Archaeal Viruses Contribute to the Novel Viral Assemblage Inhabiting Oceanic, Basalt-Hosted Deep Subsurface Crustal Fluids

NASA Astrophysics Data System (ADS)

Nigro, O. D.; Rappe, M. S.; Jungbluth, S.; Lin, H. T.; Steward, G.

2015-12-01

Fluids contained in the basalt-hosted deep subsurface of the world's oceans represent one of the most inaccessible and understudied biospheres on earth. Recent improvements in sampling infrastructure have allowed us to collect large volumes of crustal fluids (~104 L) from Circulation Obviation Retrofit Kits (CORKs) placed in boreholes located on the eastern flank of the Juan de Fuca Ridge (JdFR). We detected viruses within these fluids by TEM and epifluorescence microscopy in samples collected from 2010 to 2014. Viral abundance, determined by epifluorescence counts, indicated that concentrations of viruses in subsurface basement fluids (~105 ml-1) are lower than the overlying seawater, but are higher in abundance than microbial cells in the same samples. Analysis of TEM images revealed distinct viral morphologies (rod and spindle-shaped) that resemble the morphologies of viral families infecting archaea. There are very few, if any, direct observations of these viral morphologies in marine samples, although they have been observed in enrichment cultures and their signature genes detected in metagenomic studies from hydrothermal vents and marine sediments. Analysis of metagenomes from the JdFR crustal fluids revealed sequences with homology to archaeal viruses from the rudiviridae, bicaudaviridae and fuselloviridae. Prokaryotic communities in fluids percolating through the basaltic basement rock of the JdFR flank are distinct from those inhabiting the overlying sediments and seawater. Similarly, our data support the idea that the viral assemblage in these fluids is distinct from viral assemblages in other marine and terrestrial aquatic environments. Our data also suggest that viruses contribute to the mortality of deep subsurface prokaryotes through cell lysis, and viruses may alter the genetic potential of their hosts through the processes of lysogenic conversion and horizontal gene transfer.

ANME-2D Archaea Catalyze Methane Oxidation in Deep Subsurface Sediments Independent of Nitrate Reduction

NASA Astrophysics Data System (ADS)

Hernsdorf, A. W.; Amano, Y.; Suzuki, Y.; Ise, K.; Thomas, B. C.; Banfield, J. F.

2015-12-01

Terrestrial sediments are an important global reservoir for methane. Microorganisms in the deep subsurface play a critical role in the methane cycle, yet much remains to be learned about their diversity and metabolisms. To provide more comprehensive insight into the microbiology of the methane cycle in the deep subsurface, we conducted a genome-resolved study of samples collected from the Horonobe Underground Research Laboratory (HURL), Japan. Groundwater samples were obtained from three boreholes from a depth range of between 140 m and 250 m in two consecutive years. Groundwater was filtered and metagenomic DNA extracted and sequenced, and the sequence data assembled. Based on the sequences of phylogenetically informative genes on the assembled fragments, we detected a high degree of overlap in community composition across a vertical transect within one borehole at the two sampling times. However, there was comparatively little similarity observed among communities across boreholes. Spatial and temporal abundance patterns were used in combination with tetranucleotide signatures of assembled genome fragments to bin the data and reconstruct over 200 unique draft genomes, of which 137 are considered to be of high quality (>90% complete). The deepest samples from one borehole were highly dominated by an archaeon identified as ANME-2D; this organism was also present at lower abundance in all other samples from that borehole. Also abundant in these microbial communities were novel members of the Gammaproteobacteria, Saccharibacteria (TM7) and Tenericute phyla. Notably, a ~2 Mbp draft genome for the ANME-2D archaeon was reconstructed. As expected, the genome encodes all of the genes predicted to be involved in the reverse methanogenesis pathway. In contrast with the previously reported ANME2-D genome, the HURL ANME-2D genome lacks the capacity to reduce nitrate. However, we identified many multiheme cytochromes with closest similarity to those of the known Fe-reducing/oxidizing archaeon Ferroglobus placidus. Thus, we suggest that ANME2-D may couple methane oxidation to reduction of ferric iron minerals in the sediment and may be generally important as a link between the iron and methane cycles in deep subsurface environments. Such information has important implications for modeling the global carbon cycle.

A New Sensitive GC-MS-based Method for Analysis of Dipicolinic Acid and Quantifying Bacterial Endospores in Deep Marine Subsurface Sediment

NASA Astrophysics Data System (ADS)

Fang, J.

2015-12-01

Marine sediments cover more than two-thirds of the Earth's surface and represent a major part of the deep biosphere. Microbial cells and microbial activity appear to be widespread in these sediments. Recently, we reported the isolation of gram-positive anaerobic spore-forming piezophilic bacteria and detection of bacterial endospores in marine subsurface sediment from the Shimokita coalbed, Japan. However, the modern molecular microbiological methods (e.g., DNA-based microbial detection techniques) cannot detect bacterial endospore, because endospores are impermeable and are not stained by fluorescence DNA dyes or by ribosomal RNA staining techniques such as catalysed reporter deposition fluorescence in situ hybridization. Thus, the total microbial cell abundance in the deep biosphere may has been globally underestimated. This emphasizes the need for a new cultivation independent approach for the quantification of bacterial endospores in the deep subsurface. Dipicolinic acid (DPA, pyridine-2,6-dicarboxylic acid) is a universal and specific component of bacterial endospores, representing 5-15wt% of the dry spore, and therefore is a useful indicator and quantifier of bacterial endospores and permits to estimate total spore numbers in the subsurface biosphere. We developed a sensitive analytical method to quantify DPA content in environmental samples using gas chromatography-mass spectrometry. The method is sensitive and more convenient in use than other traditional methods. We applied this method to analyzing sediment samples from the South China Sea (obtained from IODP Exp. 349) to determine the abundance of spore-forming bacteria in the deep marine subsurface sediment. Our results suggest that gram-positive, endospore-forming bacteria may be the "unseen majority" in the deep biosphere.

Energy Requirements of Hydrogen-utilizing Microbes: A Boundary Condition for Subsurface Life

NASA Technical Reports Server (NTRS)

Hoehler, Tori M.; Alperin, Marc J.; Albert, Daniel B.; Martens, Christopher S.

2003-01-01

Microbial ecosystems based on the energy supplied by water-rock chemistry carry particular significance in the context of geo- and astrobiology. With no direct dependence on solar energy, lithotrophic microbes could conceivably penetrate a planetary crust to a depth limited only by temperature or pressure constraints (several kilometers or more). The deep lithospheric habitat is thereby potentially much greater in volume than its surface counterpart, and in addition offers a stable refuge against inhospitable surface conditions related to climatic or atmospheric evolution (e.g., Mars) or even high-energy impacts (e.g., early in Earth's history). The possibilities for a deep microbial biosphere are, however, greatly constrained by life s need to obtain energy at a certain minimum rate (the maintenance energy requirement) and of a certain minimum magnitude (the energy quantum requirement). The mere existence of these requirements implies that a significant fraction of the chemical free energy available in the subsurface environment cannot be exploited by life. Similar limits may also apply to the usefulness of light energy at very low intensities or long wavelengths. Quantification of these minimum energy requirements in terrestrial microbial ecosystems will help to establish a criterion of energetic habitability that can significantly constrain the prospects for life in Earth's subsurface, or on other bodies in the solar system. Our early work has focused on quantifying the biological energy quantum requirement for methanogenic archaea, as representatives of a plausible subsurface metabolism, in anoxic sediments (where energy availability is among the most limiting factors in microbial population growth). In both field and laboratory experiments utilizing these sediments, methanogens retain a remarkably consistent free energy intake, in the face of fluctuating environmental conditions that affect energy availability. The energy yields apparently required by methanogens in these sediment systems for sustained metabolism are about half that previously thought necessary. Lowered energy requirements would imply that a correspondingly greater proportion of the planetary subsurface could represent viable habitat for microorganisms.

Chemolithotrophy in the continental deep subsurface: Sanford Underground Research Facility (SURF), USA

PubMed Central

Osburn, Magdalena R.; LaRowe, Douglas E.; Momper, Lily M.; Amend, Jan P.

2014-01-01

The deep subsurface is an enormous repository of microbial life. However, the metabolic capabilities of these microorganisms and the degree to which they are dependent on surface processes are largely unknown. Due to the logistical difficulty of sampling and inherent heterogeneity, the microbial populations of the terrestrial subsurface are poorly characterized. In an effort to better understand the biogeochemistry of deep terrestrial habitats, we evaluate the energetic yield of chemolithotrophic metabolisms and microbial diversity in the Sanford Underground Research Facility (SURF) in the former Homestake Gold Mine, SD, USA. Geochemical data, energetic modeling, and DNA sequencing were combined with principle component analysis to describe this deep (down to 8100 ft below surface), terrestrial environment. SURF provides access into an iron-rich Paleoproterozoic metasedimentary deposit that contains deeply circulating groundwater. Geochemical analyses of subsurface fluids reveal enormous geochemical diversity ranging widely in salinity, oxidation state (ORP 330 to −328 mV), and concentrations of redox sensitive species (e.g., Fe2+ from near 0 to 6.2 mg/L and Σ S2- from 7 to 2778μg/L). As a direct result of this compositional buffet, Gibbs energy calculations reveal an abundance of energy for microorganisms from the oxidation of sulfur, iron, nitrogen, methane, and manganese. Pyrotag DNA sequencing reveals diverse communities of chemolithoautotrophs, thermophiles, aerobic and anaerobic heterotrophs, and numerous uncultivated clades. Extrapolated across the mine footprint, these data suggest a complex spatial mosaic of subsurface primary productivity that is in good agreement with predicted energy yields. Notably, we report Gibbs energy normalized both per mole of reaction and per kg fluid (energy density) and find the later to be more consistent with observed physiologies and environmental conditions. Further application of this approach will significantly expand our understanding of the deep terrestrial biosphere. PMID:25429287

Trends and Future Challenges in Sampling the Deep Terrestrial Biosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilkins, Michael J.; Daly, Rebecca; Mouser, Paula J.

2014-09-12

Research in the deep terrestrial biosphere is driven by interest in novel biodiversity and metabolisms, biogeochemical cycling, and the impact of human activities on this ecosystem. As this interest continues to grow, it is important to ensure that when subsurface investigations are proposed, materials recovered from the subsurface are sampled and preserved in an appropriate manner to limit contamination and ensure preservation of accurate microbial, geochemical, and mineralogical signatures. On February 20th, 2014, a workshop on “Trends and Future Challenges in Sampling The Deep Subsurface” was coordinated in Columbus, Ohio by The Ohio State University and West Virginia University faculty,more » and sponsored by The Ohio State University and the Sloan Foundation’s Deep Carbon Observatory. The workshop aims were to identify and develop best practices for the collection, preservation, and analysis of terrestrial deep rock samples. This document summarizes the information shared during this workshop.« less

Metabolic stratification driven by surface and subsurface interactions in a terrestrial mud volcano.

PubMed

Cheng, Ting-Wen; Chang, Yung-Hsin; Tang, Sen-Lin; Tseng, Ching-Hung; Chiang, Pei-Wen; Chang, Kai-Ti; Sun, Chih-Hsien; Chen, Yue-Gau; Kuo, Hung-Chi; Wang, Chun-Ho; Chu, Pao-Hsuan; Song, Sheng-Rong; Wang, Pei-Ling; Lin, Li-Hung

2012-12-01

Terrestrial mud volcanism represents the prominent surface geological feature, where fluids and hydrocarbons are discharged along deeply rooted structures in tectonically active regimes. Terrestrial mud volcanoes (MVs) directly emit the major gas phase, methane, into the atmosphere, making them important sources of greenhouse gases over geological time. Quantification of methane emission would require detailed insights into the capacity and efficiency of microbial metabolisms either consuming or producing methane in the subsurface, and establishment of the linkage between these methane-related metabolisms and other microbial or abiotic processes. Here we conducted geochemical, microbiological and genetic analyses of sediments, gases, and pore and surface fluids to characterize fluid processes, community assemblages, functions and activities in a methane-emitting MV of southwestern Taiwan. Multiple lines of evidence suggest that aerobic/anaerobic methane oxidation, sulfate reduction and methanogenesis are active and compartmentalized into discrete, stratified niches, resembling those in marine settings. Surface evaporation and oxidation of sulfide minerals are required to account for the enhanced levels of sulfate that fuels subsurface sulfate reduction and anaerobic methanotrophy. Methane flux generated by in situ methanogenesis appears to alter the isotopic compositions and abundances of thermogenic methane migrating from deep sources, and to exceed the capacity of microbial consumption. This metabolic stratification is sustained by chemical disequilibria induced by the mixing between upward, anoxic, methane-rich fluids and downward, oxic, sulfate-rich fluids.

Metabolic stratification driven by surface and subsurface interactions in a terrestrial mud volcano

PubMed Central

Cheng, Ting-Wen; Chang, Yung-Hsin; Tang, Sen-Lin; Tseng, Ching-Hung; Chiang, Pei-Wen; Chang, Kai-Ti; Sun, Chih-Hsien; Chen, Yue-Gau; Kuo, Hung-Chi; Wang, Chun-Ho; Chu, Pao-Hsuan; Song, Sheng-Rong; Wang, Pei-Ling; Lin, Li-Hung

2012-01-01

Terrestrial mud volcanism represents the prominent surface geological feature, where fluids and hydrocarbons are discharged along deeply rooted structures in tectonically active regimes. Terrestrial mud volcanoes (MVs) directly emit the major gas phase, methane, into the atmosphere, making them important sources of greenhouse gases over geological time. Quantification of methane emission would require detailed insights into the capacity and efficiency of microbial metabolisms either consuming or producing methane in the subsurface, and establishment of the linkage between these methane-related metabolisms and other microbial or abiotic processes. Here we conducted geochemical, microbiological and genetic analyses of sediments, gases, and pore and surface fluids to characterize fluid processes, community assemblages, functions and activities in a methane-emitting MV of southwestern Taiwan. Multiple lines of evidence suggest that aerobic/anaerobic methane oxidation, sulfate reduction and methanogenesis are active and compartmentalized into discrete, stratified niches, resembling those in marine settings. Surface evaporation and oxidation of sulfide minerals are required to account for the enhanced levels of sulfate that fuels subsurface sulfate reduction and anaerobic methanotrophy. Methane flux generated by in situ methanogenesis appears to alter the isotopic compositions and abundances of thermogenic methane migrating from deep sources, and to exceed the capacity of microbial consumption. This metabolic stratification is sustained by chemical disequilibria induced by the mixing between upward, anoxic, methane-rich fluids and downward, oxic, sulfate-rich fluids. PMID:22739492

The Search for Sustainable Subsurface Habitats on Mars, and the Sampling of Impact Ejecta

NASA Astrophysics Data System (ADS)

Ivarsson, Magnus; Lindgren, Paula

2010-07-01

On Earth, the deep subsurface biosphere of both the oceanic and the continental crust is well known for surviving harsh conditions and environments characterized by high temperatures, high pressures, extreme pHs, and the absence of sunlight. The microorganisms of the terrestrial deep biosphere have an excellent capacity for adapting to changing geochemistry, as the alteration of the crust proceeds and the conditions of their habitats slowly change. Despite an almost complete isolation from surface conditions and the surface biosphere, the deep biosphere of the crustal rocks has endured over geologic time. This indicates that the deep biosphere is a self-sufficient system, independent of the global events that occur at the surface, such as impacts, glaciations, sea level fluctuations, and climate changes. With our sustainable terrestrial subsurface biosphere in mind, the subsurface on Mars has often been suggested as the most plausible place to search for fossil Martian life, or even present Martian life. Since the Martian surface is more or less sterile, subsurface settings are the only place on Mars where life could have been sustained over geologic time. To detect a deep biosphere in the Martian basement, drilling is a requirement. However, near future Mars sample return missions are limited by the mission's payload, which excludes heavy drilling equipment and restrict the missions to only dig the topmost meter of the Martian soil. Therefore, the sampling and analysis of Martian impact ejecta has been suggested as a way of accessing the deeper Martian subsurface without using heavy drilling equipment. Impact cratering is a natural geological process capable of excavating and exposing large amounts of rock material from great depths up to the surface. Several studies of terrestrial impact deposits show the preservation of pre-impact biosignatures, such as fossilized organisms and chemical biological markers. Therefore, if the Martian subsurface contains a record of life, it is reasonable to assume that biosignatures derived from the Martian subsurface could also be preserved in the Martian impact ejecta.

Microbial community composition along a 50 000-year lacustrine sediment sequence

PubMed Central

Ariztegui, Daniel; Horn, Fabian; Kallmeyer, Jens; Orsi, William D

2018-01-01

Abstract For decades, microbial community composition in subseafloor sediments has been the focus of extensive studies. In deep lacustrine sediments, however, the taxonomic composition of microbial communities remains undercharacterized. Greater knowledge on microbial diversity in lacustrine sediments would improve our understanding of how environmental factors, and resulting selective pressures, shape subsurface biospheres in marine and freshwater sediments. Using high-throughput sequencing of 16S rRNA genes across high-resolution climate intervals covering the last 50 000 years in Laguna Potrok Aike, Argentina, we identified changes in microbial populations in response to both past environmental conditions and geochemical changes of the sediment during burial. Microbial communities in Holocene sediments were most diverse, reflecting a layering of taxa linked to electron acceptors availability. In deeper intervals, the data show that salinity, organic matter and the depositional conditions over the Last Glacial-interglacial cycle were all selective pressures in the deep lacustrine assemblage resulting in a genetically distinct biosphere from the surface dominated primarily by Bathyarchaeota and Atribacteria groups. However, similar to marine sediments, some dominant taxa in the shallow subsurface persisted into the subsurface as minor fraction of the community. The subsequent establishment of a deep subsurface community likely results from a combination of paleoenvironmental factors that have shaped the pool of available substrates, together with substrate depletion and/or reworking of organic matter with depth. PMID:29471361

Deep subsurface microbial processes

USGS Publications Warehouse

Lovley, D.R.; Chapelle, F.H.

1995-01-01

Information on the microbiology of the deep subsurface is necessary in order to understand the factors controlling the rate and extent of the microbially catalyzed redox reactions that influence the geophysical properties of these environments. Furthermore, there is an increasing threat that deep aquifers, an important drinking water resource, may be contaminated by man's activities, and there is a need to predict the extent to which microbial activity may remediate such contamination. Metabolically active microorganisms can be recovered from a diversity of deep subsurface environments. The available evidence suggests that these microorganisms are responsible for catalyzing the oxidation of organic matter coupled to a variety of electron acceptors just as microorganisms do in surface sediments, but at much slower rates. The technical difficulties in aseptically sampling deep subsurface sediments and the fact that microbial processes in laboratory incubations of deep subsurface material often do not mimic in situ processes frequently necessitate that microbial activity in the deep subsurface be inferred through nonmicrobiological analyses of ground water. These approaches include measurements of dissolved H2, which can predict the predominant microbially catalyzed redox reactions in aquifers, as well as geochemical and groundwater flow modeling, which can be used to estimate the rates of microbial processes. Microorganisms recovered from the deep subsurface have the potential to affect the fate of toxic organics and inorganic contaminants in groundwater. Microbial activity also greatly influences 1 the chemistry of many pristine groundwaters and contributes to such phenomena as porosity development in carbonate aquifers, accumulation of undesirably high concentrations of dissolved iron, and production of methane and hydrogen sulfide. Although the last decade has seen a dramatic increase in interest in deep subsurface microbiology, in comparison with the study of other habitats, the study of deep subsurface microbiology is still in its infancy.

Anaerobic decomposition of humic substances by Clostridium from the deep subsurface

PubMed Central

Ueno, Akio; Shimizu, Satoru; Tamamura, Shuji; Okuyama, Hidetoshi; Naganuma, Takeshi; Kaneko, Katsuhiko

2016-01-01

Decomposition of humic substances (HSs) is a slow and cryptic but non-negligible component of carbon cycling in sediments. Aerobic decomposition of HSs by microorganisms in the surface environment has been well documented; however, the mechanism of anaerobic microbial decomposition of HSs is not completely understood. Moreover, no microorganisms capable of anaerobic decomposition of HSs have been isolated. Here, we report the anaerobic decomposition of humic acids (HAs) by the anaerobic bacterium Clostridium sp. HSAI-1 isolated from the deep terrestrial subsurface. The use of 14C-labelled polycatechol as an HA analogue demonstrated that the bacterium decomposed this substance up to 7.4% over 14 days. The decomposition of commercial and natural HAs by the bacterium yielded lower molecular mass fractions, as determined using high-performance size-exclusion chromatography. Fourier transform infrared spectroscopy revealed the removal of carboxyl groups and polysaccharide-related substances, as well as the generation of aliphatic components, amide and aromatic groups. Therefore, our results suggest that Clostridium sp. HSAI-1 anaerobically decomposes and transforms HSs. This study improves our understanding of the anaerobic decomposition of HSs in the hidden carbon cycling in the Earth’s subsurface. PMID:26743007

Terrestrial source to deep-sea sink sediment budgets at high and low sea levels: Insights from tectonically active Southern California

USGS Publications Warehouse

Covault, J.A.; Romans, B.W.; Graham, S.A.; Fildani, A.; Hilley, G.E.

2011-01-01

Sediment routing from terrestrial source areas to the deep sea influences landscapes and seascapes and supply and filling of sedimentary basins. However, a comprehensive assessment of land-to-deep-sea sediment budgets over millennia with significant climate change is lacking. We provide source to sink sediment budgets using cosmogenic radionuclide-derived terrestrial denudation rates and submarine-fan deposition rates through sea-level fluctuations since oxygen isotope stage 3 (younger than 40 ka) in tectonically active, spatially restricted sediment-routing systems of Southern California. We show that source-area denudation and deep-sea deposition are balanced during a period of generally falling and low sea level (40-13 ka), but that deep-sea deposition exceeds terrestrial denudation during the subsequent period of rising and high sea level (younger than 13 ka). This additional supply of sediment is likely owed to enhanced dispersal of sediment across the shelf caused by seacliff erosion during postglacial shoreline transgression and initiation of submarine mass wasting. During periods of both low and high sea level, land and deep-sea sediment fluxes do not show orders of magnitude imbalances that might be expected in the wake of major sea-level changes. Thus, sediment-routing processes in a globally significant class of small, tectonically active systems might be fundamentally different from those of larger systems that drain entire orogens, in which sediment storage in coastal plains and wide continental shelves can exceed millions of years. Furthermore, in such small systems, depositional changes offshore can reflect onshore changes when viewed over time scales of several thousand years to more than 10 k.y. ?? 2011 Geological Society of America.

Geomicrobiology and Metagenomics of Terrestrial Deep Subsurface Microbiomes.

PubMed

Itävaara, M; Salavirta, H; Marjamaa, K; Ruskeeniemi, T

2016-01-01

Fractures in the deep subsurface of Earth's crust are inhabited by diverse microbial communities that participate in biogeochemical cycles of the Earth. Life on Earth, which arose c. 3.5-4.0 billion years ago, reaches down at least 5 km in the crust. Deep mines, caves, and boreholes have provided scientists with opportunities to sample deep subsurface microbiomes and to obtain information on the species diversity and functions. A wide variety of bacteria, archaea, eukaryotes, and viruses are now known to reside in the crust, but their functions are still largely unknown. The crust at different depths has varying geological composition and hosts endemic microbiomes accordingly. The diversity is driven by geological formations and gases evolving from deeper depths. Cooperation among different species is still mostly unexplored, but viruses are known to restrict density of bacterial and archaeal populations. Due to the complex growth requirements of the deep subsurface microbiomes, the new knowledge about their diversity and functions is mostly obtained by molecular methods, eg, meta'omics'. Geomicrobiology is a multidisciplinary research area combining disciplines from geology, mineralogy, geochemistry, and microbiology. Geomicrobiology is concerned with the interaction of microorganisms and geological processes. At the surface of mineralogical or rock surfaces, geomicrobial processes occur mainly under aerobic conditions. In the deep subsurface, however, the environmental conditions are reducing and anaerobic. The present chapter describes the world of microbiomes in deep terrestrial geological environments as well as metagenomic and metatranscriptomic methods suitable for studies of these enigmatic communities. Copyright © 2016 Elsevier Inc. All rights reserved.

Ecology, physiology, and phylogeny of deep subsurface Sphingomonas sp.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fredrickson, Jim K.; Balkwill, David L.; Romine, Margaret F.

Several new species of the genus Sphingomonas including S. aromaticivorans, S. stygia, and S. subterranea that have the capacity for degrading a broad range of aromatic compounds including toluene, naphthalene, xylenes, p-cresol, fluorene, biphenyl, and dibenzothiophene, were isolated from deeply-buried (>200 m) sediments of the US Atlantic coastal plain (ACP). In S. aromaticivorans F199, many of the genes involved in the catabolism of these aromatic compounds are encoded on a 184-kb conjugative plasmid; some of the genes involved in aromatic catabolism are plasmid-encoded in the other strains as well. Members of the genus Sphingomonas were common among aerobic heterotrophic bacteriamore » cultured from ACP sediments and have been detected in deep subsurface environments elsewhere. The major source of organic carbon for heterotrophic metabolism in ACP deep aquifers is lignite that originated from plant material buried with the sediments. We speculate that the ability of the subsurface Sphingomonas strains to degrade a wide array of aromatic compounds represents an adaptation for utilization of sedimentary lignite. These and related subsurface Sphingomonas spp may play an important role in the transformation of sedimentary organic carbon in the aerobic and microaerobic regions of the deep aquifers of the ACP.« less

Ecology, physiology, and phylogeny of deep subsurface Sphingomonas sp.

PubMed

Fredrickson, J K; Balkwill, D L; Romine, M F; Shi, T

1999-10-01

Several new species of the genus Sphingomonas including S. aromaticivorans, S. stygia, and S. subterranea that have the capacity for degrading a broad range of aromatic compounds including toluene, naphthalene, xylenes, p-cresol, fluorene, biphenyl, and dibenzothiophene, were isolated from deeply-buried (>200 m) sediments of the US Atlantic coastal plain (ACP). In S. aromaticivorans F199, many of the genes involved in the catabolism of these aromatic compounds are encoded on a 184-kb conjugative plasmid; some of the genes involved in aromatic catabolism are plasmid-encoded in the other strains as well. Members of the genus Sphingomonas were common among aerobic heterotrophic bacteria cultured from ACP sediments and have been detected in deep subsurface environments elsewhere. The major source of organic carbon for heterotrophic metabolism in ACP deep aquifers is lignite that originated from plant material buried with the sediments. We speculate that the ability of the subsurface Sphingomonas strains to degrade a wide array of aromatic compounds represents an adaptation for utilization of sedimentary lignite. These and related subsurface Sphingomonas spp may play an important role in the transformation of sedimentary organic carbon in the aerobic and microaerobic regions of the deep aquifers of the ACP.

Fungi in deep-sea sediments of the Central Indian Basin

NASA Astrophysics Data System (ADS)

Damare, Samir; Raghukumar, Chandralata; Raghukumar, S.

2006-01-01

Although a great amount of information is available on bacteria inhabiting deep-sea sediments, the occurrence of fungi in this environment has been poorly studied and documented. We report here the occurrence of fungi in deep-sea sediments from ˜5000 m depth in the Central Indian Basin (9-16°S and 73-76°E). A total of 181 cultures of fungi, most of which belong to terrestrial sporulating species, were isolated by a variety of isolation techniques. Species of Aspergillus and non-sporulating fungi were the most common. Several yeasts were also isolated. Maximum species diversity was observed in 0-2 cm sections of the sediment cores. Direct staining of the sediments with Calcofluor, a fluorescent optical brightener, revealed the presence of fungal hyphae in the sediments. Immunofluorescence using polyclonal antibodies raised against a deep-sea isolate of Aspergillus terreus (# A 4634) confirmed its presence in the form of hyphae in the sub-section from which it was isolated. A total of 25 representative species of fungi produced substantial biomass at 200 bar pressure at 30° as well as at 5 °C. Many fungi showed abnormal morphology at 200 bar/5 °C. A comparison of terrestrial isolates with several deep-sea isolates indicated that the former could grow at 200 bar pressure when growth was initiated with mycelial inocula. However, spores of a deep-sea isolate A. terreus (# A 4634), but not the terrestrial ones, showed germination at 200 bar pressure and 30 °C. Our results suggest that terrestrial species of fungi transported to the deep sea are initially stressed but may gradually adapt themselves for growth under these conditions.

Energy Gradients Structure Microbial Communities Across Sediment Horizons in Deep Marine Sediments of the South China Sea

PubMed Central

Graw, Michael F.; D'Angelo, Grace; Borchers, Matthew; Thurber, Andrew R.; Johnson, Joel E.; Zhang, Chuanlun; Liu, Haodong; Colwell, Frederick S.

2018-01-01

The deep marine subsurface is a heterogeneous environment in which the assembly of microbial communities is thought to be controlled by a combination of organic matter deposition, electron acceptor availability, and sedimentology. However, the relative importance of these factors in structuring microbial communities in marine sediments remains unclear. The South China Sea (SCS) experiences significant variability in sedimentation across the basin and features discrete changes in sedimentology as a result of episodic deposition of turbidites and volcanic ashes within lithogenic clays and siliceous or calcareous ooze deposits throughout the basin's history. Deep subsurface microbial communities were recently sampled by the International Ocean Discovery Program (IODP) at three locations in the SCS with sedimentation rates of 5, 12, and 20 cm per thousand years. Here, we used Illumina sequencing of the 16S ribosomal RNA gene to characterize deep subsurface microbial communities from distinct sediment types at these sites. Communities across all sites were dominated by several poorly characterized taxa implicated in organic matter degradation, including Atribacteria, Dehalococcoidia, and Aerophobetes. Sulfate-reducing bacteria comprised only 4% of the community across sulfate-bearing sediments from multiple cores and did not change in abundance in sediments from the methanogenic zone at the site with the lowest sedimentation rate. Microbial communities were significantly structured by sediment age and the availability of sulfate as an electron acceptor in pore waters. However, microbial communities demonstrated no partitioning based on the sediment type they inhabited. These results indicate that microbial communities in the SCS are structured by the availability of electron donors and acceptors rather than sedimentological characteristics. PMID:29696012

Microbial abundance in the deep subsurface of the Chesapeake Bay impact crater: Relationship to lithology and impact processes

USGS Publications Warehouse

Cockell, Charles S.; Gronstal, Aaron L.; Voytek, Mary A.; Kirshtein, Julie D.; Finster, Kai; Sanford, Ward E.; Glamoclija, Mihaela; Gohn, Gregroy S.; Powars, David S.; Horton, J. Wright

2009-01-01

Asteroid and comet impact events are known to cause profound disruption to surface ecosystems. The aseptic collection of samples throughout a 1.76-km-deep set of cores recovered from the deep subsurface of the Chesapeake Bay impact structure has allowed the study of the subsurface biosphere in a region disrupted by an impactor. Microbiological enumerations suggest the presence of three major microbiological zones. The upper zone (127–867 m) is characterized by a logarithmic decline in microbial abundance from the surface through the postimpact section of Miocene to Upper Eocene marine sediments and across the transition into the upper layers of the impact tsunami resurge sediments and sediment megablocks. In the middle zone (867–1397 m) microbial abundances are below detection. This zone is predominantly quartz sand, primarily composed of boulders and blocks, and it may have been mostly sterilized by the thermal pulse delivered during impact. No samples were collected from the large granite block (1096–1371 m). The lowest zone (below 1397 m) of increasing microbial abundance coincides with a region of heavily impact-fractured, hydraulically conductive suevite and fractured schist. These zones correspond to lithologies influenced by impact processes. Our results yield insights into the influence of impacts on the deep subsurface biosphere.

Culturable prokaryotic diversity of deep, gas hydrate sediments: first use of a continuous high-pressure, anaerobic, enrichment and isolation system for subseafloor sediments (DeepIsoBUG)

PubMed Central

Parkes, R John; Sellek, Gerard; Webster, Gordon; Martin, Derek; Anders, Erik; Weightman, Andrew J; Sass, Henrik

2009-01-01

Deep subseafloor sediments may contain depressurization-sensitive, anaerobic, piezophilic prokaryotes. To test this we developed the DeepIsoBUG system, which when coupled with the HYACINTH pressure-retaining drilling and core storage system and the PRESS core cutting and processing system, enables deep sediments to be handled without depressurization (up to 25 MPa) and anaerobic prokaryotic enrichments and isolation to be conducted up to 100 MPa. Here, we describe the system and its first use with subsurface gas hydrate sediments from the Indian Continental Shelf, Cascadia Margin and Gulf of Mexico. Generally, highest cell concentrations in enrichments occurred close to in situ pressures (14 MPa) in a variety of media, although growth continued up to at least 80 MPa. Predominant sequences in enrichments were Carnobacterium, Clostridium, Marinilactibacillus and Pseudomonas, plus Acetobacterium and Bacteroidetes in Indian samples, largely independent of media and pressures. Related 16S rRNA gene sequences for all of these Bacteria have been detected in deep, subsurface environments, although isolated strains were piezotolerant, being able to grow at atmospheric pressure. Only the Clostridium and Acetobacterium were obligate anaerobes. No Archaea were enriched. It may be that these sediment samples were not deep enough (total depth 1126–1527 m) to obtain obligate piezophiles. PMID:19694787

Characterisation of DOC and its relation to the deep terrestrial biosphere

NASA Astrophysics Data System (ADS)

Vieth, Andrea; Vetter, Alexandra; Sachse, Anke; Horsfield, Brian

2010-05-01

The deep subsurface is populated by a large number of microorganisms playing a pivotal role in the carbon cycling. The question arises as to the origin of the potential carbon sources that support deep microbial communities and their possible interactions within the deep subsurface. As the carbon sources need to be dissolved in formation fluids to become available to microorganisms, the dissolved organic carbon (DOC) needs further characterisation as regards concentration, structural as well as molecular composition and origin. The Malm carbonates in the Molasse basin of southern Germany are of large economic potential as they are targets for both hydrocarbon and geothermal exploration (ANDREWS et al., 1987). Five locations that differ in their depth of the Malm aquifer between 220 m and 3445 m below surface have been selected for fluid sampling. The concentration and the isotopic composition of the DOC have been determined. To get a better insight into the structural composition of the DOC, we also applied size exclusion chromatography and quantified the amount of low molecular weight organic acids (LMWOA) by ion chromatography. With increasing depth of the aquifer the formation fluids show increasing salinity as chloride concentrations increase from 2 to 300 mg/l and also the composition of the DOC changes. Water samples from greater depth (>3000 m) showed that the DOC mainly consists of LMWOA (max. 83 %) and low percentages of neutral compounds (alcohols, aldehyde, ketones, amino acids) as well as "building blocks". Building blocks have been described to be the oxidation intermediates from humic substances to LMWOA. With decreasing depth of the aquifer, the DOC of the fluid becomes increasingly dominated by neutral compounds and the percentage of building blocks increases to around 27%. The fluid sample from 220 m depth still contains a small amount of humic substances. The DOC of formation fluids in some terrestrial sediments may originate from organic-rich layers like coals and source rocks which may provide carbon sources for the deep biosphere by leaching water soluble organic compounds. We investigated the potential of a series of Eocene-Pleistocene coals, mudstones and sandstones from New Zealand with different maturities (Ro between 0.29 and 0.39) and total organic carbon content (TOC) regarding their potential to release such compounds. The water extraction of these New Zealand coals using Soxhlet apparatus resulted in yields of LMWOA that may feed the local deep terrestrial biosphere over geological periods of time (VIETH et al., 2008). However, the DOC of the water extracts mainly consisted of humic substances. To investigate the effect of thermal maturity of the organic matter as well as the effect of the organic matter type on the extraction yields, we examined additional coal samples (Ro between 0.29 and 0.80) and source rock samples from low to medium maturity (Ro between 0.3 to 1.1). Within our presentation we would like to show the compositional diversity and variability of dissolved organic compounds in natural formation fluids as well as in water extracts from a series of very different lithologies and discuss their effects on the carbon cycling in the deep terrestrial subsurface. References: Andrews, J. N., Youngman, M. J., Goldbrunner, J. E., and Darling, W. G., 1987. The geochemistry of formation waters in the Molasse Basin of Upper Austria. Environmental Geology 10, 43-57. Vieth, A., Mangelsdorf, K., Sykes, R., and Horsfield, B., 2008. Water extraction of coals - potential to estimate low molecular weight organic acids as carbon feedstock for the deep terrestrial biosphere? Organic Geochemistry 39, 985-991.

Analysis of a PAH-degrading bacterial population in subsurface sediments on the Mid-Atlantic Ridge

NASA Astrophysics Data System (ADS)

Shao, Zongze; Cui, Zhisong; Dong, Chunming; Lai, Qiliang; Chen, Liang

2010-05-01

Little is known about the types and concentrations of polycyclic aromatic hydrocarbons (PAHs) existing in the deep-sea subsurface environment, which is believed to be cold, oligothrophic and of high static pressure. PAHs in the upper layers of the water column are unavoidably subjected to degradation while they are deposited to the sea floor and become embedded in the deep-sea sediment. In this report, a high concentration of PAHs was discovered in the sediment 2.7 m beneath the bottom surface at a water depth of 3962 m on the Mid-Atlantic Ridge (MAR). The total concentration of PAHs was 445 ng (g dry wt sediment) -1. Among the seven detected PAHs, the concentrations of phenanthrene (222 ng g -1) and fluorene (79 ng g -1) were relatively high. In addition, PAH-degrading bacteria were found within the sediments. As in a previously detected site on the MAR, in the PAH-enriched region of this site, a bacterium of the genus Cycloclasticus was found to be the predominant isolate detected by PCR-DGGE analysis. In addition, bacteria of the Halomonas, Marinobacter, Alcanivorax, Thalassospira and Maricaulis genera, were also included in the PAH-degrading community. In summary, a high concentration of PAHs was detected in the subsurface of the deep-sea sediment, and once again, the Cycloclasticus bacterium was confirmed to be a ubiquitous marine PAH degrader even in the subsurface marine environment. Considering the abundance of PAHs therein, biodegradation is thus thought to be inactive, probably because of the low temperature, limited oxygen and/or limited nutrients.

Sulfur and iron cycling in deep-subsurface, coal bed-containing sediments off Shimokita (Japan)

NASA Astrophysics Data System (ADS)

Riedinger, N.; Smirnoff, M. N.; Gilhooly, W.; Phillips, S. C.; Lyons, T. W.; 337 Scientific Party, I.

2013-12-01

The main goal of IODP Expedition 337 was the identification and characterization of the deep coal bed biosphere and hydrocarbon system off the Shimokita Peninsula (Japan) in the northwestern Pacific using the D/V Chikyu. To accomplish this scientific objective, it was also necessary to investigate the inorganic biogeochemistry in order to identify possible electron acceptors and bio-essential nutrients. These biogeochemical parameters greatly influence both, the composition and abundance of microbial communities as well as the organic carbon cycle. In turn, the microbially mediated carbon cycle influences the diagenetic reactions in the subsurface, thus, altering geochemical and physical characteristics of the material. Here we present results from metal and sulfur geochemical analyses from the deep-subsurface sediments (about 1250 to 2466 mbsf) at Site C0020 off Shimokita. The measured concentrations of acid volatile sulfur (AVS) as well as chromium reducible sulfur (CRS) reflect the alteration of iron oxides to iron sulfides and indicate that the main sulfur-bearing phase in the investigated sediments is pyrite. Concentrations of intermediate sulfur species are minor and occur mainly in the coal-bearing interval. Our data show that the uppermost sediments contain higher amounts of pyrite (up to 1.2 wt.%) with an average of 0.5 wt.% compared to the deeper deposits (below about 1800 mbsf), which show an average of 0.16 wt.%. In contrast, iron oxide concentrations are highest in the deeper sediment sections (up to 0.4%), where pyrite concentrations are low. The alteration of iron oxides to sulfides in theses lower section was probably governed by the amount of available sulfide in the pore water. The occurrence of (bio-)reactive iron phases in these deeply buried sediments has implications for the deep biosphere as those minerals have the potential to serve as electron acceptors during burial, including reactions involving deep sourced electron donors, such as hydrogen and methane - related to the coal bed as the potential source. Thus, the deep subsurface coal beds off Shimokita provide an ideal environment to investigate microbial and metal interactions under extreme conditions.

Origin and distribution of the organic matter in the distal lobe of the Congo deep-sea fan - A Rock-Eval survey

NASA Astrophysics Data System (ADS)

Baudin, François; Stetten, Elsa; Schnyder, Johann; Charlier, Karine; Martinez, Philippe; Dennielou, Bernard; Droz, Laurence

2017-08-01

The Congo River, the second largest river in the world, is a major source of organic matter for the deep Atlantic Ocean because of the connection of its estuary to the deep offshore area by a submarine canyon which feeds a vast deep-sea fan. The lobe zone of this deep-sea fan is the final receptacle of the sedimentary inputs presently channelled by the canyon and covers an area of 2500 km². The quantity and the source of organic matter preserved in recent turbiditic sediments from the distal lobe of the Congo deep-sea fan were assessed using Rock-Eval pyrolysis analyses. Six sites, located at approximately 5000 m water-depth, were investigated. The mud-rich sediments of the distal lobe contain high amounts of organic matter ( 3.5 to 4% Corg), the origin of which is a mixture of terrestrial higher-plant debris, soil organic matter and deeply oxidized phytoplanktonic material. Although the respective contribution of terrestrial and marine sources of organic matter cannot be precisely quantified using Rock-Eval analyses, the terrestrial fraction is dominant according to similar hydrogen and oxygen indices of both suspended and bedload sediments from the Congo River and that deposited in the lobe complex. The Rock-Eval signature supports the 70% to 80% of the terrestrial fraction previously estimated using C/N and δ13Corg data. In the background sediment, the organic matter distribution is homogeneous at different scales, from a single turbiditic event to the entire lobe, and changes in accumulation rates only have a limited effect on the quantity and quality of the preserved organic matter. Peculiar areas with chemosynthetic bivalves and/or bacterial mats, explored using ROV Victor 6000, show a Rock-Eval signature similar to background sediment. This high organic carbon content associated to high sedimentation rates (> 2 to 20 mm.yr-1) in the Congo distal lobe complex implies a high burial rate for organic carbon. Consequently, the Congo deep-sea fan represents an enormous sink of terrestrial organic matter when compared to other turbiditic systems over the world.

Homoacetogenesis in Deep-Sea Chloroflexi, as Inferred by Single-Cell Genomics, Provides a Link to Reductive Dehalogenation in Terrestrial Dehalococcoidetes

PubMed Central

Sewell, Holly L.; Kaster, Anne-Kristin

2017-01-01

ABSTRACT The deep marine subsurface is one of the largest unexplored biospheres on Earth and is widely inhabited by members of the phylum Chloroflexi. In this report, we investigated genomes of single cells obtained from deep-sea sediments of the Peruvian Margin, which are enriched in such Chloroflexi. 16S rRNA gene sequence analysis placed two of these single-cell-derived genomes (DscP3 and Dsc4) in a clade of subphylum I Chloroflexi which were previously recovered from deep-sea sediment in the Okinawa Trough and a third (DscP2-2) as a member of the previously reported DscP2 population from Peruvian Margin site 1230. The presence of genes encoding enzymes of a complete Wood-Ljungdahl pathway, glycolysis/gluconeogenesis, a Rhodobacter nitrogen fixation (Rnf) complex, glyosyltransferases, and formate dehydrogenases in the single-cell genomes of DscP3 and Dsc4 and the presence of an NADH-dependent reduced ferredoxin:NADP oxidoreductase (Nfn) and Rnf in the genome of DscP2-2 imply a homoacetogenic lifestyle of these abundant marine Chloroflexi. We also report here the first complete pathway for anaerobic benzoate oxidation to acetyl coenzyme A (CoA) in the phylum Chloroflexi (DscP3 and Dsc4), including a class I benzoyl-CoA reductase. Of remarkable evolutionary significance, we discovered a gene encoding a formate dehydrogenase (FdnI) with reciprocal closest identity to the formate dehydrogenase-like protein (complex iron-sulfur molybdoenzyme [CISM], DET0187) of terrestrial Dehalococcoides/Dehalogenimonas spp. This formate dehydrogenase-like protein has been shown to lack formate dehydrogenase activity in Dehalococcoides/Dehalogenimonas spp. and is instead hypothesized to couple HupL hydrogenase to a reductive dehalogenase in the catabolic reductive dehalogenation pathway. This finding of a close functional homologue provides an important missing link for understanding the origin and the metabolic core of terrestrial Dehalococcoides/Dehalogenimonas spp. and of reductive dehalogenation, as well as the biology of abundant deep-sea Chloroflexi. PMID:29259088

Microbial production and oxidation of methane in deep subsurface

NASA Astrophysics Data System (ADS)

Kotelnikova, Svetlana

2002-10-01

The goal of this review is to summarize present studies on microbial production and oxidation of methane in the deep subterranean environments. Methane is a long-living gas causing the "greenhouse" effect in the planet's atmosphere. Earlier, the deep "organic carbon poor" subsurface was not considered as a source of "biogenic" methane. Evidence of active methanogenesis and presence of viable methanogens including autotrophic organisms were obtained for some subsurface environments including water-flooded oil-fields, deep sandy aquifers, deep sea hydrothermal vents, the deep sediments and granitic groundwater at depths of 10 to 2000 m below sea level. As a rule, the deep subterranean microbial populations dwell at more or less oligotrophic conditions. Molecular hydrogen has been found in a variety of subsurface environments, where its concentrations were significantly higher than in the tested surface aquatic environments. Chemolithoautotrophic microorganisms from deep aquifers that could grow on hydrogen and carbon dioxide can act as primary producers of organic carbon, initiating heterotrophic food chains in the deep subterranean environments independent of photosynthesis. "Biogenic" methane has been found all over the world. On the basis of documented occurrences, gases in reservoirs and older sediments are similar and have the isotopic character of methane derived from CO 2 reduction. Groundwater representing the methanogenic end member are characterized by a relative depletion of dissolved organic carbon (DOC) in combination with an enrichment in 13C in inorganic carbon, which is consistent with the preferential reduction of 12CO 2 by autotrophic methanogens or acetogens. The isotopic composition of methane formed via CO 2 reduction is controlled by the δ13C of the original CO 2 substrate. Literature data shows that CH 4 as heavy as -40‰ or -50‰ can be produced by the microbial reduction of isotopically heavy CO 2. Produced methane may be oxidized microbially to carbon dioxide. Microbial methane oxidation is a biogeochemical process that limits the release of methane, a greenhouse gas from anaerobic environments. Anaerobic methane oxidation plays an important role in marine sediments. Similar processes may take place in deep subsurface and thus fuel the deep microbial community. Organisms or consortia responsible for anaerobic methane oxidation have not yet been cultured, although diverse aerobic methanotrophs have been isolated from a variety of underground niches. The presence of aerobic methanotrophs in the anoxic subsurface remains to be explained. The presence of methane in the deep subsurface have been shown all over the world. The flux of gases between the deep subsurface and the atmosphere is driven by the concentration gradient from depth to the atmosphere. However, methane is consumed by methanotrophs on the way of its evolution in oxidized environments and is transformed to organic form, available for further microbial processing. When the impact of subsurface environments to global warming is estimated, it is necessary to take into account the activity of methane-producing Archaea and methane-oxidizing biofilters in groundwater. Microbial production and oxidation of methane is involved in the carbon cycle in the deep subsurface environments.

Exploring Microbial Life in Oxic Sediments Underlying Oligotrophic Ocean Gyres

NASA Astrophysics Data System (ADS)

Ziebis, W.; Orcutt, B.; Wankel, S. D.; D'Hondt, S.; Szubin, R.; Kim, J. N.; Zengler, K.

2015-12-01

Oxygen, carbon and nutrient availability are defining parameters for microbial life. In contrast to organic-rich sediments of the continental margins, where high respiration rates lead to a depletion of O2 within a thin layer at the sediment surface, it was discovered that O2 penetrates several tens of meters into organic-poor sediments underlying oligotrophic ocean gyres. In addition, nitrate, another important oxidant, which usually disappears rapidly with depth in anoxic sediments, tends to accumulate above seawater concentrations in the oxic subsurface, reflecting the importance of nitrogen cycling processes, including both nitrification and denitrification. Two IODP drilling expeditions were vital for exploring the nature of the deep subsurface beneath oligotrophic ocean gyres, expedition 329 to the South Pacific Gyre (SPG) and expedition 336 to North Pond, located on the western flank of the Mid-Atlantic ridge beneath the North Atlantic Gyre. Within the ultra-oligotrophic SPG O2 penetrates the entire sediment column from the sediment-water interface to the underlying basement to depths of > 75 m. At North Pond, a topographic depression filled with sediment and surrounded by steep basaltic outcrops, O2 penetrates deeply into the sediment (~ 30 m) until it eventually becomes depleted. O2 also diffuses upward into the sediment from seawater circulating within the young crust underlying the sediment, resulting in a deep oxic layer several meters above the basalt. Despite low organic carbon contents microbial cells persist throughout the entire sediment column within the SPG (> 75 m) and at North Pond, albeit at low abundances. We explored the nature of the subsurface microbial communities by extracting intact cells from large volumes of sediment obtained from drill cores of the two expeditions. By using CARD-FiSH, amplicon (16s rRNA) and metagenome sequencing we shed light on the phylogenetic and functional diversity of the elusive communities residing in the deep oxic sediments of these two different areas. Given the global extent of this oxic subsurface studies of the diversity and metabolic potential of its biome, together with the analyses of porewater geochemical and isotopic composition, are beginning to reveal its role in global biogeochemical cycles.

Long-Duration Orbit Exposure Experiment with Sub-Surface Microorganism from a Mars Terrestrial Analog

NASA Astrophysics Data System (ADS)

Davila, A. F.; Lim, D.; Fairen, A. G.; Uceda, E. R.; Zavaleta, J.; McKay, C.

2007-07-01

Orbit Exposure Experiments (OEE) allow us to test the possibility of life transfer between planets and moons. Deep sub-surface microorganisms may be the best candidates to survive long-term exposure to space conditions. A long duration OEE is proposed to test our hypothesis.

[Search for life in deep biospheres].

PubMed

Naganuma, Takeshi

2003-12-01

The life in deep biospheres bridges conventional biology and future exobiology. This review focuses the microbiological studies from the selected deep biospheres, i.e., deep-sea hydrothermal vents, sub-hydrothermal vents, terrestrial subsurface and a sub-glacier lake. The dark biospheres facilitate the emergence of organisms and communities dependent on chemolithoautotrophy, which are overwhelmed by photoautotrophy (photosynthesis) in the surface biospheres. The life at deep-sea hydrothermal vents owes much to chemolithoautotrophy based on the oxidation of sulfide emitted from the vents. It is likely that similarly active bodies such as the Jovian satellite Europa may have hydrothermal vents and associated biological communities. Anoxic or anaerobic condition is characteristic of deep subsurface biospheres. Subsurface microorganisms exploit available oxidants, or terminal electron acceptors (TEA), for anaerobic respiration. Sulfate, nitrate, iron (III) and CO2 are the representative TEAs in the deep subsurface. Below the 3000-4000 m-thick glacier on Antarctica, there have been >70 lakes with liquid water located. One of such sub-glacial lakes, Lake Vostok, is about to be drill-penetrated for microbiological studies. These deep biosphere "platforms" provide new knowledge about the diversity and potential of the Earth's life. The expertise obtained from the deep biosphere expeditions will facilitate the capability of exobiologial exploration.

The role of water exchange between a stream channel and its hyporheic zone in nitrogen cycling at the terrestrial-aquatic interface

USGS Publications Warehouse

Triska, F.J.; Duff, J.H.; Avanzino, R.J.

1993-01-01

The subsurface riparian zone was examined as an ecotone with two interfaces. Inland is a terrestrial boundary, where transport of water and dissolved solutes is toward the channel and controlled by watershed hydrology. Streamside is an aquatic boundary, where exchange of surface water and dissolved solutes is bi-directional and flux is strongly influenced by channel hydraulics. Streamside, bi-directional exchange of water was qualitatively defined using biologically conservative tracers in a third order stream. In several experiments, penetration of surface water extended 18 m inland. Travel time of water from the channel to bankside sediments was highly variable. Subsurface chemical gradients were indirectly related to the travel time. Sites with long travel times tended to be low in nitrate and DO (dissolved oxygen) but high in ammonium and DOC (dissolved organic carbon). Sites with short travel times tended to be high in nitrate and DO but low in ammonium and DOC. Ammonium concentration of interstitial water also was influenced by sorption-desorption processes that involved clay minerals in hyporheic sediments. Denitrification potential in subsurface sediments increased with distance from the channel, and was limited by nitrate at inland sites and by DO in the channel sediments. Conversely, nitrification potential decreased with distance from the channel, and was limited by DO at inland sites and by ammonium at channel locations. Advection of water and dissolved oxygen away from the channel resulted in an oxidized subsurface habitat equivalent to that previously defined as the hyporheic zone. The hyporheic zone is viewed as stream habitat because of its high proportion of surface water and the occurrence of channel organisms. Beyond the channel's hydrologic exchange zone, interstitial water is often chemically reduced. Interstitial water that has not previously entered the channel, groundwater, is viewed as a terrestrial component of the riparian ecotone. Thus, surface water habitats may extend under riparian vegetation, and terrestrial groundwater habitats may be found beneath the stream channel. ?? 1993 Kluwer Academic Publishers.

Nematoda from the terrestrial deep subsurface of South Africa.

PubMed

Borgonie, G; García-Moyano, A; Litthauer, D; Bert, W; Bester, A; van Heerden, E; Möller, C; Erasmus, M; Onstott, T C

2011-06-02

Since its discovery over two decades ago, the deep subsurface biosphere has been considered to be the realm of single-cell organisms, extending over three kilometres into the Earth's crust and comprising a significant fraction of the global biosphere. The constraints of temperature, energy, dioxygen and space seemed to preclude the possibility of more-complex, multicellular organisms from surviving at these depths. Here we report species of the phylum Nematoda that have been detected in or recovered from 0.9-3.6-kilometre-deep fracture water in the deep mines of South Africa but have not been detected in the mining water. These subsurface nematodes, including a new species, Halicephalobus mephisto, tolerate high temperature, reproduce asexually and preferentially feed upon subsurface bacteria. Carbon-14 data indicate that the fracture water in which the nematodes reside is 3,000-12,000-year-old palaeometeoric water. Our data suggest that nematodes should be found in other deep hypoxic settings where temperature permits, and that they may control the microbial population density by grazing on fracture surface biofilm patches. Our results expand the known metazoan biosphere and demonstrate that deep ecosystems are more complex than previously accepted. The discovery of multicellular life in the deep subsurface of the Earth also has important implications for the search for subsurface life on other planets in our Solar System.

­­Clastic Pipes on Mars: Evidence for a Near Surface Groundwater System

NASA Astrophysics Data System (ADS)

Wheatley, D. F.; Chan, M. A.; Okubo, C. H.

2017-12-01

Clastic pipes, a type of vertical, columnar injectite, occur throughout the terrestrial stratigraphic record and are identified across many Martian terrains. Terrestrial pipe analogs can aid in identifying clastic pipes on Mars to understand their formation processes and their implications for a past near-surface groundwater system. On Earth, clastic pipes form through fluidization of overpressurized sediment. Fluidization occurs when the upward frictional (i.e., drag) forces of escaping fluids overpower the downward acting gravitational force. To create the forces necessary for pipe formation requires overpressurization of a body of water-saturated porous media overlain by a low permeability confining layer. As the pressure builds, the confining layer eventually fractures and the escaping fluids fluidize the porous sediment causing the sediment to behave like a fluid. These specific formation conditions record evidence of a violent release of fluid-suspended sediment including brecciation of the host and sealing material, internal outward grading/sorting that results in a coarser-grained commonly better cemented outer rind, traction structures, and a cylindrical geometry. Pipes form self-organized, dispersed spatial relationships due to the efficient diffusion of overpressured zones in the subsurface and the expulsion of sediment under pressure. Martian pipes occur across the northern lowlands, dichotomy boundary, and southern highlands in various forms of erosional relief ranging from newer eruption structures to eroded cylindrical/conical mounds with raised rims to highly eroded mounds/hills. Similar to terrestrial examples, Martian pipes form in evenly-spaced, self-organized arrangements. The pipes are typically internally massive with a raised outer rim (interpreted as a sorted, coarser-grained, better-cemented rim). This evidence indicates that Martian pipes formed through fluidization, which requires a near-surface groundwater system. Pipes create a window into the subsurface by excavating subsurface sediment and waters. After emplacement, pipes can also act as fluid conduits, channeling post-depositional fluid flow. The preferential porosity and flow paths may make the pipes an ideal exploration target for microbial life.

Microbial diversity in Cenozoic sediments recovered from the Lomonosov Ridge in the Central Arctic basin.

PubMed

Forschner, Stephanie R; Sheffer, Roberta; Rowley, David C; Smith, David C

2009-03-01

The current understanding of microbes inhabiting deeply buried marine sediments is based largely on samples collected from continental shelves in tropical and temperate latitudes. The geographical range of marine subsurface coring was expanded during the Integrated Ocean Drilling Program Arctic Coring Expedition (IODP ACEX). This expedition to the ice-covered central Arctic Ocean successfully cored the entire 428 m sediment stack on the Lomonosov Ridge during August and September 2004. The recovered cores vary from siliciclastic sediment low in organic carbon (< 0.2%) to organic rich ( approximately 3%) black sediments that rapidly accumulated in the early middle Eocene. Three geochemical environments were characterized based on chemical analyses of porewater: an upper ammonium oxidation zone, a carbonate dissolution zone and a deep (> 200 m below sea floor) sulfate reduction zone. The diversity of microbes within each zone was assessed using 16S rRNA phylogenetic markers. Bacterial 16S rRNA genes were successfully amplified from each of the biogeochemical zones, while archaea was only amplified from the deep sulfate reduction zone. The microbial communities at each zone are phylogenetically different and are most closely related to those from other deep subsurface environments.

Potential for hydrogen-oxidizing chemolithoautotrophic and diazotrophic populations to initiate biofilm formation in oligotrophic, deep terrestrial subsurface waters.

PubMed

Wu, Xiaofen; Pedersen, Karsten; Edlund, Johanna; Eriksson, Lena; Åström, Mats; Andersson, Anders F; Bertilsson, Stefan; Dopson, Mark

2017-03-23

Deep terrestrial biosphere waters are separated from the light-driven surface by the time required to percolate to the subsurface. Despite biofilms being the dominant form of microbial life in many natural environments, they have received little attention in the oligotrophic and anaerobic waters found in deep bedrock fractures. This study is the first to use community DNA sequencing to describe biofilm formation under in situ conditions in the deep terrestrial biosphere. In this study, flow cells were attached to boreholes containing either "modern marine" or "old saline" waters of different origin and degree of isolation from the light-driven surface of the earth. Using 16S rRNA gene sequencing, we showed that planktonic and attached populations were dissimilar while gene frequencies in the metagenomes suggested that hydrogen-fed, carbon dioxide- and nitrogen-fixing populations were responsible for biofilm formation across the two aquifers. Metagenome analyses further suggested that only a subset of the populations were able to attach and produce an extracellular polysaccharide matrix. Initial biofilm formation is thus likely to be mediated by a few bacterial populations which were similar to Epsilonproteobacteria, Deltaproteobacteria, Betaproteobacteria, Verrucomicrobia, and unclassified bacteria. Populations potentially capable of attaching to a surface and to produce extracellular polysaccharide matrix for attachment were identified in the terrestrial deep biosphere. Our results suggest that the biofilm populations were taxonomically distinct from the planktonic community and were enriched in populations with a chemolithoautotrophic and diazotrophic metabolism coupling hydrogen oxidation to energy conservation under oligotrophic conditions.

Rapid climatic signal propagation from source to sink in a southern California sediment-routing system

USGS Publications Warehouse

Covault, J.A.; Romans, B.W.; Fildani, A.; McGann, M.; Graham, S.A.

2010-01-01

Terrestrial source areas are linked to deep-sea basins by sediment-routing systems, which only recently have been studied with a holistic approach focused on terrestrial and submarine components and their interactions. Here we compare an extensive piston-core and radiocarbon-age data set from offshore southern California to contemporaneous Holocene climate proxies in order to test the hypothesis that climatic signals are rapidly propagated from source to sink in a spatially restricted sediment-routing system that includes the Santa Ana River drainage basin and the Newport deep-sea depositional system. Sediment cores demonstrate that variability in rates of Holocene deep-sea turbidite deposition is related to complex ocean-atmosphere interactions, including enhanced magnitude and frequency of the North American monsoon and El Ni??o-Southern Oscillation cycles, which increased precipitation and fluvial discharge in southern California. This relationship is evident because, unlike many sediment-routing systems, the Newport submarine canyon-and-channel system was consistently linked tothe Santa Ana River,which maintained sediment delivery even during Holocene marine transgression and highstand. Results of this study demonstrate the efficiency of sediment transport and delivery through a spatially restricted, consistently linked routing system and the potential utility of deep-sea turbidite depositional trends as paleoclimate proxies in such settings. ?? 2010 by The University of Chicago.

Deep Subsurface Life from North Pond: Enrichment, Isolation, Characterization and Genomes of Heterotrophic Bacteria

PubMed Central

Russell, Joseph A.; León-Zayas, Rosa; Wrighton, Kelly; Biddle, Jennifer F.

2016-01-01

Studies of subsurface microorganisms have yielded few environmentally relevant isolates for laboratory studies. In order to address this lack of cultivated microorganisms, we initiated several enrichments on sediment and underlying basalt samples from North Pond, a sediment basin ringed by basalt outcrops underlying an oligotrophic water-column west of the Mid-Atlantic Ridge at 22°N. In contrast to anoxic enrichments, growth was observed in aerobic, heterotrophic enrichments from sediment of IODP Hole U1382B at 4 and 68 m below seafloor (mbsf). These sediment depths, respectively, correspond to the fringes of oxygen penetration from overlying seawater in the top of the sediment column and upward migration of oxygen from oxic seawater from the basalt aquifer below the sediment. Here we report the enrichment, isolation, initial characterization and genomes of three isolated aerobic heterotrophs from North Pond sediments; an Arthrobacter species from 4 mbsf, and Paracoccus and Pseudomonas species from 68 mbsf. These cultivated bacteria are represented in the amplicon 16S rRNA gene libraries created from whole sediments, albeit at low (up to 2%) relative abundance. We provide genomic evidence from our isolates demonstrating that the Arthrobacter and Pseudomonas isolates have the potential to respire nitrate and oxygen, though dissimilatory nitrate reduction could not be confirmed in laboratory cultures. The cultures from this study represent members of abundant phyla, as determined by amplicon sequencing of environmental DNA extracts, and allow for further studies into geochemical factors impacting life in the deep subsurface. PMID:27242705

Deep Subsurface Life from North Pond: Enrichment, Isolation, Characterization and Genomes of Heterotrophic Bacteria.

PubMed

Russell, Joseph A; León-Zayas, Rosa; Wrighton, Kelly; Biddle, Jennifer F

2016-01-01

Studies of subsurface microorganisms have yielded few environmentally relevant isolates for laboratory studies. In order to address this lack of cultivated microorganisms, we initiated several enrichments on sediment and underlying basalt samples from North Pond, a sediment basin ringed by basalt outcrops underlying an oligotrophic water-column west of the Mid-Atlantic Ridge at 22°N. In contrast to anoxic enrichments, growth was observed in aerobic, heterotrophic enrichments from sediment of IODP Hole U1382B at 4 and 68 m below seafloor (mbsf). These sediment depths, respectively, correspond to the fringes of oxygen penetration from overlying seawater in the top of the sediment column and upward migration of oxygen from oxic seawater from the basalt aquifer below the sediment. Here we report the enrichment, isolation, initial characterization and genomes of three isolated aerobic heterotrophs from North Pond sediments; an Arthrobacter species from 4 mbsf, and Paracoccus and Pseudomonas species from 68 mbsf. These cultivated bacteria are represented in the amplicon 16S rRNA gene libraries created from whole sediments, albeit at low (up to 2%) relative abundance. We provide genomic evidence from our isolates demonstrating that the Arthrobacter and Pseudomonas isolates have the potential to respire nitrate and oxygen, though dissimilatory nitrate reduction could not be confirmed in laboratory cultures. The cultures from this study represent members of abundant phyla, as determined by amplicon sequencing of environmental DNA extracts, and allow for further studies into geochemical factors impacting life in the deep subsurface.

Differential Bacterial Colonization of Volcanic Minerals in Deep Thermal Basalts

NASA Astrophysics Data System (ADS)

Smith, A. R.; Popa, R.; Fisk, M. R.; Nielsen, M.; Wheat, G.; Jannasch, H.; Fisher, A.; Sievert, S.

2010-04-01

There are reports of microbial weathering patterns in volcanic glass and minerals of both terrestrial and Martian origin. Volcanic minerals are colonized differentially in subsurface hydrothermal environments by a variety of physiological types.

The nature and function of microbial enzymes in subsurface marine sediments

NASA Astrophysics Data System (ADS)

Steen, A. D.; Schmidt, J.

2016-02-01

Isotopic and genomic evidence indicates that marine sediments contain populations of active heterotrophic microorganisms which appear to metabolize old, detrital, apparently recalcitrant organic matter. In surface communities, heterotrophs use extracellular enzymes to access complex organic matter. In subsurface sediments, in which microbial doubling times can be on the order of hundreds or thousands of years, it is not clear whether extracellular enzymes could remain stable and active long enough to constitute a 'profitable' stragtegy for accessing complex organic carbon. Here we present evidence that a wide range of extracellular enzyme are active in subsurface sediments from two different environments: the White Oak River, NC, and deep (up to 80 m) sediments of the Baltic Sea Basin recovered from IODP Expedition 347. In the White Oak River, enzymes from deeper sediments appear to be better-adapted to highly-degraded organic matter than enzymes from surface sediments. In the Baltic Sea, preliminary data suggest that enzymes related to nitrogen acquisition are preferentially expressed. By characterizing the extracellular enzymes present in marine sediments, we hope to achieve a better understanding of the mechanisms that control sedimentary organic matter remineralization and preservation.

Humic acids contribution to sedimentary organic matter on a shallow continental shelf (northern Adriatic Sea)

NASA Astrophysics Data System (ADS)

Giani, M.; Rampazzo, F.; Berto, D.

2010-12-01

The shallow northern Adriatic Sea receives large river runoff, predominantly from the Po River, which is the main allochthonous source of nutrients and organic matter. The origin and quality of organic matter deposited in the sediments can influence the degradation processes and oxygen consumption in the bottom waters as well as the fate of many pollutants. Therefore the humic acids (HA) were quantified in surface and sub-surface sediments collected in an area of the north-western Adriatic platform south of Po River. HA showed to have a relevant contribution to sedimentary organic matter. HA content in sediments were positively correlated with the organic carbon concentration and negatively with redox potential and pH, particularly in sub-surface reduced sediments, suggesting their important role in the diagenetic processes taking place in anoxic conditions. Elemental composition of HA extracted from surface and sub-surface sediments showed a wide range of variation of the C org/N ratios which could be due to a mixed (terrestrial and marine) origin and/or an elevated bacteria degradation of nitrogen during diagenesis processes in sediments. The spectroscopic ratios A 2/A 4 and A 4/A 6 of HA confirmed a mixed origin with a high degree of condensation of the HA extracted from sediments.

Rates and extent of microbial debromination in the deep subseafloor biosphere

NASA Astrophysics Data System (ADS)

Berg, R. D.; Solomon, E. A.; Morris, R. M.

2013-12-01

Recent genomic and porewater geochemical data suggest that reductive dehalogenation of a wide range of halogenated organic compounds could represent an important energy source for deep subseafloor microbial communities. At continental slope sites worldwide, there is a remarkably linear relationship between porewater profiles of ammonium and bromide, indicating that the factors controlling the distribution and rates of dehalogenation have the potential to influence carbon and nitrogen cycling in the deep subsurface biosphere. Though this metabolic pathway could play an important role in the cycling of otherwise refractory pools of carbon and nitrogen in marine sediments and provide energy to microbial communities in the deep subsurface biosphere, the rates and extent of dehalogenation in marine sediments are poorly constrained. Here we report net reaction rate profiles of debromination activity in continental slope sediments, calculated from numerical modeling of porewater bromide profiles from several margins worldwide. The reaction rate profiles indicate three common zones of debromination activity in slope sediments: 1) low rates of debromination, and a potential bromine sink, in the upper sediment column correlating to the sulfate reduction zone, with net bromide removal rates from -3.6 x 10^-2 to -4.85 x 10^-1 μmol m^-2 yr^-1, 2) high rates of debromination from the sulfate-methane transition zone to ~40-100 mbsf, with net bromide release rates between 7.1 x 10^-2 to 3.9 x 10^-1 μmol m^-2 yr^-1, and 3) an inflection point at ~40-100 mbsf, below which net rates of debromination decrease by an order of magnitude and at several sites are indistinguishable from zero. These results indicate that dehalogenating activity is widely distributed in marine sediments, providing energy to fuel deep subseafloor microbial communities, with potentially important consequences for the global bromine and nitrogen cycles.

Depth Distribution and Assembly of Sulfate-Reducing Microbial Communities in Marine Sediments of Aarhus Bay

PubMed Central

Jochum, Lara M.; Chen, Xihan; Lever, Mark A.; Loy, Alexander; Jørgensen, Bo Barker; Schramm, Andreas

2017-01-01

ABSTRACT Most sulfate-reducing microorganisms (SRMs) present in subsurface marine sediments belong to uncultured groups only distantly related to known SRMs, and it remains unclear how changing geochemical zones and sediment depth influence their community structure. We mapped the community composition and abundance of SRMs by amplicon sequencing and quantifying the dsrB gene, which encodes dissimilatory sulfite reductase subunit beta, in sediment samples covering different vertical geochemical zones ranging from the surface sediment to the deep sulfate-depleted subsurface at four locations in Aarhus Bay, Denmark. SRMs were present in all geochemical zones, including sulfate-depleted methanogenic sediment. The biggest shift in SRM community composition and abundance occurred across the transition from bioturbated surface sediments to nonbioturbated sediments below, where redox fluctuations and the input of fresh organic matter due to macrofaunal activity are absent. SRM abundance correlated with sulfate reduction rates determined for the same sediments. Sulfate availability showed a weaker correlation with SRM abundances and no significant correlation with the composition of the SRM community. The overall SRM species diversity decreased with depth, yet we identified a subset of highly abundant community members that persists across all vertical geochemical zones of all stations. We conclude that subsurface SRM communities assemble by the persistence of members of the surface community and that the transition from the bioturbated surface sediment to the unmixed sediment below is a main site of assembly of the subsurface SRM community. IMPORTANCE Sulfate-reducing microorganisms (SRMs) are key players in the marine carbon and sulfur cycles, especially in coastal sediments, yet little is understood about the environmental factors controlling their depth distribution. Our results suggest that macrofaunal activity is a key driver of SRM abundance and community structure in marine sediments and that a small subset of SRM species of high relative abundance in the subsurface SRM community persists from the sulfate-rich surface sediment to sulfate-depleted methanogenic subsurface sediment. More generally, we conclude that SRM communities inhabiting the subsurface seabed assemble by the selective survival of members of the surface community. PMID:28939599

Rates of microbial metabolism in deep coastal plain aquifers

USGS Publications Warehouse

Chapelle, F.H.; Lovley, D.R.

1990-01-01

Rates of microbial metabolism in deep anaerobic aquifers of the Atlantic coastal plain of South Carolina were investigated by both microbiological and geochemical techniques. Rates of [2-14C]acetate and [U-14C]glucose oxidation as well as geochemical evidence indicated that metabolic rates were faster in the sandy sediments composing the aquifers than in the clayey sediments of the confining layers. In the sandy aquifer sediments, estimates of the rates of CO2 production (millimoles of CO2 per liter per year) based on the oxidation of [2-14C]acetate were 9.4 x 10-3 to 2.4 x 10-1 for the Black Creek aquifer, 1.1 x 10-2 for the Middendorf aquifer, and <7 x 10-5 for the Cape Fear aquifer. These estimates were at least 2 orders of magnitude lower than previously published estimates that were based on the accumulation of CO2 in laboratory incubations of similar deep subsurface sediments. In contrast, geochemical modeling of groundwater chemistry changes along aquifer flowpaths gave rate estimates that ranged from 10-4 to 10-6 mmol of CO2 per liter per year. The age of these sediments (ca. 80 million years) and their organic carbon content suggest that average rates of CO2 production could have been no more than 10-4 mmol per liter per year. Thus, laboratory incubations may greatly overestimate the in situ rates of microbial metabolism in deep subsurface environments. This has important implications for the use of laboratory incubations in attempts to estimate biorestoration capacities of deep aquifers. The rate estimates from geochemical modeling indicate that deep aquifers are among the most oligotrophic aquatic environments in which there is ongoing microbial metabolism.

Anaerobic methanotrophic communities thrive in deep submarine permafrost.

PubMed

Winkel, Matthias; Mitzscherling, Julia; Overduin, Pier P; Horn, Fabian; Winterfeld, Maria; Rijkers, Ruud; Grigoriev, Mikhail N; Knoblauch, Christian; Mangelsdorf, Kai; Wagner, Dirk; Liebner, Susanne

2018-01-22

Thawing submarine permafrost is a source of methane to the subsurface biosphere. Methane oxidation in submarine permafrost sediments has been proposed, but the responsible microorganisms remain uncharacterized. We analyzed archaeal communities and identified distinct anaerobic methanotrophic assemblages of marine and terrestrial origin (ANME-2a/b, ANME-2d) both in frozen and completely thawed submarine permafrost sediments. Besides archaea potentially involved in anaerobic oxidation of methane (AOM) we found a large diversity of archaea mainly belonging to Bathyarchaeota, Thaumarchaeota, and Euryarchaeota. Methane concentrations and δ 13 C-methane signatures distinguish horizons of potential AOM coupled either to sulfate reduction in a sulfate-methane transition zone (SMTZ) or to the reduction of other electron acceptors, such as iron, manganese or nitrate. Analysis of functional marker genes (mcrA) and fluorescence in situ hybridization (FISH) corroborate potential activity of AOM communities in submarine permafrost sediments at low temperatures. Modeled potential AOM consumes 72-100% of submarine permafrost methane and up to 1.2 Tg of carbon per year for the total expected area of submarine permafrost. This is comparable with AOM habitats such as cold seeps. We thus propose that AOM is active where submarine permafrost thaws, which should be included in global methane budgets.

Exploring Genomic Diversity Using Metagenomics of Deep-Sea Subsurface Microbes from the Louisville Seamount and the South Pacific Gyre

NASA Astrophysics Data System (ADS)

Tully, B. J.; Sylvan, J. B.; Heidelberg, J. F.; Huber, J. A.

2014-12-01

There are many limitations involved with sampling microbial diversity from deep-sea subsurface environments, ranging from physical sample collection, low microbial biomass, culturing at in situ conditions, and inefficient nucleic acid extractions. As such, we are continually modifying our methods to obtain better results and expanding what we know about microbes in these environments. Here we present analysis of metagenomes sequences from samples collected from 120 m within the Louisville Seamount and from the top 5-10cm of the sediment in the center of the south Pacific gyre (SPG). Both systems are low biomass with ~102 and ~104 cells per cm3 for Louisville Seamount samples analyzed and the SPG sediment, respectively. The Louisville Seamount represents the first in situ subseafloor basalt and the SPG sediments represent the first in situ low biomass sediment microbial metagenomes. Both of these environments, subseafloor basalt and sediments underlying oligotrophic ocean gyres, represent large provinces of the seafloor environment that remain understudied. Despite the low biomass and DNA generated from these samples, we have generated 16 near complete genomes (5 from Louisville and 11 from the SPG) from the two metagenomic datasets. These genomes are estimated to be between 51-100% complete and span a range of phylogenetic groups, including the Proteobacteria, Actinobacteria, Firmicutes, Chloroflexi, and unclassified bacterial groups. With these genomes, we have assessed potential functional capabilities of these organisms and performed a comparative analysis between the environmental genomes and previously sequenced relatives to determine possible adaptations that may elucidate survival mechanisms for these low energy environments. These methods illustrate a baseline analysis that can be applied to future metagenomic deep-sea subsurface datasets and will help to further our understanding of microbiology within these environments.

Deep subsurface life from North Pond: Enrichment, isolation, characterization and genomes of heterotrophic bacteria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, Joseph A.; Leon-Zayas, Rosa; Wrighton, Kelly

Studies of subsurface microorganisms have yielded few environmentally relevant isolates for laboratory studies. In order to address this lack of cultivated microorganisms, we initiated several enrichments on sediment and underlying basalt samples from North Pond, a sediment basin ringed by basalt outcrops underlying an oligotrophic watercolumn west of the Mid-Atlantic Ridge at 22° N. In contrast to anoxic enrichments, growth was observed in aerobic, heterotrophic enrichments from sediment of IODP Hole U1382B at 4 and 68 m below seafloor (mbsf). These sediment depths, respectively, correspond to the fringes of oxygen penetration from overlying seawater in the top of the sedimentmore » column and upward migration of oxygen from oxic seawater from the basalt aquifer below the sediment. Here we report the enrichment, isolation, initial characterization and genomes of three isolated aerobic heterotrophs from North Pond sediments; an Arthrobacter species from 4 mbsf, and Paracoccus and Pseudomonas species from 68 mbsf. These cultivated bacteria are represented in the amplicon 16S rRNA gene libraries created from whole sediments, albeit at low (up to 2%) relative abundance. We provide genomic evidence from our isolates demonstrating that the Arthrobacter and Pseudomonas isolates have the potential to respire nitrate and oxygen, though dissimilatory nitrate reduction could not be confirmed in laboratory cultures. Furthermore, the cultures from this study represent members of abundant phyla, as determined by amplicon sequencing of environmental DNA extracts, and allow for further studies into geochemical factors impacting life in the deep subsurface.« less

Deep subsurface life from North Pond: Enrichment, isolation, characterization and genomes of heterotrophic bacteria

DOE PAGES

Russell, Joseph A.; Leon-Zayas, Rosa; Wrighton, Kelly; ...

2016-05-10

Studies of subsurface microorganisms have yielded few environmentally relevant isolates for laboratory studies. In order to address this lack of cultivated microorganisms, we initiated several enrichments on sediment and underlying basalt samples from North Pond, a sediment basin ringed by basalt outcrops underlying an oligotrophic watercolumn west of the Mid-Atlantic Ridge at 22° N. In contrast to anoxic enrichments, growth was observed in aerobic, heterotrophic enrichments from sediment of IODP Hole U1382B at 4 and 68 m below seafloor (mbsf). These sediment depths, respectively, correspond to the fringes of oxygen penetration from overlying seawater in the top of the sedimentmore » column and upward migration of oxygen from oxic seawater from the basalt aquifer below the sediment. Here we report the enrichment, isolation, initial characterization and genomes of three isolated aerobic heterotrophs from North Pond sediments; an Arthrobacter species from 4 mbsf, and Paracoccus and Pseudomonas species from 68 mbsf. These cultivated bacteria are represented in the amplicon 16S rRNA gene libraries created from whole sediments, albeit at low (up to 2%) relative abundance. We provide genomic evidence from our isolates demonstrating that the Arthrobacter and Pseudomonas isolates have the potential to respire nitrate and oxygen, though dissimilatory nitrate reduction could not be confirmed in laboratory cultures. Furthermore, the cultures from this study represent members of abundant phyla, as determined by amplicon sequencing of environmental DNA extracts, and allow for further studies into geochemical factors impacting life in the deep subsurface.« less

The deep, hot biosphere: Twenty-five years of retrospection.

PubMed

Colman, Daniel R; Poudel, Saroj; Stamps, Blake W; Boyd, Eric S; Spear, John R

2017-07-03

Twenty-five years ago this month, Thomas Gold published a seminal manuscript suggesting the presence of a "deep, hot biosphere" in the Earth's crust. Since this publication, a considerable amount of attention has been given to the study of deep biospheres, their role in geochemical cycles, and their potential to inform on the origin of life and its potential outside of Earth. Overwhelming evidence now supports the presence of a deep biosphere ubiquitously distributed on Earth in both terrestrial and marine settings. Furthermore, it has become apparent that much of this life is dependent on lithogenically sourced high-energy compounds to sustain productivity. A vast diversity of uncultivated microorganisms has been detected in subsurface environments, and we show that H 2 , CH 4 , and CO feature prominently in many of their predicted metabolisms. Despite 25 years of intense study, key questions remain on life in the deep subsurface, including whether it is endemic and the extent of its involvement in the anaerobic formation and degradation of hydrocarbons. Emergent data from cultivation and next-generation sequencing approaches continue to provide promising new hints to answer these questions. As Gold suggested, and as has become increasingly evident, to better understand the subsurface is critical to further understanding the Earth, life, the evolution of life, and the potential for life elsewhere. To this end, we suggest the need to develop a robust network of interdisciplinary scientists and accessible field sites for long-term monitoring of the Earth's subsurface in the form of a deep subsurface microbiome initiative.

Aromatic-degrading Sphingomonas isolates from the deep subsurface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fredrickson, J.K.; Romine, M.F.; Balkwill, D.L.

An obligately aerobic chemoheterotrophic bacterium (strain F199) previously isolated from Southeast Coastal Plain subsurface sediments and shown to degrade toluene, naphthalene, and other aromatic compounds was characterized by analysis of its 16S rRNA nucleotide base sequence and cellular lipid composition. Strain F199 contained 2-OH14:0 and 18:1{omega}7c as the predominant cellular fatty acids and sphingolipids that are characteristic of the genus Sphingomonas. Phylogenetic analysis of its 16SrRNA sequence indicated that F199 was most closely related to Sphingomonas capsulata among the bacteria currently in the Ribosomal Database. Five additional isolates from deep Southeast Coastal Plain sediments were determined by 16S rRNA sequencemore » analysis to be closely related to F199. These strains also contained characteristic sphingolipids. Four of these five strains could also grow on a broad range of aromatic compounds and could mineralize [{sup 14C}]toluene and [{sup 14C}]naphthalene. S. capsulata (ATCC 14666), Sphingomonas paucimobiolis (ATCC 29837), and one of the subsurface isolates were unable to grow on any of the aromatic compounds or mineralize toluene or naphthalene. These results indicate that bacteria within the genus Sphingomonas are present in Southeast Coastal Plain subsurface sediments and that the capacity for degrading a broad range of substituted aromatic compounds appears to be common among Sphingomonas species from this environment. 41 refs., 2 figs., 5 tabs.« less

Variability in aerobic methane oxidation over the past 1.2 Myrs recorded in microbial biomarker signatures from Congo fan sediments

NASA Astrophysics Data System (ADS)

Talbot, Helen M.; Handley, Luke; Spencer-Jones, Charlotte L.; Dinga, Bienvenu Jean; Schefuß, Enno; Mann, Paul J.; Poulsen, John R.; Spencer, Robert G. M.; Wabakanghanzi, Jose N.; Wagner, Thomas

2014-05-01

Methane (CH4) is a strong greenhouse gas known to have perturbed global climate in the past, especially when released in large quantities over short time periods from continental or marine sources. It is therefore crucial to understand and, if possible, quantify the individual and combined response of these variable methane sources to natural climate variability. However, past changes in the stability of greenhouse gas reservoirs remain uncertain and poorly constrained by geological evidence. Here, we present a record from the Congo fan of a highly specific bacteriohopanepolyol (BHP) biomarker for aerobic methane oxidation (AMO), 35-aminobacteriohopane-30,31,32,33,34-pentol (aminopentol), that identifies discrete periods of increased AMO as far back as 1.2 Ma. Fluctuations in the concentration of aminopentol, and other 35-aminoBHPs, follow a pattern that correlates with late Quaternary glacial-interglacial climate cycles, with highest concentrations during warm periods. We discuss possible sources of aminopentol, and the methane consumed by the precursor methanotrophs, within the context of the Congo River setting, including supply of methane oxidation markers from terrestrial watersheds and/or marine sources (gas hydrate and/or deep subsurface gas reservoir). Compound-specific carbon isotope values of -30‰ to -40‰ for BHPs in ODP 1075 and strong similarities between the BHP signature of the core and surface sediments from the Congo estuary and floodplain wetlands from the interior of the Congo River Basin, support a methanotrophic and likely terrigenous origin of the 35-aminoBHPs found in the fan sediments. This new evidence supports a causal connection between marine sediment BHP records of tropical deep sea fans and wetland settings in the feeding river catchments, and thus tropical continental hydrology. Further research is needed to better constrain the different sources and pathways of methane emission. However, this study identifies the large potential of aminoBHPs, in particular aminopentol, to trace and, once better calibrated and understood, quantify past methane sources and fluxes from terrestrial and potentially also marine sources.

Single cell genomic study of Dehalococcoidites in deep sea sediments of Peru Margin 1230

NASA Astrophysics Data System (ADS)

Kaster, A.; Meyer-Blackwell, K.; Spormann, A. M.

2013-12-01

Dehalogenating Chloroflexi, such as Dehalococcoidites Dhc were originally discovered as the key microorganisms mediating reductive dehalogenation of the prevalent groundwater contaminants tetrachloroethene and trichloroethene. Molecular and genomic studies on their key enzymes for energy conservation, reductive dehalogenases rdh, have provided evidence for ubiquitous horizontal gene transfer. A pioneering study by Futagami et al. discovered novel putative rdh phylotypes in sediments from the Pacific, revealing an unknown and surprising abundance of rdh genes in pristine habitats. The frequent detection of Dhc-related 16S rRNA genes from these environments implied the occurrence of dissimilatory dehalorespiration in marine subsurface sediments, however, pristine Dhc could never be linked to this activity. Despite being ubiquitous in those environments, metabolic life style or ecological function of Dhc in the absence of anthropogenic contaminants is still completely unknown. We therefore analyzed a non-contaminated deep sea sediment sample of the Peru Margin 1230 site by a single cell genomic (SGC) approach. We present for the first time data on three single Dhc cells, helping to elucidate their role in the poorly understood oligotrophic marine sub-surface environment.

Investigations in Martian Sedimentology

NASA Technical Reports Server (NTRS)

Moore, Jeffrey M.

1998-01-01

The purpose of this report is to investigate and discuss the Martian surface. This report was done in specific tasks. The tasks were: characterization of Martian fluids and chemical sediments; mass wasting and ground collapse in terrains of volatile-rich deposits; Mars Rover terrestrial field investigations; Mars Pathfinder operations support; and Martian subsurface water instrument.

Potential Physiologies of Deep Branches on the Tree of Life with Deep Subsurface Samples from IODP Leg 347: Baltic Sea Paleoenvironment

NASA Astrophysics Data System (ADS)

Lloyd, K. G.; Bird, J. T.; Shumaker, A.

2014-12-01

Very little is known about how evolutionary branches that are distantly related to cultured microorganisms make a living in the deep subsurface marine environment. Here, sediments are cut-off from surface inputs of organic substrates for tens of thousands of years; yet somehow support a diverse population of microorganisms. We examined the potential metabolic and ecological roles of uncultured archaea and bacteria in IODP Leg 347: Baltic Sea Paleoenvironment samples, using quantitative PCR holes 60B, 63E, 65C, and 59C and single cell genomic analysis for hole 60B. We quantified changes in total archaea and bacteria, as well as deeply-branching archaeal taxa with depth. These sediment cores alternate between high and low salinities, following a glacial cycle. This allows changes in the quantities of these groups to be placed in the context of potentially vastly different organic matter sources. In addition, single cells were isolated, and their genomes were amplified and sequenced to allow a deeper look into potential physiologies of uncultured deeply-branching organisms found up to 86 meters deep in marine sediments. Together, these data provide deeper insight into the relationship between microorganisms and their organic matter substrates in this extreme environments.

Investigation of North Pond crustal fluids by poised potential methods

NASA Astrophysics Data System (ADS)

Jones, R. M.; Orcutt, B.

2017-12-01

Microbes are present in the deep subsurface but their rates of activity, potential metabolisms and roles in the environment are still largely unknown. The marine deep crustal subsurface accounts for approximately 2.3x1018 m2 of the earth's volume, making this environment potentially significant to earth processes despite low productivity inherent in resource limited conditions. This has implications for geochemical cycling and exploring limits of life, linking to the `follow the energy' approach for defining habitability on earth and further afield. Most resources for life in the marine deep crust originate from rock. One subset of lithotrophic interactions involves direct transfer between electron acceptors and donors embedded in minerals and microbes. In this investigation, poised potential methods such as chronoamperometry were used to investigate mineral-microbe electron transfer interactions in the context of North Pond, a Mid-Atlantic ridge site representative of cool, sediment-covered basalts that make up the majority of the deep marine subsurface. Electrodes were poised at potentials corresponding approximately to particular lithotrophic oxidation reactions to enrich for sub-sections of North Pond deep subsurface fluid communities that were associated with direct electron transfer at these potentials.

Fungal diversity from deep marine subsurface sediments (IODP 317, Canterbury Basin, New Zealand)

NASA Astrophysics Data System (ADS)

Redou, V.; Arzur, D.; Burgaud, G.; Barbier, G.

2012-12-01

Recent years have seen a growing interest regarding micro-eukaryotic communities in extreme environments as a third microbial domain after Bacteria and Archaea. However, knowledge is still scarce and the diversity of micro-eukaryotes in such environments remains hidden and their ecological role unknown. Our research program is based on the deep sedimentary layers of the Canterbury Basin in New Zealand (IODP 317) from the subsurface to the record depth of 1884 meters below seafloor. The objectives of our study are (i) to assess the genetic diversity of fungi in deep-sea sediments and (ii) identify the functional part in order to better understand the origin and the ecological role of fungal communities in this extreme ecosystem. Fingerprinting-based methods using capillary electrophoresis single-strand conformation polymorphism and denaturing high-performance liquid chromatography were used as a first step to raise our objectives. Molecular fungal diversity was assessed using amplification of ITS1 (Internal Transcribed Spacer 1) as a biomarker on 11 samples sediments from 3.76 to 1884 meters below seafloor. Fungal molecular signatures were detected throughout the sediment core. The phyla Ascomycota and Basidiomycota were revealed with DNA as well as cDNA. Most of the phylotypes are affiliated to environmental sequences and some to common fungal cultured species. The discovery of a present and metabolically active fungal component in this unique ecosystem allows some interesting first hypotheses that will be further combined to culture-based methods and deeper molecular methods (454 pyrosequencing) to highlight essential informations regarding physiology and ecological role of fungal communities in deep marine sediments.

Active subsurface cellular function in the Baltic Sea Basin, IODP Exp 347

NASA Astrophysics Data System (ADS)

Reese, B. K.; Zinke, L. A.; Bird, J. T.; Lloyd, K. G.; Marshall, I.; Amend, J.; Jørgensen, B. B.

2016-12-01

The Baltic Sea Basin is a unique depositional setting that has experienced periods of glaciation and deglaciation as a result of global temperature fluctuations over the course of several hundred thousand years. This has resulted in laminated sediments formed during periods with strong permanent salinity stratification. The high sedimentation rates (100-500 cm/1000 y) make this an ideal setting to understand the microbial structure of a deep biosphere community in a high-organic matter environment. The responses of deep sediment microbial communities to variations in conditions during and after deposition are poorly understood. Samples were collected through scientific drilling during the International Ocean Discovery Program (IODP) Expedition 347 on board the Greatship Manisha, September-November 2013. We examined the active microbial community structure using the 16S rRNA gene transcript and active functional genes through metatranscriptome sequencing. Major biogeochemical shifts have been observed in response to the depositional history between the limnic, brackish, and marine phases. The microbial community structure in the BSB is diverse and reflective of the unique changes in the geochemical profile. These data further define the existence life in the deep subsurface and the survival mechanisms required for this extreme environment.

Heterotrophic potential of Atribacteria from deep marine Antarctic sediment

NASA Astrophysics Data System (ADS)

Carr, S. A.; Orcutt, B.; Mandernack, K. W.; Spear, J. R.

2015-12-01

Bacteria belonging to the newly classified candidate phylum "Atribacteria" (formerly referred to as "OP9" and "JS1") are common in anoxic methane-rich sediments. However, the metabolic functions and biogeochemical role of these microorganisms in the subsurface remains unrealized due to the lack of pure culture representatives. This study observed a steady increase of Atribacteria-related sequences with increasing sediment depth throughout the methane-rich zone of the Adélie Basin, Antarctica (according to a 16S rRNA gene survey). To explore the functional potential of Atribacteria in this basin, samples from various depths (14, 25 and 97 meters below seafloor), were subjected to metagenomic sequencing. Additionally, individual cells were separated from frozen, unpreserved sediment for whole genome amplification. The successful isolation and sequencing of a single-amplified Atribacteria genome from these unpreserved sediments demonstrates a future use of single cell techniques with previously collected and frozen sediments. Our resulting single-cell amplified genome, combined with metagenomic interpretations, provides our first insights to the functional potential of Atribacteria in deep subsurface settings. As observed for non-marine Atribacteria, genomic analyses suggest a heterotrophic metabolism, with Atribacteria potentially producing fermentation products such as acetate, ethanol and CO2. These products may in turn support methanogens within the sediment microbial community and explain the frequent occurrence of Atribacteria in anoxic methane-rich sediments.

The deep, hot biosphere: Twenty-five years of retrospection

PubMed Central

Colman, Daniel R.; Poudel, Saroj; Stamps, Blake W.; Boyd, Eric S.; Spear, John R.

2017-01-01

Twenty-five years ago this month, Thomas Gold published a seminal manuscript suggesting the presence of a “deep, hot biosphere” in the Earth’s crust. Since this publication, a considerable amount of attention has been given to the study of deep biospheres, their role in geochemical cycles, and their potential to inform on the origin of life and its potential outside of Earth. Overwhelming evidence now supports the presence of a deep biosphere ubiquitously distributed on Earth in both terrestrial and marine settings. Furthermore, it has become apparent that much of this life is dependent on lithogenically sourced high-energy compounds to sustain productivity. A vast diversity of uncultivated microorganisms has been detected in subsurface environments, and we show that H2, CH4, and CO feature prominently in many of their predicted metabolisms. Despite 25 years of intense study, key questions remain on life in the deep subsurface, including whether it is endemic and the extent of its involvement in the anaerobic formation and degradation of hydrocarbons. Emergent data from cultivation and next-generation sequencing approaches continue to provide promising new hints to answer these questions. As Gold suggested, and as has become increasingly evident, to better understand the subsurface is critical to further understanding the Earth, life, the evolution of life, and the potential for life elsewhere. To this end, we suggest the need to develop a robust network of interdisciplinary scientists and accessible field sites for long-term monitoring of the Earth’s subsurface in the form of a deep subsurface microbiome initiative. PMID:28674200

Nucleic acid based quantitative microbial community analysis in different marine and terrestrial sediments

NASA Astrophysics Data System (ADS)

Schippers, A.; Blazejak, A.; Köweker, G.

2009-12-01

Sub-seafloor sediments harbour over half of all prokaryotic cells on Earth. This immense cell number is calculated from numerous microscopic cell counts (AODC) in ODP sediment cores. Since AODC can not differentiate between living or dead cells, the population size of living microorganisms and the abundance of different prokaryotic groups are unknown. Recent molecular nucleic acid and biomarker analyses showed that a high proportion of the cells are alive and that the microbial communities of deep marine sediments harbour members of distinct, uncultured bacterial and archaeal lineages. The main objective of our project is the quantification of living prokaryotes in various sediments. Deep sediment samples from the Pacific and the Atlantic Oceans (ODP Legs 201 and 207, IODP Exp. 307 and 308), sediments from the Indian Ocean (RV Sonne 189-2) and the Black Sea (RV Meteor 51/4) as well as terrestrial Chesapeake Bay Sediments (ICDP) were analyzed using Catalyzed Reporter Deposition - Fluorescence In Situ Hybridisation (CARD - FISH) and quantitative, real-time PCR (Q-PCR), targeting either the 16S rRNA gene or the functional genes dsrA, mcrA and aprA to quantify microorganisms of various phylogenetic or physiological groups (e.g. JS1 cluster and Chloroflexi). At all sediment sites, cell numbers decreased with depth, however, the abundance of particular microbial groups varied at different sites and depths. The results indicate that global estimates of the deep biosphere should be reconsidered.

Zonation of Microbial Communities by a Hydrothermal Mound in the Atlantis II Deep (the Red Sea).

PubMed

Wang, Yong; Li, Jiang Tao; He, Li Sheng; Yang, Bo; Gao, Zhao Ming; Cao, Hui Luo; Batang, Zenon; Al-Suwailem, Abdulaziz; Qian, Pei-Yuan

2015-01-01

In deep-sea geothermal rift zones, the dispersal of hydrothermal fluids of moderately-high temperatures typically forms subseafloor mounds. Major mineral components of the crust covering the mound are barite and metal sulfides. As a result of the continental rifting along the Red Sea, metalliferous sediments accumulate on the seafloor of the Atlantis II Deep. In the present study, a barite crust was identified in a sediment core from the Atlantis II Deep, indicating the formation of a hydrothermal mound at the sampling site. Here, we examined how such a dense barite crust could affect the local environment and the distribution of microbial inhabitants. Our results demonstrate distinctive features of mineral components and microbial communities in the sediment layers separated by the barite crust. Within the mound, archaea accounted for 65% of the community. In contrast, the sediments above the barite boundary were overwhelmed by bacteria. The composition of microbial communities under the mound was similar to that in the sediments of the nearby Discovery Deep and marine cold seeps. This work reveals the zonation of microbial communities after the formation of the hydrothermal mound in the subsurface sediments of the rift basin.

Zonation of Microbial Communities by a Hydrothermal Mound in the Atlantis II Deep (the Red Sea)

PubMed Central

Wang, Yong; Li, Jiang Tao; He, Li Sheng; Yang, Bo; Gao, Zhao Ming; Cao, Hui Luo; Batang, Zenon; Al-Suwailem, Abdulaziz; Qian, Pei-Yuan

2015-01-01

In deep-sea geothermal rift zones, the dispersal of hydrothermal fluids of moderately-high temperatures typically forms subseafloor mounds. Major mineral components of the crust covering the mound are barite and metal sulfides. As a result of the continental rifting along the Red Sea, metalliferous sediments accumulate on the seafloor of the Atlantis II Deep. In the present study, a barite crust was identified in a sediment core from the Atlantis II Deep, indicating the formation of a hydrothermal mound at the sampling site. Here, we examined how such a dense barite crust could affect the local environment and the distribution of microbial inhabitants. Our results demonstrate distinctive features of mineral components and microbial communities in the sediment layers separated by the barite crust. Within the mound, archaea accounted for 65% of the community. In contrast, the sediments above the barite boundary were overwhelmed by bacteria. The composition of microbial communities under the mound was similar to that in the sediments of the nearby Discovery Deep and marine cold seeps. This work reveals the zonation of microbial communities after the formation of the hydrothermal mound in the subsurface sediments of the rift basin. PMID:26485717

Molecular hydrogen: An abundant energy source for bacterial activity in nuclear waste repositories

NASA Astrophysics Data System (ADS)

Libert, M.; Bildstein, O.; Esnault, L.; Jullien, M.; Sellier, R.

A thorough understanding of the energy sources used by microbial systems in the deep terrestrial subsurface is essential since the extreme conditions for life in deep biospheres may serve as a model for possible life in a nuclear waste repository. In this respect, H 2 is known as one of the most energetic substrates for deep terrestrial subsurface environments. This hydrogen is produced from abiotic and biotic processes but its concentration in natural systems is usually maintained at very low levels due to hydrogen-consuming bacteria. A significant amount of H 2 gas will be produced within deep nuclear waste repositories, essentially from the corrosion of metallic components. This will consequently improve the conditions for microbial activity in this specific environment. This paper discusses different study cases with experimental results to illustrate the fact that microorganisms are able to use hydrogen for redox processes (reduction of O 2, NO3-, Fe III) in several waste disposal conditions. Consequences of microbial activity include: alteration of groundwater chemistry and shift in geochemical equilibria, gas production or consumption, biocorrosion, and potential modifications of confinement properties. In order to quantify the impact of hydrogen bacteria, the next step will be to determine the kinetic rate of the reactions in realistic conditions.

Phylogenetic and Functional Diversity of Microbial Communities Associated with Subsurface Sediments of the Sonora Margin, Guaymas Basin

PubMed Central

Vigneron, Adrien; Cruaud, Perrine; Roussel, Erwan G.; Pignet, Patricia; Caprais, Jean-Claude; Callac, Nolwenn; Ciobanu, Maria-Cristina; Godfroy, Anne; Cragg, Barry A.; Parkes, John R.; Van Nostrand, Joy D.; He, Zhili; Zhou, Jizhong; Toffin, Laurent

2014-01-01

Subsurface sediments of the Sonora Margin (Guaymas Basin), located in proximity of active cold seep sites were explored. The taxonomic and functional diversity of bacterial and archaeal communities were investigated from 1 to 10 meters below the seafloor. Microbial community structure and abundance and distribution of dominant populations were assessed using complementary molecular approaches (Ribosomal Intergenic Spacer Analysis, 16S rRNA libraries and quantitative PCR with an extensive primers set) and correlated to comprehensive geochemical data. Moreover the metabolic potentials and functional traits of the microbial community were also identified using the GeoChip functional gene microarray and metabolic rates. The active microbial community structure in the Sonora Margin sediments was related to deep subsurface ecosystems (Marine Benthic Groups B and D, Miscellaneous Crenarchaeotal Group, Chloroflexi and Candidate divisions) and remained relatively similar throughout the sediment section, despite defined biogeochemical gradients. However, relative abundances of bacterial and archaeal dominant lineages were significantly correlated with organic carbon quantity and origin. Consistently, metabolic pathways for the degradation and assimilation of this organic carbon as well as genetic potentials for the transformation of detrital organic matters, hydrocarbons and recalcitrant substrates were detected, suggesting that chemoorganotrophic microorganisms may dominate the microbial community of the Sonora Margin subsurface sediments. PMID:25099369

Prospecting for Martian Ice from Orbit

NASA Technical Reports Server (NTRS)

Kanner, L. C.; Bell, M. S.; Allen, C. C.

2003-01-01

Recent data from the Gamma-Ray Spectrometer (GRS) on Mars Odyssey indicate the presence of a hydrogen-rich layer tens of centimeters thick in high latitudes on Mars. This hydrogen-rich layer correlates to previously determined regions of ice stability. It has been suggested that the subsurface hydrogen is ice and constitutes 35 plus or minus 15% by weight near the north and south polar regions. This study constrains the location of subsurface ice deposits on the scale of kilometers or smaller by combining GRS data with surface features indicative of subsurface ice. The most recognizable terrestrial geomorphic indicators of subsurface ice, formed in permafrost and periglacial environments, include thermokarst pits, pingos, pseudocraters and patterned ground. Patterned ground features have geometric forms such as circles, polygons, stripes and nets. This study focuses on the polygonal form of patterned ground, selected for its discernable shape and subsurface implications. Polygonal features are typically demarcated by troughs, beneath which grow vertical ice-wedges. Ice-wedges form in thermal contraction cracks in ice-rich soil and grow with annual freezing and thawing events repeated over tens of years. Ice wedges exist below the depth of seasonal freeze-thaw. Terrestrial ice wedges can be several meters deep and polygons can be tens of meters apart, and, on rare occasions, up to 1 km. The crack spacing of terrestrial polygons is typically 3 to 10 times the crack depth.

Submarine groundwater discharge into the coast revealed by water chemistry of man-made undersea liquefied petroleum gas cavern

NASA Astrophysics Data System (ADS)

Lee, Jin-Yong; Cho, Byung Wook

2008-10-01

SummaryThe occurrence of submarine groundwater discharge (SGD) as well as its supply of many nutrients and metals to coastal seawaters is now generally known. However, previous studies have focused on the chemical and radiological analysis of groundwater, surface seawater, shallow marine sediments and their pore waters, as well as the measurement of upward flow through the marine sediments, as end members of the discharge process. In this study, chemical and isotopic analysis results of marine subsurface waters are reported. These were obtained from deep boreholes of an undersea liquefied petroleum gas (LPG) storage cavern, located about 8 km off the western coast of Korea. The cavern is about 130-150 m below the sea bottom, which is covered by a 4.8-19.5 m silty clay stratum. An isotopic composition (δ 2H and δ 18O) of the marine subsurface waters falls on a mixing line between terrestrial groundwater and seawater. Vertical EC profiling at the cavern boreholes revealed the existence of a fresh water zone. An increase in the contents of ferrous iron and manganese and a decrease in levels of nitrate, bicarbonate and cavern seepage were recorded in August 2006, indicating a decreased submarine groundwater flux originating from land, mainly caused by an elevated cavern gas pressure. It is suggested in this study that the main source of fresh waters in the man-made undersea cavern is the submarine groundwater discharge mainly originating from the land.

Low temperature hydrothermal maturation of organic matter in sediments from the Atlantis II Deep, Red Sea

NASA Technical Reports Server (NTRS)

Simoneit, Bernd R. T.; Grimalt, Joan O.; Hayes, J. M.; Hartman, Hyman

1987-01-01

Hydrocarbons and bulk organic matter of two sediment cores within the Atlantis II Deep are analyzed, and microbial inputs and minor terrestrial sources are found to represent the major sedimentary organic material. Results show that extensive acid-catalyzed reactions are occurring in the sediments, and the Atlantis II Deep is found to exhibit a lower degree of thermal maturation than other hydrothermal or intrusive systems. The lack of carbon number preference noted among the n-alkanes suggests that the organic matter of these sediments has undergone some degree of catagenesis, though yields of hydrocarbons are much lower than those found in other hydrothermal areas, probably due to the effect of lower temperature and poor source-rock characteristics.

Where the oil from surface and subsurface plumes deposited during/after Deepwater Horizon oil spill?

NASA Astrophysics Data System (ADS)

Yan, B.

2016-02-01

The Deepwater Horizon (DwH) oil spill released an estimated 4.9 million barrels (about 200 million gallons) of crude oil into the Gulf of Mexico between April 20, 2010 and July 15, 2010. Though Valentine et al. has linked the elevated oil components in some sediments with the subsurface plume, the sites with fallout from the ocean surface plume has not been identified. This piece of information is critical not only for a comprehensive scientific understanding of the ecosystem response and fate of spill-related pollutants, but also for litigation purposes and future spill response and restoration planning. In this study we focus on testing the hypothesis that marine snow from the surface plume were deposited on the sea floor over a broad area. To do so, we use publicly available data generated as part of the ongoing Natural Resource Damage Assessment (NRDA) process to assess the spatial distribution of petroleum hydrocarbons in the water column and deep-ocean sediments of the Gulf of Mexico. Sensitive hydrocarbon markers are used to differentiate hydrocarbons from surface plume, deep subsurface plume, and in-situ burning. Preliminary results suggest the overlapping but different falling sites of these plumes and the sedimentation process was controlled by various biological, chemical, and physical factors.

Archaea in Organic-Lean and Organic-Rich Marine Subsurface Sediments: An Environmental Gradient Reflected in Distinct Phylogenetic Lineages

PubMed Central

Durbin, Alan M.; Teske, Andreas

2012-01-01

Examining the patterns of archaeal diversity in little-explored organic-lean marine subsurface sediments presents an opportunity to study the association of phylogenetic affiliation and habitat preference in uncultured marine Archaea. Here we have compiled and re-analyzed published archaeal 16S rRNA clone library datasets across a spectrum of sediment trophic states characterized by a wide range of terminal electron-accepting processes. Our results show that organic-lean marine sediments in deep marine basins and oligotrophic open ocean locations are inhabited by distinct lineages of archaea that are not found in the more frequently studied, organic-rich continental margin sediments. We hypothesize that different combinations of electron donor and acceptor concentrations along the organic-rich/organic-lean spectrum result in distinct archaeal communities, and propose an integrated classification of habitat characteristics and archaeal community structure. PMID:22666218

Estimating growth rates of uncultivated clades of archaea and bacteria in marine sediments

NASA Astrophysics Data System (ADS)

Lloyd, K. G.

2016-12-01

The vast majority of microbes present in marine sediments have never been cultivated in laboratory conditions. It is therefore difficult to estimate the growth rates of these organisms in situ. Quantitative PCR (qPCR) and 16S rRNA gene libraries from sediments below 10 cm show very little change in abundance of these organisms with depth or with redox conditions. Therefore, we hypothesized that uncultivated clades of bacteria and archaea that are ubiquitous in marine sediments, actually grow in the upper 10 cm of marine sediments. We collected sediment cores from the White Oak River estuary, sectioned them in 1 cm intervals, and examined the changes in abundance of uncultivated microbes with depth using 16S rRNA gene libraries and qPCR. We found that some of the key clades associated with the deep subsurface microbiome, such as Bathyarchaeota and MBG-D, increase in abundance with depth, demonstrating extremely slow growth in these shallow subsurface sediments.

Community dynamics of anaerobic bacteria in deep petroleum reservoirs

NASA Astrophysics Data System (ADS)

Hallmann, Christian; Schwark, Lorenz; Grice, Kliti

2008-09-01

The nature, activity and metabolism of microbes that inhabit the deep subsurface environment are a matter of ongoing debate. Primarily limited by temperature, little is known about secondary factors that restrict or enhance microbial activity or about the extent of a habitable environment deep below the surface. In particular, the degraders of chemically inert organic substrates remain elusive. Petroleum reservoirs can be regarded as natural bioreactors and are ideally suited for the study of microbial metabolism in the deep subsurface. Here we analyse series of oil samples that were biodegraded to different degrees. We find fatty acids after hydrolysis of purified crude oil fractions, indicating the presence of intact phospholipids and suggesting that indigenous bacteria inhabit petroleum reservoirs in sediment depths of up to 2,000m. A major change in bacterial community structure occurs after the removal of n-alkanes, indicating that more than one consortium is responsible for petroleum degradation. Our results suggest that further study of petroleum fluids will help understand bacterial metabolism and diversity in this habitat of the deep subsurface.

The Ability of Microbial Community of Lake Baikal Bottom Sediments Associated with Gas Discharge to Carry Out the Transformation of Organic Matter under Thermobaric Conditions

PubMed Central

Bukin, Sergei V.; Pavlova, Olga N.; Manakov, Andrei Y.; Kostyreva, Elena A.; Chernitsyna, Svetlana M.; Mamaeva, Elena V.; Pogodaeva, Tatyana V.; Zemskaya, Tamara I.

2016-01-01

The ability to compare the composition and metabolic potential of microbial communities inhabiting the subsurface sediment in geographically distinct locations is one of the keys to understanding the evolution and function of the subsurface biosphere. Prospective areas for study of the subsurface biosphere are the sites of hydrocarbon discharges on the bottom of the Lake Baikal rift, where ascending fluxes of gas-saturated fluids and oil from deep layers of bottom sediments seep into near-surface sediment. The samples of surface sediments collected in the area of the Posolskaya Bank methane seep were cultured for 17 months under thermobaric conditions (80°C, 5 MPa) with the addition of complementary organic substrate, and a different composition for the gas phase. After incubation, the presence of intact cells of microorganisms, organic matter transformation and the formation of oil biomarkers was confirmed in the samples, with the addition of Baikal diatom alga Synedra acus detritus, and gas mixture CH4:H2:CO2. Taxonomic assignment of the 16S rRNA sequence data indicates that the predominant sequences in the enrichment were Sphingomonas (55.3%), Solirubrobacter (27.5%) and Arthrobacter (16.6%). At the same time, in heat-killed sediment and in sediment without any additional substrates, which were cultivated in a CH4 atmosphere, no geochemical changes were detected, nor the presence of intact cells and 16S rRNA sequences of Bacteria and Archaea. This data may suggest that the decomposition of organic matter under culturing conditions could be performed by microorganisms from low-temperature sediment layers. One possible explanation of this phenomenon is migration of the representatives of the deep thermophilic community through fault zones in the near surface sediment layers, together with gas-bearing fluids. PMID:27242716

The Ability of Microbial Community of Lake Baikal Bottom Sediments Associated with Gas Discharge to Carry Out the Transformation of Organic Matter under Thermobaric Conditions.

PubMed

Bukin, Sergei V; Pavlova, Olga N; Manakov, Andrei Y; Kostyreva, Elena A; Chernitsyna, Svetlana M; Mamaeva, Elena V; Pogodaeva, Tatyana V; Zemskaya, Tamara I

2016-01-01

The ability to compare the composition and metabolic potential of microbial communities inhabiting the subsurface sediment in geographically distinct locations is one of the keys to understanding the evolution and function of the subsurface biosphere. Prospective areas for study of the subsurface biosphere are the sites of hydrocarbon discharges on the bottom of the Lake Baikal rift, where ascending fluxes of gas-saturated fluids and oil from deep layers of bottom sediments seep into near-surface sediment. The samples of surface sediments collected in the area of the Posolskaya Bank methane seep were cultured for 17 months under thermobaric conditions (80°C, 5 MPa) with the addition of complementary organic substrate, and a different composition for the gas phase. After incubation, the presence of intact cells of microorganisms, organic matter transformation and the formation of oil biomarkers was confirmed in the samples, with the addition of Baikal diatom alga Synedra acus detritus, and gas mixture CH4:H2:CO2. Taxonomic assignment of the 16S rRNA sequence data indicates that the predominant sequences in the enrichment were Sphingomonas (55.3%), Solirubrobacter (27.5%) and Arthrobacter (16.6%). At the same time, in heat-killed sediment and in sediment without any additional substrates, which were cultivated in a CH4 atmosphere, no geochemical changes were detected, nor the presence of intact cells and 16S rRNA sequences of Bacteria and Archaea. This data may suggest that the decomposition of organic matter under culturing conditions could be performed by microorganisms from low-temperature sediment layers. One possible explanation of this phenomenon is migration of the representatives of the deep thermophilic community through fault zones in the near surface sediment layers, together with gas-bearing fluids.

Marine Subsurface Microbial Community Shifts Across a Hydrothermal Gradient in Okinawa Trough Sediments

PubMed Central

2016-01-01

Sediments within the Okinawa back-arc basin overlay a subsurface hydrothermal network, creating intense temperature gradients with sediment depth and potential limits for microbial diversity. We investigated taxonomic changes across 45 m of recovered core with a temperature gradient of 3°C/m from the dynamic Iheya North Hydrothermal System. The interval transitions sharply from low-temperature marine mud to hydrothermally altered clay at 10 meters below seafloor (mbsf). Here, we present taxonomic results from an analysis of the 16S rRNA gene that support a conceptual model in which common marine subsurface taxa persist into the subsurface, while high temperature adapted archaeal taxa show localized peaks in abundances in the hydrothermal clay horizons. Specifically, the bacterial phylum Chloroflexi accounts for a major proportion of the total microbial community within the upper 10 mbsf, whereas high temperature archaea (Terrestrial Hot Spring Crenarchaeotic Group and methanotrophic archaea) appear in varying local abundances in deeper, hydrothermal clay horizons with higher in situ temperatures (up to 55°C, 15 mbsf). In addition, geochemical evidence suggests that methanotrophy may be occurring in various horizons. There is also relict DNA (i.e., DNA preserved after cell death) that persists in horizons where the conditions suitable for microbial communities have ceased. PMID:28096736

Fungal and Prokaryotic Activities in the Marine Subsurface Biosphere at Peru Margin and Canterbury Basin Inferred from RNA-Based Analyses and Microscopy

PubMed Central

Pachiadaki, Maria G.; Rédou, Vanessa; Beaudoin, David J.; Burgaud, Gaëtan; Edgcomb, Virginia P.

2016-01-01

The deep sedimentary biosphere, extending 100s of meters below the seafloor harbors unexpected diversity of Bacteria, Archaea, and microbial eukaryotes. Far less is known about microbial eukaryotes in subsurface habitats, albeit several studies have indicated that fungi dominate microbial eukaryotic communities and fungal molecular signatures (of both yeasts and filamentous forms) have been detected in samples as deep as 1740 mbsf. Here, we compare and contrast fungal ribosomal RNA gene signatures and whole community metatranscriptomes present in sediment core samples from 6 and 95 mbsf from Peru Margin site 1229A and from samples from 12 and 345 mbsf from Canterbury Basin site U1352. The metatranscriptome analyses reveal higher relative expression of amino acid and peptide transporters in the less nutrient rich Canterbury Basin sediments compared to the nutrient rich Peru Margin, and higher expression of motility genes in the Peru Margin samples. Higher expression of genes associated with metals transporters and antibiotic resistance and production was detected in Canterbury Basin sediments. A poly-A focused metatranscriptome produced for the Canterbury Basin sample from 345 mbsf provides further evidence for active fungal communities in the subsurface in the form of fungal-associated transcripts for metabolic and cellular processes, cell and membrane functions, and catalytic activities. Fungal communities at comparable depths at the two geographically separated locations appear dominated by distinct taxa. Differences in taxonomic composition and expression of genes associated with particular metabolic activities may be a function of sediment organic content as well as oceanic province. Microscopic analysis of Canterbury Basin sediment samples from 4 and 403 mbsf produced visualizations of septate fungal filaments, branching fungi, conidiogenesis, and spores. These images provide another important line of evidence supporting the occurrence and activity of fungi in the deep subseafloor biosphere. PMID:27375571

Fungal and Prokaryotic Activities in the Marine Subsurface Biosphere at Peru Margin and Canterbury Basin Inferred from RNA-Based Analyses and Microscopy.

PubMed

Pachiadaki, Maria G; Rédou, Vanessa; Beaudoin, David J; Burgaud, Gaëtan; Edgcomb, Virginia P

2016-01-01

The deep sedimentary biosphere, extending 100s of meters below the seafloor harbors unexpected diversity of Bacteria, Archaea, and microbial eukaryotes. Far less is known about microbial eukaryotes in subsurface habitats, albeit several studies have indicated that fungi dominate microbial eukaryotic communities and fungal molecular signatures (of both yeasts and filamentous forms) have been detected in samples as deep as 1740 mbsf. Here, we compare and contrast fungal ribosomal RNA gene signatures and whole community metatranscriptomes present in sediment core samples from 6 and 95 mbsf from Peru Margin site 1229A and from samples from 12 and 345 mbsf from Canterbury Basin site U1352. The metatranscriptome analyses reveal higher relative expression of amino acid and peptide transporters in the less nutrient rich Canterbury Basin sediments compared to the nutrient rich Peru Margin, and higher expression of motility genes in the Peru Margin samples. Higher expression of genes associated with metals transporters and antibiotic resistance and production was detected in Canterbury Basin sediments. A poly-A focused metatranscriptome produced for the Canterbury Basin sample from 345 mbsf provides further evidence for active fungal communities in the subsurface in the form of fungal-associated transcripts for metabolic and cellular processes, cell and membrane functions, and catalytic activities. Fungal communities at comparable depths at the two geographically separated locations appear dominated by distinct taxa. Differences in taxonomic composition and expression of genes associated with particular metabolic activities may be a function of sediment organic content as well as oceanic province. Microscopic analysis of Canterbury Basin sediment samples from 4 and 403 mbsf produced visualizations of septate fungal filaments, branching fungi, conidiogenesis, and spores. These images provide another important line of evidence supporting the occurrence and activity of fungi in the deep subseafloor biosphere.

Microbiological and Geochemical Survey of CO2-Dominated Mofette and Mineral Waters of the Cheb Basin, Czech Republic.

PubMed

Krauze, Patryk; Kämpf, Horst; Horn, Fabian; Liu, Qi; Voropaev, Andrey; Wagner, Dirk; Alawi, Mashal

2017-01-01

The Cheb Basin (NW Bohemia, Czech Republic) is a shallow, neogene intracontinental basin. It is a non-volcanic region which features frequent earthquake swarms and large-scale diffuse degassing of mantle-derived CO 2 at the surface that occurs in the form of CO 2 -rich mineral springs and wet and dry mofettes. So far, the influence of CO 2 degassing onto the microbial communities has been studied for soil environments, but not for aquatic systems. We hypothesized, that deep-trenching CO 2 conduits interconnect the subsurface with the surface. This admixture of deep thermal fluids should be reflected in geochemical parameters and in the microbial community compositions. In the present study four mineral water springs and two wet mofettes were investigated through an interdisciplinary survey. The waters were acidic and differed in terms of organic carbon and anion/cation concentrations. Element geochemical and isotope analyses of fluid components were used to verify the origin of the fluids. Prokaryotic communities were characterized through quantitative PCR and Illumina 16S rRNA gene sequencing. Putative chemolithotrophic, anaerobic and microaerophilic organisms connected to sulfur (e.g., Sulfuricurvum, Sulfurimonas ) and iron (e.g., Gallionella, Sideroxydans ) cycling shaped the core community. Additionally, CO 2 -influenced waters form an ecosystem containing many taxa that are usually found in marine or terrestrial subsurface ecosystems. Multivariate statistics highlighted the influence of environmental parameters such as pH, Fe 2+ concentration and conductivity on species distribution. The hydrochemical and microbiological survey introduces a new perspective on mofettes. Our results support that mofettes are either analogs or rather windows into the deep biosphere and furthermore enable access to deeply buried paleo-sediments.

Microbiological and Geochemical Survey of CO2-Dominated Mofette and Mineral Waters of the Cheb Basin, Czech Republic

PubMed Central

Krauze, Patryk; Kämpf, Horst; Horn, Fabian; Liu, Qi; Voropaev, Andrey; Wagner, Dirk; Alawi, Mashal

2017-01-01

The Cheb Basin (NW Bohemia, Czech Republic) is a shallow, neogene intracontinental basin. It is a non-volcanic region which features frequent earthquake swarms and large-scale diffuse degassing of mantle-derived CO2 at the surface that occurs in the form of CO2-rich mineral springs and wet and dry mofettes. So far, the influence of CO2 degassing onto the microbial communities has been studied for soil environments, but not for aquatic systems. We hypothesized, that deep-trenching CO2 conduits interconnect the subsurface with the surface. This admixture of deep thermal fluids should be reflected in geochemical parameters and in the microbial community compositions. In the present study four mineral water springs and two wet mofettes were investigated through an interdisciplinary survey. The waters were acidic and differed in terms of organic carbon and anion/cation concentrations. Element geochemical and isotope analyses of fluid components were used to verify the origin of the fluids. Prokaryotic communities were characterized through quantitative PCR and Illumina 16S rRNA gene sequencing. Putative chemolithotrophic, anaerobic and microaerophilic organisms connected to sulfur (e.g., Sulfuricurvum, Sulfurimonas) and iron (e.g., Gallionella, Sideroxydans) cycling shaped the core community. Additionally, CO2-influenced waters form an ecosystem containing many taxa that are usually found in marine or terrestrial subsurface ecosystems. Multivariate statistics highlighted the influence of environmental parameters such as pH, Fe2+ concentration and conductivity on species distribution. The hydrochemical and microbiological survey introduces a new perspective on mofettes. Our results support that mofettes are either analogs or rather windows into the deep biosphere and furthermore enable access to deeply buried paleo-sediments. PMID:29321765

Viral activities and life cycles in deep subseafloor sediments.

PubMed

Engelhardt, Tim; Orsi, William D; Jørgensen, Bo Barker

2015-12-01

Viruses are highly abundant in marine subsurface sediments and can even exceed the number of prokaryotes. However, their activity and quantitative impact on microbial populations are still poorly understood. Here, we use gene expression data from published continental margin subseafloor metatranscriptomes to qualitatively assess viral diversity and activity in sediments up to 159 metres below seafloor (mbsf). Mining of the metatranscriptomic data revealed 4651 representative viral homologues (RVHs), representing 2.2% of all metatranscriptome sequence reads, which have close translated homology (average 77%, range 60-97% amino acid identity) to viral proteins. Archaea-infecting RVHs are exclusively detected in the upper 30 mbsf, whereas RVHs for filamentous inoviruses predominate in the deepest sediment layers. RVHs indicative of lysogenic phage-host interactions and lytic activity, notably cell lysis, are detected at all analysed depths and suggest a dynamic virus-host association in the marine deep biosphere studied here. Ongoing lytic viral activity is further indicated by the expression of clustered, regularly interspaced, short palindromic repeat-associated cascade genes involved in cellular defence against viral attacks. The data indicate the activity of viruses in subsurface sediment of the Peruvian margin and suggest that viruses indeed cause cell mortality and may play an important role in the turnover of subseafloor microbial biomass. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

Biofilm formation and potential for iron cycling in serpentinization-influenced groundwater of the Zambales and Coast Range ophiolites.

PubMed

Meyer-Dombard, D'Arcy R; Casar, Caitlin P; Simon, Alexander G; Cardace, Dawn; Schrenk, Matthew O; Arcilla, Carlo A

2018-05-01

Terrestrial serpentinizing systems harbor microbial subsurface life. Passive or active microbially mediated iron transformations at alkaline conditions in deep biosphere serpentinizing ecosystems are understudied. We explore these processes in the Zambales (Philippines) and Coast Range (CA, USA) ophiolites, and associated surface ecosystems by probing the relevance of samples acquired at the surface to in situ, subsurface ecosystems, and the nature of microbe-mineral associations in the subsurface. In this pilot study, we use microcosm experiments and batch culturing directed at iron redox transformations to confirm thermodynamically based predictions that iron transformations may be important in subsurface serpentinizing ecosystems. Biofilms formed on rock cores from the Zambales ophiolite on surface and in-pit associations, confirming that organisms from serpentinizing systems can form biofilms in subsurface environments. Analysis by XPS and FTIR confirmed that enrichment culturing utilizing ferric iron growth substrates produced reduced, magnetic solids containing siderite, spinels, and FeO minerals. Microcosms and enrichment cultures supported organisms whose near relatives participate in iron redox transformations. Further, a potential 'principal' microbial community common to solid samples in serpentinizing systems was identified. These results indicate collectively that iron redox transformations should be more thoroughly and universally considered when assessing the function of terrestrial subsurface ecosystems driven by serpentinization.

Aliphatic hydrocarbons and triterpenes of the Congo deep-sea fan

NASA Astrophysics Data System (ADS)

Méjanelle, Laurence; Rivière, Béatrice; Pinturier, Laurence; Khripounoff, Alexis; Baudin, François; Dachs, Jordi

2017-08-01

Hydrocarbons were analyzed in sediments from the Congo River deep-sea fan, from the Congo River, and in sinking particles collected by sediment traps 40 m above the sediment. Studied sites encompassed three lobes of decreasing age of formation along the canyon: sites A, F and C and a another lobe system, disconnected from the active channel since 4 ka, Site E. Terrestrial long-chain odd n-alkanes were dominant in all sediments of the lobe system. Unsaturated terpenoids sourced by higher plants, such as gammacerene, lupene, ursene and oleanene, were also detected. At site C, characterized by high accumulation rates (10-20 cm yr-1), the organic matter spends less time in the oxic layer than at other sites and high phytadiene concentrations 10-17 μg gOC-1) evidenced recent terrestrial and phytoplanktonic remains reworked in anaerobic conditions. In these sediments, organic carbon-normalized concentrations of terrestrial alkanes and terpenoids were several fold higher than in the lobe sediments with lower accumulation rates (sites A and F), arguing for a more rapid degradation of terrestrial hydrocarbons than bulk organic carbon in the first steps of pre-diagenesis. Ample variations in the contributions of biomarkers from higher plants, ferns, bacteria and angiosperms, indicate an heterogeneous contribution of the soil and vegetation detritus delivered to the Congo lobe sediments. Lower concentrations in terrestrial hydrocarbons at site E, 45 km away from the active canyon, indicated that river particles are still admixed to the dominant marine organic matter. Diploptene and hop-7(21)-ene have a dual origin, from terrestrial and marine microorganisms. Scatter in their relationship to gammacerene argues for a contribution of marine microorganisms, in addition to soils-sourced microorganisms. The close distribution patterns of diploptene, hop-21-ene, hop-7(21)ene and neohop-13(18)-ene is in line with the hypothesis of sequential clay-catalyzed isomerisation of bacterial hopenes. Terrestrial biomarker accumulation fluxes at site C are one order of magnitude higher than vertical pelagic flux, demonstrating the magnitude of the inputs delivered through turbiditic transport in the submarine canyon. Crude oil contamination was evidenced at the disconnected site E (UCM, C21 to C26 tricyclic diterpanes, CPI) and, in smaller amounts, in some sediments from sites A and C. It may be related to marine crude oil extraction and transport. A short-chain mode of alkanes with an even predominance is evidenced in sediments of the lobe complex and likely sources, crude oil, microorganisms and ferns, are discussed.

Young (late Amazonian), near-surface, ground ice features near the equator, Athabasca Valles, Mars

USGS Publications Warehouse

Burr, D.M.; Soare, R.J.; Wan, Bun Tseung J.-M.; Emery, J.P.

2005-01-01

A suite of four feature types in a ???20 km2 area near 10?? N, 204?? W in Athabasca Valles is interpreted to have resulted from near-surface ground ice. These features include mounds, conical forms with rimmed summit depressions, flatter irregularly-shaped forms with raised rims, and polygonal terrain. Based on morphology, size, and analogy to terrestrial ground ice forms, these Athabascan features are interpreted as pingos, collapsing pingos, pingo scars, and thermal contraction polygons, respectively. Thermal Infrared Mapping Spectrometer (THEMIS) data and geological features in the area are consistent with a sedimentary substrate underlying these features. These observations lead us to favor a ground ice interpretation, although we do not rule out volcanic and especially glaciofluvial hypotheses. The hypothesized ground ice that formed the mounds and rimmed features may have been emplaced via the deposition of saturated sediment during flooding; an alternative scenario invokes magmatically cycled groundwater. The ground ice implicit in the hypothesized thermal contraction polygons may have derived either from this flooding/ground water, or from atmospheric water vapor. The lack of obvious flood modification of the mounds and rimmed features indicates that they formed after the most recent flood inundated the area. Analogy with terrestrial pingos suggests that ground ice may be still extant within the positive relief mounds. As the water that flooded down Athabasca Valles emerged via a volcanotectonic fissure from a deep aquifer, any extant pingo ice may contain evidence of a deep subsurface biosphere. ?? 2005 Elsevier Inc. All rights reserved.

Energy transfer in the Congo deep-sea fan: From terrestrially-derived organic matter to chemosynthetic food webs

NASA Astrophysics Data System (ADS)

Pruski, A. M.; Decker, C.; Stetten, E.; Vétion, G.; Martinez, P.; Charlier, K.; Senyarich, C.; Olu, K.

2017-08-01

Large amounts of recent terrestrial organic matter (OM) from the African continent are delivered to the abyssal plain by turbidity currents and accumulate in the Congo deep-sea fan. In the recent lobe complex, large clusters of vesicomyid bivalves are found all along the active channel in areas of reduced sediment. These soft-sediment communities resemble those fuelled by chemoautotrophy in cold-seep settings. The aim of this study was to elucidate feeding strategies in these macrofaunal assemblages as part of a greater effort to understand the link between the inputs of terrestrially-derived OM and the chemosynthetic habitats. The biochemical composition of the sedimentary OM was first analysed in order to evaluate how nutritious the available particulate OM is for the benthic macrofauna. The terrestrial OM is already degraded when it reaches the final depositional area. However, high biopolymeric carbon contents (proteins, carbohydrates and lipids) are found in the channel of the recent lobe complex. In addition, about one to two thirds of the nitrogen can be assigned to peptide-like material. Even if this soil-derived OM is poorly digestible, turbiditic deposits contain such high amounts of organic carbon that there is enough biopolymeric carbon and proteacinous nitrogen to support dense benthic communities that contrast with the usual depauperate abyssal plains. Stable carbon and nitrogen isotopes and fatty acid biomarkers were then used to shed light on the feeding strategies allowing the energy transfer from the terrestrial OM brought by the turbidity currents to the abyssal food web. In the non-reduced sediment, surface detritivorous holothurians and suspension-feeding poriferans rely on detritic OM, thereby depending directly on the turbiditic deposits. The sulphur-oxidising symbiont bearing vesicomyids closely depend on the reprocessing of OM with methane and sulphide as final products. Their carbon and nitrogen isotopic signatures vary greatly among sites and could reflect the intensity of the anaerobic oxidation of methane (AOM) in the sediments. Within the vesicomyid habitats, the heterotrophic fauna exhibits a distinctively light carbon isotopic signature in comparison to the background sediments, clearly indicating the utilisation of chemosynthetically-derived OM. Fatty acid biomarkers further confirm that dorvilleid polychaetes consume aggregates that perform AOM. Terrestrial OM reprocessing by microbial consortium thus ensures its transfer to the benthic food web in the Congo deep-sea fan.

Microbial Life of North Pacific Oceanic Crust

NASA Astrophysics Data System (ADS)

Schumann, G.; Koos, R.; Manz, W.; Reitner, J.

2003-12-01

Information on the microbiology of the deep subsurface is necessary in order to understand the factors controlling the rate and extent of the microbially catalyzed reactions that influence the geophysical properties of these environments. Drilling into 45-Ma oceanic basaltic crust in a deepwater environment during ODP Leg 200 provided a promising opportunity to explore the abundance, diversity and activity of micro-organisms. The combined use of culture-independent molecular phylogenetic analyses and enrichment culture techniques is an advantageous approach in investigating subsurface microbial ecosystems. Enrichment culture methods allow the evaluation of potential activities and functions. Microbiological investigations revealed few aerobic cultivable, in part hitherto unknown, micro-organisms in deep submarine sediments and basaltic lava flows. 16S rDNA sequencing of isolates from sediment revealed the next relatives to be members of the genera Halomonas, Pseudomonas, and Lactobacillus. Within the Pseudomonadaceae the closest relative is Acinetobacter sp., which was isolated from a deep subsurface environment. The next phylogenetical relatives within the Halomonadaceae are bacteria typically isolated from Soda lakes, which are considered as model of early life conditions. Interestingly, not only sediment bacteria could be obtained in pure culture. Aerobic strains could also be successfully isolated from the massive tholeiitic basalt layer at a depth of 76.16 mbsf (46 m below the sediment/basement contact). These particular isolates are gram-positive with low G+C content of DNA, phylogenetically affiliated to the phylum Firmicutes. The closest neighbors are e.g. a marine Bacillus isolated from the Gulf of Mexico and a low G+C gram-positive bacterium, which belongs to the microbial flora in the deepest sea mud of the Mariana Trench, isolated from a depth of 10,897 m. Based on the similarity values, the isolates represent hitherto undescribed species of the deep biosphere. Molecular microbial diversity is currently determined by cloning und comparative 16S rRNA gene analyses. The first results will also be presented. In summary, the low number of isolates, cultivated under aerobic conditions, is in good agreement with the common opinion that most of the bacteria within the deep biosphere are anaerobic. Thus, studies of microbial community structure in solid geological materials are feasible and constitute further evidence that continuing microbiological activity in the challenging exploration of the deep sub-seafloor biosphere environment is absolutely promising.

Microbial metabolisms in a 2.5-km-deep ecosystem created by hydraulic fracturing in shales.

PubMed

Daly, Rebecca A; Borton, Mikayla A; Wilkins, Michael J; Hoyt, David W; Kountz, Duncan J; Wolfe, Richard A; Welch, Susan A; Marcus, Daniel N; Trexler, Ryan V; MacRae, Jean D; Krzycki, Joseph A; Cole, David R; Mouser, Paula J; Wrighton, Kelly C

2016-09-05

Hydraulic fracturing is the industry standard for extracting hydrocarbons from shale formations. Attention has been paid to the economic benefits and environmental impacts of this process, yet the biogeochemical changes induced in the deep subsurface are poorly understood. Recent single-gene investigations revealed that halotolerant microbial communities were enriched after hydraulic fracturing. Here, the reconstruction of 31 unique genomes coupled to metabolite data from the Marcellus and Utica shales revealed that many of the persisting organisms play roles in methylamine cycling, ultimately supporting methanogenesis in the deep biosphere. Fermentation of injected chemical additives also sustains long-term microbial persistence, while thiosulfate reduction could produce sulfide, contributing to reservoir souring and infrastructure corrosion. Extensive links between viruses and microbial hosts demonstrate active viral predation, which may contribute to the release of labile cellular constituents into the extracellular environment. Our analyses show that hydraulic fracturing provides the organismal and chemical inputs for colonization and persistence in the deep terrestrial subsurface.

Microbial metabolisms in a 2.5-km-deep ecosystem created by hydraulic fracturing in shales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daly, Rebecca A.; Borton, Mikayla A.; Wilkins, Michael J.

Hydraulic fracturing is the industry standard for extracting hydrocarbons from shale formations. Attention has been paid to the economic benefits and environmental impacts of this process, yet the biogeochemical changes induced in the deep subsurface are poorly understood. Recent single-gene investigations revealed that halotolerant microbial communities were enriched after hydraulic fracturing. Here the reconstruction of 31 unique genomes coupled to metabolite data from the Marcellus and Utica shales revealed that methylamine cycling supports methanogenesis in the deep biosphere. Fermentation of injected chemical additives also sustains long-term microbial persistence, while sulfide generation from thiosulfate represents a poorly recognized corrosion mechanism inmore » shales. Extensive links between viruses and microbial hosts demonstrate active viral predation, which may contribute to the release of labile cellular constituents into the extracellular environment. Our analyses show that hydraulic fracturing provides the organismal and chemical inputs for colonization and persistence in the deep terrestrial subsurface.« less

Deep subsurface life in Bengal Fan sediments (IODP Exp. 354)

NASA Astrophysics Data System (ADS)

Adhikari, R. R.; Heuer, V. B.; Elvert, M.; Kallmeyer, J.; Kitte, J. A.; Wörmer, L.; Hinrichs, K. U.

2017-12-01

We collected Bengal Fan sediment samples along a 8°N transect during International Ocean Discovery Program Expedition 354 (February - March 2015, Singapore - Colombo, Sri Lanka) to study subseafloor life in this, as yet unstudied, area. Among other biogeochemical parameters, we quantified microbial biomass by analyzing prokaryotic cells using epifluorescence microscopy after detaching cells from the sediment, and bacterial endospores by analyzing the diagnostic biomarker dipicolinic acid (DPA) by detection of fluorescence of the terbium-DPA complex. To gain understanding of total microbial activity, we quantified hydrogen utilization potential of hydrogenase enzymes, which are ubiquitous in subsurface microorganisms, by using a tritium assay. We measured highest cell concentrations of ca. 108 cells g-1 in shallow sediments close to the seafloor. These concentrations are one to two orders of magnitude lower than in most marine continental margin settings [1]. Similar to the global trend [1], cell concentrations decreased with depth according to a power-law function. Endospore concentrations scattered between ca. 105 and 107 cells g-1 sediment at all sites and depths. We could not observe a clear relationship of endospore concentration and sediment depth; instead, it appears to be linked to lithology and total organic carbon content. Bulk Hydrogenase enzyme activity ranged from nmolar to μmolar range of H2 g-1d-1. Similar to previous observations [2], per-cell hydrogen utilization depends on vertical biogeochemical zones, which could be due to the differences in hydrogen utilization requirements/efficiency of the respective metabolic processes such as sulfate reduction, methanogenesis, fermentation etc. Bengal fan is highly dynamic due to channel and levee systems and the sediments are dominated by turbidites, thick sand layers and hemipelagic deposits, which may control biogeochemical zonation. Based on our microbial biomass and activity data, we suggest that the nature, quality and origin of sedimentary material influence the deep subsurface life. [1] Kallmeyer et al., (2012) PNAS 109(40), 16213-16216 [2] Adhikari et al., (2016) Frontiers in Microbiology 7:8

On the Dielectric Properties of the Martian-like Surface Sediments

NASA Technical Reports Server (NTRS)

Heggy, E.; Clifford, S. M.; Morris, R. V.; Paillou, P.; Ruffie, G.

2004-01-01

We have undertaken laboratory electromagnetic characterization of the total set of minerals identified by TES on the Martian surface in order to investigate experimentally the dielectric properties of the sediments covering it in the frequency range from 1 to 30 MHz. Volcanic Rocks with a well defined mineralogy and petrology from potential terrestrial analogues sites have also been included in the study. Our primary objective is to evaluate the range of electrical and magnetic losses that may be encountered by the various Radar sounding and imaging experiments dedicated to map the Martian subsurface searching for underground water. The electromagnetic properties of these Mars-like materials will be presented as a function of various geophysical parameters, such as porosity, bulk density and temperature. The secondary objective, is to locate regions were surface dielectric conditions are suitable for subsurface sounding.

Cultivation Of Deep Subsurface Microbial Communities

NASA Astrophysics Data System (ADS)

Obrzut, Natalia; Casar, Caitlin; Osburn, Magdalena R.

2018-01-01

The potential habitability of surface environments on other planets in our solar system is limited by exposure to extreme radiation and desiccation. In contrast, subsurface environments may offer protection from these stressors and are potential reservoirs for liquid water and energy that support microbial life (Michalski et al., 2013) and are thus of interest to the astrobiology community. The samples used in this project were extracted from the Deep Mine Microbial Observatory (DeMMO) in the former Homestake Mine at depths of 800 to 2000 feet underground (Osburn et al., 2014). Phylogenetic data from these sites indicates the lack of cultured representatives within the community. We used geochemical data to guide media design to cultivate and isolate organisms from the DeMMO communities. Media used for cultivation varied from heterotrophic with oxygen, nitrate or sulfate to autotrophic media with ammonia or ferrous iron. Environmental fluid was used as inoculum in batch cultivation and strains were isolated via serial transfers or dilution to extinction. These methods resulted in isolating aerobic heterotrophs, nitrate reducers, sulfate reducers, ammonia oxidizers, and ferric iron reducers. DNA sequencing of these strains is underway to confirm which species they belong to. This project is part of the NASA Astrobiology Institute Life Underground initiative to detect and characterize subsurface microbial life; by characterizing the intraterrestrials, the life living deep within Earth’s crust, we aim to understand the controls on how and where life survives in subsurface settings. Cultivation of terrestrial deep subsurface microbes will provide insight into the survival mechanisms of intraterrestrials guiding the search for these life forms on other planets.

How to Access and Sample the Deep Subsurface of Mars

NASA Technical Reports Server (NTRS)

Briggs, G.; Blacic, J.; Dreesen, D.; Mockler, T.

2000-01-01

We are developing a technology roadmap to support a series of Mars lander missions aimed at successively deeper and more comprehensive explorations of the Martian subsurface. The proposed mission sequence is outlined. Key to this approach is development of a drilling and sampling technology robust and flexible enough to successfully penetrate the presently unknown subsurface geology and structure. Martian environmental conditions, mission constraints of power and mass and a requirement for a high degree of automation all limit applicability of many proven terrestrial drilling technologies. Planetary protection and bioscience objectives further complicate selection of candidate systems. Nevertheless, recent advances in drilling technologies for the oil & gas, mining, underground utility and other specialty drilling industries convinces us that it will be possible to meet science and operational objectives of Mars subsurface exploration.

Designing a network of critical zone observatories to explore the living skin of the terrestrial Earth

NASA Astrophysics Data System (ADS)

Brantley, Susan L.; McDowell, William H.; Dietrich, William E.; White, Timothy S.; Kumar, Praveen; Anderson, Suzanne P.; Chorover, Jon; Lohse, Kathleen Ann; Bales, Roger C.; Richter, Daniel D.; Grant, Gordon; Gaillardet, Jérôme

2017-12-01

The critical zone (CZ), the dynamic living skin of the Earth, extends from the top of the vegetative canopy through the soil and down to fresh bedrock and the bottom of the groundwater. All humans live in and depend on the CZ. This zone has three co-evolving surfaces: the top of the vegetative canopy, the ground surface, and a deep subsurface below which Earth's materials are unweathered. The network of nine CZ observatories supported by the US National Science Foundation has made advances in three broad areas of CZ research relating to the co-evolving surfaces. First, monitoring has revealed how natural and anthropogenic inputs at the vegetation canopy and ground surface cause subsurface responses in water, regolith structure, minerals, and biotic activity to considerable depths. This response, in turn, impacts aboveground biota and climate. Second, drilling and geophysical imaging now reveal how the deep subsurface of the CZ varies across landscapes, which in turn influences aboveground ecosystems. Third, several new mechanistic models now provide quantitative predictions of the spatial structure of the subsurface of the CZ.Many countries fund critical zone observatories (CZOs) to measure the fluxes of solutes, water, energy, gases, and sediments in the CZ and some relate these observations to the histories of those fluxes recorded in landforms, biota, soils, sediments, and rocks. Each US observatory has succeeded in (i) synthesizing research across disciplines into convergent approaches; (ii) providing long-term measurements to compare across sites; (iii) testing and developing models; (iv) collecting and measuring baseline data for comparison to catastrophic events; (v) stimulating new process-based hypotheses; (vi) catalyzing development of new techniques and instrumentation; (vii) informing the public about the CZ; (viii) mentoring students and teaching about emerging multidisciplinary CZ science; and (ix) discovering new insights about the CZ. Many of these activities can only be accomplished with observatories. Here we review the CZO enterprise in the United States and identify how such observatories could operate in the future as a network designed to generate critical scientific insights. Specifically, we recognize the need for the network to study network-level questions, expand the environments under investigation, accommodate both hypothesis testing and monitoring, and involve more stakeholders. We propose a driving question for future CZ science and a hubs-and-campaigns model to address that question and target the CZ as one unit. Only with such integrative efforts will we learn to steward the life-sustaining critical zone now and into the future.

New Support for Hypotheses of an Ancient Ocean on Mars

NASA Technical Reports Server (NTRS)

Oehler, Dorothy Z.; Allen, Carlton C.

2013-01-01

A new analog for the giant polygons in the Chryse-Acidalia area suggests that those features may have formed in a major body of water - likely a Late Hesperian to Early Amazonian ocean. This analog -terrestrial polygons in subsea, passive margin basins derives from 3D seismic data that show similar-scale, polygonal fault systems in the subsurface of more than 50 terrestrial offshore basins. The terrestrial and martian polygons share similar sizes, basin-wide distributions, tectonic settings, and association with expected fine-grained sediments. Late Hesperian deposition from outflow floods may have triggered formation of these polygons, by providing thick, rapidly-deposited, fine-grained sediments necessary for polygonal fracturing. The restriction of densely occurring polygons to elevations below approx. -4000 m to -4100 m supports inferences that a body of water controlled their formation. Those same elevations appear to restrict occurrence of polygons in Utopia Planitia, suggesting that this analog may apply also to Utopia and that similar processes may have occurred across the martian lowlands.

Polycyclic aromatic hydrocarbons (PAHs) in the water column and sediment core of Deep Bay, South China

NASA Astrophysics Data System (ADS)

Qiu, Yao-Wen; Zhang, Gan; Liu, Guo-Qing; Guo, Ling-Li; Li, Xiang-Dong; Wai, Onyx

2009-06-01

The levels of 15 polycyclic aromatic hydrocarbons (PAHs) were determined in seawater, suspended particulate matter (SPM), surface sediment and core sediment samples of Deep Bay, South China. The average concentrations Σ 15PAHs were 69.4 ± 24.7 ng l -1 in seawater, 429.1 ± 231.8 ng g -1 in SPM, and 353.8 ± 128.1 ng g -1 dry weight in surface sediment, respectively. Higher PAH concentrations were observed in SPM than in surface sediment. Temporal trend of PAH concentrations in core sediment generally increased from 1948 to 2004, with higher concentrations in top than in sub-surface, implying a stronger recent input of PAHs owing to the rapid economic development in Shenzhen. Compared with historical data, the PAH levels in surface sediment has increased, and this was further confirmed by the increasing trend of PAHs in the core sediment. Phenanthrene, fluoranthene and pyrene dominated in the PAH composition pattern profiles in the Bay. Compositional pattern analysis suggested that PAHs in the Deep Bay were derived from both pyrogenic and petrogenic sources, and diesel oil leakage, river runoff and air deposition may serve as important pathways for PAHs input to the Bay. Significant positive correlations between partition coefficient in surface sediment to that in water ( KOC) of PAH and their octanol/water partition coefficients ( KOW) were observed, suggesting that KOC of PAHs in sediment/water of Deep Bay may be predicted by the corresponding KOW.

Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock

DOE PAGES

Bagnoud, Alexandre; Chourey, Karuna; Hettich, Robert L.; ...

2016-10-14

A significant fraction (~ 20%) of microbial life is found in the terrestrial deep subsurface, yet the metabolic processes extant in those environments are poorly understood. Here we show that H 2, injected into the Opalinus Clay formation in a borehole located 300 meters below the surface, fuels a community of microorganisms with interconnected metabolisms. Metagenomic binning and metaproteomic analysis reveal a complete carbon cycle, driven by autotrophic hydrogen oxidizers. Dead biomass from these organisms is a substrate for a fermenting bacterium that produces acetate as a product. In turn, complete oxidizer heterotrophic sulfate- reducing bacteria utilize acetate and oxidizemore » it to CO 2, closing the cycle. This metabolic reconstruction sheds light onto a hydrogen-driven carbon cycle, and a sunlight-independent ecosystem in the deep subsurface.« less

Microbial metagenomes from three aquifers in the Fennoscandian shield terrestrial deep biosphere reveal metabolic partitioning among populations

PubMed Central

Wu, Xiaofen; Holmfeldt, Karin; Hubalek, Valerie; Lundin, Daniel; Åström, Mats; Bertilsson, Stefan; Dopson, Mark

2016-01-01

Microorganisms in the terrestrial deep biosphere host up to 20% of the earth's biomass and are suggested to be sustained by the gases hydrogen and carbon dioxide. A metagenome analysis of three deep subsurface water types of contrasting age (from <20 to several thousand years) and depth (171 to 448 m) revealed phylogenetically distinct microbial community subsets that either passed or were retained by a 0.22 μm filter. Such cells of <0.22 μm would have been overlooked in previous studies relying on membrane capture. Metagenomes from the three water types were used for reconstruction of 69 distinct microbial genomes, each with >86% coverage. The populations were dominated by Proteobacteria, Candidate divisions, unclassified archaea and unclassified bacteria. The estimated genome sizes of the <0.22 μm populations were generally smaller than their phylogenetically closest relatives, suggesting that small dimensions along with a reduced genome size may be adaptations to oligotrophy. Shallow ‘modern marine' water showed community members with a predominantly heterotrophic lifestyle. In contrast, the deeper, ‘old saline' water adhered more closely to the current paradigm of a hydrogen-driven deep biosphere. The data were finally used to create a combined metabolic model of the deep terrestrial biosphere microbial community. PMID:26484735

Microbial metagenomes from three aquifers in the Fennoscandian shield terrestrial deep biosphere reveal metabolic partitioning among populations.

PubMed

Wu, Xiaofen; Holmfeldt, Karin; Hubalek, Valerie; Lundin, Daniel; Åström, Mats; Bertilsson, Stefan; Dopson, Mark

2016-05-01

Microorganisms in the terrestrial deep biosphere host up to 20% of the earth's biomass and are suggested to be sustained by the gases hydrogen and carbon dioxide. A metagenome analysis of three deep subsurface water types of contrasting age (from <20 to several thousand years) and depth (171 to 448 m) revealed phylogenetically distinct microbial community subsets that either passed or were retained by a 0.22 μm filter. Such cells of <0.22 μm would have been overlooked in previous studies relying on membrane capture. Metagenomes from the three water types were used for reconstruction of 69 distinct microbial genomes, each with >86% coverage. The populations were dominated by Proteobacteria, Candidate divisions, unclassified archaea and unclassified bacteria. The estimated genome sizes of the <0.22 μm populations were generally smaller than their phylogenetically closest relatives, suggesting that small dimensions along with a reduced genome size may be adaptations to oligotrophy. Shallow 'modern marine' water showed community members with a predominantly heterotrophic lifestyle. In contrast, the deeper, 'old saline' water adhered more closely to the current paradigm of a hydrogen-driven deep biosphere. The data were finally used to create a combined metabolic model of the deep terrestrial biosphere microbial community.

Carbon Cycling and Storage in Mangrove Forests

NASA Astrophysics Data System (ADS)

Alongi, Daniel M.

2014-01-01

Mangroves are ecologically and economically important forests of the tropics. They are highly productive ecosystems with rates of primary production equal to those of tropical humid evergreen forests and coral reefs. Although mangroves occupy only 0.5% of the global coastal area, they contribute 10-15% (24 Tg C y-1) to coastal sediment carbon storage and export 10-11% of the particulate terrestrial carbon to the ocean. Their disproportionate contribution to carbon sequestration is now perceived as a means for conservation and restoration and a way to help ameliorate greenhouse gas emissions. Of immediate concern are potential carbon losses to deforestation (90-970 Tg C y-1) that are greater than these ecosystems' rates of carbon storage. Large reservoirs of dissolved inorganic carbon in deep soils, pumped via subsurface pathways to adjacent waterways, are a large loss of carbon, at a potential rate up to 40% of annual primary production. Patterns of carbon allocation and rates of carbon flux in mangrove forests are nearly identical to those of other tropical forests.

Carbon cycling and storage in mangrove forests.

PubMed

Alongi, Daniel M

2014-01-01

Mangroves are ecologically and economically important forests of the tropics. They are highly productive ecosystems with rates of primary production equal to those of tropical humid evergreen forests and coral reefs. Although mangroves occupy only 0.5% of the global coastal area, they contribute 10-15% (24 Tg C y(-1)) to coastal sediment carbon storage and export 10-11% of the particulate terrestrial carbon to the ocean. Their disproportionate contribution to carbon sequestration is now perceived as a means for conservation and restoration and a way to help ameliorate greenhouse gas emissions. Of immediate concern are potential carbon losses to deforestation (90-970 Tg C y(-1)) that are greater than these ecosystems' rates of carbon storage. Large reservoirs of dissolved inorganic carbon in deep soils, pumped via subsurface pathways to adjacent waterways, are a large loss of carbon, at a potential rate up to 40% of annual primary production. Patterns of carbon allocation and rates of carbon flux in mangrove forests are nearly identical to those of other tropical forests.

Microbes of deep marine sediments as viewed by metagenomics

NASA Astrophysics Data System (ADS)

Biddle, J.

2015-12-01

Ten years after the first deep marine sediment metagenome was produced, questions still exist about the nucleic acid sequences we have retrieved. Current data sets, including the Peru Margin, Costa Rica Margin and Iberian Margin show that consistently, data forms larger assemblies at depth due to the reduced complexity of the microbial community. But are these organisms active or preserved? At SMTZs, a change in the assembly statistics is noted, as well as an increase in cell counts, suggesting that cells are truly active. As depth increases, genome sizes are consistently large, suggesting that much like soil microbes, sedimentary microbes may maintain a larger reportorie of genomic potential. Functional changes are seen with depth, but at many sites are not correlated to specific geochemistries. Individual genomes show changes with depth, which raises interesting questions on how the subsurface is settled and maintained. The subsurface does have a distinct genomic signature, including unusual microbial groups, which we are now able to analyze for total genomic content.

Preliminary Results of a Modern Watershed Study from Lake Junín, Peru: Biomarker Assemblages in Terrestrial and Aquatic Plants and Surface Sediments

NASA Astrophysics Data System (ADS)

Woods, A.; Werne, J. P.; Rodbell, D. T.; Abbott, M. B.

2016-12-01

Lake Junín is a large, evaporatively-enriched lake in the central Peruvian Andes that is ideally situated to record variability in the South American Summer Monsoon, and sediment cores recovered by the Lake Junín Deep Drilling Project in 2015 span several glacial/interglacial cycles. Compound-specific stable hydrogen isotopes from leaf waxes offer the potential to reconstruct changes in monsoon strength and evapotranspiration for the entire sediment record, and can be compared with the carbonate-derived oxygen isotope record that is preserved only during interglacials. To characterize the modern proxy system, leaf samples were collected from terrestrial and aquatic species that are representative of the vegetation in the watershed. The compound distributions, concentrations, and D/H ratios of n-alkanes and n-alkanoic acids from plants and surface sediments were analyzed to develop site-specific calibrations of both terrestrial and aquatic isotopic signals, for application to downcore biomarker analyses.

Active fungi amidst a marine subsurface RNA paleome

NASA Astrophysics Data System (ADS)

Orsi, W.; Biddle, J.; Edgcomb, V.

2012-12-01

The deep marine subsurface is a vast habitat for microbial life where cells may live on geologic timescales. Since extracellular DNA in sediments may be preserved on long timescales, ribosomal RNA (rRNA) is suggested to be a proxy for the active fraction of a microbial community in the subsurface. During an investigation of eukaryotic 18S rRNA signatures by amplicon pyrosequencing, metazoan, plant, and diatom rRNA signatures were recovered from marine sediments up to 2.7 million years old, suggesting that rRNA may be much more stable than previously considered in the marine subsurface. This finding confirms the concept of a paleome, extending it to include rRNA. Within the same dataset, unique profiles of fungi were found across a range of marine subsurface provinces exhibiting statistically significant correlations with total organic carbon (TOC), sulfide, and dissolved inorganic carbon (DIC). Sequences from metazoans, plants and diatoms showed different correlation patterns, consistent with a depth-controlled paleome. The fungal correlations with geochemistry allow the inference that some fungi are active and adapted for survival in the marine subsurface. A metatranscriptomic analysis of fungal derived mRNA confirms that fungi are metabolically active and utilize a range of organic and inorganic substrates in the marine subsurface.

Tackling the Challenge of Deep Vadose Zone Remediation at the Hanford Site

NASA Astrophysics Data System (ADS)

Morse, J. G.; Wellman, D. M.; Gephart, R.

2010-12-01

The Central Plateau of the Hanford Site in Washington State contains some 800 waste disposal sites where 1.7 trillion liters of contaminated water was once discharged into the subsurface. Most of these sites received liquids from the chemical reprocessing of spent uranium fuel to recover plutonium. In addition, 67 single shell tanks have leaked or are suspected to have leaked 3.8 million liters of high alkali and aluminate rich cesium-contaminated liquids into the sediment. Today, this inventory of subsurface contamination contains an estimated 550,000 curies of radioactivity and 150 million kg (165,000 tons) of metals and hazardous chemicals. Radionuclides range from mobile 99Tc to more immobilized 137Cs, 241Am, uranium, and plutonium. A significant fraction of these contaminants likely remain within the deep vadose zone. Plumes of groundwater containing tritium, nitrate, 129I and other contaminants have migrated through the vadose zone and now extend outward from the Central Plateau to the Columbia River. During most of Hanford Site history, subsurface studies focused on groundwater monitoring and characterization to support waste management decisions. Deep vadose zone studies were not a priority because waste practices relied upon that zone to buffer contaminant releases into the underlying aquifer. Remediation of the deep vadose zone is now central to Hanford Site cleanup because these sediments can provide an ongoing source of contamination to the aquifer and therefore to the Columbia River. However, characterization and remediation of the deep vadose zone pose some unique challenges. These include sediment thickness; contaminant depth; coupled geohydrologic, geochemical, and microbial processes controlling contaminant spread; limited availability and effectiveness of traditional characterization tools and cleanup remedies; and predicting contaminant behavior and remediation performance over long time periods and across molecular to field scales. The U.S Department of Energy recognizes these challenges and is committed to a sustained, focused effort of continuing to apply existing technologies where feasible while investing and developing in new innovative, field-demonstrated capabilities supporting longer-term basic and applied research to establish the technical underpinning for solving intractable deep vadose zone problems and implementing final remedies. This approach will rely upon Multi-Project Teams focusing on coordinated projects across multiple DOE offices, programs, and site contractors plus the facilitation of basic and applied research investments through implementing a Deep Vadose Zone Applied Field Research Center and other scientific studies.

Comparative metagenomics of bathypelagic plankton and bottom sediment from the Sea of Marmara

PubMed Central

Quaiser, Achim; Zivanovic, Yvan; Moreira, David; López-García, Purificación

2011-01-01

To extend comparative metagenomic analyses of the deep-sea, we produced metagenomic data by direct 454 pyrosequencing from bathypelagic plankton (1000 m depth) and bottom sediment of the Sea of Marmara, the gateway between the Eastern Mediterranean and the Black Seas. Data from small subunit ribosomal RNA (SSU rRNA) gene libraries and direct pyrosequencing of the same samples indicated that Gamma- and Alpha-proteobacteria, followed by Bacteroidetes, dominated the bacterial fraction in Marmara deep-sea plankton, whereas Planctomycetes, Delta- and Gamma-proteobacteria were the most abundant groups in high bacterial-diversity sediment. Group I Crenarchaeota/Thaumarchaeota dominated the archaeal plankton fraction, although group II and III Euryarchaeota were also present. Eukaryotes were highly diverse in SSU rRNA gene libraries, with group I (Duboscquellida) and II (Syndiniales) alveolates and Radiozoa dominating plankton, and Opisthokonta and Alveolates, sediment. However, eukaryotic sequences were scarce in pyrosequence data. Archaeal amo genes were abundant in plankton, suggesting that Marmara planktonic Thaumarchaeota are ammonia oxidizers. Genes involved in sulfate reduction, carbon monoxide oxidation, anammox and sulfatases were over-represented in sediment. Genome recruitment analyses showed that Alteromonas macleodii ‘surface ecotype', Pelagibacter ubique and Nitrosopumilus maritimus were highly represented in 1000 m-deep plankton. A comparative analysis of Marmara metagenomes with ALOHA deep-sea and surface plankton, whale carcasses, Peru subsurface sediment and soil metagenomes clustered deep-sea Marmara plankton with deep-ALOHA plankton and whale carcasses, likely because of the suboxic conditions in the deep Marmara water column. The Marmara sediment clustered with the soil metagenome, highlighting the common ecological role of both types of microbial communities in the degradation of organic matter and the completion of biogeochemical cycles. PMID:20668488

Prevalence of the Chloroflexi-Related SAR202 Bacterioplankton Cluster throughout the Mesopelagic Zone and Deep Ocean†

PubMed Central

Morris, R. M.; Rappé, M. S.; Urbach, E.; Connon, S. A.; Giovannoni, S. J.

2004-01-01

Since their initial discovery in samples from the north Atlantic Ocean, 16S rRNA genes related to the environmental gene clone cluster known as SAR202 have been recovered from pelagic freshwater, marine sediment, soil, and deep subsurface terrestrial environments. Together, these clones form a major, monophyletic subgroup of the phylum Chloroflexi. While members of this diverse group are consistently identified in the marine environment, there are currently no cultured representatives, and very little is known about their distribution or abundance in the world's oceans. In this study, published and newly identified SAR202-related 16S rRNA gene sequences were used to further resolve the phylogeny of this cluster and to design taxon-specific oligonucleotide probes for fluorescence in situ hybridization. Direct cell counts from the Bermuda Atlantic time series study site in the north Atlantic Ocean, the Hawaii ocean time series site in the central Pacific Ocean, and along the Newport hydroline in eastern Pacific coastal waters showed that SAR202 cluster cells were most abundant below the deep chlorophyll maximum and that they persisted to 3,600 m in the Atlantic Ocean and to 4,000 m in the Pacific Ocean, the deepest samples used in this study. On average, members of the SAR202 group accounted for 10.2% (±5.7%) of all DNA-containing bacterioplankton between 500 and 4,000 m. PMID:15128540

Significant contribution of Archaea to extant biomass in marine subsurface sediments.

PubMed

Lipp, Julius S; Morono, Yuki; Inagaki, Fumio; Hinrichs, Kai-Uwe

2008-08-21

Deep drilling into the marine sea floor has uncovered a vast sedimentary ecosystem of microbial cells. Extrapolation of direct counts of stained microbial cells to the total volume of habitable marine subsurface sediments suggests that between 56 Pg (ref. 1) and 303 Pg (ref. 3) of cellular carbon could be stored in this largely unexplored habitat. From recent studies using various culture-independent techniques, no clear picture has yet emerged as to whether Archaea or Bacteria are more abundant in this extensive ecosystem. Here we show that in subsurface sediments buried deeper than 1 m in a wide range of oceanographic settings at least 87% of intact polar membrane lipids, biomarkers for the presence of live cells, are attributable to archaeal membranes, suggesting that Archaea constitute a major fraction of the biomass. Results obtained from modified quantitative polymerase chain reaction and slot-blot hybridization protocols support the lipid-based evidence and indicate that these techniques have previously underestimated archaeal biomass. The lipid concentrations are proportional to those of total organic carbon. On the basis of this relationship, we derived an independent estimate of amounts of cellular carbon in the global marine subsurface biosphere. Our estimate of 90 Pg of cellular carbon is consistent, within an order of magnitude, with previous estimates, and underscores the importance of marine subsurface habitats for global biomass budgets.

Cultivation and diversity of fungi buried in the Baltic Sea sediments

NASA Astrophysics Data System (ADS)

Xiao, N.

2015-12-01

@font-face { "ＭＳ 明朝"; }@font-face { "Century"; }@font-face { "Century"; }@font-face { "@ＭＳ 明朝"; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0mm 0mm 0.0001pt; text-align: justify; font-size: 12pt; ; }.MsoChpDefault { ; }div.WordSection1 { page: WordSection1; } Studies on molecular biological and cultivation have been done for the prokaryotic microbial community in the deep biosphere. Compare to the prokaryotic community, few attempts have been done for eukaryotic microbial community. Here we report the study on fungi buried in deep-subsurface sediments by approaches of both cultivation and molecular diversity survey. Cultivation targeting fungi has been done using a sequential sediment samples obtained from the Baltic Sea, Landsort Deep site during the IODP expedition 347. 6 culture media with different nutrition and salt concentration have been tried for the fungi cultivation. 50 isolates of fungi were obtained from the sediment samples. The surface sediments showed richness of fungi strains but not for the deep sediments. Internal Transcribed Spacer (ITS) regions of RNA genes were amplified and for the identification of the isolates. The isolates were classified to 11 different genera. Pseudeurotium bakeri was the dominant strain throughout the glacial and interglacial sediments. We also found different representative fungal strains from glacial and interglacial sediments, suggesting the cultivated strains are buried from different sources. The survey of fungal diversity was done by sequencing the 18S RNA genes in the total DNA extracted from selected sediment samples. Fungi community showed different cluster in the glacial and interglacial sediments.Our results revealed the presence and activity of fungi in the deep biosphere of the Baltic sea and provided evidence of fungal community response to the climate change.

How Connecting Sediment Transport Between Environments Solves First-Order Questions Regarding Construction of the Land- and Seascape Recorded by the Permian Brushy Canyon Fm., West Texas, USA

NASA Astrophysics Data System (ADS)

Mohrig, D. C.; Ustipak, K.

2016-12-01

Exposures in the Guadalupe and Delaware mountains together with well logs and core from the Delaware Basin capture a system-wide picture of the stratigraphy defining the terrestrial, shallow marine, basin slope and basin floor environments associated with the Permian Brushy Canyon Formation. Patterns of erosion and styles of deposition characterizing any one of these environments cannot be fully understood without explicit consideration of sediment transport in the adjacent environments. Properties of an inherited basin margin and slope are particularly important to unraveling the transport histories in the linked terrestrial - to - deep marine environments defining the Brushy Canyon Fm. A one-dimensional turbidity current model will be used to show that the inherited submarine slope of about six degrees is steep enough that all sand-transporting currents are erosional down its length. This slope segment detaches the terrestrial and shallow marine environments from the deeper marine environments and decreases the potential for sediment accumulation in the former. All sediment transported to the brink of the basin slope is efficiently moved to deeper water, promoting a tendency for very little sediment to be preserved in the terrestrial environment; a property of the Brushy Canyon system that has spurred on considerable debate and speculation amongst geoscientists studying the formation. The steep inherited slope and its ability to generate erosional sandy turbidity currents also provides an explanation for the high relative fraction of thin-bedded, mud-rich deposits that are present in the most proximal deep marine setting. Again, a one-dimensional turbidity current model is used to show that only very dilute, muddy currents are expected to accumulate in significant quantity at this position in the long profile of the system. Coarser sediment load is confined to and efficiently transported through erosionally based channels onto the basin floor. Finally, the observed spatial trends in sediment erosion over the proximal 20 - 30 km of the basin floor and net sedimentation out to distances approaching 160 km from the shelf edge will be explored and further quantified using the one-dimensional numerical model for turbidity currents.

Physical and chemical controls on habitats for life in the deep subsurface beneath continents and ice

PubMed Central

Parnell, John; McMahon, Sean

2016-01-01

The distribution of life in the continental subsurface is likely controlled by a range of physical and chemical factors. The fundamental requirements are for space to live, carbon for biomass and energy for metabolic activity. These are inter-related, such that adequate permeability is required to maintain a supply of nutrients, and facies interfaces invite colonization by juxtaposing porous habitats with nutrient-rich mudrocks. Viable communities extend to several kilometres depth, diminishing downwards with decreasing porosity. Carbon is contributed by recycling of organic matter originally fixed by photosynthesis, and chemoautotrophy using crustal carbon dioxide and methane. In the shallow crust, the recycled component predominates, as processed kerogen or hydrocarbons, but abiotic carbon sources may be significant in deeper, metamorphosed crust. Hydrogen to fuel chemosynthesis is available from radiolysis, mechanical deformation and mineral alteration. Activity in the subcontinental deep biosphere can be traced through the geological record back to the Precambrian. Before the colonization of the Earth's surface by land plants, a geologically recent event, subsurface life probably dominated the planet's biomass. In regions of thick ice sheets the base of the ice sheet, where liquid water is stable and a sediment layer is created by glacial erosion, can be regarded as a deep biosphere habitat. This environment may be rich in dissolved organic carbon and nutrients accumulated from dissolving ice, and from weathering of the bedrock and the sediment layer. PMID:26667907

Quantifying microbial activity in deep subsurface sediments using a tritium based hydrognease enzyme assay

NASA Astrophysics Data System (ADS)

Adhikari, R.; Nickel, J.; Kallmeyer, J.

2012-12-01

Microbial life is widespread in Earth's subsurface and estimated to represent a significant fraction of Earth's total living biomass. However, very little is known about subsurface microbial activity and its fundamental role in biogeochemical cycles of carbon and other biologically important elements. Hydrogen is one of the most important elements in subsurface anaerobic microbial metabolism. Heterotrophic and chemoautotrophic microorganisms use hydrogen in their metabolic pathways. They either consume or produce protons for ATP synthesis. Hydrogenase (H2ase) is a ubiquitous intracellular enzyme that catalyzes the interconversion of molecular hydrogen and/or water into protons and electrons. The protons are used for the synthesis of ATP, thereby coupling energy generating metabolic processes to electron acceptors such as CO2 or sulfate. H2ase enzyme targets a key metabolic compound in cellular metabolism therefore the assay can be used as a measure for total microbial activity without the need to identify any specific metabolic process. Using the highly sensitive tritium assay we measured H2ase enzyme activity in the organic-rich sediments of Lake Van, a saline, alkaline lake in eastern Turkey, in marine sediments of the Barents Sea and in deep subseafloor sediments from the Nankai Trough. H2ase activity could be quantified at all depths of all sites but the activity distribution varied widely with depth and between sites. At the Lake Van sites H2ase activity ranged from ca. 20 mmol H2 cm-3d-1 close to the sediment-water interface to 0.5 mmol H2 cm-3d-1 at a depth of 0.8 m. In samples from the Barents Sea H2ase activity ranged between 0.1 to 2.5 mmol H2 cm-3d-1 down to a depth of 1.60 m. At all sites the sulfate reduction rate profile followed the upper part of the H2ase activity profile until sulfate reduction reached the minimum detection limit (ca. 10 pmol cm-3d-1). H2ase activity could still be quantified after the decline of sulfate reduction, indicating that other microbial processes are becoming quantitatively more important. Similarly, H2ase activity could be quantified at greater depths (ca. 400 mbsf) in Nankai Trough sediments. Nankai Trough is one of the world's most geologically active accretionary wedges, where the Philippine Plate is subducting under the southwest of Japan. Due to the transient faulting, huge amounts of energy are liberated that enhance chemical transformations of organic and inorganic matter. An increase in H2ase activity could be observed at greater depth, which suggests that microbial activity is stimulated by the fault activity. Current techniques for the quantification of microbial activity in deep sediments have already reached their physical and technical limits and-in many cases- are still not sensitive enough to quantify extremely low rates of microbial activity. Additional to the quantification of specific processes, estimates of total microbial activity will provide valuable information on energy flux and microbial metabolism in the subsurface biosphere and other low-energy environments as well as help identifying hotspots of microbial activity. The tritium H2ase assay has a potential to become a valuable tool to measure total subsurface microbial activity.

The Importance of Subsurface Production for Carbon Export - Evidence from Past Oceans

NASA Astrophysics Data System (ADS)

Kemp, A. E. S.

2016-02-01

The maxim of the geological concept of uniformitarianism is "the present is the key to the past", but in the context of our temporally and spatially minimal observational record of modern ocean biogeochemical processes, ancient ocean sediments may provide critical evidence of the key species involved in carbon flux. Specifically, laminated marine sediments that preserve the seasonal flux cycle represent "palaeo-sediment traps" that vastly expand our knowledge of the operations of the marine biological carbon pump. Several key subsurface-dwelling diatom taxa, hitherto thought to be biogeochemically insignificant, are dominant components of ancient marine sediments. For example, the sapropels and equivalent horizons that have accumulated in the Mediterranean over the past 5 million years, contain abundant rhizosolenid and hemiaulid diatoms. These deposits contain the highest concentrations of organic carbon and there is extensive evidence that this was produced by subsurface production in a deep chlorophyll maximum. The highly stratified conditions that led to this subsurface production and carbon flux are in contrast to prevailing views that have held upwelling systems as those with the highest potential for export in the global ocean. Similarly, studies of ancient "greenhouse" periods such as the Cretaceous, with highly stratified oceans and which are potential analogues for future climate change, show evidence for extensive subsurface production. Together with emerging evidence from stratified regions of the modern ocean, such as the subtropical gyres, insights from these ancient oceans suggest that a reappraisal is required of current views on key phytoplankton producers and their role the operation of the marine biological carbon pump.

Diversity and Biogeography of Bathyal and Abyssal Seafloor Bacteria

PubMed Central

Bienhold, Christina; Zinger, Lucie; Boetius, Antje; Ramette, Alban

2016-01-01

The deep ocean floor covers more than 60% of the Earth’s surface, and hosts diverse bacterial communities with important functions in carbon and nutrient cycles. The identification of key bacterial members remains a challenge and their patterns of distribution in seafloor sediment yet remain poorly described. Previous studies were either regionally restricted or included few deep-sea sediments, and did not specifically test biogeographic patterns across the vast oligotrophic bathyal and abyssal seafloor. Here we define the composition of this deep seafloor microbiome by describing those bacterial operational taxonomic units (OTU) that are specifically associated with deep-sea surface sediments at water depths ranging from 1000–5300 m. We show that the microbiome of the surface seafloor is distinct from the subsurface seafloor. The cosmopolitan bacterial OTU were affiliated with the clades JTB255 (class Gammaproteobacteria, order Xanthomonadales) and OM1 (Actinobacteria, order Acidimicrobiales), comprising 21% and 7% of their respective clades, and about 1% of all sequences in the study. Overall, few sequence-abundant bacterial types were globally dispersed and displayed positive range-abundance relationships. Most bacterial populations were rare and exhibited a high degree of endemism, explaining the substantial differences in community composition observed over large spatial scales. Despite the relative physicochemical uniformity of deep-sea sediments, we identified indicators of productivity regimes, especially sediment organic matter content, as factors significantly associated with changes in bacterial community structure across the globe. PMID:26814838

Tracing the source of sedimentary organic carbon in the Loess Plateau of China: An integrated elemental ratio, stable carbon signatures, and radioactive isotopes approach.

PubMed

Liu, Chun; Dong, Yuting; Li, Zhongwu; Chang, Xiaofeng; Nie, Xiaodong; Liu, Lin; Xiao, Haibing; Bashir, Hassan

2017-02-01

Soil erosion, which will induce the redistribution of soil and associated soil organic carbon (SOC) on the Earth's surface, is of critically importance for biogeochemical cycling of essential elements and terrestrial carbon sequestration. Despite the importance of soil erosion, surprisingly few studies have evaluated the sources of eroded carbon (C). This study used natural abundance levels of the stable isotope signature ( 13 C) and radioactive isotopes ( 137 Cs and 210 Pb ex ), along with elements ratio (C/N) based on a two end member mixing model to qualitatively and quantitatively identify the sources of sedimentary OC retained by check dam in the Qiaozigou small watershed in the Loess Plateau, China. Sediment profiles (0-200 cm) captured at natural depositional area of the basin was compared to possible source materials, which included: superficial Loess mineral soils (0-20 cm) from three land use types [i.e., grassland (Medicago sativa), forestland (Robinia pseudoacacia.), shrubland (Prunus sibirica), and gully land (Loess parent material.)]. The results demonstrated that SOC in sediments showed significantly negative correlation with pH (P < 0.01), and positive correlation with soil water content (SWC) (P < 0.05). The sedimentary OC was not derived from grasslands or gullies. Forestland and shrubland were two main sources of eroded organic carbon within the surface sediment (0-60 cm deep), except for that in the 20-40 cm soil layer. Radionuclides analyses also implied that the surface sediments retained by check-dams mainly originated from soils of forestland and shrubland. Results of the two end-member mixing model demonstrated that more than 50% SOC (mean probability estimate (MPE) 50.13% via 13 C and 60.53% via C/N) in surface sediment (0-20 cm deep) derived from forestland, whereas subsurface sedimentary SOC (20-200 cm) mainly resulted from shrubland (MPE > 50%). Although uncertainties on the sources of SOC in deep soils exist, the soil organic δ 13 C and C/N is still an effective indicator for sources of sedimentary organic carbon in the deposition zone in the short term (<10 years). Copyright © 2016 Elsevier Ltd. All rights reserved.

Phylogenetic and enzymatic diversity of deep subseafloor aerobic microorganisms in organics- and methane-rich sediments off Shimokita Peninsula.

PubMed

Kobayashi, Tohru; Koide, Osamu; Mori, Kozue; Shimamura, Shigeru; Matsuura, Takae; Miura, Takeshi; Takaki, Yoshihiro; Morono, Yuki; Nunoura, Takuro; Imachi, Hiroyuki; Inagaki, Fumio; Takai, Ken; Horikoshi, Koki

2008-07-01

"A meta-enzyme approach" is proposed as an ecological enzymatic method to explore the potential functions of microbial communities in extreme environments such as the deep marine subsurface. We evaluated a variety of extra-cellular enzyme activities of sediment slurries and isolates from a deep subseafloor sediment core. Using the new deep-sea drilling vessel "Chikyu", we obtained 365 m of core sediments that contained approximately 2% organic matter and considerable amounts of methane from offshore the Shimokita Peninsula in Japan at a water depth of 1,180 m. In the extra-sediment fraction of the slurry samples, phosphatase, esterase, and catalase activities were detected consistently throughout the core sediments down to the deepest slurry sample from 342.5 m below seafloor (mbsf). Detectable enzyme activities predicted the existence of a sizable population of viable aerobic microorganisms even in deep subseafloor habitats. The subsequent quantitative cultivation using solid media represented remarkably high numbers of aerobic, heterotrophic microbial populations (e.g., maximally 4.4x10(7) cells cm(-3) at 342.5 mbsf). Analysis of 16S rRNA gene sequences revealed that the predominant cultivated microbial components were affiliated with the genera Bacillus, Shewanella, Pseudoalteromonas, Halomonas, Pseudomonas, Paracoccus, Rhodococcus, Microbacterium, and Flexibacteracea. Many of the predominant and scarce isolates produced a variety of extra-cellular enzymes such as proteases, amylases, lipases, chitinases, phosphatases, and deoxyribonucleases. Our results indicate that microbes in the deep subseafloor environment off Shimokita are metabolically active and that the cultivable populations may have a great potential in biotechnology.

Gene expression in the deep biosphere.

PubMed

Orsi, William D; Edgcomb, Virginia P; Christman, Glenn D; Biddle, Jennifer F

2013-07-11

Scientific ocean drilling has revealed a deep biosphere of widespread microbial life in sub-seafloor sediment. Microbial metabolism in the marine subsurface probably has an important role in global biogeochemical cycles, but deep biosphere activities are not well understood. Here we describe and analyse the first sub-seafloor metatranscriptomes from anaerobic Peru Margin sediment up to 159 metres below the sea floor, represented by over 1 billion complementary DNA (cDNA) sequence reads. Anaerobic metabolism of amino acids, carbohydrates and lipids seem to be the dominant metabolic processes, and profiles of dissimilatory sulfite reductase (dsr) transcripts are consistent with pore-water sulphate concentration profiles. Moreover, transcripts involved in cell division increase as a function of microbial cell concentration, indicating that increases in sub-seafloor microbial abundance are a function of cell division across all three domains of life. These data support calculations and models of sub-seafloor microbial metabolism and represent the first holistic picture of deep biosphere activities.

Sorption and oxic degradation of the explosive CL-20 during transport in subsurface sediments.

PubMed

Szecsody, J E; Girvin, D C; Devary, B J; Campbell, J A

2004-08-01

The abiotic sorption and oxic degradation processes that control the fate of the explosive CL-20, Hexanitrohexaazaisowurtzitane, in the subsurface environment were investigated to determine the potential for vadose and groundwater contamination. Sorption of aqueous CL-20 is relatively small (K(d) = 0.02-3.83 cm3 g(-1) for 7 sediments and 12 minerals), which results in only slight retardation relative to water movement. Thus, CL-20 could move quickly through unsaturated and saturated sediments of comparable composition to groundwater, similar to the subsurface behavior of RDX. CL-20 sorption was mainly to mineral surfaces of the sediments, and the resulting isotherm was nonlinear. CL-20 abiotically degrades in oxic environments at slow rates (i.e., 10s to 100s of hours) with a wide variety of minerals, but at fast rates (i.e., minutes) in the presence of 2:1 phyllosilicate clays (hectorite, montmorillonite, nontronite), micas (biotite, illite), and specific oxides (MnO2 and the ferrous-ferric iron oxide magnetite). High concentrations of surface ferrous iron in a dithionite reduced sediment degraded CL-20 the fastest (half-life < 0.05 h), but 2:1 clays containing no structural or adsorbed ferrous iron (hectorite) could also quickly degrade CL-20 (half-life < 0.2 h). CL-20 degradation rates were slower in natural sediments (half-life 3-800 h) compared to minerals. Sediments with slow degradation rates and small sorption would exhibit the highest potential for deep subsurface migration. Products of CL-20 oxic degradation included three high molecular weight compounds and anions (nitrite and formate). The 2-3.5 moles of nitrite produced suggest CL-20 nitro-groups are degraded, and the amount of formate produced (0.2-1.2 moles) suggests the CL-20 cage structure is broken in some sediments. Identification of further degradation products and CL-20 mineralization rates is needed to fully assess the impact of these CL-20 transformation rates on the risk of CL-20 (and degradation product) subsurface movement.

The deep biosphere in terrestrial sediments in the chesapeake bay area, virginia, USA.

PubMed

Breuker, Anja; Köweker, Gerrit; Blazejak, Anna; Schippers, Axel

2011-01-01

For the first time quantitative data on the abundance of Bacteria, Archaea, and Eukarya in deep terrestrial sediments are provided using multiple methods (total cell counting, quantitative real-time PCR, Q-PCR and catalyzed reporter deposition-fluorescence in situ hybridization, CARD-FISH). The oligotrophic (organic carbon content of ∼0.2%) deep terrestrial sediments in the Chesapeake Bay area at Eyreville, Virginia, USA, were drilled and sampled up to a depth of 140 m in 2006. The possibility of contamination during drilling was checked using fluorescent microspheres. Total cell counts decreased from 10(9) to 10(6) cells/g dry weight within the uppermost 20 m, and did not further decrease with depth below. Within the top 7 m, a significant proportion of the total cell counts could be detected with CARD-FISH. The CARD-FISH numbers for Bacteria were about an order of magnitude higher than those for Archaea. The dominance of Bacteria over Archaea was confirmed by Q-PCR. The down core quantitative distribution of prokaryotic and eukaryotic small subunit ribosomal RNA genes as well as functional genes involved in different biogeochemical processes was revealed by Q-PCR for the uppermost 10 m and for 80-140 m depth. Eukarya and the Fe(III)- and Mn(IV)-reducing bacterial group Geobacteriaceae were almost exclusively found in the uppermost meter (arable soil), where reactive iron was detected in higher amounts. The bacterial candidate division JS-1 and the classes Anaerolineae and Caldilineae of the phylum Chloroflexi, highly abundant in marine sediments, were found up to the maximum sampling depth in high copy numbers at this terrestrial site as well. A similar high abundance of the functional gene cbbL encoding for the large subunit of RubisCO suggests that autotrophic microorganisms could be relevant in addition to heterotrophs. The functional gene aprA of sulfate reducing bacteria was found within distinct layers up to ca. 100 m depth in low copy numbers. The gene mcrA of methanogens was not detectable. Cloning and sequencing data of 16S rRNA genes revealed sequences of typical soil Bacteria. The closest relatives of the archaeal sequences were Archaea recovered from terrestrial and marine environments. Phylogenetic analysis of the Crenarchaeota and Euryarchaeota revealed new members of the uncultured South African Gold Mine Group, Deep Sea Hydrothermal Vent Euryarchaeotal Group 6, and Miscellaneous Crenarcheotic Group clusters.

Active Marine Subsurface Bacterial Population Composition in Low Organic Carbon Environments from IODP Expedition 320

NASA Astrophysics Data System (ADS)

Shepard, A.; Reese, B. K.; Mills, H. J.; IODP Expedition 320 Shipboard Science Party

2011-12-01

The marine subsurface environment contains abundant and active microorganisms. These microbial populations are considered integral players in the marine subsurface biogeochemical system with significance in global geochemical cycles and reservoirs. However, variations in microbial community structure, activity and function associated with the wide-ranging sedimentary and geochemical environments found globally have not been fully resolved. Integrated Ocean Drilling Program Expedition 320 recovered sediments from site U1332. Two sampling depths were selected for analysis that spanned differing lithological units in the sediment core. Sediments were composed of mostly clay with zeolite minerals at 8 meters below sea floor (mbsf). At 27 mbsf, sediments were composed of alternating clayey radiolarian ooze and nannofossil ooze. The concentration of SO42- had little variability throughout the core and the concentration of Fe2+ remained close to, or below, detection limits (0.4 μM). Total organic carbon content ranged from a low of 0.03 wt% to a high of 0.07 wt% between 6 and 30 mbsf providing an opportunity to evaluate marine subsurface microbial communities under extreme electron donor limiting conditions. The metabolically active fraction of the bacterial population was isolated by the extraction and amplification of 16S ribosomal RNA. Pyrosequencing of 16S rRNA transcripts and subsequent bioinformatic analyses provided a robust data set (15,931 total classified sequences) to characterize the community at a high resolution. As observed in other subsurface environments, the overall diversity of active bacterial populations decreased with depth. The population shifted from a diverse but evenly distributed community at approximately 8 mbsf to a Firmicutes dominated population at 27 mbsf (80% of sequences). A total of 95% of the sequences at 27 mbsf were grouped into three genera: Lactobacillus (phylum Firmicutes) at 80% of the total sequences, Marinobacter (phylum Proteobacteria) at 8%, and Formosa (phylum Bacteroidetes) at 7%. These lineages support a paradigm suggesting the importance of fermentation in the subsurface. However, this study extends the predicted range for fermentation below the shallow subsurface and into organic carbon limited marine sediments. Other previously characterized subsurface active populations from environments with higher organic carbon concentrations do not show similar levels of reduced diversity or predominance of fermentative populations. This study further emphasizes the spatial variability of microbial populations in the deep subsurface and highlights the need for continued exploration.

Biogeochemical Cycle of Methanol in Anoxic Deep-Sea Sediments

PubMed Central

Yanagawa, Katsunori; Tani, Atsushi; Yamamoto, Naoya; Hachikubo, Akihiro; Kano, Akihiro; Matsumoto, Ryo; Suzuki, Yohey

2016-01-01

The biological flux and lifetime of methanol in anoxic marine sediments are largely unknown. We herein reported, for the first time, quantitative methanol removal rates in subsurface sediments. Anaerobic incubation experiments with radiotracers showed high rates of microbial methanol consumption. Notably, methanol oxidation to CO2 surpassed methanol assimilation and methanogenesis from CO2/H2 and methanol. Nevertheless, a significant decrease in methanol was not observed after the incubation, and this was attributed to the microbial production of methanol in parallel with its consumption. These results suggest that microbial reactions play an important role in the sources and sinks of methanol in subseafloor sediments. PMID:27301420

Current status and historical trends of organochlorine pesticides in the ecosystem of Deep Bay, South China

NASA Astrophysics Data System (ADS)

Qiu, Yao-Wen; Zhang, Gan; Guo, Ling-Li; Cheng, Hai-Rong; Wang, Wen-Xiong; Li, Xiang-Dong; Wai, Onyx W. H.

2009-11-01

To characterize the current status and historical trends in organochlorine pesticides (OCPs) contamination in Deep Bay, an important water body between Hong Kong and mainland China with a Ramsar mangrove wetland (Maipo), samples from seawater, suspended particulate matter (SPM), surface sediment, sediment core and fish were collected to determine the OCPs concentrations. Sediment core dating was accomplished using the 210Pb method. The average concentrations of DDTs, HCHs and chlordanes in water were 1.96, 0.71, 0.81 ng l -1, while in SPM were 36.5, 2.5, 35.7 ng g -1 dry weight, in surface sediment were 20.2, 0.50, 2.4 ng g -1 dry weight, and in fish were 125.4, 0.43, 13.1 ng g -1 wet weight, respectively. DDTs concentrations in various matrices of Deep Bay were intermediate compared with those in other areas. Temporal trends of the targeted OCPs levels in sediment core generally increased from 1948 to 2004, with the highest levels in top or sub-surface sediment. Both DDT composition and historical trends indicated an ongoing fresh DDT input. A positive relationship between the bioconcentration factor (BCF) of target chemicals and the corresponding octanol-water partition coefficient ( Kow), and between the biota-sediment accumulation factors (BSAF) and the Kow were observed in the Bay. The risk assessment indicated that there were potential ecological and human health risks for the target OCPs in Deep Bay.

Earthquakes drive large-scale submarine canyon development and sediment supply to deep-ocean basins.

PubMed

Mountjoy, Joshu J; Howarth, Jamie D; Orpin, Alan R; Barnes, Philip M; Bowden, David A; Rowden, Ashley A; Schimel, Alexandre C G; Holden, Caroline; Horgan, Huw J; Nodder, Scott D; Patton, Jason R; Lamarche, Geoffroy; Gerstenberger, Matthew; Micallef, Aaron; Pallentin, Arne; Kane, Tim

2018-03-01

Although the global flux of sediment and carbon from land to the coastal ocean is well known, the volume of material that reaches the deep ocean-the ultimate sink-and the mechanisms by which it is transferred are poorly documented. Using a globally unique data set of repeat seafloor measurements and samples, we show that the moment magnitude ( M w ) 7.8 November 2016 Kaikōura earthquake (New Zealand) triggered widespread landslides in a submarine canyon, causing a powerful "canyon flushing" event and turbidity current that traveled >680 km along one of the world's longest deep-sea channels. These observations provide the first quantification of seafloor landscape change and large-scale sediment transport associated with an earthquake-triggered full canyon flushing event. The calculated interevent time of ~140 years indicates a canyon incision rate of 40 mm year -1 , substantially higher than that of most terrestrial rivers, while synchronously transferring large volumes of sediment [850 metric megatons (Mt)] and organic carbon (7 Mt) to the deep ocean. These observations demonstrate that earthquake-triggered canyon flushing is a primary driver of submarine canyon development and material transfer from active continental margins to the deep ocean.

Earthquakes drive large-scale submarine canyon development and sediment supply to deep-ocean basins

PubMed Central

Mountjoy, Joshu J.; Howarth, Jamie D.; Orpin, Alan R.; Barnes, Philip M.; Bowden, David A.; Rowden, Ashley A.; Schimel, Alexandre C. G.; Holden, Caroline; Horgan, Huw J.; Nodder, Scott D.; Patton, Jason R.; Lamarche, Geoffroy; Gerstenberger, Matthew; Micallef, Aaron; Pallentin, Arne; Kane, Tim

2018-01-01

Although the global flux of sediment and carbon from land to the coastal ocean is well known, the volume of material that reaches the deep ocean—the ultimate sink—and the mechanisms by which it is transferred are poorly documented. Using a globally unique data set of repeat seafloor measurements and samples, we show that the moment magnitude (Mw) 7.8 November 2016 Kaikōura earthquake (New Zealand) triggered widespread landslides in a submarine canyon, causing a powerful “canyon flushing” event and turbidity current that traveled >680 km along one of the world’s longest deep-sea channels. These observations provide the first quantification of seafloor landscape change and large-scale sediment transport associated with an earthquake-triggered full canyon flushing event. The calculated interevent time of ~140 years indicates a canyon incision rate of 40 mm year−1, substantially higher than that of most terrestrial rivers, while synchronously transferring large volumes of sediment [850 metric megatons (Mt)] and organic carbon (7 Mt) to the deep ocean. These observations demonstrate that earthquake-triggered canyon flushing is a primary driver of submarine canyon development and material transfer from active continental margins to the deep ocean. PMID:29546245

Combined use of radiocarbon and stable carbon isotope to constrain the sources and cycling of particulate organic carbon in a large freshwater lake, China.

PubMed

Chen, Jingan; Yang, Haiquan; Zeng, Yan; Guo, Jianyang; Song, Yilong; Ding, Wei

2018-06-01

The concentrations and isotopic compositions of dissolved inorganic carbon (DIC) and particulate organic carbon (POC) were measured in order to better constrain the sources and cycling of POC in Lake Fuxian, the largest deep freshwater lake in China. Model results based on the combined δ 13 C and Δ 14 C, showed that the average lake-wide contributions of autochthonous POC, terrestrial POC, and resuspended sediment POC to the bulk POC in Lake Fuxian were 61%, 22%, and 17%, respectively. This indicated autochthonous POC might play a dominant role in sustaining large oligotrophic lake ecosystem. A mean 17% contribution of resuspended sediment POC to the bulk POC implied that sediment might have more significant influence on aquatic environment and ecosystem than previously recognized in large deep lakes. The contributions of different sources POC to the water-column POC were a function of the initial composition of the source materials, photosynthesis, physical regime of the lake, sediment resuspension, respiration and degradation of organic matter, and were affected indirectly by environmental factors such as light, temperature, DO, wind speed, turbidity, and nutrient concentration. This study is not only the first systematic investigation on the radiocarbon and stable isotope compositions of POC in large deep freshwater lake in China, but also one of the most extensive radiocarbon studies on the ecosystem of any great lakes in the world. The unique data constrain relative influences of autochthonous POC, terrestrial POC, and resuspended sediment POC, and deepen the understanding of the POC cycling in large freshwater lakes. This study is far from comprehensive, but it serves to highlight the potential of combined radiocarbon and stable carbon isotope for constraining the sources and cycling of POC in large lake system. More radiocarbon investigations on the water-column POC and the aquatic food webs are necessary to illuminate further the fate of autochthonous POC, terrestrial POC, and resuspended sediment POC, and their eco-environmental effects. Copyright © 2017 Elsevier B.V. All rights reserved.

Biodiversity of polycyclic aromatic hydrocarbon-degrading bacteria from deep sea sediments of the Middle Atlantic Ridge.

PubMed

Cui, Zhisong; Lai, Qiliang; Dong, Chunming; Shao, Zongze

2008-08-01

The bacteria involved in the biodegradation of polycyclic aromatic hydrocarbons (PAHs) in deep sea subsurface environments are largely unknown. In order to reveal their biodiversity, sediments from 2.2 m under the bottom surface at a water depth of 3542 m were sampled on the Middle Atlantic Ridge with a gravity column sampler. The sediments were promptly enriched with either crude oil or a mixture of PAHs (naphthalene, phenanthrene and pyrene) as the sole carbon source, and further enriched with the PAH mixture mentioned above in the lab. The resulting consortia were named C2CO and C2PPN respectively. Their bacterial composition was analysed with plate cultivation, PCR-DGGE and 16S rDNA library analysis. On plates, isolates belonging to Pseudoalteromonas, Halomonas, Marinobacter, Thalassospira and Tistrella dominated the culturable populations. With PCR-DGGE, five major bands closely related to Cycloclasticus, Alteromonas, Thalassospira, Alcanivorax and Rhodospirillaceae were detected in consortium C2CO, while only one major band of Cycloclasticus was detected in consortium C2PPN. In addition, the dynamics of community structure in response to aromatic substrate alterations were examined. As a result, three ribotypes of Cycloclasticus were detected by 16S rDNA library analysis, one which played a key role in phenanthrene degradation; two Alteromonas bacteria dominated the naphthalene reselected consortium. Although bacteria of the two genera grew as the main members of the communities, none of them were isolated, probably owing to their poor cultivability. These results confirm that bacteria of Cycloclasticus are important obligate PAH degraders in marine environments, and coexist with other degrading bacteria that inhabit the deep subsurface sediment of the Atlantic. This supports the view that PAH accumulation and bioattenuation occur in remote areas consistently and continuously.

Biodiversity of polycyclic aromatic hydrocarbon-degrading bacteria from deep sea sediments of the Middle Atlantic Ridge

PubMed Central

Cui, Zhisong; Lai, Qiliang; Dong, Chunming; Shao, Zongze

2008-01-01

The bacteria involved in the biodegradation of polycyclic aromatic hydrocarbons (PAHs) in deep sea subsurface environments are largely unknown. In order to reveal their biodiversity, sediments from 2.2 m under the bottom surface at a water depth of 3542 m were sampled on the Middle Atlantic Ridge with a gravity column sampler. The sediments were promptly enriched with either crude oil or a mixture of PAHs (naphthalene, phenanthrene and pyrene) as the sole carbon source, and further enriched with the PAH mixture mentioned above in the lab. The resulting consortia were named C2CO and C2PPN respectively. Their bacterial composition was analysed with plate cultivation, PCR-DGGE and 16S rDNA library analysis. On plates, isolates belonging to Pseudoalteromonas, Halomonas, Marinobacter, Thalassospira and Tistrella dominated the culturable populations. With PCR-DGGE, five major bands closely related to Cycloclasticus, Alteromonas, Thalassospira, Alcanivorax and Rhodospirillaceae were detected in consortium C2CO, while only one major band of Cycloclasticus was detected in consortium C2PPN. In addition, the dynamics of community structure in response to aromatic substrate alterations were examined. As a result, three ribotypes of Cycloclasticus were detected by 16S rDNA library analysis, one which played a key role in phenanthrene degradation; two Alteromonas bacteria dominated the naphthalene reselected consortium. Although bacteria of the two genera grew as the main members of the communities, none of them were isolated, probably owing to their poor cultivability. These results confirm that bacteria of Cycloclasticus are important obligate PAH degraders in marine environments, and coexist with other degrading bacteria that inhabit the deep subsurface sediment of the Atlantic. This supports the view that PAH accumulation and bioattenuation occur in remote areas consistently and continuously. PMID:18445026

Non-viable Microbial Community Structure and Geochemistry of Deep Subsurface Shales at Marcellus Shale Energy and Environment Laboratory

NASA Astrophysics Data System (ADS)

Akondi, R.; Trexler, R.; Sharma, S.; Mouser, P. J.; Pfiffner, S. M.

2016-12-01

The deep subsurface is known to harbor diverse communities of living microbes, and can therefore be expected to also harbor an equally diverse and likely different set of non-viable microbial populations. In this study, diglyceride fatty acids, (DGFA, biomarkers for non-viable microbes) as well as their compound specific isotopes (CSIA) were used to study the yield and variety of DGFAs in deep subsurface mid-Devonian sediments of different lithologies. Pristine sidewall cores were obtained from intervals in the Marcellus, Mahantango, and the Marcellus/Mahantango formation interface. The biomarkers were extracted and DGFAs were methylated to fatty acid methyl esters (FAMEs) and analyzed using GC-MS, while the CSIAs were performed using GC-irMS. Sediments were also analyzed for total organic carbon (TOC), stable carbon isotopic composition of organic carbon (δ13Corg), inorganic carbon (δ13Ccarb), and nitrogen (δ15Norg). TOC concentration was highest in the Marcellus and there was a general trend of increasing TOC from Mahantango to the Marcellus. The δ13Corg and δ13Ccarb increased and decreased respectively from Mahantango to the Marcellus while δ15Norg did not show any trend. The FAME profiles consisted of normal saturated, monounsaturated, polyunsaturated, branched, epoxy, terminally branched, hydroxyl, and dimethyl esters. The total biomass yield and variety of DGFA-FAME profiles were higher in the Mahantango compared to the samples from the Marcellus formation and Marcellus/Mahantango interface, suggesting the presence of more paleo-microbial activity in the less consolidated Mahantango formation. We attribute this to the smaller pore throat sizes within the Marcellus formation compared to the Mahantango formation. Since organic matter in the sediments is also one of the key sources of energy for microbial metabolism, bulk 13C and CSIA of the lipids will be used to understand the source(s) and pathways of the carbon cycling within the microbial communities.

Temperature and pressure adaptation of a sulfate reducer from the deep subsurface

PubMed Central

Fichtel, Katja; Logemann, Jörn; Fichtel, Jörg; Rullkötter, Jürgen; Cypionka, Heribert; Engelen, Bert

2015-01-01

Microbial life in deep marine subsurface faces increasing temperatures and hydrostatic pressure with depth. In this study, we have examined growth characteristics and temperature-related adaptation of the Desulfovibrio indonesiensis strain P23 to the in situ pressure of 30 MPa. The strain originates from the deep subsurface of the eastern flank of the Juan de Fuca Ridge (IODP Site U1301). The organism was isolated at 20°C and atmospheric pressure from ~61°C-warm sediments approximately 5 m above the sediment–basement interface. In comparison to standard laboratory conditions (20°C and 0.1 MPa), faster growth was recorded when incubated at in situ pressure and high temperature (45°C), while cell filamentation was induced by further compression. The maximum growth temperature shifted from 48°C at atmospheric pressure to 50°C under high-pressure conditions. Complementary cellular lipid analyses revealed a two-step response of membrane viscosity to increasing temperature with an exchange of unsaturated by saturated fatty acids and subsequent change from branched to unbranched alkyl moieties. While temperature had a stronger effect on the degree of fatty acid saturation and restructuring of main phospholipids, pressure mainly affected branching and length of side chains. The simultaneous decrease of temperature and pressure to ambient laboratory conditions allowed the cultivation of our moderately thermophilic strain. This may in turn be one key to a successful isolation of microorganisms from the deep subsurface adapted to high temperature and pressure. PMID:26500624

Global Drainage Patterns to Modern Terrestrial Sedimentary Basins and its Influence on Large River Systems

NASA Astrophysics Data System (ADS)

Nyberg, B.; Helland-Hansen, W.

2017-12-01

Long-term preservation of alluvial sediments is dependent on the hydrological processes that deposit sediments solely within an area that has available accomodation space and net subsidence know as a sedimentary basin. An understanding of the river processes contributing to terrestrial sedimentary basins is essential to fundamentally constrain and quantify controls on the modern terrestrial sink. Furthermore, the terrestrial source to sink controls place constraints on the entire coastal, shelf and deep marine sediment routing systems. In addition, the geographical importance of modern terrestrial sedimentary basins for agriculture and human settlements has resulted in significant upstream anthropogenic catchment modification for irrigation and energy needs. Yet to our knowledge, a global catchment model depicting the drainage patterns to modern terrestrial sedimentary basins has previously not been established that may be used to address these challenging issues. Here we present a new database of 180,737 global catchments that show the surface drainage patterns to modern terrestrial sedimentary basins. This is achieved by using high resolution river networks derived from digital elevation models in relation to newly acquired maps on global modern sedimentary basins to identify terrestrial sinks. The results show that active tectonic regimes are typically characterized by larger terrestrial sedimentary basins, numerous smaller source catchments and a high source to sink relief ratio. To the contrary passive margins drain catchments to smaller terrestrial sedimentary basins, are composed of fewer source catchments that are relatively larger and a lower source to sink relief ratio. The different geomorphological characteristics of source catchments by tectonic setting influence the spatial and temporal patterns of fluvial architecture within sedimentary basins and the anthropogenic methods of exploiting those rivers. The new digital database resource is aimed to help the geoscientific community to contribute further to our quantitative understanding of source-to-sink systems and its allogenic and autogenic controls, geomorphological characteristics, terrestrial sediment transit times and the anthropogenic impact on those systems.

Atribacteria from the Subseafloor Sedimentary Biosphere Disperse to the Hydrosphere through Submarine Mud Volcanoes.

PubMed

Hoshino, Tatsuhiko; Toki, Tomohiro; Ijiri, Akira; Morono, Yuki; Machiyama, Hideaki; Ashi, Juichiro; Okamura, Kei; Inagaki, Fumio

2017-01-01

Submarine mud volcanoes (SMVs) are formed by muddy sediments and breccias extruded to the seafloor from a source in the deep subseafloor and are characterized by the discharge of methane and other hydrocarbon gasses and deep-sourced fluids into the overlying seawater. Although SMVs act as a natural pipeline connecting the Earth's surface and subsurface biospheres, the dispersal of deep-biosphere microorganisms and their ecological roles remain largely unknown. In this study, we investigated the microbial communities in sediment and overlying seawater at two SMVs located on the Ryukyu Trench off Tanegashima Island, southern Japan. The microbial communities in mud volcano sediments were generally distinct from those in the overlying seawaters and in the well-stratified Pacific margin sediments collected at the Peru Margin, the Juan de Fuca Ridge flank off Oregon, and offshore of Shimokita Peninsula, northeastern Japan. Nevertheless, in-depth analysis of different taxonomic groups at the sub-species level revealed that the taxon affiliated with Atribacteria , heterotrophic anaerobic bacteria that typically occur in organic-rich anoxic subseafloor sediments, were commonly found not only in SMV sediments but also in the overlying seawater. We designed a new oligonucleotide probe for detecting Atribacteria using the catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH). CARD-FISH, digital PCR and sequencing analysis of 16S rRNA genes consistently showed that Atribacteria are abundant in the methane plumes of the two SMVs (0.58 and 1.5 × 10 4 cells/mL, respectively) but not in surrounding waters, suggesting that microbial cells in subseafloor sediments are dispersed as "deep-biosphere seeds" into the ocean. These findings may have important implications for the microbial transmigration between the deep subseafloor biosphere and the hydrosphere.

Atribacteria from the Subseafloor Sedimentary Biosphere Disperse to the Hydrosphere through Submarine Mud Volcanoes

PubMed Central

Hoshino, Tatsuhiko; Toki, Tomohiro; Ijiri, Akira; Morono, Yuki; Machiyama, Hideaki; Ashi, Juichiro; Okamura, Kei; Inagaki, Fumio

2017-01-01

Submarine mud volcanoes (SMVs) are formed by muddy sediments and breccias extruded to the seafloor from a source in the deep subseafloor and are characterized by the discharge of methane and other hydrocarbon gasses and deep-sourced fluids into the overlying seawater. Although SMVs act as a natural pipeline connecting the Earth’s surface and subsurface biospheres, the dispersal of deep-biosphere microorganisms and their ecological roles remain largely unknown. In this study, we investigated the microbial communities in sediment and overlying seawater at two SMVs located on the Ryukyu Trench off Tanegashima Island, southern Japan. The microbial communities in mud volcano sediments were generally distinct from those in the overlying seawaters and in the well-stratified Pacific margin sediments collected at the Peru Margin, the Juan de Fuca Ridge flank off Oregon, and offshore of Shimokita Peninsula, northeastern Japan. Nevertheless, in-depth analysis of different taxonomic groups at the sub-species level revealed that the taxon affiliated with Atribacteria, heterotrophic anaerobic bacteria that typically occur in organic-rich anoxic subseafloor sediments, were commonly found not only in SMV sediments but also in the overlying seawater. We designed a new oligonucleotide probe for detecting Atribacteria using the catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH). CARD-FISH, digital PCR and sequencing analysis of 16S rRNA genes consistently showed that Atribacteria are abundant in the methane plumes of the two SMVs (0.58 and 1.5 × 104 cells/mL, respectively) but not in surrounding waters, suggesting that microbial cells in subseafloor sediments are dispersed as “deep-biosphere seeds” into the ocean. These findings may have important implications for the microbial transmigration between the deep subseafloor biosphere and the hydrosphere. PMID:28676800

Effects of remediation amendments on vadose zone microorganisms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Hannah M.; Tilton, Fred A.

2012-08-10

Surfactant-based foam delivery technology has been studied to remediate Hanford 200 area deep vadose zone sediment. However, the surfactants and remediation amendments have an unknown effect on indigenous subsurface microorganisms. Microbial populations are important factors to consider in remediation efforts due to their potential to alter soil geochemistry. This project focuses on measuring microbial metabolic responses to remediation amendments in batch and column studies using Deep Vadose Zone Sediments. Initial studies of the microbes from Hanford 200 area deep vadose zone sediment showed surfactants sodium dodecyl sulfate (SDS) and cocamidopropyl betaine (CAPB) and remediation amendment calcium polysulfide (CPS) had nomore » affect on microbial growth using BiologTM Ecoplates. To move towards a more realistic field analog, soil columns were packed with Hanford 200 Area sediment. Once microbial growth in the column was verified by observing growth of the effluent solution on tryptic soy agar plates, remedial surfactants were injected into the columns, and the resulting metabolic diversity was measured. Results suggest surfactant sodium dodecyl sulfate (SDS) stimulates microbial growth. The soil columns were also visualized using X-ray microtomography to inspect soil packing and possibly probe for evidence of biofilms. Overall, BiologTM Ecoplates provide a rapid assay to predict effects of remediation amendments on Hanford 200 area deep vadose zone microorganisms.« less

Novel applications for biogeophysics: Prospects for detecting key subseafloor geomicrobiological processes or habitats

NASA Astrophysics Data System (ADS)

Colwell, F. S.; Ntarlagiannis, D.

2007-05-01

The new subdiscipline of biogeophysics has focused mostly on the geophysical signatures of microbial processes in contaminated subsurface environments usually undergoing remediation. However, the use of biogeophysics to examine the biogeochemistry of marine sediments has not yet been well-integrated into conceptual models that describe subseafloor processes. Current examples of geophysical measurements that have been used to detect geomicrobiological processes or infer their location in the seafloor include sound surveillance system (SOSUS)-derived data that detect seafloor eruptive events, deep and shallow cross-sectional seismic surveys that determine the presence of hydraulically conductive zones or gas-bearing sediments (e.g., bottom-simulating reflectors or bubble-rich strata), and thermal profiles. One possible area for innovative biogeophysical characterization of the seafloor involves determining the depth of the sulfate-methane interface (SMI) in locations where sulfate diffuses from the seawater and methane emanates from subsurface strata. The SMI demarcates a stratum where microbially-driven anaerobic methane oxidation (AMO) is dependent upon methane as an electron donor and sulfate as an electron acceptor. AMO is carried out by a recently defined, unique consortium of microbes that metabolically temper the flux of methane into the overlying seawater. The depth of the SMI is, respectively, shallow or deep according to whether a high or low rate of methane flux occurs from the deep sediments. Presently, the SMI can only be determined by direct measurements of methane and sulfate concentrations in the interstitial waters or by molecular biological techniques that target the microbes responsible for creating the SMI. Both methods require collection and considerable analysis of sediment samples. Therefore, detection of the SMI by non-destructive methods would be advantageous. As a key biogeochemical threshold in marine sediments, the depth of the SMI defines methane charge in marine sediments, whether it is from dissolved methane or from methane hydrates. As such, a biogeophysical strategy for determining SMI depth would represent an important contribution to assessing methane charge with respect to climate change, sediment stability, or potential energy resources.

Microbial activity in the marine deep biosphere: progress and prospects.

PubMed

Orcutt, Beth N; Larowe, Douglas E; Biddle, Jennifer F; Colwell, Frederick S; Glazer, Brian T; Reese, Brandi Kiel; Kirkpatrick, John B; Lapham, Laura L; Mills, Heath J; Sylvan, Jason B; Wankel, Scott D; Wheat, C Geoff

2013-01-01

The vast marine deep biosphere consists of microbial habitats within sediment, pore waters, upper basaltic crust and the fluids that circulate throughout it. A wide range of temperature, pressure, pH, and electron donor and acceptor conditions exists-all of which can combine to affect carbon and nutrient cycling and result in gradients on spatial scales ranging from millimeters to kilometers. Diverse and mostly uncharacterized microorganisms live in these habitats, and potentially play a role in mediating global scale biogeochemical processes. Quantifying the rates at which microbial activity in the subsurface occurs is a challenging endeavor, yet developing an understanding of these rates is essential to determine the impact of subsurface life on Earth's global biogeochemical cycles, and for understanding how microorganisms in these "extreme" environments survive (or even thrive). Here, we synthesize recent advances and discoveries pertaining to microbial activity in the marine deep subsurface, and we highlight topics about which there is still little understanding and suggest potential paths forward to address them. This publication is the result of a workshop held in August 2012 by the NSF-funded Center for Dark Energy Biosphere Investigations (C-DEBI) "theme team" on microbial activity (www.darkenergybiosphere.org).

Microbial activity in the marine deep biosphere: progress and prospects

PubMed Central

Orcutt, Beth N.; LaRowe, Douglas E.; Biddle, Jennifer F.; Colwell, Frederick S.; Glazer, Brian T.; Reese, Brandi Kiel; Kirkpatrick, John B.; Lapham, Laura L.; Mills, Heath J.; Sylvan, Jason B.; Wankel, Scott D.; Wheat, C. Geoff

2013-01-01

The vast marine deep biosphere consists of microbial habitats within sediment, pore waters, upper basaltic crust and the fluids that circulate throughout it. A wide range of temperature, pressure, pH, and electron donor and acceptor conditions exists—all of which can combine to affect carbon and nutrient cycling and result in gradients on spatial scales ranging from millimeters to kilometers. Diverse and mostly uncharacterized microorganisms live in these habitats, and potentially play a role in mediating global scale biogeochemical processes. Quantifying the rates at which microbial activity in the subsurface occurs is a challenging endeavor, yet developing an understanding of these rates is essential to determine the impact of subsurface life on Earth's global biogeochemical cycles, and for understanding how microorganisms in these “extreme” environments survive (or even thrive). Here, we synthesize recent advances and discoveries pertaining to microbial activity in the marine deep subsurface, and we highlight topics about which there is still little understanding and suggest potential paths forward to address them. This publication is the result of a workshop held in August 2012 by the NSF-funded Center for Dark Energy Biosphere Investigations (C-DEBI) “theme team” on microbial activity (www.darkenergybiosphere.org). PMID:23874326

Characterization of microbial communities in subsurface nuclear blast cavities of the Nevada Test Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moser, Duane P; Czerwinski, Ken; Russell, Charles E

2010-07-13

This US Department of Energy (DOE) Environmental Remediation Sciences Project (ERSP) was designed to test fundamental hypotheses concerning the existence and nature of indigenous microbial populations of Nevada Test Site subsurface nuclear test/detonation cavities. Now called Subsurface Biogeochemical Research (SBR), this program's Exploratory Research (ER) element, which funded this research, is designed to support high risk, high potential reward projects. Here, five cavities (GASCON, CHANCELLOR, NASH, ALEMAN, and ALMENDRO) and one tunnel (U12N) were sampled using bailers or pumps. Molecular and cultivation-based techniques revealed bacterial signatures at five sites (CHANCELLOR may be lifeless). SSU rRNA gene libraries contained diverse andmore » divergent microbial sequences affiliated with known metal- and sulfur-cycling microorganisms, organic compound degraders, microorganisms from deep mines, and bacteria involved in selenate reduction and arsenite oxidation. Close relatives of Desulforudis audaxviator, a microorganism thought to subsist in the terrestrial deep subsurface on H2 and SO42- produced by radiochemical reactions, was detected in the tunnel waters. NTS-specific media formulations were used to culture and quantify nitrate-, sulfate-, iron-reducing, fermentative, and methanogenic microorganisms. Given that redox manipulations mediated by microorganisms can impact the mobility of DOE contaminants, our results should have implications for management strategies at this and other DOE sites.« less

Characterization of Microbial Communities in Subsurface Nuclear Blast Cavities of the Nevada Test Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moser, Duane P.; Bruckner, Jim; Fisher, Jen

2010-09-01

This U.S. Department of Energy (DOE) Environmental Remediation Sciences Project (ERSP) was designed to test fundamental hypotheses concerning the existence and nature of indigenous microbial populations of Nevada Test Site subsurface nuclear test/detonation cavities. Now called Subsurface Biogeochemical Research (SBR), this program’s Exploratory Research (ER) element, which funded this research, is designed to support high risk, high potential reward projects. Here, five cavities (GASCON, CHANCELLOR, NASH, ALEMAN, and ALMENDRO) and one tunnel (U12N) were sampled using bailers or pumps. Molecular and cultivation-based techniques revealed bacterial signatures at five sites (CHANCELLOR may be lifeless). SSU rRNA gene libraries contained diverse andmore » divergent microbial sequences affiliated with known metal- and sulfur-cycling microorganisms, organic compound degraders, microorganisms from deep mines, and bacteria involved in selenate reduction and arsenite oxidation. Close relatives of Desulforudis audaxviator, a microorganism thought to subsist in the terrestrial deep subsurface on H2 and SO42- produced by radiochemical reactions, was detected in the tunnel waters. NTS-specific media formulations were used to culture and quantify nitrate-, sulfate-, iron-reducing, fermentative, and methanogenic microorganisms. Given that redox manipulations mediated by microorganisms can impact the mobility of DOE contaminants, our results should have implications for management strategies at this and other DOE sites.« less

Low temperature hydrothermal maturation of organic matter in sediments from the Atlantis II Deep, Red Sea.

PubMed

Simoneit, B R; Grimalt, J O; Hayes, J M; Hartman, H

1987-01-01

Hydrocarbons and bulk organic matter of two sediment cores (No. 84 and 126, CHAIN 61 cruise) located within the Atlantis II Deep have been analyzed. Although the brines overlying the coring areas were reported to be sterile, microbial inputs and minor terrestrial sources the major sedimentary organic material. This input is derived from the upper water column above the brines. Both steroid and triterpenoid hydrocarbons show that extensive acid-catalyzed reactions are occurring in the sediments. In comparison with other hydrothermal (Guaymas Basin) or intrusive systems (Cape Verde Rise), the Atlantis II Deep exhibits a lower degree of thermal maturation. This is easily deduced from the elemental composition of the kerogens and the absence of polynuclear aromatic hydrocarbons of a pyrolytic origin in the bitumen. The lack of carbon number preference among the n-alkanes suggests, especially in the case of the long chain homologs, that the organic matter of Atlantis II Deep sediments has undergone some degree of catagenesis. However, the yields of hydrocarbons are much lower than those observed in other hydrothermal areas. The effect of lower temperature and poor source-rock characteristics appear to be responsible for the differences.

Reactive Fe(II) layers in deep-sea sediments

NASA Astrophysics Data System (ADS)

König, Iris; Haeckel, Matthias; Drodt, Matthias; Suess, Erwin; Trautwein, Alfred X.

1999-05-01

The percentage of the structural Fe(II) in clay minerals that is readily oxidized to Fe(III) upon contact with atmospheric oxygen was determined across the downcore tan-green color change in Peru Basin sediments. This latent fraction of reactive Fe(II) was only found in the green strata, where it proved to be large enough to constitute a deep reaction layer with respect to the pore water O 2 and NO 3-. Large variations were detected in the proportion of the reactive Fe(II) concentration to the organic matter content along core profiles. Hence, the commonly observed tan-green color change in marine sediments marks the top of a reactive Fe(II) layer, which may represent the major barrier to the movement of oxidation fronts in pelagic subsurface sediments. This is also demonstrated by numerical model simulations. The findings imply that geochemical barriers to pore water oxidation fronts form diagenetically in the sea floor wherever the stage of iron reduction is reached, provided that the sediments contain a significant amount of structural iron in clay minerals.

Genetic legacy of the deep subsurface recorded in the outflow channel of a terrestrial serpentinizing seep (Luzon, the Philippines)

NASA Astrophysics Data System (ADS)

Woycheese, K. M.; Meyer-Dombard, D. R.; Cardace, D.; Arcilla, C. A.

2014-12-01

The deep subsurface microbial community represents the largest biome on Earth, yet accessing this deep biosphere is challenging. Fluids seep along fractures from aquifers that may support diverse microbial communities, living off hydrogen gas generated by radiolysis, serpentinization, or thermogenic reactions. A serpentinizing seep, emanating fluids as high as pH 11.27, was found to accrete meters-long carbonate terraces in the Zambales ophiolite range (Luzon, the Philippines). Samples were collected at several locations along the Poon Bato (PB) River, focusing primarily on the pools and terraces formed by carbonate rimstone (Figure 1). As serpentinizing fluids are exposed to the atmosphere, dynamic niches are established in surface sediments. We propose that the high pH, reducing, high Ca+2 fluid pool terraces reflect remnants of deep subsurface microbial communities, based on high-throughput 16S rRNA sequencing data. In total, eight samples were collected for environmental DNA analysis. Post-sequence analysis revealed a total of 927126 counts, with an average of 115890.75 counts per sample. Many taxa aligned with cultured representatives of serpentinizing seep-associated taxa, including Bacteroidetes, Clostrida, Chloroflexi, Methylococcales, and Xanthomonadales. Geochemical data indicates an average fluid temperature of 28.9°C, and pH that varies from 9.22-11.27. Total carbon wt.% of solids was highest in a shallow pool shaped by boulders, where calcite precipitation occurred over nearly every surface. Dissolved oxygen (DO%) was highest at PB1 main pool (60%), although a calcite skin had formed along the air-water interface. Dissolved inorganic carbon (DIC) at PB1 main pool was 1.3 ppm, while at PB2 main pool, the DIC was higher (6.0 ppm). The lack of calcite skin may allow more direct access to atmospheric carbon dioxide at PB2. The isotopic value of carbon-13 was depleted at PB1 relative to PB2 (δ13C VPDB -25.4 ‰ versus δ13C VPDB ‰ -17.5, respectively). The DOC concentration at PB1 main pool was 0.3 ppm and 1.15 ppm at PB2. Given the low DIC concentrations at PB1, it is suggested that heterotrophy may dominate over autotrophy in the system. This suggests that the highly reducing, high pH fluids emanating from fluid seeps at Poon Bato influence surface communities via inundation with serpentinizing fluid.

Taxonomic study of aromatic-degrading bacteria from deep-terrestrial-subsurface sediments and description of Sphingomonas aromaticivorans sp. nov., Sphingomonas subterranea sp. nov., and Sphingomonas stygia sp. nov.

PubMed

Balkwill, D L; Drake, G R; Reeves, R H; Fredrickson, J K; White, D C; Ringelberg, D B; Chandler, D P; Romine, M F; Kennedy, D W; Spadoni, C M

1997-01-01

Phylogenetic analyses of 16S rRNA gene sequences by distance matrix and parsimony methods indicated that six strains of bacteria isolated from deep saturated Atlantic coastal plain sediments were closely related to the genus Sphingomonas. Five of the strains clustered with, but were distinct from, Sphingomonas capsulata, whereas the sixth strain was most closely related to Blastobacter natatorius. The five strains that clustered with S. capsulata, all of which could degrade aromatic compounds, were gram-negative, non-spore-forming, non-motile, rod-shaped organisms that produced small, yellow colonies on complex media. Their G + C contents ranged from 60.0 to 65.4 mol%, and the predominant isoprenoid quinone was ubiquinone Q-10. All of the strains were aerobic and catalase positive. Indole, urease, and arginine dihydrolase were not produced. Gelatin was not liquified, and glucose was not fermented. Sphingolipids were present in all strains; 2OH14:0 was the major hydroxy fatty acid, and 18:1 was a major constituent of cellular lipids. Acid was produced oxidatively from pentoses, hexoses, and disaccharides, but not from polyalcohols and indole. All of these characteristics indicate that the five aromatic-degrading strains should be placed in the genus Sphingomonas as currently defined. Phylogenetic analysis of 16S rRNA gene sequences, DNA-DNA reassociation values, BOX-PCR genomic fingerprinting, differences in cellular lipid composition, and differences in physiological traits all indicated that the five strains represent three previously undescribed Sphingomonas species. Therefore, we propose the following new species: Sphingomonas aromaticivorans (type strain, SMCC F199), Sphingomonas subterranea (type strain, SMCC B0478), and Sphingomonas stygia (type strain, SMCC B0712).

Isoprenoid quinones resolve the stratification of microbial redox processes in a biogeochemical continuum from the photic zone to deep anoxic sediments of the Black Sea.

PubMed

Becker, Kevin W; Elling, Felix J; Schröder, Jan M; Lipp, Julius S; Goldhammer, Tobias; Zabel, Matthias; Elvert, Marcus; Overmann, Jörg; Hinrichs, Kai-Uwe

2018-03-09

The stratified water column of the Black Sea serves as a model ecosystem for studying the interactions of microorganisms with major biogeochemical cycles. Here we provide detailed analysis of isoprenoid quinones to study microbial redox processes in the ocean. In a continuum from the photic zone through the chemocline into deep anoxic sediments of the southern Black Sea, diagnostic quinones and inorganic geochemical parameters indicate niche segregation between redox processes and corresponding shifts in microbial community composition. Quinones specific for oxygenic photosynthesis and aerobic respiration dominate oxic waters, while quinones associated with thaumarchaeal ammonia-oxidation and bacterial methanotrophy, respectively, dominate a narrow interval in suboxic waters. Quinone distributions indicate highest metabolic diversity within the anoxic zone, with anoxygenic photosynthesis being a major process in its photic layer. In the dark anoxic layer, quinone profiles indicate occurrence of bacterial sulfur and nitrogen cycling, archaeal methanogenesis, and archaeal methanotrophy. Multiple novel ubiquinone isomers, possibly originating from unidentified intra-aerobic anaerobes, occur in this zone. The respiration modes found in the anoxic zone continue into shallow subsurface sediments, but quinone abundances rapidly decrease within the upper 50 cm below sea floor, reflecting the transition to lower energy availability. In the deep subseafloor sediments, quinone distributions and geochemical profiles indicate archaeal methanogenesis/methanotrophy and potentially bacterial fermentative metabolisms. We observed that sedimentary quinone distributions track lithology, which supports prior hypotheses that deep biosphere community composition and metabolisms are determined by environmental conditions during sediment deposition. Importance Microorganisms play crucial roles in global biogeochemical cycles. Yet, we have only a fragmentary understanding of the diversity of microorganisms and their metabolisms, as the majority remains uncultured. Thus, culture-independent approaches are critical for determining microbial diversity and active metabolic processes. In order to resolve the stratification of microbial communities in the Black Sea, we comprehensively analyzed redox process-specific isoprenoid quinone biomarkers in a unique continuous record from the photic zone through the chemocline into anoxic subsurface sediments. We describe an unprecedented quinone diversity that allowed us to detect distinct biogeochemical processes including oxygenic photosynthesis, archaeal ammonia oxidation, aerobic methanotrophy and anoxygenic photosynthesis in defined geochemical zones. Copyright © 2018 American Society for Microbiology.

Microbial Metagenomics Reveals Climate-Relevant Subsurface Biogeochemical Processes.

PubMed

Long, Philip E; Williams, Kenneth H; Hubbard, Susan S; Banfield, Jillian F

2016-08-01

Microorganisms play key roles in terrestrial system processes, including the turnover of natural organic carbon, such as leaf litter and woody debris that accumulate in soils and subsurface sediments. What has emerged from a series of recent DNA sequencing-based studies is recognition of the enormous variety of little known and previously unknown microorganisms that mediate recycling of these vast stores of buried carbon in subsoil compartments of the terrestrial system. More importantly, the genome resolution achieved in these studies has enabled association of specific members of these microbial communities with carbon compound transformations and other linked biogeochemical processes-such as the nitrogen cycle-that can impact the quality of groundwater, surface water, and atmospheric trace gas concentrations. The emerging view also emphasizes the importance of organism interactions through exchange of metabolic byproducts (e.g., within the carbon, nitrogen, and sulfur cycles) and via symbioses since many novel organisms exhibit restricted metabolic capabilities and an associated extremely small cell size. New, genome-resolved information reshapes our view of subsurface microbial communities and provides critical new inputs for advanced reactive transport models. These inputs are needed for accurate prediction of feedbacks in watershed biogeochemical functioning and their influence on the climate via the fluxes of greenhouse gases, CO2, CH4, and N2O. Copyright © 2016 Elsevier Ltd. All rights reserved.

Pre-aged plant waxes in tropical lake sediments and their influence on the chronology of molecular paleoclimate proxy records

NASA Astrophysics Data System (ADS)

Douglas, Peter M. J.; Pagani, Mark; Eglinton, Timothy I.; Brenner, Mark; Hodell, David A.; Curtis, Jason H.; Ma, Keith F.; Breckenridge, Andy

2014-09-01

Sedimentary records of plant-wax hydrogen (δDwax) and carbon (δ13Cwax) stable isotopes are increasingly applied to infer past climate change. Compound-specific radiocarbon analyses, however, indicate that long time lags can occur between the synthesis of plant waxes and their subsequent deposition in marginal marine sediments. The influence of these time lags on interpretations of plant-wax stable isotope records is presently unconstrained, and it is unclear whether such time lags also affect lacustrine sediments. We present compound-specific radiocarbon (14Cwax) data for n-alkanoic acid plant waxes (n-C26 to n-C32) from: (1) a sediment core from Lake Chichancanab, Yucatan Peninsula, Mexico, (2) soils in the Lake Chichancanab catchment, and (3) surface sediments from three other lakes in southeastern Mexico and northern Guatemala. 14Cwax ages in the surface sediments are consistently older than modern, and may be negatively correlated with mean annual precipitation and positively correlated with lake catchment area. 14Cwax ages in soils surrounding Lake Chichancanab increase with soil depth, consistent with deep, subsoil horizons being the primary source of lacustrine aged plant waxes, which are likely delivered to lake sediments through subsurface transport. Plant waxes in the Lake Chichancanab core are 350-1200 years older than corresponding ages of bulk sediment deposition, determined by 14C dates on terrestrial plant macrofossils in the core. A δDwax time series is in closer agreement with other regional proxy hydroclimate records when a plant-wax 14C age model is applied, as opposed to the macrofossil-based core chronology. Inverse modeling of plant-wax age distribution parameters suggests that plant waxes in the Lake Chichancanab sediment core derive predominantly from millennial-age soil carbon pools that exhibit relatively little age variance (<200 years). Our findings demonstrate that high-temporal-resolution climate records inferred from stable isotope measures on plant waxes in lacustrine sediments may suffer from possible chronologic distortions as a consequence of long residence times of plant waxes in soils. They also underscore the importance of direct radiocarbon dating of these organic molecules.

In situ Detection of Microbial Life in the Deep Biosphere in Igneous Ocean Crust.

PubMed

Salas, Everett C; Bhartia, Rohit; Anderson, Louise; Hug, William F; Reid, Ray D; Iturrino, Gerardo; Edwards, Katrina J

2015-01-01

The deep biosphere is a major frontier to science. Recent studies have shown the presence and activity of cells in deep marine sediments and in the continental deep biosphere. Volcanic lavas in the deep ocean subsurface, through which substantial fluid flow occurs, present another potentially massive deep biosphere. We present results from the deployment of a novel in situ logging tool designed to detect microbial life harbored in a deep, native, borehole environment within igneous oceanic crust, using deep ultraviolet native fluorescence spectroscopy. Results demonstrate the predominance of microbial-like signatures within the borehole environment, with densities in the range of 10(5) cells/mL. Based on transport and flux models, we estimate that such a concentration of microbial cells could not be supported by transport through the crust, suggesting in situ growth of these communities.

Origin Of Methane Gas And Migration Through The Gas Hydrate Stability Zone Beneath The Permafrost Zone

NASA Astrophysics Data System (ADS)

Uchida, T.; Waseda, A.; Namikawa, T.

2005-12-01

In 1998 and 2002 Mallik wells were drilled at Mackenzie Delta in the Canadian Arctic that clarified the characteristics of gas hydrate-dominant sandy layers at depths from 890 to 1110 m beneath the permafrost zone. Continuous downhole well log data as well as visible gas hydrates have confirmed pore-space hydrate as intergranular pore filling within sandy layers whose saturations are up to 80% in pore volume, but muddy sediments scarcely contain. Plenty of gas hydrate-bearing sand core samples have been obtained from the Mallik wells. According to grain size distributions pore-space hydrate is dominant in medium- to very fine-grained sandy strata. Methane gas accumulation and original pore space large enough to occur within host sediments may be required for forming highly saturated gas hydrate in pore system. The distribution of a porous and coarser-grained host rock should be one of the important factors to control the occurrence of gas hydrate, as well as physicochemical conditions. Subsequent analyses in sedimentology and geochemistry performed on gas hydrate-bearing sandy core samples also revealed important geologic and sedimentological controls on the formation and concentration of natural gas hydrate. This appears to be a similar mode for conventional oil and gas accumulations. It is necessary for investigating subsurface fluid flow behaviors to evaluate both porosity and permeability of gas hydrate-bearing sandy sediments, and the measurements of water permeability for them indicate that highly saturated sands may have permeability of a few millidarcies. The isotopic data of methane show that hydrocarbon gas contained in gas hydrate is generated by thermogenic decomposition of kerogen in deep mature sediments. Based on geochemical and geological data, methane is inferred to migrate upward closely associated with pore water hundreds of meters into and through the hydrate stability zone partly up to the permafrost zone and the surface along faults and permeable sandy pathways. It should be remarked that there are many similar features in appearance and characteristics between the terrestrial and deep marine areas such as Nankai Trough with observations of well-interconnected and highly saturated pore-space hydrate.

Anaerobic consortia of fungi and sulfate reducing bacteria in deep granite fractures.

PubMed

Drake, Henrik; Ivarsson, Magnus; Bengtson, Stefan; Heim, Christine; Siljeström, Sandra; Whitehouse, Martin J; Broman, Curt; Belivanova, Veneta; Åström, Mats E

2017-07-04

The deep biosphere is one of the least understood ecosystems on Earth. Although most microbiological studies in this system have focused on prokaryotes and neglected microeukaryotes, recent discoveries have revealed existence of fossil and active fungi in marine sediments and sub-seafloor basalts, with proposed importance for the subsurface energy cycle. However, studies of fungi in deep continental crystalline rocks are surprisingly few. Consequently, the characteristics and processes of fungi and fungus-prokaryote interactions in this vast environment remain enigmatic. Here we report the first findings of partly organically preserved and partly mineralized fungi at great depth in fractured crystalline rock (-740 m). Based on environmental parameters and mineralogy the fungi are interpreted as anaerobic. Synchrotron-based techniques and stable isotope microanalysis confirm a coupling between the fungi and sulfate reducing bacteria. The cryptoendolithic fungi have significantly weathered neighboring zeolite crystals and thus have implications for storage of toxic wastes using zeolite barriers.Deep subsurface microorganisms play an important role in nutrient cycling, yet little is known about deep continental fungal communities. Here, the authors show organically preserved and partly mineralized fungi at 740 m depth, and find evidence of an anaerobic fungi and sulfate reducing bacteria consortium.

Potential for Nitrogen Fixation and Nitrification in the Granite-Hosted Subsurface at Henderson Mine, CO

PubMed Central

Swanner, Elizabeth D.; Templeton, Alexis S.

2011-01-01

The existence of life in the deep terrestrial subsurface is established, yet few studies have investigated the origin of nitrogen that supports deep life. Previously, 16S rRNA gene surveys cataloged a diverse microbial community in subsurface fluids draining from boreholes 3000 feet deep at Henderson Mine, CO, USA (Sahl et al., 2008). The prior characterization of the fluid chemistry and microbial community forms the basis for the further investigation here of the source of NH4+. The reported fluid chemistry included N2, NH4+ (5–112 μM), NO2− (27–48 μM), and NO3− (17–72 μM). In this study, the correlation between low NH4+ concentrations in dominantly meteoric fluids and higher NH4+ in rock-reacted fluids is used to hypothesize that NH4+ is sourced from NH4+-bearing biotite. However, biotite samples from the host rocks and ore-body minerals were analyzed by Fourier transform infrared (FTIR) microscopy and none-contained NH4+. However, the nitrogenase-encoding gene nifH was successfully amplified from DNA of the fluid sample with high NH4+, suggesting that subsurface microbes have the capability to fix N2. If so, unregulated nitrogen fixation may account for the relatively high NH4+ concentrations in the fluids. Additionally, the amoA and nxrB genes for archaeal ammonium monooxygenase and nitrite oxidoreductase, respectively, were amplified from the high NH4+ fluid DNA, while bacterial amoA genes were not. Putative nitrifying organisms are closely related to ammonium-oxidizing Crenarchaeota and nitrite-oxidizing Nitrospira detected in other subsurface sites based upon 16S rRNA sequence analysis. Thermodynamic calculations underscore the importance of NH4+ as an energy source in a subsurface nitrification pathway. These results suggest that the subsurface microbial community at Henderson is adapted to the low nutrient and energy environment by their capability of fixing nitrogen, and that fixed nitrogen may support subsurface biomass via nitrification. PMID:22190904

Terrestrial Biomarkers for Early Life on Earth as Analogs for Possible Martian Life Forms: Examples of Minerally Replaced Bacteria and Biofilms From the 3.5 - 3.3-Ga Barberton Greenstone Belt, South Africa

NASA Technical Reports Server (NTRS)

Westall, F.; McKay, D. S.; Gibson, E. K.; deWit, M. J.; Dann, J.; Gerneke, D.; deRonde, C. E. J.

1998-01-01

The search for extraterrestrial life and especially martian life hinges on a variety of methods used to identify vestiges of what we could recognize as life, including chemical signatures, morphological fossils, and biogenic precipitates. Although the possibility of extant life on Mars (subsurface) is being considered, most exploration efforts may be directed toward the search for fossil life. Geomorphological evidence points to a warmer and wetter Mars early on in its history, a scenario that encourages comparison with the early Earth. For this reason, study of the early terrestrial life forms and environment in which they lived may provide clues as to how to search for extinct martian life. As a contribution to the early Archean database of terrestrial microfossils, we present new data on morphological fossils from the 3.5-3.3-Ga Barberton greenstone belt (BGB), South Africa. This study underlines the variety of fossil types already present in some of the oldest, best-preserved terrestrial sediments, ranging from minerally replaced bacteria and bacteria molds of vaRious morphologies (coccoid, coccobacillus, bacillus) to minerally replaced biofilm. Biofilm or extracellular polymeric substance (EPS) is produced by bacteria and appears to be more readily fossilisable than bacteria themselves. The BGB fossils occur in shallow water to subaerial sediments interbedded with volcanic lavas, the whole being deposited on oceanic crust. Penecontemporaneous silicification of sediments and volcanics resulted in the chertification of the rocks, which were later subjected to low-grade metamorphism (lower greenschist).

Microbial Ecosystems from the Deepest Regions of the Terrestrial Deep Biosphere

NASA Astrophysics Data System (ADS)

Moser, D. P.

2011-12-01

Although recent discoveries from four continents support the existence of microbial ecosystems across vast regions of our planet's inner space, very little is known about the abundance, distribution, diversity, or ultimate depth limit of subsurface microbial life. These deep lithospheric inhabitants must contend with a variety of potential challenges including high temperature, pressure and salinity, extreme isolation, and low energy flux. Interestingly, although deep microbial ecosystems are assumed to be energy and nutrient limited, it is often difficult to identify any one limiting substrate and the energy for deep life is often present in relative abundance (e.g. as geologically-produced hydrogen or other reduced gases). Recently, the concept of radiation-supported deep microbial ecosystems has gained traction in the literature. In particular, one bacterium, a Firmicute denoted Candidatus Desulforudis audaxviator, has been shown to be prominent, and in cases dominate, in deep fracture fluids from across the Witwatersrand basin of South Africa, where it appears to persist by utilizing H2 and SO42- derived from radiochemical reactions in U-rich host rock. Until recently, these mines were thought to define the geographic limit of this genus and species; however, our recent North American detection of D. audaxviator in radioactive subsurface water resulting from underground nuclear tests both supports earlier assertions concerning the radiochemical lifestyle of D. audaxviator and greatly expands its range. Results such as these suggest that novel modes of life operating without inputs from the photosphere are possible, and thus may have implications for the likelihood of detecting life off the Earth (e.g. in the Martian subsurface). In addition to underground nuclear detonation cavities, this talk will consider insights gained from ongoing microbial ecology assessments from several to date unexplored deep ecosystems accessed via deep mines in the Black Hills (USA) and Canadian Shield (Canada) and exploratory boreholes in the Southern Great Basin (USA). The tantalizing possibility that several of these new potential habitats have exceeded some limit for life will be also be explored.

Biogeographic congruency among bacterial communities from terrestrial sulfidic springs

PubMed Central

Headd, Brendan; Engel, Annette S.

2014-01-01

Terrestrial sulfidic springs support diverse microbial communities by serving as stable conduits for geochemically diverse and nutrient-rich subsurface waters. Microorganisms that colonize terrestrial springs likely originate from groundwater, but may also be sourced from the surface. As such, the biogeographic distribution of microbial communities inhabiting sulfidic springs should be controlled by a combination of spring geochemistry and surface and subsurface transport mechanisms, and not necessarily geographic proximity to other springs. We examined the bacterial diversity of seven springs to test the hypothesis that occurrence of taxonomically similar microbes, important to the sulfur cycle, at each spring is controlled by geochemistry. Complementary Sanger sequencing and 454 pyrosequencing of 16S rRNA genes retrieved five proteobacterial classes, and Bacteroidetes, Chlorobi, Chloroflexi, and Firmicutes phyla from all springs, which suggested the potential for a core sulfidic spring microbiome. Among the putative sulfide-oxidizing groups (Epsilonproteobacteria and Gammaproteobacteria), up to 83% of the sequences from geochemically similar springs clustered together. Abundant populations of Hydrogenimonas-like or Sulfurovum-like spp. (Epsilonproteobacteria) occurred with abundant Thiothrix and Thiofaba spp. (Gammaproteobacteria), but Arcobacter-like and Sulfurimonas spp. (Epsilonproteobacteria) occurred with less abundant gammaproteobacterial populations. These distribution patterns confirmed that geochemistry rather than biogeography regulates bacterial dominance at each spring. Potential biogeographic controls were related to paleogeologic sedimentation patterns that could control long-term microbial transport mechanisms that link surface and subsurface environments. Knowing the composition of a core sulfidic spring microbial community could provide a way to monitor diversity changes if a system is threatened by anthropogenic processes or climate change. PMID:25250021

Generation of sedimentary fabrics and facies by repetitive excavation and storm infilling of burrow networks Holocene of south Florida and Caicos Platform, B. W. I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tedesco, L.P.; Wanless, H.R.

Excavation of deep, open burrow networks and subsequent infilling with sediment from the surface produces an entirely new sedimentary deposit and results in obliteration to severe diagenetic transformation of precursor depositional facies. Repetitive excavation and infilling is responsible for creating the preserved depositional facies of many marine deposits. Excavating burrowers occur from intertidal to abyssal depths, and are important throughout the Phanerozoic. The repetitive coupling of deep, open burrow excavation with subsequent storm sediment infilling of open burrow networks is a gradual process that ultimately results in the loss of the original deposit and the generation of new lithologies, fabricsmore » and facies. The new lithologies are produced in the subsurface and possess fabrics, textures and skeletal assemblages that are not a direct reflection of either precursor facies or the surficial depositional conditions. Sedimentary facies generated by repetitive burrow excavation and infilling commonly are massively bedded and generally are mottled skeletal packstones. Skeletal grains usually are well-preserved and coarser components are concentrated in burrow networks, pockets and patches. The coarse skeletal components of burrow-generated facies are a mixture of coarse bioclasts from the precursor facies and both the coarse and fine skeletal material introduced from the sediment surface. Many so-called bioturbated or massive facies may, in fact, be primary depositional facies generated in the subsurface and represent severe diagenetic transformation of originally deposited sequences. In addition, mudstones and wackestones mottled with packstone patches may record storm sedimentation.« less

Microbial Community Responses to Organophosphate Substrate Additions in Contaminated Subsurface Sediments

PubMed Central

Martinez, Robert J.; Wu, Cindy H.; Beazley, Melanie J.; Andersen, Gary L.; Conrad, Mark E.; Hazen, Terry C.; Taillefert, Martial; Sobecky, Patricia A.

2014-01-01

Background Radionuclide- and heavy metal-contaminated subsurface sediments remain a legacy of Cold War nuclear weapons research and recent nuclear power plant failures. Within such contaminated sediments, remediation activities are necessary to mitigate groundwater contamination. A promising approach makes use of extant microbial communities capable of hydrolyzing organophosphate substrates to promote mineralization of soluble contaminants within deep subsurface environments. Methodology/Principal Findings Uranium-contaminated sediments from the U.S. Department of Energy Oak Ridge Field Research Center (ORFRC) Area 2 site were used in slurry experiments to identify microbial communities involved in hydrolysis of 10 mM organophosphate amendments [i.e., glycerol-2-phosphate (G2P) or glycerol-3-phosphate (G3P)] in synthetic groundwater at pH 5.5 and pH 6.8. Following 36 day (G2P) and 20 day (G3P) amended treatments, maximum phosphate (PO4 3−) concentrations of 4.8 mM and 8.9 mM were measured, respectively. Use of the PhyloChip 16S rRNA microarray identified 2,120 archaeal and bacterial taxa representing 46 phyla, 66 classes, 110 orders, and 186 families among all treatments. Measures of archaeal and bacterial richness were lowest under G2P (pH 5.5) treatments and greatest with G3P (pH 6.8) treatments. Members of the phyla Crenarchaeota, Euryarchaeota, Bacteroidetes, and Proteobacteria demonstrated the greatest enrichment in response to organophosphate amendments and the OTUs that increased in relative abundance by 2-fold or greater accounted for 9%–50% and 3%–17% of total detected Archaea and Bacteria, respectively. Conclusions/Significance This work provided a characterization of the distinct ORFRC subsurface microbial communities that contributed to increased concentrations of extracellular phosphate via hydrolysis of organophosphate substrate amendments. Within subsurface environments that are not ideal for reductive precipitation of uranium, strategies that harness microbial phosphate metabolism to promote uranium phosphate precipitation could offer an alternative approach for in situ sequestration. PMID:24950228

Pollen and spores date origin of rift basins from Texas to nova scotia as early late triassic.

PubMed

Traverse, A

1987-06-12

Palynological studies of the nonmarine Newark Supergroup of eastern North America and of rift basins in the northern Gulf of Mexico facilitate correlation with well-dated marine sections of Europe. New information emphasizes the chronological link between the Newark basins and a Gulf of Mexico basin and their common history in the rifting of North America from Pangea. Shales from the subsurface South Georgia Basin are shown to be of late Karnian age (early Late Triassic). The known time of earliest sedimentation in the Culpeper Basin is extended from Norian (late Late Triassic) to mid-Karnian, and the date of earliest sedimentation in the Richmond and Deep River basins is moved to at least earliest Karnian, perhaps Ladinian. The subsurface Eagle Mills Formation in Texas and Arkansas has been dated palynologically as mid- to late Karnian. The oldest parts of the Newark Supergroup, and the Eagle Mills Formation, mostly began deposition in precursor rift basins that formed in Ladinian to early Karnian time. In the southern Newark basins, sedimentation apparently ceased in late Karnian but continued in the northern basins well into the Jurassic, until genesis of the Atlantic ended basin sedimentation.

Designing a network of critical zone observatories to explore the living skin of the terrestrial Earth

Treesearch

Susan L. Brantley; William H. McDowell; William E. Dietrich; Timothy S. White; Praveen Kumar; Suzanne P. Anderson; Jon Chorover; Kathleen Ann Lohse; Roger C. Bales; Daniel D. Richter; Gordon Grant; Jérôme Gaillardet

2017-01-01

The critical zone (CZ), the dynamic living skin of the Earth, extends from the top of the vegetative canopy through the soil and down to fresh bedrock and the bottom of the groundwater. All humans live in and depend on the CZ. This zone has three co-evolving surfaces: the top of the vegetative canopy, the ground surface, and a deep subsurface below which Earth’s...

Sulfur mass-independent fractionation in subsurface fracture waters indicates a long-standing sulfur cycle in Precambrian rocks.

PubMed

Li, L; Wing, B A; Bui, T H; McDermott, J M; Slater, G F; Wei, S; Lacrampe-Couloume, G; Lollar, B Sherwood

2016-10-27

The discovery of hydrogen-rich waters preserved below the Earth's surface in Precambrian rocks worldwide expands our understanding of the habitability of the terrestrial subsurface. Many deep microbial ecosystems in these waters survive by coupling hydrogen oxidation to sulfate reduction. Hydrogen originates from water-rock reactions including serpentinization and radiolytic decomposition of water induced by decay of radioactive elements in the host rocks. The origin of dissolved sulfate, however, remains unknown. Here we report, from anoxic saline fracture waters ∼2.4 km below surface in the Canadian Shield, a sulfur mass-independent fractionation signal in dissolved sulfate. We demonstrate that this sulfate most likely originates from oxidation of sulfide minerals in the Archaean host rocks through the action of dissolved oxidants (for example, HO · and H 2 O 2 ) themselves derived from radiolysis of water, thereby providing a coherent long-term mechanism capable of supplying both an essential electron donor (H 2 ) and a complementary acceptor (sulfate) for the deep biosphere.

Sulfur mass-independent fractionation in subsurface fracture waters indicates a long-standing sulfur cycle in Precambrian rocks

PubMed Central

Li, L.; Wing, B. A.; Bui, T. H.; McDermott, J. M.; Slater, G. F.; Wei, S.; Lacrampe-Couloume, G.; Lollar, B. Sherwood

2016-01-01

The discovery of hydrogen-rich waters preserved below the Earth's surface in Precambrian rocks worldwide expands our understanding of the habitability of the terrestrial subsurface. Many deep microbial ecosystems in these waters survive by coupling hydrogen oxidation to sulfate reduction. Hydrogen originates from water–rock reactions including serpentinization and radiolytic decomposition of water induced by decay of radioactive elements in the host rocks. The origin of dissolved sulfate, however, remains unknown. Here we report, from anoxic saline fracture waters ∼2.4 km below surface in the Canadian Shield, a sulfur mass-independent fractionation signal in dissolved sulfate. We demonstrate that this sulfate most likely originates from oxidation of sulfide minerals in the Archaean host rocks through the action of dissolved oxidants (for example, HO· and H2O2) themselves derived from radiolysis of water, thereby providing a coherent long-term mechanism capable of supplying both an essential electron donor (H2) and a complementary acceptor (sulfate) for the deep biosphere. PMID:27807346

Terrestrial Subsurface Ecosystem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilkins, Michael J.; Fredrickson, Jim K.

2015-10-15

The Earth’s crust is a solid cool layer that overlays the mantle, with a varying thickness of between 30-50 km on continental plates, and 5-10 km on oceanic plates. Continental crust is composed of a variety of igneous, metamorphic, and sedimentary rocks that weather and re-form over geologic cycles lasting millions to billions of years. At the crust surface, these weathered minerals and organic material combine to produce a variety of soils types that provide suitable habitats and niches for abundant microbial diversity (see Chapter 4). Beneath this soil zone is the subsurface. Once thought to be relatively free ofmore » microorganisms, recent estimates have calculated that between 1016-1017 g C biomass (2-19% of Earth’s total biomass) may be present in this environment (Whitman et al., 1998;McMahon and Parnell, 2014). Microbial life in the subsurface exists across a wide range of habitats: in pores associated with relatively shallow unconsolidated aquifer sediments to fractures in bedrock formations that are more than a kilometer deep, where extreme lithostatic pressures and temperatures are encountered. While these different environments contain varying physical and chemical conditions, the absence of light is a constant. Despite this, diverse physiologies and metabolisms enable microorganisms to harness energy and carbon for growth in water-filled pore spaces and fractures. Carbon and other element cycles are driven by microbial activity, which has implications for both natural processes and human activities in the subsurface, e.g., bacteria play key roles in both hydrocarbon formation and degradation. Hydrocarbons are a major focus for human utilization of the subsurface, via oil and gas extraction and potential geologic CO2 sequestration. The subsurface is also utilized or being considered for sequestered storage of high-level radioactive waste from nuclear power generation and residual waste from past production of weapons grade nuclear materials. While our understanding of the subsurface is continually improving, it is clear that only a small fraction of microbial habitats have been sampled and studied. In this chapter, we will discuss these studies in the context of the distribution of microbial life in the subsurface, the stresses that microorganisms must overcome to survive in these environments, and the metabolic strategies that are employed to harness energy in a region of the planet far-removed from sunlight. Finally, we will consider both beneficial and deleterious effects of microbial activity in the subsurface on human activities in this environment.« less

Predominance of Viable Spore-Forming Piezophilic Bacteria in High-Pressure Enrichment Cultures from ~1.5 to 2.4 km-Deep Coal-Bearing Sediments below the Ocean Floor

PubMed Central

Fang, Jiasong; Kato, Chiaki; Runko, Gabriella M.; Nogi, Yuichi; Hori, Tomoyuki; Li, Jiangtao; Morono, Yuki; Inagaki, Fumio

2017-01-01

Phylogenetically diverse microorganisms have been observed in marine subsurface sediments down to ~2.5 km below the seafloor (kmbsf). However, very little is known about the pressure-adapted and/or pressure-loving microorganisms, the so called piezophiles, in the deep subseafloor biosphere, despite that pressure directly affects microbial physiology, metabolism, and biogeochemical processes of carbon and other elements in situ. In this study, we studied taxonomic compositions of microbial communities in high-pressure incubated sediment, obtained during the Integrated Ocean Drilling Program (IODP) Expedition 337 off the Shimokita Peninsula, Japan. Analysis of 16S rRNA gene-tagged sequences showed that members of spore-forming bacteria within Firmicutes and Actinobacteria were predominantly detected in all enrichment cultures from ~1.5 to 2.4 km-deep sediment samples, followed by members of Proteobacteria, Acidobacteria, and Bacteroidetes according to the sequence frequency. To further study the physiology of the deep subseafloor sedimentary piezophilic bacteria, we isolated and characterized two bacterial strains, 19R1-5 and 29R7-12, from 1.9 and 2.4 km-deep sediment samples, respectively. The isolates were both low G+C content, gram-positive, endospore-forming and facultative anaerobic piezophilic bacteria, closely related to Virgibacillus pantothenticus and Bacillus subtilis within the phylum Firmicutes, respectively. The optimal pressure and temperature conditions for growth were 20 MPa and 42°C for strain 19R1-5, and 10 MPa and 43°C for strain 29R7-12. Bacterial (endo)spores were observed in both the enrichment and pure cultures examined, suggesting that these piezophilic members were derived from microbial communities buried in the ~20 million-year-old coal-bearing sediments after the long-term survival as spores and that the deep biosphere may host more abundant gram-positive spore-forming bacteria and their spores than hitherto recognized. PMID:28220112

Predominance of Viable Spore-Forming Piezophilic Bacteria in High-Pressure Enrichment Cultures from ~1.5 to 2.4 km-Deep Coal-Bearing Sediments below the Ocean Floor.

PubMed

Fang, Jiasong; Kato, Chiaki; Runko, Gabriella M; Nogi, Yuichi; Hori, Tomoyuki; Li, Jiangtao; Morono, Yuki; Inagaki, Fumio

2017-01-01

Phylogenetically diverse microorganisms have been observed in marine subsurface sediments down to ~2.5 km below the seafloor (kmbsf). However, very little is known about the pressure-adapted and/or pressure-loving microorganisms, the so called piezophiles, in the deep subseafloor biosphere, despite that pressure directly affects microbial physiology, metabolism, and biogeochemical processes of carbon and other elements in situ . In this study, we studied taxonomic compositions of microbial communities in high-pressure incubated sediment, obtained during the Integrated Ocean Drilling Program (IODP) Expedition 337 off the Shimokita Peninsula, Japan. Analysis of 16S rRNA gene-tagged sequences showed that members of spore-forming bacteria within Firmicutes and Actinobacteria were predominantly detected in all enrichment cultures from ~1.5 to 2.4 km-deep sediment samples, followed by members of Proteobacteria, Acidobacteria, and Bacteroidetes according to the sequence frequency. To further study the physiology of the deep subseafloor sedimentary piezophilic bacteria, we isolated and characterized two bacterial strains, 19R1-5 and 29R7-12, from 1.9 and 2.4 km-deep sediment samples, respectively. The isolates were both low G+C content, gram-positive, endospore-forming and facultative anaerobic piezophilic bacteria, closely related to Virgibacillus pantothenticus and Bacillus subtilis within the phylum Firmicutes, respectively. The optimal pressure and temperature conditions for growth were 20 MPa and 42°C for strain 19R1-5, and 10 MPa and 43°C for strain 29R7-12. Bacterial (endo)spores were observed in both the enrichment and pure cultures examined, suggesting that these piezophilic members were derived from microbial communities buried in the ~20 million-year-old coal-bearing sediments after the long-term survival as spores and that the deep biosphere may host more abundant gram-positive spore-forming bacteria and their spores than hitherto recognized.

In situ Detection of Microbial Life in the Deep Biosphere in Igneous Ocean Crust

PubMed Central

Salas, Everett C.; Bhartia, Rohit; Anderson, Louise; Hug, William F.; Reid, Ray D.; Iturrino, Gerardo; Edwards, Katrina J.

2015-01-01

The deep biosphere is a major frontier to science. Recent studies have shown the presence and activity of cells in deep marine sediments and in the continental deep biosphere. Volcanic lavas in the deep ocean subsurface, through which substantial fluid flow occurs, present another potentially massive deep biosphere. We present results from the deployment of a novel in situ logging tool designed to detect microbial life harbored in a deep, native, borehole environment within igneous oceanic crust, using deep ultraviolet native fluorescence spectroscopy. Results demonstrate the predominance of microbial-like signatures within the borehole environment, with densities in the range of 105 cells/mL. Based on transport and flux models, we estimate that such a concentration of microbial cells could not be supported by transport through the crust, suggesting in situ growth of these communities. PMID:26617595

Marine Subsurface Microbial Communities Across a Hydrothermal Gradient in Okinawa Trough Sediments

NASA Astrophysics Data System (ADS)

Brandt, L. D.; Hser Wah Saw, J.; Ettema, T.; House, C. H.

2015-12-01

IODP Expedition 331 to the Okinawa backarc basin provided an opportunity to study the microbial stratigraphy within the sediments surrounding a hydrothermal vent. The Okinawa backarc basin is a sedimented region of the seafloor located on a continental margin, and also hosts a hydrothermal network within the subsurface. Site C0014 within the Iheya North hydrothermal field is located 450 m east of the active vent and has a surface temperature of 5°C with no evidence of hydrothermal alteration within the top 10 meters below sea floor (mbsf). Temperature increases with depth at an estimated rate of 3°C/m and transitions from non-hydrothermal margin sediments to a hydrothermally altered regime below 10 mbsf. In this study, we utilized deep 16S rRNA sequencing of DNA from IODP Expedition 331 Site C0014 sediment horizons in order to assess diversity throughout the sediment column as well as determine the potential limits of the biosphere. Analysis of the amplicon data shows a shift over 15 mbsf from a heterogeneous community of cosmopolitan marine subsurface taxa toward an archaeal-dominated community in the deepest horizons of the predicted biosphere. Notably, the phylum Chloroflexi represents a substantial taxon through most horizons, where it appears to be replaced below 10 mbsf by punctuations of thermophilic and methanotrophic Archaea and Miscellaneous Crenarchaeotic Group abundances. DNA from the aforementioned transition horizons was further analyzed using metagenomic sequencing. Preliminary taxonomic analysis of the metagenomic data agrees well with amplicon data in capturing the shift in relative abundance of Archaea increasing with depth. Additionally, reverse gyrase, a gene found exclusively in hyperthermophilic microorganisms, was recovered only in the metagenome of the deepest horizon. A BLAST search of this protein sequence against the GenBank non-redudnant protein database produced top hits with reverse gyrase from Thermococcus and Pyrococcus, which are known thermophiles. Up until now, thermophiles and hyperthermophiles have been studied in cultured hydrothermal vent fluid samples, or have been identified from 16S rRNA taxonomic analyses. These recovered genes provide direct evidence for a pervasive subsurface hyperthermophilic biosphere in off-axis hydrothermal sediments.

Organic matter in sediments of an acidic mining lake as assessed by lipid analysis. Part I: fatty acids.

PubMed

Poerschmann, Juergen; Koschorreck, Matthias; Górecki, Tadeusz

2012-01-01

Fatty acid (FA) patterns of sediments collected from the bottom of an acidic mine pit lake (AML) at different depths (surface sediment: 0 to 1cm; deep sediment: 4 to 5 cm) were studied to characterize microbial communities and the sources of sedimentary organic matter (SOM). Studies were performed on the molecular level utilizing source-specific, diagnostic FA biomarkers. The biomarker-based approach has been used widely in marine sediment studies, but has not been applied for sediments from AMLs so far. Combined FA concentrations in the surface sediment were higher compared to those in the deep sediment (497 vs. 127 μg g(-1)d.w., respectively). This was related to deposition of autochthonous biomass and higher terrestrial plants onto the surface sediment, as well as--to lesser extent--with higher bacterial activity on the sediment-water interface. The FA distribution in both sediments was characterized by a strong even-over-odd preference and was bimodal in nature: there was a cluster at nC(14)-nC(18) characteristic of chiefly autochthonous (algal and bacterial) SOM production, and another cluster at nC(22-28) related to input from higher plants. The FA distribution in the surface sediment pointed to higher terrestrial input compared to autochthonous contribution to SOM (67%:33%) as an estimate. Fingerprinting of viable bacteria was accomplished through signature FA markers including branched C(15) and C(17) surrogates, cyclopropanoic acids, 3-hydroxy (OH) acids and monounsaturated surrogates with unusual double bond localization. The abundance of Gram-negative bacteria was higher in the surface sediment as evidenced by total diagnostic 3-OH-fatty acids (37 μg g(-1) versus 25 μg g(-1)). Potential source taxa in both sediment layers included acidophilic iron- and sulfur-oxidizing bacteria including Acidithiobacillus ferrooxidans. High abundances of terminally branched C(15) and C(17) surrogates in both sediments pointed to sulfate- and iron-reducing bacteria. Signature FAs characteristic of methanotrophs were virtually lacking in both sediments. Copyright © 2011 Elsevier B.V. All rights reserved.

Close association of active nitrifiers with Beggiatoa mats covering deep-sea hydrothermal sediments.

PubMed

Winkel, Matthias; de Beer, Dirk; Lavik, Gaute; Peplies, Jörg; Mußmann, Marc

2014-06-01

Hydrothermal sediments in the Guaymas Basin are covered by microbial mats that are dominated by nitrate-respiring and sulphide-oxidizing Beggiatoa. The presence of these mats strongly correlates with sulphide- and ammonium-rich fluids venting from the subsurface. Because ammonium and oxygen form opposed gradients at the sediment surface, we hypothesized that nitrification is an active process in these Beggiatoa mats. Using biogeochemical and molecular methods, we measured nitrification and determined the diversity and abundance of nitrifiers. Nitrification rates ranged from 74 to 605 μmol N l(-1)  mat day(-1), which exceeded those previously measured in hydrothermal plumes and other deep-sea habitats. Diversity and abundance analyses of archaeal and bacterial ammonia monooxygenase subunit A genes, archaeal 16S ribosomal RNA pyrotags and fluorescence in situ hybridization confirmed that ammonia- and nitrite-oxidizing microorganisms were associated with Beggiatoa mats. Intriguingly, we observed cells of bacterial and potential thaumarchaeotal ammonia oxidizers attached to narrow, Beggiatoa-like filaments. Such a close spatial coupling of nitrification and nitrate respiration in mats of large sulphur bacteria is novel and may facilitate mat-internal cycling of nitrogen, thereby reducing loss of bioavailable nitrogen in deep-sea sediments. © 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.

Subsurface sediment contamination during borehole drilling with an air-actuated down-hole hammer.

PubMed

Malard, Florian; Datry, Thibault; Gibert, Janine

2005-10-01

Drilling methods can severely alter physical, chemical, and biological properties of aquifers, thereby influencing the reliability of water samples collected from groundwater monitoring wells. Because of their fast drilling rate, air-actuated hammers are increasingly used for the installation of groundwater monitoring wells in unconsolidated sediments. However, oil entrained in the air stream to lubricate the hammer-actuating device can contaminate subsurface sediments. Concentrations of total hydrocarbons, heavy metals (Cu, Ni, Cr, Zn, Pb, and Cd), and nutrients (particulate organic carbon, nitrogen, and phosphorus) were measured in continuous sediment cores recovered during the completion of a 26-m deep borehole drilled with a down-hole hammer in glaciofluvial deposits. Total hydrocarbons, Cu, Ni, Cr and particulate organic carbon (POC) were all measured at concentrations far exceeding background levels in most sediment cores. Hydrocarbon concentration averaged 124 +/- 118 mg kg(-1) dry sediment (n = 78 samples) with peaks at depths of 8, 14, and 20 m below the soil surface (maximum concentration: 606 mg kg(-1)). The concentrations of hydrocarbons, Cu, Ni, Cr, and POC were positively correlated and exhibited a highly irregular vertical pattern, that probably reflected variations in air loss within glaciofluvial deposits during drilling. Because the penetration of contaminated air into the formation is unpreventable, the representativeness of groundwater samples collected may be questioned. It is concluded that air percussion drilling has strong limitations for well installation in groundwater quality monitoring surveys.

Deglacial Tropical Atlantic subsurface warming links ocean circulation variability to the West African Monsoon.

PubMed

Schmidt, Matthew W; Chang, Ping; Parker, Andrew O; Ji, Link; He, Feng

2017-11-13

Multiple lines of evidence show that cold stadials in the North Atlantic were accompanied by both reductions in Atlantic Meridional Overturning Circulation (AMOC) and collapses of the West African Monsoon (WAM). Although records of terrestrial change identify abrupt WAM variability across the deglaciation, few studies show how ocean temperatures evolved across the deglaciation. To identify the mechanism linking AMOC to the WAM, we generated a new record of subsurface temperature variability over the last 21 kyr based on Mg/Ca ratios in a sub-thermocline dwelling planktonic foraminifera in an Eastern Equatorial Atlantic (EEA) sediment core from the Niger Delta. Our subsurface temperature record shows abrupt subsurface warming during both the Younger Dryas (YD) and Heinrich Event 1. We also conducted a new transient coupled ocean-atmosphere model simulation across the YD that better resolves the western boundary current dynamics and find a strong negative correlation between AMOC strength and EEA subsurface temperatures caused by changes in ocean circulation and rainfall responses that are consistent with the observed WAM change. Our combined proxy and modeling results provide the first evidence that an oceanic teleconnection between AMOC strength and subsurface temperature in the EEA impacted the intensity of the WAM on millennial time scales.

Saturated CO2 inhibits microbial processes in CO2-vented deep-sea sediments

NASA Astrophysics Data System (ADS)

de Beer, D.; Haeckel, M.; Neumann, J.; Wegener, G.; Inagaki, F.; Boetius, A.

2013-02-01

This study focused on biogeochemical processes and microbial activity in sediments of a natural deep-sea CO2 seepage area (Yonaguni Knoll IV hydrothermal system, Japan). The aim was to assess the influence of the geochemical conditions occurring in highly acidic and CO2 saturated sediments on sulphate reduction (SR) and anaerobic methane oxidation (AOM). Porewater chemistry was investigated from retrieved sediment cores and in situ by microsensor profiling. The sites sampled around a sediment-hosted hydrothermal CO2 vent were very heterogeneous in porewater chemistry, indicating a complex leakage pattern. Near the vents, droplets of liquid CO2 were observed to emanate from the sediments, and the pH reached approximately 4.5 in a sediment depth >6 cm, as determined in situ by microsensors. Methane and sulphate co-occurred in most sediment samples from the vicinity of the vents down to a depth of at least 3 m. However, SR and AOM were restricted to the upper 7-15 cm below seafloor, although neither temperature, low pH, nor the availability of methane and sulphate could be limiting microbial activity. We argue that the extremely high subsurface concentrations of dissolved CO2 (1000-1700 mM), through the ensuing high H2CO3 levels (approx. 1-2 mM) uncouples the proton-motive-force (PMF) and thus inhibits biological energy conservation by ATPase-driven phosphorylation. This limits life to the surface sediment horizons above the liquid CO2 phase, where less extreme conditions prevail. Our results may have to be taken into consideration in assessing the consequences of deep-sea CO2 sequestration on benthic element cycling and on the local ecosystem state.

Connectivity to the surface determines diversity patterns in subsurface aquifers of the Fennoscandian shield.

PubMed

Hubalek, Valerie; Wu, Xiaofen; Eiler, Alexander; Buck, Moritz; Heim, Christine; Dopson, Mark; Bertilsson, Stefan; Ionescu, Danny

2016-10-01

Little research has been conducted on microbial diversity deep under the Earth's surface. In this study, the microbial communities of three deep terrestrial subsurface aquifers were investigated. Temporal community data over 6 years revealed that the phylogenetic structure and community dynamics were highly dependent on the degree of isolation from the earth surface biomes. The microbial community at the shallow site was the most dynamic and was dominated by the sulfur-oxidizing genera Sulfurovum or Sulfurimonas at all-time points. The microbial community in the meteoric water filled intermediate aquifer (water turnover approximately every 5 years) was less variable and was dominated by candidate phylum OD1. Metagenomic analysis of this water demonstrated the occurrence of key genes for nitrogen and carbon fixation, sulfate reduction, sulfide oxidation and fermentation. The deepest water mass (5000 year old waters) had the lowest taxon richness and surprisingly contained Cyanobacteria. The high relative abundance of phylogenetic groups associated with nitrogen and sulfur cycling, as well as fermentation implied that these processes were important in these systems. We conclude that the microbial community patterns appear to be shaped by the availability of energy and nutrient sources via connectivity to the surface or from deep geological processes.

Geomorphic consequences of rapid deglaciation at Pasterze Glacier, Hohe Tauern Range, Austria, between 2010 and 2013 based on repeated terrestrial laser scanning data

NASA Astrophysics Data System (ADS)

Avian, M.; Kellerer-Pirklbauer, A.; Lieb, G. K.

2018-06-01

Since the end of the Little Ice Age around 1850 CE glaciers in the Alps have been receding dramatically. This study aimed to quantify and characterize the geomorphic and landform changes of a 0.9 km2 large proglacial area at the largest glacier in Austria (Pasterze Glacier, Austria, N 47°04‧, E 12°44‧). Point clouds from multiple terrestrial laserscanning (TLS) and different image data were used to quantify surface elevation changes and distinguish different types of erosional and depositional landforms during the period 2010-2013. Results indicate that the study area is characterized by a total volume loss of 1,309,000 m3. Excluding the area which was deglaciated, the volume loss equals 275,000 m3 in the period 2010-13. The decrease is related to sediment transfer out of study area and due to sediment-buried glacier ice which is slowly melting. The landform classification reveals that drift mantled slopes are most frequent (20.9% of the study area in 2013) next to ice contact terrace landforms (19.7%). In terms of vertical surface elevation changes, our results suggest distinguishing between 3 distinct domains within the study area: (i) a flat valley bottom area consisting of water/sandur areas and ice-cored landforms dominated by widespread subsurface ice melting and lateral fluvial (and thermal) erosion; (ii) a gently-sloping footslope area consisting of ice-contact sediments, former ice marginal channels and deep incised gullies with corresponding debris cones dominated by linear erosion and corresponding deposition; and (iii) a steep lateral slope area mainly built up of consolidated drift material with incised gullies dominated by linear erosion. Our results not only confirm the previously revealed high geomorphic activity for proglacial areas of alpine glaciers in terms of surface elevation variations, they also highlight that landforms might change substantially from one year to the next not only because of erosional/depositional processes, but also because of the melting of buried dead-ice bodies.

Patterns and drivers of bacterial α- and β-diversity across vertical profiles from surface to subsurface sediments.

PubMed

Luna, Gian Marco; Corinaldesi, Cinzia; Rastelli, Eugenio; Danovaro, Roberto

2013-10-01

We investigated the patterns and drivers of bacterial α- and β-diversity, along with viral and prokaryotic abundance and the carbon production rates, in marine surface and subsurface sediments (down to 1 m depth) in two habitats: vegetated sediments (seagrass meadow) and non-vegetated sediments. Prokaryotic abundance and production decreased with depth in the sediment, but cell-specific production rates and the virus-to-prokaryote ratio increased, highlighting unexpectedly high activity in the subsurface. The highest diversity was observed in vegetated sediments. Bacterial β-diversity between sediment horizons was high, and only a minor number of taxa was shared between surface and subsurface layers. Viruses significantly contributed to explain α- and β-diversity patterns. Despite potential limitations due to the only use of fingerprinting techniques, this study indicates that the coastal subsurface host highly active and diversified bacterial assemblages, that subsurface cells are more active than expected and that viruses promote β-diversity and stimulate bacterial metabolism in subsurface layers. The limited number of taxa shared between habitats, and between surface and subsurface sediment horizons, suggests that future investigations of the shallow subsurface will provide insights into the census of bacterial diversity, and the comprehension of the patterns and drivers of prokaryotic diversity in marine ecosystems. © 2013 John Wiley & Sons Ltd and Society for Applied Microbiology.

A promising tool for subsurface permafrost mapping-An application of airborne geophysics from the Yukon River Basin, Alaska

USGS Publications Warehouse

Abraham, Jared E.

2011-01-01

In the area of Fort Yukon, the AEM survey shows elevated resistivities extending to depth, likely indicative of thick permafrost. This depth corresponds well to observations from a borehole drilled in the area in the late 1990s, which detected permafrost to a depth of about 100 meters (Clark and others, 2009). In contrast to the area of Fort Yukon, the Yukon River and its floodplain are not associated with deep resistive sediments, suggesting a lack of deep permafrost, at least within the depth range of the AEM mapping (fig. 3).

Geochemical modeling of subsurface fluid generation in the Gulf of Cadiz

NASA Astrophysics Data System (ADS)

Schmidt, Christopher; Hensen, Christian; Wallmann, Klaus

2016-04-01

During RV METEOR cruise M86/5 in 2012 a number of deep-sea mud volcanoes were discovered at about 4500 m water depth west of the deformation front of the accretionary wedge in the Gulf of Cadiz (NE Atlantic). Fluid flow at these locations is mediated by an active strike-slip fault marking the transcurrent plate boundary between Africa and Eurasia. Geochemical signals of emanating fluids have been interpreted as being a mixture of various deep-sourced processes such as the alteration of oceanic crust, clay-mineral dehydration, and recrystallization of carbonaceous, Upper Jurassic sediments (Hensen et al. 2015). In the current study we present results of a geochemical reactive-transport model that was designed to simulate major fluid-affecting processes, such as the smectite to illite transformation or recrystallization of carbonates in order to provide a proof of concept. Preliminary results show that the model is able to reproduce pore water signatures (e.g. for chloride, strontium, 87Sr/86Sr) in subsurface sediments that are similar to those of MV fluids. Hensen, C., Scholz, F., Nuzzo, M., Valadares, V., Gràcia, E., Terrinha, P., Liebetrau, V., Kaul, N., Silva, S., Martínez-Loriente, S., Bartolome, R., Piñero, E., Magalhães, V.H., Schmidt, M., Weise, S.M., Cunha, M., Hilario, A., Perea, H., Rovelli, L. and Lackschewitz, K. (2015) Strike-slip faults mediate the rise of crustal-derived fluids and mud volcanism in the deep sea. Geology 43, 339-342.

New Bio-Indicators for Long Term Natural Attenuation of Monoaromatic Compounds in Deep Terrestrial Aquifers.

PubMed

Aüllo, Thomas; Berlendis, Sabrina; Lascourrèges, Jean-François; Dessort, Daniel; Duclerc, Dominique; Saint-Laurent, Stéphanie; Schraauwers, Blandine; Mas, Johan; Patriarche, Delphine; Boesinger, Cécile; Magot, Michel; Ranchou-Peyruse, Anthony

2016-01-01

Deep subsurface aquifers despite difficult access, represent important water resources and, at the same time, are key locations for subsurface engineering activities for the oil and gas industries, geothermal energy, and CO2 or energy storage. Formation water originating from a 760 m-deep geological gas storage aquifer was sampled and microcosms were set up to test the biodegradation potential of BTEX by indigenous microorganisms. The microbial community diversity was studied using molecular approaches based on 16S rRNA genes. After a long incubation period, with several subcultures, a sulfate-reducing consortium composed of only two Desulfotomaculum populations was observed able to degrade benzene, toluene, and ethylbenzene, extending the number of hydrocarbonoclastic-related species among the Desulfotomaculum genus. Furthermore, we were able to couple specific carbon and hydrogen isotopic fractionation during benzene removal and the results obtained by dual compound specific isotope analysis (C = -2.4‰ ± 0.3‰; H = -57‰ ± 0.98‰; AKIEC: 1.0146 ± 0.0009, and AKIEH: 1.5184 ± 0.0283) were close to those obtained previously in sulfate-reducing conditions: this finding could confirm the existence of a common enzymatic reaction involving sulfate-reducers to activate benzene anaerobically. Although we cannot assign the role of each population of Desulfotomaculum in the mono-aromatic hydrocarbon degradation, this study suggests an important role of the genus Desulfotomaculum as potential biodegrader among indigenous populations in subsurface habitats. This community represents the simplest model of benzene-degrading anaerobes originating from the deepest subterranean settings ever described. As Desulfotomaculum species are often encountered in subsurface environments, this study provides some interesting results for assessing the natural response of these specific hydrologic systems in response to BTEX contamination during remediation projects.

Distribution of aliphatic hydrocarbons, polycyclic aromatic hydrocarbons and organochlorinated pollutants in deep-sea sediments of the Southern Cretan margin, Eastern Mediterranean Sea: a baseline assessment.

PubMed

Mandalakis, Manolis; Polymenakou, Paraskevi N; Tselepides, Anastasios; Lampadariou, Nikolaos

2014-07-01

Deep sediments from the southern Cretan margin were analyzed to establish baseline levels for various types of organic pollutants before the anticipated intensification of anthropogenic activities. The total concentration of aliphatic hydrocarbons (ΣAH:326-3758ngg(-1), dry weight) was similar to those reported for deep sediments of the western Mediterranean Sea, while considerably lower levels were measured for polycyclic aromatic hydrocarbons (ΣPAH:9-60ngg(-1)). Source-diagnostic ratios suggested that the aliphatic hydrocarbons in sediments were mainly of terrestrial biogenic origin, while polycyclic aromatic hydrocarbons stemmed from the deposition of long-range transported combustion aerosols. Among the organochlorinated compounds analyzed, β-hexachlorocyclohexane (β-HCH:222-7052pgg(-1)), 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (p,p'-DDT:37-2236pgg(-1)) and polychlorinated biphenyls (ΣPCB:38-1182pgg(-1)) showed the highest abundance in sediments. The presence of HCHs and PCBs was attributed to historical inputs that have undergone extensive weathering, whereas an ongoing fresh input was suggested for p,p'-DDT. Multiple linear regression analysis revealed that the levels of the various pollutants in sediments were controlled by different factors, but with organic carbon content playing a prominent role in most cases. Copyright © 2014 Elsevier Ltd. All rights reserved.

Mercury as a Global Pollutant: Sources, Pathways, and Effects

PubMed Central

2013-01-01

Mercury (Hg) is a global pollutant that affects human and ecosystem health. We synthesize understanding of sources, atmosphere-land-ocean Hg dynamics and health effects, and consider the implications of Hg-control policies. Primary anthropogenic Hg emissions greatly exceed natural geogenic sources, resulting in increases in Hg reservoirs and subsequent secondary Hg emissions that facilitate its global distribution. The ultimate fate of emitted Hg is primarily recalcitrant soil pools and deep ocean waters and sediments. Transfers of Hg emissions to largely unavailable reservoirs occur over the time scale of centuries, and are primarily mediated through atmospheric exchanges of wet/dry deposition and evasion from vegetation, soil organic matter and ocean surfaces. A key link between inorganic Hg inputs and exposure of humans and wildlife is the net production of methylmercury, which occurs mainly in reducing zones in freshwater, terrestrial, and coastal environments, and the subsurface ocean. Elevated human exposure to methylmercury primarily results from consumption of estuarine and marine fish. Developing fetuses are most at risk from this neurotoxin but health effects of highly exposed populations and wildlife are also a concern. Integration of Hg science with national and international policy efforts is needed to target efforts and evaluate efficacy. PMID:23590191

Life strategies of a ubiquitous and abundant subsurface archaeal group Bathyarchaeota

NASA Astrophysics Data System (ADS)

He, Y.; Li, M.; Perumal, V.; Feng, X.; Sievert, S. M.; Wang, F.

2015-12-01

Archaea belonging to the Miscellaneous Crenarchaeota Group (MCG, "Candidatus Bathyarchaeota") are widespread and abundant in the deep biosphere, yet their life strategies and ecological roles remain elusive. Metagenomic sequencing of a sample enriched in Bathyarchaeota (up to 74%) that originated from Guaymas Basin deep-sea vent sediments revealed 6 partial to nearly completed Bathyarchaeota genomic bins. ranging ~900kb-3.3Mb. The Bathyarchaeota bin size ranged from approximately 0.9 to 3.3 Mb, with coverage ranging from approximately 10× to 28×. The phylogeny based on 110 concatenated conserved archaeal single copy genes confirmed the placement of Bathyarchaeota into a novel archaeal phylum. Genes encoding for enzymes involved in the degradation of organic polymers such as protein, cellulose, chitin, and aromatic compounds, were identified. In addition, genes encoding glycolysis/gluconeogenesis, beta-oxidation pathways and the tricarboxylic acid cycle (except citrate synthase) were present in all genomic bins highlighting the heterotrophic life style of Bathyarchaeota. The presence of a wide variety of transporters of organic compounds further supports the versatile heterotrophic metabolism of Bathyarchaeota. This study highlights the life strategies of a ubiquitous and abundant subsurface archaeal group that thrives under energy-limited conditions, and expands the metabolic potentials of Archaea that play important roles in carbon cycling in marine sediments.

Insights into the Lurking Structures and Related Intraplate Earthquakes in the Region of Bay of Bengal Using Gravity and Full Gravity Gradient Tensor

NASA Astrophysics Data System (ADS)

Dubey, C. P.; Tiwari, V. M.; Rao, P. R.

2017-12-01

Comprehension of subsurface structures buried under thick sediments in the region of Bay of Bengal is vital as structural features are the key parameters that influence or are caused by the subsurface deformation and tectonic events like earthquakes. Here, we address this issue using the integrated analysis and interpretation of gravity and full gravity gradient tensor with few seismic profiles available in the poorly known region. A 2D model of the deep earth crust-mantle is constructed and interpreted with gravity gradients and seismic profiles, which made it possible to obtain a visual image of a deep seated fault below the basement associated with thick sediments strata. Gravity modelling along a NE-SW profile crossing the hypocentre of the earthquake of 21 May 2014 ( M w 6.0) in the northern Bay of Bengal suggests that the location of intraplate normal dip fault earthquake in the upper mantle is at the boundary of density anomalies, which is probably connected to the crustal fault. We also report an enhanced structural trend of two major ridges, the 85°E and the 90°E ridges hidden under the sedimentary cover from the computed full gravity gradients tensor components.

Internal tides affect benthic community structure in an energetic submarine canyon off SW Taiwan

NASA Astrophysics Data System (ADS)

Liao, Jian-Xiang; Chen, Guan-Ming; Chiou, Ming-Da; Jan, Sen; Wei, Chih-Lin

2017-07-01

Submarine canyons are major conduits of terrestrial and shelf organic matter, potentially benefiting the seafloor communities in the food-deprived deep sea; however, strong bottom currents driven by internal tides and the potentially frequent turbidity currents triggered by storm surges, river flooding, and earthquakes may negatively impact the benthos. In this study, we investigated the upper Gaoping Submarine Canyon (GPSC), a high-sediment-yield canyon connected to a small mountain river (SMR) off southwest (SW) Taiwan. By contrasting the benthic meiofaunal and macrofaunal communities within and outside the GPSC, we examined how food supplies and disturbance influenced the benthic community assemblages. The benthic communities in the upper GPSC were mainly a nested subset of the adjacent slope assemblages. Several meiofaunal (e.g. ostracods) and macrofaunal taxa (e.g. peracarid crustaceans and mollusks) that typically occurred on the slope were lost from the canyon. The polychaete families switched from diverse feeding guilds on the slope to motile subsurface deposit feeders dominant in the canyon. The diminishing of epibenthic peracarids and proliferation of deep burrowing polychaetes in the GPSC resulted in macrofauna occurring largely within deeper sediment horizons in the canyon than on the slope. The densities and numbers of taxa were depressed with distinct and more variable composition in the canyon than on the adjacent slope. Both the densities and numbers of taxa were negatively influenced by internal tide flushing and positively influenced by food availability; however, the internal tides also negatively influenced the food supplies. While the meiofauna and macrofauna densities were both depressed by the extreme physical conditions in the GPSC, only the macrofaunal densities increased with depth in the canyon, presumably related to increased frequency and intensity of disturbance toward the canyon head. The population densities of meiofauna, on the other hand, rebounded more rapidly due to their fast growth rate and short generation time and thus did not display bathymetric pattern in the canyon. To our knowledge, this is the first benthic ecological study in a submarine canyon connected to a high-sediment-yield SMR. The biological responses to extreme physical conditions in the GPSC could have broad implications on understanding the anthropogenic and climate change impacts in the deep-sea ecosystems.

Subsurface dolomite formation during post-depositional flow of sulphate-bearing fluids from underlying salt giants: Early Pliocene example at DSDP Leg 42A, Site 374, Ionian Abyssal Plain

NASA Astrophysics Data System (ADS)

McKenzie, Judith A.; Evans, Nick; Hodell, David; Aloisi, Giovanni; Vasconcelos, Crisogono

2017-04-01

Deciphering exact mechanisms for the formation of massive dolomite deposits has long been an enigma in sedimentary geology. The recognition that microbes can play a role in the dolomite precipitation process has added a new dimension to the study of the origin of dolomite formations in both shallow and deep-water environments. This scientific advance has evolved, particularly, through the investigation of dolomite-containing, organic-rich hemipelagic sediments cored on various continental margins during DSDP and ODP drilling campaigns, as well as intensive evaluations of modern hypersaline dolomite-precipitating environments with complementary culture experiments conducted in the laboratory. For example, the association of an active subsurface microbial community in contact with underlying brines of unknown origin leading to in situ dolomite precipitation has been observed in a Quaternary sequence of hemi-pelagic, organic carbon-rich sediments drilled on the Peru Margin, ODP Leg 201, Site 1229 (1). Specifically, it can be concluded that the long-term activity of subsurface microbes can be maintained by post-depositional flow of sulfate-bearing fluids from underlying large-scale evaporite deposits, or salt giants, promoting in situ dolomite precipitation. Another example of dolomite precipitation directly associated with the underlying Messinian salt giant was found at DSDP Leg 42A, Site 374 in the Ionian Abyssal Plain. Deep-sea drilling recovered a lowermost Pliocene sequence of diagenetically altered sediment (Unit II) separating the overlying Pliocene open-marine deposits (Unit I) and the underlying end Messinian dolomitic mudstone with gypsum layers (Unit III). The lower portion of this altered interval contained in Core 11, Section 2 (378.0 - 381.5 mbsf) comprises a dolomicrite with an unusual crystal morphology (2). The original interstitial water geochemical profiles indicate that a saline brine is diffusing upwards from below and into the dolomicrite sequence. There appears to be on-going bacterial sulfate reduction in this boundary zone between the evaporitic and normal pelagic sediments with a significant decrease in sulfate concentrations, whereas the chloride profile remains constant. It was concluded that the earliest Pliocene marine sediments of Unit II had been dolomitized after burial as a consequence of ionic migration across a steep Mg-concentration gradient (3). However, with the addition of a microbial factor into the study of the dolomite precipitation process, an alternate interpretation is possible. We propose that, at the location of DSDP Leg 42A, Site 374, modern subsurface dolomite precipitation is ongoing and the site is a "natural laboratory" in which to investigate the microbial phenomenon in the context of a giant evaporite deposit. This actualistic example may provide a new model for the origin of massive dolomite deposits associated with other salt giants in the rock record. (1) Meister, P., et al., 2007. Sedimentology, 54, 1007-1031. (2) Bernoulli, D. & Mélières, F., 1978. In: Hsü, K., Montadert, L. et al., 1978. Initial Reports of the Deep Sea Drilling Project, Volume 42, Part 1, 621-633. (3) McDuff, R.E., et al., 1978. In: Hsü, K., Montadert, L. et al., 1978. Initial Reports of the Deep Sea Drilling Project, Volume 42, Part 1, 561-568.

Mangrove sedimentation and response to relative sea-level rise

USGS Publications Warehouse

Woodroffe, CD; Rogers, K.; Mckee, Karen L.; Lovelock, CE; Mendelssohn, IA; Saintilan, N.

2016-01-01

Mangroves occur on upper intertidal shorelines in the tropics and subtropics. Complex hydrodynamic and salinity conditions influence mangrove distributions, primarily related to elevation and hydroperiod; this review considers how these adjust through time. Accumulation rates of allochthonous and autochthonous sediment, both inorganic and organic, vary between and within different settings. Abundant terrigenous sediment can form dynamic mudbanks; tides redistribute sediment, contrasting with mangrove peat in sediment-starved carbonate settings. Sediments underlying mangroves sequester carbon, but also contain paleoenvironmental records of adjustments to past sea-level changes. Radiometric dating indicates long-term sedimentation, whereas Surface Elevation Table-Marker Horizon measurements (SET-MH) provide shorter perspectives, indicating shallow subsurface processes of root growth and substrate autocompaction. Many tropical deltas also experience deep subsidence, which augments relative sea-level rise. The persistence of mangroves implies an ability to cope with moderately high rates of relative sea-level rise. However, many human pressures threaten mangroves, resulting in continuing decline in their extent throughout the tropics.

Viral infections as controlling factors for the deep biosphere? (Invited)

NASA Astrophysics Data System (ADS)

Engelen, B.; Engelhardt, T.; Sahlberg, M.; Cypionka, H.

2009-12-01

The marine deep biosphere represents the largest biotope on Earth. Throughout the last years, we have obtained interesting insights into its microbial community composition. However, one component that was completely overlooked so far is the viral inventory of deep-subsurface sediments. While viral infections were identified to have a major impact on the benthic microflora of deep-sea surface sediments (Danavaro et al. 2008), no studies were performed on deep-biosphere samples, so far. As grazers probably play only a minor role in anoxic and highly compressed deep sediments, viruses might be the main “predators” for indigenous microorganisms. Furthermore, the release of cell components, called “the viral shunt”, could have a major impact on the deep biosphere in providing labile organic compounds to non-infected microorganisms in these generally nutrient depleted sediments. However, direct counting of viruses in sediments is highly challenging due to the small size of viruses and the high background of small particles. Even molecular surveys using “universal” PCR primers that target phage-specific genes fail due to the vast phage diversity. One solution for this problem is the lysogenic viral life cycle as many bacteriophages integrate their DNA into the host genome. It is estimated that up to 70% of cultivated bacteria contain prophages within their genome. Therefore, culture collections (Batzke et al. 2007) represent an archive of the viral composition within the respective habitat. These prophages can be induced to become free phage particles in stimulation experiments in which the host cells are set under certain stress situations such as a treatment with UV exposure or DNA-damaging antibiotics. The study of the viral component within the deep biosphere offers to answer the following questions: To which extent are deep-biosphere populations controlled by viral infections? What is the inter- and intra-specific diversity and the host-specific viral biogeography? Can viral infections tell us something about the physiological state of indigenous microorganisms? Finally, we will obtain estimates for the viral shunt as an important factor for sustaining the deep biosphere. References: Batzke A, Engelen B, Sass H, Cypionka H (2007) Phylogenetic and physiological diversity of cultured deep-biosphere bacteria from Equatorial Pacific Ocean and Peru Margin sediments. Geomicrobiology J 24:261-273 Danovaro R, Dell'Anno A, Corinaldesi C, Magagnini M, Noble R, Tamburini C, Weinbauer M (2008) Major viral impact on the functioning of benthic deep-sea ecosystems. Nature 454: 1084-U1027.

Influence of Wastewater Discharge on the Metabolic Potential of the Microbial Community in River Sediments.

PubMed

Li, Dong; Sharp, Jonathan O; Drewes, Jörg E

2016-01-01

To reveal the variation of microbial community functions during water filtration process in river sediments, which has been utilized widely in natural water treatment systems, this study investigates the influence of municipal wastewater discharge to streams on the phylotype and metabolic potential of the microbiome in upstream and particularly various depths of downstream river sediments. Cluster analyses based on both microbial phylogenetic and functional data collectively revealed that shallow upstream sediments grouped with those from deeper subsurface downstream regions. These sediment samples were distinct from those found in shallow downstream sediments. Functional genes associated with carbohydrate, xenobiotic, and certain amino acid metabolisms were overrepresented in upstream and deep downstream samples. In contrast, the more immediate contact with wastewater discharge in shallow downstream samples resulted in an increase in the relative abundance of genes associated with nitrogen, sulfur, purine and pyrimidine metabolisms, as well as restriction-modification systems. More diverse bacterial phyla were associated with upstream and deep downstream sediments, mainly including Actinobacteria, Planctomycetes, and Firmicutes. In contrast, in shallow downstream sediments, genera affiliated with Betaproteobacteria and Gammaproteobacteria were enriched with putative functions that included ammonia and sulfur oxidation, polyphosphate accumulation, and methylotrophic bacteria. Collectively, these results highlight the enhanced capabilities of microbial communities residing in deeper stream sediments for the transformation of water contaminants and thus provide a foundation for better design of natural water treatment systems to further improve the removal of contaminants.

Phylogeny and phylogeography of functional genes shared among seven terrestrial subsurface metagenomes reveal N-cycling and microbial evolutionary relationships

PubMed Central

Lau, Maggie C. Y.; Cameron, Connor; Magnabosco, Cara; Brown, C. Titus; Schilkey, Faye; Grim, Sharon; Hendrickson, Sarah; Pullin, Michael; Sherwood Lollar, Barbara; van Heerden, Esta; Kieft, Thomas L.; Onstott, Tullis C.

2014-01-01

Comparative studies on community phylogenetics and phylogeography of microorganisms living in extreme environments are rare. Terrestrial subsurface habitats are valuable for studying microbial biogeographical patterns due to their isolation and the restricted dispersal mechanisms. Since the taxonomic identity of a microorganism does not always correspond well with its functional role in a particular community, the use of taxonomic assignments or patterns may give limited inference on how microbial functions are affected by historical, geographical and environmental factors. With seven metagenomic libraries generated from fracture water samples collected from five South African mines, this study was carried out to (1) screen for ubiquitous functions or pathways of biogeochemical cycling of CH4, S, and N; (2) to characterize the biodiversity represented by the common functional genes; (3) to investigate the subsurface biogeography as revealed by this subset of genes; and (4) to explore the possibility of using metagenomic data for evolutionary study. The ubiquitous functional genes are NarV, NPD, PAPS reductase, NifH, NifD, NifK, NifE, and NifN genes. Although these eight common functional genes were taxonomically and phylogenetically diverse and distinct from each other, the dissimilarity between samples did not correlate strongly with geographical or environmental parameters or residence time of the water. Por genes homologous to those of Thermodesulfovibrio yellowstonii detected in all metagenomes were deep lineages of Nitrospirae, suggesting that subsurface habitats have preserved ancestral genetic signatures that inform the study of the origin and evolution of prokaryotes. PMID:25400621

From Río Tinto to Mars: the terrestrial and extraterrestrial ecology of acidophiles.

PubMed

Amils, R; González-Toril, E; Aguilera, A; Rodríguez, N; Fernández-Remolar, D; Gómez, F; García-Moyano, A; Malki, M; Oggerin, M; Sánchez-Andrea, I; Sanz, J L

2011-01-01

The recent geomicrobiological characterization of Río Tinto, Iberian Pyrite Belt (IPB), has proven the importance of the iron cycle, not only in generating the extreme conditions of the habitat (low pH, high concentration of toxic heavy metals) but also in maintaining the high level of microbial diversity, both prokaryotic and eukaryotic, detected in the water column and the sediments. The extreme conditions of the Tinto basin are not the product of industrial contamination but the consequence of the presence of an underground bioreactor that obtains its energy from the massive sulfide minerals of the IPB. To test this hypothesis, a drilling project was carried out to intersect ground waters that interact with the mineral ore in order to provide evidence of subsurface microbial activities and the potential resources to support these activities. The oxidants that drive the system appear to come from the rock matrix, contradicting conventional acid mine drainage models. These resources need only groundwater to launch microbial metabolism. There are several similarities between the vast deposits of sulfates and iron oxides on Mars and the main sulfide-containing iron bioleaching products found in the Tinto. Firstly, the short-lived methane detected both in Mars' atmosphere and in the sediments and subsurface of the IPB and secondly, the abundance of iron, common to both. The physicochemical properties of iron make it a source of energy, a shield against radiation and oxidative stress as well as a natural pH controller. These similarities have led to Río Tinto's status as a Mars terrestrial analogue. Copyright © 2011 Elsevier Inc. All rights reserved.

DUSEL and the future of deep terrestrial microbiology (Invited)

NASA Astrophysics Data System (ADS)

Onstott, T. C.; Peters, C. A.; Murdoch, L. C.; Elsworth, D.; Sonnenthal, E. L.; Kieft, T.; Boutt, D. F.; Germanovich, L.; Glaser, S. D.; Wang, H. F.; Roggenthen, B.; Lesko, K.; Cushman, P.; Stetler, L. D.; Bang, S.; Anderson, C.

2009-12-01

DUSEL will take advantage of the existing subsurface architecture of the deepest mine in the U.S. to provide a platform for launching new exploration into the deep terrestrial biosphere. Multi-year experiments are currently being designed to delineate the relationships between microbial diversity and activity and hydraulic connectivity, temperature, pressure, strain rate and multiphase fluids. Unlike the physics experiments, which will be located close to the center of the mine, most of these experiments will be located at the periphery in existing tunnels at 100 to 2400 m depth in order to access fluid fill fractures with boreholes. Hydrological models suggest that DUSEL could sample ~100 km3 volume for microbial biogeographic and transport studies. The high-capacity underground water filtration plant used to generate ultrapure water for neutrino detectors will readily supply water for microbiology coring projects reducing microbial contamination. This will be essential for the drilling platform located at 2400 m depth that will drill down to 7+ km and 120oC in search of the upper temperature limit for life. Another advantage of underground coring is that the drilling fluid pressure will be much less than that of the fracture water, which means that when the coring bit intersects a water-filled fracture, the fracture water will flow into the core barrel reducing the contamination of fracture surfaces in the cores. The ultra-low radiation background counting facility to be located at 1475 m depth will potentially enable 106 times improvement in the detection limit for subsurface microbial respiration rates using radioactive tracers. The Coupled Thermal-Hydrological-Mechanical-Chemical-Biological, block-heating experiment will examine how the microbial communities within fractures respond to the increased thermal and fluid flux. The Fracture Processes Facility is not only designed to determine what controls rock strength, but could also determine to what extent subsurface chemoautotrophic activity is regulated by tectonic episodicity. The DUSEL CO2 Facility will investigate how microbial activity is impacted by CO2 injection and whether microbial activity has a significant impact upon long-term sequestration of CO2. These three experiments represent a subset of the integrated suite of experiments planned for the first 5 years, but many more microbial experiments can be accommodated within DUSEL. With its unique experimental assets, km-scale spatial access and multi-decade observational lifetime, DUSEL will usher in the next generation of exploration into the deep terrestrial biosphere and not only reveal the answers to many of its well-hidden secrets, but perhaps to the origin of life itself.

Optimization of remediation strategies using vadose zone monitoring systems

NASA Astrophysics Data System (ADS)

Dahan, Ofer

2016-04-01

In-situ bio-remediation of the vadose zone depends mainly on the ability to change the subsurface hydrological, physical and chemical conditions in order to enable development of specific, indigenous, pollutants degrading bacteria. As such the remediation efficiency is much dependent on the ability to implement optimal hydraulic and chemical conditions in deep sections of the vadose zone. These conditions are usually determined in laboratory experiments where parameters such as the chemical composition of the soil water solution, redox potential and water content of the sediment are fully controlled. Usually, implementation of desired optimal degradation conditions in deep vadose zone at full scale field setups is achieved through infiltration of water enriched with chemical additives on the land surface. It is assumed that deep percolation into the vadose zone would create chemical conditions that promote biodegradation of specific compounds. However, application of water with specific chemical conditions near land surface dose not necessarily results in promoting of desired chemical and hydraulic conditions in deep sections of the vadose zone. A vadose-zone monitoring system (VMS) that was recently developed allows continuous monitoring of the hydrological and chemical properties of deep sections of the unsaturated zone. The VMS includes flexible time-domain reflectometry (FTDR) probes which allow continuous monitoring of the temporal variation of the vadose zone water content, and vadose-zone sampling ports (VSPs) which are designed to allow frequent sampling of the sediment pore-water and gas at multiple depths. Implementation of the vadose zone monitoring system in sites that undergoes active remediation provides real time information on the actual chemical and hydrological conditions in the vadose zone as the remediation process progresses. Up-to-date the system has been successfully implemented in several studies on water flow and contaminant transport in the unsaturated zone including enhanced bioremediation of contaminated deep vadose zone (40 m depth). Manipulating subsurface conditions for enhanced bioremediation was demonstrated through two remediation projects. One site is characterized by 20 m deep vadose zone that is contaminated with gasoline products and the other is a 40 m deep vadose zone that is contaminated with perchlorate. In both cases temporal variation of the sediment water content as well as the variations in the vadose zone chemical and isotopic composition allowed real time detection of water flow velocities, contaminants transport rates and bio-degradation degree. Results and conclusions from each wetting cycle were used to improve the following wetting cycles in order to optimize contaminants degradation conditions while minimizing leaching of contaminants to the groundwater.

Spatial Structure and Activity of Sedimentary Microbial Communities Underlying a Beggiatoa spp. Mat in a Gulf of Mexico Hydrocarbon Seep

PubMed Central

Lloyd, Karen G.; Albert, Daniel B.; Biddle, Jennifer F.; Chanton, Jeffrey P.; Pizarro, Oscar; Teske, Andreas

2010-01-01

Background Subsurface fluids from deep-sea hydrocarbon seeps undergo methane- and sulfur-cycling microbial transformations near the sediment surface. Hydrocarbon seep habitats are naturally patchy, with a mosaic of active seep sediments and non-seep sediments. Microbial community shifts and changing activity patterns on small spatial scales from seep to non-seep sediment remain to be examined in a comprehensive habitat study. Methodology/Principal Findings We conducted a transect of biogeochemical measurements and gene expression related to methane- and sulfur-cycling at different sediment depths across a broad Beggiatoa spp. mat at Mississippi Canyon 118 (MC118) in the Gulf of Mexico. High process rates within the mat (∼400 cm and ∼10 cm from the mat's edge) contrasted with sharply diminished activity at ∼50 cm outside the mat, as shown by sulfate and methane concentration profiles, radiotracer rates of sulfate reduction and methane oxidation, and stable carbon isotopes. Likewise, 16S ribosomal rRNA, dsrAB (dissimilatory sulfite reductase) and mcrA (methyl coenzyme M reductase) mRNA transcripts of sulfate-reducing bacteria (Desulfobacteraceae and Desulfobulbaceae) and methane-cycling archaea (ANME-1 and ANME-2) were prevalent at the sediment surface under the mat and at its edge. Outside the mat at the surface, 16S rRNA sequences indicated mostly aerobes commonly found in seawater. The seep-related communities persisted at 12–20 cm depth inside and outside the mat. 16S rRNA transcripts and V6-tags reveal that bacterial and archaeal diversity underneath the mat are similar to each other, in contrast to oxic or microoxic habitats that have higher bacterial diversity. Conclusions/Significance The visual patchiness of microbial mats reflects sharp discontinuities in microbial community structure and activity over sub-meter spatial scales; these discontinuities have to be taken into account in geochemical and microbiological inventories of seep environments. In contrast, 12–20 cm deep in the sediments microbial communities performing methane-cycling and sulfate reduction persist at lower metabolic rates regardless of mat cover, and may increase activity rapidly when subsurface flow changes. PMID:20090951

Bacterial Growth, Necromass Turnover, And Endospore Abundance In The Deep Subseafloor Sediments Of The Greenland Shelf Using D:L Amino Acid Model.

NASA Astrophysics Data System (ADS)

Mhatre, S. S.; Braun, S.; Jaussi, M.; Røy, H.; Jørgensen, B. B.; Lomstein, B. A.

2015-12-01

The subsurface realm is colonized by a large number of microorganisms- about 3 × 1029. Microbial cells in these very stable and oligotrophic settings catabolize at a much slower rate than model organisms in nutrient rich cultures. The aim of this work was to use recently developed D:L-amino acid racemization model for studying the turnover times of microbial biomass and microbial necromass in a ~12,000 years old Greenland shelf marine sediment samples. Sediments were analyzed for total hydrolysable amino acids (THAA), the bacterial endospore marker dipicolinic acid (DPA), and amino acid enantiomers of aspartic acid. The percentage amino acid carbon content (%TAAC) and the percentage amino acid nitrogen content (%TAAN) were used for determining the degradation state of the organic matter. Endospores quantified using DPA quantification method were found to be as abundant as vegetative cells. The microbial necromass turnover times were thousand years, and biomass turnover times were in the range of tens to hundred years. Studies with deeper sediment cores will further improve our understanding of the energetic limits of life in the deep biosphere.

The role of deep-water sedimentary processes in shaping a continental margin: The Northwest Atlantic

USGS Publications Warehouse

Mosher, David C.; Campbell, D.C.; Gardner, J.V.; Piper, D.J.W.; Chaytor, Jason; Rebesco, M.

2017-01-01

The tectonic history of a margin dictates its general shape; however, its geomorphology is generally transformed by deep-sea sedimentary processes. The objective of this study is to show the influences of turbidity currents, contour currents and sediment mass failures on the geomorphology of the deep-water northwestern Atlantic margin (NWAM) between Blake Ridge and Hudson Trough, spanning about 32° of latitude and the shelf edge to the abyssal plain. This assessment is based on new multibeam echosounder data, global bathymetric models and sub-surface geophysical information.The deep-water NWAM is divided into four broad geomorphologic classifications based on their bathymetric shape: graded, above-grade, stepped and out-of-grade. These shapes were created as a function of the balance between sediment accumulation and removal that in turn were related to sedimentary processes and slope-accommodation. This descriptive method of classifying continental margins, while being non-interpretative, is more informative than the conventional continental shelf, slope and rise classification, and better facilitates interpretation concerning dominant sedimentary processes.Areas of the margin dominated by turbidity currents and slope by-pass developed graded slopes. If sediments did not by-pass the slope due to accommodation then an above grade or stepped slope resulted. Geostrophic currents created sedimentary bodies of a variety of forms and positions along the NWAM. Detached drifts form linear, above-grade slopes along their crests from the shelf edge to the deep basin. Plastered drifts formed stepped slope profiles. Sediment mass failure has had a variety of consequences on the margin morphology; large mass-failures created out-of-grade profiles, whereas smaller mass failures tended to remain on the slope and formed above-grade profiles at trough-mouth fans, or nearly graded profiles, such as offshore Cape Fear.

Collection, processing, and interpretation of ground-penetrating radar data to determine sediment thickness at selected locations in Deep Creek Lake, Garrett County, Maryland, 2007

USGS Publications Warehouse

Banks, William S.L.; Johnson, Carole D.

2011-01-01

This investigation focused on selected regions of the study area, particularly in the coves where sediment accumulations were presumed to be thickest. GPR was the most useful tool for interpreting sediment thickness, especially in these shallow coves. The radar profiles were interpreted for two surfaces of interest-the water bottom, which was defined as the "2007 horizon," and the interface between Lake sediments and the original Lake bottom, which was defined as the "1925 horizon"-corresponding to the year the Lake was impounded. The ground-penetrating radar data were interpreted on the basis of characteristics of the reflectors. The sediments that had accumulated in the impounded Lake were characterized by laminated, parallel reflections, whereas the subsurface below the original Lake bottom was characterized by more discontinuous and chaotic reflections, often with diffractions indicating cobbles or boulders. The reflectors were picked manually along the water bottom and along the interface between the Lake sediments and the pre-Lake sediments. A simple graphic approach was used to convert traveltimes to depth through water and depth through saturated sediments using velocities of the soundwaves through the water and the saturated sediments. Nineteen cross sections were processed and interpreted in 9 coves around Deep Creek Lake, and the difference between the 2007 horizon and the 1925 horizon was examined. In most areas, GPR data indicate a layer of sediment between 1 and 7 feet thick. When multiple cross sections from a single cove were compared, the cross sections indicated that sediment thickness decreased toward the center of the Lake.

Pleistocene Through Oligocene Record of Himalayan Orogeny and Climate. The Iodp Expedition 354 Drilling Transect across the Middle Bengal Fan at 8°N

NASA Astrophysics Data System (ADS)

Spiess, V.; France-Lanord, C.; Schwenk, T.; Klaus, A.

2015-12-01

IODP Expedition 354 in the Bay of Bengal February-March 2015 drilled a seven site, 320 km-long transect across the Bengal Fan at 8°N. Three deep penetration and additional four shallow holes provided a spatial overview of the primarily turbiditic depositional system, comprising the Bengal deep sea fan. Sediments originate from Himalayan rivers, documenting terrestrial changes of the monsoon evolution and Himalayan erosion and weathering, and are transported through a delta and shelf canyon, supplying turbidity currents loaded with a full spectrum of grain sizes. Mostly following transport channels, sediments deposit on and between levees, while depocenters are laterally shifting over hundreds of kilometers on millennial time scales. Expedition 354 documented these deposits in space and time by identifying, coring and dating numerous stratigraphic marker horizons across the transect, allowing a detailed reconstruction of channel-levee migration, abandonment, reoccupation and overall uniform growth in the late Pleistocene. High resolution records of these growth patterns were acquired in several levee, interlevee and hemipelagic successions. Miocene through Pliocene fan development was studied at three deeper sites, which document and recovered sand rich facies throughout most of the cores acquired by the half-APC coring technology, intercalated by longer periods of hemipelagic deposition and absence of turbiditic input as the results of major depocenter shifts. Recovered sediments have Himalayan mineralogical and geochemical signatures suitable to reconstruct time series of erosion, weathering and changes in source regions as well as impacts on the global carbon cycle. Miocene shifts in terrestrial vegetation, in sediment budget and in style of sediment transport have been tracked. Expedition 354 has extended the record of early fan deposition by 10 Ma into the Late Oligocene.

Age and provenance of Triassic to Cenozoic sediments of West and Central Sarawak, Malaysia

NASA Astrophysics Data System (ADS)

Breitfeld, H. Tim; Galin, Thomson; Hall, Robert

2015-04-01

Sarawak is located on the northern edge of Sundaland in NW Borneo. West and Central Sarawak include parts of the Kuching and Sibu Zones. These contain remnants of several sedimentary basins with ages from Triassic to Cenozoic. New light mineral, heavy mineral and U-Pb detrital zircon ages show differences in provenance reflecting the tectonic evolution of the region. The oldest clastic sediments are Triassic (Sadong Formation and its deep marine equivalent Kuching Formation). They were sourced by a Triassic (Carnian to Norian) volcanic arc and reworked Paleoproterozoic detritus derived from Cathaysialand. The Upper Jurassic to Cretaceous Pedawan Formation is interpreted as forearc basin fill with distinctive zircon populations indicating subduction beneath present-day West Sarawak which initiated in the Late Jurassic. Subsequent subduction until the early Late Cretaceous formed the Schwaner Mountains magmatic arc. After collision of SW Borneo and other microcontinental fragments with Sundaland in the early Late Cretaceous, deep marine sedimentation (Pedawan Formation) ceased, and there was uplift forming the regional Pedawan-Kayan unconformity. Two episodes of extension followed and were responsible for basin development on land in West Sarawak from the latest Cretaceous onwards, probably in a pull-apart setting. The first episode is associated with sediments of the Kayan Group, deposited in the Latest Cretaceous (Maastrichtian) to Eocene, and the second episode with Upper Eocene sediments of the Ketungau Basin. Zircon ages indicate volcanic activity throughout the Early Cenozoic in NW Borneo, and inherited zircon ages indicate reworking of Triassic and Cretaceous rocks. A large deep marine basin, the Rajang Basin, was north of the Lupar Line Fault in Central Sarawak (Sibu Zone) from the Late Cretaceous to the Late Eocene. Zircons from sediments of the Rajang Basin indicate they have similar ages and provenance to contemporaneous terrestrial sediments of the Kayan Group and Ketungau Basin to the south, suggesting a narrow steep continental Sundaland margin at the position of the Lupar Line, and a large-scale sedimentary connection between the terrestrial and deep marine basins in the Late Cretaceous to Late Eocene. A recent reconstruction for the proto-South China Sea proposed an isolated so-called Semitau terrane colliding with SW Borneo and Sundaland in the Late Eocene. Our data show that the area of the Kuching and Sibu Zones were connected with SW Borneo and Sundaland from the Cretaceous onwards. The Cretaceous and Cenozoic sedimentary basins were sourced by alternations of Schwaner Mountains and Malay Tin Belt rocks. Our new age and provenance data cannot be explained by an isolated Semitau terrane and a Late Eocene collision.

Permafrost Organic Carbon Mobilization From the Watershed to the Colville River Delta: Evidence From 14C Ramped Pyrolysis and Lignin Biomarkers

NASA Astrophysics Data System (ADS)

Zhang, Xiaowen; Bianchi, Thomas S.; Cui, Xingqian; Rosenheim, Brad E.; Ping, Chien-Lu; Hanna, Andrea J. M.; Kanevskiy, Mikhail; Schreiner, Kathryn M.; Allison, Mead A.

2017-11-01

The deposition of terrestrial-derived permafrost particulate organic carbon (POC) has been recorded in major Arctic river deltas. However, associated transport pathways of permafrost POC from the watershed to the coast have not been well constrained. Here we utilized a combination of ramped pyrolysis-oxidation radiocarbon analysis (RPO 14C) along with lignin biomarkers, to track the linkages between soils and river and delta sediments. Surface and deep soils showed distinct RPO thermographs which may be related to degradation and organo-mineral interaction. Soil material in the bed load of the river channel was mostly derived from deep old permafrost. Both surface and deep soils were transported and deposited to the coast. Hydrodynamic sorting and barrier island protection played important roles in terrestrial-derived permafrost POC deposition near the coast. On a large scale, ice processes (e.g., ice gauging and strudel scour) and ocean currents controlled the transport and distribution of permafrost POC on the Beaufort Shelf.

Mineralization of Bacteria in Terrestrial Basaltic Rocks: Comparison With Possible Biogenic Features in Martian Meteorite Allan Hills 84001

NASA Technical Reports Server (NTRS)

Thomas-Keprta, K. L.; McKay, D. S.; Wentworth, S. J.; Stevens, T. O.; Taunton, A. E.; Allen, C. C.; Gibson, E. K., Jr.; Romanek, C. S.

1998-01-01

The identification of biogenic features altered by diagenesis or mineralization is important in determining whether specific features in terrestrial rocks and in meteorites may have a biogenic origin. Unfortunately, few studies have addressed the formation of biogenic features in igneous rocks, which may be important to these phenomena, including the controversy over possible biogenic features in basaltic martian meteorite ALH84001. To explore the presence of biogenic features in igneous rocks, we examined microcosms growing in basaltic small-scale experimental growth chambers or microcosms. Microbial communities were harvested from aquifers of the Columbia River Basalt (CRB) group and grown in a microcosm containing unweathered basalt chips and groundwater (technique described in. These microcosms simulated natural growth conditions in the deep subsurface of the CRB, which should be a good terrestrial analog for any putative martian subsurface ecosystem that may have once included ALH84001. Here we present new size measurements and photomicrographs comparing the putative martian fossils to biogenic material in the CRB microcosms. The range of size and shapes of the biogenic features on the CRB microcosm chips overlaps with and is similar to those on ALH84001 chips. Although this present work does not provide evidence for the biogenicity of ALH84001 features, we believe that, based on criteria of size, shape, and general morphology, a biogenic interpretation for the ALH84001 features remains plausible.

Impact of landscape disturbance on the quality of terrestrial sediment carbon in temperate streams

NASA Astrophysics Data System (ADS)

Fox, James F.; Ford, William I.

2016-09-01

Recent studies have shown the super saturation of fluvial networks with respect to carbon dioxide, and the concept that the high carbon dioxide is at least partially the result of turnover of sediment organic carbon that ranges in age from years to millennia. Currently, there is a need for more highly resolved studies at stream and river scales that enable estimates of terrestrial carbon turnover within fluvial networks. Our objective was to develop a new isotope-based metric to estimate the quality of sediment organic carbon delivered to temperate streams and to use the new metric to estimate carbon quality across landscape disturbance gradients. Carbon quality is defined to be consistent with in-stream turnover and our metric is used to measure the labile or recalcitrant nature of the terrestrial-derived carbon within streams. Our hypothesis was that intensively-disturbed landscapes would tend to produce low quality carbon because deep, recalcitrant soil carbon would be eroded and transported to the fluvial system while moderately disturbed or undisturbed landscapes would tend to produce higher quality carbon from well-developed surface soils and litter. The hypothesis was tested by applying the new carbon quality metric to 15 temperate streams with a wide range of landscape disturbance levels. We find that our hypothesis premised on an indirect relationship between the extent of landscape disturbance and the quality of sediment carbon in streams holds true for moderate and high disturbances but not for un-disturbed forests. We explain the results based on the connectivity, or dis-connectivity, between terrestrial carbon sources and pathways for sediment transport. While pathways are typically un-limited for disturbed landscapes, the un-disturbed forests have dis-connectivity between labile carbon of the forest floor and the stream corridor. Only in the case when trees fell into the stream corridor due to severe ice storms did the quality of sediment carbon increase in the streams. We argue that as scientists continue to estimate the in-stream turnover of terrestrially-derived carbon in fluvial carbon budgets, the assumption of pathway connectivity between carbon sources to the stream should be justified.

Deep-Subsurface Marine Methane Hydrate Microbial Communities: Who's There and What Are They Doing?

NASA Astrophysics Data System (ADS)

Colwell, F.; Reed, D.; Fujita, Y.; Delwiche, M.; Blackwelder, D.; Uchida, T.; Fujii, T.; Lu, H.

2001-12-01

Natural gas hydrates are crystalline deposits of freshwater and primarily methane. They are estimated to represent a potentially vast reservoir of energy. Relatively little is known regarding microbial communities surrounding deep [>100 meters below sea floor (mbsf)] hydrate-bearing sediments. Deep sediment cores were collected in zones above, within, and below the hydrate bearing strata in an accretionary prism off the coast of Japan. Microorganisms were characterized using cultivation- and non-cultivation-based microbiological techniques to better understand the role that they play in the production and distribution of methane in gas hydrates. Direct counts show cell density at 105 cells/g throughout the hydrate strata. Lipid and 16S rDNA analyses indicate that diverse bacterial and archaeal microorganisms are represented throughout the strata. Acetate and hydrogen were utilized as an energy source for methane-producing microorganisms from each sediment depth. Although the methanogenic biomarker coenzyme M was not present above the detection limit in any of the samples, cloning and characterization of amplified 16S ribosomal RNA genes indicated the presence of methanogenic microorganisms related to the Methanobacteriales and Methanococcales. In addition, archaeal clones closely related to the hyperthermophilic Pyrodictiales were detected. Analysis of eubacterial clones indicated a more diverse eubacterial community compared to the archaea, including members from the groups of cyanobacteria, proteobacteria, gram positive bacteria, and flexibacter-cytophaga-bacteriodes. This study suggests that the diversity of microbial communities associated with the presence of methane in gas hydrate-rich deep marine sediments is greater than previously estimated.

Refined depositional history and dating of the Tongaporutuan reference section, north Taranaki, New Zealand: new volcanic ash U-Pb zircon ages, biostratigraphy and sedimentation rates

USGS Publications Warehouse

Maier, K.L.; Crundwell, Martin P.; Coble, Matthew A.; Kingsley-Smith, Peter R.; Graham, Stephan A.

2016-01-01

This study presents new radiometric ages from volcanic ash beds within a c. 1900 m thick, progradational, deep-water clastic slope succession of late Miocene age exposed along the north Taranaki coast of the North Island, New Zealand. The ash beds yield U–Pb zircon ages ranging from 10.63 ± 0.65 Ma to 8.97 ± 0.22 Ma. The new ages are compatible with and provide corroboration of New Zealand Tongaporutuan Stage planktic foraminiferal and bolboformid biostratigraphic events identified in the same section. The close accord between these two age datasets provides a stratigraphically consistent and coherent basis for examining margin evolution. The arrival of a prograding clastic wedge and ensuing upward shoaling is recorded by sedimentation rates c. 2000 m/Ma–1 that are an order of magnitude higher than sedimentation rates on the precursor deep basin floor. This outcrop study provides new constraints for interpreting analogous subsurface deposits in Taranaki Basin and complements the regional late Miocene biostratigraphic dating framework.

Subsurface North Atlantic warming as a trigger of rapid cooling events: evidence from the early Pleistocene (MIS 31-19)

NASA Astrophysics Data System (ADS)

Hernández-Almeida, I.; Sierro, F.-J.; Cacho, I.; Flores, J.-A.

2015-04-01

Subsurface water column dynamics in the subpolar North Atlantic were reconstructed in order to improve the understanding of the cause of abrupt ice-rafted detritus (IRD) events during cold periods of the early Pleistocene. We used paired Mg / Ca and δ18O measurements of Neogloboquadrina pachyderma (sinistral - sin.), deep-dwelling planktonic foraminifera, to estimate the subsurface temperatures and seawater δ18O from a sediment core from Gardar Drift, in the subpolar North Atlantic. Carbon isotopes of benthic and planktonic foraminifera from the same site provide information about the ventilation and water column nutrient gradient. Mg / Ca-based temperatures and seawater δ18O suggest increased subsurface temperatures and salinities during ice-rafting, likely due to northward subsurface transport of subtropical waters during periods of weaker Atlantic Meridional Overturning Circulation (AMOC). Planktonic carbon isotopes support this suggestion, showing coincident increased subsurface ventilation during deposition of IRD. Subsurface accumulation of warm waters would have resulted in basal warming and break-up of ice-shelves, leading to massive iceberg discharges in the North Atlantic. The release of heat stored at the subsurface to the atmosphere would have helped to restart the AMOC. This mechanism is in agreement with modelling and proxy studies that observe a subsurface warming in the North Atlantic in response to AMOC slowdown during Marine Isotope Stage (MIS) 3.

Methane related changes in prokaryotic activity along geochemical profiles in sediments of Lake Kinneret (Israel)

NASA Astrophysics Data System (ADS)

Bar Or, I.; Ben-Dov, E.; Kushmaro, A.; Eckert, W.; Sivan, O.

2014-06-01

Microbial methane oxidation process (methanotrophy) is the primary control on the emission of the greenhouse gas methane (CH4) to the atmosphere. In terrestrial environments, aerobic methanotrophic bacteria are mainly responsible for oxidizing the methane. In marine sediments the coupling of the anaerobic oxidation of methane (AOM) with sulfate reduction, often by a consortium of anaerobic methanotrophic archaea (ANME) and sulfate reducing bacteria, was found to consume almost all the upward diffusing methane. Recently, we showed geochemical evidence for AOM driven by iron reduction in Lake Kinneret (LK) (Israel) deep sediments and suggested that this process can be an important global methane sink. The goal of the present study was to link the geochemical gradients found in the porewater (chemical and isotope profiles) with possible changes in microbial community structure. Specifically, we examined the possible shift in the microbial community in the deep iron-driven AOM zone and its similarity to known sulfate driven AOM populations. Screening of archaeal 16S rRNA gene sequences revealed Thaumarchaeota and Euryarchaeota as the dominant phyla in the sediment. Thaumarchaeota, which belongs to the family of copper containing membrane-bound monooxgenases, increased with depth while Euryarchaeota decreased. This may indicate the involvement of Thaumarchaeota, which were discovered to be ammonia oxidizers but whose activity could also be linked to methane, in AOM in the deep sediment. ANMEs sequences were not found in the clone libraries, suggesting that iron-driven AOM is not through sulfate. Bacterial 16S rRNA sequences displayed shifts in community diversity with depth. Proteobacteria and Chloroflexi increased with depth, which could be connected with their different dissimilatory anaerobic processes. The observed changes in microbial community structure suggest possible direct and indirect mechanisms for iron-driven AOM in deep sediments.

Heat as a groundwater tracer in shallow and deep heterogeneous media: Analytical solution, spreadsheet tool, and field applications

USGS Publications Warehouse

Kurylyk, Barret L.; Irvine, Dylan J.; Carey, Sean K.; Briggs, Martin A.; Werkema, Dale D.; Bonham, Mariah

2017-01-01

Groundwater flow advects heat, and thus, the deviation of subsurface temperatures from an expected conduction‐dominated regime can be analysed to estimate vertical water fluxes. A number of analytical approaches have been proposed for using heat as a groundwater tracer, and these have typically assumed a homogeneous medium. However, heterogeneous thermal properties are ubiquitous in subsurface environments, both at the scale of geologic strata and at finer scales in streambeds. Herein, we apply the analytical solution of Shan and Bodvarsson (2004), developed for estimating vertical water fluxes in layered systems, in 2 new environments distinct from previous vadose zone applications. The utility of the solution for studying groundwater‐surface water exchange is demonstrated using temperature data collected from an upwelling streambed with sediment layers, and a simple sensitivity analysis using these data indicates the solution is relatively robust. Also, a deeper temperature profile recorded in a borehole in South Australia is analysed to estimate deeper water fluxes. The analytical solution is able to match observed thermal gradients, including the change in slope at sediment interfaces. Results indicate that not accounting for layering can yield errors in the magnitude and even direction of the inferred Darcy fluxes. A simple automated spreadsheet tool (Flux‐LM) is presented to allow users to input temperature and layer data and solve the inverse problem to estimate groundwater flux rates from shallow (e.g., <1 m) or deep (e.g., up to 100 m) profiles. The solution is not transient, and thus, it should be cautiously applied where diel signals propagate or in deeper zones where multi‐decadal surface signals have disturbed subsurface thermal regimes.

The role microbial sulfate reduction in the direct mediation of sedimentary authigenic carbonate precipitation

NASA Astrophysics Data System (ADS)

Turchyn, A. V.; Walker, K.; Sun, X.

2016-12-01

The majority of modern deep marine sediments are bathed in water that is undersaturated with respect to calcium carbonate. However, within marine sediments changing chemical conditions, driven largely by the microbial oxidation of organic carbon in the absence of oxygen, lead to supersaturated conditions and drive calcium carbonate precipitation. This sedimentary calcium carbonate is often called `authigenic carbonate', and is found in the form of cements and disseminated crystals within the marine sedimentary pile. As this precipitation of this calcium carbonate is microbially mediated, identifying authigenic carbonate within the geological record and understanding what information its geochemical and/or isotopic signature may hold is key for understanding its importance and what information it may contain past life. However, the modern controls on authigenic carbonate precipitation remain enigmatic because the myriad of microbially mediated reactions occurring within sediments both directly and indirectly impact the proton balance. In this submission we present data from 25 ocean sediment cores spanning the globe where we explore the deviation from the stoichiometrically predicted relationships among alkalinity, calcium and sulfate concentrations. In theory for every mol of organic carbon reduced by sulfate, two mol of alkalinity is produced, and to precipitate subsurface calcium carbonate one mol of calcium is used to consume two mol of alkalinity. We use this data with a model to explore changes in carbonate saturation state with depth below the seafloor. Alkalinity changes in the subsurface are poorly correlated with changes in calcium concentrations, however calcium concentrations are directly and tightly coupled to changes in sulfate concentrations in all studied sites. This suggests a direct role for sulfate reducing bacteria in the precipitation of subsurface carbonate cements.

2500 high-quality genomes reveal that the biogeochemical cycles of C, N, S and H are cross-linked by metabolic handoffs in the terrestrial subsurface

NASA Astrophysics Data System (ADS)

Anantharaman, K.; Brown, C. T.; Hug, L. A.; Sharon, I.; Castelle, C. J.; Shelton, A.; Bonet, B.; Probst, A. J.; Thomas, B. C.; Singh, A.; Wilkins, M.; Williams, K. H.; Tringe, S. G.; Beller, H. R.; Brodie, E.; Hubbard, S. S.; Banfield, J. F.

2015-12-01

Microorganisms drive the transformations of carbon compounds in the terrestrial subsurface, a key reservoir of carbon on earth, and impact other linked biogeochemical cycles. Our current knowledge of the microbial ecology in this environment is primarily based on 16S rRNA gene sequences that paint a biased picture of microbial community composition and provide no reliable information on microbial metabolism. Consequently, little is known about the identity and metabolic roles of the uncultivated microbial majority in the subsurface. In turn, this lack of understanding of the microbial processes that impact the turnover of carbon in the subsurface has restricted the scope and ability of biogeochemical models to capture key aspects of the carbon cycle. In this study, we used a culture-independent, genome-resolved metagenomic approach to decipher the metabolic capabilities of microorganisms in an aquifer adjacent to the Colorado River, near Rifle, CO, USA. We sequenced groundwater and sediment samples collected across fifteen different geochemical regimes. Sequence assembly, binning and manual curation resulted in the recovery of 2,542 high-quality genomes, 27 of which are complete. These genomes represent 1,300 non-redundant organisms comprising both abundant and rare community members. Phylogenetic analyses involving ribosomal proteins and 16S rRNA genes revealed the presence of up to 34 new phyla that were hitherto unknown. Less than 11% of all genomes belonged to the 4 most commonly represented phyla that constitute 93% of all currently available genomes. Genome-specific analyses of metabolic potential revealed the co-occurrence of important functional traits such as carbon fixation, nitrogen fixation and use of electron donors and electron acceptors. Finally, we predict that multiple organisms are often required to complete redox pathways through a complex network of metabolic handoffs that extensively cross-link subsurface biogeochemical cycles.

Comparisons of the hydraulics of water flows in Martian outflow channels with flows of similar scale on earth

NASA Technical Reports Server (NTRS)

Komar, P. D.

1979-01-01

The hydraulics of channelized water flows on Mars and the resulting sediment transport rates are calculated, and similar computations are performed for such terrestrial analogs as the Mississippi River and the catastrophic Lake Missoula floods that formed the Channeled Scabland in eastern Washington State. The morphologies of deep-sea channels formed by catastrophic turbidity currents are compared with the Martian channels, many similarities are pointed out, and the hydraulics of the various flows are compared. The results indicate that the velocities, discharges, bottom shear stresses, and sediment-transport capacity of water flows along the Martian channels would be comparable to those of the oceanic turbidity currents and the Lake Missoula floods. It is suggested that the submarine canyons from which turbidity currents originate are the terrestrial counterparts to the chaotic-terrain areas or craters that serve as sources for many of the Martian channels.

Organic geochemistry of sediments of deep Gulf of Mexico basin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, J.; Sassen, R.; Nunn, J.

1989-09-01

An analysis of 716 core samples from DSDP (Deep Sea Drilling Project) Leg 96 in the Mississippi submarine fan and the Orca and Pigmy basins in the Louisiana continental slope was done using a Rock-Eval pyrolysis unit with TOC (total organic carbon) module. The analysis allows computation of the hydrogen index (HI), TOC, and kerogen type, and assessment of the oil-generative capacity of the sediments in the Louisiana continental slope. No samples are obviously oil prone. TOC content ranges from 0.12 to 2.29%, with an overall average of 0.82%. HI values are generally less than 150 mg HC/g TOC. T{submore » max} (temperature of the maximum of the S{sub 2} peak) values (425{degree}C average) show the sediments are immature throughout the study area. Hydrocarbon-generative potential of the sediments ranges from 492 to 1,107 ppm, with an average of 854 ppm. Because of organic lean, thermally immature, and gas-prone terrestrial organic matter, there is little reason to assume that the sediments from the Mississippi fan can provide oil source rock for the Gulf Coast basin, and that sediments of anoxic basins in the Louisiana continental slope are analogs to the past environments where source rocks for crude oil have been deposited.« less

Regional biostratigraphy and paleoenvironmental history of Miocene of onshore and offshore Alabama

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, C.C.

1989-09-01

Subsurface Miocene sediments of coastal Alabama and the adjoining state and federal waters consist of a clastic wedge varying in thickness from less than 1,000 ft in southern Alabama to a maximum of about 6,000 ft in the northeastern portion of the Main Pass area. Relatively deep-water and open-marine transgressive basal Miocene clays and shales unconformably overlie a gently southwestward-dipping late Oligocene-earliest Miocene carbonate platform. Middle and late Miocene sediments consist of a regressive offlapping sequence of sand and shale deposited in varying neritic paleoenvironments. Analysis of planktonic and benthonic foraminifera has resulted in a refined biostratigraphic zonation of thesemore » sediments, permitting the recognition of several regional time-equivalent datum levels, or biohorizons. These biohorizons are shown on a series of subsurface cross sections that show the dramatic southwestward thickening of middle and late Miocene sediments as well as illustrate the relationships of the producing intervals within the Cibicides carstensi and Discorbis 12 interval zones. The paleoenvironmental history of the Miocene has been reconstructed on a series of paleobathymetric maps drawn for selected regional biohorizons. Among other features, these maps have proven the existence and outlined the margins of previously unrecognized shallow-meritic deltaic sediments in southeastern Mobile County and in the Chandeleur and Viosca Knoll (north) areas. Analysis of sedimentation rates, which range from less than 25 to 1,370 ft/m.y., further aids in understanding the coastal shelf, deltaic, and open-marine depositional history of the Miocene of Alabama and the adjoining state and federal waters.« less

Tracking small mountainous river derived terrestrial organic carbon across the active margin marine environment

NASA Astrophysics Data System (ADS)

Childress, L. B.; Blair, N. E.; Orpin, A. R.

2015-12-01

Active margins are particularly efficient in the burial of organic carbon due to the close proximity of highland sources to marine sediment sinks and high sediment transport rates. Compared with passive margins, active margins are dominated by small mountainous river systems, and play a unique role in marine and global carbon cycles. Small mountainous rivers drain only approximately 20% of land, but deliver approximately 40% of the fluvial sediment to the global ocean. Unlike large passive margin systems where riverine organic carbon is efficiently incinerated on continental shelves, small mountainous river dominated systems are highly effective in the burial and preservation of organic carbon due to the rapid and episodic delivery of organic carbon sourced from vegetation, soil, and rock. To investigate the erosion, transport, and burial of organic carbon in active margin small mountainous river systems we use the Waipaoa River, New Zealand. The Waipaoa River, and adjacent marine depositional environment, is a system of interest due to a large sediment yield (6800 tons km-2 yr-1) and extensive characterization. Previous studies have considered the biogeochemistry of the watershed and tracked the transport of terrestrially derived sediment and organics to the continental shelf and slope by biogeochemical proxies including stable carbon isotopes, lignin phenols, n-alkanes, and n-fatty acids. In this work we expand the spatial extent of investigation to include deep sea sediments of the Hikurangi Trough. Located in approximately 3000 m water depth 120 km from the mouth of the Waipaoa River, the Hikurangi Trough is the southern extension of the Tonga-Kermadec-Hikurangi subduction system. Piston core sediments collected by the National Institute of Water and Atmospheric Research (NIWA, NZ) in the Hikurangi Trough indicate the presence of terrestrially derived material (lignin phenols), and suggest a continuum of deposition, resuspension, and transport across the margin. Based on tephra beds identified within the sediments, this material was likely transported by a series of turbidite events, delivered to the Hikurangi Trough through Poverty Canyon.

Pacific Northwest Laboratory annual report for 1992 to the DOE Office of Energy Research

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grove, L.K.

1993-03-01

The 1992 Annual Report from Pacific Northwest Laboratory (PNL) to the US Department of Energy (DOE) describes research in environment and health conducted during fiscal year 1992. This report consists of four volumes oriented to particular segments of the PNL program, describing research performed for the DOE Office of Health and Environmental Research in the Office of Energy Research. The parts of the 1992 Annual Report are: Biomedical Sciences; Environmental Sciences; Atmospheric Sciences; and Physical Sciences. This Report is Part II: Environmental Sciences. Included in this report are developments in Subsurface Science, Terrestrial Science, Laboratory-Directed Research and Development, Interactions withmore » Educational Institutions, Technology Transfer, Publications, and Presentations. The research is directed toward developing a fundamental understanding of subsurface and terrestrial systems as a basis for both managing these critical resources and addressing environmental problems such as environmental restoration and global change. The Technology Transfer section of this report describes a number of examples in which fundamental research is laying the groundwork for the technology needed to resolve important environmental problems. The Interactions with Educational Institutions section of the report illustrates the results of a long-term, proactive program to make PNL facilities available for university and preuniversity education and to involve educational institutions in research programs. The areas under investigation include the effect of geochemical and physical phenomena on the diversity and function of microorganisms in deep subsurface environments, ways to address subsurface heterogeneity, and ways to determine the key biochemical and physiological pathways (and DNA markers) that control nutrient, water, and energy dynamics in arid ecosystems and the response of these systems to disturbance and climatic change.« less

Pacific Northwest Laboratory annual report for 1992 to the DOE Office of Energy Research. Part 2, Environmental sciences

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grove, L.K.; Wildung, R.E.

1993-03-01

The 1992 Annual Report from Pacific Northwest Laboratory (PNL) to the US Department of Energy (DOE) describes research in environment and health conducted during fiscal year 1992. This report consists of four volumes oriented to particular segments of the PNL program, describing research performed for the DOE Office of Health and Environmental Research in the Office of Energy Research. The parts of the 1992 Annual Report are: Biomedical Sciences; Environmental Sciences; Atmospheric Sciences; and Physical Sciences. This Report is Part 2: Environmental Sciences. Included in this report are developments in Subsurface Science, Terrestrial Science, Laboratory-Directed Research and Development, Interactions withmore » Educational Institutions, Technology Transfer, Publications, and Presentations. The research is directed toward developing a fundamental understanding of subsurface and terrestrial systems as a basis for both managing these critical resources and addressing environmental problems such as environmental restoration and global change. The Technology Transfer section of this report describes a number of examples in which fundamental research is laying the groundwork for the technology needed to resolve important environmental problems. The Interactions with Educational Institutions section of the report illustrates the results of a long-term, proactive program to make PNL facilities available for university and preuniversity education and to involve educational institutions in research programs. The areas under investigation include the effect of geochemical and physical phenomena on the diversity and function of microorganisms in deep subsurface environments, ways to address subsurface heterogeneity, and ways to determine the key biochemical and physiological pathways (and DNA markers) that control nutrient, water, and energy dynamics in arid ecosystems and the response of these systems to disturbance and climatic change.« less

Shallow Investigations of the Deep Seafloor: Quantitative Morphology in the Levant Basin, Eastern Mediterranean

NASA Astrophysics Data System (ADS)

Kanari, M.; Ketter, T.; Tibor, G.; Schattner, U.

2017-12-01

We aim to characterize the seafloor morphology and its shallow sub-surface structures and deformations in the deep part of the Levant basin (eastern Mediterranean) using recently acquired high-resolution shallow seismic reflection data and multibeam bathymetry, which allow quantitative analysis of morphology and structure. The Levant basin at the eastern Mediterranean is considered a passive continental margin, where most of the recent geological processes were related in literature to salt tectonics rooted at the Messinian deposits from 6Ma. We analyzed two sets of recently acquired high-resolution data from multibeam bathymetry and 3.5 kHz Chirp sub-bottom seismic reflection in the deep basin of the continental shelf offshore Israel (water depths up to 2100 m). Semi-automatic mapping of seafloor features and seismic data interpretation resulted in quantitative morphological analysis of the seafloor and its underlying sediment with penetration depth up to 60 m. The quantitative analysis and its interpretation are still in progress. Preliminary results reveal distinct morphologies of four major elements: channels, faults, folds and sediment waves, validated by seismic data. From the spatial distribution and orientation analyses of these phenomena, we identify two primary process types which dominate the formation of the seafloor in the Levant basin: structural and sedimentary. Characterization of the geological and geomorphological processes forming the seafloor helps to better understand the transport mechanisms and the relations between sediment transport and deposition in deep water and the shallower parts of the shelf and slope.

Are deep-sea ecosystems surrounding Madagascar threatened by land-use or climate change?

NASA Astrophysics Data System (ADS)

Fontanier, Christophe; Mamo, Briony; Toucanne, Samuel; Bayon, Germain; Schmidt, Sabine; Deflandre, Bruno; Dennielou, Bernard; Jouet, Gwenael; Garnier, Eline; Sakai, Saburo; Lamas, Ruth Martinez; Duros, Pauline; Toyofuku, Takashi; Salé, Aurélien; Belleney, Déborah; Bichon, Sabrina; Boissier, Audrey; Chéron, Sandrine; Pitel, Mathilde; Roubi, Angélique; Rovere, Mickaël; Grémare, Antoine; Dupré, Stéphanie; Jorry, Stéphan J.

2018-01-01

In this short communication, we present a multidisciplinary study of sedimentary records collected from a deep-sea interfluve proximal to the mouths of major northwestern Madagascan rivers. For the last 60 years, the seafloor has been repeatedly disturbed by the deposition of organic rich, tropical, terrestrial sediments causing marked reductions in benthic biodiversity. Increased soil erosion due to local land-use, deforestation and intensifying tropical cyclones are potential causes for this sedimentary budget and biodiversity shift. Our marine sedimentary records indicate that until now, these conditions have not occurred within the region for at least 20,000 years.

Some New Windows into Terrestrial Deep Subsurface Microbial Ecosystems

NASA Astrophysics Data System (ADS)

Moser, D. P.

2011-12-01

Over the past several years, our group has surveyed the microbial ecology and biogeochemistry of a range of fracture rock subsurface ecosystems via deep mine boreholes in South Africa, the United States, and Canada; and boreholes from surface or deeply-sourced natural springs of the U.S. Great Basin. Collectively, these mostly unexplored habitats represent a wide range of geologic provinces, host rock types, aquatic chemistries, and the vast potential for biogeographic isolation. Thus, patterns of microbial diversity are of interest from the perspective of filling a fundamental knowledge gap; and while not necessarily expected, the detection of closely related microorganisms from geographically isolated settings would be noteworthy. Across these sample sets, microbial communities were invariably very low in biomass (e.g. 10e3 - 10e4 cells per mL) and dominated by deeply-branching bacterial lineages, particularly from the phyla Firmicutes and Nitrospira. In several cases, the Firmicutes have shown very close phylogenetic affiliations to lineages detected at divergent locations. For example, one abundant lineage from a new artesian well drilled into the Furnace Creek Fault of Death Valley, CA bears a very close phylogenetic relatedness to environmental DNA sequences (SSU rRNA gene) detected in one of the world's deepest mines (Tau Tona of South Africa) and what was North America's deepest gold mine (Homestake of South Dakota). Several radioactive wells from the Nevada National Security Site have produced rRNA gene sequences very close (e.g. greater than 99% identity) to that of Desulforudis audaxviator, a rarely detected microorganism thought to subsist as a single species ecosystem on the products of radiochemical reactions in deep crustal rocks from the South African Witwatersrand Basin. These sequences, along with more distantly related sequences from the marine subsurface (ridge flank basalt and mud volcanoes) and groundwater in Europe, hint at a role in certain hydrogen-rich subsurface settings for this group. Likewise, patterns of archaeal diversity across many of our Great Basin sites suggest shared deep lineages, particularly with the phylum, Thaumarchaeota. Here we will explore the possible significance of these patterns of diversity and discuss future research plans involving high throughput molecular techniques.

New Bio-Indicators for Long Term Natural Attenuation of Monoaromatic Compounds in Deep Terrestrial Aquifers

PubMed Central

Aüllo, Thomas; Berlendis, Sabrina; Lascourrèges, Jean-François; Dessort, Daniel; Duclerc, Dominique; Saint-Laurent, Stéphanie; Schraauwers, Blandine; Mas, Johan; Patriarche, Delphine; Boesinger, Cécile; Magot, Michel; Ranchou-Peyruse, Anthony

2016-01-01

Deep subsurface aquifers despite difficult access, represent important water resources and, at the same time, are key locations for subsurface engineering activities for the oil and gas industries, geothermal energy, and CO2 or energy storage. Formation water originating from a 760 m-deep geological gas storage aquifer was sampled and microcosms were set up to test the biodegradation potential of BTEX by indigenous microorganisms. The microbial community diversity was studied using molecular approaches based on 16S rRNA genes. After a long incubation period, with several subcultures, a sulfate-reducing consortium composed of only two Desulfotomaculum populations was observed able to degrade benzene, toluene, and ethylbenzene, extending the number of hydrocarbonoclastic–related species among the Desulfotomaculum genus. Furthermore, we were able to couple specific carbon and hydrogen isotopic fractionation during benzene removal and the results obtained by dual compound specific isotope analysis (𝜀C = -2.4‰ ± 0.3‰; 𝜀H = -57‰ ± 0.98‰; AKIEC: 1.0146 ± 0.0009, and AKIEH: 1.5184 ± 0.0283) were close to those obtained previously in sulfate-reducing conditions: this finding could confirm the existence of a common enzymatic reaction involving sulfate-reducers to activate benzene anaerobically. Although we cannot assign the role of each population of Desulfotomaculum in the mono-aromatic hydrocarbon degradation, this study suggests an important role of the genus Desulfotomaculum as potential biodegrader among indigenous populations in subsurface habitats. This community represents the simplest model of benzene-degrading anaerobes originating from the deepest subterranean settings ever described. As Desulfotomaculum species are often encountered in subsurface environments, this study provides some interesting results for assessing the natural response of these specific hydrologic systems in response to BTEX contamination during remediation projects. PMID:26904000

Río Tinto: A Geochemical and Mineralogical Terrestrial Analogue of Mars

NASA Astrophysics Data System (ADS)

Amils, Ricardo; Fernández-Remolar, David

2014-09-01

The geomicrobiological characterization of the water column and sediments of Río Tinto (Huelva, Southwestern Spain) have proven the importance of the iron and the sulfur cycles, not only in generating the extreme conditions of the habitat (low pH, high concentration of toxic heavy metals), but also in maintaining the high level of microbial diversity detected in the basin. It has been proven that the extreme acidic conditions of Río Tinto basin are not the product of 5000 years of mining activity in the area, but the consequence of an active underground bioreactor that obtains its energy from the massive sulfidic minerals existing in the Iberian Pyrite Belt. Two drilling projects, MARTE (Mars Astrobiology Research and Technology Experiment) (2003-2006) and IPBSL (Iberian Pyrite Belt Subsurface Life Detection) (2011-2015), were developed and carried out to provide evidence of subsurface microbial activity and the potential resources that support these activities. The reduced substrates and the oxidants that drive the system appear to come from the rock matrix. These resources need only groundwater to launch diverse microbial metabolisms. The similarities between the vast sulfate and iron oxide deposits on Mars and the main sulfide bioleaching products found in the Tinto basin have given Río Tinto the status of a geochemical and mineralogical Mars terrestrial analogue.

Martian mud volcanism: Terrestrial analogs and implications for formational scenarios

USGS Publications Warehouse

Skinner, J.A.; Mazzini, A.

2009-01-01

The geology of Mars and the stratigraphic characteristics of its uppermost crust (mega-regolith) suggest that some of the pervasively-occurring pitted cones, mounds, and flows may have formed through processes akin to terrestrial mud volcanism. A comparison of terrestrial mud volcanism suggests that equivalent Martian processes likely required discrete sedimentary depocenters, volatile-enriched strata, buried rheological instabilities, and a mechanism of destabilization to initiate subsurface flow. We outline five formational scenarios whereby Martian mud volcanism might have occurred: (A) rapid deposition of sediments, (B) volcano-induced destabilization, (C) tectonic shortening, (D) long-term, load-induced subsidence, and (E) seismic shaking. We describe locations within and around the Martian northern plains that broadly fit the geological context of these scenarios and which contain mud volcano-like landforms. We compare terrestrial and Martian satellite images and examine the geological settings of mud volcano provinces on Earth in order to describe potential target areas for piercement structures on Mars. Our comparisons help to evaluate not only the role of water as a functional component of geological processes on Mars but also how Martian mud volcanoes could provide samples of otherwise inaccessible strata, some of which could contain astrobiological evidence.

Correlation of sea level falls interpreted from atoll stratigraphy with turbidites in adjacent basins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lincoln, J.M.

Past sea levels can be derived from any atoll subsurface sediments deposited at or near sea level by determining the ages of deposition and correcting the present depths to the sediments for subsidence of the underlying edifice since the times of deposition. A sea level curve constructed by this method consists of discontinuous segments, each corresponding to a period of rising relative sea level and deposition of a discrete sedimentary package. Discontinuities in the sea level curve derived by this method correspond to relative sea level falls and stratigraphic hiatuses in the atoll subsurface. During intervals of relative sea levelmore » fall an atoll emerges to become a high limestone island. Sea level may fluctuate several times during a period of atoll emergence to become a high limestone island. Sea level may fluctuate several times during a period of atoll emergence without depositing sediments on top of the atoll. Furthermore, subaerial erosion may remove a substantial part of the depositional record of previous sea level fluctuations. For these reasons the authors must look to the adjacent basins to complement the incomplete record of sea level change recorded beneath atolls. During lowstands of sea level, faunas originally deposited near sea level on an atoll may be eroded and redeposited as turbidites in deep adjacent basins. Three such turbidites penetrated during deep-sea drilling at Sites 462 and 315 in the central Pacific correlate well with a late Tertiary sea level curve based on biostratigraphic ages and {sup 87}Sr/{sup 86}Sr chronostratigraphy for core from Enewetak Atoll in the northern Marshall Islands. Further drilling of the archipelagic aprons adjacent to atolls will improve the sea level history that may be inferred from atoll stratigraphy.« less

Homology between genes for aromatic hydrocarbon degradation in surface and deep-subsurface sphingomonas strains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, E.; Aversano, P.J.; Zylstra, G.J.

The cloned genes for aromatic hydrocarbon degradation from Sphingomonas yanoikuyae B1 were utilized in Southern hybridization experiments with Sphingomonas strains from the surface and deep-subsurface environments. One hybridization pattern was obtained with BamHI-digested genomic DNAs for two surface strains, while a differing pattern was seen for five deep-subsurface strains. The cross-hybridizing genes were located in the chromosomes of the surface strains and on plasmids in the deep-subsurface strains. 31 refs., 3 figs., 1 tab.

Geophysical Investigation of a Thermokarst Lake Talik in Continuous Permafrost

NASA Astrophysics Data System (ADS)

Creighton, A.; Parsekian, A.; Arp, C. D.; Jones, B. M.; Babcock, E.; Bondurant, A. C.

2016-12-01

On the Arctic Coastal Plain (ACP) of northern Alaska, shallow thermokarst lakes cover up to 25% of the landscape. These lakes occupy depressions created by the subsidence of thawed, ice-rich permafrost. Areas of unfrozen sediment, or taliks, can form under lakes that have a mean annual bottom temperature greater than 0°C. The geometry of these taliks, as well as the processes that create them, are important for understanding interactions between surface water, groundwater, and carbon cycling. Non-invasive geophysical methods are a useful means to study talik sediments as borehole studies yield few data points, and the contrast between unfrozen and frozen sediments is an ideal geophysical target. To study talik configuration associated with an actively expanding thermokarst lake, we conducted a geophysical transect across Peatball Lake. This lake has an estimated initiation age of 1400 calendar years BP. Over the past 60 years, lake surface area has increased through thermal and mechanical shoreline erosion. A talik of previously unknown thickness likely exists below Peatball Lake. We conducted a transect of transient electromagnetic soundings across the lake extending into the surrounding terrestrial environment. Since permafrost has relatively high resistivity compared to talik sediments, the interpreted electrical structure of the subsurface likely reflects talik geometry. We also conducted nuclear magnetic resonance soundings at representative locations along the transect. These measurements can provide data on sub-lake sediment properties including water content. Together, these measurements resolve the talik structure across the lake transect and showed evidence of varying talik thicknesses from the lake edge to center. These is no evidence of a talik at the terrestrial control sites. These results can help constrain talik development models and thus provide insight into Arctic and permafrost processes in the face of a changing climate.

Anthropogenic activities have contributed moderately to increased inputs of organic materials in marginal seas off China.

PubMed

Liu, Liang-Ying; Wei, Gao-Ling; Wang, Ji-Zhong; Guan, Yu-Feng; Wong, Charles S; Wu, Feng-Chang; Zeng, Eddy Y

2013-10-15

Sediment has been recognized as a gigantic sink of organic materials and therefore can record temporal input trends. To examine the impact of anthropogenic activities on the marginal seas off China, sediment cores were collected from the Yellow Sea, the inner shelf of the East China Sea (ECS), and the South China Sea (SCS) to investigate the sources and spatial and temporal variations of organic materials, i.e., total organic carbon (TOC) and aliphatic hydrocarbons. The concentration ranges of TOC were 0.5-1.29, 0.63-0.83, and 0.33-0.85%, while those of Σn-C14-35 (sum of n-alkanes with carbon numbers of 14-35) were 0.08-1.5, 0.13-1.97, and 0.35-0.96 μg/g dry weight in sediment cores from the Yellow Sea, ECS inner shelf, and the SCS, respectively. Terrestrial higher plants were an important source of aliphatic hydrocarbons in marine sediments off China. The spatial distribution of Σn-C14-35 concentrations and source diagnostic ratios suggested a greater load of terrestrial organic materials in the Yellow Sea than in the ECS and SCS. Temporally, TOC and Σn-C14-35 concentrations increased with time and peaked at either the surface or immediate subsurface layers. This increase was probably reflective of elevated inputs of organic materials to marginal seas off China in recent years, and attributed partly to the impacts of intensified anthropogenic activities in mainland China. Source diagnostics also suggested that aliphatic hydrocarbons were mainly derived from biogenic sources, with a minority in surface sediment layers from petroleum sources, consistent with the above-mentioned postulation.

Estimating sedimentation rates and sources in a partially urbanized catchment using caesium-137

NASA Astrophysics Data System (ADS)

Ormerod, L. M.

1998-06-01

While there has been increased interest in determining sedimentation rates and sources in agricultural and forested catchments in recent years, there have been few studies dealing with urbanized catchments. A study of sedimentation rates and sources within channel and floodplain deposits of a partially urbanized catchment has been undertaken using the 137Cs technique. Results for sedimentation rates showed no particular downstream pattern. This may be partially explained by underestimation of sedimentation rates at some sites by failure to sample the full 137Cs profile, floodplain erosion and deliberate removal of sediment. Evidence of lateral increases in net sedimentation rates with distance from the channel may be explained by increased floodplain erosion at sites closer to the channel and floodplain formation by lateral deposition. Potential sediment sources for the catchment were considered to be forest topsoil, subsurface material and sediments derived from urban areas, which were found to be predominantly subsurface material. Tracing techniques showed an increase in subsurface material for downstream sites, confirming expectations that subsurface material would increase in the downstream direction in response to the direct and indirect effects of urbanization.

Mapping bedrock surface contours using the horizontal-to-vertical spectral ratio (HVSR) method near the middle quarter srea, Woodbury, Connecticut

USGS Publications Warehouse

Brown, Craig J.; Voytek, Emily B.; Lane, John W.; Stone, Janet R.

2013-01-01

The bedrock surface contours in Woodbury, Connecticut, were determined downgradient of a commercial zone known as the Middle Quarter area (MQA) using the novel, noninvasive horizontal-to-vertical (H/V) spectral ratio (HVSR) passive seismic geophysical method. Boreholes and monitoring wells had been drilled in this area to characterize the shallow subsurface to within 20 feet (ft) of the land surface, but little was known about the deep subsurface, including sediment thicknesses and depths to bedrock (Starn and Brown, 2007; Brown and others, 2009). Improved information on the altitude of the bedrock surface and its spatial variation was needed for assessment and remediation of chlorinated solvents that have contaminated the overlying glacial aquifer that supplies water to wells in the area.

The subsurface record for the Anthropocene based on the global analysis of deep wells

NASA Astrophysics Data System (ADS)

Rose, K.

2016-12-01

While challenges persist in the characterization of Earth's subsurface, over two centuries of exploration resulting in more than six million deep wellbores, offer insights into these systems. Characteristics of the subsurface vary and can be analyzed on a variety of spatial scales using geospatial tools and methods. Characterization and prediction of subsurface properties, such as depth, thickness, porosity, permeability, pressure and temperature, are important for models and interpretations of the subsurface. Subsurface studies contribute to insights and understanding of natural system but also enable predictions and assessments of subsurface resources and support environmental and geohazard assessments. As the geo-data science landscape shifts, becoming more open, there are increasing opportunities to fill knowledge gaps, mine large, interrelated datasets, and develop innovative methods to improve our understanding of the subsurface and the impacts of its exploration. In this study, a global dataset of more than 6,000,000 deep subsurface wells has been assembled using ArcGIS and Access, which reflects to a first order, the cumulative representation of over two centuries of drilling. Wellbore data, in general represent the only portal for direct measurement and characterization of deep subsurface properties. As human engineering of the subsurface evolves from a focus on hydrocarbon resource development to include subsurface waste product disposal (e.g. CO2, industrial waste, etc) and production of other deep subsurface resources, such as heat and water resources, there is the increasing need to improve characterization techniques and understand local and global ramifications of anthropogenic interaction with the subsurface. Data and geospatial analyses are reviewed to constrain the extent to which human interactions, not just with Earth's surface systems, atmospheric and geologic, but subsurface systems will result in an enduring signature of human influences on the planet. Specifically, the extent and enduring signature of subsurface interactions with the planet, utilizing the four-dimensional, spatial and temporal, record for known deep wellbores is utilized.

Viral Predation and Host Immunity Structure Microbial Communities in a Terrestrial Deep Subsurface, Hydraulically Fractured Shale System

NASA Astrophysics Data System (ADS)

Daly, R. A.; Mouser, P. J.; Trexler, R.; Wrighton, K. C.

2014-12-01

Despite a growing appreciation for the ecological role of viruses in marine and gut systems, little is known about their role in the terrestrial deep (> 2000 m) subsurface. We used assembly-based metagenomics to examine the viral component in fluids from hydraulically fractured Marcellus shale gas wells. Here we reconstructed microbial and viral genomes from samples collected 7, 82, and 328 days post fracturing. Viruses accounted for 4.14%, 0.92% and 0.59% of the sample reads that mapped to the assembly. We identified 6 complete, circularized viral genomes and an additional 92 viral contigs > 5 kb with a maximum contig size of 73.6 kb. A BLAST comparison to NCBI viral genomes revealed that 85% of viral contigs had significant hits to the viral order Caudovirales, with 43% of sequences belonging to the family Siphoviridae, 38% to Myoviridae, and 12% to Podoviridae. Enrichment of Caudovirales viruses was supported by a large number of predicted proteins characteristic of tailed viruses including terminases (TerL), tape measure, tail formation, and baseplate related proteins. The viral contigs included evidence of lytic and temperate lifestyles, with the 7 day sample having the greatest number of detected lytic viruses. Notably in this sample, the most abundant virus was lytic and its inferred host, a member of the Vibrionaceae, was not detected at later time points. Analyses of CRISPR sequences (a viral and foreign DNA immune system in bacteria and archaea), linked 18 viral contigs to hosts. CRISPR linkages increased through time and all bacterial and archaeal genomes recovered in the final time point had genes for CRISPR-mediated viral defense. The majority of CRISPR sequences linked phage genomes to several Halanaerobium strains, which are the dominant and persisting members of the community inferred to be responsible for carbon and sulfur cycling in these shales. Network analysis revealed that several viruses were present in the 82 and 328 day samples; this viral persistence is consistent with concomitant temporal stability in geochemistry and microbial community composition. Our findings suggest that after a disturbance (hydraulic fracturing) viral predation and host immunity is an important controller of microbial community structure, metabolism, and thus biogeochemical cycling in the deep subsurface.

New temperature model of the Netherlands from new data and novel modelling methodology

NASA Astrophysics Data System (ADS)

Bonté, Damien; Struijk, Maartje; Békési, Eszter; Cloetingh, Sierd; van Wees, Jan-Diederik

2017-04-01

Deep geothermal energy has grown in interest in Western Europe in the last decades, for direct use but also, as the knowledge of the subsurface improves, for electricity generation. In the Netherlands, where the sector took off with the first system in 2005, geothermal energy is seen has a key player for a sustainable future. The knowledge of the temperature subsurface, together with the available flow from the reservoir, is an important factor that can determine the success of a geothermal energy project. To support the development of deep geothermal energy system in the Netherlands, we have made a first assessment of the subsurface temperature based on thermal data but also on geological elements (Bonté et al, 2012). An outcome of this work was ThermoGIS that uses the temperature model. This work is a revision of the model that is used in ThermoGIS. The improvement from the first model are multiple, we have been improving not only the dataset used for the calibration and structural model, but also the methodology trough an improved software (called b3t). The temperature dataset has been updated by integrating temperature on the newly accessible wells. The sedimentary description in the basin has been improved by using an updated and refined structural model and an improved lithological definition. A major improvement in from the methodology used to perform the modelling, with b3t the calibration is made not only using the lithospheric parameters but also using the thermal conductivity of the sediments. The result is a much more accurate definition of the parameters for the model and a perfected handling of the calibration process. The result obtain is a precise and improved temperature model of the Netherlands. The thermal conductivity variation in the sediments associated with geometry of the layers is an important factor of temperature variations and the influence of the Zechtein salt in the north of the country is important. In addition, the radiogenic heat production in the crust shows a significant impact. From the temperature values, also identify in the lower part of the basin, deep convective systems that could be major geothermal energy target in the future.

Fate of permafrost-released organic matter in the Laptev Sea: What is its lateral transport time along the transect from the Lena delta area to the deep sea of the Arctic interior?

NASA Astrophysics Data System (ADS)

Bröder, L.; Tesi, T.; Bruchert, V.; Dudarev, O.; Semiletov, I. P.; Gustafsson, O.

2015-12-01

Ongoing global warming may cause an increasing supply of permafrost-derived organic carbon through both river discharge and coastal erosion to the Arctic shelves where it can be either degraded to CO2 and outgassed, buried in sediments or transported to the deep sea. Here we assess the balance between burial and lateral transport on the fate of terrestrial organic carbon (TerrOC) by exploring how it changes in concentration, composition and degradation status during both cross-shelf transport and burial. We analyzed a suite of terrestrial biomarkers as well as source-diagnostic bulk carbon isotopes (δ13C, Δ14C) in sediments from the wide Siberian Arctic Shelf and found contrasting trends for the operationally-defined carbon pools. TerrOC concentrations and degradation status vary noticeably more during cross-shelf transport than after burial. The concentrations of lignin phenols, cutin acids and high-molecular weight (HMW) wax lipids (tracers of vascular plants) do not display clear changes over time during sediment accumulation, while they significantly decrease along the transect. Molecular-based degradation proxies for TerrOC (e.g., CPI of HMW lipids, the HMW acids/alkanes ratio and the acid/aldehyde ratio of lignin phenols) do not suggest extensive down-core mineralization, but there appears to be a trend to more degraded TerrOC with increasing distance from the coast. We infer that the degree of degradation of permafrost-derived TerrOC is a function of the time spent under oxic conditions (oxygen exposure time, OET). Specifically, one possible explanation for these patterns could be protracted OETs during cross-shelf transport compared to rather short in situ OETs after burial. To test this hypothesis we estimate lateral transport times using compound-specific radiocarbon analysis for terrestrial OC biomarkers (HMW fatty acids) and compare these with in situ OETs calculated from measured oxygen penetration depths and 210Pb-derived sedimentation rates.

Subsurface Environment Sampler for Improved In Situ Characterization of Subsurface Microbial Communities

NASA Astrophysics Data System (ADS)

Barnhart, E. P.; Ruppert, L. F.; Orem, W. H.; McIntosh, J. C.; Cunningham, A. B.; Fields, M. W.; Hiebert, R.; Hyatt, R.

2016-12-01

There is an increasing threat that deep aquifers, an important drinking water resource, may be contaminated by the extraction and transport of fossil fuels. This threat increases the need for improved groundwater monitoring and the ability to predict the extent to which microbial activity may remediate such contamination. The characterization of subsurface microbial communities could provide an ideal biomonitoring tool for the assessment of subsurface contamination due to prokaryotes environmental ubiquity, rapidity of response to environmental perturbation and the important role they play in hydrocarbon degradation and bioremediation. New DNA sequencing technologies provide the opportunity to cost-effectively identify the vast subsurface microbial ecosystem, but use of this new technology is restricted due to issues with sampling. Prior subsurface microbiology studies have relied on core samples that are expensive to obtain hard to collect aseptically and/or ground water samples that do not reflect in situ microbial densities or activities. The development of down-well incubation of sterile sediment with a Diffusive Microbial Sampler (DMS) has emerged as an alternative method to sample subsurface microbial communities that minimizes cost and contamination issues associated with traditional methods. We have designed a Subsurface Environment Sampler with a DMS module that could enable the anaerobic transport of the in situ microbial community from the field for laboratory bioremediation studies. This sampler could provide an inexpensive and standard method for subsurface microbial sampling which would make this tool useful for Federal, State, private and local agencies interested in monitoring contamination or the effectiveness of bioremediation activities in subsurface aquifers.

Ecohydrology of Deep Fractured Rocks at Homestake DUSEL

NASA Astrophysics Data System (ADS)

Kieft, T. L.; Boutt, D. F.; Murdoch, L. C.; Wang, H. F.

2009-12-01

The Deep Underground Science and Engineering Laboratory (DUSEL) at Homestake in SD will provide an unprecedented opportunity to study the terrestrial subsurface. Such a study could fundamentally change the way we view the origin and early evolution of life on Earth, the search for novel materials, and the generation of energy. Knowledge of subsurface life has come from only a few boreholes and deep mines. DUSEL will enable the first detailed study of a deep ecosystem in the context of the hydrology, geochemistry, and rock system state that sustain it. We are guided by the over-arching question: What controls the distribution and evolution of subsurface life? Our hypothesis is that these controls are dominated by processes related to geology, geochemistry, geomechanics, and hydrology. Themes of scaling and the development of facies, or zones of similar characteristics cut across all the processes. The ecohydrologic setting of DUSEL Homestake is characterized by a vast expanse of fractured metamorphic rock cut by 100s of km of tunnels and boreholes. Many km3 of the region have been highly affected by mining activities; adjacent regions are partially desaturated; and more distal regions are pristine and presumed to harbor indigenous microbial ecosystems. Simulations along with descriptions of the mine suggest division into zones, or ecohydrologic facies, where essential characteristics related to the requirements for life are expected to be similar. These ecohydrologic facies are a primary organizing principle for our investigation. The Deep EcoHydrology Experiment will consist of field studies supported by numerical simulations. The experimental activities include a particularly exciting opportunity to probe the lower limits of the biosphere using deep drilling technology deployed from the lowest reaches of the facility (2440 m below the surface). The use of the flooding/dewatering event as a tracer combined with hydrologic and mechanical stressors form a theme that cuts across many of the experimental activities. Five key experimental activities have been identified that will enable motivating hypotheses to be tested: 1) Initial Characterization, 2) Flow System, 3) Stress and Deformation, 4) Exploration, and 5) Cross-cutting activities. The International Continental Drilling Program has approved a preproposal for an ICDP ecohydrology project at DUSEL. The development of a long-term deep geosciences observatory at the Homestake DUSEL will revolutionize the field of deep sub-surface ecohydrology. The opportunities for young scientists and international participation in such a facility will be tremendous. Results from the work will have wide ranging implications as 20% of the current earth’s surface consists of a similar geologic setting. DUSEL will also facilitate experiential learning for K-12 through graduate school students working alongside world-class geoscientists.

Microbial stowaways: Addressing oil spill impacts and the artificial reef effect on deep-sea microbiomes

NASA Astrophysics Data System (ADS)

Hamdan, L. J.; Salerno, J. L.; Blackwell, C. A.; Little, B.; McGown, C.; Fitzgerald, L. A.; Damour, M.

2016-02-01

Shipwrecks enhance macro-biological diversity in the deep ocean, but, to date, studies have not explored the reef effect on deep-sea microbiological diversity. This is an important concept to address in a restoration framework, as microbial biogeochemical function impacts recruitment and adhesion of higher trophic levels on artificial reefs. In addition, microbial biofilms influence the preservation of shipwrecks through biologically mediated corrosion. Oil and gas-related activities have potential to disrupt the base of the reef trophic web; therefore, bacterial diversity and gene function at six shipwrecks (3 steel-hulled; 3 wood-hulled) in the northern Gulf of Mexico was investigated as part of the GOM-SCHEMA (Shipwreck Corrosion, Hydrocarbon Exposure, Microbiology, and Archaeology) project. Sites were selected based on proximity to the Deepwater Horizon spill's subsurface plume, depth, hull type, and existing archaeological data. Classification of taxa in sediments adjacent to and at distance from wrecks, in water, and on experimental steel coupons was used to evaluate how the presence of shipwrecks and spill contaminants in the deep biosphere influenced diversity. At all sites, and in all sample types, Proteobacteria were most abundant. Biodiversity was highest in surface sediments and in coupon biofilms adjacent to two steel-hulled wrecks in the study (Halo and Anona) and decreased with sediment depth and distance from the wrecks. Sequences associated with the iron oxidizing Mariprofundus genus were elevated at steel-hulled sites, indicating wreck-specific environmental selection. Despite evidence of the reef effect on microbiomes, bacterial composition was structured primarily by proximity to the spill and secondarily by hull material at all sites. This study provides the first evidence of an artificial reef effect on deep-sea microbial communities and suggests that biodiversity and function of primary colonizers of shipwrecks may be impacted by the spill.

Identifying glacial influences on sedimentation in tectonically-active, mass flow dominated arc basins with reference to the Neoproterozoic Gaskiers glaciation (c. 580 Ma) of the Avalonian-Cadomian Orogenic Belt

NASA Astrophysics Data System (ADS)

Carto, Shannon L.; Eyles, Nick

2012-06-01

Neoproterozoic 'Avalonian-Cadomian' volcanic arc basins once lay peripheral to Gondwana and are now found around the North Atlantic Ocean in New England, Atlantic Canada and northwestern Europe as 'peri-Gondwanan terranes.' Their thick (up to 9 km) marine fills are dominated by turbidites, debrites (diamictites and variably graded conglomerates), slumps and olistostromes recording the dominance of mass flow processes in arc basins oversupplied with volcaniclastic sediment. Several diamictite horizons in these basins were identified as glacial tillites more than one hundred years ago on the basis of poor textural sorting, and the lack of any understanding of mass flow processes. An association with thin-bedded turbidite facies, then interpreted as glaciolacustrine varvites, was seen as evidence for widespread glacial conditions which is still the basis today of a near global 'Gaskiers glaciation' at c. 580 Ma, despite classic sedimentological work which shows that the 'tillites' and 'varvites' of these basins are deep marine sediment gravity flow deposits. Only in two basins (Gaskiers Formation, Avalon Peninsula in Newfoundland, and the Konnarock Formation of Virginia) is a distal and regionally-restricted glacial influence on marine sedimentation identified from ice-rafted, striated dropstones in turbidites but terrestrial 'ice-contact' facies are absent. As revealed in this study, terrestrial glacial facies may not have survived frequent volcanic activity such as seen today on glaciated active plate margin volcanoes such as Mount Rainier in Washington USA, and Cotopaxi Volcano in Ecuador where primary glacial sediment is frequently reworked by lahars, pyroclastic flows, debris avalanches and outburst floods. The weight of evidence presented in this study indicates that ice covers during the Gaskiers glaciation were not widespread across the Avalonian-Cadomian back arc basins; the deep marine Grenada Basin (Caribbean Sea) filled with turbidites, debrites (lahars) and debris avalanches from the adjacent Lesser Antilles Arc is identified here as a modern analogue for these ancient basins.

Seismic evidence of glacial-age river incision into the Tahaa barrier reef, French Polynesia

USGS Publications Warehouse

Toomey, Michael; Woodruff, Jonathan D.; Ashton, Andrew D.; Perron, J. Taylor

2016-01-01

Rivers have long been recognized for their ability to shape reef-bound volcanic islands. On the time-scale of glacial–interglacial sea-level cycles, fluvial incision of exposed barrier reef lagoons may compete with constructional coral growth to shape the coastal geomorphology of ocean islands. However, overprinting of Pleistocene landscapes by Holocene erosion or sedimentation has largely obscured the role lowstand river incision may have played in developing the deep lagoons typical of modern barrier reefs. Here we use high-resolution seismic imagery and core stratigraphy to examine how erosion and/or deposition by upland drainage networks has shaped coastal morphology on Tahaa, a barrier reef-bound island located along the Society Islands hotspot chain in French Polynesia. At Tahaa, we find that many channels, incised into the lagoon floor during Pleistocene sea-level lowstands, are located near the mouths of upstream terrestrial drainages. Steeper antecedent topography appears to have enhanced lowstand fluvial erosion along Tahaa's southwestern coast and maintained a deep pass. During highstands, upland drainages appear to contribute little sediment to refilling accommodation space in the lagoon. Rather, the flushing of fine carbonate sediment out of incised fluvial channels by storms and currents appears to have limited lagoonal infilling and further reinforced development of deep barrier reef lagoons during periods of highstand submersion.

Age depth model construction of the upper section of ICDP Dead Sea Deep Drilling Project based on the high-resolution 14C dating

NASA Astrophysics Data System (ADS)

Kitagawa, H.; Nakamura, T.; Neugebauer, I.; Schwab, M. J.; Brauer, A.; Goldstein, S. L.; Stein, M.

2014-12-01

To reconstruct environmental, climatic and tectonic histories of the Levant, a deep drilling has been accomplished in the northern basin of the Dead Sea during the fall winter of 2010-2011 by the Dead Sea Deep Drilling Project (DSDDP) in the framework of the ICDP program. The sediment cores from site 5017-1 (water depth of ~300 m) recorded the paleoenvironmental and paleohydrological changes in the Dead Sea and the Levant during the last two glacial-interglacial cycles (Neugebauer et al., QSR in press). To provide precise timing of sedimentological - limnological events in the lake and its watershed, and more critically the relative timing of these events, radiocarbon dating of >70 well-preserved terrestrial plants and some carbonate deposits from the upper 150 m long section of the sediment core were performed. Based on the high-resolution radiocarbon dating, a statistical age-depth model was constructed with assumptions on the deposition condition and the radiocarbon age offset of carbonate samples. We discuss the practicality and the limitation of the age-depth model toward interpreting the high-resolution records of environmental, climatic and tectonic events recorded in the long sediment cores from site 5017-1.

Planetary science and exploration in the deep subsurface: results from the MINAR Program, Boulby Mine, UK

NASA Astrophysics Data System (ADS)

Payler, Samuel J.; Biddle, Jennifer F.; Coates, Andrew J.; Cousins, Claire R.; Cross, Rachel E.; Cullen, David C.; Downs, Michael T.; Direito, Susana O. L.; Edwards, Thomas; Gray, Amber L.; Genis, Jac; Gunn, Matthew; Hansford, Graeme M.; Harkness, Patrick; Holt, John; Josset, Jean-Luc; Li, Xuan; Lees, David S.; Lim, Darlene S. S.; McHugh, Melissa; McLuckie, David; Meehan, Emma; Paling, Sean M.; Souchon, Audrey; Yeoman, Louise; Cockell, Charles S.

2017-04-01

The subsurface exploration of other planetary bodies can be used to unravel their geological history and assess their habitability. On Mars in particular, present-day habitable conditions may be restricted to the subsurface. Using a deep subsurface mine, we carried out a program of extraterrestrial analog research - MINe Analog Research (MINAR). MINAR aims to carry out the scientific study of the deep subsurface and test instrumentation designed for planetary surface exploration by investigating deep subsurface geology, whilst establishing the potential this technology has to be transferred into the mining industry. An integrated multi-instrument suite was used to investigate samples of representative evaporite minerals from a subsurface Permian evaporite sequence, in particular to assess mineral and elemental variations which provide small-scale regions of enhanced habitability. The instruments used were the Panoramic Camera emulator, Close-Up Imager, Raman spectrometer, Small Planetary Linear Impulse Tool, Ultrasonic drill and handheld X-ray diffraction (XRD). We present science results from the analog research and show that these instruments can be used to investigate in situ the geological context and mineralogical variations of a deep subsurface environment, and thus habitability, from millimetre to metre scales. We also show that these instruments are complementary. For example, the identification of primary evaporite minerals such as NaCl and KCl, which are difficult to detect by portable Raman spectrometers, can be accomplished with XRD. By contrast, Raman is highly effective at locating and detecting mineral inclusions in primary evaporite minerals. MINAR demonstrates the effective use of a deep subsurface environment for planetary instrument development, understanding the habitability of extreme deep subsurface environments on Earth and other planetary bodies, and advancing the use of space technology in economic mining.

Thermokarst lake dynamics and its influence on biogeochemical sediment characteristics: A case study from the discontinuous permafrost zone in Interior Alaska

NASA Astrophysics Data System (ADS)

Lenz, J.; Walter Anthony, K. M.; Maio, C. V.; Matuszewski, F.; Grosse, G.

2017-12-01

Under currently projected scenarios of climate warming, discontinuous warm permafrost in Interior Alaska is expected to experience widespread disappearance. Thermokarst ponds and lakes are evidence for rapid permafrost thaw and amplify deep thaw by talik development. During the thawing process, previously preserved organic matter is made available for decomposition and former permafrost carbon is potentially released as greenhouse gases carbon dioxide and methane. In the course of lake development and shoreline expansion, both, younger near-surface and older organic matter from slumping shores are potentially deposited in the lake basin. Lake internal bioproductivity is complementing carbon accumulation in lacustrine deposits and provides an additional source of young carbon. This study presents results of two intersecting, limnolithological transects of 5 sediment cores from Goldstream Lake, a typical small, boreal thermokarst lake in Interior Alaska. We here distinguish external terrestrial and internal aquatic carbon contributions to sediments based on sediment samples that were analyzed for the total organic carbon/total nitrogen ratio (C/N) as well as stable carbon isotopes. The littoral zone with actively eroding shorelines is characterized by methane seeps produced from anaerobic microbial decomposition; however, near-shore sediments have surprisingly low total organic carbon contents with a mean of 1.5 wt%; the low C/N ratio of 8.7 indicate a dominance of lacustrine plant material. Very similar results were found for sediments in the central basin, but here a clear shift to a terrestrial carbon signal (C/N of 22) with total organic carbon content of almost 30 wt% is presumably indicating the presence of a trash layer featuring largely terrestrial plants submerged during the initial lake phase. The talik sediments have carbon storage similar to the lake sediments but in contrast are not layered. Subarctic aquatic environments such as Goldstream Lake demonstrate a high aquatic productivity as well as a high biogeochemical turn-over over short periods of time. In addition, the ongoing decomposition of organic matter in talik sediments proves to be crucial to assess the contribution of thermokarst lakes to future climate change by mobilizing soil carbon previously frozen in permafrost.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stevens, S.E. Jr.; Chung, K.T.

Anaerobic bacteria were isolated from deep subsurface sediment samples taken at study sites in Idaho (INEL) and Washington (HR) by culturing on dilute and concentrated medium. Morphologically distinct colonies were purified, and their responses to 21 selected physiological tests were determined. Although the number of isolates was small (18 INEL, 27 HR) some general patterns could be determined. Most strains could utilize all the carbon sources, however the glycerol and melizitose utilization was positive for 50% or less of the HR isolates. Catalase activity (27.78% at INEL, 74.07% at HR) and tryptophan metabolism (11.12% at INEL, 40.74% at HR) weremore » significantly different between the two study sites. MPN and viable counts indicate that sediments near the water table yield the greatest numbers of anaerobes. Deeper sediments also appear to be more selective with the greatest number of viable counts on low-nutrient mediums. Likewise, only strictly obligate anaerobes were found in the deepest sediment samples. Selective media indicated the presence of methanogens, acetogens, and sulfate reducers at only the HR site.« less

Microbial methane formation in deep aquifers of a coal-bearing sedimentary basin, Germany

PubMed Central

Gründger, Friederike; Jiménez, Núria; Thielemann, Thomas; Straaten, Nontje; Lüders, Tillmann; Richnow, Hans-Hermann; Krüger, Martin

2015-01-01

Coal-bearing sediments are major reservoirs of organic matter potentially available for methanogenic subsurface microbial communities. In this study the specific microbial community inside lignite-bearing sedimentary basin in Germany and its contribution to methanogenic hydrocarbon degradation processes was investigated. The stable isotope signature of methane measured in groundwater and coal-rich sediment samples indicated methanogenic activity. Analysis of 16S rRNA gene sequences showed the presence of methanogenic Archaea, predominantly belonging to the orders Methanosarcinales and Methanomicrobiales, capable of acetoclastic or hydrogenotrophic methanogenesis. Furthermore, we identified fermenting, sulfate-, nitrate-, and metal-reducing, or acetogenic Bacteria clustering within the phyla Proteobacteria, complemented by members of the classes Actinobacteria, and Clostridia. The indigenous microbial communities found in the groundwater as well as in the coal-rich sediments are able to degrade coal-derived organic components and to produce methane as the final product. Lignite-bearing sediments may be an important nutrient and energy source influencing larger compartments via groundwater transport. PMID:25852663

The diagenetic fate of taraxer-14-ene and oleanene isomers

NASA Astrophysics Data System (ADS)

ten Haven, H. L.; Rullkötter, J.

1988-10-01

The extractable organic matter in Holocene to early Miocene deep-sea sediments from Site 645 (ODP Leg 105) in Baffin Bay contains almost exclusively biological markers of terrigenous origin. Pentacyclic triterpenoids of the α-(ursene) and β-amyrin (oleanene) type often occur as the most abundant compounds in the aliphatic hydrocarbon, ketone and alcohol fractions of the sediment extract. A specific diagenetic reaction involves the conversion of taraxer-14-ene into olean-12-ene in the upper 700 metres of the sedimentary sequence. The taraxerene-to-oleanene conversion is complete before the onset of isomerisation of diasterenes at C-20. In the sediment as well as in laboratory simulation experiments, olean-12-ene further isomerises to olean-13(18)-ene and olean-18-ene, the latter of which may be the direct precursor of 18β(H)- and 18α(H)-oleanane found in sediments containing more mature organic matter and in crude oils. The subsurface interconversion of these triterpenoid skeletons indicate that oleanane does not necessarily start life as an oleanoid.

Shelfal sediment transport by undercurrents forces turbidity current activity during high sea level, Chile continental margin

NASA Astrophysics Data System (ADS)

Bernhardt, Anne; Hebbeln, Dierk; Regenberg, Marcus; Lückge, Andreas; Strecker, Manfred. R.

2016-04-01

Understanding the links between terrigenous sediment supply and marine transport and depositional processes along tectonically active margins is essential to decipher turbidite successions as potential archives of climatic and seismic forcings and to comprehend timing and quantity of marine clastic deposition. Sequence stratigraphic models predict coarse-grained terrigenous sediment delivery to deep-marine sites mainly during sea-level fall and lowstand. Marine clastic deposition during periods of transgression and highstand has been attributed to the continued geomorphic connectivity between terrestrial sediment sources and marine sinks (e.g., rivers connected to submarine canyons) often facilitated by narrow shelves, high sediment supply causing delta migration to the shelf edge, and/or abrupt increases in sediment supply due to climatic variability or catastrophic events. To decipher the controls on Holocene highstand turbidite deposition, we analyzed twelve sediment cores of spatially disparate, coeval Holocene turbidite systems along the Chile margin (29-40°S) with changing climatic and geomorphic characteristics but uniform changes of sea level. Intraslope basins in north-central Chile (29-33°S) offshore a narrow to absent shelf record a shut-off of turbidite activity during the Holocene. In contrast, core sites in south-central Chile (36-40°S) offshore a wide continental shelf have repeatedly experienced turbidite deposition during sea-level highstand conditions, even though most of the depocenters are not connected via canyons to sediment sources. The interplay of stable high sediment supply related to strong onshore precipitation in combination with a wide shelf, over which undercurrents move sediment towards the shelf edge, appears to control Holocene turbidite sedimentation and sediment export to the deep sea.

The metal oxide fraction of pelagic sediment in the equatorial North Pacific Ocean: A source of metals in ferromanganese nodules

USGS Publications Warehouse

Piper, D.Z.

1988-01-01

Pelagic sediment recovered at DOMES Site A in the equatorial North Pacific (151??W, 9?? 15???N) consists of a surface homogeneous layer, approximately 10 cm thick, overlying a strongly mottled layer that is lighter in color. The radiolarian composition of both units is Quaternary. In areas where this sediment was only a few centimeters thick, the underlying sediment was early Tertiary. Clay mineralogy and major oxide composition of the two Quaternary sediments are uniform. Their similarity to continental shale suggests that the sediment has a terrigenous source. Clay mineralogy and major oxide composition of the Tertiary sediment also are uniform, although they differ markedly from the Quarternary sediment. In contrast to the major oxides, concentrations of Mn, Co, Cu, and Ni soluble in hydroxylamine hydrochlorideacetic acid are strongly different in the surface and subsurface Quaternary sediment. Mn and Ni exhibit pronounced depletions in the subsurface sediment, Ni slightly more than Mn. Cu is also depleted in the subsurface sediment, but less than Mn. It is also depleted in the subsurface Tertiary sediment, whereas the Mn concentration remains high. Concentration of Co relative to Mn increases into the subsurface Quaternary sediment to a constant Co:Mn ratio of 3 ?? 10-2. The trivalent REE (the REE exclusive of Ce) and Fe exhibit little down-core variation. Distribution of elements in these sediments is closely related to their concentration in associated surface ferromanganese nodules. The nodules are of two distinct types: those from the area where the Quaternary sediment is relatively thick have ??-MnO2 as the dominant manganese mineral. The ratios of Ni:Mn, Cu:Mn, and Fe:Mn in these nodules approximate the corresponding ratios of the soluble fraction of surface sediment. Todorokite is the dominant mineral of nodules recovered from areas where the Quaternary sediment is thin. Relatively high Cu/Mn, Ni/Mn, and low Fe/Mn ratios of these nodules mirror differences between the soluble fraction of surface and subsurface Quaternary sediment. These compositional trends of sediment and nodules at DOMES Site A reflect a diagenetic origin for the todorokite nodules and a predominantly hydrogenous origin for the ??-MnO2 nodules. ?? 1988.

On the possibility of galactic cosmic ray-induced radiolysis-powered life in subsurface environments in the Universe.

PubMed

Atri, Dimitra

2016-10-01

Photosynthesis is a mechanism developed by terrestrial life to utilize the energy from photons of solar origin for biological use. Subsurface regions are isolated from the photosphere, and consequently are incapable of utilizing this energy. This opens up the opportunity for life to evolve alternative mechanisms for harvesting available energy. Bacterium Candidatus Desulforudis audaxviator, found 2.8 km deep in a South African mine, harvests energy from radiolysis, induced by particles emitted from radioactive U, Th and K present in surrounding rock. Another radiation source in the subsurface environments is secondary particles generated by galactic cosmic rays (GCRs). Using Monte Carlo simulations, it is shown that it is a steady source of energy comparable to that produced by radioactive substances, and the possibility of a slow metabolizing life flourishing on it cannot be ruled out. Two mechanisms are proposed through which GCR-induced secondary particles can be utilized for biological use in subsurface environments: (i) GCRs injecting energy in the environment through particle-induced radiolysis and (ii) organic synthesis from GCR secondaries interacting with the medium. Laboratory experiments to test these hypotheses are also proposed. Implications of these mechanisms on finding life in the Solar System and elsewhere in the Universe are discussed. © 2016 The Author(s).

On the possibility of galactic cosmic ray-induced radiolysis-powered life in subsurface environments in the Universe

PubMed Central

2016-01-01

Photosynthesis is a mechanism developed by terrestrial life to utilize the energy from photons of solar origin for biological use. Subsurface regions are isolated from the photosphere, and consequently are incapable of utilizing this energy. This opens up the opportunity for life to evolve alternative mechanisms for harvesting available energy. Bacterium Candidatus Desulforudis audaxviator, found 2.8 km deep in a South African mine, harvests energy from radiolysis, induced by particles emitted from radioactive U, Th and K present in surrounding rock. Another radiation source in the subsurface environments is secondary particles generated by galactic cosmic rays (GCRs). Using Monte Carlo simulations, it is shown that it is a steady source of energy comparable to that produced by radioactive substances, and the possibility of a slow metabolizing life flourishing on it cannot be ruled out. Two mechanisms are proposed through which GCR-induced secondary particles can be utilized for biological use in subsurface environments: (i) GCRs injecting energy in the environment through particle-induced radiolysis and (ii) organic synthesis from GCR secondaries interacting with the medium. Laboratory experiments to test these hypotheses are also proposed. Implications of these mechanisms on finding life in the Solar System and elsewhere in the Universe are discussed. PMID:27707907

Biolog(TM) ID as compared to 16S ribosomal RNA ID for environmental isolates from the deep subsurface

DOE Office of Scientific and Technical Information (OSTI.GOV)

McKinsey, P.C.

2000-05-05

The U.S. Dept of Energy (DOE) Subsurface Microbial Culture Collection (SMCC) contains nearly 10,000 strains of microorganisms isolated from terrestrial subsurface environments. Many of the aerobic, gram-negative, chemoheterotrophs isolated from the DOE Savannah River Site (SRS) have previously been identified by phylogenetic analysis of 16S ribosomal RNA (rRNA) gene nucleotide sequences. These SMCC isolates are currently being examined using Biolog GN Microplates and the Biolog Microstation System in order to gain knowledge of their metabolic capabilities and to compare Biolog IDs with 16S IDs. To accommodate the particular needs of these subsurface isolates, which are often incapable of growing undermore » high-nutrient conditions, Biolog's recommendations for inoculating isolates into Biolog GN Microplates have been altered. The isolates are grown on low nutrient media, sodium thioglycolate (3mM) is added to the culture media to inhibit capsule formation, and a low density of bacteria is inoculated into the microplate. Using these altered inoculation criteria, 60 percent of these SMCC isolates have a Biolog genus ID that matches the 16S rRNA ID. These results indicate that the Biolog System can be a good means of identifying unusual environmental isolates, even when recommended inoculation procedures are altered to accommodate particular isolate needs.« less

Denitrifying Bacteria from the Genus Rhodanobacter Dominate Bacterial Communities in the Highly Contaminated Subsurface of a Nuclear Legacy Waste Site

PubMed Central

Green, Stefan J.; Prakash, Om; Jasrotia, Puja; Overholt, Will A.; Cardenas, Erick; Hubbard, Daniela; Tiedje, James M.; Watson, David B.; Schadt, Christopher W.; Brooks, Scott C.

2012-01-01

The effect of long-term mixed-waste contamination, particularly uranium and nitrate, on the microbial community in the terrestrial subsurface was investigated at the field scale at the Oak Ridge Integrated Field Research Challenge (ORIFRC) site in Oak Ridge, TN. The abundance, community composition, and distribution of groundwater microorganisms were examined across the site during two seasonal sampling events. At representative locations, subsurface sediment was also examined from two boreholes, one sampled from the most heavily contaminated area of the site and another from an area with low contamination. A suite of DNA- and RNA-based molecular tools were employed for community characterization, including quantitative PCR of rRNA and nitrite reductase genes, community composition fingerprinting analysis, and high-throughput pyrotag sequencing of rRNA genes. The results demonstrate that pH is a major driver of the subsurface microbial community structure and that denitrifying bacteria from the genus Rhodanobacter (class Gammaproteobacteria) dominate at low pH. The relative abundance of bacteria from this genus was positively correlated with lower-pH conditions, and these bacteria were abundant and active in the most highly contaminated areas. Other factors, such as the concentration of nitrogen species, oxygen level, and sampling season, did not appear to strongly influence the distribution of Rhodanobacter bacteria. The results indicate that these organisms are acid-tolerant denitrifiers, well suited to the acidic, nitrate-rich subsurface conditions, and pH is confirmed as a dominant driver of bacterial community structure in this contaminated subsurface environment. PMID:22179233

Deposition and Burial Efficiency of Terrestrial Organic Carbon Exported from Small Mountainous Rivers to the Continental Margin, Southwest of Taiwan

NASA Astrophysics Data System (ADS)

Hsu, F.; Lin, S.; Wang, C.; Huh, C.

2007-12-01

Terrestrial organic carbon exported from small mountainous river to the continental margin may play an important role in global carbon cycle and it?|s biogeochemical process. A huge amount of suspended materials from small rivers in southwestern Taiwan (104 million tons per year) could serve as major carbon source to the adjacent ocean. However, little is know concerning fate of this terrigenous organic carbon. The purpose of this study is to calculate flux of terrigenous organic carbon deposited in the continental margin, offshore southwestern Taiwan through investigating spatial variation of organic carbon content, organic carbon isotopic compositions, organic carbon deposition rate and burial efficiency. Results show that organic carbon compositions in sediment are strongly influenced by terrestrial material exported from small rivers in the region, Kaoping River, Tseng-wen River and Er-jan Rver. In addition, a major part of the terrestrial materials exported from the Kaoping River may bypass shelf region and transport directly into the deep sea (South China Sea) through the Kaoping Canyon. Organic carbon isotopic compositions with lighter carbon isotopic values are found near the Kaoping River and Tseng-wen River mouth and rapidly change from heavier to lighter values through shelf to slope. Patches of lighter organic carbon isotopic compositions with high organic carbon content are also found in areas west of Kaoping River mouth, near the Kaoshiung city. Furthermore, terrigenous organic carbons with lighter isotopic values are found in the Kaoping canyon. A total of 0.028 Mt/yr of terrestrial organic carbon was found in the study area, which represented only about 10 percent of all terrestrial organic carbon deposited in the study area. Majority (~90 percent) of the organic carbon exported from the Kaoping River maybe directly transported into the deep sea (South China Sea) and become a major source of organic carbon in the deep sea.

Complete genome sequence of Anaeromyxobacter sp. Fw109-5, an Anaerobic, Metal-Reducing Bacterium Isolated from a Contaminated Subsurface Environment

DOE PAGES

Hwang, C.; Copeland, A.; Lucas, Susan; ...

2015-01-22

We report the genome sequence of Anaeromyxobacter sp. Fw109-5, isolated from nitrate- and uranium-contaminated subsurface sediment of the Oak Ridge Integrated Field-Scale Subsurface Research Challenge (IFC) site, Oak Ridge Reservation, TN. The bacterium’s genome sequence will elucidate its physiological potential in subsurface sediments undergoing in situ uranium bioremediation and natural attenuation.

Snake River Plain Geothermal Play Fairway Analysis - Phase 1 KMZ files

DOE Data Explorer

John Shervais

2015-10-10

This dataset contain raw data files in kmz files (Google Earth georeference format). These files include volcanic vent locations and age, the distribution of fine-grained lacustrine sediments (which act as both a seal and an insulating layer for hydrothermal fluids), and post-Miocene faults compiled from the Idaho Geological Survey, the USGS Quaternary Fault database, and unpublished mapping. It also contains the Composite Common Risk Segment Map created during Phase 1 studies, as well as a file with locations of select deep wells used to interrogate the subsurface.

The Discovery of Deep Oil Plumes at the Deepwater Horizon Oil Spill Site (Invited)

NASA Astrophysics Data System (ADS)

Diercks, A. R.; Asper, V. L.; Highsmith, R. C.; Woolsey, M.; Lohrenz, S. E.; McLetchie, K.; Gossett, A.; Lowe, M., III; Joung, D.; McKay, L.

2010-12-01

In May 2010, the National Institute for Undersea Science and Technology (NIUST), a partnership of the University of Mississippi, the University of Southern Mississippi and NOAA, had a 17-day research cruise aboard the UNOLS vessel R/V Pelican scheduled. Two weeks before departure, the Deepwater Horizon oil platform burned and sank, resulting in an uncontrolled oil spill at a depth of ~1500 m at Mississippi Canyon Block 252. The initial mission plan to do AUV surveys of wrecks and hydrate outcrops in the northern Gulf of Mexico, some of them very close to the site of the accident, was abandoned in favor of responding to the still uncontrolled oil spill. The primary goals of the redefined cruise were to acquire baseline and early impact data for seafloor sediments and subsurface distribution of oil and gas hydrates as close as possible in time and space to the origin of the oil spill. Investigating an oil spill nearly a mile deep in the ocean presents special benthic sampling and subsurface oil detection challenges. NIUST’s AUV’s were unloaded from the ship and a large main winch installed to allow operation of a full ocean depth box corer for collecting sediment samples in water depths up to 2000 m. During the first five-day leg of the cruise, a total of 28 box cores were collected. The Pelican returned to port (Cocodrie, LA) to drop off sediment and water samples for immediate analyses, and to take on more sampling gear and supplies for the second leg of the cruise, including an Acrobat, a CDOM fluorometer, a Video Ray ROV, and a CO2 sensor in addition to the already installed CTD Rosette with O2 sensor and beam transmissometer. During Leg 2, CTD stations were plotted to cover the area surrounding the wreck site and at various water depths to map the subsurface water column structure and chemistry as baseline values for future investigations and especially to look for submerged oil and/or gas hydrates. Early in the water column sampling, a subsurface feature was discovered at 1200 to 1400 m depth. This layer was detected by three independent sensors, CDOM (colored dissolved organic matter) fluorometer, beam transmissometer, and dissolved oxygen sensor. All three instruments responded in unison with greater fluorescence and beam attenuation and decreased O2 concentration. These signals were first observed at a station 5 miles from the accident site. Second and third station measurements at 2.5 miles, and at 1.25 miles from the spill site, showed the same signal but with significantly greater magnitude. Following this discovery, the sampling plan for the remaining days of the cruise was changed to map the newly discovered feature. This paper will discuss our data acquired during this cruise aboard the RV Pelican and its original discovery of the deep oil plumes from the Deepwater Horizon well.

Geochemical Impacts of Leaking CO2 from Subsurface Storage Reservoirs on the Fate of Metal Contaminants in an Overlaying Groundwater Aquifer

NASA Astrophysics Data System (ADS)

Shao, H.; Qafoku, N. P.; Lawter, A.; Bowden, M. E.; Brown, C. F.

2014-12-01

The leakage of CO2 and the concomitant upward transport of brine solutions and contaminants from deep storage reservoirs to overlaying groundwater aquifers is considered one of the major risks associated with geologic carbon sequestration (GCS). A systematic understanding of how such leakage would impact the geochemistry of potable aquifers is crucial to the maintenance of environmental quality and the widespread acceptance of GCS. A series of batch and column experiments studies were conducted to understand the fate (mobilization and immobilization) of trace metals, such as Cd and As in the groundwater aquifer after the intrusion of CO2 gas and CO2-saturated fluids containing leached metals from deep subsurface storage reservoirs. Sediments from the High Plains aquifer in Kansas, United States, were used in this investigation, which is part of the National Risk Assessment Partnership Program sponsored by the US DOE. This aquifer was selected to be representative of consolidated sand and gravel/sandstone aquifers overlying potential CO2 sequestration repositories within the continental US. The experiments were conducted at room temperature and atmospheric pressure. The results demonstrated that Cd and As that intrude into groundwater aquifers with the leaking CO2 at initial concentrations of 40 and 114 mg/L, respectively, will be adsorbed on the sediments, in spite of the acidic pH (between 5 and 6) due to CO2 dissolution in the groundwater. Cd concentrations were well below its MCL in both the aqueous solution of the batch study and the effluent of the column study, even for one of the sediment samples which had undetectable amount of carbonate minerals to buffer the pH. Arsenic concentrations were also significantly lower than that in the influent, suggesting that natural sediments have the capacity to mitigate the adverse effects of the CO2 leakage. However, the mitigation capacity of sediments is influenced by its geochemical properties. When there are anions such as phosphate in the sediment, competitive adsorption may occur and result in higher concentrations of toxic metals in the aqueous phase. Results from these investigations will provide useful information to support site selection, risk assessment, and public education efforts associated with geological CO2 storage and sequestration.

Flow and geochemistry of groundwater beneath a back-barrier lagoon: The subterranean estuary at Chincoteague Bay, Maryland, USA

USGS Publications Warehouse

Bratton, J.F.; Böhlke, J.K.; Krantz, D.E.; Tobias, C.R.

2009-01-01

To better understand large-scale interactions between fresh and saline groundwater beneath an Atlantic coastal estuary, an offshore drilling and sampling study was performed in a large barrier-bounded lagoon, Chincoteague Bay, Maryland, USA. Groundwater that was significantly fresher than overlying bay water was found in shallow plumes up to 8??m thick extending more than 1700??m offshore. Groundwater saltier than bay surface water was found locally beneath the lagoon and the barrier island, indicating recharge by saline water concentrated by evaporation prior to infiltration. Steep salinity and nutrient gradients occur within a few meters of the sediment surface in most locations studied, with buried peats and estuarine muds acting as confining units. Groundwater ages were generally more than 50??years in both fresh and brackish waters as deep as 23??m below the bay bottom. Water chemistry and isotopic data indicate that freshened plumes beneath the estuary are mixtures of water originally recharged on land and varying amounts of estuarine surface water that circulated through the bay floor, possibly at some distance from the sampling location. Ammonium is the dominant fixed nitrogen species in saline groundwater beneath the estuary at the locations sampled. Isotopic and dissolved-gas data from one location indicate that denitrification within the subsurface flow system removed terrestrial nitrate from fresh groundwater prior to discharge along the western side of the estuary. Similar situations, with one or more shallow semi-confined flow systems where groundwater geochemistry is strongly influenced by circulation of surface estuary water through organic-rich sediments, may be common on the Atlantic margin and elsewhere.

Spatial variations of community structures and methane cycling across a transect of Lei-Gong-Hou mud volcanoes in eastern Taiwan.

PubMed

Wang, Pei-Ling; Chiu, Yi-Ping; Cheng, Ting-Wen; Chang, Yung-Hsin; Tu, Wei-Xain; Lin, Li-Hung

2014-01-01

This study analyzed cored sediments retrieved from sites distributed across a transect of the Lei-Gong-Hou mud volcanoes in eastern Taiwan to uncover the spatial distributions of biogeochemical processes and community assemblages involved in methane cycling. The profiles of methane concentration and carbon isotopic composition revealed various orders of the predominance of specific methane-related metabolisms along depth. At a site proximal to the bubbling pool, the methanogenic zone was sandwiched by the anaerobic methanotrophic zones. For two sites distributed toward the topographic depression, the methanogenic zone overlaid the anaerobic methanotrophic zone. The predominance of anaerobic methanotrophy at specific depth intervals is supported by the enhanced copy numbers of the ANME-2a 16S rRNA gene and coincides with high dissolved Fe/Mn concentrations and copy numbers of the Desulfuromonas/Pelobacter 16S rRNA gene. Assemblages of 16S rRNA and mcrA genes revealed that methanogenesis was mediated by Methanococcoides and Methanosarcina. pmoA genes and a few 16S rRNA genes related to aerobic methanotrophs were detected in limited numbers of subsurface samples. While dissolved Fe/Mn signifies the presence of anaerobic metabolisms near the surface, the correlations between geochemical characteristics and gene abundances, and the absence of aerobic methanotrophs in top sediments suggest that anaerobic methanotrophy is potentially dependent on iron/manganese reduction and dominates over aerobic methanotrophy for the removal of methane produced in situ or from a deep source. Near-surface methanogenesis contributes to the methane emissions from mud platform. The alternating arrangements of methanogenic and methanotrophic zones at different sites suggest that the interactions between mud deposition, evaporation, oxidation and fluid transport modulate the assemblages of microbial communities and methane cycling in different compartments of terrestrial mud volcanoes.

Cold-seep-like macrofaunal communities in organic- and sulfide-rich sediments of the Congo deep-sea fan

NASA Astrophysics Data System (ADS)

Olu, K.; Decker, C.; Pastor, L.; Caprais, J.-C.; Khripounoff, A.; Morineaux, M.; Ain Baziz, M.; Menot, L.; Rabouille, C.

2017-08-01

Methane-rich fluids arising from organic matter diagenesis in deep sediment layers sustain chemosynthesis-based ecosystems along continental margins. This type of cold seep develops on pockmarks along the Congo margin, where fluids migrate from deep-buried paleo-channels of the Congo River, acting as reservoirs. Similar ecosystems based on shallow methane production occur in the terminal lobes of the present-day Congo deep-sea fan, which is supplied by huge quantities of primarily terrestrial material carried by turbiditic currents along the 800 km channel, and deposited at depths of up to nearly 5000 m. In this paper, we explore the effect of this carbon enrichment of deep-sea sediments on benthic macrofauna, along the prograding lobes fed by the current active channel, and on older lobes receiving less turbiditic inputs. Macrofaunal communities were sampled using either USNEL cores on the channel levees, or ROV blade cores in the chemosynthesis-based habitats patchily distributed in the active lobe complex. The exceptionally high organic content of the surface sediment in the active lobe complex was correlated with unusual densities of macrofauna for this depth, enhanced by a factor 7-8, compared with those of the older, abandoned lobe, whose sediment carbon content is still higher than in Angola Basin at same depth. Macrofaunal communities, dominated by cossurid polychaetes and tanaids were also more closely related to those colonizing low-flow cold seeps than those of typical deep-sea sediment. In reduced sediments, microbial mats and vesicomyid bivalve beds displayed macrofaunal community patterns that were similar to their cold-seep counterparts, with high densities, low diversity and dominance of sulfide-tolerant polychaetes and gastropods in the most sulfidic habitats. In addition, diversity was higher in vesicomyid bivalve beds, which appeared to bio-irrigate the upper sediment layers. High beta-diversity is underscored by the variability of geochemical gradients in vesicomyid assemblages, and by the vesicomyid population characteristics that vary in density, size and composition. By modifying the sediment geochemistry differently according to their morphology and physiology, the different vesicomyid species play an important role structuring macrofauna composition and vertical distribution. Dynamics of turbiditic deposits at a longer temporal scale (thousands of years) and their spatial distribution in the lobe area also resulted in high heterogeneity of the "cold-seep-like communities". Dynamics of chemosynthetic habitats and associated macrofauna in the active lobe area resembled those previously observed at the Regab pockmark along the Congo margin and rapid succession is expected to cope with high physical disturbance by frequent turbiditic events and huge sedimentation rates. Finally, we propose a model of the temporal evolution of these peculiar habitats and communities on longer timescales in response to changes in distributary channels within the lobe complex.

Origin and fate of sedimentary organic matter in the northern Bay of Bengal during the last 18 ka

NASA Astrophysics Data System (ADS)

Contreras-Rosales, L. A.; Schefuß, E.; Meyer, V.; Palamenghi, L.; Lückge, A.; Jennerjahn, T. C.

2016-11-01

The Northern Bay of Bengal (NBoB) is a globally important region for deep-sea organic matter (OM) deposition due to massive fluvial discharge from the Ganges-Brahmaputra-Meghna (G-B-M) rivers and moderate to high surface productivity. Previous studies have focused on carbon burial in turbiditic sediments of the Bengal Fan. However, little is known about the storage of carbon in pelagic and hemipelagic sediments of the Bay of Bengal over millennial time scales. This study presents a comprehensive history of OM origin and fate as well as a quantification of carbon sediment storage in the Eastern Bengal Slope (EBS) during the last 18 ka. Bulk organic proxies (TOC, TIC, TN, δ13CTOC, δ15NTN) and content and composition of total hydrolysable amino acids (THAA) in a sediment core (SO188-342KL) from the EBS were analyzed. Three periods of high OM accumulation were identified: the Late Glacial (LG), the Bölling/Alleröd (B/A), and the Early Holocene Climatic Optimum (EHCO). Lower eustatic sea level before 15 ka BP allowed a closer connection between the EBS and the fluvial debouch, favoring high terrestrial OM input to the core site. This connection was progressively lost between 15 and 7 ka BP as sea level rose to its present height and terrestrial OM input decreased considerably. Export and preservation of marine OM was stimulated during periods of summer monsoon intensification (B/A and EHCO) as a consequence of higher surface productivity enhanced by cyclonic-eddy nutrient pumping and fluvial nutrient delivery into the photic zone. Changes in the THAA composition indicate that the marine plankton community structure shifted from calcareous-dominated before 13 ka BP to siliceous-dominated afterwards. They also indicate that the relative proportion of marine versus terrestrial OM deposited at site 342KL was primarily driven by relative sea level and enlarged during the Holocene. The ballasting effect of lithogenic particles during periods of high coastal proximity and/or enhanced fluvial discharge promoted the export and preservation of OM. The high organic carbon accumulation rates in the EBS during the LG (18-17 ka BP) were 5-fold higher than at present and comparable to those of glacial upwelling areas. Despite the differences in sediment and OM transport and storage among the Western and Eastern sectors of the NBoB, this region remains important for global carbon sequestration during sea level low-stands. In addition, the summer monsoon was a key promotor of terrestrial and marine OM export to the deep-ocean, highlighting its relevance as regulator of the global carbon budget.

Río Tinto: A Geochemical and Mineralogical Terrestrial Analogue of Mars

PubMed Central

Amils, Ricardo; Fernández-Remolar, David

2014-01-01

The geomicrobiological characterization of the water column and sediments of Río Tinto (Huelva, Southwestern Spain) have proven the importance of the iron and the sulfur cycles, not only in generating the extreme conditions of the habitat (low pH, high concentration of toxic heavy metals), but also in maintaining the high level of microbial diversity detected in the basin. It has been proven that the extreme acidic conditions of Río Tinto basin are not the product of 5000 years of mining activity in the area, but the consequence of an active underground bioreactor that obtains its energy from the massive sulfidic minerals existing in the Iberian Pyrite Belt. Two drilling projects, MARTE (Mars Astrobiology Research and Technology Experiment) (2003–2006) and IPBSL (Iberian Pyrite Belt Subsurface Life Detection) (2011–2015), were developed and carried out to provide evidence of subsurface microbial activity and the potential resources that support these activities. The reduced substrates and the oxidants that drive the system appear to come from the rock matrix. These resources need only groundwater to launch diverse microbial metabolisms. The similarities between the vast sulfate and iron oxide deposits on Mars and the main sulfide bioleaching products found in the Tinto basin have given Río Tinto the status of a geochemical and mineralogical Mars terrestrial analogue. PMID:25370383

Sediment storage quantification and postglacial evolution of an inner-alpine sedimentary basin (Gradenmoos, Schober Mountains, Austria)

NASA Astrophysics Data System (ADS)

Götz, J.; Buckel, J.; Otto, J. C.; Schrott, L.

2012-04-01

Knickpoints in longitudinal valley profiles of alpine headwater catchments can be frequently assigned to the lithological and tectonical setting, to damming effects through large (rockfall) deposits, or to the impact of Pleistocene glaciations causing overdeepened basins. As a consequence various sedimentary sinks developed, which frequently interrupt sediment flux in alpine drainage basins. Today these locations may represent landscape archives documenting a sedimentary history of great value for the understanding of alpine landscape evolution. The glacially overdeepened Gradenmoos basin at 1920 m a.s.l. (an alpine lake mire with adjacent floodplain deposits and surrounding slope storage landforms; approx. 4.1 km2) is the most pronounced sink in the studied Gradenbach catchment (32.5 km2). The basin is completely filled up with sediments delivered by mainly fluvial processes, debris flows, and rock falls, it is assumed to be deglaciated since Egesen times and it is expected to archive a continuous stratigraphy of postglacial sedimentation. As the analysis of denudation-accumulation-systems is generally based on back-calculation of stored sediment volumes to a specific sediment delivering area, most reliable results will be consequently obtained (1) if sediment output of the system can be neglected for the investigated period of time, (2) if - due to spatial scale - sediment storage can be assessed quantitatively with a high level of accuracy, and (3) if the sediment contributing area can be clearly delimited. All three aspects are considered to be fulfilled to a high degree within the Gradenmoos basin. Sediment storage is quantified using geophysical methods, core drillings and GIS modelling whereas postglacial reconstruction is based on radiocarbon dating and palynological analyses. Subject to variable subsurface conditions, different geophysical methods were applied to detect bedrock depth. Electrical resistivity surveying (2D/3D) was used most extensively as it delivered detailed and realistic subsurface models with low residual errors in the fine grained and water saturated central and distal part of the basin. With a lower data density, ground penetrating radar and refraction seismic supplied bedrock depths underneath adjacent debris and talus slope deposits. Additionally extracted sediment cores (up to 22 m depth) yielded a detailed stratigraphic record of the basin comprising a basal till layer underneath lake sediments (sandy-silty, partly varved), a sandy matrix with several oxidised layers in the upper sections, and layers of peat towards the surface. As bedrock was reached several times, core drilling further enabled to calibrate resistivity models. On the base of geophysical derived bedrock points, the shape of the assumed bedrock basin was modelled using a thin-plate-spline interpolation. Sediment volumes were calculated by subtracting the bedrock model from a surface DEM derived from terrestrial laser scanning. Since sediment delivering areas can be clearly assigned to single storage landform volumes, denudation rates could be calculated in detail and related to sedimentation rates obtained by radiocarbon dating results. An integrated analysis of surface, subsurface and temporal information finally yielded a model of postglacial basin evolution which will be discussed in a paraglacial context. This presentation is supported by the EUROCORES programme TOPO-EUROPE of the European Science Foundation.

Dynamics of the transfer of terrestrial organic matter in the late Quaternary turbiditic system of the Ogooué River (Gabon)

NASA Astrophysics Data System (ADS)

Mignard, Salomé; Mulder, Thierry; Martinez, Philippe; Garlan, Thierry

2016-04-01

In many cases (Hedges et al., 1995, Xing et al., 2011) the supply of terrestrial organic matter (OM) in the oceanic environment is confined to the continental and upper slope of continental margins. However, some recent studies (Huc et al., 2001, Baudin et al., 2010, Biscara et al., 2011, Stetten et al., 2015) demonstrated that significant amounts of continental OM can be transported and deposited in deep sea sediments. This transfer is more efficient in turbiditic systems which are linked to important river deltas. In such systems, the terrigenous influx are important and the downslope sediment-laden currents can indeed transport and rapidly bury important quantities of TOM transferred from the river mouth and the shelf to the abyssal plain. The turbiditic system associated with the Ogooué River offshore Gabon has been selected to study more precisely the modalities of transfer of continental OM from the shelf to the deep offshore. The works focuses on the concentration of OM in both hemipelagites and turbidites as well as the different parameters influencing the spatial distribution and concentration. For this study 10 cores located along the system from the continental shelf to the distal lobes have been selected. The quantity of OM in the sediments as well as its origin (continental vs marine) have been measured using bulk geochemical analyses (% OC, δ13Corg). The stratigraphy of the cores was determined using a combination of planktonic foraminiferal assemblages, δ18O on benthic foraminifers and 14C dates on planktonic foraminifers, and calcium carbonate content calibrated with XRF measurements. The studied cores contain various amounts of organic carbon ranging from 0.7wt% to more than 9wt%. The highest contents are found in turbidite beds where woody detritus and well preserved fragmentary leaf debris are concentrated. In the hemipelagic facies, organic matter is composed of a mixture of marine and land derived organic matter associated with clay-size sediments. This organic sedimentation is highly sensitive to the variations of the sea level due to the alternation between glacial and interglacial times. Glacial periods are characterized by higher amounts of organic matter in hemipelagic deposits, with a higher contribution of continental material, and by the presence of frequent organic rich turbiditic beds. On the contrary, during interglacial periods very few turbiditic events are recorded and the OM in hemipelagic sediments is mainly of marine origin and in lesser quantity. When the sea-level is high, the Ogooué delta is disconnected from the canyon heads and the sediments delivered by the river are deposited on the shelf and mobilized by the strong South-North coastal drift currents. During low sea-level periods, the river discharges its sediments rich in terrestrial OM directly in the canyons heads bypassing the shelf. The low sea level also generates increased erosion of the shelf sediments containing globally high rate of reworked continental OM.

Characterization of a suspected terrestrial deep groundwater discharge area on the Canadian Precambrian Shield

NASA Astrophysics Data System (ADS)

Sheppard, Marsha I.; Thibault, D. H.; Milton, G. M.; Reid, J. A. K.; Smith, P. A.; Stevens, K.

1995-03-01

Underground storage and disposal of hazardous wastes require an understanding of groundwater flow and the ability to locate recharge and discharge. Usually, recharge and discharge occur at a transition zone where dispersion/advection, molecular diffusion and biogeochemical processes control the fate of a contaminants leaving an underground facility. Appropriate landscape modelling for risk assessment cannot proceed until this interface is well defined and groundwater discharge can be mapped. Although discharge locations have traditionally been thought of as aquatic, the presence of animal licks suggests the possibility of terrestrial discharge. We have characterized a suspected terrestrial discharge, a well-used deer lick, (1) physically, through surficial mapping, and vegetation and soil profile analyses; (2) geophysically, through magnetic and very low-frequency electromagnetic tilt-angle surveys; (3) hydrogeologically, through water-table elevation measurements; (4) geochemically, through overburden analyses for 238U, 226Ra, 210Pb, Na, tritium, Cl and 36{Cl}/{Cl} atom ratios, as well as pore-water and groundwater analyses for pH, electrical conductivity (EC) and major anions and cations; and (5) thermally, through overburden-rock interface temperatures. Halophytic plants and sedges contained more Na, Cl and 238U than averages reported in the literature. Lineament alignment, coincident with elevated groundwater EC, supported the presence and position of a subsurface fracture. Groundwater chemistry suggested that interfering runoff from a nearby ridge masked the chemical signatures expected of deep groundwater but attest to the weak and possibly ephemeral nature of this discharge. Interpretation of the geochemical data was supported by solute transport modelling. Good agreement between the predictions using an unsaturated soil model, a simple wetland compartment model and the observed profile implied that evapotranspiration, seasonal water-table fluctuations and flooding, and sorption of 238U due to anoxia deep in the overburden are major processes shaping the overburden solute profile. This evidence strongly supported the hypothesis that the site is a location where deep groundwater (groundwater from depths of 500-1000 m) discharges.

Organic geochemistry of sediments of the Deep Gulf of Mexico Basin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sassen, R.; Fang Jiasong

1990-05-01

Analysis of 716 core samples cored at DSDP (Deep Sea Drilling Project) Leg 96 in the Mississippi submarine fan and the Orca and Pigmy basins in the Louisiana continental slope using a Rock-Eval pyrolysis unit with a TOC (total organic carbon) module allows computations of hydrogen index (HI), total organic carbon, kerogen type, and oil generative capacity assessment. No samples are obviously oil prone. TOC content ranges from 0.12 to 2.29%, with an overall average of 9.82%. HI values are generally less than 150 mg HC/g TOC. T{sub max} (maximum temperature of S{sub 2}) values (average = 425{degree}C) show themore » sediments are thermally immature through-out the study area. Hydrocarbon generative potential of the sediments ranges from 492 to 1,107 ppm, with an average of 854 ppm. Higher PI (Production index) values, ranging from 0.12 to 0.32 and averaging 0.15, suggest the presence of hydrocarbon seepage. Because of organically lean, thermally immature, and gas-prone terrestrial kerogen, there is little reason to assume that the sediments of the Mississippi fan can provide oil source rock for the Gulf of Mexico Basin, or that sediments of anoxic basins in the Louisiana continental slope are analogs to past environments where source rocks for crude oil have been deposited.« less

Great differences in the critical erosion threshold between surface and subsurface sediments: A field investigation of an intertidal mudflat, Jiangsu, China

NASA Astrophysics Data System (ADS)

Shi, Benwei; Wang, Ya Ping; Wang, Li Hua; Li, Peng; Gao, Jianhua; Xing, Fei; Chen, Jing Dong

2018-06-01

Understanding of bottom sediment erodibility is necessary for the sustainable management and protection of coastlines, and is of great importance for numerical models of sediment dynamics and transport. To investigate the dependence of sediment erodibility on degree of consolidation, we measured turbidity, waves, tidal currents, intratidal bed-level changes, and sediment properties on an exposed macrotidal mudflat during a series of tidal cycles. We estimated the water content of surface sediments (in the uppermost 2 cm of sediment) and sub-surface sediments (at 2 cm below the sediment surface). Bed shear stress values due to currents (τc), waves (τw), and combined current-wave action (τcw) were calculated using a hydrodynamic model. In this study, we estimate the critical shear stress for erosion using two approaches and both of them give similar results. We found that the critical shear stress for erosion (τce) was 0.17-0.18 N/m2 in the uppermost 0-2 cm of sediment and 0.29 N/m2 in sub-surface sediment layers (depth, 2 cm), as determined by time series of τcw values and intratidal bed-level changes, and values of τce, obtained using the water content of bottom sediments, were 0.16 N/m2 in the uppermost 2 cm and 0.28 N/m2 in the sub-surface (depth, 2 cm) sediment. These results indicate that the value of τce for sub-surface sediments (depth, 2 cm) is much greater than that for the uppermost sediments (depth, 0-2 cm), and that the τce value is mainly related to the water content, which is determined by the extent of consolidation. Our results have implications for improving the predictive accuracy of models of sediment transport and morphological evolution, by introducing variable τce values for corresponding sediment layers, and can also provide a mechanistic understanding of bottom sediment erodibility at different sediment depths on intertidal mudflats, as related to differences in the consolidation time.

Ecological impacts of large-scale disposal of mining waste in the deep sea

PubMed Central

Hughes, David J.; Shimmield, Tracy M.; Black, Kenneth D.; Howe, John A.

2015-01-01

Deep-Sea Tailings Placement (DSTP) from terrestrial mines is one of several large-scale industrial activities now taking place in the deep sea. The scale and persistence of its impacts on seabed biota are unknown. We sampled around the Lihir and Misima island mines in Papua New Guinea to measure the impacts of ongoing DSTP and assess the state of benthic infaunal communities after its conclusion. At Lihir, where DSTP has operated continuously since 1996, abundance of sediment infauna was substantially reduced across the sampled depth range (800–2020 m), accompanied by changes in higher-taxon community structure, in comparison with unimpacted reference stations. At Misima, where DSTP took place for 15 years, ending in 2004, effects on community composition persisted 3.5 years after its conclusion. Active tailings deposition has severe impacts on deep-sea infaunal communities and these impacts are detectable at a coarse level of taxonomic resolution. PMID:25939397

Ecological impacts of large-scale disposal of mining waste in the deep sea.

PubMed

Hughes, David J; Shimmield, Tracy M; Black, Kenneth D; Howe, John A

2015-05-05

Deep-Sea Tailings Placement (DSTP) from terrestrial mines is one of several large-scale industrial activities now taking place in the deep sea. The scale and persistence of its impacts on seabed biota are unknown. We sampled around the Lihir and Misima island mines in Papua New Guinea to measure the impacts of ongoing DSTP and assess the state of benthic infaunal communities after its conclusion. At Lihir, where DSTP has operated continuously since 1996, abundance of sediment infauna was substantially reduced across the sampled depth range (800-2020 m), accompanied by changes in higher-taxon community structure, in comparison with unimpacted reference stations. At Misima, where DSTP took place for 15 years, ending in 2004, effects on community composition persisted 3.5 years after its conclusion. Active tailings deposition has severe impacts on deep-sea infaunal communities and these impacts are detectable at a coarse level of taxonomic resolution.

Distribution of surface deposits in the Gijón urban subsurface (NW Spain)

NASA Astrophysics Data System (ADS)

López-Fernández, Carlos; Pando, Luis; María Díaz-Díaz, Luis; Arias, Daniel; Flor-Blanco, Germán

2016-04-01

Gijón is the second most populous city (278.285 inhabitants in 2015) of the Spanish north coast. The urban subsurface is mostly formed (≈80%) by Quaternary sediments which exceeds 20 meters of thickness when cover the Jurassic carbonate basement (Gijón Formation). This work has allowed to know the spatial distribution of the different types of sediments in urban area. To do this, a GIS database was developed that contains data from more than 450 geotechnical reports. Information provided by fieldwork and the exploration of excavation works in progress throughout the city was also incorporated. Currently, the geodatabase developed comprises more than 1,400 site investigation points: boreholes, dynamic probing and trial pits. This has been supplemented with hundreds on-site and laboratory tests carried out on core samples of soils and rocks, performed following renowned testing standards. Quaternary formations, largely concealed below man-made fills, set up two main areas composed by granular and cohesive soils: the littoral zone at the northern urban perimeter and the continental zone at the southern sector. The first one, fluvial-marine deposits, consist of sandy sediments related to beach/dune systems and marsh deposits, with gravels, organogenic mud and layers of Holocene peat. The southern area is composed by residual clays -silt and coarse-grained soils to a lesser extent- linked to the dissolution of the Mesozoic substrate. Associated with these two types of deposits, two main aquifers can be differentiated. The thickness of the man-made deposits, fluvial-marine sediments and residual deposits was determined in this work. Thus, a 3-d model of Gijón subsurface at urban scale was obtained. A map of the Jurassic bedrock bedrock was also produced. Building construction works may be affected by the geotechnical behavior of the Quaternary deposits and the saturation of granular sediments., This is because the shallowness of the water table, the usual low bearing capacity and other issues such as clays consolidation or swelling phenomena. The use of concrete slabs, deep foundations and piled/anchored retaining walls is very common when projecting underground floors under these conditions.

Inorganic and organic geochemical fingerprinting of sediment sources and ocean circulation on a complex continental margin (São Paulo Bight, Brazil)

NASA Astrophysics Data System (ADS)

Michaelovitch de Mahiques, Michel; Jörg Hanebuth, Till Jens; Hanae Nagai, Renata; Caruso Bícego, Marcia; Lopes Figueira, Rubens Cesar; Mello Sousa, Silvia Helena; Burone, Leticia; Franco-Fraguas, Paula; Taniguchi, Satie; Barbosa Salaroli, Alexandre; Pereira Dias, Gilberto; Menezes Prates, Denise; Fernandes Freitas, Maria Eugenia

2017-03-01

In this study, we use inorganic (metal) and organic (bulk and molecular) markers in sediment samples of the south-eastern Brazilian margin to investigate the response of geochemical fingerprints to the complex hydrodynamic processes present in the area. Results indicate the potential of export of terrigenous siliciclastic and organic constituents to the upper slope, even in an area with limited fluvial supply.

Metal contents and especially the ln(Ti / Al) and ln(Fe / K) ratios make it possible to recognise the extension of shelf sediments toward the upper slope. Potassium, here expressed as ln(K / Sc) and ln(K / Al) ratios used as proxies of illite-kaolinite variations, proved to be an important parameter, especially because it allowed us to decipher the imprint of the northward flow of the Intermediate Western Boundary Current (IWBC) in comparison to the southward flows of the Brazil Current (BC) and Deep Western Boundary Current (DWBC). Using organic matter analyses, we were able to evaluate the extent of terrestrial contributions to the outer shelf and slope, even without the presence of significant fluvial input. In addition, molecular markers signify a slight increase in the input of C4-derived plants to the slope sediments, transported from distant areas by the main alongshore boundary currents, indicating that the terrestrial fraction of the organic matter deposited on the slope has a distinct origin when compared to shelf sediments.

Hydraulic fracturing offers view of microbial life in the deep terrestrial subsurface.

PubMed

Mouser, Paula J; Borton, Mikayla; Darrah, Thomas H; Hartsock, Angela; Wrighton, Kelly C

2016-11-01

Horizontal drilling and hydraulic fracturing are increasingly used for recovering energy resources in black shales across the globe. Although newly drilled wells are providing access to rocks and fluids from kilometer depths to study the deep biosphere, we have much to learn about microbial ecology of shales before and after 'fracking'. Recent studies provide a framework for considering how engineering activities alter this rock-hosted ecosystem. We first provide data on the geochemical environment and microbial habitability in pristine shales. Next, we summarize data showing the same pattern across fractured shales: diverse assemblages of microbes are introduced into the subsurface, eventually converging to a low diversity, halotolerant, bacterial and archaeal community. Data we synthesized show that the shale microbial community predictably shifts in response to temporal changes in geochemistry, favoring conservation of key microorganisms regardless of inputs, shale location or operators. We identified factors that constrain diversity in the shale and inhibit biodegradation at the surface, including salinity, biocides, substrates and redox. Continued research in this engineered ecosystem is required to assess additive biodegradability, quantify infrastructure biocorrosion, treat wastewaters that return to the surface and potentially enhance energy production through in situ methanogenesis. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Cooling and drying in northeast Africa across the Pliocene

NASA Astrophysics Data System (ADS)

Liddy, Hannah M.; Feakins, Sarah J.; Tierney, Jessica E.

2016-09-01

Terrestrial records suggest that Northeast Africa experienced drying during the Pliocene; however, these records are often incomplete in time and space, and questions about this shift in climate remain. Here, we use marine sediments from Deep Sea Drilling Project (DSDP) Site 231 in the Gulf of Aden to generate a multi-proxy organic geochemical record of northeast African climate spanning 5.3-2 Ma. This new record provides a regional perspective on climate and serves as context for the fossil record of early hominin evolution. We measured leaf wax carbon (δ13Cwax) and hydrogen (δDwax) isotopic composition and TEX86 (tetraether index of 86 carbons) to investigate past changes in vegetation, aridity, and ocean temperature, respectively. In the earliest Pliocene, we infer warm subsurface ocean temperatures from TEX86, semi-arid conditions on land and extensive C4 grasslands based on δDwax, δ13Cwax and previously published pollen. After 5 Ma, ocean temperatures gradually cooled, and at 4.3 Ma there was a transition to arid conditions on land based on δDwax and pollen. Grasslands yielded to a mid Pliocene landscape of dry shrublands. This drying appears to be an atmospheric response to cooling ocean temperatures, which may reflect changes in tropical ocean circulation, the intensification of Indian Monsoon winds or perhaps other changes associated with Pliocene cooling.

Microbes in deep marine sediments viewed through amplicon sequencing and metagenomics

NASA Astrophysics Data System (ADS)

Biddle, J.; Leon, Z. R.; Russell, J. A., III; Martino, A. J.

2016-12-01

Nearly twenty percent of microbial biomass on Earth can be found in the marine subsurface. The majority of this is concentrated on continental margins, which have been investigated by scientific drilling. On the Costa Rica Margin, Iberian Margin and Peru Margins, sediment samples have been investigated through DNA extraction followed by amplicon and metagenomic sequencing. Overall samples show a high degree of microbial diversity, including many lineages of newly defined groups. In this talk, metagenome assembled genomes of unusual lineages will be presented, including their relationships to shallower relatives. From Costa Rica, in particular, we have retrieved deep relatives of Lokiarchaeota and Thorarchaeota, as well as other deeply branching archaeal relatives. We discuss their genome similarities to both other archaea and eukaryotes. From the Iberian Margin, relatives of Atribacteria and Aerophobetes will be discussed. Finally, we will detail the knowledge lost or gained depending on whether samples are studied via amplicon sequencing or total metagenomics, as studies in other environments have shown that up to 15% of microbial diversity is ignored when samples are studied via amplicon sequencing alone.

Recycling an uplifted early foreland basin fill: An example from the Jaca basin (Southern Pyrenees, Spain)

NASA Astrophysics Data System (ADS)

Roigé, M.; Gómez-Gras, D.; Remacha, E.; Boya, S.; Viaplana-Muzas, M.; Teixell, A.

2017-10-01

In the northern Jaca basin (Southern Pyrenees), the replacement of deep-marine by terrestrial environments during the Eocene records a main drainage reorganization in the active Pyrenean pro-wedge, which leads to recycling of earlier foreland basin sediments. The onset of late Eocene-Oligocene terrestrial sedimentation is represented by four main alluvial fans: Santa Orosia, Canciás, Peña Oroel and San Juan de la Peña, which appear diachronously from east to west. These alluvial fans are the youngest preserved sediments deposited in the basin. We provide new data on sediment composition and sources for the late Eocene-Oligocene alluvial fans and precursor deltas of the Jaca basin. Sandstone petrography allows identification of the interplay of axially-fed sediments from the east with transversely-fed sediments from the north. Compositional data for the alluvial fans reflects a dominating proportion of recycled rock fragments derived from the erosion of a lower to middle Eocene flysch depocentre (the Hecho Group), located immediately to the north. In addition, pebble composition allows identification of a source in the North Pyrenean Zone that provided lithologies from the Cretaceous carbonate flysch, Jurassic dolostones and Triassic dolerites. Thus we infer this zone as part of the source area, located in the headwaters, which would have been unroofed from turbidite deposits during the late Eocene-Oligocene. These conclusions provide new insights on the response of drainage networks to uplift and topographic growth of the Pyrenees, where the water divide migrated southwards to its present day location.

Controlled Source Electromagnetic Monitoring of Hydraulic Fracturing: Wellbore and Fluid Effects

NASA Astrophysics Data System (ADS)

Couchman, M. J.; Everett, M. E.

2017-12-01

As unconventional resources become increasingly important, we must tackle the issue of real-time monitoring of the efficiency of unconventional hydrocarbon extraction. Controlled Source Electromagnetics (CSEM) have been used primarily as a marine-based technique to monitor conventional oil bearing reservoirs with a strong resurgence the new millennium. Many of these studies revolving around detecting a thin resistive layer such as a reservoir at 1m - 3km depth. In these cases, the presence of the resistive layer is characterized by a jump in electric field amplitude recorded at the boundary between the layer and the host sediments. The lessons learned from these studies can be applied to terrestrial unconventional settings with appropriate modifications. The work shown here is a means develop methods which enable more reliable terrestrial CSEM monitoring of the flow of injected fluids associated with hydraulic fracturing of unconventional reservoirs and to detect subsurface fluids based on their CSEM signature and in turn, to infer the subsurface flow of electrically conductive injected fluids. The predictive model validated for various 1-D marine, and terrestrial cases focus on the mapping of fluid flow in from a horizontal wellbore in a uniform halfspace using an in-line Horizontal Electric Dipole (HED) with electric field amplitude recorded by an array of electric field sensors. The effect of the of the vertical and horizontal wellbores are documented taking into account the conductivity, size, and thickness of each wellbore. The fracturing fluids flow and conductivity are also taken into account throughout various stages of the fracturing process. In each case, the sensitivity at a location of the surface in-line electric field to a given resistive or conductive layer, due to a source is calculated.

Understanding Subsurface Geoelectrical and Structural Constrains for Low Frequency Radar Sounding of Jovian Satellites

NASA Astrophysics Data System (ADS)

Heggy, Essam; Bruzzone, Lorenzo; Beck, Pierre; Doute, Sylvain; Gim, Youngyu; Herique, Alain; Kofman, Wlodek; Orosei, Roberto; Plaut, Jeffery; Rosen, Paul; Seu, Roberto

2010-05-01

Thermally stable Ice sheets on earth are known to be among the most favorable geophysical contexts for deep subsurface sounding radars. Penetrations ranging from few to several hundreds of meters have been observed at 10 to 60 MHz when sounding homogenous and pure ice sheets in Antarctica and in Alaskan glaciers. Unlike the terrestrial case, ice sheets on Jovian satellites are older formations with a more complex matrix of mineral inclusions with an even three dimensional distribution on the surface and subsurface that is yet to be understood in order to quantify its effect on the dielectric attenuation at the experiment sounding frequencies. Moreover, ridges, tectonic and shock features, may results in a complex and heterogeneous subsurface structure that can induce scattering attenuation with different amplitudes depending on the subsurface heterogeneity levels. Such attenuation phenomena's has to be accounted in the instrument design and future data analysis in order to optimize the science return, reduce mission risk and define proper operation modes. In order to address those challenges in the current performance studies and instrument design of the proposed radar sounding experiments, we present an attempt to quantify both the dielectric and scattering losses on both icy satellites, Ganymede and Europa, based on experimental dielectric characterization of relevant icy-dust mixtures samples, field work from analog environment and radar propagation simulations in parametric subsurface geophysical models representing potential geological scenarios of the two Jovian satellites. Our preliminary results suggest that the use of a dual band radar enable to overcome several of these constrains and reduces ambiguities associated subsurface interface mapping. Acknowledgement. This research is carried out by the Jet Propulsion Laboratory/Caltech, under a grant from the National Aeronautics and Space Administration.

Carbon mineralization in surface and subsurface soils in a subtropical mixed forest in central China

NASA Astrophysics Data System (ADS)

Liu, F.; Tian, Q.

2014-12-01

About a half of soil carbon is stored in subsurface soil horizons, their dynamics have the potential to significantly affect carbon balancing in terrestrial ecosystems. However, the main factors regulating subsurface soil carbon mineralization are poorly understood. As affected by mountain humid monsoon, the subtropical mountains in central China has an annual precipitation of about 2000 mm, which causes strong leaching of ions and nutrition. The objectives of this study were to monitor subsurface soil carbon mineralization and to determine if it is affected by nutrient limitation. We collected soil samples (up to 1 m deep) at three locations in a small watershed with three soil layers (0-10 cm, 10-30 cm, below 30 cm). For the three layers, soil organic carbon (SOC) ranged from 35.8 to 94.4 mg g-1, total nitrogen ranged from 3.51 to 8.03 mg g-1, microbial biomass carbon (MBC) ranged from 170.6 to 718.4 μg g-1 soil. We measured carbon mineralization with the addition of N (100 μg N/g soil), P (50 μg P/g soil), and liable carbon (glucose labeled by 5 atom% 13C, at five levels: control, 10% MBC, 50% MBC, 100% MBC, 200% MBC). The addition of N and P had negligible effects on CO2 production in surface soil layers; in the deepest soil layer, the addition of N and P decreased CO2 production from 4.32 to 3.20 μg C g-1 soil carbon h-1. Glucose addition stimulated both surface and subsurface microbial mineralization of SOC, causing priming effects. With the increase of glucose addition rate from 10% to 200% MBC, the primed mineralization rate increased from 0.19 to 3.20 μg C g-1 soil carbon h-1 (fifth day of glucose addition). The magnitude of priming effect increased from 28% to 120% as soil layers go deep compare to the basal CO2 production (fifth day of 200% MBC glucose addition, basal CO2 production rate for the surface and the deepest soil was 11.17 and 2.88 μg C g-1 soil carbon h-1). These results suggested that the mineralization of subsurface carbon is more sensitive to nutrient addition, and carbon mineralization in this layer is likely limited by carbon availability. Thus, any changes in environment conditions (global warming, nitrogen deposition, precipitation pattern change etc.) that affect the distribution of fresh carbon in soil profiles could then stimulate the release of deep soil carbon.

Microbial Life in the Deep Subsurface: Deep, Hot and Radioactive

NASA Technical Reports Server (NTRS)

DeStefano, Andrea L.; Ford, Jill C.; Winsor, Seana K.; Allen, Carlton C.; Miller, Judith; McNamara, Karen M.; Gibson, Everett K., Jr.

2000-01-01

Recent studies, motivated in part by the search for extraterrestrial life, continue to expand the recognized limits of Earth's biosphere. This work explored evidence for life a high-temperature, radioactive environment in the deep subsurface.

Comparison between infaunal communities of the deep floor and edge of the Tonga Trench: Possible effects of differences in organic matter supply

NASA Astrophysics Data System (ADS)

Leduc, Daniel; Rowden, Ashley A.; Glud, Ronnie N.; Wenzhöfer, Frank; Kitazato, Hiroshi; Clark, Malcolm R.

2016-10-01

Hadal trenches are characterised by environmental conditions not found in any other environment, thereby providing new opportunities to understand the processes that shape deep-sea benthic communities. Technological advances have led to an increase in the number of investigations in hadal trenches over the last two decades. However, more quantitative samples including the deepest parts of trenches is needed to better understand trends in benthic diversity, abundance, biomass and community structure in these extreme habitats, and how these may be shaped by environmental and/or evolutionary factors. In this study, we describe and compare the abundance, biomass, vertical distribution in the sediment, diversity, and community structure of nematodes and other infauna in sediments from the Horizon Deep ( 10 800 m) in the Tonga Trench and a site on the edge of the trench ( 6250 m). Mean nematode abundance was six times greater at the Horizon Deep site (387 ind. 10 cm-2) than at the trench edge site (65 ind. 10 cm-2). A similar pattern was observed for biomass (15 vs 2 μgDW 10 cm-2, respectively), which likely resulted from elevated organic matter supply at the Horizon Deep site. There was no significant difference in nematode species richness between the two sites, but diversity measured using rarefaction was significantly greater at the trench edge site than at the Horizon Deep site [ES(20); 13.8 vs 7.8]. Dominance was much more pronounced in the Horizon Deep, which may be due to competitive exclusion by a small number of opportunistic species. Nematode community structure differed significantly both between sites and among sediment depth layers. The presence of subsurface peaks in pigment concentrations, bacteria abundance, and nematode abundance at the Horizon Deep site is consistent with a recent turbidite event, and may also reflect high rates of bioturbation by larger fauna resulting from high food availability. Determining the relative influences of different environmental factors on hadal trench benthic communities will require further investigation based on quantitative samples encompassing the trench axis as well as the oceanic and continental slopes.

Hydrogen concentrations as an indicator of the predominant terminal electron-accepting reactions in aquatic sediments

USGS Publications Warehouse

Lovley, D.R.; Goodwin, S.

1988-01-01

Factors controlling the concentration of dissolved hydrogen gas in anaerobic sedimentary environments were investigated. Results, presented here or previously, demonstrated that, in sediments, only microorganisms catalyze the oxidation of H2 coupled to the reduction of nitrate, Mn(IV), Fe(III), sulfate, or carbon dioxide. Theoretical considerations suggested that, at steady-state conditions, H2 concentrations are primarily dependent upon the physiological characteristics of the microorganism(s) consuming the H2 and that organisms catalyzing H2 oxidation, with the reduction of a more electrochemically positive electron acceptor, can maintain lower H2 concentrations than organisms using electron acceptors which yield less energy from H2 oxidation. The H2 concentrations associated with the specified predominant terminal electron-accepting reactions in bottom sediments of a variety of surface water environments were: methanogenesis, 7-10 nM; sulfate reduction, 1-1.5 nM; Fe(III) reduction, 0.2 nM; Mn(IV) or nitrate reduction, less than 0.05 nM. Sediments with the same terminal electron acceptor for organic matter oxidation had comparable H2 concentrations, despite variations in the rate of organic matter decomposition, pH, and salinity. Thus, each terminal electron-accepting reaction had a unique range of steady-state H2 concentrations associated with it. Preliminary studies in a coastal plain aquifer indicated that H2 concentrations also vary in response to changes in the predominant terminal electron-accepting process in deep subsurface environments. These studies suggest that H2 measurements may aid in determining which terminal electron-accepting reactions are taking place in surface and subsurface sedimentary environments. ?? 1988.

In-situ Subsurface Soil Analyzer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulmer, Chris

The Department of Energy’s (DOE’s) Terrestrial Ecosystem Science (TES) program is seeking improved sensor systems for monitoring hydro-biogeochemical processes in complex subsurface environments. The TES program is specifically interested in acquiring chemical and structural information regarding the type and nature of the hydration and redox states of subsurface chemical species. The technology should be able to perform on-site and real-time measurements to provide information not available using current sample acquisition and preservation processes. To address the needs of the DOE and the terrestrial science community, Physical Optics Corporation (POC) worked on the development of a new In-Situ Subsurface Soil Analyzermore » (ISSA) based on magnetic resonance technologies. Benchtop testing was performed to assess the feasibility of continuous wave electron pair resonance (CW-EPR) detection of chemical species in subsurface soil systems.« less

Metabolic activity of subseafloor microbes in the South Pacific Gyre

NASA Astrophysics Data System (ADS)

Morono, Y.; Ito, M.; Terada, T.; Inagaki, F.

2013-12-01

The South Pacific Gyre (SPG) is characterized as the most oligotrophic open ocean environment. The sediment is rich in oxygen but poor in energy-sources such as reduced organic matter, and hence harbors very low numbers of microbial cells in relatively shallow subseafloor sediment (D'Hondt et al., 2009; Kallmeyer et al., 2012). In such an energy-limited sedimentary habitat, a small size of microbial community persists living functions with extraordinary low oxygen-consumption rate (Røy et al., 2012). During IODP Expedition 329, a series of sediment samples were successfully recovered from 7 drill sites (U1365-1371) from the seafloor to basement in the SPG, providing an unprecedented opportunity to study metabolic activity of the aerobic subseafloor microbial communities. We initiated incubation onboard by adding stable isotope-labeled substrates to the freshly collected sediment sample, such as 13C and/or 15N-labeled bicarbonate, glucose, amino acids, acetate, and ammonium under the (micro-) aerobic condition. One of the technological challenges in this study is to harvest microbial cells from very low-biomass sediment samples for the analysis using nano-scale secondary ion mass spectrometry (NanoSIMS). To address the technical issue, we improved existing cell separation technique for the SPG sediment samples with small inorganic zeolitic grains. By monitoring cell recovery rates through an image-based cell enumeration technique (Morono et al., 2009), we found that cell recovery rates in the SPG sediment samples are generally lower than those in other oceanographic settings (i.e., organic-rich ocean margin sediments). To gain higher cell recovery ratio, we applied multiple density gradient layers, resulting in the cell recovery ratio up to around 80-95% (Morono et al., in press). Then, using the newly developed cell separation technique, we successfully sorted enough number of microbial cells in small spots on the membrane (i.e., 103 to 105 cells per spot). NanoSIMS analysis showed incorporation of the supplemented stable isotope-labeled substrates after 1.5 year-incubation. The substrate incorporation rates of individual microbial cell ranged in average from 1/10 to 1/2 of those values previously observed in an organic-rich ocean margin sediment (Morono et al., 2011). References S. D'Hondt et al., Subseafloor sedimentary life in the South Pacific Gyre. Proc Natl Acad Sci USA 106, 11651 (2009) J. Kallmeyeret al., Global distribution of microbial abundance and biomass in subseafloor sediment. Proc Natl Acad Sci USA 109, 16213 (2012) H. Røy et al., Aerobic microbial respiration in 86-million-year-old deep-sea red clay. Science 336, 922 (2012) Y. Morono et al. Discriminative detection and enumeration of microbial life in marine subsurface sediments. ISME J 3, 503 (2009) Y. Morono et al., An Improved Cell Separation Technique for Marine Subsurface Sediments: Applications for High-throughput Analysis Using Flow Cytometry and Cell Sorting. Environ Microbiol, (2013) Y. Morono et al., Carbon and nitrogen assimilation in deep subseafloor microbial cells. Proc Natl Acad Sci USA 108, 18295 (2011)

Reconstructing Deep Ocean Circulation in the North Atlantic from Bermuda Rise, and Beyond

NASA Astrophysics Data System (ADS)

McManus, J. F.

2016-12-01

The large-scale subsurface circulation of the ocean is an important component of the Earth's climate system, and contributes to the global and regional transport of heat and mass. Assessing how this system has changed in the past is thus a priority for understanding natural climate variability. A long-coring campaign on Bermuda Rise has provided additional abundant high-quality sediments from this site of rapid accumulation in the deep western basin, situated beneath the subtropical gyre of the North Atlantic Ocean. These sediments allow the high-resolution reconstruction of deepwater chemistry and export from this key location throughout the last 150,000 years, covering the entire last glacial cycle in a continuous section of 35 meters in core KNR191-CDH19. The suite of proxy indicators analyzed includes uranium-series disequilibria, neodymium isotopes, and benthic stable isotopes. Combined with multiple previous studies of nearby cores on Bermuda Rise, the published and new proxy data from CDH19 confirm the variability of the deep circulation in the Atlantic Ocean in association with past climate changes. The multiple indicators, along with complementary data from other locations, display coherent evidence for contrasts between deep circulation during glacial and interglacial intervals, with persistent strong, deep ventilation only within the peak interglacial of marine isotope stage 5e (MIS 5e) and the Holocene. In contrast, repeated, dramatic variability in deep ocean circulation accompanied the millennial climate changes of the last glaciation and deglaciation. The largest magnitude circulation shifts occurred at the transitions into stadials associated with the Hudson strait iceberg discharges and between them and the ensuing northern interstadial warmings, significantly exceeding that of the overall glacial-interglacial difference, highlighting the potential oceanographic and climatic importance of short-term perturbations to the deep ocean circulation.

Effects of legacy nuclear waste on the compositional diversity and distributions of sulfate-reducing bacteria in a terrestrial subsurface aquifer.

PubMed

Bagwell, Christopher E; Liu, Xuaduan; Wu, Liyou; Zhou, Jizhong

2006-03-01

The impact of legacy nuclear waste on the compositional diversity and distribution of sulfate-reducing bacteria in a heavily contaminated subsurface aquifer was examined. dsrAB clone libraries were constructed and restriction fragment length polymorphism (RFLP) analysis used to evaluate genetic variation between sampling wells. Principal component analysis identified nickel, nitrate, technetium, and organic carbon as the primary variables contributing to well-to-well geochemical variability, although comparative sequence analysis showed the sulfate-reducing bacteria community structure to be consistent throughout contaminated and uncontaminated regions of the aquifer. Only 3% of recovered dsrAB gene sequences showed apparent membership to the Deltaproteobacteria. The remainder of recovered sequences may represent novel, deep-branching lineages that, to our knowledge, do not presently contain any cultivated members; although corresponding phylotypes have recently been reported from several different marine ecosystems. These findings imply resiliency and adaptability of sulfate-reducing bacteria to extremes in environmental conditions, although the possibility for horizontal transfer of dsrAB is also discussed.

Fishing activities

USGS Publications Warehouse

Oberle, Ferdinand; Puig, Pere; Martin, Jacobo; Micallef, Aaron; Krastel, Sebastian; Savini, Alessandra

2018-01-01

Unlike the major anthropogenic changes that terrestrial and coastal habitats underwent during the last centuries such as deforestation, river engineering, agricultural practices or urbanism, those occurring underwater are veiled from our eyes and have continued nearly unnoticed. Only recent advances in remote sensing and deep marine sampling technologies have revealed the extent and magnitude of the anthropogenic impacts to the seafloor. In particular, bottom trawling, a fishing technique consisting of dragging a net and fishing gear over the seafloor to capture bottom-dwelling living resources has gained attention among the scientific community, policy makers and the general public due to its destructive effects on the seabed. Trawling gear produces acute impacts on biota and the physical substratum of the seafloor by disrupting the sediment column structure, overturning boulders, resuspending sediments and imprinting deep scars on muddy bottoms. Also, the repetitive passage of trawling gear over the same areas creates long-lasting, cumulative impacts that modify the cohesiveness and texture of sediments. It can be asserted nowadays that due to its recurrence, mobility and wide geographical extent, industrial trawling has become a major force driving seafloor change and affecting not only its physical integrity on short spatial scales but also imprinting measurable modifications to the geomorphology of entire continental margins.

Morphogenesis of the SW Balearic continental slope and adjacent abyssal plain, Western Mediterranean Sea

NASA Astrophysics Data System (ADS)

Camerlenghi, Angelo; Accettella, Daniela; Costa, Sergio; Lastras, Galderic; Acosta, Juan; Canals, Miquel; Wardell, Nigel

2009-06-01

We present the seafloor morphology and shallow seismic structure of the continental slope south-east of the Balearic promontory and of the adjacent Algero-Balearic abyssal plain from multibeam and chirp sonar data. The main purpose of this research was to identify the sediment pathways from the Balearic promontory to the Algero-Balearic deep basin from the Early Pliocene to the Present. The morphology of the southern Balearic margin is controlled by a SW-NE structural trend, whose main expressions are the Emile Baudot Escarpment transform fault, and a newly discovered WSW-ENE trend that affects the SW end of the escarpment and the abyssal plain. We relate the two structural trends to right-lateral simple shear as a consequence of the Miocene westward migration of the Gibraltar Arc. Newly discovered steep and narrow volcanic ridges were probably enabled to grow by local transtension along the transform margin. Abyssal plain knolls and seahills relate to the subsurface deformation of early stage halokinetic structures such as salt rollers, salt anticlines, and salt pillows. The limited thickness of the overburden and the limited amount of deformation in the deep basin prevent the formation of more mature halokinetic structures such as diapirs, salt walls, bulbs, and salt extrusions. The uppermost sediment cover is affected by a dense pattern of sub-vertical small throw normal faults resulting from extensional stress induced in the overburden by subsurface salt deformation structures. Shallow gas seismic character and the possible presence of an active polygonal fault system suggest upward fluid migration and fluid and sediment expulsion at the seafloor through a probable mud volcano and other piercement structures. One large debris flow deposit, named Formentera Debris Flow, has been identified on the lower slope and rise of the south Formentera margin. Based on current observations, we hypothesize that the landslide originating the Formentera Debris Flow occurred in the Holocene, perhaps in historical times.

Carboxydotrophy potential of uncultivated Hydrothermarchaeota from the oceanic crust deep biosphere

NASA Astrophysics Data System (ADS)

Carr, S. A.; Jungbluth, S.; Rappe, M. S.; Orcutt, B.

2017-12-01

The marine sedimentary and crustal subsurface biospheres harbor many uncultured microorganisms, including those belonging to Hydrothermarchaeota, formerly known as Marine Benthic Group E. SSU rRNA sequences of Hydrothermarchaeota have been identified in marine sediments across the globe, often in low abundance. Recently, crustal fluids from two subseafloor borehole observatories located on the eastern flank of the Juan de Fuca Ridge (i.e., CORKs at IODP Holes U1362A and U1362B), were collected for single-cell and metagenomic analyses. Both techniques revealed Hydrothermarchaeota to be prevalent in this system. Collectively, single-cell amplified genomes (SAGs) and metagenome-assembled genomes (MAGs) depict Hydrothermarchaeota as opportunists, potentially capable of dissimilative and assimilative carboxydotrophy, sulfate reduction, thiosulfate reduction, nitrate reduction, chemotaxis, and motility. We propose that this diverse suit of metabolic potential may be advantageous for the hydrologically and geochemically dynamic subsurface crustal aquifer, an environment thought to be energy and nutrient limited.

Terrestrial Diapirs as Analogs to Europa's Lenticulae and Chaos, and Implications for Europa Exploration

NASA Astrophysics Data System (ADS)

Pappalardo, R. T.

2007-12-01

Ice diapirism has been cited to explain Europa's pits, spots, and domes (commonly collectively referred to as "lenticulae") as well as the satellite's larger chaos terrains. Europa's diapirs have been modeled as thermal- compositional in origin, rising within an ice shell greater than ~20 km thick. The morphologies and characteristics of terrestrial diapirs shed light on possible diapiric processes within Europa. Diapirs commonly rise in fields of similarly sized subcircular features which can intrude into the shallow subsurface or extrude onto the surface. Rim synclines (peripheral depressions) may form in response to withdrawal of diapiric material from a diapir's surroundings, and peripheral and crestal faults are predicted above intrusive diapirs. The heads of neighboring synchronously active diapirs can flatten against one another. Each of these terrestrial characteristics is consistent with the morphologies of some Europan lenticulae. Terrestrial diapiric heads can merge into a broad canopy, potentially analogous to the formation of some Europan chaos terrains. Xenoliths can be carried upward within terrestrial diapirs, suggesting that diapirism within Europa's ice shell can dredge deep material up toward the surface on the timescale of diapir rise. The deepest strata rise into the central axes of terrestrial diapirs, implying that materials from greatest depth in Europa's ice shell may be exposed in the centers of individual extrusive lenticulae and in discrete locations within chaos regions. Lenticulae and chaos are high priority locations to explore for materials that have risen from near Europa's ice-ocean interface to the surface.

Hydrology of two slopes in subarctic Yukon, Canada

NASA Astrophysics Data System (ADS)

Carey, Sean K.; Woo, Ming-Ko

1999-11-01

Two subarctic forested slopes in central Wolf Creek basin, Yukon, were studied in 1996-1997 to determine the seasonal pattern of the hydrologic processes. A south-facing slope has a dense aspen forest on silty soils with seasonal frost only and a north-facing slope has open stands of black spruce and an organic layer on top of clay sediments with permafrost. Snowmelt is advanced by approximately one month on the south-facing slope due to greater radiation receipt. Meltwater infiltrates its seasonally frozen soil with low ice content, recharging the soil moisture reservoir but yielding no lateral surface or subsurface flow. Summer evaporation depletes this recharged moisture and any additional rainfall input, at the expense of surface or subsurface flow. The north-facing slope with an ice rich substrate hinders deep percolation. Snow meltwater is impounded within the organic layer to produce surface runoff in rills and gullies, and subsurface flow along pipes and within the matrix of the organic soil. During the summer, most subsurface flows are confined to the organic layer which has hydraulic conductivities orders of magnitudes larger than the underlying boulder-clay. Evaporation on the north-facing slope declines as both the frost table and the water table descend in the summer. A water balance of the two slopes demonstrates that vertical processes of infiltration and evaporation dominate moisture exchanges on the south-facing slope, whereas the retardation of deep drainage by frost and by clayey soil on the permafrost slope promotes a strong lateral flow component, principally within the organic layer. These results have the important implication that permafrost slopes and organic horizons are the principal controls on streamflow generation in subarctic catchments.

Mechanisms of Arsenic Mobilization and Attenuation in Subsurface Sediments

NASA Astrophysics Data System (ADS)

O'Day, P. A.; Illera, V.; Root, R.; Choi, S.; Vlassopoulos, D.

2007-12-01

This talk will review molecular mechanisms of As mobilization and attenuation in subsurface sediments using examples from recent field studies that represent a range in oxidation-redox (redox) potential. As a ubiquitous trace element in sediments, As speciation and fate is linked to the abundance and biogeochemical behavior of the generally more abundant redox-active elements Fe, S, and Mn. All four elements are subject to oxidation, reduction, and pH-dependent processes such as sorption, desorption, precipitation, and dissolution, and which may include both biotic and abiotic reaction steps. We have used spectroscopic interrogation and geochemical modeling to characterize As speciation in subsurface sediments in several contrasting environments, including high and low S and Fe settings. Aquifers most at risk for contamination by As include those that are rich in organic matter and nutrients, stimulating high rates of microbial reduction and creating anoxic conditions, but limited in labile or available S and/or Fe that remove As by precipitation or adsorption. In subsurface sediments with low labile S and Fe, laboratory experiments and spectroscopic studies suggest that sediment Mn minerals are important in the oxidation of sorbed As(III) to As(V), but that they have a limited oxidation capacity. Arsenic attenuation and mobilization in the subsurface are affected by seasonal variations when hydraulic conditions are influenced by surface infiltration, which may induce transitions from oxidized to reduced conditions (or vice versa) in porewater.

Streambed microstructure predicts evolution of development and life history mode in the plethodontid salamander Eurycea tynerensis

PubMed Central

Bonett, Ronald M; Chippindale, Paul T

2006-01-01

Background Habitat variation strongly influences the evolution of developmentally flexible traits, and may drive speciation and diversification. The plethodontid salamander Eurycea tynerensis is endemic to the geologically diverse Ozark Plateau of south-central North America, and comprises both strictly aquatic paedomorphic populations (achieving reproductive maturity while remaining in the larval form) and more terrestrial metamorphic populations. The switch between developmental modes has occurred many times, but populations typically exhibit a single life history mode. This unique system offers an opportunity to study the specific ecological circumstances under which alternate developmental and life history modes evolve. We use phylogenetic independent contrasts to test for relationships between a key microhabitat feature (streambed sediment) and this major life history polymorphism. Results We find streambed microstructure (sediment particle size, type and degree of sorting) to be highly correlated with life-history mode. Eurycea tynerensis is paedomorphic in streams containing large chert gravel, but metamorphoses in nearby streams containing poorly sorted, clastic material such as sandstone or siltstone. Conclusion Deposits of large chert gravel create loosely associated streambeds, which provide access to subsurface water during dry summer months. Conversely, streambeds composed of more densely packed sandstone and siltstone sediments leave no subterranean refuge when surface water dries, presumably necessitating metamorphosis and use of terrestrial habitats. This represents a clear example of the relationship between microhabitat structure and evolution of a major developmental and life history trait, and has broad implications for the role of localized ecological conditions on larger-scale evolutionary processes. PMID:16512919

Controls on subsurface methane fluxes and shallow gas formation in Baltic Sea sediment (Aarhus Bay, Denmark)

NASA Astrophysics Data System (ADS)

Flury, Sabine; Røy, Hans; Dale, Andrew W.; Fossing, Henrik; Tóth, Zsuzsanna; Spiess, Volkhard; Jensen, Jørn Bo; Jørgensen, Bo Barker

2016-09-01

Shallow gas accumulates in coastal marine sediments when the burial rate of reactive organic matter beneath the sulfate zone is sufficiently high and the methanogenic zone is sufficiently deep. We investigated the controls on methane production and free methane gas accumulation along a 400 m seismo-acoustic transect across a sharp transition from gas-free into gas-bearing sediment in Aarhus Bay (Denmark). Twelve gravity cores were taken, in which the pore water was analyzed for inorganic solutes while rates of organic carbon mineralization were measured experimentally by 35SO42- radiotracer method. The thickness of organic-rich Holocene mud increased from 5 to 10 m along the transect concomitant with a shallowing of the depth of the sulfate-methane transition from >4 m to 2.5 m. In spite of drastic differences in the distribution of methane and sulfate in the sediment along the transect, there were only small differences in total mineralization, and methanogenesis was only equivalent to about 1% of sulfate reduction. Shallow gas appeared where the mud thickness exceeded 8-9 m. Rates of methanogenesis increased along the transect as did the upward diffusive flux of methane. Interestingly, the increase in the sedimentation rate and Holocene mud thickness had only a modest direct effect on methanogenesis rates in deep sediments. This increase in methane flux, however, triggered a shallowing of the sulfate-methane transition which resulted in a large increase in methanogenesis at the top of the methanogenic zone. Thus, our results demonstrate a positive feedback mechanism that causes a strong enhancement of methanogenesis and explains the apparently abrupt appearance of gas when a threshold thickness of organic-rich mud is exceeded.

Organic matter in sediment layers of an acidic mining lake as assessed by lipid analysis. Part II: Neutral lipids.

PubMed

Poerschmann, Juergen; Koschorreck, Matthias; Górecki, Tadeusz

2017-02-01

Natural neutralization of acidic mining lakes is often limited by organic matter. The knowledge of the sources and degradability of organic matter is crucial for understanding alkalinity generation in these lakes. Sediments collected at different depths (surface sediment layer from 0 to 1 cm and deep sediment layer from 4 to 5cm) from an acidic mining lake were studied in order to characterize sedimentary organic matter based on neutral signature markers. Samples were exhaustively extracted, subjected to pre-chromatographic derivatizations and analyzed by GC/MS. Herein, molecular distributions of diagnostic alkanes/alkenes, terpenes/terpenoids, polycyclic aromatic hydrocarbons, aliphatic alcohols and ketones, sterols, and hopanes/hopanoids were addressed. Characterization of the contribution of natural vs. anthropogenic sources to the sedimentary organic matter in these extreme environments was then possible based on these distributions. With the exception of polycyclic aromatic hydrocarbons, combined concentrations across all marker classes proved higher in the surface sediment layer as compared to those in the deep sediment layer. Alkane and aliphatic alcohol distributions pointed to predominantly allochthonous over autochthonous contribution to sedimentary organic matter. Sterol patterns were dominated by phytosterols of terrestrial plants including stigmasterol and β-sitosterol. Hopanoid markers with the ββ-biohopanoid "biological" configuration were more abundant in the surface sediment layer, which pointed to higher bacterial activity. The pattern of polycyclic aromatic hydrocarbons pointed to prevailing anthropogenic input. Pyrolytic makers were likely to due to atmospheric deposition from a nearby former coal combustion facility. The combined analysis of the array of biomarkers provided new insights into the sources and transformations of organic matter in lake sediments. Copyright © 2016 Elsevier B.V. All rights reserved.

Alteration textures in terrestrial volcanic glass and the associated bacterial community.

PubMed

Cockell, C S; Olsson-Francis, K; Herrera, A; Meunier, A

2009-01-01

Alteration textures were examined in subglacial (hyaloclastite) deposits at Valafell, Southern Iceland. Pitted and 'elongate' alteration features are observed in the glass similar to granular and tubular features reported previously in deep-ocean basaltic glasses, but elongate features generally did not have a length to width ratio greater than five. Elongate features were found in only 7% of surfaces. Crystalline basalt clasts, which are incorporated into the hyaloclastite, did not display elongate structures. Pitted alteration features were poorly defined in crystalline basalt, comprising only 4% of the surface compared to 47% in the case of basaltic glass. Examination of silica-rich glass (obsidian) and rhyolite similarly showed poorly defined pitted textures that comprised less than 15% of the surface and no elongate features were observed. These data highlight the differences in alteration textures between terrestrial basaltic glass and previously studied deep-ocean and subsurface basaltic glass, and the important role of mineralogy in controlling the type and abundance of alteration features. The hyaloclastite contains a diverse and abundant bacterial population, as determined by 16S rDNA analysis, which could be involved in weathering the glass. Despite the presence of phototrophs, we show that they were not involved in the production of most alteration textures in the basaltic glass materials we examined.

Improved measurement of extracellular enzymatic activities in subsurface sediments using competitive desorption treatment

NASA Astrophysics Data System (ADS)

Hoarfrost, Adrienne; Snider, Rachel; Arnosti, Carol

2017-02-01

Extracellular enzymatic activities initiate microbially-driven heterotrophic carbon cycling in subsurface sediments. While measurement of hydrolytic activities in sediments is fundamental to our understanding of carbon cycling, these measurements are often technically difficult due to sorption of organic substrates to the sediment matrix. Most methods that measure hydrolysis of organic substrates in sediments rely on recovery of a fluorophore or fluorescently-labeled target substrate from a sediment incubation. The tendency for substrates to sorb to sediments results in lower recovery of an added substrate, and can result in data that are unusable or difficult to interpret. We developed a treatment using competitive desorption of a fluorescently-labeled, high molecular weight organic substrate that improves recovery of the labeled substrate from sediment subsamples. Competitive desorption treatment improved recovery of the fluorescent substrate by a median of 66%, expanded the range of sediments for which activity measurements could be made, and was effective in sediments from a broad range of geochemical contexts. More reliable measurements of hydrolytic activities in sediments will yield usable and more easily interpretable data from a wider range of sedimentary environments, enabling better understanding of microbially-catalyzed carbon cycling in subsurface environments.

Megafans as Hydrous Environments

NASA Technical Reports Server (NTRS)

Wilkinson, M. Justin; Miller, R. McG.; Allen, C. C.; Kreslavsky, M. H.; Eckardt, F.

2009-01-01

The mesoscale sedimentary environment known as the megafan, is a low-angle, partial cone of fluvial sediment generated where a river enters an unconfined basin where it begins the process of avulsing over wide areas. In shifting to different positions, the river lays down a partial cone of sediment and establishes a characteristic radial pattern of paleo courses. The apparent paucity of sedimentary bodies obviously tied to martian outflow channels may also relate to the difficulty of recognition due to their sheer size and featurelessness. However, the existence of megafans on Mars is being examined now that their ubiquity and characteristics on Earth are better understood. Accordingly we suggest two likely candidates on Mars: Maja Valles fluvial cone and Amazonis Planitia fluvial sedimentary bodies. Two cryptic examples from Amazonis Planitia may be important for understanding subsurface hydrous accumulation. For at least some of its history, discharges from Mangala Valles likely resulted in megafans. Distances from the end of Mangala Valles to the northern (low) margin of the planitia are very large, a fact that has suggested that fluvial emplacement was unlikely. However, the megafan model shows that long megafan radii are indeed feasible. It has been suggested further that discharge from Labou Vallis (8.5S 154.5W) must have led to fluvial sedimentation in the planitia. We suggest that during locally non-lacustrine/ocean phases, this sedimentation would have occurred in the form of megafans. However, the megafan model shows that long megafan radii are indeed feasible. It has been suggested further that discharge from Labou Vallis (8.5S 154.5W) must have led to fluvial sedimentation in the planitia. We suggest that during locally non-lacustrine/ocean phases, this sedimentation would have occurred in the form of megafans. Megafans emanating from Marte, Mangala and Labou valles have probably contributed to hydrous near-subsurface environments--in their distal reaches, i.e. along the northern, eastern and southeastern margins of Amazonis Planitia at various times. Following a new terrestrial analog, we conclude groundwater has at times accumulated preferentially beneath distal slopes of the Maja Valles feature, and along the northern, eastern and southeastern margins of Amazonis Planitia.

viral abundance distribution in deep waters of the Northern of South China Sea

NASA Astrophysics Data System (ADS)

He, Lei; Yin, Kedong

2017-04-01

Little is known about the vertical distribution and interaction of viruses and bacteria in the deep ocean water column. The vertical distribution of viral-like particles and bacterial abundance was investigated in the deep water column in the South China Sea during September 2005 along with salinity, temperature and dissolved oxygen. There were double maxima in the ratio of viral to bacterial abundance (VBR) in the water column: the subsurface maximum located at 50-100 m near the pycnocline layer, and the deep maximum at 800-1000 m. At the subsurface maximum of VBR, both viral and bacterial abundance were maximal in the water column, and at the deep maximum of VBR, both viral and bacterial abundance were low, but bacterial abundance was relatively lower than viral abundance. The subsurface VBR maximum coincided with the subsurface chlorophyll maximum while the deep VBR maximum coincided with the minimum in dissolved oxygen (2.91mg L-1). Therefore, we hypothesize that the two maxima were formed by different mechanisms. The subsurface VBR maximum was formed due to an increase in bacterial abundance resulting from the stimulation of abundant organic supply at the subsurface chlorophyll maximum, whereas the deep VBR maximum was formed due to a decrease in bacterial abundance caused by more limitation of organic matter at the oxygen minimum. The evidence suggests that viruses play an important role in controlling bacterial abundance in the deep water column due to the limitation of organic matter supply. In turn, this slows down the formation of the oxygen minimum in which oxygen may be otherwise lower. The mechanism has a great implication that viruses could control bacterial decomposition of organic matter, oxygen consumption and nutrient remineralization in the deep oceans.

Active microbial biofilms in deep poor porous continental subsurface rocks.

PubMed

Escudero, Cristina; Vera, Mario; Oggerin, Monike; Amils, Ricardo

2018-01-24

Deep continental subsurface is defined as oligotrophic environments where microorganisms present a very low metabolic rate. To date, due to the energetic cost of production and maintenance of biofilms, their existence has not been considered in poor porous subsurface rocks. We applied fluorescence in situ hybridization techniques and confocal laser scanning microscopy in samples from a continental deep drilling project to analyze the prokaryotic diversity and distribution and the possible existence of biofilms. Our results show the existence of natural microbial biofilms at all checked depths of the Iberian Pyrite Belt (IPB) subsurface and the co-occurrence of bacteria and archaea in this environment. This observation suggests that multi-species biofilms may be a common and widespread lifestyle in subsurface environments.

Archive of Sediment Data Collected around the Chandeleur Islands and Breton Island in 2007 and 1987 (Vibracore Surveys: 07SCC04, 07SCC05, and 87039)

USGS Publications Warehouse

Dreher, C.A.; Flocks, J.G.; Kulp, M.A.; Ferina, N.F.

2010-01-01

In 2006 and 2007, the U.S. Geological Survey (USGS) and collaborators at the University of New Orleans (UNO) collected high-resolution seismic profiles and subsurface cores around the Chandeleur and Breton Islands, Louisiana (Study Area Map). To ground-truth the acoustic seismic surveys conducted in 2006, 124 vibracores were acquired during the 07SCC04 and 07SCC05 cruises in 2007. These cores were collected within the back-barrier, nearshore, and offshore environments. The surveys were conducted as part of a post-hurricane assessment and sediment resource inventory for the Barrier Island Coastal Monitoring (BICM) project. Vibracores were collected offshore using the USGS R/V G.K. Gilbert, while the terrestrial, back-barrier, and nearshore vibracores were collected from the UNO R/V Greenhead. This report serves as an archive of sediment data from two concurrent vibracore surveys (cruises 07SCC04 and 07SCC05) from around the Breton and Chandeleur Islands in 2007 and also documents sediment data from vibracores collected offshore of the Chandeleur Islands in 1987 (cruise 87039). The 1987 vibracores were collected through the collaborated efforts of the USGS, Louisiana Geological Survey (LGS), and Alpine Ocean Seismic. Each vibracore can be identified by cruise and core number.

Microcosm studies of subsurface PAH-degrading bacteria from a former manufactured gas plant

NASA Astrophysics Data System (ADS)

Durant, Neal D.; Wilson, Liza P.; Bouwer, Edward J.

1995-01-01

A study was conducted to evaluate the potential for natural in situ biodegradation of polycyclic aromatic hydrocarbons (PAH's) in the subsurface at the site of a former manufactured gas plant. Fifty-seven samples of unconsolidated subsurface sediments were aseptically obtained from five boreholes across the site. Bacteria capable of aerobically degrading PAH's without an acclimation period were detected throughout shallow (2.7 m) and deep (24.7 m) areas of the subsurface in both relatively clean (<20 μg L -1 naphthalene) and contaminated (4400 μg L -1 naphthalene) zones. Significant ( p < 0.05) quantities of naphthalene (8±3% to 43±7%) and/or phenanthrene (3±1% to 31±3%) were mineralized in sediment-groundwater microcosms during 4 weeks of aerobic incubation at 22°C. Three samples out of 11 were able to aerobically mineralize significant quantities of benzene (6±2% to 24±1%). Of 11 samples tested for anaerobic mineralization, naphthalene biodegradation (7±1% to 13±2%) in the presence of N03 was observed in two samples. Compound removals were first order with respect to substrate concentration during the first 10-15 days of incubation. Compound biodegradation plateaued in the later stages of incubation (15-40 days), most likely from diminishing bioavailability and nutrient and oxygen depletion. Population densities in the sediments were typically low, with viable aerobic counts ranging from 0 to 10 5 CFU gdw -1, viable anaerobic counts ranging from 0 to 104 CFU gdw -1, and total counts (AODC) usually 10-fold greater than viable counts. Total counts exhibited a strong ( p < 0.01) positive correlation with sample grain size. Viable aerobic and anaerobic populations commonly occurred in the same sample, suggesting the presence of facultative anaerobes. Bacteria were metabolically active in samples from groundwaters with low pH (3.7) and high naphthalene concentrations (11,000 μg L -1). Data from these enumeration and microcosm studies suggest that natural in situ biodegradation is occurring at the site.

Volatile organic compounds in Gulf of Mexico sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDonald, T.J.

1988-01-01

Volatile organic compounds (VOC), concentrations and compositions were documented for estuarine, coastal, shelf, slope, and deep water sediments from the Gulf of Mexico. VOC were measured (detection limit >0.01 ppb) using a closed-loop stripping apparatus with gas chromatography (GC) and flame ionization, flame photometric, and mass spectrometric detectors. The five primary sources of Gulf of Mexico sediment VOC are: (1) planktonic and benthic fauna and flora; (2) terrestrial material from riverine and atmospheric deposition; (3) anthropogenic inputs: (4) upward migration of hydrocarbons; and (5) transport by bottom currents or slumping. Detected organo-sulfur compounds include alkylated sulfides, thiophene, alkylated thiophenes, andmore » benzothiophenes. Benzothiophenes are petroleum related. Low molecular weight organo-sulfur compounds result from the biological oxidation of organic matter. A lack of organosulfur compounds in the reducing environment of the Orca Basin may result from a lack of free sulfides which are necessary for their production.« less

Nontoxic chemical process for in situ permeability enhancement and accelerated decontamination of fine-grain subsurface sediments

DOEpatents

Kansa, E.J.; Wijesinghe, A.M.; Viani, B.E.

1997-01-14

The remediation of heterogeneous subsurfaces is extremely time consuming and expensive with current and developing technologies. Although such technologies can adequately remove contaminants in the high hydraulic conductivity, coarse-grained sediments, they cannot access the contaminated low hydraulic conductivity fine-grained sediments. The slow bleed of contaminants from the fine-grained sediments is the primary reason why subsurface remediation is so time-consuming and expensive. This invention addresses the problem of remediating contaminated fine-grained sediments. It is intended that, in the future, a heterogeneous site be treated by a hybrid process that first remediates the high hydraulic conductivity, coarse-grained sediments, to be followed by the process, described in this invention, to treat the contaminated low hydraulic conductivity fine-grained sediments. The invention uses cationic flocculants and organic solvents to collapse the swelling negative double layer surrounding water saturated clay particles, causing a flocculated, cracked clay structure. The modification of the clay fabric in fine-grained sediments dramatically increases the hydraulic conductivity of previously very tight clays many orders of magnitude. 8 figs.

Nontoxic chemical process for in situ permeability enhancement and accelerated decontamination of fine-grain subsurface sediments

DOEpatents

Kansa, Edward J.; Wijesinghe, Ananda M.; Viani, Brian E.

1997-01-01

The remediation of heterogeneous subsurfaces is extremely time consuming and expensive with current and developing technologies. Although such technologies can adequately remove contaminants in the high hydraulic conductivity, coarse-grained sediments, they cannot access the contaminated low hydraulic conductivity fine-grained sediments. The slow bleed of contaminants from the fine-grained sediments is the primary reason why subsurface remediation is so time-consuming and expensive. This invention addresses the problem of remediating contaminated fine-grained sediments. It is intended that, in the future, a heterogeneous site be treated by a hybrid process that first remediates the high hydraulic conductivity, coarse-grained sediments, to be followed by the process, described in this invention, to treat the contaminated low hydraulic conductivity fine-grained sediments. The invention uses cationic flocculents and organic solvents to collapse the swelling negative double layer surrounding water saturated clay particles, causing a flocculated, cracked clay structure. The modification of the clay fabric in fine-grained sediments dramatically increases the hydraulic conductivity of previously very tight clays many orders of magnitude.

Multi-method investigation of cushion peatlands (

NASA Astrophysics Data System (ADS)

Forbriger, M.; Schittek, K.; Höfle, B.; Siart, C.; Eitel, B.

2012-04-01

This study presents a multi-method and multi-proxy approach for palaeonvironmental investigations in the western andean cordillera of southern Peru (Lucanas province, 14° S) using cushion peatlands as terrestrial geoarchives. The region stretching between the Altiplano and the Peruvian desert in the lowland shares a long term settlement history, in which local cultures adapted to climate change in many different ways. Being one of the most outstanding human remains, the abri below Cerro Llamoca, 4.450 m a.s.l. in the uppermost ranges of the Llamoca peatland catchment area further reveals an occupation history of almost 10.000 years, as revealed by latest archaeological investigations. In remote and highly elevated regions such as the central Andes, cushion peatlands basically represent the only high resolution terrestrial archives suitable for geoarchaeological and palaeoenvironmental studies. Characterized by high accumulation rates, they ideally document environmental changes, particularly at small time intervals. Within the multidisciplinary project 'Andean Transect - Climate Sensitivity of pre-Columbian Man-Environment-Systems' several sediment cores with depths up to 11.5 m b.s. were recovered from the Llamoca peatland. Based on almost 100 AMS 14C-datings they provide a chronology of 8000 years and, thus, offer profound insights into climatic and environmental changes in the study area. While nearly homogeneous peat layers record stable environmental conditions, the heterogeneous granulometric composition of intercalated sediment layers documents several periods of intense geomorphodynamic activity. Due to high resolution geochemical analyses of peat layers (1 cm interval; humification degree, CNS measurements, XRF-scanning), the existence of slight and short-term trends of landscape development during these phases can be identified. Additional pollen, charred particles and plant macrofossil analyses confirm these findings and help reconstructing local vegetation history. High-resolution digital elevation models derived from terrestrial laser scanning (TLS) provide important input data for geomorphologic analyses on current geomorphic processes that can be transferred to former times. Detailed subsurface information obtained by geophysics (electrical resistivity tomography ERT) helped identify the most suitable sampling sites. Information about peat thickness, stratigraphy and depth to bedrock was combined with topographical elevation data, chronometrical outcomes and palaeoenvironmental parameters to generate subsurface models of the study site. The findings allow reconstructing and visualizing the ancient landscape and the stages of peat development, which coincide with pre-Columbian cultural eras.

Orbital SAR and Ground-Penetrating Radar for Mars: Complementary Tools in the Search for Water

NASA Technical Reports Server (NTRS)

Campbell, B. A.; Grant, J. A.

2000-01-01

The physical structure and compositional variability of the upper martian crust is poorly understood. Optical and infrared measurements probe at most the top few cm of the surface layer and indicate the presence of layered volcanics and sediments, but it is likely that permafrost, hydrothermal deposits, and transient liquid water pockets occur at depths of meters to kilometers within the crust. An orbital synthetic aperture radar (SAR) can provide constraints on surface roughness, the depth of fine-grained aeolian or volcanic deposits, and the presence of strongly absorbing near-surface deposits such as carbonates. This information is crucial to the successful landing and operation of any rover designed to search for subsurface water. A rover-based ground-penetrating radar (GPR) can reveal layering in the upper crust, the presence of erosional or other subsurface horizons, depth to a permafrost layer, and direct detection of near-surface transient liquid water. We detail here the radar design parameters likely to provide the best information for Mars, based on experience with SAR and GPR in analogous terrestrial or planetary environments.

Terrestrial organic carbon contributions to sediments on the Washington margin

NASA Astrophysics Data System (ADS)

Prahl, F. G.; Ertel, J. R.; Goni, M. A.; Sparrow, M. A.; Eversmeyer, B.

1994-07-01

Elemental and stable carbon isotopic compositions and biomarker concentrations were determined in sediments from the Columbia River basin and the Washington margin in order to evaluate geochemical approaches for quantifying terrestrial organic matter in marine sediments. The biomarkers include: an homologous series of long-chain n-alkanes derived from the surface waxes of higher plants; phenolic and hydroxyalkanoic compounds produced by CuO oxidation of two major vascular plant biopolymers, lignin and cutin. All marine sediments, including samples collected from the most remote sites in Cascadia Basin, showed organic geochemical evidence for the presence of terrestrial organic carbon. Using endmember values for the various biomarkers determined empirically by two independent means, we estimate that the terrestrial contribution to the Washington margin is ~ 60% for shelf sediments, ~ 30% for slope sediments, and decreases further to ≤15% in basin sediments. Results from the same geochemical measurements made with depth in gravity core 6705-7 from Cascadia Seachannel suggest that our approach to assess terrestrial organic carbon contributions to contemporary deposits on the Washington margin can be applied to the study of sediments depositing in this region since the last glacial period.

The life sulfuric: microbial ecology of sulfur cycling in marine sediments.

PubMed

Wasmund, Kenneth; Mußmann, Marc; Loy, Alexander

2017-08-01

Almost the entire seafloor is covered with sediments that can be more than 10 000 m thick and represent a vast microbial ecosystem that is a major component of Earth's element and energy cycles. Notably, a significant proportion of microbial life in marine sediments can exploit energy conserved during transformations of sulfur compounds among different redox states. Sulfur cycling, which is primarily driven by sulfate reduction, is tightly interwoven with other important element cycles (carbon, nitrogen, iron, manganese) and therefore has profound implications for both cellular- and ecosystem-level processes. Sulfur-transforming microorganisms have evolved diverse genetic, metabolic, and in some cases, peculiar phenotypic features to fill an array of ecological niches in marine sediments. Here, we review recent and selected findings on the microbial guilds that are involved in the transformation of different sulfur compounds in marine sediments and emphasise how these are interlinked and have a major influence on ecology and biogeochemistry in the seafloor. Extraordinary discoveries have increased our knowledge on microbial sulfur cycling, mainly in sulfate-rich surface sediments, yet many questions remain regarding how sulfur redox processes may sustain the deep-subsurface biosphere and the impact of organic sulfur compounds on the marine sulfur cycle. © 2017 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.

Ocean Drilling Program Contributions to the Understanding of the Deep Subsurface Biosphere

NASA Astrophysics Data System (ADS)

Fisk, M. R.

2003-12-01

Tantalizing evidence for microbes in oceanic basalts has been reported for a few decades, but it was from rocks cored on Ocean Drilling Program (ODP) Leg 148 in 1993 that the first clear-cut evidence of microbial invasion of ocean basalts was obtained. (Work on ODP legs, starting with Leg 112 in 1986, had already revealed the presence of significant microbial biomass in sediments.) In 1997 ODP created the Deep Biosphere Program Planning Group to promote the investigation of the microbiology of the ocean crust. In 1999 ODP built a microbiology lab on the JOIDES Resolution, and used the lab that year (Legs 185 and 187) to test the amount of microbial contamination introduced into rocks during drilling and to establish cultures from cored basalts. These experiments have been repeated on several legs since then. The development of CORKs has permitted long-term sampling of subseafloor fluids, and microorganisms have been recovered from CORKed holes. Thus, ODP made it possible for the scientific community to address major questions about the biology of the igneous crust, such as, (1) What microbes are present? (2) How abundant are they? (3) How are they distributed? DNA from basalts and subseafloor fluids reveal what types of organisms are present. Cell abundance and biomass have been estimated based on cell counts and on organic content of basalts. Surveys of basalts in DSDP/ODP repositories indicate that microorganisms are ubiquitous in the igneous crust. Microorganisms are found in rocks that are close to 100° C. They are found as deep as 1500 m below the sea floor, and in rocks as young as a few years and as old as 170 million years. Because of the vast size of the habitat, microorganism, even if present in small numbers, could be a significant fraction of the Earth's biomass. In a short time ODP contributed to advances in our understanding of the oceanic subsurface biosphere. Answers to other significant questions such as: (1) How do the microorganisms live?, (2) What impact do subsurface microorganisms have on the surface biosphere? (3) And, what roles do the subsurface biosphere play in element cycling? will be answered by future drilling. The International Ocean Drilling Program (IODP) is in the enviable position of providing support to address these key questions about the Earth's subsurface biosphere.

Snow on the Seafloor? Methods to Detect Carbohydrates in Deep-sea Sediments Impacted by the Deepwater Horizon Oil Spill

NASA Astrophysics Data System (ADS)

Lincoln, S. A.; Freeman, K. H.

2015-12-01

A significant portion of the oil released from the Macondo well after the 2010 Deepwater Horizon (DwH) explosion reached the seafloor (1,2). The transfer of buoyant hydrocarbons from the sea surface and subsurface plumes to depths >1500 m, however, is not well understood. A prominent role for sinking marine snow--small, composite particles composed largely of extracellular polymeric substances exuded by algae and bacteria--has been proposed. Snow particles, rich in carbohydrates, may have sorbed and physically entrained oil from the water column as they sank. Several lines of evidence support this scenario: abundant snow was observed 3-4 weeks after the oil spill (3); oil and dispersants can induce marine snow formation (4); and flocculent material covering deep-sea corals near the DwH site contained biomarkers consistent with Macondo oil (5). To investigate whether the chemically complex marine oil snow leaves a direct sedimentary record, we analyzed carbohydrates at high resolution (2 mm intervals) in sediment cores collected at 4 sites in the northern Gulf of Mexico in 2013 using a modified phenol-sulfuric acid spectrophotometric method. We detected a sharp subsurface peak in carbohydrate concentrations near the Macondo well; we interpret this peak as post-DwH marine snow. Coeval carbohydrate, polycyclic aromatic hydrocarbon, and hopane profiles suggest a clear link between marine snow and Macondo oil components, as documented in a 3-year time-series at one site, and enable preliminary conclusions about the delivery and fate of marine snow components in sediments. We also characterized carbohydrates near the wellhead using fluorescent lectin-binding analyses developed for applications in cell biology. Particle morphologies include collapse structures suggestive of a water column origin. Finally, we explore the extent to which polysaccharide residues detected with selective lectins can be used to determine the provenance of marine snow (e.g., bacterial v. algal). (1) Valentine et al., 2014. PNAS 111, 15906-15911. (2) Romero et al., 2015. PLOS One 10(5): e0128371 (3) Passow et al., ERL 7, 035301. (4) Passow, 2014. Deep-Sea Res. II, http://dx.doi. org/10.1016/j.dsr2.2014.10.001i (5) White et al., 2012. PNAS 109(50), 20303-20308.

Deep drilling in the Chesapeake Bay impact structure - An overview

USGS Publications Warehouse

Gohn, G.S.; Koeberl, C.; Miller, K.G.; Reimold, W.U.

2009-01-01

The late Eocene Chesapeake Bay impact structure lies buried at moderate depths below Chesapeake Bay and surrounding landmasses in southeastern Virginia, USA. Numerous characteristics made this impact structure an inviting target for scientific drilling, including the location of the impact on the Eocene continental shelf, its threelayer target structure, its large size (??85 km diameter), its status as the source of the North American tektite strewn field, its temporal association with other late Eocene terrestrial impacts, its documented effects on the regional groundwater system, and its previously unstudied effects on the deep microbial biosphere. The Chesapeake Bay Impact Structure Deep Drilling Project was designed to drill a deep, continuously cored test hole into the central part of the structure. A project workshop, funding proposals, and the acceptance of those proposals occurred during 2003-2005. Initial drilling funds were provided by the International Continental Scientific Drilling Program (ICDP) and the U.S. Geological Survey (USGS). Supplementary funds were provided by the National Aeronautics and Space Administration (NASA) Science Mission Directorate, ICDP, and USGS. Field operations were conducted at Eyreville Farm, Northampton County, Virginia, by Drilling, Observation, and Sampling of the Earth's Continental Crust (DOSECC) and the project staff during September-December 2005, resulting in two continuously cored, deep holes. The USGS and Rutgers University cored a shallow hole to 140 m in April-May 2006 to complete the recovered section from land surface to 1766 m depth. The recovered section consists of 1322 m of crater materials and 444 m of overlying postimpact Eocene to Pleistocene sediments. The crater section consists of, from base to top: basement-derived blocks of crystalline rocks (215 m); a section of suevite, impact melt rock, lithic impact breccia, and cataclasites (154 m); a thin interval of quartz sand and lithic blocks (26 m); a granite megablock (275 m); and sediment blocks and boulders, polymict, sediment-clast-dominated sedimentary breccias, and a thin upper section of stratified sediments (652 m). The cored postimpact sediments provide insight into the effects of a large continental-margin impact on subsequent coastal-plain sedimentation. This volume contains the first results of multidisciplinary studies of the Eyreville cores and related topics. The volume is divided into these sections: geologic column; borehole geophysical studies; regional geophysical studies; crystalline rocks, impactites, and impact models; sedimentary breccias; postimpact sediments; hydrologic and geothermal studies; and microbiologic studies. ?? 2009 The Geological Society of America.

Quaternary history of the Kiseiba Oasis region, southern Egypt

NASA Astrophysics Data System (ADS)

Maxwell, Ted A.; Haynes, C. Vance; Nicoll, Kathleen; Johnston, Andrew K.; Grant, John A.; Kilani, Ali

2017-12-01

Kiseiba Oasis and depression are located in southern Egypt between the Selima Sand Sheet to the west and the Nile to the east, an important area that hosted Late Cenozoic drainage, Middle Pleistocene lakes, and numerous Paleolithic and Neolithic cultural sites. A synthesis of orbital data, field surveying and near-surface stratigraphy provides new insights into the Quaternary history of this region. Shuttle Imaging Radar data show a complex of fluvial channels that are due to stringers of surficial fluvial lag, subsurface fluvial deposits, and areas of deep alluvium. Three topographic surfaces are described: 1) the Atmur El-Kibeish, above 230 m elevation, which displays a linear pattern of light radar returns, possibly formed from northeast drainage; 2) the Acheulean Surface, at 200 m elevation, that has dark radar patterns resulting from thick alluvium bounded by pebble sand and calcrete strata, and 3) the Kiseiba Surface, below 190 m, that has a complex series of surface and subsurface fluvial and aeolian sediments. Initial drainage from the Early through Middle Pleistocene was to the northeast, which may have lasted through the Last Interglacial. Later reworking of sediments during the Last Glacial Maximum and the Holocene resulted in topographic inversion, with any subsequent local drainage on the Kiseiba Surface to the southwest, towards the Kiseiba Scarp.

Microbial community assembly and evolution in subseafloor sediment.

PubMed

Starnawski, Piotr; Bataillon, Thomas; Ettema, Thijs J G; Jochum, Lara M; Schreiber, Lars; Chen, Xihan; Lever, Mark A; Polz, Martin F; Jørgensen, Bo B; Schramm, Andreas; Kjeldsen, Kasper U

2017-03-14

Bacterial and archaeal communities inhabiting the subsurface seabed live under strong energy limitation and have growth rates that are orders of magnitude slower than laboratory-grown cultures. It is not understood how subsurface microbial communities are assembled and whether populations undergo adaptive evolution or accumulate mutations as a result of impaired DNA repair under such energy-limited conditions. Here we use amplicon sequencing to explore changes of microbial communities during burial and isolation from the surface to the >5,000-y-old subsurface of marine sediment and identify a small core set of mostly uncultured bacteria and archaea that is present throughout the sediment column. These persisting populations constitute a small fraction of the entire community at the surface but become predominant in the subsurface. We followed patterns of genome diversity with depth in four dominant lineages of the persisting populations by mapping metagenomic sequence reads onto single-cell genomes. Nucleotide sequence diversity was uniformly low and did not change with age and depth of the sediment. Likewise, there was no detectable change in mutation rates and efficacy of selection. Our results indicate that subsurface microbial communities predominantly assemble by selective survival of taxa able to persist under extreme energy limitation.

Workshop to develop deep-life continental scientific drilling projects

DOE PAGES

Kieft, T. L.; Onstott, T. C.; Ahonen, L.; ...

2015-05-29

The International Continental Scientific Drilling Program (ICDP) has long espoused studies of deep subsurface life, and has targeted fundamental questions regarding subsurface life, including the following: "(1) What is the extent and diversity of deep microbial life and what are the factors limiting it? (2) What are the types of metabolism/carbon/energy sources and the rates of subsurface activity? (3) How is deep microbial life adapted to subsurface conditions? (4) How do subsurface microbial communities affect energy resources? And (5) how does the deep biosphere interact with the geosphere and atmosphere?" (Horsfield et al., 2014) Many ICDP-sponsored drilling projects have includedmore » a deep-life component; however, to date, not one project has been driven by deep-life goals, in part because geomicrobiologists have been slow to initiate deep biosphere-driven ICDP projects. Therefore, the Deep Carbon Observatory (DCO) recently partnered with the ICDP to sponsor a workshop with the specific aim of gathering potential proponents for deep-life-driven ICDP projects and ideas for candidate drilling sites. Twenty-two participants from nine countries proposed projects and sites that included compressional and extensional tectonic environments, evaporites, hydrocarbon-rich shales, flood basalts, Precambrian shield rocks, subglacial and subpermafrost environments, active volcano–tectonic systems, megafan deltas, and serpentinizing ultramafic environments. The criteria and requirements for successful ICDP applications were presented. Deep-life-specific technical requirements were discussed and it was concluded that, while these procedures require adequate planning, they are entirely compatible with the sampling needs of other disciplines. As a result of this workshop, one drilling workshop proposal on the Basin and Range Physiographic Province (BRPP) has been submitted to the ICDP, and several other drilling project proponents plan to submit proposals for ICDP-sponsored drilling workshops in 2016.« less

Diffusive Transfer of Oxygen From Seamount Basaltic Crust Into Overlying Sediments: an Example From the Clarion-Clipperton Fracture Zone, Equatorial Pacific Ocean

NASA Astrophysics Data System (ADS)

Kasten, S.; Mewes, K.; Mogollón, J.; Picard, A.; Rühlemann, C.; Eisenhauer, A.; Kuhn, T.; Ziebis, W.

2015-12-01

Within the Clarion-Clipperton Fracture Zone (CCFZ) located in the equatorial Pacific Ocean numerous seamounts, with diameters ranging from 3 to 30 km and varying heights above the surrounding seafloor of up to 2500 m, occur throughout the deep-sea plain. There is evidence that these may serve as conduits for low-temperature hydrothermal circulation of seawater through the oceanic crust. During RV SONNE cruise SO205 in April/May 2010 and BIONOD cruise with RV ĹATALANTE in spring 2012 we took piston and gravity cores for geochemical analyses, as well as for high-resolution pore-water oxygen and nutrient measurements. Specifically, we took cores along a transect at three sites, located 400, 700 and 1000 m away from the foot of a 240 m high seamount, called 'Teddy Bare'. At all 3 sites oxygen penetrates the entire sediment column of the organic carbon-poor sediment. More importantly, oxygen concentrations initially decrease with sediment depth but increase again at depths of 3 m and 7 m above the basaltic basement, suggesting an upward diffusion of oxygen from seawater circulating within the seamount crust into the overlying basal sediments. This is the first time this has been shown for the deep subsurface in the Pacific Ocean. Mirroring the oxygen concentrations nitrate concentrations accumulate with sediment depth but decrease towards the basement. Transport-reaction modeling revealed that (1) the diffusive flux of oxygen from the basaltic basement exceeds the oxygen consumption through organic matter oxidation and nitrification in the basal sediments and (2) the nutrient exchange between the sediment and the underlying basaltic crust occurs at orders-of-magnitude lower rates than between the sediment surface and the overlying bottom water. We furthermore show that the upward diffusion of oxygen from the basaltic basement affects the preservation of organic compounds within the oxic sediment column at all 3 sites. Our investigations indicate that an upward diffusion of oxygen from the basalt into the overlying sediment may be a widespread phenomenon in this area of the Pacific Ocean that is characterized by numerous seamounts.

Characterization of geologic deposits in the vicinity of US Ecology, Amargosa Basin, southern Nevada

USGS Publications Warehouse

Taylor, Emily M.

2010-01-01

Multiple approaches have been applied to better understand the characteristics of geologic units exposed at the surface and buried at depth in the vicinity of US Ecology (USE), a low-level commercial waste site in the northern Amargosa Desert, Nevada. Techniques include surficial geologic mapping and interpretation of the subsurface using borehole data. Dated deposits at depth were used to estimate rates of sediment accumulation. The subsurface lithologies have been modeled in three dimensions. Lithologic cross sections have been created from the three-dimensional model and have been compared to resistivity data at the same location. Where deposits appear offset, a fault was suspected. Global Positioning System elevation transects were measured and trenches were excavated to locate a strand of the Carrara Fault. The presence of the fault helps to better understand the shape of the potentiometric surface. These data will be used to better understand the hydrologic parameters controlling the containment of the waste at US Ecology.Quaternary geologic units exposed at the surface, in the vicinity of US Ecology, are derived from the alluvium shed off the adjacent range front and the Amargosa River. These deposits vary from modern to early Pleistocene in age. At depth, heterogeneous sands and gravel occur. Observed in deep trenches and boreholes, the subsurface deposits are characterized as fining-upward sequence of sediment from 5- to 8-meters thick. No volcanic units or fine-grained playa deposits were described in the boreholes to a depth of 200 meters. Based on Infrared Stimulated Luminescence dated core samples, short-term rates of sediment accumulation (<70,000 years) are an average of 2.7 millimeters per year, however, long-term rates (<3,900,000 years) are orders of magnitude less. Resistivity data, when compared to lithologic cross sections, generally are consistent with lithology grain size and probable soil carbonate accumulations. Surface resistivity displays a fining-upward sequence of sediments at the surface with a soil carbonate imprint. Finally, trenching north of US Ecology successfully exposed offset Quaternary deposits on a splay of the Carrara Fault. Holocene deposits do not appear to be faulted, however, a fault zone does intersect middle and late Pleistocene aged units.

Stable, geochemically mediated biospheres in the Deep Mine Microbial Observatory, SD, USA

NASA Astrophysics Data System (ADS)

Osburn, M. R.; Casar, C. P.; Kruger, B.; Flynn, T. M.

2017-12-01

The terrestrial subsurface is a vast reservoir of life, hosting diverse microbial ecosystems with varying levels of connectivity to surface inputs. Understanding long term ecosystem dynamics within the subsurface biosphere is very challenging due to limitations in accessibility, sample availability, and slow microbial growth rates. The establishment of the Deep Mine Microbial Observatory (DeMMO) at the Sanford Underground Research Facility, SD, USA has allowed for bimonthly sampling for nearly two years at six sites spanning 250 to 1500 m below the surface. Here we present a time-resolved analysis of the geomicrobiology of the six DeMMO sites, which have been created from legacy mine boreholes modified to allow for controlled sampling. Our interdisciplinary approach includes analysis of passively draining fracture fluid for aqueous and gas geochemistry, DNA sequencing, microscopy, and isotopic measurements of organic and inorganic substrates. Fluid geochemistry varies significantly between sites, but is relatively stable over time for a given site, even through significant external perturbations such as drilling and installation of permanent sampling devices into the boreholes. The fluid-hosted microbial diversity follows these trends, with consistent populations present at each site through time, even through drilling events. For instance, the shallowest site (DeMMO 1) consistently hosts >30% uncharacterized phyla and >25% Omnitrophica whereas the deepest site (DeMMO 6) is dominated by Firmicutes and Bacterioidetes. Microbial diversity appears to respond to the availability of energy sources such as organic carbon, sulfate, sulfide, hydrogen, and iron. Carbon isotopic measurements reveal closed system behavior with significant recycling of organic carbon into the DIC pool. Together these observations suggest DeMMO hosts isolated subsurface microbial populations adapted to local geochemistry that are stable on yearlong timescales.

Organic carbon accumulation in modern sediments of the Angola basin influenced by the Congo deep-sea fan

NASA Astrophysics Data System (ADS)

Baudin, François; Martinez, Philippe; Dennielou, Bernard; Charlier, Karine; Marsset, Tania; Droz, Laurence; Rabouille, Christophe

2017-08-01

Geochemical data (total organic carbon-TOC content, δ13Corg, C:N, Rock-Eval analyses) were obtained on 150 core tops from the Angola basin, with a special focus on the Congo deep-sea fan. Combined with the previously published data, the resulting dataset (322 stations) shows a good spatial and bathymetric representativeness. TOC content and δ13Corg maps of the Angola basin were generated using this enhanced dataset. The main difference in our map with previously published ones is the high terrestrial organic matter content observed downslope along the active turbidite channel of the Congo deep-sea fan till the distal lobe complex near 5000 m of water-depth. Interpretation of downslope trends in TOC content and organic matter composition indicates that lateral particle transport by turbidity currents is the primary mechanism controlling supply and burial of organic matter in the bathypelagic depths.

Hydrocarbons in Deep-Sea Sediments following the 2010 Deepwater Horizon Blowout in the Northeast Gulf of Mexico.

PubMed

Romero, Isabel C; Schwing, Patrick T; Brooks, Gregg R; Larson, Rebekka A; Hastings, David W; Ellis, Greg; Goddard, Ethan A; Hollander, David J

2015-01-01

The Deepwater Horizon (DWH) spill released 4.9 million barrels of oil into the Gulf of Mexico (GoM) over 87 days. Sediment and water sampling efforts were concentrated SW of the DWH and in coastal areas. Here we present geochemistry data from sediment cores collected in the aftermath of the DWH event from 1000-1500 m water depth in the DeSoto Canyon, NE of the DWH wellhead. Cores were analyzed at high-resolution (at 2 mm and 5 mm intervals) in order to evaluate the concentration, composition and input of hydrocarbons to the seafloor. Specifically, we analyzed total organic carbon (TOC), aliphatic, polycyclic aromatic hydrocarbon (PAHs), and biomarker (hopanes, steranes, diasteranes) compounds to elucidate possible sources and transport pathways for deposition of hydrocarbons. Results showed higher hydrocarbon concentrations during 2010-2011 compared to years prior to 2010. Hydrocarbon inputs in 2010-2011 were composed of a mixture of sources including terrestrial, planktonic, and weathered oil. Our results suggest that after the DWH event, both soluble and highly insoluble hydrocarbons were deposited at enhanced rates in the deep-sea. We proposed two distinct transport pathways of hydrocarbon deposition: 1) sinking of oil-particle aggregates (hydrocarbon-contaminated marine snow and/or suspended particulate material), and 2) advective transport and direct contact of the deep plume with the continental slope surface sediments between 1000-1200 m. Our findings underline the complexity of the depositional event observed in the aftermath of the DWH event in terms of multiple sources, variable concentrations, and spatial (depth-related) variability in the DeSoto Canyon, NE of the DWH wellhead.

Hydrocarbons in Deep-Sea Sediments following the 2010 Deepwater Horizon Blowout in the Northeast Gulf of Mexico

PubMed Central

Romero, Isabel C.; Schwing, Patrick T.; Brooks, Gregg R.; Larson, Rebekka A.; Hastings, David W.; Ellis, Greg; Goddard, Ethan A.; Hollander, David J.

2015-01-01

The Deepwater Horizon (DWH) spill released 4.9 million barrels of oil into the Gulf of Mexico (GoM) over 87 days. Sediment and water sampling efforts were concentrated SW of the DWH and in coastal areas. Here we present geochemistry data from sediment cores collected in the aftermath of the DWH event from 1000 – 1500 m water depth in the DeSoto Canyon, NE of the DWH wellhead. Cores were analyzed at high-resolution (at 2 mm and 5 mm intervals) in order to evaluate the concentration, composition and input of hydrocarbons to the seafloor. Specifically, we analyzed total organic carbon (TOC), aliphatic, polycyclic aromatic hydrocarbon (PAHs), and biomarker (hopanes, steranes, diasteranes) compounds to elucidate possible sources and transport pathways for deposition of hydrocarbons. Results showed higher hydrocarbon concentrations during 2010-2011 compared to years prior to 2010. Hydrocarbon inputs in 2010-2011 were composed of a mixture of sources including terrestrial, planktonic, and weathered oil. Our results suggest that after the DWH event, both soluble and highly insoluble hydrocarbons were deposited at enhanced rates in the deep-sea. We proposed two distinct transport pathways of hydrocarbon deposition: 1) sinking of oil-particle aggregates (hydrocarbon-contaminated marine snow and/or suspended particulate material), and 2) advective transport and direct contact of the deep plume with the continental slope surface sediments between 1000-1200 m. Our findings underline the complexity of the depositional event observed in the aftermath of the DWH event in terms of multiple sources, variable concentrations, and spatial (depth-related) variability in the DeSoto Canyon, NE of the DWH wellhead. PMID:26020923

The hydrological response of a small catchment after the abandonment of terrace cultivation. A study case in northwestern Spain

NASA Astrophysics Data System (ADS)

Llorente-Adán, Jose A.; Lana-Renault, Noemí; Galilea, Ianire; Ruiz-Flaño, Purificacion

2015-04-01

Terrace construction for cultivation results in a complete transformation of the hillslopes to a series of flat sectors and almost vertical steps. This strategy, which involves a redistribution of soils and a re-organization of the drainage network, provides fertile soil over steep slopes, improves infiltration and controls overland flow under conditions of intense rainstorms. In Camero Viejo (north-western Iberian ranges) most of the hillslopes are occupied by terraced fields. During the XXth century, rural population declined and agricultural practices were abandoned. In this area, a small catchment (1.9 km2) was monitored in 2012 for studying how the abandonment of agricultural terraces affect water and sediment transfer from the hillslopes to the channels. Terraces occupy 40% of the catchment and are covered by sparse grass and shrubs. The equipment installed in the catchment registers continuously meteorological data, discharge and water table fluctuations. Data on suspended sediment transport is obtained by means of a rising-stage sampler. Here we present the hydrological results corresponding to the years 2012-13 and 2013-14. The hydrological response of the catchment was moderate (annual runoff coefficient < 0.20), which could be in part explained by the high evapotranspiration rates reported in the area. Lows flows were recorded in summer and autumn, when the water reserves of the catchment were dry, and high flows occurred from January, when the catchment became wetter. The shape of the hydrographs, with slow response times, moderate peakflows and long recession limbs suggested a large contribution of subsurface flow, probably favored by deep and well structured soils in the bench terraces. Soil saturation areas were not observed during the study period, suggesting that soil infiltration processes and subsurface flow are important, and that the drainage system of the terraces is probably well maintained. No suspended sediment has been collected so far, confirming the hypothesis that subsurface flow might be a dominant runoff generation process.

New procedure for recovering extra- and intracellular DNA from marine sediment samples

NASA Astrophysics Data System (ADS)

Alawi, M.; Kallmeyer, J.

2012-12-01

Extracellular DNA (eDNA) is a ubiquitous biological compound in aquatic sediment and soil. Despite major methodological advances, analysis of DNA from sediment is still technically challenging, not just because of the co-elution of inhibitory substances, but also due to co-elution of extracellular DNA, which potentially leads to an overestimate of the actual diversity. Previous studies suggested that eDNA might play an important role in biogeochemical element cycling, horizontal gene transfer and stabilization of biofilm structures. Several protocols based on the precipitation of eDNA e.g. with CTAB and ethanol have already been published. However, using these methods we did not succeed in quantifying very low amounts of eDNA (e.g. <1μg eDNA/g dry wt) in marine sediment even when using DNA carriers like glycogen. Since the recovery of eDNA by precipitation strongly depends on its concentration, these previously published procedures are not adequate for deep biosphere sediment due to the low eDNA content. We have focused on the question whether eDNA could be a source of nitrogen and phosphorus for microbes in the subseafloor biosphere. Therefore we developed a new method for the (semi)-quantitative extraction of eDNA from sediment. The new extraction procedure is based on sequential washing of the sediment to remove simultaneously eDNA and microbial cells without lysing them. After separation of the cells by centrifugation, the eDNA was extracted from the supernatant and purified by adsorption onto a solid phase, followed by removal of the solids and subsequent elution of the pure eDNA. Intracellular DNA (iDNA) was extracted and purified from the cell pellet using a commercial DNA extraction kit. Additional to a very low detection limit and reproducible quantification, this new method allows separation and purification of both extracellular and intracellular DNA to an extent that inhibitors are removed and downstream applications like PCR can be performed. To evaluate the new extraction method two sediments with rather opposing composition were analyzed. Sediment from the South Pacific Gyre, the most oligotrophic oceanic region on earth and organic-rich Baltic Sea sediment (Northern Germany) were processed. Using this new procedure high purity genomic iDNA and eDNA with a molecular size range between 20 bp and 50k bp can be simultaneously recovered even from very oligotrophic sediment with very low cell abundances. The main fraction of recovered eDNA was suitable for downstream applications like PCR and had a molecular size that indicates minimal shearing. Despite about two decades of research many questions about deep subsurface life remain unanswered. The fact that microbes can be found even in deep oligotrophic marine sediment raises the fundamental questions of the types and availability of substrates and their biogeochemical cycling. This is the first study that provides evidence that eDNA is an important potential substrate for microorganisms in the deep biosphere. Also, our results show a link between cell counts and eDNA content, indicating that the eDNA pool in the investigated sediment consist mainly of microbial DNA. Comparative sequence analysis of extracted iDNA and eDNA will provide deeper insights into the origin and turnover of eDNA and the apparent microbial community composition in the deep biosphere.

Mineral-Association and Activity of Bacteria and Archaea in the Deep Subsurface South Pacific Gyre Sediment

NASA Astrophysics Data System (ADS)

Steele, J. A.; Dekas, A. E.; Harrison, B. K.; Morono, Y.; Inagaki, F.; Ziebis, W.; Orphan, V. J.

2012-12-01

Although the subsurface biosphere is now recognized as an important reservoir of life on our planet, until recently the microbial community beneath open-ocean oligotrophic gyres (making up the majority of the seafloor) has just begun to be studied in detail. IODP Expedition 329 and the KNOX-022RR site survey cruise have taken some of the first steps at characterizing the microbial community beneath the South Pacific Gyre, a region with low organic carbon burial rates (10-8 and 10-10 moles C cm-1 yr-1), deep oxygen penetration (sediments are oxidized to the basement), and low prokaryotic cell counts (106 cells cm-3 to <103 cells cm-3). In these sediments, the dominant fraction of organic carbon may be aggregated or adsorbed to minerals, suggesting that microbes that are able to grow on the minerals may create potential "hotspots" of activity. In this study, we performed magnetic separation on oligotrophic sediment samples and examined the bacterial and archaeal communities using 16S rRNA tag sequencing. To determine if the mineral-associated cells were autotrophic and/or utilizing nitrate, we performed long-term (20 month) incubations with 13CO2 and 15NO3- from sediment taken at depths ~2-70 mbsf beneath the oligotrophic gyre and outside of the oligotrophic gyre (IODP Exp. 329 stations U1368-U1371). Subsequently we used the DNA stain SYBR Green I, and CARD-FISH-NanoSIMS to identify cells which were actively taking up the isotopic label. We then used SEM-EDS to identify the mineral particle composition. Preliminary results found the magnetic fraction in oligotrophic sediment (KNOX-022RR station SPG-5) from 1.2-2.6 mbsf showed a greater diversity of both bacteria and archaea. OTUs from Chloroflexi groups SO85 and SAR202 were dominant in the magnetic fraction. Firmicutes, Bacteroidetes, δ-Proteobacteria, Verrucomicrobia, Deferribacteres, WS3, OP10, and OP1 OTUs were found only in the magnetic fraction. Crenarchaeal OTUs from Marine Benthic Group B and Marine Group I (Thaumarchaea) and Euryarchaeal OTUs from Methanomicrobia and Thermococcus groups were found in the magnetic fraction with Marine Group I Crenarchaea showing the highest archaeal abundance. The higher diversity in the magnetic fraction suggests that bacteria and archaea associated with Fe-rich or Mn-rich minerals may be able to exploit a wider array of niches. Comparing sediment from within and outside the gyre, the more productive sediments had greater total cell numbers; however, we observed an increase in attached cells in the relatively Fe and P-rich samples (the heavy fraction) in the oligotrophic sediments (IODP Exp. 329 station U1368 and KNOX-022RR station SPG-6), suggesting a possible preference for attachment to Fe and P-rich particles.

An in vivo Investigation into Temperature-Controlled Stratification of Sub-Seafloor Populations

NASA Astrophysics Data System (ADS)

McClelland, H. L. O.; Morono, Y.; Fike, D. A.; Bradley, A. S.

2017-12-01

The deep subsurface is characterized by a paucity of carbon substrates and biologically exploitable chemical potential energy. These metabolic challenges can be exacerbated by high temperatures, due to increased costs of cellular maintenance. Though sparse, microbial life persists in such environments, however, the degree to which temperature gradients result in the stratification extremophilic sub-seafloor populations is poorly understood. During Expedition 370, we established a matrix of incubation experiments with sediment samples taken from 8 depths corresponding to in situ temperatures of approximately 37, 50, 60, 70, 80, 90, 100 and 110°C, which were incubated in oxygen-free, acetate- and sulfate- supplemented, artificial seawater at temperatures of 37, 50, 60, 70 and 80°C. Substrates include large isotopic labels. Following separation from the sediment, cells were analyzed using SIMS, allowing estimates of biomass synthesis rates. We are interested in discussing potential future experiments and collaborations using this resource.

Temporal Dynamics and Decay of Putatively Allochthonous and Autochthonous Viral Genotypes in Contrasting Freshwater Lakes

PubMed Central

Barbosa, Jorge G.; Brown, Julia M.; Donelan, Ryan P.; Eaglesham, James B.; Eggleston, Erin M.; LaBarre, Brenna A.

2012-01-01

Aquatic viruses play important roles in the biogeochemistry and ecology of lacustrine ecosystems; however, their composition, dynamics, and interactions with viruses of terrestrial origin are less extensively studied. We used a viral shotgun metagenomic approach to elucidate candidate autochthonous (i.e., produced within the lake) and allochthonous (i.e., washed in from other habitats) viral genotypes for a comparative study of their dynamics in lake waters. Based on shotgun metagenomes prepared from catchment soil and freshwater samples from two contrasting lakes (Cayuga Lake and Fayetteville Green Lake), we selected two putatively autochthonous viral genotypes (phycodnaviruses likely infecting algae and cyanomyoviruses likely infecting picocyanobacteria) and two putatively allochthonous viral genotypes (geminiviruses likely infecting terrestrial plants and circoviruses infecting unknown hosts but common in soil libraries) for analysis by genotype-specific quantitative PCR (TaqMan) applied to DNAs from viruses in the viral size fraction of lake plankton, i.e., 0.2 μm > virus > 0.02 μm. The abundance of autochthonous genotypes largely reflected expected host abundance, while the abundance of allochthonous genotypes corresponded with rainfall and storm events in the respective catchments, suggesting that viruses with these genotypes may have been transported to the lake in runoff. The decay rates of allochthonous and autochthonous genotypes, assessed in incubations where all potential hosts were killed, were generally lower (0.13 to 1.50% h−1) than those reported for marine virioplankton but similar to those for freshwater virioplankton. Both allochthonous and autochthonous viral genotypes were detected at higher concentrations in subsurface sediments than at the water-sediment interface. Our data indicate that putatively allochthonous viruses are present in lake plankton and sediments, where their temporal dynamics reflect active transport to the lake during hydrological events and then decay once there. PMID:22773646

Long-term fluid expulsion revealed by carbonate crusts and pockmarks connected to subsurface gas anomalies and palaeo-channels in the central North Sea

NASA Astrophysics Data System (ADS)

Chand, Shyam; Crémière, Antoine; Lepland, Aivo; Thorsnes, Terje; Brunstad, Harald; Stoddart, Daniel

2017-06-01

Gas seepage through the seafloor into the water column is inferred based on acoustic mapping, video observations and geochemical analyses at multiple locations in the Viking Graben and Utsira High areas of the central North Sea. Flares in the Viking Graben occur both inside and along the periphery of a submarine melt water channel where pockmarks (up to 500 m in diameter) and methane-derived carbonate crusts are found on the seafloor, indicating focussing of fluid flow in the vicinity of the channel. The flares can be related to gas accumulations close to the seafloor as well as in Quaternary and deeper strata, observed as high-amplitude reflections on seismic data. Many palaeo-channels, which act as accumulation zones, are observed in the subsurface of both the Viking Graben and Utsira High areas. The deeper origin of gas is partially supported by results of isotope analyses of headspace gas collected from sediment samples of the Viking Graben, which show a mixed microbial/thermogenic origin whereas isotope data on free seeping gas in the Viking Graben indicate a predominantly microbial origin. Based on these lines of evidence, a structure-controlled fluid flow model is proposed whereby hydrocarbons migrate in limited amount from deep thermogenic reservoirs along faults, and these deep fluids are strongly diluted by microbial methane. Moreover, the existence of subsurface pockmarks at several stratigraphic levels indicates long-term fluid flow, interpreted to be caused by gas hydrate destabilisation and stress-related high overpressures.

Concentrations of inorganic arsenic in groundwater, agricultural soils and subsurface sediments from the middle Gangetic plain of Bihar, India.

PubMed

Kumar, Manoj; Ramanathan, A L; Rahman, Mohammad Mahmudur; Naidu, Ravi

2016-12-15

Concentrations of inorganic forms [arsenite, As(III) and arsenate, As(V) of arsenic (As) present in groundwater, agricultural soils and subsurface sediments located in the middle Gangetic plain of Bihar, India were determined. Approximately 73% of the groundwater samples (n=19) show As(III) as the dominant species while 27% reveals As(V) was the dominant species. The concentration of As(III) in agricultural soil samples varies from not detectable to 40μg/kg and As(V) was observed as the major species (ranging from 1050 to 6835μg/kg) while the total As concentration varied from 3528 to 14,690μg/kg. Total extracted concentration of As was higher in the subsurface sediments (range 9119-20,056μg/kg in Methrapur and 4788-19,681μg/kg in Harail Chapar) than the agricultural soil, indicating the subsurface sediment as a source of As. Results of X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) revealed the presence of hematite and goethite throughout the vertical section below while magnetite was observed only in the upper oxidized layer at Methrapur and Harail Chapar. Alteration of Fe-oxides and presence of fibrous goethite indicating presence of diagenetic sediment. Siderite plays a crucial role as sinks to the As in subsurface sediments. The study also concluded that decomposition of organic matter present in dark and grey sections promote the redox conditions and trigger mobilization of As into groundwater. Copyright © 2016 Elsevier B.V. All rights reserved.

Microbial Communities and Organic Matter Composition in Surface and Subsurface Sediments of the Helgoland Mud Area, North Sea

PubMed Central

Oni, Oluwatobi E.; Schmidt, Frauke; Miyatake, Tetsuro; Kasten, Sabine; Witt, Matthias; Hinrichs, Kai-Uwe; Friedrich, Michael W.

2015-01-01

The role of microorganisms in the cycling of sedimentary organic carbon is a crucial one. To better understand relationships between molecular composition of a potentially bioavailable fraction of organic matter and microbial populations, bacterial and archaeal communities were characterized using pyrosequencing-based 16S rRNA gene analysis in surface (top 30 cm) and subsurface/deeper sediments (30–530 cm) of the Helgoland mud area, North Sea. Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) was used to characterize a potentially bioavailable organic matter fraction (hot-water extractable organic matter, WE-OM). Algal polymer-associated microbial populations such as members of the Gammaproteobacteria, Bacteroidetes, and Verrucomicrobia were dominant in surface sediments while members of the Chloroflexi (Dehalococcoidales and candidate order GIF9) and Miscellaneous Crenarchaeota Groups (MCG), both of which are linked to degradation of more recalcitrant, aromatic compounds and detrital proteins, were dominant in subsurface sediments. Microbial populations dominant in subsurface sediments (Chloroflexi, members of MCG, and Thermoplasmata) showed strong correlations to total organic carbon (TOC) content. Changes of WE-OM with sediment depth reveal molecular transformations from oxygen-rich [high oxygen to carbon (O/C), low hydrogen to carbon (H/C) ratios] aromatic compounds and highly unsaturated compounds toward compounds with lower O/C and higher H/C ratios. The observed molecular changes were most pronounced in organic compounds containing only CHO atoms. Our data thus, highlights classes of sedimentary organic compounds that may serve as microbial energy sources in methanic marine subsurface environments. PMID:26635758

Effect of Submarine Groundwater Discharge on Relict Arctic Submarine Permafrost and Gas Hydrate

NASA Astrophysics Data System (ADS)

Frederick, J. M.; Buffett, B. A.

2014-12-01

Permafrost-associated gas hydrate deposits exist at shallow depths within the sediments of the circum-Arctic continental shelves. Degradation of this shallow water reservoir has the potential to release large quantities of methane gas directly to the atmosphere. Gas hydrate stability and the permeability of the shelf sediments to gas migration is closely linked with submarine permafrost. Submarine permafrost extent depends on several factors, such as the lithology, sea level variations, mean annual air temperature, ocean bottom water temperature, geothermal heat flux, and the salinity of the pore water. The salinity of the pore water is especially relevant because it partially controls the freezing point for both ice and gas hydrate. Measurements of deep pore water salinity are few and far between, but show that deep off-shore sediments are fresh. Deep freshening has been attributed to large-scale topographically-driven submarine groundwater discharge, which introduces fresh terrestrial groundwater into deep marine sediments. We investigate the role of submarine ground water discharge on the salinity field and its effects on the seaward extent of relict submarine permafrost and gas hydrate stability on the Arctic shelf with a 2D shelf-scale model based on the finite volume method. The model tracks the evolution of the temperature, salinity, and pressure fields given imposed boundary conditions, with latent heat of water ice and hydrate formation included. The permeability structure of the sediments is coupled to changes in permafrost. Results show that pore fluid is strongly influenced by the permeability variations imposed by the overlying permafrost layer. Groundwater discharge tends to travel horizontally off-shore beneath the permafrost layer and the freshwater-saltwater interface location displays long timescale transient behavior that is dependent on the groundwater discharge strength. The seaward permafrost extent is in turn strongly influenced by the salinity field and location of the freshwater-saltwater transition. Our results suggest that the role of salt transport and its effect on permafrost evolution can provide context for the interpretation of recent permafrost maps and methane observations in the Arctic.

High-resolution seismic-reflection images across the ICDP-USGS Eyreville deep drilling site, Chesapeake Bay impact structure

USGS Publications Warehouse

Powars, David S.; Catchings, Rufus D.; Goldman, Mark R.; Gohn, Gregory S.; Horton, J. Wright; Edwards, Lucy E.; Rymer, Michael J.; Gandhok, Gini

2009-01-01

The U.S. Geological Survey (USGS) acquired two 1.4-km-long, high-resolution (~5 m vertical resolution) seismic-reflection lines in 2006 that cross near the International Continental Scientific Drilling Program (ICDP)-USGS Eyreville deep drilling site located above the late Eocene Chesapeake Bay impact structure in Virginia, USA. Five-meter spacing of seismic sources and geophones produced high-resolution images of the subsurface adjacent to the 1766-m-depth Eyreville core holes. Analysis of these lines, in the context of the core hole stratigraphy, shows that moderate-amplitude, discontinuous, dipping reflections below ~527 m correlate with a variety of Chesapeake Bay impact structure sediment and rock breccias recovered in the cores. High-amplitude, continuous, subhorizontal reflections above ~527 m depth correlate with the uppermost part of the Chesapeake Bay impact structure crater-fill sediments and postimpact Eocene to Pleistocene sediments. Reflections with ~20-30 m of relief in the uppermost part of the crater-fill and lowermost part of the postimpact section suggest differential compaction of the crater-fill materials during early postimpact time. The top of the crater-fill section also shows ~20 m of relief that appears to represent an original synimpact surface. Truncation surfaces, locally dipping reflections, and depth variations in reflection amplitudes generally correlate with the lithostrati-graphic and sequence-stratigraphic units and contacts in the core. Seismic images show apparent postimpact paleochannels that include the first possible Miocene paleochannels in the Mid-Atlantic Coastal Plain. Broad downwarping in the postim-pact section unrelated to structures in the crater fill indicates postimpact sediment compaction.

Microbial habitability of Europa sustained by radioactive sources.

PubMed

Altair, Thiago; de Avellar, Marcio G B; Rodrigues, Fabio; Galante, Douglas

2018-01-10

There is an increasing interest in the icy moons of the Solar System due to their potential habitability and as targets for future exploratory missions, which include astrobiological goals. Several studies have reported new results describing the details of these moons' geological settings; however, there is still a lack of information regarding the deep subsurface environment of the moons. The purpose of this article is to evaluate the microbial habitability of Europa constrained by terrestrial analogue environments and sustained by radioactive energy provided by natural unstable isotopes. The geological scenarios are based on known deep environments on Earth, and the bacterial ecosystem is based on a sulfate-reducing bacterial ecosystem found 2.8 km below the surface in a basin in South Africa. The results show the possibility of maintaining the modeled ecosystem based on the proposed scenarios and provides directions for future models and exploration missions for a more complete evaluation of the habitability of Europa and of icy moons in general.

New Frontiers for Deep Fluids and Geobiology Research in the World's Oldest Rocks

NASA Astrophysics Data System (ADS)

Sherwood Lollar, B.; Li, L.; Wing, B. A.; Warr, O.; Sica, C. S.; Lollar, G. S.; Sutcliffe, N. C.; Telling, J.; Ballentine, C. J.; Giunta, T.; McDermott, J. M.

2016-12-01

Discovery of new environmental systems that facilitate investigation of biodiversity, microbial metabolism, life's adaptation to extreme conditions, and limits to life, have expanded our conception of Earth's habitability and informed search strategies for life elsewhere in the solar system. While chemolithotrophic microbial ecosystems in the marine biosphere have been investigated for decades, the geobiology of terrestrial systems is undergoing a recent expansion, in particular to include the > 70% of the continental lithosphere comprised of Precambrian rocks - the oldest rocks on Earth. Underground research laboratories and mines worldwide provide access to the deep subsurface in Precambrian settings, and targets for investigation of extant microbial ecosystems. Kidd Creek Mine located in Tmmins Ontario on the Canadian Shield is an iconic site. Investigation of fracture fluids here to 3 km revealed H2 production via radiolysis and serpentinization [1]; production of methane and higher hydrocarbons via abiotic organic synthesis [2]; and fracture fluids with mean residence times on the order of a billion years [3]. Recently, investigation of the sulfur cycle in these fluids has revealed a mass independent sulfur isotope signature in the dissolved sulfate, whereby oxidants from radiolysis oxidize Archean sulfide minerals, providing a mechanism to supply both electron donors (H2) and electron acceptors (sulfate) that could fuel a deep microbial biosphere [4]. Recent MPNs results demonstrate the presence of sulfate-reducing bacteria in these waters in the present day. Beginning in 2016 the deep levels at this site are providing access to international teams of researchers to collaborate with the University of Toronto in a multi-year program to characterize the deep CHONS cycles, as terrestrial geobiology continues to expand our understanding of the habitability of the Earth. [1] Sherwood Lollar et al. (2014) Nature 516,379-382. [2] Sherwood Lollar et al. (2002) Nature 416,522-524. [3] Holland et al. (2013) Nature 497,357-360. [4] Li et al. (2016) Nature Communications in press.

The down canyon evolution of submarine sediment density flows

NASA Astrophysics Data System (ADS)

Parsons, D. R.; Barry, J.; Clare, M. A.; Cartigny, M.; Chaffey, M. R.; Gales, J. A.; Gwiazda, R.; Maier, K. L.; McGann, M.; Paull, C. K.; O'Reilly, T. C.; Rosenberger, K. J.; Simmons, S.; Sumner, E. J.; Talling, P.; Xu, J.

2017-12-01

Submarine density flows, known as turbidity currents, transfer globally significant volumes of terrestrial and shelf sediments, organic carbon, nutrients and fresher-water into the deep ocean. Understanding such flows has wide implications for global organic carbon cycling, the functioning of deep-sea ecosystems, seabed infrastructure hazard assessments, and interpreting geological archives of Earth history. Only river systems transport comparable volumes of sediment over such large areas of the globe. Despite their clear importance, there are remarkably few direct measurements of these oceanic turbidity currents in action. Here we present results from the multi-institution Coordinated Canyon Experiment (CCE) which deployed multiple moorings along the axis of Monterey Canyon (offshore California). An array of six moorings, with downward looking acoustic Doppler current profilers (ADCP) were positioned along the canyon axis from 290 m to 1850 m water depth. The ADCPs reveal the internal flow structure of submarine density flows at each site. We use a novel inversion method to reconstruct the suspended sediment concentration and flow stratification field during each event. Together the six moorings provide the first ever views of the internal structural evolution of turbidity current events as they evolve down system. Across the total 18-month period of deployment at least 15 submarine sediment density flows were measured with velocities up to 8.1 m/sec, with three of these flows extending 50 kms down the canyon beyond the 1850 m water depth mooring. We use these novel data to highlight the controls on ignition, interval structure and collapse of individual events and discuss the implications for the functioning and deposits produced by these enigmatic flows.

Subsurface microbial habitats on Mars

NASA Technical Reports Server (NTRS)

Boston, P. J.; Mckay, C. P.

1991-01-01

We developed scenarios for shallow and deep subsurface cryptic niches for microbial life on Mars. Such habitats could have considerably prolonged the persistence of life on Mars as surface conditions became increasingly inhospitable. The scenarios rely on geothermal hot spots existing below the near or deep subsurface of Mars. Recent advances in the comparatively new field of deep subsurface microbiology have revealed previously unsuspected rich aerobic and anaerobic microbal communities far below the surface of the Earth. Such habitats, protected from the grim surface conditions on Mars, could receive warmth from below and maintain water in its liquid state. In addition, geothermally or volcanically reduced gases percolating from below through a microbiologically active zone could provide the reducing power needed for a closed or semi-closed microbial ecosystem to thrive.

ICDP project DeepCHALLA: reconstructing East African climate change and environmental history over the past 250,000 years

NASA Astrophysics Data System (ADS)

Verschuren, Dirk; Van Daele, Maarten; Wolff, Christian; Waldmann, Nicolas; Meyer, Inka; Ombori, Titus; Peterse, Francien; O'Grady, Ryan; Schnurrenberger, Doug; Olago, Daniel

2017-04-01

Sediments on the bottom of Lake Challa, a 92-meter deep crater lake on the border of Kenya and Tanzania near Mt. Kilimanjaro, contain a uniquely long and continuous record of past climate and environmental change. The near-equatorial location and exceptional quality of this natural archive provide great opportunities to study tropical climate variability at both short (inter-annual to decadal) and long (glacial-interglacial) time scales; and the influence of this climate variability on the region's freshwater resources, the functioning of terrestrial ecosystems, and the history of the East African landscape in which modern humans (our species, Homo sapiens) evolved and have lived ever since. Supported in part by the International Continental Scientific Drilling Programme (ICDP), the DeepCHALLA project has now recovered the sediment record of Lake Challa down to 214.8 meter below the lake floor, with almost certain 100% cover of the uppermost 121.3 meter (ca.150,000 year BP to present) and estimated 85% cover over the lower part of the sequence, down to the lowermost distinct reflector in the available seismic stratigraphy. This reflector represents a 2 meter thick layer of volcanic sand and silt deposited ca.250,000 years ago, and overlies still older silty lacustrine clays deposited during early lake development. Down-hole logging produced continuous profiles of in-situ sediment composition that confer an absolute depth scale to both the recovered cores and their three-dimensional representation in seismic stratigraphy. As readily observed through the transparent core liners, Lake Challa sediments are finely laminated throughout most of the recovered sequence. Combined with the great time span, the exquisite temporal resolution of these sediments promises to greatly increase our understanding of tropical climate and ecosystem dynamics, and create a long-awaited equatorial counterpart to the high-latitude climate records extracted from the ice sheets of Greenland and Antarctica.

Miocene climate variations in the Moesian Platform sediments based on sedimentology and biomarkers

NASA Astrophysics Data System (ADS)

Butiseaca, Geanina; Vasiliev, Iuliana; Rabagia, Traian; Dinu, Corneliu; Mulch, Andreas

2017-04-01

During the Miocene the Moesian Platform (southern Romania and northern Bulgaria) had a complicated flexural behavior due to the mobility of the nearby orogens. The different behavior induced varying sediment charges, sediment distribution and sediment types. The northern part of the study area (on which the Dacian Basin is overlaid) is characterized by siliciclastic units with dominantly deep facieses, while the southern part is characterized by carbonate production in shallower basin waters. Since the Miocene, the Dacian and Black Sea basins have been highly sensitive to fluctuations in the hydrological cycle. To establish the dynamic evolution of the basin and the climate variations during the Miocene, we have sampled both northern and southern margins of the basin. To discriminate between the tectonic imprint and the eustatic influence over the sedimentation rate we have chosen a multidisciplinary approach including sedimentology, tectonics and organic geochemistry based reconstructions. The sedimentary succession is interrupted by few unconformities correspondent with the main phases of orogeny (in the Carpathian Foredeep) while the southern part seems to have been exposed more often expressed in the geological record by a higher number of unconformities and paleo-soils levels. The n-alkanes distribution recovered from the lipids extracted from the sedimentary rocks indicates a mixture of terrestrial and marine input in the northern, Romanian, closer to Carpathians, part of the Dacian Basin. Surprisingly, the southern, Bulgarian side, showed a more predominant terrestrial input (with higher contribution of the long chain n-alkanes) at least for the Sarmatian (arround 10 Ma). The estimated paleotemperatures based on branched GDGT's indicate much warmer conditions than present day, up to a value of 20 C mean annual temperatures. We will further investigate the paleoenvironmental changes during the latest Miocene of the Dacian basin, using the biomarker approach on the organic biomarkers.

Paleoceanographic history of the Lower Bengal Fan during the last glacial cycle - IODP Expedition 354

NASA Astrophysics Data System (ADS)

Dekens, P. S.; Weber, M. E.; Lantzsch, H.; Das, S. K.; Williams, T.; Adhikari, R. R.; Jia, G.; Fox, L. R.; Ge, J.; Manoj, M. C.; Savian, J. F.; Reilly, B. T.; Selkin, P. A.; Meynadier, L.; Spiess, V.; France-Lanord, C.; Sharma, B.

2015-12-01

IODP Expedition 354 drilled a ~320 km long transect of seven sites on the Lower Bengal Fan at 8o N in the Northern Indian Ocean. The sediments cores recovered record a complex relationship between turbiditic and hemipelagic environments. This variability offers a unique opportunity to link our understanding of tectonic and terrestrial processes with climate and oceanography. With the exception the westernmost Site U1454, all sites show a several meter thick, hemipelagic top layer, usually representing Late Quaternary sediment. We present physical, geochemical and stable isotopic properties of this interval to establish a time frame and assess the paleoceanographic development of the region during the last glacial cycle. We sampled Site U1452C-1H continuously for the uppermost 480 cm of hemipelagic sediment in 2-cm increments. Preliminary results indicate the Toba Ash 1 (0.74 ka) is a distinct time marker in all physical properties. Furthermore, wet-bulk density as well as color reflectance b* (the red-green component) and L* (the lightness) show a dominant precession cyclicity. Hence, we are able to provide an insolation-tuned chronology for the last 200 ka (MIS1 - 7) as a preliminary age model. These records agree well with d18O records retrieved from Chinese caves. We will present a preliminary paleoceanographic proxy data to reconstruct sea-surface temperature (SST), sea-surface salinity (SSS), ice volume, marine biological productivity, nutrient supply, and deep-water circulation. These oceanographic and climate conditions are linked to changes in monsoonal strength and terrestrial input using sedimentary proxies to reconstruct chemical weathering and sediment sources and transport time. This work addresses one of the primary cruise objectives - linking monsoon variability, regional and global climate, and Bay of Bengal sediment deposition.

Erosion and deposition on the eastern margin of the Bermuda Rise in the late Quaternary

NASA Astrophysics Data System (ADS)

McCave, I. N.; Hollister, C. D.; Laine, E. P.; Lonsdale, P. F.; Richardson, M. J.

1982-05-01

A near-bottom survey has been made on the Eastward Scarp (32°50'N, 57°30'W) of the Bermuda Rise, which rises 1150 m above the 5500-m deep Sohm Abyssal Plain in the western North Atlantic. The survey reveals evidence of erosion and deposition at present and in the late Quaternary by the deeper levels of the westward flowing Gulf Stream Return Flow. Four distinct regions of increasing bed gradient show increasing sediment smoothing and scour in the transition from plateau to abyssal plain. Bedforms observed are current crescents, crag and tail, triangular ripples, elongate mounds, transverse mud ripples, lineations, and furrows ranging from 10 to 1 m or less in depth, decreasing generally with bed gradient. Measured near-bottom current speeds are up to 20 cm s -1. Temperature structure on the lower, steep, slopes suggests that detachment of bottom mixed layers may occur there. Extensive net erosion appears to be confined to the lower steep slopes of the scarp. Reflection profiles (4 kHz) show that there has been erosion in areas thinly draped with recent sediments and in areas that show development of small scarps. The distribution of subsurface acoustic characteristics of the region corresponds broadly to the areas characterized by bed gradient and distinct sedimentation conditions. Subsurface hyperbolae, possibly caused by buried furrows, show furrow persistence through several tens of metres of deposition. Erosion occurs up to the top of the scarp during episodes of presumed stronger currents, which may correspond with intensified circulation during glacials.

In-Well Sediment Incubators to Evaluate Microbial Community Stability and Dynamics following Bioimmobilization of Uranium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baldwin, Brett R.; Peacock, Aaron D.; Gan, M.

2009-09-23

An in-situ incubation device (ISI) was developed in order to investigate the stability and dynamics of sediment associated microbial communities to prevailing subsurface oxidizing or reducing conditions. Here we describe the use of these devices at the Old Rifle Uranium Mill Tailings Remedial Action (UMTRA) site. During the 7 month deployment oxidized Rifle aquifer background sediments (RABS) were deployed in previously biostimulated wells under iron reducing conditions, cell densities of known iron reducing bacteria including Geobacteraceae increased significantly showing the microbial community response to local subsurface conditions. PLFA profiles of RABS following in situ deployment were strikingly similar to thosemore » of adjacent sediment cores suggesting ISI results could be extrapolated to the native material of the test plots. Results for ISI deployed reduced sediments showed only slight changes in community composition and pointed toward the ability of the ISIs to monitor microbial community stability and response to subsurface conditions.« less

Evidence for sub-lacustrine volcanic activity in Lake Bolsena (central Italy) revealed by high resolution seismic data sets

NASA Astrophysics Data System (ADS)

Lindhorst, Katja; Krastel, Sebastian; Wagner, Bernd; Schuerer, Anke

2017-06-01

The Bolsena caldera that formed between 0.6 and 0.2 Ma has a well preserved structural rim, which makes it an ideal site to study the tectonic and volcanic evolution of calderas. However, the main area is covered by a 150 m deep lake which makes it rather difficult to investigate the subsurface structure directly. To overcome this problem new high resolution hydro-acoustic surveys using a multichannel reflection seismic system and a sediment echo-sounder system were conducted in September 2012. As space was limited we used a rowing boat towed by a rubber boat to handle a 36 m long and 24 channel streamer to receive seismic reflections produced using a Mini GI-Gun (0.25 l). The subsurface structure of Lake Bolsena was imaged up to a sediment depth of 190 m, which is estimated to have filled over a period of 333 kyrs. However, massive pyroclastic flow deposits found in the deeper parts of the basin indicate an initial infill of volcanic deposits from two adjacent younger calderas, the Latera (W) and Montefiascone (SE) calderas. Our data suggest that the caldera has a long history of active volcanism, because the lacustrine sediments show post-sedimentary influences of geothermal fluids. We mapped several mound structures at various stratigraphic depths. Two volcanic structures outcrop at the modern lake surface implying recent activity. One of these structures is hardly covered by sediments and has a crater-like feature in its summit. The other structure shows a pockmark-like depression on top. Another observable feature is a partially sediment filled crater located in the western part of the lake which further implies the existence of a magma chamber located beneath the Bolsena caldera. Since the late Pleistocene and Holocene, the sedimentation was mainly hemipelagic evidenced by a sediment drape of up to 10 m thick sediment drape on the uppermost sediments. Beneath the drape we found evidence for a distal tephra layer likely related to an explosive eruption from the Campanian Volcanic Province occurring as the Neapolitan Yellow Tuff. Our new geophysical data set is a valuable record with a potential to constrain the sedimentary and volcanic evolution of the Vulsini Volcanic District in areas that have not been assessed previously due to logistical challenges of conducting surveys in water-filled settings.

Sediment Transport Capacity of Turbidity Currents: from Microscale to Geological Scale.

NASA Astrophysics Data System (ADS)

Eggenhuisen, J. T.; Tilston, M.; Cartigny, M.; Pohl, F.; de Leeuw, J.; van der Grind, G. J.

2016-12-01

A big question in sedimentology concerns the magnitude of fluxes of sediment particles, solute matter and dissolved gasses from shallow marine waters to deep basins by turbidity current flow. Here we establish sediment transport capacity of turbidity current flow on three levels. The most elementary level is set by the maximum amount of sediment that can be contained at the base of turbidity currents without causing complete extinction of boundary layer turbulence. The second level concerns the capacity in a vertical column within turbidity currents. The third level involves the amount of sediment that can be transported in turbidite systems on geological timescales. The capacity parameter Γ compares turbulent forces near the boundary of a turbulent suspension to gravity and buoyancy forces acting on suspended particles. The condition of Γ>1 coincides with complete suppression of coherent boundary layer turbulence in Direct Numerical Simulations of sediment-laden turbulent flow. Γ=1 coincides with the upper limit of observed suspended particle concentrations in flume and field measurements. Γ is grainsize independent, yet capacity of the full vertical structure of turbidity currents becomes grainsize dependent. This is due to the appearance of grainsize dependent vertical motions within turbulence as a primary control on the shape of the vertical concentration profile. We illustrate this dependence with experiments and theory and conclude that capacity depends on the competence of prevailing turbulence to suspend particle sizes. The concepts of capacity and competence are thus tangled. Finally, the capacity of turbidity current flow structure is coupled to geological constraints on recurrence times, channel and lobe life cycles, and allogenic forcing on system activity to arrive at system scale sediment transport capacity. We demonstrate a simple model that uses the fundamental process insight described above to estimate geological sediment budgets from architectural information. These predictions are tied to existing S2S analyses to constrain submarine channel and fan dimensions in ancient and subsurface systems. Predictions of sediment budgets in deep marine systems rely on integration of fundamental issues in turbulent particle suspension into geological models of turbidite systems.

Meteoric 10Be/9Be ratios in marine sedimentary records: Deciphering the mixing between their marine and terrestrial sources and influence of costal trace metal fluxes

NASA Astrophysics Data System (ADS)

Wittmann, H.; von Blanckenburg, F.; Mohtadi, M.; Christl, M.; Bernhardt, A.

2017-12-01

Meteoric 10Be to stable 9Be ratios combine a cosmogenic nuclide produced in the atmosphere at a rate known from reconstructions of magnetic field strength with a stable isotope that records the present and past continental weathering and erosion flux. In seawater, the 10Be/9Be ratio provides important information on metal release from bottom sediments, called boundary exchange, and the oceanic mixing of reactive trace metals due to the inherently different sources of the two isotopes. When measured in the authigenic phase of marine sediments, the 10Be/9Be ratio allows deriving the feedbacks between erosion, weathering, and climate in the geologic past. At an ocean margin site 37°S offshore Chile, we use the 10Be/9Be ratio to trace changes in terrestrial particulate composition due to exchange with seawater. We analyzed the reactive (sequentially extracted) phase of marine surface sediments along a coast-perpendicular transect, and compared to samples from their riverine source. We find evidence for growth of authigenic rims through co-precipitation, not via reversible adsorption, that incorporate an open ocean 10Be/9Be signature from a deep water source only 30 km from the coast, thereby overprinting terrestrial riverine 10Be/9Be signatures. We show that the measured 10Be/9Be ratios in marine sediments comprise a mixture between seawater-derived and riverine-sourced phases. As 10Be/9Be ratios increase due to exchange with seawater, particulate-bound Fe concentrations increase, which we attribute to release of Fe-rich pore waters during boundary exchange in the sediment. The implications for the use of 10Be/9Be in sedimentary records for paleo-denudation flux reconstructions are that in coast-proximal sites that are neither affected by deeper water nor by narrow boundary currents, the authigenic record will be a direct recorder of terrigenous denudation of the adjacent river catchments. Hence archive location and past oceanic circulation have to be accounted for when reconstructing continental erosion and weathering, and only at open ocean sites that are fully reset by seawater global signals can be reconstructed.

Belowground rhizomes in paleosols: The hidden half of an Early Devonian vascular plant

NASA Astrophysics Data System (ADS)

Xue, Jinzhuang; Deng, Zhenzhen; Huang, Pu; Huang, Kangjun; Benton, Michael J.; Cui, Ying; Wang, Deming; Liu, Jianbo; Shen, Bing; Basinger, James F.; Hao, Shougang

2016-08-01

The colonization of terrestrial environments by rooted vascular plants had far-reaching impacts on the Earth system. However, the belowground structures of early vascular plants are rarely documented, and thus the plant-soil interactions in early terrestrial ecosystems are poorly understood. Here we report the earliest rooted paleosols (fossil soils) in Asia from Early Devonian deposits of Yunnan, China. Plant traces are extensive within the soil and occur as complex network-like structures, which are interpreted as representing long-lived, belowground rhizomes of the basal lycopsid Drepanophycus. The rhizomes produced large clones and helped the plant survive frequent sediment burial in well-drained soils within a seasonal wet-dry climate zone. Rhizome networks contributed to the accumulation and pedogenesis of floodplain sediments and increased the soil stabilizing effects of early plants. Predating the appearance of trees with deep roots in the Middle Devonian, plant rhizomes have long functioned in the belowground soil ecosystem. This study presents strong, direct evidence for plant-soil interactions at an early stage of vascular plant radiation. Soil stabilization by complex rhizome systems was apparently widespread, and contributed to landscape modification at an earlier time than had been appreciated.

Belowground rhizomes in paleosols: The hidden half of an Early Devonian vascular plant.

PubMed

Xue, Jinzhuang; Deng, Zhenzhen; Huang, Pu; Huang, Kangjun; Benton, Michael J; Cui, Ying; Wang, Deming; Liu, Jianbo; Shen, Bing; Basinger, James F; Hao, Shougang

2016-08-23

The colonization of terrestrial environments by rooted vascular plants had far-reaching impacts on the Earth system. However, the belowground structures of early vascular plants are rarely documented, and thus the plant-soil interactions in early terrestrial ecosystems are poorly understood. Here we report the earliest rooted paleosols (fossil soils) in Asia from Early Devonian deposits of Yunnan, China. Plant traces are extensive within the soil and occur as complex network-like structures, which are interpreted as representing long-lived, belowground rhizomes of the basal lycopsid Drepanophycus The rhizomes produced large clones and helped the plant survive frequent sediment burial in well-drained soils within a seasonal wet-dry climate zone. Rhizome networks contributed to the accumulation and pedogenesis of floodplain sediments and increased the soil stabilizing effects of early plants. Predating the appearance of trees with deep roots in the Middle Devonian, plant rhizomes have long functioned in the belowground soil ecosystem. This study presents strong, direct evidence for plant-soil interactions at an early stage of vascular plant radiation. Soil stabilization by complex rhizome systems was apparently widespread, and contributed to landscape modification at an earlier time than had been appreciated.

Belowground rhizomes in paleosols: The hidden half of an Early Devonian vascular plant

PubMed Central

Xue, Jinzhuang; Deng, Zhenzhen; Huang, Pu; Huang, Kangjun; Benton, Michael J.; Cui, Ying; Wang, Deming; Liu, Jianbo; Shen, Bing; Basinger, James F.; Hao, Shougang

2016-01-01

The colonization of terrestrial environments by rooted vascular plants had far-reaching impacts on the Earth system. However, the belowground structures of early vascular plants are rarely documented, and thus the plant−soil interactions in early terrestrial ecosystems are poorly understood. Here we report the earliest rooted paleosols (fossil soils) in Asia from Early Devonian deposits of Yunnan, China. Plant traces are extensive within the soil and occur as complex network-like structures, which are interpreted as representing long-lived, belowground rhizomes of the basal lycopsid Drepanophycus. The rhizomes produced large clones and helped the plant survive frequent sediment burial in well-drained soils within a seasonal wet−dry climate zone. Rhizome networks contributed to the accumulation and pedogenesis of floodplain sediments and increased the soil stabilizing effects of early plants. Predating the appearance of trees with deep roots in the Middle Devonian, plant rhizomes have long functioned in the belowground soil ecosystem. This study presents strong, direct evidence for plant−soil interactions at an early stage of vascular plant radiation. Soil stabilization by complex rhizome systems was apparently widespread, and contributed to landscape modification at an earlier time than had been appreciated. PMID:27503883

The origin of modern agglutinated foraminiferal assemblages: evidence from a stratified fjord

NASA Astrophysics Data System (ADS)

Murray, John W.; Alve, Elisabeth; Cundy, Andrew

2003-11-01

Loch Etive, a silled 145 m deep fjord on the Scottish west coast, provides an example of modern benthic foraminiferal assemblages at intermediate depths (i.e., below the intertidal zone and above the CCD) consisting almost exclusively of organic-cemented agglutinated forms. Since such faunas from intermediate depths are rare in modern oceans but relatively common in the fossil record, the present study allows new insights into one kind of ancient environment for which there are few modern analogues. The strong dominance of agglutinated forms (both living and in some dead assemblages of foraminifera to the exclusion of calcareous taxa) is attributed to the unusual oceanographic conditions. These include a combination of restricted deep-water renewals and strong influence of freshwater which drains through large areas (relative to the size of the loch) of vegetated land. The result is calm bottom water conditions with commonly occurring oxygen depletion (although not anoxic), brackish water throughout the water column (salinity 28 in the deeper parts), and organic-rich (mostly terrestrially derived) sediments with geochemical properties, which, to a much larger degree than open marine ones, are controlled by local input. This environment supports low abundance and low diversity live assemblages, mainly restricted to the surface 1 cm of sediment. The dead assemblages show similar faunal characteristics, but the calcareous components are, due to carbonate dissolution, even more reduced. One of the calcareous species in Loch Etive is Elphidium albiumbilicatum. Its occurrence is the first record in British waters and it matches the previously suggested southern limit of its distribution. Analysis of a 90 cm long core representing sediments deposited over the past two centuries shows the presence of a calcareous dominated assemblage, including more marine species, with a higher diversity, in the lower part. This suggests that Loch Etive is in the process of going from a marine, to a more terrestrial dominated environment. The relatively high sedimentation rate (0.5 cm per yr), the apparent lack of smearing through bioturbation, and the presence of faunal changes in response to reduced marine influence over the past centuries, shows that Loch Etive has a good potential for performing high-resolution climatic studies.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bishop, James K.B.; Wood, Todd

Three Carbon Explorer (CE) floats profiling to kilometer depths in the Southern Ocean tracked dawn-dusk variations of mixing/stratification, particulate organic carbon (POC), and light scattering and sedimentation at 100, 250, and 800 m continuously from January 2002 to April 2003. Data were analyzed in conjunction with contemporaneous satellite winds and chlorophyll and derived subsurface light fields. The CE deployed at 66{sup o}S 172{sup o}W operated in the ice edge zone in absence of light. Two CEs deployed at 55{sup o}S 172{sup o}W recorded wintertime mixing to {approx}400 m, yet observed very different bloom dynamics and sedimentation the following spring. Fourmore » hypotheses are explored. The strongest is that shallow transient stratification of the deep winter mixed layer to shallower than photosynthetic critical depth occurred more frequently in the non-bloom/higher sedimentation case. The lower particle export to 800 m under the bloom was hypothesized to be due to higher interception of sinking carbon by a relatively starved over wintering zooplankton population. In the Southern Ocean surface phytoplankton biomass may counter indicate particle flux at kilometer depths.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prahl, F.G.; Sparrow, M.A.; Eversmeyer, B.

Elemental and stable carbon isotopic compositions and biomarker concentrations were determined in sediments from the Columbia River basin and the Washington margin in order to evaluate geochemical approaches for quantifying terrestrial organic matter in marine sediments. The biomarkers include: an homologous series of long-chain n-alkanes derived from the surface waxes of higher plants; phenolic and hydroxyalkanoic compounds produced by CuO oxidation of two major vascular plant biopolymers, lignin and cutin. All marine sediments, including samples collected from the most remote sites in Cascadia Basin, showed organic geochemical evidence for the presence of terrestrial organic carbon. Using endmember values for themore » various biomarkers determined empirically by two independent means, the authors estimate that the terrestrial contribution to the Washington margin is [approximately] 60% for shelf sediments, [approximately] 30% for slope sediments, and decreases further to [le] 15% in basin sediments. Results from the same geochemical measurements made with depth in gravity core 6705-7 from Cascadia Seachannel suggest that this approach to assess terrestrial organic carbon contributions to contemporary deposits on the Washington margin can be applied to the study of sediments depositing in this region since the last glacial period.« less

Spatial variations of community structures and methane cycling across a transect of Lei-Gong-Hou mud volcanoes in eastern Taiwan

PubMed Central

Wang, Pei-Ling; Chiu, Yi-Ping; Cheng, Ting-Wen; Chang, Yung-Hsin; Tu, Wei-Xain; Lin, Li-Hung

2014-01-01

This study analyzed cored sediments retrieved from sites distributed across a transect of the Lei-Gong-Hou mud volcanoes in eastern Taiwan to uncover the spatial distributions of biogeochemical processes and community assemblages involved in methane cycling. The profiles of methane concentration and carbon isotopic composition revealed various orders of the predominance of specific methane-related metabolisms along depth. At a site proximal to the bubbling pool, the methanogenic zone was sandwiched by the anaerobic methanotrophic zones. For two sites distributed toward the topographic depression, the methanogenic zone overlaid the anaerobic methanotrophic zone. The predominance of anaerobic methanotrophy at specific depth intervals is supported by the enhanced copy numbers of the ANME-2a 16S rRNA gene and coincides with high dissolved Fe/Mn concentrations and copy numbers of the Desulfuromonas/Pelobacter 16S rRNA gene. Assemblages of 16S rRNA and mcrA genes revealed that methanogenesis was mediated by Methanococcoides and Methanosarcina. pmoA genes and a few 16S rRNA genes related to aerobic methanotrophs were detected in limited numbers of subsurface samples. While dissolved Fe/Mn signifies the presence of anaerobic metabolisms near the surface, the correlations between geochemical characteristics and gene abundances, and the absence of aerobic methanotrophs in top sediments suggest that anaerobic methanotrophy is potentially dependent on iron/manganese reduction and dominates over aerobic methanotrophy for the removal of methane produced in situ or from a deep source. Near-surface methanogenesis contributes to the methane emissions from mud platform. The alternating arrangements of methanogenic and methanotrophic zones at different sites suggest that the interactions between mud deposition, evaporation, oxidation and fluid transport modulate the assemblages of microbial communities and methane cycling in different compartments of terrestrial mud volcanoes. PMID:24723919

Hydrothermal sediments are a source of water column Fe and Mn in the Bransfield Strait, Antarctica

NASA Astrophysics Data System (ADS)

Aquilina, Alfred; Homoky, William B.; Hawkes, Jeffrey A.; Lyons, Timothy W.; Mills, Rachel A.

2014-07-01

Short sediment cores were collected from ∼1100 m water depth at the top of Hook Ridge, a submarine volcanic edifice in the Central Basin of the Bransfield Strait, Antarctica, to assess Fe and Mn supply to the water column. Low-temperature hydrothermal fluids advect through these sediments and, in places, subsurface H2S is present at high enough concentrations to support abundant Sclerolinum sp., an infaunal tubeworm that hosts symbiotic thiotrophic bacteria. The water column is fully oxic, and oxygen penetration depths at all sites are 2-5 cmbsf. Pore water Fe and Mn content is high within the subsurface ferruginous zone (max. 565 μmol Fe L-1, >3-7 cmbsf)-14-18 times higher than values measured at a nearby, background site of equivalent water depth. Diffusion and advection of pore waters supply significant Fe and Mn to the surface sediment. Sequential extraction of the sediment demonstrates that there is a significant enrichment in a suite of reactive, authigenic Fe minerals in the upper 0-5 cm of sediment at one site characterised by weathered crusts at the seafloor. At a site with only minor authigenic mineral surface enrichment we infer that leakage of pore water Fe and Mn from the sediment leads to enriched total dissolvable Fe and Mn in bottom waters. An Eh sensor mounted on a towed package mapped a distinct Eh signature above this coring site which is dispersed over several km at the depth of Hook Ridge. We hypothesise that the main mechanism for Fe and Mn efflux from the sediment is breach of the surface oxic layer by the abundant Sclerolinum sp., along with episodic enhancements by physical mixing and resuspension of sediment in this dynamic volcanic environment. We propose that Hook Ridge sediments are an important source of Fe and Mn to the deep waters of the Central Basin in the Bransfield Strait, where concentrations are sustained by the benthic flux, and Fe is stabilised in the water column as either colloidal phases or ligand-bound dissolved species. Entrainment of this water mass into the Drake Passage and thereby the Antarctic Circumpolar Current could provide a significant metal source to this HNLC region of the Southern Ocean if mixing and upwelling occurs before removal of this metal pool to underlying sediments. Sediment-covered volcanic ridges are common within rifted margins and may play a previously overlooked role in the global Fe cycle.

77 FR 14717 - National Oil and Hazardous Substances Pollution Contingency Plan; National Priorities List...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-13

... preclude future actions under Superfund. This partial deletion pertains to the surface soil, unsaturated subsurface soil, surface water and sediments of Operable Unit (OU) 1, the Gateway Lake Ash Study Area, and.... Surface soil, unsaturated subsurface soil, surface water, and sediments at OU-2, OU-3, OU-4, OU-5, OU-6...

Effect of replacing surface inlets with blind or gravel inlets on sediment and phosphorus subsurface drainage losses

USDA-ARS?s Scientific Manuscript database

Open surface inlets that connect to subsurface tile drainage systems provide a direct pathway for sediment, nutrients, and agrochemicals to surface waters. This study was conducted to determine whether modifying open inlets by burying them in gravel capped with 30 cm of sandy clay loam soil or in ve...

Subsurface warming in the subpolar North Atlantic during rapid climate events in the Early and Mid-Pleistocene

NASA Astrophysics Data System (ADS)

Hernández-Almeida, Iván; Sierro, Francisco; Cacho, Isabel; Abel Flores, José

2014-05-01

A new high-resolution reconstruction of the temperature and salinity of the subsurface waters using paired Mg/Ca-δ18O measurements on the planktonic foraminifera Neogloboquadrina pachyderma sinistrorsa (sin.) was conducted on a deep-sea sediment core in the subpolar North Atlantic (Site U1314). This study aims to reconstruct millennial-scale subsurface hydrography variations during the Early and Mid-Pleistocene (MIS 31-19). These rapid climate events are characterized by abrupt shifts between warm/cold conditions, and ice-sheet oscillations, as evidenced by major ice rafting events recorded in the North Atlantic sediments (Hernández-Almeida et al., 2012), similar to those found during the Last Glacial period (Marcott et al, 2011). The Mg/Ca derived paleotemperature and salinity oscillations prior and during IRD discharges at Site U1314 are related to changes in intermediate circulation. The increases in Mg/Ca paleotemperatures and salinities during the IRD event are preceded by short episodes of cooling and freshening of subsurface waters. The response of the AMOC to this perturbation is an increased of warm and salty water coming from the south, transported to high latitudes in the North Atlantic beneath the thermocline. This process is accompanied by a southward shift in the convection cell from the Nordic Seas to the subpolar North Atlantic and better ventilation of the North Atlantic at mid-depths. Poleward transport of warm and salty subsurface subtropical waters causes intense basal melting and thinning of marine ice-shelves, that culminates in large-scale instability of the ice sheets, retreat of the grounding line and iceberg discharge. The mechanism proposed involves the coupling of the AMOC with ice-sheet dynamics, and would explain the presence of these fluctuations before the establishment of high-amplitude 100-kyr glacial cycles. Hernández-Almeida, I., Sierro, F.J., Cacho, I., Flores, J.A., 2012. Impact of suborbital climate changes in the North Atlantic on ice sheet dynamics at the Mid-Pleistocene Transition. Paleoceanography 27, PA3214. Marcott, S.A., Clark, P.U., Padman, L., Klinkhammer, G.P., Springer, S.R., Liu, Z., Otto-Bliesner, B.L., Carlson, A.E., Ungerer, A., Padman, J., He, F., Cheng, J., Schmittner, A., 2011. Ice-shelf collapse from subsurface warming as a trigger for Heinrich events. Proceedings of the National Academy of Sciences 108, 13415-13419

Identification and Removal of Contaminant Sequences From Ribosomal Gene Databases: Lessons From the Census of Deep Life

PubMed Central

Sheik, Cody S.; Reese, Brandi Kiel; Twing, Katrina I.; Sylvan, Jason B.; Grim, Sharon L.; Schrenk, Matthew O.; Sogin, Mitchell L.; Colwell, Frederick S.

2018-01-01

Earth’s subsurface environment is one of the largest, yet least studied, biomes on Earth, and many questions remain regarding what microorganisms are indigenous to the subsurface. Through the activity of the Census of Deep Life (CoDL) and the Deep Carbon Observatory, an open access 16S ribosomal RNA gene sequence database from diverse subsurface environments has been compiled. However, due to low quantities of biomass in the deep subsurface, the potential for incorporation of contaminants from reagents used during sample collection, processing, and/or sequencing is high. Thus, to understand the ecology of subsurface microorganisms (i.e., the distribution, richness, or survival), it is necessary to minimize, identify, and remove contaminant sequences that will skew the relative abundances of all taxa in the sample. In this meta-analysis, we identify putative contaminants associated with the CoDL dataset, recommend best practices for removing contaminants from samples, and propose a series of best practices for subsurface microbiology sampling. The most abundant putative contaminant genera observed, independent of evenness across samples, were Propionibacterium, Aquabacterium, Ralstonia, and Acinetobacter. While the top five most frequently observed genera were Pseudomonas, Propionibacterium, Acinetobacter, Ralstonia, and Sphingomonas. The majority of the most frequently observed genera (high evenness) were associated with reagent or potential human contamination. Additionally, in DNA extraction blanks, we observed potential archaeal contaminants, including methanogens, which have not been discussed in previous contamination studies. Such contaminants would directly affect the interpretation of subsurface molecular studies, as methanogenesis is an important subsurface biogeochemical process. Utilizing previously identified contaminant genera, we found that ∼27% of the total dataset were identified as contaminant sequences that likely originate from DNA extraction and DNA cleanup methods. Thus, controls must be taken at every step of the collection and processing procedure when working with low biomass environments such as, but not limited to, portions of Earth’s deep subsurface. Taken together, we stress that the CoDL dataset is an incredible resource for the broader research community interested in subsurface life, and steps to remove contamination derived sequences must be taken prior to using this dataset. PMID:29780369

Identification and Removal of Contaminant Sequences From Ribosomal Gene Databases: Lessons From the Census of Deep Life.

PubMed

Sheik, Cody S; Reese, Brandi Kiel; Twing, Katrina I; Sylvan, Jason B; Grim, Sharon L; Schrenk, Matthew O; Sogin, Mitchell L; Colwell, Frederick S

2018-01-01

Earth's subsurface environment is one of the largest, yet least studied, biomes on Earth, and many questions remain regarding what microorganisms are indigenous to the subsurface. Through the activity of the Census of Deep Life (CoDL) and the Deep Carbon Observatory, an open access 16S ribosomal RNA gene sequence database from diverse subsurface environments has been compiled. However, due to low quantities of biomass in the deep subsurface, the potential for incorporation of contaminants from reagents used during sample collection, processing, and/or sequencing is high. Thus, to understand the ecology of subsurface microorganisms (i.e., the distribution, richness, or survival), it is necessary to minimize, identify, and remove contaminant sequences that will skew the relative abundances of all taxa in the sample. In this meta-analysis, we identify putative contaminants associated with the CoDL dataset, recommend best practices for removing contaminants from samples, and propose a series of best practices for subsurface microbiology sampling. The most abundant putative contaminant genera observed, independent of evenness across samples, were Propionibacterium , Aquabacterium , Ralstonia , and Acinetobacter . While the top five most frequently observed genera were Pseudomonas , Propionibacterium , Acinetobacter , Ralstonia , and Sphingomonas . The majority of the most frequently observed genera (high evenness) were associated with reagent or potential human contamination. Additionally, in DNA extraction blanks, we observed potential archaeal contaminants, including methanogens, which have not been discussed in previous contamination studies. Such contaminants would directly affect the interpretation of subsurface molecular studies, as methanogenesis is an important subsurface biogeochemical process. Utilizing previously identified contaminant genera, we found that ∼27% of the total dataset were identified as contaminant sequences that likely originate from DNA extraction and DNA cleanup methods. Thus, controls must be taken at every step of the collection and processing procedure when working with low biomass environments such as, but not limited to, portions of Earth's deep subsurface. Taken together, we stress that the CoDL dataset is an incredible resource for the broader research community interested in subsurface life, and steps to remove contamination derived sequences must be taken prior to using this dataset.

Isotopic evidence for the influence of typhoons and submarine canyons on the sourcing and transport behavior of biospheric organic carbon to the deep sea

NASA Astrophysics Data System (ADS)

Zheng, Li-Wei; Ding, Xiaodong; Liu, James T.; Li, Dawei; Lee, Tsung-Yu; Zheng, Xufeng; Zheng, Zhenzhen; Xu, Min Nina; Dai, Minhan; Kao, Shuh-Ji

2017-05-01

Export of biospheric organic carbon from land masses to the ocean plays an important role in regulating the global carbon cycle. High-relief islands in the western Pacific are hotspots for such land-to-ocean carbon transport due to frequent floods and active tectonics. Submarine canyon systems serve as a major conduit to convey terrestrial organics into the deep sea, particularly during episodic floods, though the nature of ephemeral sediment transportation through such canyons remains unclear. In this study, we deployed a sediment trap in southwestern Taiwan's Gaoping submarine canyon during summer 2008, during which Typhoon Kalmaegi impacted the study area. We investigated sources of particulate organic carbon and quantified the content of fossil organic carbon (OCf) and biospheric non-fossil carbon (OCnf) during typhoon and non-typhoon periods, based on relations between total organic carbon (TOC), isotopic composition (δ13 C, 14C), and nitrogen to carbon ratios (N/C) of newly and previously reported source materials. During typhoons, flooding connected terrestrial rivers to the submarine canyon. Fresh plant debris was not found in the trap except in the hyperpycnal layer, suggesting that only hyperpycnal flow is capable of entraining plant debris, while segregation had occurred during non-hyperpycnal periods. The OCnf components in typhoon flood and trapped samples were likely sourced from aged organics buried in ancient landslides. During non-typhoon periods, the canyon is more connected to the shelf, where waves and tides cause reworking, thus allowing abiotic and biotic processes to generate isotopically uniform and similarly aged OCnf for transport into the canyon. Therefore, extreme events coupled with the submarine canyon system created an efficient method for deep-sea burial of freshly produced organic-rich material. Our results shed light on the ephemeral transport of organics within a submarine canyon system on an active tectonic margin.

Sporadic Groundwater Upwelling in Deep Martian Craters: Evidence for Lacustrine Clays and Carbonates

NASA Technical Reports Server (NTRS)

Michalski, J. R.; Rogers, A. D.; Wright, S. P.; Niles, P.; Cuadros, J.

2012-01-01

While the surface of Mars may have had an active hydrosphere early in its history [1], it is likely that this water retreated to the subsurface early on due to loss of the magnetic field and early atmosphere [2]. This likely resulted in the formation of two distinct aqueous regimes for Mars from the Late Noachian onward: one dominated by redistribution of surface ice and occasional melting of snow/ice [3], and one dominated by groundwater activity [4]. The excavation of alteration minerals from deep in the crust by impact craters points to an active, ancient, deep hydrothermal system [5]. Putative sapping features [6] may occur where the groundwater breached the surface. Upwelling groundwater may also have played a critical role in the formation of massive, layered, cemented sediments in Sinus Meridiani [7,8], in the Valles Marineris [9], and possibly in Gale Crater [10], where the Curiosity Rover will land later this year. Understanding the past distribution, geochemistry, and significance of groundwater on Mars is critical to untangling the origins of deep alteration minerals, Hesperian sulfate deposits, and crater fill deposits at Gale Crater or in other locations.

Probing Water Ice for Trace Organics using Raman Scattering in the Laboratory and Terrestrial Field Analogs

NASA Astrophysics Data System (ADS)

Winebrenner, D. P.; Kirby, J. P.; Marquardt, B.

2013-12-01

Trace constituents in (predominantly) water ice are key to understanding planetary and astrobiological processes on a wide variety of solar system bodies, including Europa, Enceladus, Titan, Ceres, Mars, and comets. Organic traces are of particular interest not only for astrobiology but also, for example, for understanding the fates of abiotic organics delivered by meteorites. Raman scattering is known for specificity in identifying bonds and compounds, but has generally been considered relatively insensitive to concentrations characteristic of trace constituents. Here we test in doped water ice a Raman probe system that was developed for industrial and environmental applications and that has characterized select traces at ppm-levels near a deep-sea hydrothermal vent. We report in particular results for 17 amino acids and for aromatic hydrocarbons. Finally, based on physically robust Raman optics developed for industrial environments, we proposal a concept for subsurface investigation of traces in terrestrial analog environments such as glaciers and ice sheets, by means of integrating a Raman probe with a thermal ice melt probe recently field-tested in Greenland.

Thermodynamically controlled preservation of organic carbon in floodplains

DOE PAGES

Boye, Kristin; Noel, Vincent; Tfaily, Malak M.; ...

2017-05-01

Organic matter decomposition in soils and terrestrial sediments has a prominent role in the global carbon cycle. Carbon stocks in anoxic environments, such as wetlands and the subsurface of floodplains, are large and presumed to decompose slowly. The degree of microbial respiration in anoxic environments is typically thought to depend on the energetics of available terminal electron acceptors such as nitrate or sulfate; microbes couple the reduction of these compounds to the oxidation of organic carbon. But, it is also possible that the energetics of the organic carbon itself can determine whether it is decomposed. We examined water-soluble organic carbonmore » by Fourier-transform ion-cyclotron-resonance mass spectrometry to compare the chemical composition and average nominal oxidation state of carbon—a metric reflecting whether microbial oxidation of organic matter is thermodynamically favourable—in anoxic (sulfidic) and oxic (non-sulfidic) floodplain sediments. We also observed distinct minima in the average nominal oxidation state of water-soluble carbon in sediments exhibiting anoxic, sulfate-reducing conditions, suggesting preservation of carbon compounds with nominal oxidation states below the threshold that makes microbial sulfate reduction thermodynamically favourable. Finally, we show that thermodynamic limitations constitute an important complement to other mechanisms of carbon preservation, such as enzymatic restrictions and mineral association, within anaerobic environments.« less

Thermodynamically controlled preservation of organic carbon in floodplains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boye, Kristin; Noel, Vincent; Tfaily, Malak M.

Organic matter decomposition in soils and terrestrial sediments has a prominent role in the global carbon cycle. Carbon stocks in anoxic environments, such as wetlands and the subsurface of floodplains, are large and presumed to decompose slowly. The degree of microbial respiration in anoxic environments is typically thought to depend on the energetics of available terminal electron acceptors such as nitrate or sulfate; microbes couple the reduction of these compounds to the oxidation of organic carbon. But, it is also possible that the energetics of the organic carbon itself can determine whether it is decomposed. We examined water-soluble organic carbonmore » by Fourier-transform ion-cyclotron-resonance mass spectrometry to compare the chemical composition and average nominal oxidation state of carbon—a metric reflecting whether microbial oxidation of organic matter is thermodynamically favourable—in anoxic (sulfidic) and oxic (non-sulfidic) floodplain sediments. We also observed distinct minima in the average nominal oxidation state of water-soluble carbon in sediments exhibiting anoxic, sulfate-reducing conditions, suggesting preservation of carbon compounds with nominal oxidation states below the threshold that makes microbial sulfate reduction thermodynamically favourable. Finally, we show that thermodynamic limitations constitute an important complement to other mechanisms of carbon preservation, such as enzymatic restrictions and mineral association, within anaerobic environments.« less

Thermodynamically controlled preservation of organic carbon in floodplains

NASA Astrophysics Data System (ADS)

Boye, Kristin; Noël, Vincent; Tfaily, Malak M.; Bone, Sharon E.; Williams, Kenneth H.; Bargar, John R.; Fendorf, Scott

2017-06-01

Organic matter decomposition in soils and terrestrial sediments has a prominent role in the global carbon cycle. Carbon stocks in anoxic environments, such as wetlands and the subsurface of floodplains, are large and presumed to decompose slowly. The degree of microbial respiration in anoxic environments is typically thought to depend on the energetics of available terminal electron acceptors such as nitrate or sulfate; microbes couple the reduction of these compounds to the oxidation of organic carbon. However, it is also possible that the energetics of the organic carbon itself can determine whether it is decomposed. Here we examined water-soluble organic carbon by Fourier-transform ion-cyclotron-resonance mass spectrometry to compare the chemical composition and average nominal oxidation state of carbon--a metric reflecting whether microbial oxidation of organic matter is thermodynamically favourable--in anoxic (sulfidic) and oxic (non-sulfidic) floodplain sediments. We observed distinct minima in the average nominal oxidation state of water-soluble carbon in sediments exhibiting anoxic, sulfate-reducing conditions, suggesting preservation of carbon compounds with nominal oxidation states below the threshold that makes microbial sulfate reduction thermodynamically favourable. We conclude that thermodynamic limitations constitute an important complement to other mechanisms of carbon preservation, such as enzymatic restrictions and mineral association, within anaerobic environments.

Soil Microbial Community Contribution to Small Headwater Stream Metabolism.

NASA Astrophysics Data System (ADS)

Clapcott, J. E.; Gooderham, J. P.; Barmuta, L. A.; Davies, P. E.

2005-05-01

The temporal dynamics of sediment respiration were examined in seven small headwater streams in forested catchments in 2004. A strong seasonal response was observed with higher respiration rates in depositional zones than in gravel runs. The data were also examined in the context of proportional habitat distributions that highlighted the importance of high flow events in shaping whole stream metabolic budgets. This study specifically examines the question of terrestrial soil respiration contribution to whole stream metabolism by the controlled inundation of terrestrial soils. The experiment included six experimentally inundated terrestrial zones, six terrestrial controls, and six in-stream depositional zones. Sediment bacterial respiration was measured using 14C leucine incorporation and cotton strip bioassays were also employed to provide an indicative measure of sediment microbial activity. Despite high variability and exhibiting significantly lower bacterial activity than in-stream sediments, modelling using flow data and habitat mapping illustrated the important contribution of terrestrial soil respiration to the whole stream metabolic budgets of small headwater streams. In addition, microbial community composition examined using phospholipid fatty acid analysis clearly differentiated between terrestrial and aquatic communities. Freshly inundated terrestrial communities remained similar to un-inundated controls after 28 days.

Association among active seafloor deformation, mound formation, and gas hydrate growth and accumulation within the seafloor of the Santa Monica Basin, offshore California

USGS Publications Warehouse

Paull, C.K.; Normark, W.R.; Ussler, W.; Caress, D.W.; Keaten, R.

2008-01-01

Seafloor blister-like mounds, methane migration and gas hydrate formation were investigated through detailed seafloor surveys in Santa Monica Basin, offshore of Los Angeles, California. Two distinct deep-water (??? 800??m water depth) topographic mounds were surveyed using an autonomous underwater vehicle (carrying a multibeam sonar and a chirp sub-bottom profiler) and one of these was explored with the remotely operated vehicle Tiburon. The mounds are > 10??m high and > 100??m wide dome-shaped bathymetric features. These mounds protrude from crests of broad anticlines (~ 20??m high and 1 to 3??km long) formed within latest Quaternary-aged seafloor sediment associated with compression between lateral offsets in regional faults. No allochthonous sediments were observed on the mounds, except slumped material off the steep slopes of the mounds. Continuous streams of methane gas bubbles emanate from the crest of the northeastern mound, and extensive methane-derived authigenic carbonate pavements and chemosynthetic communities mantle the mound surface. The large local vertical displacements needed to produce these mounds suggests a corresponding net mass accumulation has occurred within the immediate subsurface. Formation and accumulation of pure gas hydrate lenses in the subsurface is proposed as a mechanism to blister the seafloor and form these mounds. ?? 2008 Elsevier B.V. All rights reserved.

East African weathering dynamics controlled by vegetation-climate feedbacks

USGS Publications Warehouse

Ivory, Sarah J.; McGlue, Michael M.; Ellis, Geoffrey S.; Boehlke, Adam; Lézine, Anne-Marie; Vincens, Annie; Cohen, Andrew S.

2017-01-01

Tropical weathering has important linkages to global biogeochemistry and landscape evolution in the East African rift. We disentangle the influences of climate and terrestrial vegetation on chemical weathering intensity and erosion at Lake Malawi using a long sediment record. Fossil pollen, microcharcoal, particle size, and mineralogy data affirm that the detrital clays accumulating in deep water within the lake are controlled by feedbacks between climate and hinterland forest composition. Particle-size patterns are also best explained by vegetation, through feedbacks with lake levels, wildfires, and erosion. We develop a new source-to-sink framework that links lacustrine sedimentation to hinterland vegetation in tropical rifts. Our analysis suggests that climate-vegetation interactions and their coupling to weathering/erosion could threaten future food security and has implications for accurately predicting petroleum play elements in continental rift basins.

Evidence for Seismogenic Hydrogen Gas, a Potential Microbial Energy Source on Earth and Mars.

PubMed

McMahon, Sean; Parnell, John; Blamey, Nigel J F

2016-09-01

The oxidation of molecular hydrogen (H2) is thought to be a major source of metabolic energy for life in the deep subsurface on Earth, and it could likewise support any extant biosphere on Mars, where stable habitable environments are probably limited to the subsurface. Faulting and fracturing may stimulate the supply of H2 from several sources. We report the H2 content of fluids present in terrestrial rocks formed by brittle fracturing on fault planes (pseudotachylites and cataclasites), along with protolith control samples. The fluids are dominated by water and include H2 at abundances sufficient to support hydrogenotrophic microorganisms, with strong H2 enrichments in the pseudotachylites compared to the controls. Weaker and less consistent H2 enrichments are observed in the cataclasites, which represent less intense seismic friction than the pseudotachylites. The enrichments agree quantitatively with previous experimental measurements of frictionally driven H2 formation during rock fracturing. We find that conservative estimates of current martian global seismicity predict episodic H2 generation by Marsquakes in quantities useful to hydrogenotrophs over a range of scales and recurrence times. On both Earth and Mars, secondary release of H2 may also accompany the breakdown of ancient fault rocks, which are particularly abundant in the pervasively fractured martian crust. This study strengthens the case for the astrobiological investigation of ancient martian fracture systems. Deep biosphere-Faults-Fault rocks-Seismic activity-Hydrogen-Mars. Astrobiology 16, 690-702.

Using UAVSAR Interferometry to Quantify the Geometry and Sediment Flux of Slow-moving Landslides in the Eel River Catchment, Northern California

NASA Astrophysics Data System (ADS)

Handwerger, A. L.; Huang, M. H.; Booth, A. M.; Fielding, E. J.

2017-12-01

Slow-moving, deep-seated landslides are highly erosive features that can remain active for periods of decades to centuries, playing a major role in landscape evolution. In the Eel River catchment, Northern California, slow-moving landslides are the primary contributor of sediment to the channel network, delivering >50% of the regional sediment flux despite occupying <10% of the landscape. While detailed, regional-scale measurements of surface kinematics can be made using remote sensing data like interferometric synthetic aperture radar (InSAR) or pixel tracking with SAR or optical images, subsurface measurements including landslide thickness are sparse. As a result, thickness estimates are often approximated from topographic data and globally-derived volume-area scaling relationships that may under- or over-predict landslide volumes by up to an order of magnitude at specific field sites. Furthermore, these relationships assume that the thickness is constant along the entire landslide body. To improve our measurements of landslide volume and kinematics we use repeat-pass InSAR from the NASA/JPL UAVSAR airborne radar acquired with 4 different look directions to quantify 3D surface displacements of 20 landslides across a 550 km2 area. We apply mass conservation techniques to 1) invert for landslide thickness and 2) solve for landslide rheology (i.e. depth-averaged velocity), which enables us to better constrain both volume and sediment flux. Our preliminary results indicate that the landslide thickness is highly variable with changes up to tens of meters along the landslide body. We also find that the landslides have a power law rheology with a plug-flow vertical velocity profile. Estimates of sediment flux contributed by individual landslides ranges from 103 to 104 m3/yr. The application of UAVSAR data represents a major advance from previous InSAR studies in this region and provides one of the first datasets containing 3D displacement measurements for multiple landslides occurring under nearly identical environmental conditions. Future work is aimed at using these subsurface and kinematic data to calculate landslide erosion rates and regional sediment flux and to better understand the controls on landslide dynamics over short- and long-timescales.

Ubiquitous Gammaproteobacteria dominate dark carbon fixation in coastal sediments.

PubMed

Dyksma, Stefan; Bischof, Kerstin; Fuchs, Bernhard M; Hoffmann, Katy; Meier, Dimitri; Meyerdierks, Anke; Pjevac, Petra; Probandt, David; Richter, Michael; Stepanauskas, Ramunas; Mußmann, Marc

2016-08-01

Marine sediments are the largest carbon sink on earth. Nearly half of dark carbon fixation in the oceans occurs in coastal sediments, but the microorganisms responsible are largely unknown. By integrating the 16S rRNA approach, single-cell genomics, metagenomics and transcriptomics with (14)C-carbon assimilation experiments, we show that uncultured Gammaproteobacteria account for 70-86% of dark carbon fixation in coastal sediments. First, we surveyed the bacterial 16S rRNA gene diversity of 13 tidal and sublittoral sediments across Europe and Australia to identify ubiquitous core groups of Gammaproteobacteria mainly affiliating with sulfur-oxidizing bacteria. These also accounted for a substantial fraction of the microbial community in anoxic, 490-cm-deep subsurface sediments. We then quantified dark carbon fixation by scintillography of specific microbial populations extracted and flow-sorted from sediments that were short-term incubated with (14)C-bicarbonate. We identified three distinct gammaproteobacterial clades covering diversity ranges on family to order level (the Acidiferrobacter, JTB255 and SSr clades) that made up >50% of dark carbon fixation in a tidal sediment. Consistent with these activity measurements, environmental transcripts of sulfur oxidation and carbon fixation genes mainly affiliated with those of sulfur-oxidizing Gammaproteobacteria. The co-localization of key genes of sulfur and hydrogen oxidation pathways and their expression in genomes of uncultured Gammaproteobacteria illustrates an unknown metabolic plasticity for sulfur oxidizers in marine sediments. Given their global distribution and high abundance, we propose that a stable assemblage of metabolically flexible Gammaproteobacteria drives important parts of marine carbon and sulfur cycles.

REASON for Europa

NASA Astrophysics Data System (ADS)

Patterson, Gerald Wesley; Blankenship, Don; Moussessian, Alina; Plaut, Jeffrey; Gim, Yonggyu; Schroeder, Dustin; Soderlund, Krista; Grima, Cyril; Chapin, Elaine

2015-11-01

The science goal of the Europa multiple flyby mission is to “explore Europa to investigate its habitability”. One of the primary instruments selected for the scientific payload is a multi-frequency, multi-channel ice penetrating radar system. This “Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON)” would revolutionize our understanding of Europa’s ice shell by providing the first direct measurements of its surface character and subsurface structure. REASON will address key questions regarding Europa’s habitability, including the existence of any liquid water, through the innovative use of radar sounding, altimetry, reflectometry, and plasma/particles analyses. These investigations require a dual-frequency radar (HF and VHF frequencies) instrument with simultaneous shallow and deep sounding that is designed for performance robustness in the challenging environment of Europa. The flyby-centric mission configuration is an opportunity to collect and transmit minimally processed data back to Earth and exploit advanced processing approaches developed for terrestrial airborne data sets. The observation and characterization of subsurface features beneath Europa’s chaotic surface requires discriminating abundant surface clutter from a relatively weak subsurface signal. Finally, the mission plan also includes using REASON as a nadir altimeter capable of measuring tides to test ice shell and ocean hypotheses as well as characterizing roughness across the surface statistically to identify potential follow-on landing sites. We will present a variety of measurement concepts for addressing these challenges.

REASON for Europa

NASA Astrophysics Data System (ADS)

Moussessian, A.; Blankenship, D. D.; Plaut, J. J.; Patterson, G. W.; Gim, Y.; Schroeder, D. M.; Soderlund, K. M.; Grima, C.; Young, D. A.; Chapin, E.

2015-12-01

The science goal of the Europa multiple flyby mission is to "explore Europa to investigate its habitability". One of the primary instruments selected for the scientific payload is a multi-frequency, multi-channel ice penetrating radar system. This "Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON)" would revolutionize our understanding of Europa's ice shell by providing the first direct measurements of its surface character and subsurface structure. REASON addresses key questions regarding Europa's habitability, including the existence of any liquid water, through the innovative use of radar sounding, altimetry, reflectometry, and plasma/particles analyses. These investigations require a dual-frequency radar (HF and VHF frequencies) instrument with concurrent shallow and deep sounding that is designed for performance robustness in the challenging environment of Europa. The flyby-centric mission configuration is an opportunity to collect and transmit minimally processed data back to Earth and exploit advanced processing approaches developed for terrestrial airborne data sets. The observation and characterization of subsurface features beneath Europa's chaotic surface require discriminating abundant surface clutter from a relatively weak subsurface signal. Finally, the mission plan also includes using REASON as a nadir altimeter capable of measuring tides to test ice shell and ocean hypotheses as well as characterizing roughness across the surface statistically to identify potential follow-on landing sites. We will present a variety of measurement concepts for addressing these challenges.

In-Situ Contained And Of Volatile Soil Contaminants

DOEpatents

Varvel, Mark Darrell

2005-12-27

The invention relates to a novel approach to containing and removing toxic waste from a subsurface environment. More specifically the present invention relates to a system for containing and removing volatile toxic chemicals from a subsurface environment using differences in surface and subsurface pressures. The present embodiment generally comprises a deep well, a horizontal tube, at least one injection well, at least one extraction well and a means for containing the waste within the waste zone (in-situ barrier). During operation the deep well air at the bottom of well (which is at a high pressure relative to the land surface as well as relative to the air in the contaminated soil) flows upward through the deep well (or deep well tube). This stream of deep well air is directed into the horizontal tube, down through the injection tube(s) (injection well(s)) and into the contaminate plume where it enhances volatization and/or removal of the contaminants.

In-Situ Containment and Extraction of Volatile Soil Contaminants

DOEpatents

Varvel, Mark Darrell

2005-12-27

The invention relates to a novel approach to containing and removing toxic waste from a subsurface environment. More specifically the present invention relates to a system for containing and removing volatile toxic chemicals from a subsurface environment using differences in surface and subsurface pressures. The present embodiment generally comprises a deep well, a horizontal tube, at least one injection well, at least one extraction well and a means for containing the waste within the waste zone (in-situ barrier). During operation the deep well air at the bottom of well (which is at a high pressure relative to the land surface as well as relative to the air in the contaminated soil) flows upward through the deep well (or deep well tube). This stream of deep well air is directed into the horizontal tube, down through the injection tube(s) (injection well(s)) and into the contaminate plume where it enhances volatization and/or removal of the contaminants.

Electrically Conducting, Ca-Rich Brines, Rather Than Water, Expected in the Martian Subsurface

NASA Technical Reports Server (NTRS)

Burt, D. M.; Knauth, L. P.

2003-01-01

If Mars ever possessed a salty liquid hydrosphere, which later partly evaporated and froze down, then any aqueous fluids left near the surface could have evolved to become dense eutectic brines. Eutectic brines, by definition, are the last to freeze and the first to melt. If CaC12-rich, such brines can remain liquid until temperatures below 220 K, close to the average surface temperature of Mars. In the Martian subsurface, in intimate contact with the Ca-rich basaltic regolith, NaC1-rich early brines should have reacted to become Ca-rich. Fractional crystallization (freezing) and partial melting would also drive brines toward CaC12-rich compositions. In other words, eutectic brine compositions could be present in the shallow subsurface of Mars, for the same reasons that eutectic magma compositions are common on Earth. Don Juan Pond, Antarctica, a CaC12-rich eutectic brine, provides a possible terrestrial analog, particularly because it is fed from a basaltic aquifer. Owing to their relative density and fluid nature, brines in the Martian regolith should eventually become sandwiched between ice above and salts beneath. A thawing brine sandwich provides one explanation (among many) for the young gullies recently attributed to seepage of liquid water on Mars. Whether or not brine seepage explains the gullies phenomenon, dense, CaC12-rich brines are to be expected in the deep subsurface of Mars, although they might be somewhat diluted (temperatures permitting) and of variable salt composition. In any case, they should be good conductors of electricity.

High-resolution seismic-reflection images across the ICDP-USGS Eyreville deep drilling site, Chesapeake Bay impact structure

USGS Publications Warehouse

Powars, D.S.; Catchings, R.D.; Goldman, M.R.; Gohn, G.S.; Horton, J. Wright; Edwards, L.E.; Rymer, M.J.; Gandhok, G.

2009-01-01

The U.S. Geological Survey (USGS) acquired two 1.4-km-long, high-resolution (??5 m vertical resolution) seismic-reflection lines in 2006 that cross near the International Continental Scientifi c Drilling Program (ICDP)-USGS Eyreville deep drilling site located above the late Eocene Chesapeake Bay impact structure in Virginia, USA. Five-meter spacing of seismic sources and geophones produced high-resolution images of the subsurface adjacent to the 1766-m-depth Eyreville core holes. Analysis of these lines, in the context of the core hole stratigraphy, shows that moderateamplitude, discontinuous, dipping reflections below ??527 m correlate with a variety of Chesapeake Bay impact structure sediment and rock breccias recovered in the cores. High-amplitude, continuous, subhorizontal reflections above ??527 m depth correlate with the uppermost part of the Chesapeake Bay impact structure crater-fi ll sediments and postimpact Eocene to Pleistocene sediments. Refl ections with ??20-30 m of relief in the uppermost part of the crater-fi ll and lowermost part of the postimpact section suggest differential compaction of the crater-fi ll materials during early postimpact time. The top of the crater-fi ll section also shows ??20 m of relief that appears to represent an original synimpact surface. Truncation surfaces, locally dipping reflections, and depth variations in reflection amplitudes generally correlate with the lithostratigraphic and sequence-stratigraphic units and contacts in the core. Seismic images show apparent postimpact paleochannels that include the fi rst possible Miocene paleochannels in the Mid-Atlantic Coastal Plain. Broad downwarping in the postimpact section unrelated to structures in the crater fi ll indicates postimpact sediment compaction. ?? 2009 The Geological Society of America.

Isolation of Geobacter species from diverse sedimentary environments

USGS Publications Warehouse

Coaxes, J.D.; Phillips, E.J.P.; Lonergan, D.J.; Jenter, H.; Lovley, D.R.

1996-01-01

In an attempt to better understand the microorganisms responsible for Fe(III) reduction in sedimentary environments, Fe(III)-reducing microorganisms were enriched for and isolated from freshwater aquatic sediments, a pristine deep aquifer, and a petroleum-contaminated shallow aquifer. Enrichments were initiated with acetate or toluene as the electron donor and Fe(III) as the electron acceptor. Isolations were made with acetate or benzoate. Five new strains which could obtain energy for growth by dissimilatory Fe(III) reduction were isolated. All five isolates are gram- negative strict anaerobes which grow with acetate as the electron donor and Fe(III) as the electron acceptor. Analysis of the 16S rRNA sequence of the isolated organisms demonstrated that they all belonged to the genus Geobacter in the delta subdivision of the Proteobacteria. Unlike the type strain, Geobacter metallireducens, three of the five isolates could use H2 as an electron donor fur Fe(III) reduction. The deep subsurface isolate is the first Fe(III) reducer shown to completely oxidize lactate to carbon dioxide, while one of the freshwater sediment isolates is only the second Fe(III) reducer known that can oxidize toluene. The isolation of these organisms demonstrates that Geobacter species are widely distributed in a diversity of sedimentary environments in which Fe(III) reduction is an important process.

Diversity And Abundance Of Deep-Water Coral Mounds In The Straits Of Florida: A Result of Adaptability To Local Environments?

NASA Astrophysics Data System (ADS)

Correa, T. B.; Grasmueck, M.; Eberli, G.; Viggiano, D. A.; Rosenberg, A.; Reed, J. K.

2007-12-01

To improve the understanding of the Florida-Bahamas deep-water coral mound ecosystem, Autonomous Underwater Vehicle (AUV) surveys were conducted on five coral mound fields throughout the Straits of Florida (three sites at the base of slope of Great Bahama Bank (GBB), one in the middle of the Straits (MS) and one at the base of the Miami Terrace (MT)) in water depths of 590 to 860 m. The AUV provides high-resolution bathymetric maps, sub-bottom profiles and oceanographic data. The AUV survey sites were subsequently groundtruthed via sample collection and video transects, using the Johnson Sealink submersible. Contrary to previous surveys, we found a high diversity in coral mound morphology between sites separated by 15 to 80 km. The MT site is characterized by sinusoidal coral mound ridges, while the MS site contains densely clustered small coral mounds. Meanwhile, mounds of the GBB region are better developed, with some individual mounds reaching up to 90 m in height. Benthic coverage of live corals also differs between sites; the GBB sites are characterized by mounds densely covered by large thickets of live corals, while small thickets of mostly dead corals dominate the MT and MS sites. Several environmental factors may explain these differences. For example, bottom current patterns change between sites. The MT and the MS sites have a unidirectional regime (southward or northward flow, respectively), whereas the GBB sites have a tidal current regime. Sedimentation patterns as depicted by sub-bottom profiles also vary between the sites; coral mounds in the GBB area appear to receive higher sediment input, which can significantly enhance mound growth rates as the reef framework baffles and traps mobile sediments. However, coral mounds that cannot keep-up with the sedimentation rate are buried. Therefore, in the high sedimentation areas of GBB, flourishing live coral mounds are limited to elevated positions (i.e. plateaus, ridges crests) where sediment accumulation is lessened. Corals in these raised locations also benefit from increased exposure to nutrient-rich tidal currents, supporting a denser live coral coverage. Sub-bottom profiles of the MT site show undulating coral ridges developed on top of a relatively flat sub-surface, indicating that antecedent topography is not the only factor determining mound distribution. The integrated AUV data suggest that variable environmental factors, such as sedimentation and current patterns, contribute to the high diversity between coral mound sites of the Straits of Florida. Environmental conditions change over distances of only a few kilometers creating localized and diverse deep-water coral habitats. The deepwater fauna adapts to the local oceanographic and geological conditions. This results in an unexpectedly high abundance of deep-water coral communities with diverse expressions.

A strategy to sample nutrient dynamics across the terrestrial-aquatic interface at NEON sites

NASA Astrophysics Data System (ADS)

Hinckley, E. S.; Goodman, K. J.; Roehm, C. L.; Meier, C. L.; Luo, H.; Ayres, E.; Parnell, J.; Krause, K.; Fox, A. M.; SanClements, M.; Fitzgerald, M.; Barnett, D.; Loescher, H. W.; Schimel, D.

2012-12-01

The construction of the National Ecological Observatory Network (NEON) across the U.S. creates the opportunity for researchers to investigate biogeochemical transformations and transfers across ecosystems at local-to-continental scales. Here, we examine a subset of NEON sites where atmospheric, terrestrial, and aquatic observations will be collected for 30 years. These sites are located across a range of hydrological regimes, including flashy rain-driven, shallow sub-surface (perched, pipe-flow, etc), and deep groundwater, which likely affect the chemical forms and quantities of reactive elements that are retained and/or mobilized across landscapes. We present a novel spatial and temporal sampling design that enables researchers to evaluate long-term trends in carbon, nitrogen, and phosphorus biogeochemical cycles under these different hydrological regimes. This design focuses on inputs to the terrestrial system (atmospheric deposition, bulk precipitation), transfers (soil-water and groundwater sources/chemistry), and outputs (surface water, and evapotranspiration). We discuss both data that will be collected as part of the current NEON design, as well as how the research community can supplement the NEON design through collaborative efforts, such as providing additional datasets, including soil biogeochemical processes and trace gas emissions, and developing collaborative research networks. Current engagement with the research community working at the terrestrial-aquatic interface is critical to NEON's success as we begin construction, to ensure that high-quality, standardized and useful data are not only made available, but inspire further, cutting-edge research.

Is the genetic landscape of the deep subsurface biosphere affected by viruses?

PubMed

Anderson, Rika E; Brazelton, William J; Baross, John A

2011-01-01

Viruses are powerful manipulators of microbial diversity, biogeochemistry, and evolution in the marine environment. Viruses can directly influence the genetic capabilities and the fitness of their hosts through the use of fitness factors and through horizontal gene transfer. However, the impact of viruses on microbial ecology and evolution is often overlooked in studies of the deep subsurface biosphere. Subsurface habitats connected to hydrothermal vent systems are characterized by constant fluid flux, dynamic environmental variability, and high microbial diversity. In such conditions, high adaptability would be an evolutionary asset, and the potential for frequent host-virus interactions would be high, increasing the likelihood that cellular hosts could acquire novel functions. Here, we review evidence supporting this hypothesis, including data indicating that microbial communities in subsurface hydrothermal fluids are exposed to a high rate of viral infection, as well as viral metagenomic data suggesting that the vent viral assemblage is particularly enriched in genes that facilitate horizontal gene transfer and host adaptability. Therefore, viruses are likely to play a crucial role in facilitating adaptability to the extreme conditions of these regions of the deep subsurface biosphere. We also discuss how these results might apply to other regions of the deep subsurface, where the nature of virus-host interactions would be altered, but possibly no less important, compared to more energetic hydrothermal systems.

Is the Genetic Landscape of the Deep Subsurface Biosphere Affected by Viruses?

PubMed Central

Anderson, Rika E.; Brazelton, William J.; Baross, John A.

2011-01-01

Viruses are powerful manipulators of microbial diversity, biogeochemistry, and evolution in the marine environment. Viruses can directly influence the genetic capabilities and the fitness of their hosts through the use of fitness factors and through horizontal gene transfer. However, the impact of viruses on microbial ecology and evolution is often overlooked in studies of the deep subsurface biosphere. Subsurface habitats connected to hydrothermal vent systems are characterized by constant fluid flux, dynamic environmental variability, and high microbial diversity. In such conditions, high adaptability would be an evolutionary asset, and the potential for frequent host–virus interactions would be high, increasing the likelihood that cellular hosts could acquire novel functions. Here, we review evidence supporting this hypothesis, including data indicating that microbial communities in subsurface hydrothermal fluids are exposed to a high rate of viral infection, as well as viral metagenomic data suggesting that the vent viral assemblage is particularly enriched in genes that facilitate horizontal gene transfer and host adaptability. Therefore, viruses are likely to play a crucial role in facilitating adaptability to the extreme conditions of these regions of the deep subsurface biosphere. We also discuss how these results might apply to other regions of the deep subsurface, where the nature of virus–host interactions would be altered, but possibly no less important, compared to more energetic hydrothermal systems. PMID:22084639

Petrophysical Properties Of Sandy Sediments Possibly Hosting Gas Hydrate In The Eastern Margin Of Japan Sea

NASA Astrophysics Data System (ADS)

Uchida, T.; Takashima, I.; Sunaga, H.; Sasaki, S.; Matsumoto, R.

2011-12-01

In 2010 the MD179 project was undertaken by the Marion Dufresne aiming at recovery of deep seated gas and gas hydrate, methane induced carbonate, and deep sediments older than 300 ka in order to develop geologic model of gas hydrate accumulation and evaluate the possible environmental impact of gas hydrate for the last glacial-interglacial cycles. Sediment samples below the seafloor were obtained in the Umitaka Spur, Joetsu Channel, Toyama Trough, Japan Basin, Nishi Tsugaru and Okushiri Ridge areas by the MD179 cruise. Small amounts of sandy sediment have been retrieved as thin intercalations in Pleistocene and Holocene silty layers, where trace fossils and strong bioturbations are commonly observed. Those sandy sediments consist of very fine- to fine-grained sand grains, and are sometimes tuffaceous. Pore-size distribution measurements and thin-section observations of these arenite sands were undertaken, which indicatesd that porosities of muddy sediments are around 50 % but those of arenites range from 42 to 52 %, of which mean pore sizes and permeabilities are larger than those of siltstones and mudstones. These coarser sediments might have been transported approximately around 3 to 30 ka, where supplying sediments may not be abundant due to sea level fluctuation during the Pleistocene ice age. While the presence of gas hydrate in intergranular pores of arenite sands has not been confirmed, the soupy occurrence in recovered sediments may strongly indicate the presence of gas hydrate filling the intergranular pore system of arenite sands that is called pore-space hydrates. They have been recognized till now in the Mallik as well as in the Nankai Trough areas, which are considered to be very common even in the subsurface sandy sediments at the eastern margin of Japan Sea. Concentration of gas hydrate may need primary intergranular pores large enough to occur within a host sediment that may be arenite sand without matrix grains deposited in the sedimentary environment such as deep sea channels. The geological modeling of the gas hydrate formation and evolution system is concerned for energy resource potential in the Japan Sea as well as the Nankai Trough areas. Time of deposition of coarse-grained sediments can be recognized by the thermoluminescence (TL) dating method. TL dating works on the principle that materials containing naturally occurring radioactive isotopes such as uranium, thorium or potassium are subject to low levels of radiation. In mineral crystals, this leads to ionization of the atoms in the host material and freed electrons may become trapped in structural defects or holes in the mineral crystal lattice. These electrons can be released by heating under controlled conditions, and an emission of light occurs which is the basis of TL dating. Additionally they usually provide information about the provenance and the paleoenvironment when the sediments deposited. This study was performed as a part of the MH21 Research Consortium on methane hydrate in Japan.

Tracking Soil Organic Carbon Transport to Continental Margin Sediments Using Soil-Specific Hopanoid Biomarkers: a Case Study From the Congo Fan (ODP Site 1075)

NASA Astrophysics Data System (ADS)

Cooke, M. P.; Talbot, H. M.; Eniola, O.; Zabel, M.; Wagner, T.

2007-12-01

The transport and subsequent deposition of terrestrially derived organic matter into the ocean is an important but poorly constrained aspect of the modern global carbon cycle. In regions associated with large river systems it is likely that the terrestrial input of organic carbon is much more complex than commonly considered and very difficult to trace based on established geochemical proxies. It is therefore important to develop proxies that target the movement and fate of this terrestrial organic material. The identification of bacteriohopanepolyol (BHP) biomarkers unique to soil derived organic carbon (SOC) has enabled the transport of SOC into aquatic sediments to be traced. The extreme recalcitrance of BHPs enables these source specific compounds to be used on recent and ancient sediments to identify periods of high and low SOC input into sediments. BHPs are bacterial membrane compounds with a high degree of structural variability. They are analogous to steroids in eukaryotes and have been identified in over half of all bacteria studied for their presence. BHPs have a wide range of over 40 functional groups on the side chain, with up to 6 functional groups in each structure, and with methylation and unsaturation over 100 total structures have been identified1. During the BHP analysis of a wide range of soils from around the world we consistently measure high levels adenosylhopane, known to originate from purple non-sulphur, nitrogen fixing and ammonia oxidising bacteria and 2-methyl adenosyl hopane (m/z 802)2, from nitrogen fixing bacteria. Only 3 lacustrine sediments with large SOC supply from their catchments areas have been found to contain these markers in a survey of over 40 different non-marine settings. Recent studies on Late Quaternary sediments from the Congo deep sea fan (OPD site 1075, approximately 2 km water depth) provide a strong case to expect markers for SOC3. An initial analysis of the core samples confirms the presence of soil specific BHP markers in each sample analyzed down to 89 m depth in addition to the presence of common sediment associated BHPs. Concentrations of soil markers are high in the upper sediment section down to about 49 m supporting the case for these molecular markers as novel proxies for SOC supply and burial. Distinct peaks of adenosyl and 2 methyl adenosyl hopane at about 200, 300 and 550 kyrs tentatively imply that the rate of terrestrial organic matter discharge from tropical Africa significantly increased at these times, possibly associated with periods of reduced soil stability in the Congo catchment. Analysis of the surface sediments from 4 other cores in close proximity to ODP site 1075 clearly shows that the percentage contribution of soil marker BHPs decreases with increasing distance from the river mouth, indicating that the river is the source of these BHPs. References 1. Rohmer, M. 1993. Pure and Applied Chemistry 65, 1293-1298. 2. Talbot, H.M., Rohmer, M., Farrimond, P., 2007. Rapid Communications in Mass Spectrometry (In press). 3. Holtvoeth, J., Wagner, T., Kolonic, S., 2005. Geochimica et Cosmochimica Acta, 69, 2031-2041.

Sampling surface and subsurface particle-size distributions in wadable gravel-and cobble-bed streams for analyses in sediment transport, hydraulics, and streambed monitoring

Treesearch

Kristin Bunte; Steven R. Abt

2001-01-01

This document provides guidance for sampling surface and subsurface sediment from wadable gravel-and cobble-bed streams. After a short introduction to streams types and classifications in gravel-bed rivers, the document explains the field and laboratory measurement of particle sizes and the statistical analysis of particle-size distributions. Analysis of particle...

Watershed scale fungal community characterization along a pH gradient in a subsurface environment co-contaminated with uranium and nitrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jasrotia, Puja; Green, Stefan; Canion, Andy

2014-01-01

The objective of this study was to characterize fungal communities in a subsurface environment co-contaminated with uranium and nitrate at the watershed scale, and to determine the potential contribution of fungi to contaminant transformation (nitrate attenuation). The abundance, distribution and diversity of fungi in subsurface groundwater samples were determined using quantitative and semi-quantitative molecular techniques, including quantitative PCR of eukaryotic SSU rRNA genes and pyrosequencing of fungal internal transcribed spacer (ITS) regions. Potential bacterial and fungal denitrification was assessed in sediment-groundwater slurries amended with antimicrobial compounds and in fungal pure cultures isolated from subsurface. Our results demonstrate that subsurface fungalmore » communities are dominated by members of the phylum Ascomycota, and a pronounced shift in fungal community composition occurs across the groundwater pH gradient at the field site, with lower diversity observed under acidic (pH < 4.5) conditions. Fungal isolates recovered from subsurface sediments were shown to reduce nitrate to nitrous oxide, including cultures of the genus Coniochaeta that were detected in abundance in pyrosequence libraries of site groundwater samples. Denitrifying fungal isolates recovered from the site were classified, and found to be distributed broadly within the phylum Ascomycota, and within a single genus within the Basidiomycota. Potential denitrification rate assays with sediment-groundwater slurries showed the potential for subsurface fungi to reduce nitrate to nitrous oxide under in situ acidic pH conditions.« less

Watershed-Scale Fungal Community Characterization along a pH Gradient in a Subsurface Environment Cocontaminated with Uranium and Nitrate

PubMed Central

Jasrotia, Puja; Green, Stefan J.; Canion, Andy; Overholt, Will A.; Prakash, Om; Wafula, Denis; Hubbard, Daniela; Watson, David B.; Schadt, Christopher W.; Brooks, Scott C.

2014-01-01

The objective of this study was to characterize fungal communities in a subsurface environment cocontaminated with uranium and nitrate at the watershed scale and to determine the potential contribution of fungi to contaminant transformation (nitrate attenuation). The abundance, distribution, and diversity of fungi in subsurface groundwater samples were determined using quantitative and semiquantitative molecular techniques, including quantitative PCR of eukaryotic small-subunit rRNA genes and pyrosequencing of fungal internal transcribed spacer (ITS) regions. Potential bacterial and fungal denitrification was assessed in sediment-groundwater slurries amended with antimicrobial compounds and in fungal pure cultures isolated from the subsurface. Our results demonstrate that subsurface fungal communities are dominated by members of the phylum Ascomycota, and a pronounced shift in fungal community composition occurs across the groundwater pH gradient at the field site, with lower diversity observed under acidic (pH <4.5) conditions. Fungal isolates recovered from subsurface sediments, including cultures of the genus Coniochaeta, which were detected in abundance in pyrosequence libraries of site groundwater samples, were shown to reduce nitrate to nitrous oxide. Denitrifying fungal isolates recovered from the site were classified and found to be distributed broadly within the phylum Ascomycota and within a single genus of the Basidiomycota. Potential denitrification rate assays with sediment-groundwater slurries showed the potential for subsurface fungi to reduce nitrate to nitrous oxide under in situ acidic pH conditions. PMID:24389927

Relative Abundance and Diversity of Bacterial Methanotrophs at the Oxic-Anoxic Interface of the Congo Deep-Sea Fan.

PubMed

Bessette, Sandrine; Moalic, Yann; Gautey, Sébastien; Lesongeur, Françoise; Godfroy, Anne; Toffin, Laurent

2017-01-01

Sitting at ∼5,000 m water depth on the Congo-Angola margin and ∼760 km offshore of the West African coast, the recent lobe complex of the Congo deep-sea fan receives large amounts of fluvial sediments (3-5% organic carbon). This organic-rich sedimentation area harbors habitats with chemosynthetic communities similar to those of cold seeps. In this study, we investigated relative abundance, diversity and distribution of aerobic methane-oxidizing bacteria (MOB) communities at the oxic-anoxic interface of sedimentary habitats by using fluorescence in situ hybridization and comparative sequence analysis of particulate mono-oxygenase ( pmoA ) genes. Our findings revealed that sedimentary habitats of the recent lobe complex hosted type I and type II MOB cells and comparisons of pmoA community compositions showed variations among the different organic-rich habitats. Furthermore, the pmoA lineages were taxonomically more diverse compared to methane seep environments and were related to those found at cold seeps. Surprisingly, MOB phylogenetic lineages typical of terrestrial environments were observed at such water depth. In contrast, MOB cells or pmoA sequences were not detected at the previous lobe complex that is disconnected from the Congo River inputs.

Distribution of microbial biomass and potential for anaerobic respiration in Hanford Site 300 Area subsurface sediment.

PubMed

Lin, Xueju; Kennedy, David; Peacock, Aaron; McKinley, James; Resch, Charles T; Fredrickson, James; Konopka, Allan

2012-02-01

Subsurface sediments were recovered from a 52-m-deep borehole cored in the 300 Area of the Hanford Site in southeastern Washington State to assess the potential for biogeochemical transformation of radionuclide contaminants. Microbial analyses were made on 17 sediment samples traversing multiple geological units: the oxic coarse-grained Hanford formation (9 to 17.4 m), the oxic fine-grained upper Ringold formation (17.7 to 18.1 m), and the reduced Ringold formation (18.3 to 52 m). Microbial biomass (measured as phospholipid fatty acids) ranged from 7 to 974 pmols per g in discrete samples, with the highest numbers found in the Hanford formation. On average, strata below 17.4 m had 13-fold less biomass than those from shallower strata. The nosZ gene that encodes nitrous oxide reductase (measured by quantitative real-time PCR) had an abundance of 5 to 17 relative to that of total 16S rRNA genes below 18.3 m and <5 above 18.1 m. Most nosZ sequences were affiliated with Ochrobactrum anthropi (97 sequence similarity) or had a nearest neighbor of Achromobacter xylosoxidans (90 similarity). Passive multilevel sampling of groundwater geochemistry demonstrated a redox gradient in the 1.5-m region between the Hanford-Ringold formation contact and the Ringold oxic-anoxic interface. Within this zone, copies of the dsrA gene and Geobacteraceae had the highest relative abundance. The majority of dsrA genes detected near the interface were related to Desulfotomaculum spp. These analyses indicate that the region just below the contact between the Hanford and Ringold formations is a zone of active biogeochemical redox cycling.

Distribution of Microbial Biomass and Potential for Anaerobic Respiration in Hanford Site 300 Area Subsurface Sediment

PubMed Central

Lin, Xueju; Kennedy, David; Peacock, Aaron; McKinley, James; Resch, Charles T.; Fredrickson, James

2012-01-01

Subsurface sediments were recovered from a 52-m-deep borehole cored in the 300 Area of the Hanford Site in southeastern Washington State to assess the potential for biogeochemical transformation of radionuclide contaminants. Microbial analyses were made on 17 sediment samples traversing multiple geological units: the oxic coarse-grained Hanford formation (9 to 17.4 m), the oxic fine-grained upper Ringold formation (17.7 to 18.1 m), and the reduced Ringold formation (18.3 to 52 m). Microbial biomass (measured as phospholipid fatty acids) ranged from 7 to 974 pmols per g in discrete samples, with the highest numbers found in the Hanford formation. On average, strata below 17.4 m had 13-fold less biomass than those from shallower strata. The nosZ gene that encodes nitrous oxide reductase (measured by quantitative real-time PCR) had an abundance of 5 to 17 relative to that of total 16S rRNA genes below 18.3 m and <5 above 18.1 m. Most nosZ sequences were affiliated with Ochrobactrum anthropi (97 sequence similarity) or had a nearest neighbor of Achromobacter xylosoxidans (90 similarity). Passive multilevel sampling of groundwater geochemistry demonstrated a redox gradient in the 1.5-m region between the Hanford-Ringold formation contact and the Ringold oxic-anoxic interface. Within this zone, copies of the dsrA gene and Geobacteraceae had the highest relative abundance. The majority of dsrA genes detected near the interface were related to Desulfotomaculum spp. These analyses indicate that the region just below the contact between the Hanford and Ringold formations is a zone of active biogeochemical redox cycling. PMID:22138990

The Role of Subsurface Water in Carving Hesperian Amphitheater-Headed Valleys

NASA Astrophysics Data System (ADS)

Lapotre, M. G. A.; Lamb, M. P.

2017-12-01

Groundwater sapping may play a role in valley formation in rare cases on Earth, typically in sand or weakly cemented sandstones. Small-scale valleys resulting from groundwater seepage in loose sand typically have amphitheater-shaped canyon heads with roughly uniform widths. By analogy to terrestrial sapping valleys, Hesperian-aged amphitheater canyons on Mars have been interpreted to result from groundwater sapping, with implications for subsurface and surface water flows on ancient Mars. However, other studies suggest that martian amphitheater canyons carved in fractured rock may instead result from large overland floods, by analogy to dry cataracts in scabland terrains in the northwestern U.S. Understanding the formation of bedrock canyons is critical to our understanding of liquid water reservoirs on ancient Mars. Can groundwater sapping carve canyons in substrates other than sand? There is currently no model to predict the necessary conditions for groundwater to carve canyons in substrates ranging from loose sediment of various sizes to competent rock. To bridge this knowledge gap, we formulate a theoretical model coupling equations of groundwater flow and sediment transport that can be applied to a wide range of substrates. The model is used to infer whether groundwater sapping could have carved canyons in the absence of overland flows, and requires limited inputs that are measureable in the field or from orbital images. Model results show that sapping erosion is capable of forming canyons, but only in loose well-sorted sand. Coarser sediment is more permeable, but more difficult to transport. Finer sediment is more easily transported, but lower permeability precludes the necessary seepage discharge. Finally, fractured rock is highly permeable, but seepage discharges are far below those required to transport typical talus boulders. Using orbiter-based lithological constraints, we conclude that canyons near Echus Chasma are carved into bedrock and therefore required high-discharge overland flow during formation. These results have implications for Hesperian hydrology; while water volumes to carve sapping versus flood canyons need not be significantly different, erosion rates are orders of magnitude faster in the flood scenario, implying brief periods of abundant surface water on Hesperian Mars.

Lignin geochemistry of sediments from the Narragansett Bay Estuary

NASA Astrophysics Data System (ADS)

Requejo, A. G.; Brown, John S.; Boehm, Paul D.

1986-12-01

Cupric oxide oxidation has been employed to characterize the lignin geochemistry of Narragansett Bay sediments. Lignin concentrations throughout the estuary are low when expressed on a carbon-normalized basis, but can be characterized as enriched when expressed on a mass-normalized basis. This implies substantial dilution of the sedimentary lignin by inputs of lignin-poor carbon. Lignin concentrations do not correlate with the 13C isotopic composition of the sedimentary organic matter. These results are consistent with a sediment lignin component consisting of varying amounts of vascular plant debris and lignin-depleted organic matter, the latter originating from both marine (planktonic) and terrestrial (uncharacterized) sources. Compositional plots of lignin-derived phenols show that sediments in the upper estuary are influenced to a greater extent by gymnosperm lignin sources than those in the mid-and lower estuary. Given the extent to which the upper estuary is affected by pollution sources, inputs from anthropogenic discharges are the most likely cause of these compositional differences. However, an evaluation of processed paper products as an "anthropogenic" lignin source indicates that the lignin content of these materials is insufficient to account for the levels found in the sediments. Subsurface lignin compositions at an upper estuary site reveal that lignin originating from the inferred anthropogenic sources disappears at a depth shallower than that which would be expected based on the distribution of other trace organic pollutants (hydrocarbons and several synthetic organic compounds). We speculate that differences in either the depositional history or the degree of preservation of these two compound classes are responsible for the observed trends.

Age determination and provenance of sandy sediments possibly hosting gas hydrate in the eastern margin of Japan Sea

NASA Astrophysics Data System (ADS)

Uchida, T.; Takashima, I.; Sasaki, S.; Matsumoto, R.

2012-12-01

In 2010 the MD179 project was undertaken by the Marion Dufresne aiming at recovery of deep seated gas and gas hydrate, methane induced carbonate, and deep sediments in order to develop the geologic model of gas hydrate accumulation and evaluate the possible environmental impact of gas hydrate for the last glacial-interglacial cycles. Sediment samples below the seafloor were obtained in the Umitaka Spur, Joetsu Channel, Toyama Trough, Japan Basin, Nishi Tsugaru and Okushiri Ridge areas by the cruise. Small amounts of sandy sediment have been retrieved as thin intercalations in Pleistocene and Holocene silty layers, where trace fossils and strong bioturbations are commonly observed. Those sandy sediments consist of very fine- to fine-grained sand grains, and are sometimes tuffaceous. Pore-size distribution measurements and thin-section observations of these arenite sands were carried out, which indicates that porosities of silty sediments are around 50 % but those of arenites range from 42 to 52 %, of which mean pore sizes and permeabilities are larger than those of silty sediments. These coarser sediments might have been transported approximately around 3 to 30 ka according to the tephra ages, where supplying sediments might have not been abundant due to sea level fluctuation during the Pleistocene ice age. While the presence of gas hydrate in intergranular pores of arenite sands has not been confirmed, the soupy occurrence in recovered sediments may strongly indicate the presence of gas hydrate filling the intergranular pore system of arenite sands that is called pore-space hydrates. They have been recognized till now in the Mallik as well as in the Nankai Trough areas, which are considered to be common even in the subsurface sandy sediments at the eastern margin of Japan Sea. Time of deposition of coarse-grained sediments can be recognized by the thermoluminescence (TL) dating method. The TL dating works on the principle that materials containing naturally occurring radioactive isotopes such as uranium, thorium or potassium are subject to low levels of radiation. Measurements of TL dating have been completed only for seven samples, which indicate 48 to 980 ka in age. Additionally they usually provide information about the provenance and the sedimentary paleoenvironment when the sediments deposited. The TL emission spectra along temperature increase from 100 to 400 degree C are divided into two types; the unimodal type and the bimodal type, which may indicate the histories of sediment transportation and their provenances. This study was performed as a part of the MH21 Research Consortium on methane hydrate in Japan.

A record of recent change in terrestrial sedimentation in a coral-reef environment, La Parguera, Puerto Rico: a response to coastal development?

PubMed

Ryan, K E; Walsh, J P; Corbett, D R; Winter, A

2008-06-01

Increased sediment flux to the coastal ocean due to coastal development is considered a major threat to the viability of coral reefs. A change in the nature of sediment supply and storage has been identified in a variety of coastal settings, particularly in response to European colonization, but sedimentation around reefs has received less attention. This research examines the sedimentary record adjacent to a coastal village that has experienced considerable land-use change over the last few decades. Sediment cores were analyzed to characterize composition and sediment accumulation rates. Sedimentation rates decreased seaward across the shelf from 0.85 cm y(-1) in a nearshore bay to 0.19 cm y(-1) in a fore-reef setting. Data reflected a significant (up to 2x) increase over the last approximately 80 years in terrestrial sediment accumulating in the back-reef setting, suggesting greater terrestrial sediment flux to the area. Reef health has declined, and increased turbidity is believed to be an important impact, particularly when combined with additional stressors.

New Interpretations of the Rayn Anticlines in the Arabian Basin Inferred from Gravity Modelling

NASA Astrophysics Data System (ADS)

AlMogren, S. M.; Mukhopadhyay, M.

2014-12-01

The Ryan Anticlines comprise of a regularly-spaced set of super-giant anticlines oriented NNW, developed due to E-W compression in the Arabian Basin. Most prominent of these being: the Ghawar Anticline, followed by the Summan, Khurais Anticlines and Qatar Arch. Gravity anomaly is largely characteristic for both Ryan Anticlines and its smaller size version the Jinadriah Anticline in the Riyadh Salt Basin. It displays a bipolar gravity field - a zone of gravity high running along the fold axis that is flanked by asymmetric gravity lows. Available structural models commonly infer structural uplift for the median gravity high but ignore the flanking lows. Here we interpret the bipolar gravity anomaly due primarily to such anticline structures, while, the flanking gravity lows are due to greater sediment thickness largely compacted and deformed over the basement depressions. Further complexities are created due to the salt layer and its migration at the lower horizons of sediment strata. Such diagnostic gravity anomaly pattern is taken here as an evidence for basement tectonics due to prevailing crustal dynamics in the Arabian Basin. Density inversion provides details on the subsurface density variation due to the folding and structural configuration for the sediment layers, including the salt layer, affected by basement deformation. This interpretation is largely supported by gravity forward and inversion models given in the present study what is partly constrained by the available seismic, MT and deep resistivity lines and surface geologic mapping. Most of the oil-gas fields in this part of the Arabian Basin are further known for salt diapirism. In this study the gravity interpretation help in identification of salt diapirism directly overlying the basement is firstly given here for Jinadriah Anticline; that is next extended to a regional geologic cross-section traversing the Ryan Anticlines to infer probable subsurface continuation of salt diapirs directly overlying the metamorphosed basement, sediment deformation pattern skirting the anticlines as well as their relationship of faulting to basement tectonics.

Aligning and synchronization of MIS5 proxy records from Lake Ohrid (FYROM) with independently dated Mediterranean archives: implications for DEEP core chronology

NASA Astrophysics Data System (ADS)

Zanchetta, Giovanni; Regattieri, Eleonora; Giaccio, Biagio; Wagner, Bernd; Sulpizio, Roberto; Francke, Alex; Vogel, Hendrik; Sadori, Laura; Masi, Alessia; Sinopoli, Gaia; Lacey, Jack H.; Leng, Melanie J.; Leicher, Niklas

2016-05-01

The DEEP site sediment sequence obtained during the ICDP SCOPSCO project at Lake Ohrid was dated using tephrostratigraphic information, cyclostratigraphy, and orbital tuning through the marine isotope stages (MIS) 15-1. Although this approach is suitable for the generation of a general chronological framework of the long succession, it is insufficient to resolve more detailed palaeoclimatological questions, such as leads and lags of climate events between marine and terrestrial records or between different regions. Here, we demonstrate how the use of different tie points can affect cyclostratigraphy and orbital tuning for the period between ca. 140 and 70 ka and how the results can be correlated with directly/indirectly radiometrically dated Mediterranean marine and continental proxy records. The alternative age model presented here shows consistent differences with that initially proposed by Francke et al. (2015) for the same interval, in particular at the level of the MIS6-5e transition. According to this new age model, different proxies from the DEEP site sediment record support an increase of temperatures between glacial to interglacial conditions, which is almost synchronous with a rapid increase in sea surface temperature observed in the western Mediterranean. The results show how a detailed study of independent chronological tie points is important to align different records and to highlight asynchronisms of climate events. Moreover, Francke et al. (2016) have incorporated the new chronology proposed for tephra OH-DP-0499 in the final DEEP age model. This has reduced substantially the chronological discrepancies between the DEEP site age model and the model proposed here for the last glacial-interglacial transition.

Eruption of a deep-sea mud volcano triggers rapid sediment movement.

PubMed

Feseker, Tomas; Boetius, Antje; Wenzhöfer, Frank; Blandin, Jerome; Olu, Karine; Yoerger, Dana R; Camilli, Richard; German, Christopher R; de Beer, Dirk

2014-11-11

Submarine mud volcanoes are important sources of methane to the water column. However, the temporal variability of their mud and methane emissions is unknown. Methane emissions were previously proposed to result from a dynamic equilibrium between upward migration and consumption at the seabed by methane-consuming microbes. Here we show non-steady-state situations of vigorous mud movement that are revealed through variations in fluid flow, seabed temperature and seafloor bathymetry. Time series data for pressure, temperature, pH and seafloor photography were collected over 431 days using a benthic observatory at the active Håkon Mosby Mud Volcano. We documented 25 pulses of hot subsurface fluids, accompanied by eruptions that changed the landscape of the mud volcano. Four major events triggered rapid sediment uplift of more than a metre in height, substantial lateral flow of muds at average velocities of 0.4 m per day, and significant emissions of methane and CO₂ from the seafloor.

Eruption of a deep-sea mud volcano triggers rapid sediment movement

PubMed Central

Feseker, Tomas; Boetius, Antje; Wenzhöfer, Frank; Blandin, Jerome; Olu, Karine; Yoerger, Dana R.; Camilli, Richard; German, Christopher R.; de Beer, Dirk

2014-01-01

Submarine mud volcanoes are important sources of methane to the water column. However, the temporal variability of their mud and methane emissions is unknown. Methane emissions were previously proposed to result from a dynamic equilibrium between upward migration and consumption at the seabed by methane-consuming microbes. Here we show non-steady-state situations of vigorous mud movement that are revealed through variations in fluid flow, seabed temperature and seafloor bathymetry. Time series data for pressure, temperature, pH and seafloor photography were collected over 431 days using a benthic observatory at the active Håkon Mosby Mud Volcano. We documented 25 pulses of hot subsurface fluids, accompanied by eruptions that changed the landscape of the mud volcano. Four major events triggered rapid sediment uplift of more than a metre in height, substantial lateral flow of muds at average velocities of 0.4 m per day, and significant emissions of methane and CO2 from the seafloor. PMID:25384354

Impact of clay minerals on sulfate-reducing activity in aquifers

USGS Publications Warehouse

Wong, D.; Suflita, J.M.; McKinley, J.P.; Krumholz, L.R.

2004-01-01

Previous studies have shown that sulfate-reduction activity occurs in a heterogeneous manner throughout the terrestrial subsurface. Low-activity regions are often observed in the presence of clay minerals. Here we report that clays inhibit sulfate reduction activity in sediments and in a pure culture of Desulfovibriovulgaris. Clay minerals including bentonite and kaolinite inhibited sulfate reduction by 70–90% in sediments. Intact clays and clay colloids or soluble components, capable of passing through a 0.2-µm filter, were also inhibitory to sulfate-reducing bacteria. Other adsorbent materials, including anion or cation exchangers and a zeolite, did not inhibit sulfate reduction in sediments, suggesting that the effect of clays was not due to their cation-exchange capacity. We observed a strong correlation between the Al2O3content of clays and their relative ability to inhibit sulfate reduction in sediments (r2 = 0.82). This suggested that inhibition might be a direct effect of Al3+ (aq) on the bacteria. We then tested pure aluminum oxide (Al2O3) and showed it to act in a similar manner to clay. As dissolved aluminum is known to be toxic to a variety of organisms at low concentrations, our results suggest that the effects of clay on sulfate-reducing bacteria may be directly due to aluminum. Thus, our experiments provide an explanation for the lack of sulfate-reduction activity in clay-rich regions and presents a mechanism for the effect.

Variations in sedimentological properties in Lake Challa, East Africa: Understanding the source to sink processes

NASA Astrophysics Data System (ADS)

Meyer, Inka; Eloy, Jonas; Verschuren, Dirk; De Batist, Marc

2016-04-01

The clastic mineral fraction of lacustrine sediments has been proven to provide valuable information about sedimentation dynamics within a lake, and it can be used to define distinct terrestrial source areas and transport mechanisms from source to sink. Down-core variation in the properties of the clastic mineral fraction yields indications for changes in terrestrial sediment sources over time. However, in order to use terrestrial proxies in palaeo-environmental reconstruction, we have to understand and quantify the modern conditions of sediment provenance and deposition at the study site. In this study we present data on grain-size distribution, mineralogy and particle shape of the clastic mineral component of lacustrine sediments from Lake Challa, a small freshwater lake of volcanic origin, located on the eastern slope of Mt. Kilimanjaro. Situated close to the equator, it contains a uniquely long and continuous sediment sequence allowing the study of inter-hemispheric climate dynamics. The finely laminated profundal sediments of Lake Challa are characterized by a fine-grained texture and are mainly composed of organic matter, biogenic silica and authigenic carbonate, with a relatively minor component of detrital mineral that can either originate from erosion of the steep volcanic crater walls or was mobilized by wind from unvegetated areas of the surrounding scrub savannah landscape. In order to distinguish between these two sources of terrestrial sediment input (i.e., local run-off versus distant aeolian) into Lake Challa, and to map out differences in sediment properties, samples were investigated from profundal surface sediments and short cores, as well as on-shore soils from several locations around the lake and from beyond the crater catchment. Variation in grain-size distribution and mineralogy can be linked to distinct terrestrial sources, whereas the shape of single particles gives additional information about transport dynamics. In future, the results from this study will be applied to the down-core record of Lake Challa to reconstruct climate-driven changes in terrigenous sediment input over time.

On the non-uniqueness of the hydro-geomorphic responses in a zero-order catchment with respect to soil moisture

NASA Astrophysics Data System (ADS)

Kim, Jongho; Dwelle, M. Chase; Kampf, Stephanie K.; Fatichi, Simone; Ivanov, Valeriy Y.

2016-06-01

This study advances mechanistic interpretation of predictability challenges in hydro-geomorphology related to the role of soil moisture spatial variability. Using model formulations describing the physics of overland flow, variably saturated subsurface flow, and erosion and sediment transport, this study explores (1) why a basin with the same mean soil moisture can exhibit distinctly different spatial moisture distributions, (2) whether these varying distributions lead to non-unique hydro-geomorphic responses, and (3) what controls non-uniqueness in relation to the response type. Two sets of numerical experiments are carried out with two physically-based models, HYDRUS and tRIBS+VEGGIE+FEaST, and their outputs are analyzed with respect to pre-storm moisture state. The results demonstrate that distinct spatial moisture distributions for the same mean wetness arise because near-surface soil moisture dynamics exhibit different degrees of coupling with deeper-soil moisture and the process of subsurface drainage. The consequences of such variations are different depending on the type of hydrological response. Specifically, if the predominant runoff response is of infiltration excess type, the degree of non-uniqueness is related to the spatial distribution of near-surface moisture. If runoff is governed by subsurface stormflow, the extent of deep moisture contributing area and its "readiness to drain" determine the response characteristics. Because the processes of erosion and sediment transport superimpose additional controls over factors governing runoff generation and overland flow, non-uniqueness of the geomorphic response can be highly dampened or enhanced. The explanation is sediment composed by multi-size particles can alternate states of mobilization or surface shielding and the transient behavior is inherently intertwined with the availability of mobile particles. We conclude that complex nonlinear dynamics of hydro-geomorphic processes are inherent expressions of physical interactions. As complete knowledge of watershed properties, states, or forcings will always present the ultimate, if ever resolvable, challenge, deterministic predictability will remain handicapped. Coupling of uncertainty quantification methods and space-time physics-based approaches will need to evolve to facilitate mechanistic interpretations and informed practical applications.

Probing Metabolic Activity of Deep Subseafloor Life with NanoSIMS

NASA Astrophysics Data System (ADS)

Morono, Y.; Terada, T.; Itoh, M.; Inagaki, F.

2014-12-01

There are very few natural environments where life is absent in the Earth's surface biosphere. However, uninhabitable region is expected to be exist in the deep subsurface biosphere, of which extent and constraining factor(s) have still remained largly unknown. Scientific ocean drilling have revealed that microbial communities in sediments are generally phylogenetically distinct from known spieces isolated from the Earth's surface biosphere, and hence metabolic functions of the deep subseafloor life remain unknown. In addition, activity of subseafloor microbial cells are thought to be extraordinally slow, as indicated by limited supply of neutrient and energy substrates. To understand the limits of the Earth's subseafloor biosphere and metabolic functions of microbial populations, detection and quantification of the deeply buried microbial cells in geological habitats are fundamentary important. Using newly developed cell separation techniques as well as an discriminative cell detection system, the current quantification limit of sedimentary microbial cells approaches to 102 cells/cm3. These techniques allow not only to assess very small microbial population close to the subsurface biotic fringe, but also to separate and sort the target cells using flow cytometric cell sorter. Once the deep subseafloor microbial cells are detached from mineral grains and sorted, it opens new windows to subsequent molecular ecological and element/isotopic analyses. With a combined use of nano-scale secondary ion masspectrometry (NanoSIMS) and stable isotope-probing techniques, it is possible to detect and measure activity of substrate incorporation into biomass, even for extremely slow metabolic processes such as uncharacteriszed deep subseafloor life. For example, it was evidenced by NanoSIMS that at least over 80% of microbial cells at ~200 meters-deep, 460,000-year-old sedimentary habitat are indeed live, which substrate incooporation was found to be low (10-15 gC/cell/day) even under the lab incubation condition. Also microbial activity in ultraoligotrophic biosphere samples such as the South Pacific Gyre (i.e., IODP Expeditions 329) will be shown. Our results demonstrates metabolic potential of microbes that have been survived for geological timescale in extremely starved condition.

[Microbes on the edge of global biosphere].

PubMed

Naganuma, T

2000-12-01

The search for life on the edge of global biosphere is a frontier to bridge conventional bio/ecology and exo/astrobiology. This communication reviews the foci of microbiological studies on the inhabitants of the selected "edges", i.e., deep-sea, deep subsurface and Antarctic habitats. The deep-sea is characterized as the no-light (non-photosynthetic) habitat, and the primary production is mostly due to the chemosynthetic autotrophy at the hydrothermal vents and methane-rich seeps. Formation of the chemosynthesis-dependent animal communities in the deep leads to the idea that such communities may be found in "ocean" of the Jovian satellite, Europa. The oxygen minimal layer (OML) in mid-water provides another field of deep-sea research. Modern OML is a relatively thin layer, found between the water depth of 200 and 1000 m, but was much thicker during the periods of oceanic anoxia events (OAEs) in the past. The history of oceanic biosphere is regarded as the cycle of OAE and non-OAE periods, and the remnants of the past OAEs may be seen in the modem OML. Anoxic (no-O2) condition is also characteristic of deep subsurface biosphere. Microorganisms in deep subsurface biosphere exploit every available oxidant, or terminal electron acceptor (TEA), for anaerobic respiration. Sulfate, nitrate, iron (III) and CO2 are the representative TEAs in the deep subsurface. Subsurface of hydrothermal vents, or sub-vent biosphere, may house brine (high salt) habitats and halophilic microorganisms. Some sub-vent halophiles were phylogenetically closely similar to the ones found in the Antarctic habitats which are extremely dry by the liophilizing climate. Below the 3000-4000 m-thick glacier on Antarctica, there have been >70 lakes with liquid water located. One of such sub-glacial lakes, Lake Vostok, has been a target of "life in extreme environments" and is about to be drill-penetrated for microbiological studies. These 'microbiological platforms' will provide new knowledge about the diversity and potential of the Earth's life and facilitate the capability of astrobiologial exploration.

Heat Stress Dictates Microbial Lipid Composition along a Thermal Gradient in Marine Sediments

PubMed Central

Sollich, Miriam; Yoshinaga, Marcos Y.; Häusler, Stefan; Price, Roy E.; Hinrichs, Kai-Uwe; Bühring, Solveig I.

2017-01-01

Temperature exerts a first-order control on microbial populations, which constantly adjust the fluidity and permeability of their cell membrane lipids to minimize loss of energy by ion diffusion across the membrane. Analytical advances in liquid chromatography coupled to mass spectrometry have allowed the detection of a stunning diversity of bacterial and archaeal lipids in extreme environments such as hot springs, hydrothermal vents and deep subsurface marine sediments. Here, we investigated a thermal gradient from 18 to 101°C across a marine sediment field and tested the hypothesis that cell membrane lipids provide a major biochemical basis for the bioenergetics of archaea and bacteria under heat stress. This paper features a detailed lipidomics approach with the focus on membrane lipid structure-function. Membrane lipids analyzed here include polar lipids of bacteria and polar and core lipids of archaea. Reflecting the low permeability of their ether-linked isoprenoids, we found that archaeal polar lipids generally dominate over bacterial lipids in deep layers of the sediments influenced by hydrothermal fluids. A close examination of archaeal and bacterial lipids revealed a membrane quandary: not only low permeability, but also increased fluidity of membranes are required as a unified property of microbial membranes for energy conservation under heat stress. For instance, bacterial fatty acids were composed of longer chain lengths in concert with higher degree of unsaturation while archaea modified their tetraethers by incorporation of additional methyl groups at elevated sediment temperatures. It is possible that these configurations toward a more fluidized membrane at elevated temperatures are counterbalanced by the high abundance of archaeal glycolipids and bacterial sphingolipids, which could reduce membrane permeability through strong intermolecular hydrogen bonding. Our results provide a new angle for interpreting membrane lipid structure-function enabling archaea and bacteria to survive and grow in hydrothermal systems. PMID:28878741

Fe-oxide grain coatings support bacterial Fe-reducing metabolisms in 1.7−2.0 km-deep subsurface quartz arenite sandstone reservoirs of the Illinois Basin (USA)

PubMed Central

Dong, Yiran; Sanford, Robert A.; Locke, Randall A.; Cann, Isaac K.; Mackie, Roderick I.; Fouke, Bruce W.

2014-01-01

The Cambrian-age Mt. Simon Sandstone, deeply buried within the Illinois Basin of the midcontinent of North America, contains quartz sand grains ubiquitously encrusted with iron-oxide cements and dissolved ferrous iron in pore-water. Although microbial iron reduction has previously been documented in the deep terrestrial subsurface, the potential for diagenetic mineral cementation to drive microbial activity has not been well studied. In this study, two subsurface formation water samples were collected at 1.72 and 2.02 km, respectively, from the Mt. Simon Sandstone in Decatur, Illinois. Low-diversity microbial communities were detected from both horizons and were dominated by Halanaerobiales of Phylum Firmicutes. Iron-reducing enrichment cultures fed with ferric citrate were successfully established using the formation water. Phylogenetic classification identified the enriched species to be related to Vulcanibacillus from the 1.72 km depth sample, while Orenia dominated the communities at 2.02 km of burial depth. Species-specific quantitative analyses of the enriched organisms in the microbial communities suggest that they are indigenous to the Mt. Simon Sandstone. Optimal iron reduction by the 1.72 km enrichment culture occurred at a temperature of 40°C (range 20–60°C) and a salinity of 25 parts per thousand (range 25–75 ppt). This culture also mediated fermentation and nitrate reduction. In contrast, the 2.02 km enrichment culture exclusively utilized hydrogen and pyruvate as the electron donors for iron reduction, tolerated a wider range of salinities (25–200 ppt), and exhibited only minimal nitrate- and sulfate-reduction. In addition, the 2.02 km depth community actively reduces the more crystalline ferric iron minerals goethite and hematite. The results suggest evolutionary adaptation of the autochthonous microbial communities to the Mt. Simon Sandstone and carries potentially important implications for future utilization of this reservoir for CO2 injection. PMID:25324834

The stable carbon isotope biogeochemistry of acetate and other dissolved carbon species in deep subseafloor sediments at the northern Cascadia Margin

USGS Publications Warehouse

Heuer, Verena B.; Pohlman, John W.; Torres, Marta E.; Elvert, Marcus; Hinrichs, Kai-Uwe

2009-01-01

Ocean drilling has revealed the existence of vast microbial populations in the deep subseafloor, but to date little is known about their metabolic activities. To better understand the biogeochemical processes in the deep biosphere, we investigate the stable carbon isotope chemistry of acetate and other carbon-bearing metabolites in sediment pore-waters. Acetate is a key metabolite in the cycling of carbon in anoxic sediments. Its stable carbon isotopic composition provides information on the metabolic processes dominating acetate turnover in situ. This study reports our findings for a methane-rich site at the northern Cascadia Margin (NE Pacific) where Expedition 311 of the Integrated Ocean Drilling Program (IODP) sampled the upper 190 m of sediment. At Site U1329, δ13C values of acetate span a wide range from −46.0‰ to −11.0‰ vs. VPDB and change systematically with sediment depth. In contrast, δ13C values of both the bulk dissolved organic carbon (DOC) (−21.6 ± 1.3‰ vs. VPDB) and the low-molecular-weight compound lactate (−20.9 ± 1.8‰ vs. VPDB) show little variability. These species are interpreted to represent the carbon isotopic composition of fermentation products. Relative to DOC, acetate is up to 23.1‰ depleted and up to 9.1‰ enriched in 13C. Broadly, 13C-depletions of acetate relative to DOC indicate flux of carbon from acetogenesis into the acetate pool while 13C-enrichments of pore-water acetate relative to DOC suggest consumption of acetate by acetoclastic methanogenesis. Isotopic relationships between acetate and lactate or DOC provide new information on the carbon flow and the presence and activity of specific functional microbial communities in distinct biogeochemical horizons of the sediment. In particular, they suggest that acetogenic CO2-reduction can coexist with methanogenic CO2-reduction, a notion contrary to the hypothesis that hydrogen levels are controlled by the thermodynamically most favorable electron-accepting process. Further, the isotopic relationship suggests a relative increase in acetate flow to acetoclastic methanogenesis with depth although its contribution to total methanogenesis is probably small. Our study demonstrates how the stable carbon isotope biogeochemistry of acetate can be used to identify pathways of microbial carbon turnover in subsurface environments. Our observations also raise new questions regarding the factors controlling acetate turnover in marine sediments.

Heavy metal tolerance in the psychrotolerant Cryptococcus sp. isolated from deep-sea sediments of the Central Indian Basin.

PubMed

Singh, Purnima; Raghukumar, Chandralata; Parvatkar, Rajesh Ramnath; Mascarenhas-Pereira, M B L

2013-03-01

A deep-sea isolate of the psychrotolerant yeast Cryptococcus sp. (NIOCC#PY13) obtained from polymetallic nodule-bearing sediments of the Central Indian Basin was examined for its capacity to grow in the presence of various concentrations of the heavy metal salts i.e., ZnSO4 , CuSO4 , Pb(CH3 COO)2 and CdCl2 . It demonstrated considerable growth in the presence of 100 mg/l concentrations of the above-mentioned four heavy metal salts both at 30°C and 15°C. This strain tolerated comparatively higher levels of these four metal salts than other deep-sea and terrestrial yeast isolates belonging to Cryptococcus, Rhodotorula, Rhodosporidium and Sporidiobolus spp. Optimum pH for growth of this isolate was in the range of 6-8 in the presence of heavy metal salts at these two temperatures. Scanning electron microscopic (SEM) studies exhibited altered cell surface morphology of the cells under the influence of heavy metals compared to that with control. The adsorption of heavy metals to the cells was demonstrated by FTIR and EDAX analysis. As evidenced by atomic absorption spectrophotometric (AAS) analysis, about 30-90% of the heavy metals were removed from the culture supernatant after 4 days of growth at 30°C. This deep-sea yeast isolate appears to be a potential candidate for bioremediation of metal-contaminated sites. Moreover, its metal tolerance properties provide a significant insight into its ecological role and adaptations to growth in such extreme conditions. Copyright © 2013 John Wiley & Sons, Ltd.

Assessing the High Temperature, High Pressure Subsurface for Anaerobic Methane Oxidation

NASA Astrophysics Data System (ADS)

Harris, R. L.; Bartlett, D.; Byrnes, A. W.; Walsh, K. M.; Lau, C. Y. M.; Onstott, T. C.

2017-12-01

The anaerobic oxidation of methane (AOM) is an important sink in the global methane (CH4) budget. ANMEs are known to oxidize CH4 either independently or in consortia with bacteria, coupling the reduction of electron acceptors such as, SO42-, NO2-, NO3-, Mn4+, or Fe3+. To further constrain the contribution of AOM to the global CH4 budget, it is important to assess unexplored environments where AOM is thermodynamically possible such as the high pressure, high temperature deep biosphere. Provided plausible electron acceptor availability, increased temperature and pCH4 yield favorable Gibbs free energies for AOM reactions and the production of ATP (Fig. 1). To date, only sulfate-dependent AOM metabolism has been documented under high temperature conditions (50-72˚C), and AOM has not been assessed above 10.1 MPa. Given that ANMEs share close phylogenetic and metabolic heritage with methanogens and that the most heat-tolerant microorganism known is a barophilic methanogen, there possibly exist thermophilic ANMEs. Here we describe preliminary results from high pressure, high temperature stable isotope tracer incubation experiments on deep biosphere samples. Deep sub-seafloor sediments collected by IODP 370 from the Nankai Trough (257 - 865 m below seafloor) and deep fracture fluid from South Africa (1339 m below land surface) were incubated anaerobically in hydrostatic pressure vessels at 40 MPa in simulated in situ temperatures (40˚ - 80˚C). Sediments and fracture fluid were incubated in sulfate-free artificial seawater, a 2:98 13CH4:N2 headspace, and treated with one of the potential electron acceptors listed above in addition to kill and endogenous activity (i.e. no added electron acceptor) controls. Stable isotope analysis of dissolved inorganic carbon (DIC) suggests that AOM occurred within 60 days of incubation for all investigated electron acceptors and temperatures except 50˚C. Sulfate-dependent AOM rates are consistent with those previously reported in the literature, while the highest rate of AOM was measured in Nankai Trough sediments from 616 m incubated at 70˚C with 10 mM NO2- (0.44 ± .01 µmol 13CO2 day-1 g-1 dry weight sediment). Further analysis is required to investigate the identities and functional adaptations of CH4-cycling organisms active under high pressure and high temperature.

Vertical distribution of major, minor and trace elements in sediments from mud volcanoes of the Gulf of Cadiz: evidence of Cd, As and Ba fronts in upper layers

NASA Astrophysics Data System (ADS)

Carvalho, Lina; Monteiro, Rui; Figueira, Paula; Mieiro, Cláudia; Almeida, Joana; Pereira, Eduarda; Magalhães, Vítor; Pinheiro, Luís; Vale, Carlos

2018-01-01

Mud volcanoes are feature of the coastal margins where anaerobic oxidation of methane triggers geochemical signals. Elemental composition, percentage of fine particles and loss on ignition were determined in sediment layers of eleven gravity cores retrieved from four mud volcanoes (Sagres, Bonjardim, Soloviev and Porto) and three undefined structures located on the deep Portuguese margin of the Gulf of Cadiz. Calcium was positively correlated to Sr and inversely to Al as well as to most of the trace elements. Vertical profiles of Ba, Cd and As concentrations, and their ratios to Al, in Porto and Soloviev showed pronounced enhancements in the top 50-cm depth. Sub-surface enhancements were less pronounced in other mud volcanoes and were absent in sediments from the structures. These profiles were interpreted as diagenetic enrichments related to the anaerobic oxidation of methane originated from upward methane-rich fluxes. The observed barium fronts were most likely caused by the presence of barite which precipitated at the sulphate-methane transition zone. Cd and As enrichments have probably resulted from successive dissolution/precipitation of sulphides in response to vertical shifts of redox boundaries.

Tropical North Atlantic subsurface warming events as a fingerprint for AMOC variability during Marine Isotope Stage 3

NASA Astrophysics Data System (ADS)

Parker, Andrew O.; Schmidt, Matthew W.; Chang, Ping

2015-11-01

The role of Atlantic Meridional Overturning Circulation (AMOC) as the driver of Dansgaard-Oeschger (DO) variability that characterized Marine Isotope Stage 3 (MIS 3) has long been hypothesized. Although there is ample proxy evidence suggesting that DO events were robust features of glacial climate, there is little data supporting a link with AMOC. Recently, modeling studies and subsurface temperature reconstructions have suggested that subsurface warming across the tropical North Atlantic can be used to fingerprint a weakened AMOC during the deglacial because a reduction in the strength of the western boundary current allows warm salinity maximum water of the subtropical gyre to enter the deep tropics. To determine if AMOC variability played a role during the DO cycles of MIS 3, we present new, high-resolution Mg/Ca and δ18O records spanning 24-52 kyr from the near-surface dwelling planktonic foraminifera Globigerinoides ruber and the lower thermocline dwelling planktonic foraminifera Globorotalia truncatulinoides in Southern Caribbean core VM12-107 (11.33°N, 66.63°W, 1079 m depth). Our subsurface Mg/Ca record reveals abrupt increases in Mg/Ca ratios (the largest equal to a 4°C warming) during the interstadial-stadial transition of most DO events during this period. This change is consistent with reconstructions of subsurface warming events associated with cold events across the deglacial using the same core. Additionally, our data support the conclusion reached by a recently published study from the Florida Straits that AMOC did not undergo significant reductions during Heinrich events 2 and 3. This record presents some of the first high-resolution marine sediment derived evidence for variable AMOC during MIS 3.

δ 13C and δD identification of sources of lipid biomarkers in sediments of Lake Haruna (Japan)

NASA Astrophysics Data System (ADS)

Chikaraishi, Yoshito; Naraoka, Hiroshi

2005-07-01

Organic materials in lacustrine sediments are from multiple terrestrial and aquatic sources. In this study, carbon (δ 13C) and hydrogen isotopic compositions (δD) of phytol, various sterols, and major n-fatty acids in sediments at Lake Haruna, Japan, were determined in their solvent-extractable (free) and saponification-released forms (bound). The δ 13C-δD distributions of these lipid molecules in sediments are compared with those of terrestrial C3 and C4 plants, aquatic C3 plants, and plankton to evaluate their relative contributions. δ 13C-δD of free phytol in sediments is very close to that of phytol in plankton samples, whereas δ 13C-δD of bound phytol in sediments is on a mixing line between terrestrial C3 plant and plankton material. Unlike phytol, no significant δ 13C-δD difference between free and bound forms was found in sterols and n-fatty acids. δ 13C-δD values of algal sterols such as 24-methylcholesta-5,22-dien-3β-ol in sediments are close to those of plankton, whereas δ 13C-δD of multiple-source sterols such as 24-ethylcholest-5-en-3β-ol and of major n-fatty acids such as n-hexadecanoic acid in sediments are between those of terrestrial C3 plants and plankton samples. Thus, δ 13C-δD distributions clearly indicate the specific source contributions of biomarkers preserved in a lacustrine environment. Free phytol and algal sterols can be attributed to phytoplankton, and bound phytol, multiple source sterols, and major n-fatty acids are contributed by both terrestrial C3 plants and phytoplankton.

Phosphatase activities as biosignatures of extant life

NASA Astrophysics Data System (ADS)

Kobayashi, K.; Itoh, Y.; Edazawa, Y.; Moroi, A.; Takano, Y.

It has been recognized that terrestrial biosphere expands to such extreme environments as deep subsurface lithosphere high temperature hot springs and stratosphere Possible extraterrestrial biospheres in Mars Europa and Titan are being discussed Many biosignatures or biomarkers have been proposed to detect microbial activities in such extreme environments Phosphate esters are essential for the terrestrial life since they are constituents of nucleic acids and cell mebranes Thus all the terrestrial organisms have phosphatases that are enzymes catalyzing hydrolysis of phosphate esters We analyzed phosphatase activities in the samples obtained in extreme environments such as submarine hydrothermal systems and discussed whether they can be used as biosignatures for extant life Core samples and chimney samples were collected at the Suiyo Seamount Izu-Bonin Arc the Pacific Ocean in 2001 and 2002 and in South Mariana hydrothermal systems the Pacific Oceanas in 2003 both in a part of the Archaean Park Project Phosphatase activity in solid rock samples was measured spectrometrically by using 25 mM p-nitrophenyl phosphate pH 8 0 or pH 6 5 as a substrate as follows Pulverized samples were incuvated with substrate solution for an hour and then production rate of p-nitrophenol was calculated with absorbance at 410 nm Phosphatase activity in extracts was measured fluorometrically by using 4-methylumberyferryl phosphate as a substrate Concentration of amino acids and their enantiomeric ratio were determined by HPLC after HF digestion of the

Organic sedimentation in modern lacustrine systems: A case study from Lake Malawi, East Africa

USGS Publications Warehouse

Ellis, Geoffrey S.; Barry J. Katz,; Christopher A. Scholz,; Peter K. Swart,

2015-01-01

This study examines the relationship between depositional environment and sedimentary organic geochemistry in Lake Malawi, East Africa, and evaluates the relative significance of the various processes that control sedimentary organic matter (OM) in lacustrine systems. Total organic carbon (TOC) concentrations in recent sediments from Lake Malawi range from 0.01 to 8.80 wt% and average 2.83 wt% for surface sediments and 2.35 wt% for shallow core sediments. Hydrogen index (HI) values as determined by Rock-Eval pyrolysis range from 0 to 756 mg HC g−1 TOC and average 205 mg HC g−1 TOC for surface sediments and 228 mg HC g−1 TOC for shallow core samples. On average, variations in primary productivity throughout the lake may account for ~33% of the TOC content in Lake Malawi sediments (as much as 1 wt% TOC), and have little or no impact on sedimentary HI values. Similarly, ~33% to 66% of the variation in TOC content in Lake Malawi sediments appears to be controlled by anoxic preservation of OM (~1–2 wt% TOC), although some component of the water depth–TOC relationship may be due to physical sediment transport processes. Furthermore, anoxic preservation has a minimal effect on HI values in Lake Malawi sediments. Dilution of OM by inorganic sediment may account for ~16% of variability in TOC content in Lake Malawi sediments (~0.5 wt% TOC). The effect of inputs of terrestrial sediment on the organic character of surface sediments in these lakes is highly variable, and appears to be more closely related to the local depositional environment than the regional flux of terrestrial OM. Total nitrogen and TOC content in surface sediments collected throughout the lake are found to be highly correlated (r2 = 0.95), indicating a well-homogenized source of OM to the lake bottom. The recurring suspension and deposition of terrestrial sediment may account for significant amounts of OM deposited in offshore regions of the lake. This process effectively separates denser inorganic sediment from less dense OM and allows terrestrial OM to preferentially be transported farther offshore. The conclusion is that for the organic carbon content in these regions to be elevated a mixed terrestrial-lacustrine origin is required. The hydrodynamic separation of mineral and organic constituents is most pronounced in regions with shallow bathymetric gradients, consistent with previous findings from Lake Tanganyika.

Subsurface Formation Evaluation on Mars: Application of Methods from the Oil Patch

NASA Astrophysics Data System (ADS)

Passey, Q. R.

2006-12-01

The ability to drill 10- to 100-meter deep wellbores on Mars would allow for evaluation of shallow subsurface formations enabling the extension of current interpretations of the geologic history of this planet; moreover, subsurface access is likely to provide direct evidence to determine if water or permafrost is present. Methodologies for evaluating sedimentary rocks using drill holes and in situ sample and data acquisition are well developed here on Earth. Existing well log instruments can measure K, Th, and U from natural spectral gamma-ray emission, compressional and shear acoustic velocities, electrical resistivity and dielectric properties, bulk density (Cs-137 or Co-60 source), photoelectric absorption of gamma-rays (sensitive to the atomic number), hydrogen index from epithermal and thermal neutron scattering and capture, free hydrogen in water molecules from nuclear magnetic resonance, formation capture cross section, temperature, pressure, and elemental abundances (C, O, Si, Ca, H, Cl, Fe, S, and Gd) using 14 MeV pulsed neutron activation more elements possible with supercooled Ge detectors. Additionally, high-resolution wellbore images are possible using a variety of optical, electrical, and acoustic imaging tools. In the oil industry, these downhole measurements are integrated to describe potential hydrocarbon reservoir properties: lithology, mineralogy, porosity, depositional environment, sedimentary and structural dip, sedimentary features, fluid type (oil, gas, or water), and fluid amount (i.e., saturation). In many cases it is possible to determine the organic-carbon content of hydrocarbon source rocks from logs (if the total organic carbon content is 1 wt% or greater), and more accurate instruments likely could be developed. Since Martian boreholes will likely be drilled without using opaque drilling fluids (as generally used in terrestrial drilling), additional instruments can be used such as high resolution direct downhole imaging and other surface contact measurements (such as IR spectroscopy and x-ray fluorescence). However, such wellbores would require modification of some instruments since conventional drilling fluids often provide the coupling of the instrument sensors to the formation (e.g., sonic velocity and galvanic resistivity measurements). The ability to drill wellbores on Mars opens up new opportunities for exploration but also introduces additional technical challenges. Currently it is not known if all existing terrestrial logging instruments can be miniaturized sufficiently for a shallow Mars wellbore, but the existing well logging techniques and instruments provide a solid framework on which to build a Martian subsurface evaluation program.

A shift of thermokarst lakes from carbon sources to sinks during the Holocene epoch

USGS Publications Warehouse

Walter Anthony, K. M.; Zimov, S. A.; Grosse, G.; Jones, Miriam C.; Anthony, P.; Chapin, F. S.; Finlay, J. C.; Mack, M. C.; Davydov, S.; Frenzel, P.F.; Frolking, S.

2014-01-01

Thermokarst lakes formed across vast regions of Siberia and Alaska during the last deglaciation and are thought to be a net source of atmospheric methane and carbon dioxide during the Holocene epoch1,2,3,4. However, the same thermokarst lakes can also sequester carbon5, and it remains uncertain whether carbon uptake by thermokarst lakes can offset their greenhouse gas emissions. Here we use field observations of Siberian permafrost exposures, radiocarbon dating and spatial analyses to quantify Holocene carbon stocks and fluxes in lake sediments overlying thawed Pleistocene-aged permafrost. We find that carbon accumulation in deep thermokarst-lake sediments since the last deglaciation is about 1.6 times larger than the mass of Pleistocene-aged permafrost carbon released as greenhouse gases when the lakes first formed. Although methane and carbon dioxide emissions following thaw lead to immediate radiative warming, carbon uptake in peat-rich sediments occurs over millennial timescales. We assess thermokarst-lake carbon feedbacks to climate with an atmospheric perturbation model and find that thermokarst basins switched from a net radiative warming to a net cooling climate effect about 5,000 years ago. High rates of Holocene carbon accumulation in 20 lake sediments (47±10 grams of carbon per square metre per year; mean±standard error) were driven by thermokarst erosion and deposition of terrestrial organic matter, by nutrient release from thawing permafrost that stimulated lake productivity and by slow decomposition in cold, anoxic lake bottoms. When lakes eventually drained, permafrost formation rapidly sequestered sediment carbon. Our estimate of about 160petagrams of Holocene organic carbon in deep lake basins of Siberia and Alaska increases the circumpolar peat carbon pool estimate for permafrost regions by over 50 per cent (ref. 6). The carbon in perennially frozen drained lake sediments may become vulnerable to mineralization as permafrost disappears7,8,9, potentially negating the climate stabilization provided by thermokarst lakes during the late Holocene.

Pools and fluxes of organic matter in a boreal landscape: implications for a safety assessment of a repository for nuclear waste.

PubMed

Kumblad, Linda; Söderbäck, Björn; Löfgren, Anders; Lindborg, Tobias; Wijnbladh, Erik; Kautsky, Ulrik

2006-12-01

To provide information necessary for a license application for a deep repository for spent nuclear fuel, the Swedish Nuclear Fuel and Waste Management Co is carrying out site investigations, including extensive studies of different parts of the surface ecosystems, at two sites in Sweden. Here we use the output from detailed modeling of the carbon dynamics in the terrestrial, limnic and marine ecosystems to describe and compare major pools and fluxes of organic matter in the Simpevarp area, situated on the southeast coast of Sweden. In this study, organic carbon is used as a proxy for radionuclides incorporated into organic matter. The results show that the largest incorporation of carbon into living tissue occurs in terrestrial catchments. Carbon is accumulated in soil or sediments in all ecosystems, but the carbon pool reaches the highest values in shallow near-land marine basins. The marine basins, especially the outer basins, are dominated by large horizontal water fluxes that transport carbon and any associated contaminants into the Baltic Sea. The results suggest that the near-land shallow marine basins have to be regarded as focal points for accumulation of radionuclides in the Simpevarp area, as they receive a comparatively large amount of carbon as discharge from terrestrial catchments, having a high NPP and a high detrital accumulation in sediments. These focal points may constitute a potential risk for exposure to humans in a future landscape as, due to post-glacial land uplift, previous accumulation bottoms are likely to be used for future agricultural purposes.

University of Washington's radioecological studies in the Marshall Islands, 1946-1977.

PubMed

Donaldson, L R; Seymour, A H; Nevissi, A E

1997-07-01

Since 1946, personnel from the School of Fisheries, University of Washington (Applied Fisheries Laboratory, 1943-1958; Laboratory of Radiation Biology, 1958-1967; and Laboratory of Radiation Ecology, since 1967), have studied the effects of nuclear detonations and the ensuing radioactivity on the marine and terrestrial environments throughout the Central Pacific. A collection of reports and publications about these activities plus a collection of several thousand samples from these periods are kept at the School of Fisheries. General findings from the surveys show that (1) fission products were prevalent in organisms of the terrestrial environment whereas activation products were prevalent in marine organisms; (2) the best biological indicators of fallout radionuclides by environments were (a) terrestrial-coconuts, land crabs; (b) reef-algae, invertebrates; and (c) marine-plankton, fish. Studies of plutonium and americium in Bikini Atoll showed that during 1971-1977 the highest concentrations of 241Am, 2.85 Bq g(-1) (77 pCi g(-1)) and 239,240Pu, 4.44 Bq g(-1) (120 pCi g(-1)), in surface sediments were found in the northwest part of the lagoon. The concentrations in the bomb craters were substantially lower than these values. Concentrations of soluble and particulate plutonium and americium in surface and deep water samples showed distributions similar to the sediment samples. That is, the highest concentration of these radionuclides in the water column were at locations with highest sediment concentration. Continuous circulation of water in the lagoon and exchange of water with open ocean resulted in removal of 111 G Bq y(-1) (3 Ci y(-1)) 241Am and 222 G Bq y(-1) (6 Ci y(-1)) 239,240Pu into the North Equatorial Current. A summary of the surveys, findings, and the historical role of the Laboratory in radioecological studies of the Marshall Islands are presented.

Structural evolution of Cenozoic basins in northeastern Tunisia, in response to sinistral strike-slip movement on the El Alia-Teboursouk Fault

NASA Astrophysics Data System (ADS)

Bejaoui, Hamida; Aïfa, Tahar; Melki, Fetheddine; Zargouni, Fouad

2017-10-01

This paper resolves the structural complexity of Cenozoic sedimentary basins in northeastern Tunisia. These basins trend NE-SW to ∼ E-W, and are bordered by old fracture networks. Detailed descriptions of the structural features in outcrop and in subsurface data suggest that the El Alia-Teboursouk Fault zone in the Bizerte area evolved through a series of tectonic events. Cross sections, lithostratigraphic correlations, and interpretation of seismic profiles through the basins show evidence for: (i) a Triassic until Jurassic-Early Cretaceous rifting phase that induced lateral variations of facies and strata thicknesses; (ii) a set of faults oriented NE-SW, NW-SE, N-S, and E-W that guided sediment accumulation in pull-apart basins, which were subject to compressive and transpressive deformation during Eocene (Lutetian-Priabonian), Miocene (Tortonian), and Pliocene-Quaternary; and (iii) NNW-SSE to NS contractional events that occurred during the Late Pliocene. Part of the latest phase has been the formation of different synsedimentary folded structures with significant subsidence inversion. Such events have been responsible for the reactivation of inherited faults, and the intrusion of Triassic evaporites, ensuring the role of a slip layer. The combined effects of the different paleoconstraints and halokinetic movements are at the origin of the evolution of these pull-apart basins. The subsurface data suggest that an important fault displacement occurred during the Mesozoic-Cenozoic. The patterns of sediment accumulation in the different basins reflect a high activity of deep ancient faults.

The metatranscriptome of a deep-sea hydrothermal plume is dominated by water column methanotrophs and lithotrophs

PubMed Central

Lesniewski, Ryan A; Jain, Sunit; Anantharaman, Karthik; Schloss, Patrick D; Dick, Gregory J

2012-01-01

Microorganisms mediate geochemical processes in deep-sea hydrothermal vent plumes, which are a conduit for transfer of elements and energy from the subsurface to the oceans. Despite this important microbial influence on marine geochemistry, the ecology and activity of microbial communities in hydrothermal plumes is largely unexplored. Here, we use a coordinated metagenomic and metatranscriptomic approach to compare microbial communities in Guaymas Basin hydrothermal plumes to background waters above the plume and in the adjacent Carmen Basin. Despite marked increases in plume total RNA concentrations (3–4 times) and microbially mediated manganese oxidation rates (15–125 times), plume and background metatranscriptomes were dominated by the same groups of methanotrophs and chemolithoautotrophs. Abundant community members of Guaymas Basin seafloor environments (hydrothermal sediments and chimneys) were not prevalent in the plume metatranscriptome. De novo metagenomic assembly was used to reconstruct genomes of abundant populations, including Marine Group I archaea, Methylococcaceae, SAR324 Deltaproteobacteria and SUP05 Gammaproteobacteria. Mapping transcripts to these genomes revealed abundant expression of genes involved in the chemolithotrophic oxidation of ammonia (amo), methane (pmo) and sulfur (sox). Whereas amo and pmo gene transcripts were abundant in both plume and background, transcripts of sox genes for sulfur oxidation from SUP05 groups displayed a 10–20-fold increase in plumes. We conclude that the biogeochemistry of Guaymas Basin hydrothermal plumes is mediated by microorganisms that are derived from seawater rather than from seafloor hydrothermal environments such as chimneys or sediments, and that hydrothermal inputs serve as important electron donors for primary production in the deep Gulf of California. PMID:22695860

The metatranscriptome of a deep-sea hydrothermal plume is dominated by water column methanotrophs and lithotrophs.

PubMed

Lesniewski, Ryan A; Jain, Sunit; Anantharaman, Karthik; Schloss, Patrick D; Dick, Gregory J

2012-12-01

Microorganisms mediate geochemical processes in deep-sea hydrothermal vent plumes, which are a conduit for transfer of elements and energy from the subsurface to the oceans. Despite this important microbial influence on marine geochemistry, the ecology and activity of microbial communities in hydrothermal plumes is largely unexplored. Here, we use a coordinated metagenomic and metatranscriptomic approach to compare microbial communities in Guaymas Basin hydrothermal plumes to background waters above the plume and in the adjacent Carmen Basin. Despite marked increases in plume total RNA concentrations (3-4 times) and microbially mediated manganese oxidation rates (15-125 times), plume and background metatranscriptomes were dominated by the same groups of methanotrophs and chemolithoautotrophs. Abundant community members of Guaymas Basin seafloor environments (hydrothermal sediments and chimneys) were not prevalent in the plume metatranscriptome. De novo metagenomic assembly was used to reconstruct genomes of abundant populations, including Marine Group I archaea, Methylococcaceae, SAR324 Deltaproteobacteria and SUP05 Gammaproteobacteria. Mapping transcripts to these genomes revealed abundant expression of genes involved in the chemolithotrophic oxidation of ammonia (amo), methane (pmo) and sulfur (sox). Whereas amo and pmo gene transcripts were abundant in both plume and background, transcripts of sox genes for sulfur oxidation from SUP05 groups displayed a 10-20-fold increase in plumes. We conclude that the biogeochemistry of Guaymas Basin hydrothermal plumes is mediated by microorganisms that are derived from seawater rather than from seafloor hydrothermal environments such as chimneys or sediments, and that hydrothermal inputs serve as important electron donors for primary production in the deep Gulf of California.

Pacific Northwest Laboratory annual report for 1993 to the DOE Office of Energy Research. Part 2: Environmental sciences

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1994-04-01

This 1993 Annual Report from Pacific Northwest Laboratory (PNL) to the US DOE describes research in environment and health conducted during fiscal year (FY) 1993. The report is divided into four parts, each in a separate volume. This part, Volume 2, covers Environmental Sciences. The research is directed toward developing a fundamental understanding of subsurface and terrestrial systems as a basis for both managing these critical resources and addressing environmental problems such as environmental restoration and global change. There are sections on Subsurface Science, Terrestrial Science, Technology Transfer, Interactions with Educational Institutions, and Laboratory Directed Research and Development.

The occurrence and distribution of uronic acids and sugar methyl ethers in sediment trap materials and sediments of two coastal marine environments

NASA Astrophysics Data System (ADS)

Bergamaschi, Brian A.; Walters, Jeffrey S.; Hedges, John I.

1999-02-01

Although recent research has indicated that bacteria may contribute an important fraction of biochemical residues in terrestrial and marine environments, it is difficult for geochemists to identify contributions from these ubiquitous and biochemically diverse organisms. Previous studies have suggested uronic acids and O-methyl sugars may be useful indicators of microbial abundance and activity, but have been limited primarily to analyses of a small number of isolated samples. We report here comparative distributions of O-methyl sugars, uronic acids, and aldoses in sediment trap material and sediments from Dabob Bay, WA and nearby Saanich Inlet, BC, where temporal and spatial trends may be used together with well-established patterns in other biochemicals to identify bacterial contributions against the background of other carbohydrate sources. O-methyl sugars and uronic acids were important contributors to the overall flux and burial of polysaccharide material in Dabob Bay and Saanich Inlet, composing ≤12 wt% of the total carbohydrate yields from sediment trap and sediment samples. O-methyl sugars accounted for an average of 5% of the carbohydrate yields from sediment trap materials and sediments, but were found rarely and only in low abundance in vascular plant tissues, phytoplankton, and kelp. In contrast, uronic acids were abundant products of sediment trap material and sediments, as well as vascular plant tissues, where in some cases they predominated among all carbohydrates. Uronic acid abundance in sediment trap material averaged 3% and ranged to >6% of total carbohydrate yields. The persistence of total minor sugar yields in water column collections from Dabob Bay throughout the seasonal cycle indicated they had a primary source that was not directly related to plankton bloom cycles nor pulsed inputs of vascular plant remains. Subsurface maxima in total minor sugar yields (and several individual components) within sediment cores from both sites indicate in situ sedimentary sources. Taken together, the observed environmental distributions strongly suggest that the minor sugar abundances in Dabob Bay and Saanich Inlet were controlled by in situ microbial production.

In situ expression of nifD in Geobacteraceae in subsurface sediments

USGS Publications Warehouse

Holmes, Dawn E.; Nevin, Kelly P.; Lovely, Derek R.

2004-01-01

In order to determine whether the metabolic state of Geobacteraceae involved in bioremediation of subsurface sediments might be inferred from levels of mRNA for key genes, in situ expression of nifD, a highly conserved gene involved in nitrogen fixation, was investigated. When Geobacter sulfurreducens was grown without a source of fixed nitrogen in chemostats with acetate provided as the limiting electron donor and Fe(III) as the electron acceptor, levels of nifD transcripts were 4 to 5 orders of magnitude higher than in chemostat cultures provided with ammonium. In contrast, the number of transcripts of recA and the 16S rRNA gene were slightly lower in the absence of ammonium. The addition of acetate to organic- and nitrogen-poor subsurface sediments stimulated the growth of Geobacteraceae and Fe(III) reduction, as well as the expression of nifD in Geobacteraceae. Levels of nifD transcripts in Geobacteraceae decreased more than 100-fold within 2 days after the addition of 100 μM ammonium, while levels of recA and total bacterial 16S rRNA in Geobacteraceae remained relatively constant. Ammonium amendments had no effect on rates of Fe(III) reduction in acetate-amended sediments or toluene degradation in petroleum-contaminated sediments, suggesting that other factors, such as the rate that Geobacteraceae could access Fe(III) oxides, limited Fe(III) reduction. These results demonstrate that it is possible to monitor one aspect of the in situ metabolic state of Geobacteraceae species in subsurface sediments via analysis of mRNA levels, which is the first step toward a more global analysis of in situ gene expression related to nutrient status and stress response during bioremediation by Geobacteraceae.

Reconstruction of atmospheric trace metals pollution in Southwest China using sediments from a large and deep alpine lake: Historical trends, sources and sediment focusing.

PubMed

Lin, Qi; Liu, Enfeng; Zhang, Enlou; Nath, Bibhash; Shen, Ji; Yuan, Hezhong; Wang, Rong

2018-02-01

Atmospheric pollution, one of the leading environmental problems in South and East Asia, and its impact on the terrestrial environmental quality remain poorly understood particularly in alpine areas where both historical and present-day mining and smelting operations might leave an imprint. Here, we reconstructed atmospheric trace metals pollution during the past century using core sediments from a large and deep alpine lake in Southwest China. The implication of in lake and/or in watershed sediment focusing in pollution quantification is discussed by analyzing 15 sediment cores. Factor analysis and enrichment factor indicated Cd, Pb and Sb as the typical pollutants. Distinct peaks of Pb and Sb pollution were observed around the 1920s, but little Pb pollution was detected in recent decades, different from other studies in similar regions. Cadmium pollution was observed until the mid-1980s synchronized with Sb. The distinctive variations in atmospheric trace metal pollution process in Southwest China highlight the regional and sub-regional sources of metal pollutants, which should be primarily attributed to non-ferrous metal smelting emissions. Both natural and anthropogenic metals showed wide concentration ranges though exhibited similar temporal trends in the 15 cores. Spatial variations of anthropogenic metals were influenced by the in-watershed pollutants remobilization, whereas, natural metals were regulated by the detrital materials in the sub-basin. In-lake sediment focusing had little influence on the spatial distributions of all metals, different from the traditional sediment focusing pattern observed in small lakes. Anthropogenic Cd accumulation in sediments ranged from 1.5 to 10.1mgm -2 in a specific core with an average of 6.5mgm -2 for the entire lake, highlighting that a reliable whole-lake pollutant budget requires an analysis of multiple cores. Our study suggests that the management of aquatic ecosystem health should take the remobilization of in-watershed stored pollutants into consideration especially under increasing human perturbation. Copyright © 2017 Elsevier B.V. All rights reserved.

Spider-mediated flux of PCBs from contaminated sediments to terrestrial ecosystems and potential risks to arachnivorous birds

USGS Publications Warehouse

Walters, D.M.; Mills, M.A.; Fritz, K.M.; Raikow, D.F.

2010-01-01

We investigated aquatic insect utilization and PCB exposure in riparian spiders at the Lake Hartwell Superfund site (Clemson, SC). We sampled sediments, adult chironomids, terrestrial insects, riparian spiders (Tetragnathidae, Araneidae, and Mecynogea lemniscata), and upland spiders (Araneidae) along a sediment contamination gradient. Stable isotopes (?13C, ? 15N) indicated that riparian spiders primarily consumed aquatic insects whereas upland spiders consumed terrestrial insects. PCBs in chironomids (mean 1240 ng/g among sites) were 2 orders of magnitude higher than terrestrial insects (15.2 ng/g), similar to differences between riparian (820?2012 ng/g) and upland spiders (30 ng/g). Riparian spider PCBs were positively correlated with sediment concentrations for all taxa (r2 = 0.44?0.87). We calculated spider-based wildlife values (WVs, the minimum spider PCB concentrations causing physiologically significant doses in consumers) to assess exposure risks for arachnivorous birds. Spider concentrations exceeded WVs for most birds at heavily contaminated sites and were ?14-fold higher for the most sensitive species (chickadee nestlings, Poecile spp.). Spiders are abundant and ubiquitous in riparian habitats, where they depend on aquatic insect prey. These traits, along with the high degree of spatial correlation between spider and sediment concentrations we observed, suggest that they are model indicator species for monitoring contaminated sediment sites and assessing risks associated with contaminant flux into terrestrial ecosystems. ?? This article not subject to U.S. Copyright. Published 2009 by the American Chemical Society.

Halite-clay interplay in the Israeli Messinian

NASA Astrophysics Data System (ADS)

Cohen, Avigdor

1993-08-01

The Mavqi'im Formation in Israel is the equivalent of the evaporite part of the Messinian stage (Upper Miocene). It is found in the subsurface in the offshore with eastward extensions into ancient buried channels in the coastal plain and in the Jordan Rift valley and in a few outcrops southwest of Lake Tiberias. Most of the anhydrite horizons can be used as correlation markers. Lateral facies changes between halite, anhydrite and shales can be traced. This is interpreted as contemporaneous sedimentation in giant marine salt ponds (halite and anhydrite) and in drowned desert valleys and/or salt-marsh coasts (shales with sabkha-like anhydrites). Another type of shale is that directly underflooring halite horizons. It is regarded as deep-water halite facies, in contrast with shallow-water facies where halite overlies gypsum and/or anhydrite. A "twofold bull's-eye model" is proposed, which assumes that either: (a) sedimentation of gypsum and halite was 'separated in space'—i.e., gypsum was deposited in the part of the basin proximal to oceanic inlets or on shallow shelves, whereas halite was deposited in the central deep part of the basin or on its distal edge; or (b) sedimentation of gypsum and halite was not contemporaneous, or 'separated in time'—i.e., in the deep parts of the basin gypsum precipitates were disintegrated by anaerobic bacteria which removed the sulfate. The lower limit of gypsum deposition is considered to be 200 m, which is the lower limit of the photic and wave zones. In the Israeli Messinian there is no difference between the clay minerals of marine and fluvial shales. Differentiation of marine shales from fluvial and mud flat shales is based on their geometry, i.e., thin persistent horizons spreading across the whole area versus thick shale lenses wedging out in 500-1000 m distances. Another consideration is the palynologic and microfauna remains: in the first case the cyst/pollen ratio may be as high as 100, whereas in the second pollen is dominant.

Seasonal variability in particulate matter source and composition to the depositional zone of Baltimore Canyon, U.S. Mid-Atlantic Bight

USGS Publications Warehouse

Prouty, Nancy G.; Mienis, Furu; Campbell, P.; Roark, E. Brendan; Davies, Andrew; Robertson, Craig M.; Duineveld, Gerard; Ross, Steve W.; Rhodes, M.; Demopoulos, Amanda W.J.

2017-01-01

Submarine canyons are often hotspots of biomass and productivity in the deep sea. However, the majority of deep-sea canyons remain poorly sampled. Using a multi-tracer approach, results from a detailed geochemical investigation from a year-long sediment trap deployment reveals details concerning the source, transport, and fate of particulate matter to the depositional zone (1318 m) of Baltimore Canyon on the US Mid-Atlantic Bight (MAB). Both organic biomarker composition (sterol and n-alkanes) and bulk characteristics (δ13C, Δ14C, Chl-a) suggest that on an annual basis particulate matter from marine and terrestrially-derived organic matter are equally important. However, elevated Chlorophyll-a and sterol concentrations during the spring sampling period highlight the seasonal influx of relatively fresh phytodetritus. In addition, the contemporaneous increase in the particle reactive elements cadmium (Cd) and molybdenum (Mo) in the spring suggest increased scavenging, aggregation, and sinking of biomass during seasonal blooms in response to enhanced surface production within the nutricline. While internal waves within the canyon resuspend sediment between 200 and 600 m, creating a nepheloid layer rich in lithogenic material, near-bed sediment remobilization in the canyon depositional zone is minimal. Instead, vertical transport and lateral transport across the continental margin are the dominant processes driving seasonal input of particulate matter. In turn, seasonal variability in deposited particulate organic matter may be linked to benthic faunal composition and ecosystem scale carbon cycling.

Exobiology site selection for future Mars missions: Martian paleolake sediments and terrestrial analogs

NASA Technical Reports Server (NTRS)

Wharton, Robert A., Jr.

1989-01-01

This research was conducted to establish the scientific framework for the exobiological study of sediments on Mars and to encourage the selection of these sedimentary deposits as sampling sites for future Mars missions. A study was completed on the Antarctic Dry Valley Lakes (terrestrial analogs of the purported Martian paleolakes) and their sediments that allowed the development of quantitative models relating environmental factors to the nature of the biological community and sediment forming processes. The publications presented include: (1) Diversity of micro-fungi isolated in an Antarctic dry valley; (2) Lake Hoare, Antarctica--sedimentation through a thick perennial ice cover; (3) The possibility of life on Mars during a water-rich past; (4) An Antarctic research outpost as a model for planetary exploration; (5) Early Martian environments--the Antarctic and other terrestrial analogs; (6) Lipophilic pigments from the benthos of a perennially ice-covered Antarctic lake; and (7) Perennially ice-covered Lake Hoare, Antarctica--physical environment, biology, and sedimentation.

Spider-mediated flux of PCBs from contaminated sediments to terrestrial ecosystems and potential risks to arachnivorous birds

EPA Science Inventory

We investigated aquatic insect utilization and PCB exposure in riparian spiders at the Lake Hartwell superfund site (Clemson, SC , USA). We sampled sediments, adult chironomids, terrestrial insects, riparian spiders (Tetragnathidae, Araneidae, and Mecynogea lemniscata), and upla...

Microbial Diversity in Surface Iron-Rich Aqueous Environments: Implications for Seeking Signs of Life on Mars

NASA Technical Reports Server (NTRS)

Brown, I. I.; Allen, C. C.; Tringe, S. G.; Klatt, C. G.; Bryant, D. A.; Sarkisova, S. A.; Garrison, D. H.; McKay, D. S.

2010-01-01

The success of selecting future landing sites on Mars to discover extinct and/or extant extraterrestrial life is dependent on the correct approximation of available knowledge about terrestrial paleogeochemistry and life evolution to Martian (paleo) geology and geochemistry. It is well known that both Earth and Mars are Fe rich. This widespread occurrence suggests that Fe may have played a key role in early life forms, where it probably served as a key constituent in early prosthetic moieties in many proteins of ancient microbes on Earth and likely Mars. The second critical idea is the premise that Life on Mars could most likely have developed when Mars experienced tectonic activity [1] which dramatically decreased around 1 bin years after Martian creation. After that Martian life could have gone extinct or hibernated in the deep subsurface, which would be expensive to reach in contrast to the successful work of Martian surface rovers. Here we analyze the diversity of microbes in several terrestrial Fe rich surface environments in conjunction with the phylogeny and molecular timing of emergence of those microbes on Earth. Anticipated results should help evaluate future landing sites on Mars in searches for biosignatures.

Critical biogeochemical functions in the subsurface are associated with bacteria from new phyla and little studied lineages

DOE PAGES

Hug, Laura A.; Thomas, Brian C.; Sharon, Itai; ...

2015-07-22

Nitrogen, sulfur and carbon fluxes in the terrestrial subsurface are determined by the intersecting activities of microbial community members, yet the organisms responsible are largely unknown. Metagenomic methods can identify organisms and functions, but genome recovery is often precluded by data complexity. To address this limitation, we developed subsampling assembly methods to re-construct high-quality draft genomes from complex samples. Here, we applied these methods to evaluate the interlinked roles of the most abundant organisms in biogeochemical cycling in the aquifer sediment. Community proteomics confirmed these activities. The eight most abundant organisms belong to novel lineages, and two represent phyla withmore » no previously sequenced genome. Four organisms are predicted to fix carbon via the Calvin Benson Bassham, Wood Ljungdahl or 3-hydroxyproprionate/4-hydroxybutarate pathways. The profiled organisms are involved in the network of denitrification, dissimilatory nitrate reduction to ammonia, ammonia oxidation and sulfate reduction/oxidation, and require substrates supplied by other community members. An ammonium-oxidizing Thaumarchaeote is the most abundant community member, despite low ammonium concentrations in the groundwater. Finally, this organism likely benefits from two other relatively abundant organisms capable of producing ammonium from nitrate, which is abundant in the groundwater. Overall, dominant members of the microbial community are interconnected through exchange of geochemical resources.« less

Vadose zone microbiology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kieft, Thomas L.; Brockman, Fred J.

2001-01-17

The vadose zone is defined as the portion of the terrestrial subsurface that extends from the land surface downward to the water table. As such, it comprises the surface soil (the rooting zone), the underlying subsoil, and the capillary fringe that directly overlies the water table. The unsaturated zone between the rooting zone and the capillary fringe is termed the "intermediate zone" (Chapelle, 1993). The vadose zone has also been defined as the unsaturated zone, since the sediment pores and/or rock fractures are generally not completely water filled, but instead contain both water and air. The latter characteristic results inmore » the term "zone of aeration" to describe the vadose zone. The terms "vadose zone," "unsaturated zone", and "zone of aeration" are nearly synonymous, except that the vadose zone may contain regions of perched water that are actually saturated. The term "subsoil" has also been used for studies of shallow areas of the subsurface immediately below the rooting zone. This review focuses almost exclusively on the unsaturated region beneath the soil layer since there is already an extensive body of literature on surface soil microbial communities and process, e.g., Paul and Clark (1989), Metting (1993), Richter and Markowitz, (1995), and Sylvia et al. (1998); whereas the deeper strata of the unsaturated zone have only recently come under scrutiny for their microbiological properties.« less

Remote sensing science for the Nineties; Proceedings of IGARSS '90 - 10th Annual International Geoscience and Remote Sensing Symposium, University of Maryland, College Park, May 20-24, 1990. Vols. 1, 2, & 3

NASA Technical Reports Server (NTRS)

1990-01-01

Various papers on remote sensing (RS) for the nineties are presented. The general topics addressed include: subsurface methods, radar scattering, oceanography, microwave models, atmospheric correction, passive microwave systems, RS in tropical forests, moderate resolution land analysis, SAR geometry and SNR improvement, image analysis, inversion and signal processing for geoscience, surface scattering, rain measurements, sensor calibration, wind measurements, terrestrial ecology, agriculture, geometric registration, subsurface sediment geology, radar modulation mechanisms, radar ocean scattering, SAR calibration, airborne radar systems, water vapor retrieval, forest ecosystem dynamics, land analysis, multisensor data fusion. Also considered are: geologic RS, RS sensor optical measurements, RS of snow, temperature retrieval, vegetation structure, global change, artificial intelligence, SAR processing techniques, geologic RS field experiment, stochastic modeling, topography and Digital Elevation model, SAR ocean waves, spaceborne lidar and optical, sea ice field measurements, millimeter waves, advanced spectroscopy, spatial analysis and data compression, SAR polarimetry techniques. Also discussed are: plant canopy modeling, optical RS techniques, optical and IR oceanography, soil moisture, sea ice back scattering, lightning cloud measurements, spatial textural analysis, SAR systems and techniques, active microwave sensing, lidar and optical, radar scatterometry, RS of estuaries, vegetation modeling, RS systems, EOS/SAR Alaska, applications for developing countries, SAR speckle and texture.

ICDP Project DeepCHALLA: Reconstructing 250,000 Years of Climate Change and Environmental History on the East African Equator

NASA Astrophysics Data System (ADS)

Wolff, C.; Verschuren, D.; Van Daele, M. E.; Waldmann, N.; Meyer, I.; Lane, C. S.; Van der Meeren, T.; Ombori, T.; Kasanzu, C.; Olago, D.

2017-12-01

Sediments on the bottom of Lake Challa, a 92-m deep crater lake on the border of Kenya and Tanzania near Mt. Kilimanjaro, contain a uniquely long and continuous record of past climate and environmental change in easternmost equatorial Africa. Supported in part by the International Continental Scientific Drilling Programme (ICDP), the DeepCHALLA project has now recovered this sediment record down to 214.8 m below the lake floor, with 100% recovery of the uppermost 121.3 m (the last 160 kyr BP) and ca.85% recovery of the older part of the sequence, down to the lowermost distinct reflector identified in seismic stratigraphy. This acoustic basement represents a ca.2-m thick layer of coarsely laminated, diatom-rich organic mud mixed with volcanic sand and silt deposited 250 kyr ago, overlying an estimated 20-30 m of unsampled lacustrine deposits representing the earliest phase of lake development. Down-hole logging produced profiles of in-situ sediment composition that confer an absolute depth- scale to both the recovered cores and the seismic stratigraphy. An estimated 74% of the recovered sequence is finely laminated (varved), and continuously so over the upper 72.3 m (the last 90 kyr). All other sections display at least cm-scale lamination, demonstrating persistence of a tranquil, profundal depositional environment throughout lake history. The sequence is interrupted only by 32 visible tephra layers 2 to 9 mm thick; and by several dozen fine-grained turbidites up to 108 cm thick, most of which are clearly bracketed between a non-erosive base and a diatom-laden cap. Tie points between sediment markers and the corresponding seismic reflectors support a preliminary age model inferring a near-constant rate of sediment accumulation over at least the last glacial cycle (140 kyr BP to present). This great time span combined with the exquisite temporal resolution of the Lake Challa sediments provides great opportunities to study past tropical climate dynamics at both short (inter-annual to decadal) and long (glacial-interglacial) time scales; and to assess the multi-faceted impact of this climate change on the region's freshwater resources, the functioning of terrestrial ecosystems, and the history of the African landscape in which modern humans (our species, Homo sapiens) originally evolved and have lived ever since.

Deep sub-seafloor prokaryotes stimulated at interfaces over geological time.

PubMed

Parkes, R John; Webster, Gordon; Cragg, Barry A; Weightman, Andrew J; Newberry, Carole J; Ferdelman, Timothy G; Kallmeyer, Jens; Jørgensen, Bo B; Aiello, Ivano W; Fry, John C

2005-07-21

The sub-seafloor biosphere is the largest prokaryotic habitat on Earth but also a habitat with the lowest metabolic rates. Modelled activity rates are very low, indicating that most prokaryotes may be inactive or have extraordinarily slow metabolism. Here we present results from two Pacific Ocean sites, margin and open ocean, both of which have deep, subsurface stimulation of prokaryotic processes associated with geochemical and/or sedimentary interfaces. At 90 m depth in the margin site, stimulation was such that prokaryote numbers were higher (about 13-fold) and activity rates higher than or similar to near-surface values. Analysis of high-molecular-mass DNA confirmed the presence of viable prokaryotes and showed changes in biodiversity with depth that were coupled to geochemistry, including a marked community change at the 90-m interface. At the open ocean site, increases in numbers of prokaryotes at depth were more restricted but also corresponded to increased activity; however, this time they were associated with repeating layers of diatom-rich sediments (about 9 Myr old). These results show that deep sedimentary prokaryotes can have high activity, have changing diversity associated with interfaces and are active over geological timescales.

Geomorphic and geochemical controls on leaf wax biomarker transport and preservation in alluvial river systems: Rio Bermejo, Argentina

NASA Astrophysics Data System (ADS)

Repasch, M. N.; Sachse, D.; Hovius, N.; Scheingross, J. S.; Szupiany, R. N.

2017-12-01

Rivers are the primary conduits for organic carbon (OC) transfer from vegetation-rich uplands to long-term sinks, and thus are responsible for significant fluxes among different reservoirs of the carbon cycle. Fluxes of terrestrial OC out of river systems are generally less than fluxes into the systems, indicating loss of OC either during active fluvial transport, during residence in the active channel belt, or in older deposits outside of the active channel belt. Sedimentary biomarkers can be used to elucidate the mechanisms of transport, preservation, and/or transformation of OC during its passage from source to sink. In this study we evaluate the influence of fluvial sediment transport on preservation of terrestrial leaf wax n-alkanes. Our natural laboratory is the Rio Bermejo in northern Argentina, which transports sediment and organic matter from the central Andes over 700 km across the foreland basin without input of foreign material from tributaries. Rapid channel migration rates in a region of flexural foreland basin uplift (the forebulge) are responsible for remobilization of floodplain sediment and terrestrial OC. By sampling suspended sediment, river bank sediment, and soil from several locations along the length of the Rio Bermejo, and analyzing the dissolved chemistry, biomarker composition, and compound-specific stable isotopes, we can evaluate the geomorphic and geochemical processes that act to influence the preservation of terrestrial biomarkers through the river system. Data suggest that concentrations of long-chain terrestrial (C25-C33) alkanes decrease downstream, while concentrations of short-chain (C15-C19) alkanes increase. This trend is corroborated by a downstream increase in suspended sediment δ13C values, suggesting a replacement of terrestrial OC by microbial OC. It is likely that microbial degradation is responsible for loss of terrestrial biomarkers as their residence time in the river system increases. Controlled laboratory experiments and analysis of modern and aged river bank sediment samples will determine where and over what timescales leaf wax alkanes are oxidized by microorganisms. With these data, we will be able to quantify the loss of OC during fluvial transit and determine the mechanisms responsible, enabling carbon cycle models to account for these losses.

Organic and Inorganic Carbon in the Rio Tinto (Spain) Deep Subsurface System: a Possible Model for Subsurface Carbon and Lithoautotrophs on Mars.

NASA Astrophysics Data System (ADS)

Bonaccorsi, R.; Stoker, C. R.; MARTE Science Team

2007-12-01

The subsurface is the key environment for searching for life on planets lacking surface life. Subsurface ecosystems are of great relevance to astrobiology including the search for past/present life on Mars. Conditions on the Martian surface do not support biological activity but the subsurface might preserve organics and host subsurface life [1]. A key requirement for the analysis of subsurface samples on Mars is the ability to characterize organic vs. inorganic carbon pools. This information is needed to determine if the sample contains organic material of biological origin and/ or to establish if pools of inorganic carbon can support subsurface biospheres. The Mars Analog Rio Tinto Experiment (MARTE) performed deep drilling of cores i.e., down to 165-m depth, in a volcanically-hosted-massive-sulfide deposit at Rio Tinto, Spain, which is considered an important analog of the Sinus Meridiani site on Mars. Results from MARTE suggest the existence of a relatively complex subsurface life including aerobic and anaerobic chemoautotrophs, and strict anaerobic methanogens sustained by Fe and S minerals in anoxic conditions, which is an ideal model analog for a deep subsurface Martian environment. We report here on the distribution of organic (C-org: 0.01-0.3Wt% and inorganic carbon (IC = 0.01-7.0 Wt%) in a subsurface rock system including weathered/oxidized i.e., gossan, and unaltered pyrite stockwork. Cores were analyzed from 3 boreholes (BH-4, BH-7, and BH-8) that penetrated down to a depth of ~165 m into massive sulfide. Nearsurface phyllosilicate rich-pockets contain the highest amounts of organics (0.3Wt%) [2], while the deeper rocks contain the highest amount of carbonates. Assessing the amount of C pools available throughout the RT subsurface brings key insight on the type of trophic system sustaining its microbial ecosystem (i.e., heterotrophs vs. autotrophs) and the biogeochemical relationships that characterize a new type of subsurface biosphere at RT. This potentially novel biosphere on Earth could be used as a model to test for extant and extinct life on Mars. Furthermore, having found carbonates in an hyperacidic system (pH ~2.3) brings new insights on the possible occurrence of deep carbonates deposits under low-pH condition on Mars. [1] Boston, P.J., et al., 1992. Icarus 95,300-308; Bonaccorsi, Stoker and Sutter, 2007 Accepted with review in Astrobiology.

Hydrodynamic Controls on Archaeal Tetraether Lipid Compositions in Washington Margin Sediments: Insights From Compound-Specific Radiocarbon Measurements

NASA Astrophysics Data System (ADS)

Uchida, M.; Eglinton, T. I.; Montlucon, D. B.; Pearson, A.; Hayes, J. M.

2008-12-01

Continental margin sediments represent a large sink of organic carbon derived from marine and terrestrial sources. Archaeal glycerol dibiphytanyl glycerol tetraether lipids (GDGTs) are derived from both marine and terrestrial sources and have been used both for reconstruction of paleo sea surface temperatures and as an index of terrestrial carbon input to the marine sediments. However, the sources and modes of supply as well as the preservation of GDGTs in marginal sediments are poorly understood. The distribution and deposition of GDGTs is further complicated by hydrodynamic processes. We have analyzed a suite of surface sediment samples collected along a transect from the mouth of the Columbia River, across the Washington Margin, to the Cascadia Basin in the northeast Pacific Ocean. Sediments were separated according to their grain size and hydrodynamic properties, and the organic matter characterized in terms of its bulk elemental, isotopic, and molecular properties. Here we present radiocarbon measurements on individual GDGTs, alkenones, and fatty acids from size-fractionated sediments from shelf and slope sediments, and discuss the results in the context of previous studies of the molecular abundances and isotopic compositions of sedimentary organic matter for in this region. Systematic variations in elemental, isotopic and molecular-level composition are observed across the different particle classes. Moreover, these variations are manifested in the isotopic composition of different molecular markers of both marine and terrestrial sources organic matter. Both marine-derived lipids, including alkenones and marine archaeal tetraethers, and soil microbe-derived tetraether lipids show strong distributional and isotopic variations among the size-fractionated sediments. These variations in terrestrial and marine biomarker properties inform on the sources, particle dynamics, and transport history of organic matter buried on river-influenced continental margins. The implications of these findings for the application of molecular markers as proxies of organic matter input, and on the interpretation of past marine and continental environmental conditions from sedimentary records will also be discussed.

Aerobic and Anaerobic Methanotrophic Communities Associated with Methane Hydrates Exposed on the Seafloor: A High-Pressure Sampling and Stable Isotope-Incubation Experiment

PubMed Central

Case, David H.; Ijiri, Akira; Morono, Yuki; Tavormina, Patricia; Orphan, Victoria J.; Inagaki, Fumio

2017-01-01

High-pressure (HP) environments represent the largest volumetric majority of habitable space for microorganisms on the planet, including the deep-sea and subsurface biosphere. However, the importance of pressure as an environmental variable affecting deep microbial life and their biogeochemical functions in carbon cycling still remains poorly understood. Here, we designed a new high-volume HP-sediment core sampler that is deployable on the payload of a remotely operated vehicle and can maintain in situ HP conditions throughout multi-month enrichment incubations including daily amendments with liquid media and gases and daily effluent sampling for geochemical or microbiological analysis. Using the HP core device, we incubated sediment and overlying water associated with methane hydrate-exposed on the seafloor of the Joetsu Knoll, Japan, at 10 MPa and 4°C for 45 days in the laboratory. Diversity analyses based on 16S rRNA and methane-related functional genes, as well as carbon isotopic analysis of methane and bicarbonate, indicated the stimulation of both aerobic and anaerobic methanotrophy driven by members of the Methylococcales, and ANME, respectively: i.e., aerobic methanotrophy was observed upon addition of oxygen whereas anaerobic processes subsequently occurred after oxygen consumption. These laboratory-measured rates at 10 MPa were generally in agreement with previously reported rates of methane oxidation in other oceanographic locations. PMID:29312247

Fe(III) reduction and U(VI) immobilization by Paenibacillus sp. strain 300A, isolated from Hanford 300A subsurface sediments.

PubMed

Ahmed, Bulbul; Cao, Bin; McLean, Jeffrey S; Ica, Tuba; Dohnalkova, Alice; Istanbullu, Ozlem; Paksoy, Akin; Fredrickson, Jim K; Beyenal, Haluk

2012-11-01

A facultative iron-reducing [Fe(III)-reducing] Paenibacillus sp. strain was isolated from Hanford 300A subsurface sediment biofilms that was capable of reducing soluble Fe(III) complexes [Fe(III)-nitrilotriacetic acid and Fe(III)-citrate] but unable to reduce poorly crystalline ferrihydrite (Fh). However, Paenibacillus sp. 300A was capable of reducing Fh in the presence of low concentrations (2 μM) of either of the electron transfer mediators (ETMs) flavin mononucleotide (FMN) or anthraquinone-2,6-disulfonate (AQDS). Maximum initial Fh reduction rates were observed at catalytic concentrations (<10 μM) of either FMN or AQDS. Higher FMN concentrations inhibited Fh reduction, while increased AQDS concentrations did not. We also found that Paenibacillus sp. 300A could reduce Fh in the presence of natural ETMs from Hanford 300A subsurface sediments. In the absence of ETMs, Paenibacillus sp. 300A was capable of immobilizing U(VI) through both reduction and adsorption. The relative contributions of adsorption and microbial reduction to U(VI) removal from the aqueous phase were ∼7:3 in PIPES [piperazine-N,N'-bis(2-ethanesulfonic acid)] and ∼1:4 in bicarbonate buffer. Our study demonstrated that Paenibacillus sp. 300A catalyzes Fe(III) reduction and U(VI) immobilization and that these reactions benefit from externally added or naturally existing ETMs in 300A subsurface sediments.

Fe(III) Reduction and U(VI) Immobilization by Paenibacillus sp. Strain 300A, Isolated from Hanford 300A Subsurface Sediments

PubMed Central

Ahmed, Bulbul; Cao, Bin; McLean, Jeffrey S.; Ica, Tuba; Dohnalkova, Alice; Istanbullu, Ozlem; Paksoy, Akin; Fredrickson, Jim K.

2012-01-01

A facultative iron-reducing [Fe(III)-reducing] Paenibacillus sp. strain was isolated from Hanford 300A subsurface sediment biofilms that was capable of reducing soluble Fe(III) complexes [Fe(III)-nitrilotriacetic acid and Fe(III)-citrate] but unable to reduce poorly crystalline ferrihydrite (Fh). However, Paenibacillus sp. 300A was capable of reducing Fh in the presence of low concentrations (2 μM) of either of the electron transfer mediators (ETMs) flavin mononucleotide (FMN) or anthraquinone-2,6-disulfonate (AQDS). Maximum initial Fh reduction rates were observed at catalytic concentrations (<10 μM) of either FMN or AQDS. Higher FMN concentrations inhibited Fh reduction, while increased AQDS concentrations did not. We also found that Paenibacillus sp. 300A could reduce Fh in the presence of natural ETMs from Hanford 300A subsurface sediments. In the absence of ETMs, Paenibacillus sp. 300A was capable of immobilizing U(VI) through both reduction and adsorption. The relative contributions of adsorption and microbial reduction to U(VI) removal from the aqueous phase were ∼7:3 in PIPES [piperazine-N,N′-bis(2-ethanesulfonic acid)] and ∼1:4 in bicarbonate buffer. Our study demonstrated that Paenibacillus sp. 300A catalyzes Fe(III) reduction and U(VI) immobilization and that these reactions benefit from externally added or naturally existing ETMs in 300A subsurface sediments. PMID:22961903

Fe(III) Reduction and U(VI) Immobilization by Paenibacillus sp. Strain 300A, Isolated from Hanford 300A Subsurface Sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmed, B.; Cao, B.; McLean, Jeffrey S.

2012-11-07

A facultative iron-reducing (Fe(III)-reducing) Paenibacillus sp. strain was isolated from Hanford 300A subsurface sediment biofilms that was capable of reducing soluble Fe(III) complexes (Fe(III)-NTA and Fe(III)-citrate) but unable to reduce poorly crystalline ferrihydrite (Fh). However, Paenibacillus sp. 300A was capable of reducing Fh in the presence of low concentrations (2 µM) of either of electron transfer mediators (ETMs) flavin mononucleotide (FMN) or anthraquinone-2,6-disulfonate (AQDS). Maximum initial Fh reduction rates were observed at catalytic concentrations (<10 µM) of either FMN or AQDS. Higher FMN concentrations inhibited Fh reduction, while increased AQDS concentrations did not. We found that Paenibacillus sp. 300A alsomore » could reduce Fh in the presence of natural ETMs from Hanford 300A subsurface sediments. In the absence of ETMs, Paenibacillus sp. 300A was capable of immobilizing U(VI) through both reduction and adsorption. The relative contributions of adsorption and microbial reduction to U(VI) removal from the aqueous phase were ~7:3 in PIPES and ~1:4 in bicarbonate buffer. Our study demonstrated that Paenibacillus sp. 300A catalyzes Fe(III) reduction and U(VI) immobilization and that these reactions benefit from externally added or naturally existing ETMs in 300A subsurface sediments.« less

Carbon Burial at the Land Ocean Interface: Climate vs Human Drivers

NASA Astrophysics Data System (ADS)

Bianchi, T. S.; Smeaton, C.; Cui, X.; Howe, J. A.; Austin, W.

2017-12-01

Fjords are connectors between the terrestrial and marine systems and are known as globally significant hotspots for the burial (Smith et al., 2014) and long-term storage (Smeaton et al., 2016) of carbon (C). The glacial geomorphology of fjords and their catchment results in the terrestrial and marine environments being strongly coupled more so than other estuary types. The clearest example of this is the terrestrial C subsidy to these sediment, it is estimated that globally 55-62% of C held in fjord sediments are terrestrially derived (Cui et al., 2016). Yet it is largely unknown how climatic and human forcing drives the transfer of terrestrial C to marine sediments. Here we, examine the role of late Holocene climate and human activity on the transfer of C from the terrestrial to marine environment along the North Atlantic Margin. Loch Sunart a Scottish fjord sits at the land ocean interface of the North Atlantic. The catchment of the fjord has been shown to be sensitive to local and regional climatic change (Gillibrand et al., 2005) and the fjord sediments have been able to record these changes in Climate (Cage and Austin, 2010). Using a long (22 m) sedimentary record we discuss our understanding of mid to late Holocene regional climate and its impact on terrestrial C transfer to the coastal ocean. Alongside this we examine the role of humans on the landscape and their impact on the transfer of terrestrial C on the coastal ocean. The results from this study will further our understanding of the long-term drivers of terrestrial C transfer to the coastal ocean. Potentially this research provides insights on future C transfers under a changing future climate allowing the importance of fjords as a climate regulation service to be reassessed.

In-situ Planetary Subsurface Imaging System

NASA Astrophysics Data System (ADS)

Song, W.; Weber, R. C.; Dimech, J. L.; Kedar, S.; Neal, C. R.; Siegler, M.

2017-12-01

Geophysical and seismic instruments are considered the most effective tools for studying the detailed global structures of planetary interiors. A planet's interior bears the geochemical markers of its evolutionary history, as well as its present state of activity, which has direct implications to habitability. On Earth, subsurface imaging often involves massive data collection from hundreds to thousands of geophysical sensors (seismic, acoustic, etc) followed by transfer by hard links or wirelessly to a central location for post processing and computing, which will not be possible in planetary environments due to imposed mission constraints on mass, power, and bandwidth. Emerging opportunities for geophysical exploration of the solar system from Venus to the icy Ocean Worlds of Jupiter and Saturn dictate that subsurface imaging of the deep interior will require substantial data reduction and processing in-situ. The Real-time In-situ Subsurface Imaging (RISI) technology is a mesh network that senses and processes geophysical signals. Instead of data collection then post processing, the mesh network performs the distributed data processing and computing in-situ, and generates an evolving 3D subsurface image in real-time that can be transmitted under bandwidth and resource constraints. Seismic imaging algorithms (including traveltime tomography, ambient noise imaging, and microseismic imaging) have been successfully developed and validated using both synthetic and real-world terrestrial seismic data sets. The prototype hardware system has been implemented and can be extended as a general field instrumentation platform tailored specifically for a wide variety of planetary uses, including crustal mapping, ice and ocean structure, and geothermal systems. The team is applying the RISI technology to real off-world seismic datasets. For example, the Lunar Seismic Profiling Experiment (LSPE) deployed during the Apollo 17 Moon mission consisted of four geophone instruments spaced up to 100 meters apart, which in essence forms a small aperture seismic network. A pattern recognition technique based on Hidden Markov Models was able to characterize this dataset, and we are exploring how the RISI technology can be adapted for this dataset.

Spectral measurements of Terrestrial Mars Analogues: support for the ExoMars - Ma_Miss instrument

NASA Astrophysics Data System (ADS)

De Angelis, S.; De Sanctis, M. C.; Ammannito, E.; Di Iorio, T.; Carli, C.; Frigeri, A.; Capria, M. T.; Federico, C.; Boccaccini, A.; Capaccioni, F.; Giardino, M.; Cerroni, P.; Palomba, E.; Piccioni, G.

2013-09-01

The Ma_Miss (Mars Multispectral Imager for Subsurface Studies) instrument onboard of ExoMars 2018 mission to Mars will investigate the Martian subsoil down to a depth of 2 meters [1]. Ma_Miss is a miniaturized spectrometer, completely integrated within the drilling system of the ExoMars Pasteur rover; it will acquire spectra in the range 0.4-2.2μm, from the excavated borehole wall. The spectroscopic investigation of the subsurface materials will give us precious information about mineralogical, petrologic and geological processes, and will give insights about materials that have not been modified by surface processes such as erosion, weathering or oxidation. Spectroscopic measurements have been performed on Terrestrial Mars Analogues with the Ma_Miss laboratory model (breadboard). Moreover spectroscopic investigation of different sets of Terrestrial Mars Analogues is being carried on with different laboratory setups, as a support for the ExoMars-Ma_Miss instrument.

Use of sediment source fingerprinting to assess the role of subsurface erosion in the supply of fine sediment in a degraded catchment in the Eastern Cape, South Africa.

PubMed

Manjoro, Munyaradzi; Rowntree, Kate; Kakembo, Vincent; Foster, Ian; Collins, Adrian L

2017-06-01

Sediment source fingerprinting has been successfully deployed to provide information on the surface and subsurface sources of sediment in many catchments around the world. However, there is still scope to re-examine some of the major assumptions of the technique with reference to the number of fingerprint properties used in the model, the number of model iterations and the potential uncertainties of using more than one sediment core collected from the same floodplain sink. We investigated the role of subsurface erosion in the supply of fine sediment to two sediment cores collected from a floodplain in a small degraded catchment in the Eastern Cape, South Africa. The results showed that increasing the number of individual fingerprint properties in the composite signature did not improve the model goodness-of-fit. This is still a much debated issue in sediment source fingerprinting. To test the goodness-of-fit further, the number of model repeat iterations was increased from 5000 to 30,000. However, this did not reduce uncertainty ranges in modelled source proportions nor improve the model goodness-of-fit. The estimated sediment source contributions were not consistent with the available published data on erosion processes in the study catchment. The temporal pattern of sediment source contributions predicted for the two sediment cores was very different despite the cores being collected in close proximity from the same floodplain. This highlights some of the potential limitations associated with using floodplain cores to reconstruct catchment erosion processes and associated sediment source contributions. For the source tracing approach in general, the findings here suggest the need for further investigations into uncertainties related to the number of fingerprint properties included in un-mixing models. The findings support the current widespread use of ≤5000 model repeat iterations for estimating the key sources of sediment samples. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evaluating Impacts of CO2 Gas Intrusion Into a Confined Sandstone aquifer: Experimental Results

DOE PAGES

Qafoku, Nikolla; Lawter, Amanda R.; Shao, Hongbo; ...

2014-12-31

Deep subsurface storage and sequestration of CO2 has been identified as a potential mitigation technique for rising atmospheric CO2 concentrations. Sequestered CO2 represents a potential risk to overlying aquifers if the CO2 leaks from the deep storage reservoir. Experimental and modeling work is required to evaluate potential risks to groundwater quality and develop a systematic understanding of how CO2 leakage may cause important changes in aquifer chemistry and mineralogy by promoting dissolution/precipitation, adsorption/desorption, and redox reactions. Sediments from the High Plains aquifer in Kansas, United States, were used in this investigation, which is part of the National Risk Assessment Partnershipmore » Program sponsored by the US Department of Energy. This aquifer was selected to be representative of consolidated sand and gravel/sandstone aquifers overlying potential CO2 sequestration repositories within the continental US. In this paper, we present results from batch experiments conducted at room temperature and atmospheric pressure with four High Plains aquifer sediments. Batch experiments simulate sudden, fast, and short-lived releases of the CO2 gas as would occur in the case of well failure during injection. Time-dependent release of major, minor, and trace elements were determined by analyzing the contacting solutions. Characterization studies demonstrated that the High Plains aquifer sediments were abundant in quartz and feldspars, and contained about 15 to 20 wt% montmorillonite and up to 5 wt% micas. Some of the High Plains aquifer sediments contained no calcite, while others had up to about 7 wt% calcite. The strong acid extraction tests confirmed that in addition to the usual elements present in most soils, rocks, and sediments, the High Plains aquifer sediments had appreciable amounts of As, Cd, Pb, Cu, and occasionally Zn, which potentially may be mobilized from the solid to the aqueous phase during or after exposure to CO2. However, the results from the batch experiments showed that the High Plains sediments mobilized only low concentrations of trace elements (potential contaminants), which were detected occasionally in the aqueous phase during these experiments. Importantly, these occurrences were more frequent in the calcite-free sediment. Results from these investigations provide useful information to support site selection, risk assessment, and public education efforts associated with geological CO2 storage and sequestration.« less

In situ time-series measurements of subseafloor sediment properties

USGS Publications Warehouse

Wheatcroft, R.A.; Stevens, A.W.; Johnson, R.V.

2007-01-01

The capabilities and diversity of subsurface sediment sensors lags significantly from what is available for the water column, thereby limiting progress in understanding time-dependent seabed exchange and high-frequency acoustics. To help redress this imbalance, a new instrument, the autonomous sediment profiler (ASP), is described herein. ASP consists of a four-electrode, Wenner-type resistivity probe and a thermistor that log data at 0.1-cm vertical intervals over a 58-cm vertical profile. To avoid resampling the same spot on the seafloor, the probes are moved horizontally within a 20 times 100-cm-2 area in one of three preselected patterns. Memory and power capacities permit sampling at hourly intervals for up to 3-mo duration. The system was tested in a laboratory tank and shown to be able to resolve high-frequency sediment consolidation, as well as changes in sediment roughness. In a field test off the southern coast of France, the system collected resistivity and temperature data at hourly intervals for 16 d. Coupled with environmental data collected on waves, currents, and suspended sediment, the ASP is shown to be useful for understanding temporal evolution of subsurface sediment porosity, although no large depositional or erosional events occurred during the deployment. Following a rapid decrease in bottom-water temperature, the evolution of the subsurface temperature field was consistent with the 1-D thermal diffusion equation coupled with advection in the upper 3-4 cm. Collectively, the laboratory and field tests yielded promising results on time-dependent seabed change.

Geometry and significance of stacked gullies on the northern California slope

USGS Publications Warehouse

Field, M.E.; Gardner, J.V.; Prior, D.B.

1999-01-01

Recent geophysical surveys off northern California reveal patterns of gullies on the sea floor and preserved within continental-slope deposits that represent both erosional and aggradational processes. These surveys, conducted as part of the STRATAFORM project, combined multibeam bathymetry and backscatter with high-resolution seismic profiles. These data provide a new basis for evaluating gully morphology, distribution, and their significance to slope sedimentation and evolution. The continental margin off northern California exhibits an upper slope that has undergone both progradation and aggradation. The slope surface, which dips at <2??to 4.0??, contains a set of straight, evenly spaced, and parallel to sub-parallel gullies that begin at the 380-m isobath and extend onto the Eel and Klamath plateaus and into Trinity Canyon. The surface gullies are typically 100-m wide or more and only 1-2 m deep. The gullied slope is underlain by a sedimentary sequence that contains abundant buried gullies to subsurface depths of over 150 m. Although some of the buried gullies are distinctly erosional, most are part of the aggradational pattern responsible for the overall growth of the slope. The latest phase of gully erosion is marked by a gullied surface lying <20 m below the present-day sea floor. These erosional gullies locally truncate individual reflectors, have small depositional levees, and exhibit greater relief than do overlying gullies exposed on the sea floor. The older subsurface gullies document a period of widespread, but minor, erosion and downslope transport, presumably from a large, proximal sediment source. The cycles of downcutting and gully excavation are a minor part of the stratigraphic section, and are likely related to the combined influence of lower sea levels and higher sediment yields. During aggradation of the slope depositional sequences, sediment was draped over the gully features, producing sediment layers that mimic the underlying gully form. Consequently, gully morphology and geometries were preserved and migrated upwards with time. The processes that produce aggraded gully drape also resulted in laterally continuous strata and were most likely related to a period when the sediment source was dispersed from a more distal (10s of km) source, such as during present conditions. The draped sequences also contain a few new gullies, which indicates that gullies can be initiated at all or most stages of slope growth.

Large fluctuations of dissolved oxygen in the Indian and Pacific oceans during Dansgaard-Oeschger oscillations caused by variations of North Atlantic Deep Water subduction

NASA Astrophysics Data System (ADS)

Schmittner, Andreas; Galbraith, Eric D.; Hostetler, Steven W.; Pedersen, Thomas F.; Zhang, Rong

2007-09-01

Paleoclimate records from glacial Indian and Pacific oceans sediments document millennial-scale fluctuations of subsurface dissolved oxygen levels and denitrification coherent with North Atlantic temperature oscillations. Yet the mechanism of this teleconnection between the remote ocean basins remains elusive. Here we present model simulations of the oxygen and nitrogen cycles that explain how changes in deepwater subduction in the North Atlantic can cause large and synchronous variations of oxygen minimum zones throughout the Northern Hemisphere of the Indian and Pacific oceans, consistent with the paleoclimate records. Cold periods in the North Atlantic are associated with reduced nutrient delivery to the upper Indo-Pacific oceans, thereby decreasing productivity. Reduced export production diminishes subsurface respiration of organic matter leading to higher oxygen concentrations and less denitrification. This effect of reduced oxygen consumption dominates at low latitudes. At high latitudes in the Southern Ocean and North Pacific, increased mixed layer depths and steepening of isopycnals improve ocean ventilation and oxygen supply to the subsurface. Atmospheric teleconnections through changes in wind-driven ocean circulation modify this basin-scale pattern regionally. These results suggest that changes in the Atlantic Ocean circulation, similar to those projected by climate models to possibly occur in the centuries to come because of anthropogenic climate warming, can have large effects on marine ecosystems and biogeochemical cycles even in remote areas.

The impact of catchment source group classification on the accuracy of sediment fingerprinting outputs.

PubMed

Pulley, Simon; Foster, Ian; Collins, Adrian L

2017-06-01

The objective classification of sediment source groups is at present an under-investigated aspect of source tracing studies, which has the potential to statistically improve discrimination between sediment sources and reduce uncertainty. This paper investigates this potential using three different source group classification schemes. The first classification scheme was simple surface and subsurface groupings (Scheme 1). The tracer signatures were then used in a two-step cluster analysis to identify the sediment source groupings naturally defined by the tracer signatures (Scheme 2). The cluster source groups were then modified by splitting each one into a surface and subsurface component to suit catchment management goals (Scheme 3). The schemes were tested using artificial mixtures of sediment source samples. Controlled corruptions were made to some of the mixtures to mimic the potential causes of tracer non-conservatism present when using tracers in natural fluvial environments. It was determined how accurately the known proportions of sediment sources in the mixtures were identified after unmixing modelling using the three classification schemes. The cluster analysis derived source groups (2) significantly increased tracer variability ratios (inter-/intra-source group variability) (up to 2122%, median 194%) compared to the surface and subsurface groupings (1). As a result, the composition of the artificial mixtures was identified an average of 9.8% more accurately on the 0-100% contribution scale. It was found that the cluster groups could be reclassified into a surface and subsurface component (3) with no significant increase in composite uncertainty (a 0.1% increase over Scheme 2). The far smaller effects of simulated tracer non-conservatism for the cluster analysis based schemes (2 and 3) was primarily attributed to the increased inter-group variability producing a far larger sediment source signal that the non-conservatism noise (1). Modified cluster analysis based classification methods have the potential to reduce composite uncertainty significantly in future source tracing studies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sediment and Nutrient Sources as well as Interspecific Competition Control Growth of 2 Common Species of Coral Reef Macroalgae

NASA Astrophysics Data System (ADS)

Moore, T.; Fong, P.; Cuker, B.

2016-02-01

Aquatic communities worldwide are increasingly subjected to multiple anthropogenic stressors that often result in shifts in structure and function. On coral reefs, human impacts have been associated with phase-shifts from coral to algal domination. We hypothesized that the proliferation of these algal communities, especially on fringing reefs, may be facilitated by human alterations in nutrient enrichment and input of sediments from developed watersheds, which may also influence competitive outcomes among dominant algal species. To evaluate how changes in these abiotic stressors as well as competition may affect the growth of 2 common species of calcifying coral reef algae, Galaxaura fasciculata and Padina boryana, we conducted 3 separate 2 factor mesocosm experiments modeling fringing reefs in Moorea, French Polynesia. In the first experiment, we varied sediment source (marine vs. terrestrial) and water column nutrients (ambient vs. enriched) for each species separately and measured growth after 7 days. While both algae grew faster in enriched compared to ambient nutrients, P. boryana performed best with marine sediment (+27% change in biomass) and G. fasciculata with terrestrial sediment (+14% change in biomass). Next, we varied sediment source (as above) as well as sediment nutrients (ambient/enriched) for each species. While P. boryana lost 44% biomass in the eutrophic terrestrial sediment treatment, G. fasciculata performed the best and gained 19% biomass. Finally, we varied competition (alone/together) and terrestrial sediment nutrients (ambient/enriched). Over the 7 day period, P. boryana lost 64% biomass when in competition with G. fasciculata in the enriched treatment while G. fasciculata gained 38% biomass when in competition with P. boryana in the ambient treatment. These results indicate that, while growth of both species of macroalgae was regulated by nutrients, sediments, and competition, each responded uniquely to these controlling factors.

Synchronizing early Eocene deep-sea and continental records - cyclostratigraphic age models for the Bighorn Basin Coring Project drill cores

NASA Astrophysics Data System (ADS)

Westerhold, Thomas; Röhl, Ursula; Wilkens, Roy H.; Gingerich, Philip D.; Clyde, William C.; Wing, Scott L.; Bowen, Gabriel J.; Kraus, Mary J.

2018-03-01

A consistent chronostratigraphic framework is required to understand the effect of major paleoclimate perturbations on both marine and terrestrial ecosystems. Transient global warming events in the early Eocene, at 56-54 Ma, show the impact of large-scale carbon input into the ocean-atmosphere system. Here we provide the first timescale synchronization of continental and marine deposits spanning the Paleocene-Eocene Thermal Maximum (PETM) and the interval just prior to the Eocene Thermal Maximum 2 (ETM-2). Cyclic variations in geochemical data come from continental drill cores of the Bighorn Basin Coring Project (BBCP, Wyoming, USA) and from marine deep-sea drilling deposits retrieved by the Ocean Drilling Program (ODP). Both are dominated by eccentricity-modulated precession cycles used to construct a common cyclostratigraphic framework. Integration of age models results in a revised astrochronology for the PETM in deep-sea records that is now generally consistent with independent 3He age models. The duration of the PETM is estimated at ˜ 200 kyr for the carbon isotope excursion and ˜ 120 kyr for the associated pelagic clay layer. A common terrestrial and marine age model shows a concurrent major change in marine and terrestrial biota ˜ 200 kyr before ETM-2. In the Bighorn Basin, the change is referred to as Biohorizon B and represents a period of significant mammalian turnover and immigration, separating the upper Haplomylus-Ectocion Range Zone from the Bunophorus Interval Zone and approximating the Wa-4-Wa-5 land mammal zone boundary. In sediments from ODP Site 1262 (Walvis Ridge), major changes in the biota at this time are documented by the radiation of a second generation of apical spine-bearing sphenolith species (e.g., S. radians and S. editus), the emergence of T. orthostylus, and the marked decline of D. multiradiatus.

Opportunities and challenges in studies of deep life (Invited)

NASA Astrophysics Data System (ADS)

Edwards, K. J.

2010-12-01

Over the past two decades, there has been an increasing awareness within the geological, microbiological, and oceanographic communities of the potentially vast microbial biosphere that is harbored beneath the surface of the Earth. With this awareness has come a mounting effort to study this potential biome - to better quantify biomass abundance, activity, and biogeochemical activity. In the Earth system, the largest deep subsurface biome is also the least accessible - the deep ocean subsurface biosphere. The oceanic deep biosphere also has greatest potential for influencing global scale biogeochemical processes -the carbon and energy cycles for example, and other elemental cycles. To address these topics and mount interdisciplinary efforts to study the deep subsurface marine biosphere, we have recently formed a center in support integrative, collaborative investigations. The national science foundation Center for Dark Biosphere Investigations (C-DEBI), has been initiated for the explicit purpose of resolving the extent, function, dynamics and implications of the subseafloor biosphere. This talk will discuss C-DEBI science, with focus on some of the opportunities and challenges in the study of deep life in the ocean, and the role that C-DEBI will play in meeting them

Late Quaternary environmental changes inferred from n-alkane evidence in coastal area of southern Hainan Island, China

NASA Astrophysics Data System (ADS)

Wang, Mengyuan; Zheng, Zhuo

2016-04-01

The studied core was a coastal core in Hainan Island, China. It is in length of 49.01m and divided into four Units (MIS 1~MIS 6) according to lithology description. The Optically Stimulated Luminescence (OSL) attributes the sediments from Unit 3 to the Oxygen Isotope Stage of MIS 5e (Unit 3b and 3c) and 5d (Unit 3a). To interpret the origination of organic carbons and to reconstruct paleovegetation changes, n-alkane, δ13C and TOC have been used in the present research. The result of n-alkanes distribution indicates a series of changes of sedimentary environment and terrestrial input. The shallow water facies at Unit 2, 3a and 4 is mainly characterized by short carbon chain n-alkanes and relatively low concentration. Contrasting with that of deep-water marine facies of MIS 5e (Unit 3b), the n-alkane pattern is typical bimodal and the main peaks are both in short and long carbon chains. During Unit 3b-1 (MIS 5e), more terrestrial original n-alkanes contribute to the concentration of TOC than oceanic. Organic matter source is mainly terrestrial origination. Total organic matter input mechanism of TLG-01 correlates with sediment grain size (average grain size). Total organic carbon input is enhanced with the increasing of fine grain size component. The variation of CPI (25-33) value in this study correlates with hydrological energy. The highest CPI (25-33) value is shown in the high sea level period of MIS 5e, comparing with that in MIS 5d and MIS 1. High CPI value corresponds to high TOC and average grain size (Φ) value. In the weak hydrological energy sedimentary environment, more terrestrial organic matter, together with TOC, deposit in the study area. ACL (25-33) index display higher values in the interglacial period (MIS 5 and MIS 1) than MIS 3 (sediments weathered during MIS 2) and MIS 6. Paq proxy, together with δ13C, estimates the mangrove growing depth in MIS 5e. The correlation between δ13C and each carbon chain alkane state stabilize and turbulence of sedimentary environment in MIS 5e. Sediments deposit in stable weak hydrological energy environment show order and grouped alkanes distribution (Unit 3b-2). High and positive correlation coefficients of δ13C and each carbon chain alkane show the dominant alkanes contributed to organic carbon (δ13C).

Adaptation of benthic invertebrates to food sources along marine-terrestrial boundaries as indicated by carbon and nitrogen stable isotopes

NASA Astrophysics Data System (ADS)

Lange, G.; Haynert, K.; Dinter, T.; Scheu, S.; Kröncke, I.

2018-01-01

Frequent environmental changes and abiotic gradients of the Wadden Sea require appropriate adaptations of the local organisms and make it suitable for investigations on functional structure of macrozoobenthic communities from marine to terrestrial boundaries. To investigate community patterns and food use of the macrozoobenthos, a transect of 11 stations was sampled for species number, abundance and stable isotope values (δ13C and δ15N) of macrozoobenthos and for stable isotope values of potential food resources. The transect was located in the back-barrier system of the island of Spiekeroog (southern North Sea, Germany). Our results show that surface and subsurface deposit feeders, such as Peringia ulvae and different oligochaete species, dominated the community, which was poor in species, while species present at the transect stations reached high abundance. The only exception was the upper salt marsh with low abundances but higher species richness because of the presence of specialized semi-terrestrial and terrestrial taxa. The macrozoobenthos relied predominantly on marine resources irrespective of the locality in the intertidal zone, although δ13C values of the consumers decreased from - 14.1 ± 1.6‰ (tidal flats) to - 21.5 ± 2.4‰ (salt marsh). However, the ubiquitous polychaete Hediste diversicolor showed a δ15N enrichment of 2.8‰ (an increase of about one trophic level) from bare sediments to the first vegetated transect station, presumably due to switching from suspension or deposit feeding to predation on smaller invertebrates. Hence, we conclude that changes in feeding mode represent an important mechanism of adaptation to different Wadden Sea habitats.

Aligning MIS5 proxy records from Lake Ohrid (FYROM) with independently dated Mediterranean archives: implications for core chronology

NASA Astrophysics Data System (ADS)

Zanchetta, G.; Regattieri, E.; Giaccio, B.; Wagner, B.; Sulpizio, R.; Francke, A.; Vogel, L. H.; Sadori, L.; Masi, A.; Sinopoli, G.; Lacey, J. H.; Leng, M. L.; Leicher, N.

2015-10-01

The DEEP site sediment sequence obtained during the ICDP SCOPSCO project at Lake Ohrid was dated using tephrostratigraphic information, cyclostratigraphy, and orbital tuning through marine isotope record. Although this approach is suitable for the generation of a general chronological framework of the long succession, it is insufficient to resolve more detailed paleoclimatological questions, such as leads and lags of climate events between marine and terrestrial records or between different regions. In this paper, we demonstrate how the use of different tie points can affect cyclostratigraphy and orbital tuning for the period between ca. 140 and 70 ka and how the results can be correlated with directly/indirectly radiometrically-dated Mediterranean marine and continental proxy records. The alternative age model obtained shows consistent differences with that proposed by Francke et al. (2015) for the same interval, in particular at the level of the MIS6-5e transition. According to this age model, different proxies from the DEEP site sediment record support an increase of temperatures between glacial to interglacial conditions, which is almost synchronous with a rapid increase in sea surface temperature observed in the western Mediterranean. The results show how important a detailed study of independent chronological tie points is for synchronizing different records and to highlight asynchronisms of climate events.

Relative Abundance and Diversity of Bacterial Methanotrophs at the Oxic–Anoxic Interface of the Congo Deep-Sea Fan

PubMed Central

Bessette, Sandrine; Moalic, Yann; Gautey, Sébastien; Lesongeur, Françoise; Godfroy, Anne; Toffin, Laurent

2017-01-01

Sitting at ∼5,000 m water depth on the Congo-Angola margin and ∼760 km offshore of the West African coast, the recent lobe complex of the Congo deep-sea fan receives large amounts of fluvial sediments (3–5% organic carbon). This organic-rich sedimentation area harbors habitats with chemosynthetic communities similar to those of cold seeps. In this study, we investigated relative abundance, diversity and distribution of aerobic methane-oxidizing bacteria (MOB) communities at the oxic–anoxic interface of sedimentary habitats by using fluorescence in situ hybridization and comparative sequence analysis of particulate mono-oxygenase (pmoA) genes. Our findings revealed that sedimentary habitats of the recent lobe complex hosted type I and type II MOB cells and comparisons of pmoA community compositions showed variations among the different organic-rich habitats. Furthermore, the pmoA lineages were taxonomically more diverse compared to methane seep environments and were related to those found at cold seeps. Surprisingly, MOB phylogenetic lineages typical of terrestrial environments were observed at such water depth. In contrast, MOB cells or pmoA sequences were not detected at the previous lobe complex that is disconnected from the Congo River inputs. PMID:28487684

Large-scale deformational systems in the South Polar Layered Deposits (Promethei Lingula, Mars): "Soft-sediment" and Deep-Seated Gravitational Slope Deformations Mechanisms

NASA Astrophysics Data System (ADS)

Guallini, Luca; Brozzetti, Francesco; Marinangeli, Lucia

2012-08-01

The present study is the first attempt at a detailed structural and kinematic analysis of large-scale deformational systems observed in the South Polar Layered Deposits (SPLDs) in the Promethei Lingula (PL) margins (Mars). By systematically collecting attitude data referable to previously unknown deformational structures and defining the cross-cut relationships of the structures, we reconstructed a deformational history consisting of two superimposed, well-defined stages. The first stage is dominated by large-scale strike-slip and transtensional faults arranged into conjugate systems and delimiting shear zones that show a wide range of subsidiary structures, including normal and reverse faults, drag folds, boudins, S-C tectonites and sub-horizontal interstratal shear planes marked by sygmoidal boudins. Other typical structures referable to this event are ductile folds (locally true convolute folds) and lobes (ball-and-pillow structures) affecting certain marker beds of the succession. We suggest that the structural assemblage might be the expression of a shallow soft-sediment tectonics that possibly occurred during warm periods of the South Pole climate. The second stage seems to affect the weaker and in certain cases pre-deformed stratigraphic levels of the SPLD succession. This stage is mainly characterized by extensional deformations caused by gravity. The consequence of the deformations is the nucleation of Deep-Seated Gravitational Slope Deformations (DSGSDs) marked by typical morphostructures, such as scarps, trenches and bulging basal contractant zones. These phenomena were never observed within an ice cap. According to terrestrial modeling, these slow collapses were caused by (1) the presence of detachment levels (i.e., subhorizontal bedding planes) along which the ice-sheet margins can slide and (2) the development of listric faults within the glacial mass, which merge with sub-horizontal shear planes in the subsurface. The presence of complex deformational systems in the SPLD necessarily implies that a large-scale dynamics of the ice-sheet occurred in the past. The relatively fast internal creep and basal/internal sliding, inferable from the structure assemblage, can be due to partial melting of the ice possibly caused by climatic changes in the Promethei Lingula region. In this manner, we believe that climate heating (which, according to the literature, is likely caused by orbital variations) softened some of the SPLD layers, triggering or accelerating the ice sheet's outward movement. The evidence of a marked disharmonic deformational style through the SPLD succession suggests the possibility of local periodic compositional variations in the sequence.

Dehalogenation activities and distribution of reductive dehalogenase homologous genes in marine subsurface sediments.

PubMed

Futagami, Taiki; Morono, Yuki; Terada, Takeshi; Kaksonen, Anna H; Inagaki, Fumio

2009-11-01

Halogenated organic compounds serve as terminal electron acceptors for anaerobic respiration in a diverse range of microorganisms. Here, we report on the widespread distribution and diversity of reductive dehalogenase homologous (rdhA) genes in marine subsurface sediments. A total of 32 putative rdhA phylotypes were detected in sediments from the southeast Pacific off Peru, the eastern equatorial Pacific, the Juan de Fuca Ridge flank off Oregon, and the northwest Pacific off Japan, collected at a maximum depth of 358 m below the seafloor. In addition, significant dehalogenation activity involving 2,4,6-tribromophenol and trichloroethene was observed in sediment slurry from the Nankai Trough Forearc Basin. These results suggest that dehalorespiration is an important energy-yielding pathway in the subseafloor microbial ecosystem.

Observational and modeling constraints on global anthropogenic enrichment of mercury.

PubMed

Amos, Helen M; Sonke, Jeroen E; Obrist, Daniel; Robins, Nicholas; Hagan, Nicole; Horowitz, Hannah M; Mason, Robert P; Witt, Melanie; Hedgecock, Ian M; Corbitt, Elizabeth S; Sunderland, Elsie M

2015-04-07

Centuries of anthropogenic releases have resulted in a global legacy of mercury (Hg) contamination. Here we use a global model to quantify the impact of uncertainty in Hg atmospheric emissions and cycling on anthropogenic enrichment and discuss implications for future Hg levels. The plausibility of sensitivity simulations is evaluated against multiple independent lines of observation, including natural archives and direct measurements of present-day environmental Hg concentrations. It has been previously reported that pre-industrial enrichment recorded in sediment and peat disagree by more than a factor of 10. We find this difference is largely erroneous and caused by comparing peat and sediment against different reference time periods. After correcting this inconsistency, median enrichment in Hg accumulation since pre-industrial 1760 to 1880 is a factor of 4.3 for peat and 3.0 for sediment. Pre-industrial accumulation in peat and sediment is a factor of ∼ 5 greater than the precolonial era (3000 BC to 1550 AD). Model scenarios that omit atmospheric emissions of Hg from early mining are inconsistent with observational constraints on the present-day atmospheric, oceanic, and soil Hg reservoirs, as well as the magnitude of enrichment in archives. Future reductions in anthropogenic emissions will initiate a decline in atmospheric concentrations within 1 year, but stabilization of subsurface and deep ocean Hg levels requires aggressive controls. These findings are robust to the ranges of uncertainty in past emissions and Hg cycling.

Coupled Geochemical Impacts of Leaking CO2 and Contaminants from Subsurface Storage Reservoirs on Groundwater Quality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao, Hongbo; Qafoku, Nikolla; Lawter, Amanda R.

2015-07-07

The leakage of CO2 and the concomitant saline solutions from deep storage reservoirs to overlying groundwater aquifers is considered one of the major potential risks associated with geologic CO2 sequestration (GCS). Batch and column experiments were conducted to determine the fate of trace metals in groundwater in the scenarios of CO2 and metal contaminated brine leakage. The sediments used in this work were collected from an unconsolidated sand and gravel aquifer in Kansas, and contained 0-4 wt% carbonates. Cd and As were spiked into the reaction system to represent potential contaminants from the reservoir brine that could intrude into groundwatermore » aquifers with leaking CO2 at initial concentrations of 114 and 40 ppb, respectively. Through this research we demonstrated that Cd and As were adsorbed on the sediments, in spite of the lowered pH due to CO2 dissolution in the groundwater. Cd concentrations were well below its MCL in both batch and column studies, even for sediment samples without detectable carbonate to buffer the pH. Arsenic concentrations in the effluent were also significantly lower than influent concentration, suggesting that the sediments tested have the capacity to mitigate the coupled adverse effects of CO2 leakage and brine intrusion. However, the mitigation capacity of sediment is a function of its geochemical properties [e.g., the calcite content; the presence of adsorbed As(III); and the presence of P in the natural sediment]. The competitive adsorption between phosphate and arsenate may result in higher concentrations of As in the aqueous phase.« less

North Pond: a natural observatory for sub-seafloor oxidant supply and metabolic reactions

NASA Astrophysics Data System (ADS)

Ziebis, Wiebke; Ferdelman, Timothy; McManus, James; Muratli, Jesse; Picard, Aude; Schmidt-Schierhorn, Friederike; Stephan, Sebastian; Villinger, Heinrich; Edwards, Katrina J.

2010-05-01

Evidence of upward transport of oxidants from basaltic aquifers to deeply buried sediments has raised questions on microbial respiration and energy cycling within the deep biosphere. Sediment ponds that occur over a vast area of sea floor on the flank of the Mid-Atlantic Ridge maybe ideal observatories to study the role of unsuspected sources of oxidants for sub-seafloor microbial life. The western flank of the Mid-Atlantic Ridge, at 22°45'N is characterized by depressions filled with sediment and surrounded by high relief topography of 7 Ma old basement. The largest depressions are 5 km to 20 km wide and sediment thickness varies but can reach 400 m (Langseth et al. 1992). They are believed to overly recharge zones for the venting of fluids that takes place locally through unsedimented young ocean crust. If we consider the sediments as boundaries overlying the hydrologically active crustal environment, then using profiles of bioactive compounds measured through the sediment layer with the goal to extract information on transport and reactions is an obvious approach to understanding the implications of subsurface transport of oxidants on metabolic activity. Recently obtained deep oxygen profiles obtained during a site survey expedition in February/March of 2009 onboard RV Maria S. Merian to North Pond, one of the larger (70 square km) and best studied sediment ponds, provided proof of this principal. North Pond is the site of the proposed IODP Expedition "677 Mid-Atlantic Microbiology". Investigations included heat-flow, single-channel seismic and bathymetry surveys, as well as gravity coring. Oxygen measurements and pore water sampling (25 cm depth intervals) were performed directly on intact sediment cores, which were subsequently sampled for microbiological analyses, as well as for incubation experiments to test for autotrophic and heterotrophic microbial activity. The entire sediment column down to > 8 m sediment depth contained oxygen. In the central part of the sediment pond oxygen decreased continuously with depth, indicating an active aerobic microbial community, while nitrate concentrations increased. In contrast, along the northern and western rims of North Pond, oxygen concentrations remained surprisingly constant with depth at values around 170 µM. In addition, at 3 locations along the north shore oxygen profiles indicated an upward supply of oxygen from the underlying basaltic basement. Pore water nutrient profiles and incubation experiments confirmed active microbial communities throughout the sediment layer, as well as the influence of upward transport of oxidants on microbial processes in deeply buried sediments. Langseth, M.G., K. Becker, R.P. Von Herzen, and P. Schultheiss. 1992. Heat and fluid flow through sediments on the western flank of the Mid-Atlantic Ridge: A hydrogeological study of North Pond. Geophys. Res. Lett. 19: 517-520.

Mn-Oxide Minerals from a Terrestrial Cave Environment: Biomarkers for the Search for Life on Mars?

NASA Technical Reports Server (NTRS)

Spilde, M. N.; Brearley, A. J.; Papike, J. J.

2001-01-01

Mn-oxides are promising biomarkers because microbes greatly accelerate Mn-oxide formation rates and produce distinctive oxidation states. Mn minerals in terrestrial caves form subaerially and could conceivably be present in the subsurface of Mars. Additional information is contained in the original extended abstract.

Photochemical dissolution of organic matter from resuspended sediments: Impact of source and diagenetic state on photorelease

NASA Astrophysics Data System (ADS)

Helms, J. R.; Glinski, D. A.; Mead, R. N.; Southwell, M.; Avery, G. B., Jr.; Kieber, R. J.; Skrabal, S. A.

2015-12-01

Resuspended sediments exposed to simulated solar radiation release dissolved organic carbon (DOC). However, it is unclear how the provenance of sedimentary organic matter (OM) impacts this photorelease. In the first geographically extensive study of this phenomenon, twenty three size fractionated, fine grained sediments (< ca. 10-20 μm) from a variety of drainage basins were resuspended (at suspended solid loading of 29- 255 mg/l) and exhibited a net photochemical DOC release ranging from 2 to 178 μmol/g/h. There was a logarithmic increase in photoreleased DOC vs. the proportion of sedimentary OC (%), most likely due to photon limitation at high sedimentary OC loading (i.e. high mass-specific absorption limiting light penetration). Sediment source and quality - determined using lipid biomarkers - had a significant effect on DOC photorelease. The fatty acid terrestrial aquatic ratio (TARFA) indicated that terrestrially derived sediments exhibited relatively greater DOC photorelease. The long chain carbon preference index (CPI24-34) indicated that diagenetically unaltered terrestrial OM photoreleased more DOC than diagenetically altered terrestrial OM. The short chain carbon preference index (CPI14-22) demonstrated that sediments containing diagenetically altered planktonic or algal derived OM had a greater photorelease rate of DOC than fresh algal OM. This suggests that humic substances (humus and/or adsorbed humic and fulvic acids) play an important role in the photochemical dissolution of OC regardless of whether or not they are imported from upstream (i.e. terrestrial humics) or generated within the depositional or sedimentary environment (i.e. humification of algal dissolved OM).

Occurrence and possible sources of arsenic in seafloor sediments surrounding sea-disposed munitions and chemical agents near O´ahu, Hawai´i

NASA Astrophysics Data System (ADS)

Tomlinson, Michael S.; De Carlo, Eric Heinen

2016-06-01

The Department of Defense disposed of conventional and chemical munitions as well as bulk containers of chemical agents in US coastal waters including those surrounding the State of Hawai´i. The Hawai´i Undersea Military Munitions Assessment has been collecting biota, water, and sediment samples from two disposal areas south of the island of O´ahu in waters 500 to 600 m deep known to have received both conventional munitions and chemical agents (specifically sulfur mustard). Unlike a number of other sea-disposed munitions investigations which used grabs or corers lowered from surface vessels, we used manned submersibles to collect the samples. Using this approach, we were able to visually identify the munitions and precisely locate our samples in relation to the munitions on the seafloor. This paper focuses on the occurrence and possible sources of arsenic found in the sediments surrounding the disposed military munitions and chemical agents. Using nonparametric multivariate statistical techniques, we looked for patterns in the chemical data obtained from these sediment samples in order to determine the possible sources of the arsenic found in these sediments. The results of the ordination technique nonmetric multidimensional scaling indicate that the arsenic is associated with terrestrial sources and not munitions. This was not altogether surprising given that: (1) the chemical agents disposed of in this area supposedly did not contain arsenic, and (2) the disposal areas studied were under terrestrial influence or served as dredge spoil disposal sites. The sediment arsenic concentrations during this investigation ranged from <1.3 to 40 mg/kg-dry weight with the lower concentrations typically found around control sites and munitions (not located in dredge disposal areas) and the higher values found at dredge disposal sites (with or without munitions). During the course of our investigation we did, however, discover that mercury appears to be loosely associated with munitions. Given that mercury contamination has been seen in about 20% of the munitions and ton containers of sulfur mustard, the association of mercury with chemical agents is not totally unexpected.

Methane Emission in a Specific Riparian-Zone Sediment Decreased with Bioelectrochemical Manipulation and Corresponded to the Microbial Community Dynamics

PubMed Central

Friedman, Elliot S.; McPhillips, Lauren E.; Werner, Jeffrey J.; Poole, Angela C.; Ley, Ruth E.; Walter, M. Todd; Angenent, Largus T.

2016-01-01

Dissimilatory metal-reducing bacteria are widespread in terrestrial ecosystems, especially in anaerobic soils and sediments. Thermodynamically, dissimilatory metal reduction is more favorable than sulfate reduction and methanogenesis but less favorable than denitrification and aerobic respiration. It is critical to understand the complex relationships, including the absence or presence of terminal electron acceptors, that govern microbial competition and coexistence in anaerobic soils and sediments, because subsurface microbial processes can effect greenhouse gas emissions from soils, possibly resulting in impacts at the global scale. Here, we elucidated the effect of an inexhaustible, ferrous-iron and humic-substance mimicking terminal electron acceptor by deploying potentiostatically poised electrodes in the sediment of a very specific stream riparian zone in Upstate New York state. At two sites within the same stream riparian zone during the course of 6 weeks in the spring of 2013, we measured CH4 and N2/N2O emissions from soil chambers containing either poised or unpoised electrodes, and we harvested biofilms from the electrodes to quantify microbial community dynamics. At the upstream site, which had a lower vegetation cover and highest soil temperatures, the poised electrodes inhibited CH4 emissions by ∼45% (when normalized to remove temporal effects). CH4 emissions were not significantly impacted at the downstream site. N2/N2O emissions were generally low at both sites and were not impacted by poised electrodes. We did not find a direct link between bioelectrochemical treatment and microbial community membership; however, we did find a correspondence between environment/function and microbial community dynamics. PMID:26793170

Benthic Foraminifers identify the source of displaced sediment from a sediment density flow at 1840 m near the Seafloor Instrument Node of the Monterey Coordinated Canyon Experiment

NASA Astrophysics Data System (ADS)

McGann, M.; Maier, K. L.; Gales, J. A.; Paull, C. K.; Gwiazda, R.; Barry, J.; Carvajal, C.; Clare, M. A.; Cartigny, M.; Chaffey, M. R.; Parsons, D. R.; O'Reilly, T. C.; Rosenberger, K. J.; Wolfson-Schwehr, M.; Simmons, S.; Sumner, E.; Talling, P.; Xu, J.

2017-12-01

Submarine canyons are found along the slopes of most continental margins and turbidity currents are thought to be the primary mechanism responsible for transporting sediment through them to deep-sea fans. The initiation sites of these flows are difficult to locate with any degree of precision from lithology alone. Fortunately, the presence of allochthonous microscopic remains, such as benthic foraminifers, can aid in the identification of the source of the displaced sediments. In Monterey Canyon, offshore California, a Seafloor Instrument Node (SIN) and adjacent mooring in the Coordinated Canyon Experiment indicate that a February 2017 turbidity current reached 1840 m water depth. In April 2017, one push core was obtained on each of four sides of the SIN just outside its frame and six others from 30-100 m away. Each was cut into 1 cm slices, stained with rose Bengal, washed, and analyzed for their microscopic constituents. Material recovered included terrestrial debris (wood, leaves, seeds, highway safety spheres, and volcanic glass) as well as foraminiferal tests. Dead benthic foraminifers from the estuarine (0-10 m), inner shelf (0-50 m), outer shelf (50-150 m), slope break (150 m), upper bathyal (150-500 m), and middle bathyal (500-2000 m) biofacies were present, suggesting a staged progression of sediment downslope from the continental shelf and slope. Living (rose Bengal stained) foraminifers recovered represent estuarine (Ammonia tepida, Elphidium excavatum), inner shelf (Buccella frigida, B. tenerrima, Buliminella elegantissima, Cibicides fletcheri, Nonionella spp., Rotorbinella turbinata), and upper bathyal (Bolivina pacifica, B. spissa, Epistominella exigua, Uvigerina peregrina) species as well as an in-situ middle bathyal biofacies (Bolivina argentea, B. spissa, Buliminella tenuata, Epistominella pacifica, Globobulimina spp., Uvigerina peregrina, U. hispida). The presence of living allochthonous benthic foraminifers from these shallower biofacies suggests the flow that covered portions of the SIN frame and the surrounding area originated in the estuarine to shallow shelf environment. Because the shallow water species were still alive when deposited at 1840 m water depth, the sediment gravity flow was a rapid event that transported sediment down canyon to this deep-marine site.

Macrostrat and GeoDeepDive: A Platform for Geological Data Integration and Deep-Time Research

NASA Astrophysics Data System (ADS)

Husson, J. M.; Peters, S. E.; Ross, I.; Czaplewski, J. J.

2016-12-01

Characterizing the quantity, lithology, age, and properties of rocks and sediments in the upper crust is central to many questions in Earth science. Although a large number of geological maps, regional syntheses, and sample-based measurements have been published in a variety of formats, there is no system for integrating and accessing rock record-derived data or for facilitating the large-scale quantitative interrogation of the physical, chemical, and biological properties of Earth's crust. Here we describe two data resources that aim to overcome some of these limitations: 1) Macrostrat, a geospatial database and supporting cyberinfrastructure that is designed to enable quantitative analyses of the entire assemblage of surface and subsurface sedimentary, igneous and metamorphic rocks, and 2) GeoDeepDive, a digital library and high throughput computing system designed to facilitate the location and extraction of information and data from the published literature. Macrostrat currently contains general summaries of the age and lithology of rocks and sediments in the upper crust at 1,474 regions in North and Central America, the Caribbean, New Zealand, and the deep sea. Distributed among these geographic regions are nearly 34,000 lithologically and chronologically-defined geological units, many of which are linked to a bedrock geologic map database with more than 1.7 million globally distributed units. Sample-derived data, including fossil occurrences in the Paleobiology Database and more than 180,000 geochemical and outcrop-derived measurements are linked to Macrostrat units and/or lithologies within those units. The rock names, lithological terms, and geological time intervals that are applied to Macrostrat units define a hierarchical, spatially and temporally indexed vocabulary that is leveraged by GeoDeepDive in order to provide researchers access to data within the scientific literature as it is published and ingested into the infrastructure. All data in Macrostrat are accessible via an Application Programming Interface, which enables the development of mobile and analytical applications. The GeoDeepDive infrastructure also supports the development and execution of applications that are tailored to the specific, literature-based data location and extraction needs of geoscientists.

The Limits of Life in the Deep Subsurface - Implications for the Origin of Life

NASA Astrophysics Data System (ADS)

Baross, John

2013-06-01

There are very few environments on Earth where life is absent. Microbial life has proliferated into habitats that span nearly every imaginable physico-chemical variable. Only the availability of liquid water and temperature are known to prevent the growth of organisms. The other extreme physical and chemical variables, such as pH, pressure, high concentrations of solutes, damaging radiation, and toxic metals, are life-prohibiting factors for most organisms but not for all. The deep subsurface environments span all of the extreme conditions encountered by life including habitat conditions not yet explored, such as those that combine high temperature, high and low pH and extreme pressures. Some of the ``extremophile'' microorganisms inhabiting the deep subsurface environments have been shown to be among the most ``ancient'' of extant life. Their genomes and physiologies have led to a broader understanding of the geological settings of early life, the most ancient energy pathways, and the importance of water/rock interactions and tectonics in the origin and early evolution of life. The case can now be made that deep subsurface environments contributed to life's origin and provided the habitat(s) for the earliest microbial communities. However, there is much more to be done to further our understanding on the role of moderate to high pressures and temperatures on the chemical and biochemical ``steps'' leading to life, and on the evolution and physiology of both ancient and present-day subsurface microbial communities.

Selective phylogenetic analysis targeting 16S rRNA genes of hyperthermophilic archaea in the deep-subsurface hot biosphere.

PubMed

Kimura, Hiroyuki; Ishibashi, Jun-Ichiro; Masuda, Harue; Kato, Kenji; Hanada, Satoshi

2007-04-01

International drilling projects for the study of microbial communities in the deep-subsurface hot biosphere have been expanded. Core samples obtained by deep drilling are commonly contaminated with mesophilic microorganisms in the drilling fluid, making it difficult to examine the microbial community by 16S rRNA gene clone library analysis. To eliminate mesophilic organism contamination, we previously developed a new method (selective phylogenetic analysis [SePA]) based on the strong correlation between the guanine-plus-cytosine (G+C) contents of the 16S rRNA genes and the optimal growth temperatures of prokaryotes, and we verified the method's effectiveness (H. Kimura, M. Sugihara, K. Kato, and S. Hanada, Appl. Environ. Microbiol. 72:21-27, 2006). In the present study we ascertained SePA's ability to eliminate contamination by archaeal rRNA genes, using deep-sea hydrothermal fluid (117 degrees C) and surface seawater (29.9 degrees C) as substitutes for deep-subsurface geothermal samples and drilling fluid, respectively. Archaeal 16S rRNA gene fragments, PCR amplified from the surface seawater, were denatured at 82 degrees C and completely digested with exonuclease I (Exo I), while gene fragments from the deep-sea hydrothermal fluid remained intact after denaturation at 84 degrees C because of their high G+C contents. An examination using mixtures of DNAs from the two environmental samples showed that denaturation at 84 degrees C and digestion with Exo I completely eliminated archaeal 16S rRNA genes from the surface seawater. Our method was quite useful for culture-independent community analysis of hyperthermophilic archaea in core samples recovered from deep-subsurface geothermal environments.

Effects of Protection and Sediment Stress on Coral Reefs in Saint Lucia

PubMed Central

Bégin, Chantale; Schelten, Christiane K.; Nugues, Maggy M.; Hawkins, Julie; Roberts, Callum; Côté, Isabelle M.

2016-01-01

The extent to which Marine Protected Areas (MPAs) benefit corals is contentious. On one hand, MPAs could enhance coral growth and survival through increases in herbivory within their borders; on the other, they are unlikely to prevent disturbances, such as terrestrial runoff, that originate outside their boundaries. We examined the effect of spatial protection and terrestrial sediment on the benthic composition of coral reefs in Saint Lucia. In 2011 (10 to 16 years after MPAs were created), we resurveyed 21 reefs that had been surveyed in 2001 and analyzed current benthic assemblages as well as changes in benthic cover over that decade in relation to protection status, terrestrial sediment influence (measured as the proportion of terrigenous material in reef-associated sediment) and depth. The cover of all benthic biotic components has changed significantly over the decade, including a decline in coral and increase in macroalgae. Protection status was not a significant predictor of either current benthic composition or changes in composition, but current cover and change in cover of several components were related to terrigenous content of sediment deposited recently. Sites with a higher proportion of terrigenous sediment had lower current coral cover, higher macroalgal cover and greater coral declines. Our results suggest that terrestrial sediment is an important factor in the recent degradation of coral reefs in Saint Lucia and that the current MPA network should be complemented by measures to reduce runoff from land. PMID:26845451

Effects of Protection and Sediment Stress on Coral Reefs in Saint Lucia.

PubMed

Bégin, Chantale; Schelten, Christiane K; Nugues, Maggy M; Hawkins, Julie; Roberts, Callum; Côté, Isabelle M

2016-01-01

The extent to which Marine Protected Areas (MPAs) benefit corals is contentious. On one hand, MPAs could enhance coral growth and survival through increases in herbivory within their borders; on the other, they are unlikely to prevent disturbances, such as terrestrial runoff, that originate outside their boundaries. We examined the effect of spatial protection and terrestrial sediment on the benthic composition of coral reefs in Saint Lucia. In 2011 (10 to 16 years after MPAs were created), we resurveyed 21 reefs that had been surveyed in 2001 and analyzed current benthic assemblages as well as changes in benthic cover over that decade in relation to protection status, terrestrial sediment influence (measured as the proportion of terrigenous material in reef-associated sediment) and depth. The cover of all benthic biotic components has changed significantly over the decade, including a decline in coral and increase in macroalgae. Protection status was not a significant predictor of either current benthic composition or changes in composition, but current cover and change in cover of several components were related to terrigenous content of sediment deposited recently. Sites with a higher proportion of terrigenous sediment had lower current coral cover, higher macroalgal cover and greater coral declines. Our results suggest that terrestrial sediment is an important factor in the recent degradation of coral reefs in Saint Lucia and that the current MPA network should be complemented by measures to reduce runoff from land.

Clustered streamlined forms in Athabasca Valles, Mars: Evidence for sediment deposition during floodwater ponding

USGS Publications Warehouse

Burr, D.

2005-01-01

A unique clustering of layered streamlined forms in Athabasca Valles is hypothesized to reflect a significant hydraulic event. The forms, interpreted as sedimentary, are attributed to extensive sediment deposition during ponding and then streamlining of this sediment behind flow obstacles during ponded water outflow. These streamlined forms are analogous to those found in depositional basins and other loci of ponding in terrestrial catastrophic flood landscapes. These terrestrial streamlined forms can provide the best opportunity for reconstructing the history of the terrestrial flooding. Likewise, the streamlined forms in Athabasca Valles may provide the best opportunity to reconstruct the recent geologic history of this young Martian outflow channel. ?? 2005 Elsevier B.V. All rights reserved.

Sorption and speciation of iodine in groundwater system: The roles of organic matter and organic-mineral complexes.

PubMed

Li, Junxia; Zhou, Hailing; Wang, Yanxin; Xie, Xianjun; Qian, Kun

2017-06-01

Characterizing the properties of main host of iodine in soil/sediment and the geochemical behaviors of iodine species are critical to understand the mechanisms of iodine mobilization in groundwater systems. Four surface soil and six subsurface sediment samples were collected from the iodine-affected area of Datong basin in northern China to conduct batch experiments and to evaluate the effects of NOM and/or organic-mineral complexes on iodide/iodate geochemical behaviors. The results showed that both iodine contents and k f -iodate values had positive correlations with solid TOC contents, implying the potential host of NOM for iodine in soil/sediment samples. The results of chemical removal of easily extracted NOM indicated that the NOM of surface soils is mainly composed of surface embedded organic matter, while sediment NOM mainly occurs in the form of organic-mineral complexes. After the removal of surface sorbed NOM, the decrease in k f -iodate value of treated surface soils indicates that surface sorbed NOM enhances iodate adsorption onto surface soil. By contrast, k f -iodate value increases in several H 2 O 2 -treated sediment samples, which was considered to result from exposed rod-like minerals rich in Fe/Al oxyhydroxide/oxides. After chemical removal of organic-mineral complexes, the lowest k f -iodate value for both treated surface soils and sediments suggests the dominant role of organic-mineral complexes on controlling the iodate geochemical behavior. In comparison with iodate, iodide exhibited lower affinities on all (un)treated soil/sediment samples. The understanding of different geochemical behaviors of iodine species helps to explain the occurrence of high iodine groundwater with iodate and iodide as the main species in shallow (oxidizing conditions) and deep (reducing conditions) groundwater. Copyright © 2017 Elsevier B.V. All rights reserved.

Microbial community stratification controlled by the subseafloor fluid flow and geothermal gradient at the Iheya North hydrothermal field in the Mid-Okinawa Trough (Integrated Ocean Drilling Program Expedition 331).

PubMed

Yanagawa, Katsunori; Breuker, Anja; Schippers, Axel; Nishizawa, Manabu; Ijiri, Akira; Hirai, Miho; Takaki, Yoshihiro; Sunamura, Michinari; Urabe, Tetsuro; Nunoura, Takuro; Takai, Ken

2014-10-01

The impacts of lithologic structure and geothermal gradient on subseafloor microbial communities were investigated at a marginal site of the Iheya North hydrothermal field in the Mid-Okinawa Trough. Subsurface marine sediments composed of hemipelagic muds and volcaniclastic deposits were recovered through a depth of 151 m below the seafloor at site C0017 during Integrated Ocean Drilling Program Expedition 331. Microbial communities inferred from 16S rRNA gene clone sequencing in low-temperature hemipelagic sediments were mainly composed of members of the Chloroflexi and deep-sea archaeal group. In contrast, 16S rRNA gene sequences of marine group I Thaumarchaeota dominated the microbial phylotype communities in the coarse-grained pumiceous gravels interbedded between the hemipelagic sediments. Based on the physical properties of sediments such as temperature and permeability, the porewater chemistry, and the microbial phylotype compositions, the shift in the physical properties of the sediments is suggested to induce a potential subseafloor recharging flow of oxygenated seawater in the permeable zone, leading to the generation of variable chemical environments and microbial communities in the subseafloor habitats. In addition, the deepest section of sediments under high-temperature conditions (∼90°C) harbored the sequences of an uncultivated archaeal lineage of hot water crenarchaeotic group IV that may be associated with the high-temperature hydrothermal fluid flow. These results indicate that the subseafloor microbial community compositions and functions at the marginal site of the hydrothermal field are highly affected by the complex fluid flow structure, such as recharging seawater and underlying hydrothermal fluids, coupled with the lithologic transition of sediments. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Significant role of organic sulfur in supporting sedimentary sulfate reduction in low-sulfate environments

NASA Astrophysics Data System (ADS)

Fakhraee, Mojtaba; Li, Jiying; Katsev, Sergei

2017-09-01

Dissimilatory sulfate reduction (DSR) is a major carbon mineralization pathway in aquatic sediments, soils, and groundwater, which regulates the production of hydrogen sulfide and the mobilization rates of biologically important elements such as phosphorus and mercury. It has been widely assumed that water-column sulfate is the main sulfur source to fuel this reaction in sediments. While this assumption may be justified in high-sulfate environments such as modern seawater, we argue that in low-sulfate environments mineralization of organic sulfur compounds can be an important source of sulfate. Using a reaction-transport model, we investigate the production of sulfate from sulfur-containing organic matter for a range of environments. The results show that in low sulfate environments (<500 μM) the in-sediment production of sulfate can support a substantial portion (>50%) of sulfate reduction. In well-oxygenated systems, porewater sulfate profiles often exhibit sub-interface peaks so that sulfate fluxes are directed out of the sediment. Our measurements in Lake Superior, the world's largest lake, corroborate this conclusion: offshore sediments act as sources rather than sinks of sulfate for the water column, and sediment DSR is supported entirely by the in-sediment production of sulfate. Sulfate reduction rates are correlated to the depth of oxygen penetration and strongly regulated by the supply of reactive organic matter; rate co-regulation by sulfate availability becomes appreciable below 500 μM level. The results indicate the need to consider the mineralization of organic sulfur in the biogeochemical cycling in low-sulfate environments, including several of the world's largest freshwater bodies, deep subsurface, and possibly the sulfate-poor oceans of the Early Earth.

Sorption and speciation of iodine in groundwater system: The roles of organic matter and organic-mineral complexes

NASA Astrophysics Data System (ADS)

Li, Junxia; Zhou, Hailing; Wang, Yanxin; Xie, Xianjun; Qian, Kun

2017-06-01

Characterizing the properties of main host of iodine in soil/sediment and the geochemical behaviors of iodine species are critical to understand the mechanisms of iodine mobilization in groundwater systems. Four surface soil and six subsurface sediment samples were collected from the iodine-affected area of Datong basin in northern China to conduct batch experiments and to evaluate the effects of NOM and/or organic-mineral complexes on iodide/iodate geochemical behaviors. The results showed that both iodine contents and kf-iodate values had positive correlations with solid TOC contents, implying the potential host of NOM for iodine in soil/sediment samples. The results of chemical removal of easily extracted NOM indicated that the NOM of surface soils is mainly composed of surface embedded organic matter, while sediment NOM mainly occurs in the form of organic-mineral complexes. After the removal of surface sorbed NOM, the decrease in kf-iodate value of treated surface soils indicates that surface sorbed NOM enhances iodate adsorption onto surface soil. By contrast, kf-iodate value increases in several H2O2-treated sediment samples, which was considered to result from exposed rod-like minerals rich in Fe/Al oxyhydroxide/oxides. After chemical removal of organic-mineral complexes, the lowest kf-iodate value for both treated surface soils and sediments suggests the dominant role of organic-mineral complexes on controlling the iodate geochemical behavior. In comparison with iodate, iodide exhibited lower affinities on all (un)treated soil/sediment samples. The understanding of different geochemical behaviors of iodine species helps to explain the occurrence of high iodine groundwater with iodate and iodide as the main species in shallow (oxidizing conditions) and deep (reducing conditions) groundwater.

Microbial Community Stratification Controlled by the Subseafloor Fluid Flow and Geothermal Gradient at the Iheya North Hydrothermal Field in the Mid-Okinawa Trough (Integrated Ocean Drilling Program Expedition 331)

PubMed Central

Breuker, Anja; Schippers, Axel; Nishizawa, Manabu; Ijiri, Akira; Hirai, Miho; Takaki, Yoshihiro; Sunamura, Michinari; Urabe, Tetsuro; Nunoura, Takuro; Takai, Ken

2014-01-01

The impacts of lithologic structure and geothermal gradient on subseafloor microbial communities were investigated at a marginal site of the Iheya North hydrothermal field in the Mid-Okinawa Trough. Subsurface marine sediments composed of hemipelagic muds and volcaniclastic deposits were recovered through a depth of 151 m below the seafloor at site C0017 during Integrated Ocean Drilling Program Expedition 331. Microbial communities inferred from 16S rRNA gene clone sequencing in low-temperature hemipelagic sediments were mainly composed of members of the Chloroflexi and deep-sea archaeal group. In contrast, 16S rRNA gene sequences of marine group I Thaumarchaeota dominated the microbial phylotype communities in the coarse-grained pumiceous gravels interbedded between the hemipelagic sediments. Based on the physical properties of sediments such as temperature and permeability, the porewater chemistry, and the microbial phylotype compositions, the shift in the physical properties of the sediments is suggested to induce a potential subseafloor recharging flow of oxygenated seawater in the permeable zone, leading to the generation of variable chemical environments and microbial communities in the subseafloor habitats. In addition, the deepest section of sediments under high-temperature conditions (∼90°C) harbored the sequences of an uncultivated archaeal lineage of hot water crenarchaeotic group IV that may be associated with the high-temperature hydrothermal fluid flow. These results indicate that the subseafloor microbial community compositions and functions at the marginal site of the hydrothermal field are highly affected by the complex fluid flow structure, such as recharging seawater and underlying hydrothermal fluids, coupled with the lithologic transition of sediments. PMID:25063666

Diversity and role of plasmids in adaptation of bacteria inhabiting the Lubin copper mine in Poland, an environment rich in heavy metals.

PubMed

Dziewit, Lukasz; Pyzik, Adam; Szuplewska, Magdalena; Matlakowska, Renata; Mielnicki, Sebastian; Wibberg, Daniel; Schlüter, Andreas; Pühler, Alfred; Bartosik, Dariusz

2015-01-01

The Lubin underground mine, is one of three mining divisions in the Lubin-Glogow Copper District in Lower Silesia province (Poland). It is the source of polymetallic ore that is rich in copper, silver and several heavy metals. Black shale is also significantly enriched in fossil organic matter in the form of long-chain hydrocarbons, polycyclic aromatic hydrocarbons, organic acids, esters, thiophenes and metalloporphyrins. Biological analyses have revealed that this environment is inhabited by extremophilic bacteria and fungi. Kupfershiefer black shale and samples of water, bottom and mineral sediments from the underground (below 600 m) Lubin mine were taken and 20 bacterial strains were isolated and characterized. All exhibited multi-resistant and hypertolerant phenotypes to heavy metals. We analyzed the plasmidome of these strains in order to evaluate the diversity and role of mobile DNA in adaptation to the harsh conditions of the mine environment. Experimental and bioinformatic analyses of 11 extrachromosomal replicons were performed. Three plasmids, including a broad-host-range replicon containing a Tn3 family transposon, carried genes conferring resistance to arsenic, cadmium, cobalt, mercury and zinc. Functional analysis revealed that the resistance modules exhibit host specificity, i.e., they may increase or decrease tolerance to toxic ions depending on the host strain. The other identified replicons showed diverse features. Among them we identified a catabolic plasmid encoding enzymes involved in the utilization of histidine and vanillate, a putative plasmid-like prophage carrying genes responsible for NAD biosynthesis, and two repABC-type plasmids containing virulence-associated genes. These findings provide an unique molecular insight into the pool of extrachromosomal replicons and highlight their role in the biology and adaptation of extremophilic bacteria inhabiting terrestrial deep subsurface.

Analyzing sources to sedimentary organic carbon in the Gulf of Urabá, southern Caribbean, using carbon stable isotopes

NASA Astrophysics Data System (ADS)

Rúa, Alex; Liebezeit, Gerd; Grajales, Heazel; Palacio, Jaime

2017-10-01

Carbon stable isotopes analysis serve reconstruction of the origin of organic matter (OM) deposited onto sediments. They also allow tracing vegetation change at different time scales. This study weighs the contribution of both marine and terrestrial sources to sedimentary organic carbon (OC) from a southwestern Caribbean Gulf partly surrounded by large Musa acuminata (banana) croplands. The δ13C values in three sediment cores from the gulf have slightly decreased over 1000 yrs BP, indicating enhanced terrestrial input of detrital carbon owing to river discharge. A two-end mixing model fed with these δ13C values showed that averaged terrestrial contribution of OC to sediment was 52.0% at prodelta, 76.4% at delta front, and 64.2% at Colombia Bay. This agrees well with sediment dynamics. The main source of sedimentary OC within the gulf was terrestrial instead of marine. In fact, a distorted trend in δ13C values for one of the coring sites could be the result of banana crop expansion through the 20th century.

Arsenic, vanadium, iron, and manganese biogeochemistry in a deltaic wetland, southern Louisiana, USA

DOE PAGES

Telfeyan, Katherine; Breaux, Alexander; Kim, Jihyuk; ...

2017-04-05

Geochemical cycling of the redox-sensitive trace elements arsenic (As) and vanadium (V) was examined in shallow pore waters from a marsh in an interdistributary embayment of the lower Mississippi River Delta. In particular, we explore how redox changes with depth and distance from the Mississippi River affect As and V cycling in the marsh pore waters. Previous geophysical surveys and radon mass balance calculations suggested that Myrtle Grove Canal and bordering marsh receive fresh groundwater, derived in large part from seepage of the Mississippi River, which subsequently mixes with brackish waters of Barataria Bay. In addition, the redox geochemistry ofmore » pore waters in the wetlands is affected by Fe and S cycling in the shallow subsurface (0-20 cm). Sediments with high organic matter content undergo SO 4 2- reduction, a process ubiquitous in the shallow subsurface but largely absent at greater depths (~3 m). Instead, at depth, in the absence of organic-rich sediments, Fe concentrations are elevated, suggesting that reduction of Fe(III) oxides/oxyhydroxides buffers redox conditions. Arsenic and V cycling in the shallow subsurface are decoupled from their behavior at depth, where both V and As appear to be removed from solution by either diffusion or adsorption onto, or co-precipitation with, authigenic minerals within the deeper aquifer sediments. Pore water As concentrations are greatest in the shallow subsurface (e.g., up to 315 nmol kg -1 in the top ~20 cm of the sediment) but decrease with depth, reaching values <30 nmol kg -1 at depths between 3 and 4 m. Vanadium concentrations appear to be tightly coupled to Fe cycling in the shallow subsurface, but at depth, V may be adsorbed to clay or sedimentary organic matter (SOM). Diffusive fluxes are calculated to examine the export of trace elements from the shallow marsh pore waters to the overlying canal water that floods the marsh. The computed fluxes suggest that the shallow sediment serves as a source of Fe, Mn, and As to the surface waters, whereas the sediments act as a sink for V. Iron and Mn fluxes are substantial, ranging from 50 to 30,000 and 770 to 4,300 nmol cm -2 day -1, respectively, whereas As fluxes are much less, ranging from 2.1 to 17 nmol cm -2 day -1. Vanadium fluxes range from 3.0 nmol cm -2 day -1 directed into the sediment to 1.7 nmol cm -2 day -1 directed out of the sediment« less

Arsenic, vanadium, iron, and manganese biogeochemistry in a deltaic wetland, southern Louisiana, USA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Telfeyan, Katherine; Breaux, Alexander; Kim, Jihyuk

Geochemical cycling of the redox-sensitive trace elements arsenic (As) and vanadium (V) was examined in shallow pore waters from a marsh in an interdistributary embayment of the lower Mississippi River Delta. In particular, we explore how redox changes with depth and distance from the Mississippi River affect As and V cycling in the marsh pore waters. Previous geophysical surveys and radon mass balance calculations suggested that Myrtle Grove Canal and bordering marsh receive fresh groundwater, derived in large part from seepage of the Mississippi River, which subsequently mixes with brackish waters of Barataria Bay. In addition, the redox geochemistry ofmore » pore waters in the wetlands is affected by Fe and S cycling in the shallow subsurface (0-20 cm). Sediments with high organic matter content undergo SO 4 2- reduction, a process ubiquitous in the shallow subsurface but largely absent at greater depths (~3 m). Instead, at depth, in the absence of organic-rich sediments, Fe concentrations are elevated, suggesting that reduction of Fe(III) oxides/oxyhydroxides buffers redox conditions. Arsenic and V cycling in the shallow subsurface are decoupled from their behavior at depth, where both V and As appear to be removed from solution by either diffusion or adsorption onto, or co-precipitation with, authigenic minerals within the deeper aquifer sediments. Pore water As concentrations are greatest in the shallow subsurface (e.g., up to 315 nmol kg -1 in the top ~20 cm of the sediment) but decrease with depth, reaching values <30 nmol kg -1 at depths between 3 and 4 m. Vanadium concentrations appear to be tightly coupled to Fe cycling in the shallow subsurface, but at depth, V may be adsorbed to clay or sedimentary organic matter (SOM). Diffusive fluxes are calculated to examine the export of trace elements from the shallow marsh pore waters to the overlying canal water that floods the marsh. The computed fluxes suggest that the shallow sediment serves as a source of Fe, Mn, and As to the surface waters, whereas the sediments act as a sink for V. Iron and Mn fluxes are substantial, ranging from 50 to 30,000 and 770 to 4,300 nmol cm -2 day -1, respectively, whereas As fluxes are much less, ranging from 2.1 to 17 nmol cm -2 day -1. Vanadium fluxes range from 3.0 nmol cm -2 day -1 directed into the sediment to 1.7 nmol cm -2 day -1 directed out of the sediment« less

Reoxidation of estuarine sediments during simulated resuspension events: Effects on nutrient and trace metal mobilisation

NASA Astrophysics Data System (ADS)

Vidal-Durà, Andrea; Burke, Ian T.; Stewart, Douglas I.; Mortimer, Robert J. G.

2018-07-01

Estuarine environments are considered to be nutrient buffer systems as they regulate the delivery of nutrients from rivers to the ocean. In the Humber Estuary (UK) seawater and freshwater mixing during tidal cycles leads to the mobilisation of oxic surface sediments (0-1 cm). However, less frequent seasonal events can also mobilise anoxic subsurface (5-10 cm) sediments, which may have further implications for the estuarine geochemistry. A series of batch experiments were carried out on surface and subsurface sediments taken from along the salinity gradient of the Humber Estuary. The aim was to investigate the geochemical processes driving major element (N, Fe, S, and Mn) redox cycling and trace metal behaviour during simulated resuspension events. The magnitude of major nutrient and metal release was significantly greater during the resuspension of outer estuarine sediments rather than from inner estuarine sediments. When comparing resuspension of surface versus subsurface sediment, only the outer estuary experiments showed significant differences in major nutrient behaviour with sediment depth. In general, any ammonium, manganese and trace metals (Cu and Zn) released during the resuspension experiments were rapidly removed from solution as new sorption sites (i.e. Fe/Mn oxyhydroxides) formed. Therefore Humber estuary sediments showed a scavenging capacity for these dissolved species and hence may act as an ultimate sink for these elements. Due to the larger aerial extent of the outer estuary intertidal mudflats in comparison with the inner estuary area, the mobilisation of the outer estuary sediments (more reducing and richer in sulphides and iron) may have a greater impact on the transport and cycling of nutrients and trace metals. Climate change-associated sea level rise combined with an increasing frequency of major storm events in temperate zones, which are more likely to mobilise deeper sediment regions, will impact the nutrient and metal inputs to the coastal waters, and therefore enhance the likelihood of eutrophication in this environment.

Structural parallels between terrestrial microbialites and Martian sediments: are all cases of `Pareidolia'?

NASA Astrophysics Data System (ADS)

Rizzo, Vincenzo; Cantasano, Nicola

2017-10-01

The study analyses possible parallels of the microbialite-known structures with a set of similar settings selected by a systematic investigation from the wide record and data set of images shot by NASA rovers. Terrestrial cases involve structures both due to bio-mineralization processes and those induced by bacterial metabolism, that occur in a dimensional field longer than 0.1 mm, at micro, meso and macro scales. The study highlights occurrence on Martian sediments of widespread structures like microspherules, often organized into some higher-order settings. Such structures also occur on terrestrial stromatolites in a great variety of `Microscopic Induced Sedimentary Structures', such as voids, gas domes and layer deformations of microbial mats. We present a suite of analogies so compelling (i.e. different scales of morphological, structural and conceptual relevance), to make the case that similarities between Martian sediment structures and terrestrial microbialites are not all cases of `Pareidolia'.

Terrestrial organic matter in surface sediments of the Baltic Sea, Northwest Europe, as determined by CuO oxidation

NASA Astrophysics Data System (ADS)

Miltner, Anja; Emeis, Kay-Christian

2001-04-01

We studied the distribution and composition of terrestrial organic matter in sediments of the Baltic Sea (Northwest Europe). To this end, surface sediments from all basins of the Baltic Sea were analyzed for their lignin oxidation product yields and compositions after CuO oxidation. Lignin oxidation product yields depend on the concentration of organic carbon and range from 0.4 to 10.2 mg g -1 total organic carbon (TOC). On the basis of an average of 13 mg g -1 TOC in two river sediments, we estimate that the upper limit of terrestrial organic matter in Baltic Sea sediments is 30% of TOC. The contribution of terrestrial organic matter differed between the individual basins, depending on the distance from runoff discharge areas and on the area occupied by each submarine catchment. Lignin composition showed a relative decrease of angiosperm tissue from the Southwest to the Northeast, reflecting the shift from temperate to boreal vegetation type. The Gotland and the Bornholm Seas, which have no significant river input, were characterized by high relative contributions of nonwoody, strongly altered material. The source may either be a mixture of pollen and peat being eroded from geologically older strata at the seafloor or laterally advected material from the other basins. However, the pronounced compositional differences between the basins indicated that interbasin transport of terrestrial organic matter is less important than direct river input, although river signals can only be traced at a few places in the Baltic Sea.

Biological formation of ethane and propane in the deep marine subsurface.

PubMed

Hinrichs, Kai-Uwe; Hayes, John M; Bach, Wolfgang; Spivack, Arthur J; Hmelo, Laura R; Holm, Nils G; Johnson, Carl G; Sylva, Sean P

2006-10-03

Concentrations and isotopic compositions of ethane and propane in cold, deeply buried sediments from the southeastern Pacific are best explained by microbial production of these gases in situ. Reduction of acetate to ethane provides one feasible mechanism. Propane is enriched in (13)C relative to ethane. The amount is consistent with derivation of the third C from inorganic carbon dissolved in sedimentary pore waters. At typical sedimentary conditions, the reactions yield free energy sufficient for growth. Relationships with competing processes are governed mainly by the abundance of H(2). Production of C(2) and C(3) hydrocarbons in this way provides a sink for acetate and hydrogen but upsets the general belief that hydrocarbons larger than methane derive only from thermal degradation of fossil organic material.

Biological formation of ethane and propane in the deep marine subsurface

PubMed Central

Hinrichs, Kai-Uwe; Hayes, John M.; Bach, Wolfgang; Spivack, Arthur J.; Hmelo, Laura R.; Holm, Nils G.; Johnson, Carl G.; Sylva, Sean P.

2006-01-01

Concentrations and isotopic compositions of ethane and propane in cold, deeply buried sediments from the southeastern Pacific are best explained by microbial production of these gases in situ. Reduction of acetate to ethane provides one feasible mechanism. Propane is enriched in 13C relative to ethane. The amount is consistent with derivation of the third C from inorganic carbon dissolved in sedimentary pore waters. At typical sedimentary conditions, the reactions yield free energy sufficient for growth. Relationships with competing processes are governed mainly by the abundance of H2. Production of C2 and C3 hydrocarbons in this way provides a sink for acetate and hydrogen but upsets the general belief that hydrocarbons larger than methane derive only from thermal degradation of fossil organic material. PMID:16990430

Sources and characteristics of terrestrial carbon in Holocene-scale sediments of the East Siberian Sea

NASA Astrophysics Data System (ADS)

Keskitalo, Kirsi; Tesi, Tommaso; Bröder, Lisa; Andersson, August; Pearce, Christof; Sköld, Martin; Semiletov, Igor P.; Dudarev, Oleg V.; Gustafsson, Örjan

2017-09-01

Thawing of permafrost carbon (PF-C) due to climate warming can remobilise considerable amounts of terrestrial carbon from its long-term storage to the marine environment. PF-C can be then be buried in sediments or remineralised to CO2 with implications for the carbon-climate feedback. Studying historical sediment records during past natural climate changes can help us to understand the response of permafrost to current climate warming. In this study, two sediment cores collected from the East Siberian Sea were used to study terrestrial organic carbon sources, composition and degradation during the past ˜ 9500 cal yrs BP. CuO-derived lignin and cutin products (i.e., compounds solely biosynthesised in terrestrial plants) combined with δ13C suggest that there was a higher input of terrestrial organic carbon to the East Siberian Sea between ˜ 9500 and 8200 cal yrs BP than in all later periods. This high input was likely caused by marine transgression and permafrost destabilisation in the early Holocene climatic optimum. Based on source apportionment modelling using dual-carbon isotope (Δ14C, δ13C) data, coastal erosion releasing old Pleistocene permafrost carbon was identified as a significant source of organic matter translocated to the East Siberian Sea during the Holocene.

Implications of Earth analogs to Martian sulfate-filled Fractures

NASA Astrophysics Data System (ADS)

Holt, R. M.; Powers, D. W.

2017-12-01

Sulfate-filled fractures in fine-grained sediments on Mars are interpreted to be the result of fluid movement during deep burial. Fractures in the Dewey Lake (aka Quartermaster) Formation of southeastern New Mexico and west Texas are filled with gypsum that is at least partially synsedimentary. Sulfate in the Dewey Lake takes two principal forms: gypsum cement and gypsum (mainly fibrous) that fills fractures ranging from horizontal to vertical. Apertures are mainly mm-scale, though some are > 1 cm. The gypsum is antitaxial, fibrous, commonly approximately perpendicular to the wall rock, and displays suture lines and relics of the wall rock. Direct evidence of synsedimentary, near-surface origin includes gypsum intraclasts, intraclasts that include smaller intraclasts that contain gypsum clasts, intraclasts of gypsum with suture lines, gypsum concentrated in small desiccation cracks, and intraclasts that include fibrous gypsum-filled fractures that terminate at the eroded clast boundary. Dewey Lake fracture fillings suggest that their Martian analogs may also have originated in the shallow subsurface, shortly following the deposition of Martian sediments, in the presence of shallow aquifers.

A new interpretation of seismic tomography in the southern Dead Sea basin using neural network clustering techniques

NASA Astrophysics Data System (ADS)

Braeuer, Benjamin; Bauer, Klaus

2015-11-01

The Dead Sea is a prime location to study the structure and development of pull-apart basins. We analyzed tomographic models of Vp, Vs, and Vp/Vs using self-organizing map clustering techniques. The method allows us to identify major lithologies by their petrophysical signatures. Remapping the clusters into the subsurface reveals the distribution of basin sediments, prebasin sedimentary rocks, and crystalline basement. The Dead Sea basin shows an asymmetric structure with thickness variation from 5 km in the west to 13 km in the east. Most importantly, we identified a distinct, well-defined body under the eastern part of the basin down to 18 km depth. Considering its geometry and petrophysical signature, this unit is interpreted as a buried counterpart of the shallow prebasin sediments encountered outside of the basin and not as crystalline basement. The seismicity distribution supports our results, where events are concentrated along boundaries of the basin and the deep prebasin sedimentary body. Our results suggest that the Dead Sea basin is about 4 km deeper than assumed from previous studies.

Microbially catalyzed nitrate-dependent metal/radionuclide oxidation in shallow subsurface sediments

NASA Astrophysics Data System (ADS)

Weber, K.; Healy, O.; Spanbauer, T. L.; Snow, D. D.

2011-12-01

Anaerobic, microbially catalyzed nitrate-dependent metal/radionuclide oxidation has been demonstrated in a variety of sediments, soils, and groundwater. To date, studies evaluating U bio-oxidation and mobilization have primarily focused on anthropogenically U contaminated sites. In the Platte River Basin U originating from weathering of uranium-rich igneous rocks in the Rocky Mountains was deposited in shallow alluvial sediments as insoluble reduced uranium minerals. These reduced U minerals are subject to reoxidation by available oxidants, such nitrate, in situ. Soluble uranium (U) from natural sources is a recognized contaminant in public water supplies throughout the state of Nebraska and Colorado. Here we evaluate the potential of anaerobic, nitrate-dependent microbially catalyzed metal/radionuclide oxidation in subsurface sediments near Alda, NE. Subsurface sediments and groundwater (20-64ft.) were collected from a shallow aquifer containing nitrate (from fertilizer) and natural iron and uranium. The reduction potential revealed a reduced environment and was confirmed by the presence of Fe(II) and U(IV) in sediments. Although sediments were reduced, nitrate persisted in the groundwater. Nitrate concentrations decreased, 38 mg/L to 30 mg/L, with increasing concentrations of Fe(II) and U(IV). Dissolved U, primarily as U(VI), increased with depth, 30.3 μg/L to 302 μg/L. Analysis of sequentially extracted U(VI) and U(IV) revealed that virtually all U in sediments existed as U(IV). The presence of U(IV) is consistent with reduced Fe (Fe(II)) and low reduction potential. The increase in aqueous U concentrations with depth suggests active U cycling may occur at this site. Tetravalent U (U(IV)) phases are stable in reduced environments, however the input of an oxidant such as oxygen or nitrate into these systems would result in oxidation. Thus co-occurrence of nitrate suggests that nitrate could be used by bacteria as a U(IV) oxidant. Most probable number enumeration of nitrate-dependent U(IV) oxidizing microorganisms demonstrated an abundant community ranging from 1.61x104 to 2.74x104 cells g-1 sediment. Enrichments initiated verified microbial U reduction and U oxidation coupled to nitrate reduction. Sediment slurries were serially diluted and incubated over a period of eight weeks and compared to uninoculated controls. Oxidation (0-4,554 μg/L) and reduction (0-55 μg/L) of U exceeded uninoculated controls further providing evidence of a U biogeochemical cycling in these subsurface sediments. The oxidation of U(IV) could contribute to U mobilization in the groundwater and result in decreased water quality. Not only could nitrate serve as an oxidant, but Fe(III) could also contribute to U mobilization. Nitrate-dependent Fe(II) oxidation is an environmentally ubiquitous process facilitated by a diversity of microorganisms. Additional research is necessary in order to establish a role of biogenic Fe(III) oxides in U geochemical cycling at this site. These microbially mediated processes could also have a confounding effect on uranium mobility in subsurface environments.

An Ocean Basin of Dirt? Using Molecular Biomarkers and Radiocarbon to Identify Organic Carbon Sources and their Preservation in the Arctic Ocean

NASA Astrophysics Data System (ADS)

Harvey, H.; Belicka, L. L.

2005-12-01

In the modern Arctic Ocean, primary production in waters over the broad continental shelves and under ice contributes an estimated 250 Mt/yr of POC to Arctic waters. The delivery of terrestrial material from large rivers, ice transport and through coastal erosion adds at least an additional 12 Mt/yr of POC. Although the marine organic carbon signal in Arctic Ocean exceeds that of terrestrial carbon by an order or magnitude or more, recent evidence suggests that this balance is not maintained and significant fractions of terrestrial carbon is preserved in sediments. Using an integrated approach combining lipid biomarkers and radiocarbon dating in particles and sediments, the process of organic carbon recycling and historical changes in its sources and preservation has been examined. A suite of lipid biomarkers in particles and sediments of western Arctic shelves and basins were measured and principle components analysis (PCA) used to allow a robust comparison among the 120+ individual compounds to assign organic sources and relative inputs. Offshore particles from the chlorophyll maximum contained abundant algal markers (e.g. 20:5 and 22:6 FAMEs), low concentrations of terrestrial markers (amyrins and 24-ethylcholest-5-en-3b-ol), and reflected modern 14C values. Particles present in deeper halocline waters also reflect marine production, but a portion of older, terrestrial carbon accompanies the sinking of the spring bloom. Surface and deeper sediments of basins contain older organic carbon and low concentrations of algal biomarkers, suggesting that marine carbon produced in surface waters is rapidly recycled. Taken together, these observations suggest that marine derived organic matter produced in shallow waters fuels carbon cycling, but relatively small amounts are preserved in sediments. As a result, the organic carbon preserved in sediments contrasts sharply to that typically observed in lower latitudes, with an increasing terrestrial signature with distance from land and potential for significant changes under a changing climate.

Characterization of ecological risks at the Milltown Reservoir-Clark Fork River Sediments Superfund Site, Montana

USGS Publications Warehouse

Pascoe, Gary A.; Blanchet, Richard J.; Linder, Greg L.; Palawski, Don; Brumbaugh, William G.; Canfield, Tim J.; Kemble, Nile E.; Ingersoll, Chris G.; Farag, Aïda M.; DalSoglio, Julie A.

1994-01-01

A comprehensive field and laboratory approach to the ecological risk assessment for the Milltown Reservoir-Clark Fork River Sediments Site, a Superfund site in the Rocky Mountains of Montana, has been described in the preceding reports of this series. The risk assessment addresses concerns over the ecological impacts of upstream releases of mining wastes to fisheries of the upper Clark Fork River (CFR) and the benthic and terrestrial habitats further downstream in Milltown Reservoir. The risk characterization component of the process integrated results from a triad of information sources: (a) chemistry studies of environmental media to identify and quantify exposures of terrestrial and aquatic organisms to site-related contaminants; (b) ecological or population studies of terrestrial vegetation, birds, benthic communities, and fish; and (c) in situ and laboratory toxicity studies with terrestrial and aquatic invertebrates and plants, small mammals, amphibians, and fish exposed to contaminated surface water, sediments, wetland soils, and food sources. Trophic transfer studies were performed on waterfowl, mammals, and predatory birds using field measurement data on metals concentrations in environmental media and lower trophic food sources. Studies with sediment exposures were incorporated into the Sediment Quality Triad approach to evaluate risks to benthic ecology. Overall results of the wetland and terrestrial studies suggested that acute adverse biological effects were largely absent from the wetland; however, adverse effects to reproductive, growth, and physiological end points of various terrestrial and aquatic species were related to metals exposures in more highly contaminated depositional areas. Feeding studies with contaminated diet collected from the upper CFR indicated that trout are at high risk from elevated metals concentrations in surface water, sediment, and aquatic invertebrates. Integration of chemical analyses with toxicological and ecological evaluations of metal effects on the wetland and fishery has provided an important foundation for environmental decisions at this site.

Structure and function of subsurface microbial communities affecting radionuclide transport and bioimmobilization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kostka, Joel E.; Prakash, Om; Green, Stefan J.

2012-05-01

Our objectives were to: 1) isolate and characterize novel anaerobic prokaryotes from subsurface environments exposed to high levels of mixed contaminants (U(VI), nitrate, sulfate), 2) elucidate the diversity and distribution of metabolically active metal- and nitrate-reducing prokaryotes in subsurface sediments, and 3) determine the biotic and abiotic mechanisms linking electron transport processes (nitrate, Fe(III), and sulfate reduction) to radionuclide reduction and immobilization. Mechanisms of electron transport and U(VI) transformation were examined under near in situ conditions in sediment microcosms and in field investigations. Field sampling was conducted at the Oak Ridge Field Research Center (ORFRC), in Oak Ridge, Tennessee. Themore » ORFRC subsurface is exposed to mixed contamination predominated by uranium and nitrate. In short, we effectively addressed all 3 stated objectives of the project. In particular, we isolated and characterized a large number of novel anaerobes with a high bioremediation potential that can be used as model organisms, and we are now able to quantify the function of subsurface sedimentary microbial communities in situ using state-of-the-art gene expression methods (molecular proxies).« less

Clays and Carbonates in a Groundwater-Fed 3.8 Ga Martian Lake: Insights to Subsurface Habitability on Mars

NASA Technical Reports Server (NTRS)

Michalski, Joseph; Niles, Paul

2015-01-01

On Earth, the deep biosphere remains a largely unexplored, but clearly important carbon reservoir. Results from some uplifted central peaks in craters on Mars indicate that substantial carbon was also present at depth and might have helped sustain a deep biosphere. In fact, many factors relevant to deep biosphere habitability are more favorable on Mars than on Earth (e.g. porosity of the crust, geothermal gradient). Future exploration of Mars should include landing sites where materials have been exhumed from depth by meteor impact or basins where subsurface fluids have emerged, carrying clues to subsurface habitability. One of the most astrobiologically interesting sites on Mars McLaughlin Crater, a 93 km-diameter impact crater that formed approximately 4 b.y. ago. On the floor of the crater is a stratigraphic section of subhorizontal, layered sedimentary rocks with strong spectroscopic evidence for Fe-rich clay minerals and Mg-rich carbonates, which we interpret as ancient lacustrine deposits. The fluids that formed these materials likely originated in the subsurface, based on the paucity of channels leading into the crater basin and the fact that this is one of the deepest basins on Mars - a good candidate to have experienced upwelling of subsurface fluids. Therefore, the deposits within McLaughlin crater provide insight into subsurface processes on Mars. In this presentation, we will discuss the habitability of the martian subsurface as well as the geology of McLaughlin Crater and the possibility to detect biomarkers at that site with a future landed mission.

Estimating changes in carbon burial on the western US coastal shelf due to anthropogenic influences on river exports

NASA Astrophysics Data System (ADS)

Sauer, M.; Bergamaschi, B. A.; Smith, R. A.; Zhu, Z.; Shih, J.

2012-12-01

Flux of nutrients and sediments to the coastal zone varies in response to land-use modification, reservoir construction, management action and population change. It is anticipated that future changes in the flux of these components in response to climate and terrestrial processes will affect carbon (C) burial in the coastal ocean. Coastal oceans store appreciable amounts of C as a result of river inflows: coastal primary production is enhanced by inputs of terrestrially derived nutrients, and C burial is controlled by terrestrial sediment supply. Assessing the capacity and changes to coastal C preservation, therefore, requires estimation of (1) riverine nutrient and sediment delivery to the coastal ocean, and (2) the enhanced C production and sediment deposition in the coastal ocean. The United States Geological Survey (USGS) has embarked on a congressionally-mandated nationwide effort to assess the future effects of climate and land use and land cover change (LULC) on C storage. The USGS has developed alternative scenarios for changes in US LULC from 2006 to 2100 based on the Intergovernmental Panel on Climate Change (IPCC) climate, economic, and demographic scenarios (Sohl et al 2012). These spatially-detailed scenarios provide inputs to national-scale SPARROW watershed models of total nitrogen, total phosphorus, total organic C (TOC), and suspended sediment (Smith et al 1997; Schwarz et al, 2006). The watershed models, in turn, provide inputs of nutrients, TOC, and sediment to a coupled model of coastal transport, production, and sedimentation. This coastal modelling component includes particulate C sedimentation and burial estimated as functions of bathymetry and pycnocline depth (Armstrong, et al 2002; Dunne et al 2007). River borne fluxes of TOC to US Pacific coastal waters under baseline conditions (1992) were 1.59 TgC/yr. Projected future (2050) fluxes under a regionally-downscaled LULC scenario aligned with the IPCC A2 scenario were similar (1.61TgC/yr). C storage in coastal environments as influenced by terrestrial processes represents a significant sink for C in comparison to terrestrial biomass C sinks, and is significantly sensitive to changes in LULC and population. The estimated rate of storage in Pacific coastal waters was 2.0 TgC/yr under baseline conditions. Projection of land use and population changes through 2050 associated with the IPCC A2 scenario had a small effect on coastal C storage processes, reducing C storage by 4% over baseline conditions. Results of this modeling exercise indicate that the size of the C sink associated with terrestrial exports is substantial and sensitive to anthropogenic activity. Thus, future assessments of how terrestrial policy and management actions may alter C storage should include an evaluation of the effects prospective alterations in terrestrial processes have on coastal C storage.

High frequency of phylogenetically diverse reductive dehalogenase-homologous genes in deep subseafloor sedimentary metagenomes

PubMed Central

Kawai, Mikihiko; Futagami, Taiki; Toyoda, Atsushi; Takaki, Yoshihiro; Nishi, Shinro; Hori, Sayaka; Arai, Wataru; Tsubouchi, Taishi; Morono, Yuki; Uchiyama, Ikuo; Ito, Takehiko; Fujiyama, Asao; Inagaki, Fumio; Takami, Hideto

2014-01-01

Marine subsurface sediments on the Pacific margin harbor diverse microbial communities even at depths of several hundreds meters below the seafloor (mbsf) or more. Previous PCR-based molecular analysis showed the presence of diverse reductive dehalogenase gene (rdhA) homologs in marine subsurface sediment, suggesting that anaerobic respiration of organohalides is one of the possible energy-yielding pathways in the organic-rich sedimentary habitat. However, primer-independent molecular characterization of rdhA has remained to be demonstrated. Here, we studied the diversity and frequency of rdhA homologs by metagenomic analysis of five different depth horizons (0.8, 5.1, 18.6, 48.5, and 107.0 mbsf) at Site C9001 off the Shimokita Peninsula of Japan. From all metagenomic pools, remarkably diverse rdhA-homologous sequences, some of which are affiliated with novel clusters, were observed with high frequency. As a comparison, we also examined frequency of dissimilatory sulfite reductase genes (dsrAB), key functional genes for microbial sulfate reduction. The dsrAB were also widely observed in the metagenomic pools whereas the frequency of dsrAB genes was generally smaller than that of rdhA-homologous genes. The phylogenetic composition of rdhA-homologous genes was similar among the five depth horizons. Our metagenomic data revealed that subseafloor rdhA homologs are more diverse than previously identified from PCR-based molecular studies. Spatial distribution of similar rdhA homologs across wide depositional ages indicates that the heterotrophic metabolic processes mediated by the genes can be ecologically important, functioning in the organic-rich subseafloor sedimentary biosphere. PMID:24624126