Science.gov

Sample records for anoxic basin nitinat

  1. Eastern Guaymas Basin: laminated but not anoxic

    NASA Astrophysics Data System (ADS)

    Cheshire, H.; Thurow, J. W.

    2009-12-01

    Site MD02-2513, eastern Guaymas Basin, challenges the accepted hypothesis about the circumstances and sequence of events leading to the occurrence of annually laminated (varved) sediment. By convention, under a climate regime of strong seasonal contrast, high productivity in a restricted basin enhances a preformed OMZ and inhibits bioturbation, resulting in the preservation of varves. The comparison of the high-resolution log of the sediment fabric and continuous XRF data from Core MD02-2513 reveal that laminated intervals over the last ~90 ka BP are characterised by an increase of oxygenation above background levels and are accompanied by lows of terrestrial and biogenic flux indicating that the preserving factor is rapid burial rather than high sedimentation rate (ie high seasonality and low rainfall). Intervals of diffuse/discontinuous laminations are times of high terrestrial and biogenic flux indicating comparatively low seasonality and high rainfall. Brief periods of relatively high anoxic conditions occur within homogeneous intervals and are accompanied by exceptionally high biogenic flux, indicating there was no seasonal contrast. Long homogenous intervals occur during the last glacial due to lowered sea level and the consequent removal of the upwelling cell offshore. The changes in Guaymas Basin seasonality are most probably caused by alterations to the migration pattern of the North Pacific Subtropical High due to the growth and decay of the North American ice sheets.

  2. The enigma of prokaryotic life in deep hypersaline anoxic basins.

    PubMed

    van der Wielen, Paul W J J; Bolhuis, Henk; Borin, Sara; Daffonchio, Daniele; Corselli, Cesare; Giuliano, Laura; D'Auria, Giuseppe; de Lange, Gert J; Huebner, Andreas; Varnavas, Sotirios P; Thomson, John; Tamburini, Christian; Marty, Danielle; McGenity, Terry J; Timmis, Kenneth N

    2005-01-07

    Deep hypersaline anoxic basins in the Mediterranean Sea are a legacy of dissolution of ancient subterranean salt deposits from the Miocene period. Our study revealed that these hypersaline basins are not biogeochemical dead ends, but support in situ sulfate reduction, methanogenesis, and heterotrophic activity. A wide diversity of prokaryotes was observed, including a new, abundant, deeply branching order within the Euryarchaeota. Furthermore, we demonstrated the presence of a unique, metabolically active microbial community in the Discovery basin, which is one of the most extreme terrestrial saline environments known, as it is almost saturated with MgCl2 (5 M).

  3. Microbial Biomass and Activity Distribution in an Anoxic, Hypersaline Basin

    PubMed Central

    LaRock, Paul A.; Lauer, Ray D.; Schwarz, John R.; Watanabe, Kathleen K.; Wiesenburg, Denis A.

    1979-01-01

    The Orca Basin is a hypersaline depression in the northern Gulf of Mexico with anoxic conditions observed in the lower 200 m of the water column. Measurements of adenosine 5′-triphosphate, heterotrophic potential, and uridine uptake made above and across the interface into the anoxic zone revealed the presence of an active microbial population approximately 100 m above the interface. Biomass and activity decreased at and just below the interface but increased near the bottom, consistent with similar observations made in the Cariaco Trench. The maximum adenosine 5′-triphosphate concentration above the interface of 5.9 ng/liter (2,173 m) is about eight times greater than the value found in oxygenated waters of corresponding depth in the absence of an anoxic zone. The maximum adenosine 5′-triphosphate concentration in the anoxic zone is approximately 15 times greater than that found in oxygenated water of similar depth, suggesting anoxia will support the development of a larger bacterial population. Our findings suggest that autotrophic bacteria may be the dominant physiological group in the region just above the interface. PMID:16345355

  4. Predictive isotopic biogeochemistry: hydrocarbons from anoxic marine basins

    NASA Technical Reports Server (NTRS)

    Freeman, K. H.; Wakeham, S. G.; Hayes, J. M.

    1994-01-01

    Carbon isotopic compositions were determined for individual hydrocarbons in water column and sediment samples from the Cariaco Trench and Black Sea. In order to identify hydrocarbons derived from phytoplankton, the isotopic compositions expected for biomass of autotrophic organisms living in surface waters of both localities were calculated based on the concentrations of CO2(aq) and the isotopic compositions of dissolved inorganic carbon. These calculated values are compared to measured delta values for particulate organic carbon and for individual hydrocarbon compounds. Specifically, we find that lycopane is probably derived from phytoplankton and that diploptene is derived from the lipids of chemoautotrophs living above the oxic/anoxic boundary. Three acyclic isoprenoids that have been considered markers for methanogens, pentamethyleicosane and two hydrogenated squalenes, have different delta values and apparently do not derive from a common source. Based on the concentration profiles and isotopic compositions, the C31 and C33 n-alkanes and n-alkenes have a similar source, and both may have a planktonic origin. If so, previously assigned terrestrial origins of organic matter in some Black Sea sediments may be erroneous.

  5. Lower Cretaceous anoxic conditions IN the Austral basin, south-western Gondwana, Patagonia Argentina

    NASA Astrophysics Data System (ADS)

    Richiano, Sebastián

    2014-10-01

    The reconstruction of palaeo-oxygenation levels in marine deposits from the Cretaceous has obtained a huge interest all around the world in recent years. This fascinating topic is here pointed out for the first time in the Austral Basin using the information provided by the black shales of the Río Mayer Formation, Patagonia, Argentina. The combination of sedimentology, ichnology and geochemistry (TOC, Ce anomaly and MnO content) allow the identification of three major intervals respecting the oxygen content. During the Berriasian and early Valanginian anoxic conditions prevail in the outer shelf. After that, between the late Valanginian and Hauterivian dysoxic palaeoenvironments were developed. Finally, a more oxygenated palaeoenvironment occurred since Aptian associated with a progradation of a proximal deltaic system. The identification of anoxic conditions is of much interest for the hydrocarbon research in this stratigraphical unit, which represents the most significant source rock of the Austral Basin.

  6. The Baltic Inflow Event 2014 and its Biogeochemical Response in the Anoxic Central Baltic Basins

    NASA Astrophysics Data System (ADS)

    Schulz-Bull, D. E.; Naumann, M.; Mohrholz, V.; Nausch, G.; Prien, R. D.

    2016-02-01

    The brackish Baltic Sea and the deeper anoxic basins in the central parts are occasionally ventilated by the intrusion of high saline and oxygen rich water from the North Atlantic entering the Baltic Sea. With a volume of 198 km3 containing 4 Gt salt, the inflow event in 2014 was the third largest ever observed. As a result the redox conditions in the anoxic parts of the Baltic Sea changed. In the Bornholm Basin and the Gotland Deep area the biogeochemical conditions for many elements and redox sensitive substances changed crucial by the inflow water. Oxidation of the hydrogen sulfide and consequent changes in the pH and the carbonate system were observed. Other chemicals such as the nitrogen nutrients, phosphate, trace metals and the dissolved organic matter react with the fresh inflow water ingredients. The chronological sequence of the biogeochemical reactions following the inflow event where monitored by autonomous stations and several ship expeditions in high spatial and temporal resolution.

  7. Viruses, prokaryotes and DNA in the sediments of a deep-hypersaline anoxic basin (DHAB) of the Mediterranean Sea.

    PubMed

    Danovaro, R; Corinaldesi, C; Dell'Anno, A; Fabiano, M; Corselli, C

    2005-04-01

    Viral and prokaryote abundance were investigated in a deep-hypersaline anoxic basin of the Eastern Mediterranean Sea (DHAB Atalante basin at c. 3000 m depth). This system was compared with two nearby deep-sea sites characterized by oxic conditions. Viral abundance and virus to prokaryote abundance ratio in hypersaline anoxic sediments displayed values close to those reported in oxic sites. The analysis of vertical profiles of viral abundance in the Atalante basin revealed the lack of significant changes with depth in the sediment, suggesting that benthic viruses in these anoxic and hypersaline conditions are preserved or resistant to decay. The anoxic basin displayed also very high concentrations of labile organic components (proteins and lipids) and extracellular DNA. These findings suggest that the DHAB sediments represent a reservoir for long-term preservation of benthic viruses and nucleic acids.

  8. Modeling the hydrodynamic interactions of deep anoxic lagoons with their source basins

    NASA Astrophysics Data System (ADS)

    Gianni, Areti; Zacharias, Ierotheos

    2012-09-01

    This study investigates the management of an extension of the anoxic water layers, from deeper to shallower environments, and aims to control the consequences in lagoon environments with great economic and ecological value. The physicochemical status in a deep anoxic lagoon (Aitoliko, Greece) was monitored and the spatial distribution of anoxic conditions in the bottom waters was the focal point. The study investigated the management of an extension of the anoxic water layers, from deeper to shallower environments, and aims to control the consequences in lagoon environments with great economic and ecological value. A three-dimensional numerical model was used in order to describe the hydrodynamic conditions in the lagoon. The model was calibrated and validated with field measurements and it was used as a tool to examine how morphological modifications in lagoon's sill and changes of the lagoon's salt/fresh water budget can affect water column hydrodynamics. The model reliably reproduced the hydrodynamic changes in the lagoon caused by morphological and/or hydraulic modification, demonstrating an ideal management plan for the control of deep anoxic hypolimnia. It is concluded that by decreasing fresh water discharges into a deep lagoon, epilimnetic density values increase while the metalimnion extends. By extending the sill's cross section, water fluxes with the source basin are increased, affecting the surface layer density. Even under these conditions fresh water discharges control the characteristics of a thin surface water layer. If the sill's cross section expansion is followed by a decrease of fresh water discharge, turbulence conditions in the water column of a deep basin are substantially affected.

  9. Hydrolytic ectoenzyme activity associated with suspended and sinking organic particles within the anoxic Cariaco Basin

    NASA Astrophysics Data System (ADS)

    Taylor, Gordon T.; Thunell, Robert; Varela, Ramon; Benitez-Nelson, Claudia; Scranton, Mary I.

    2009-08-01

    Ectohydrolase activities of suspended microbiota were compared to those associated with sinking particles (sed-POM) retrieved from sediment traps deployed in the permanently anoxic Cariaco Basin. In shore-based assays, activities of aminopeptidase, β-glucosidase, chitinase and alkaline phosphatase were measured in samples obtained from oxic and anoxic depths using MUF- and MCA-labeled fluorogenic substrate analogs. Hydrolysis potentials for these enzymes in the seston varied widely over the nine cruises sampled (8 Nov 1996-3 May 2000) and among depths (15-1265 m); from <10 to over 1600 nM d -1 hydrolysate released, generally co-varying with one another and with suspended particulate organic carbon (POC) and particulate nitrogen (PN). Hydrolytic potentials, prokaryotic abundances and POC/PN concentrations in sinking debris were 400-1.3×10 7 times higher than in comparable volumes of seawater. However when normalized to PN, hydrolytic potentials in sediment trap samples were not demonstrably higher than in Niskin bottle samples. We estimate that PN pools in sediment trap samples were turned over 2-1400 times (medians=7-26 x) slower by hydrolysis than were suspended PN pools. Median prokaryotic growth rates (divisions d -1) in sinking debris were also ˜150 times slower than for bacterioplankton. Hydrolytic potentials in surface oxic waters were generally faster than in underlying anoxic waters on a volumetric basis (nM hydrolysate d -1), but were not significantly ( p>0.05) different when normalized to PN or prokaryote abundances. Alkaline phosphatase was consistently the most active ectohydrolase in both sample types, suggesting that Cariaco Basin assemblages were adapted to decomposing phosphate esters in organic polymers. However, phosphorus limitation was not evident from nutrient inventories in the water column. Results support the hypothesis that efficiencies of polymer hydrolysis in anoxic waters are not inherently lower than in oxic waters.

  10. Microbial eukaryotes in the hypersaline anoxic L'Atalante deep-sea basin.

    PubMed

    Alexander, Eva; Stock, Alexandra; Breiner, Hans-Werner; Behnke, Anke; Bunge, John; Yakimov, Michail M; Stoeck, Thorsten

    2009-02-01

    The frontiers of eukaryote life in nature are still unidentified. In this study, we analysed protistan communities in the hypersaline (up to 365 g l(-1) NaCl) anoxic L'Atalante deep-sea basin located in the eastern Mediterranean Sea. Targeting 18S ribosomal RNA retrieved from the basin's lower halocline (3501 m depth) we detected 279 protistan sequences that grouped into 42 unique phylotypes (99% sequence similarity). Statistical analyses revealed that these phylotypes account only for a proportion of the protists inhabiting this harsh environment with as much as 50% missed by this survey. Most phylotypes were affiliated with ciliates (45%), dinoflagellates (21%), choanoflagelates (10%) and uncultured marine alveolates (6%). Sequences from other taxonomic groups like stramenopiles, Polycystinea, Acantharea and Euglenozoa, all of which are typically found in non-hypersaline deep-sea systems, are either missing or very rare in our cDNA clone library. Although many DHAB sequences fell within previously identified environmental clades, a large number branched relatively deeply. Phylotype richness, community membership and community structure differ significantly from a deep seawater reference community (3499 m depth). Also, the protistan community in the L'Atalante basin is distinctively different from any previously described hypersaline community. In conclusion, we hypothesize that extreme environments may exert a high selection pressure possibly resulting in the evolution of an exceptional and distinctive assemblage of protists. The deep hypersaline anoxic basins in the Mediterranean Sea provide an ideal platform to test for this hypothesis and are promising targets for the discovery of undescribed protists with unknown physiological capabilities.

  11. The isotopic composition of authigenic chromium in anoxic marine sediments: A case study from the Cariaco Basin

    NASA Astrophysics Data System (ADS)

    Reinhard, Christopher T.; Planavsky, Noah J.; Wang, Xiangli; Fischer, Woodward W.; Johnson, Thomas M.; Lyons, Timothy W.

    2014-12-01

    Chromium (Cr) isotopes are an emerging proxy for tracking redox processes at the Earth's surface. However, there has been limited exploration of the Cr isotope record of modern and recent marine sediments. The basic inorganic chemistry of Cr suggests that anoxic marine basins should factor prominently in the global Cr cycle and that sediments deposited within anoxic basins may offer a valuable Cr isotope archive throughout Earth's history. Here, we present δ53Cr data from sediments of the Cariaco Basin, Venezuela-a 'type' environment for large, perennially anoxic basins with a relatively strong hydrological connection to the global oceans. We document a marked positive shift in bulk δ53Cr values following the termination of the Last Glacial Maximum, followed by relative stasis. Based on a suite of independent redox proxies, this transition marks a switch from oxic to persistently anoxic and sulfidic (euxinic) depositional conditions within the basin. We find good agreement between two independent approaches toward estimating the δ53Cr composition of authigenic Cr in euxinic Cariaco Basin sediments and that these estimates are very similar to the δ53Cr composition of modern open Atlantic Ocean seawater. These data, together with considerations of reaction kinetics and mass balance within the Cariaco Basin, are consistent with the hypothesis that anoxic marine settings can serve as a chemical archive of first-order trends in seawater δ53Cr composition. Additionally, the Cariaco Basin data suggest that there has been secular stability in the average δ53Cr value of Atlantic seawater over the last ∼15 kyr.

  12. A high-resolution Late Quaternary upwelling record from the anoxic Cariaco Basin, Venezuela

    NASA Astrophysics Data System (ADS)

    Peterson, L. C.; Overpeck, J. T.; Kipp, N. G.; Imbrie, J.

    1991-02-01

    Results are presented of a high-resolution study of the planktonic foraminiferal faunas from two piston cores recovered from the Cariaco Basin in the southern Caribbean Sea. The Cariaco Basin is a small anoxic marine basin on the northern continental margin of Venezuela in an area today characterized by both seasonal trade wind-induced upwelling and pronounced dry and wet seasons. Our data indicate that large changes in the intensity of upwelling, and hence trade wind strength, occurred in this region during the last glacial-interglacial transition and throughout the Holocene. During the last glacial lowstand of sea level, the Cariaco Basin was effectively isolated from the open Caribbean along its northern margin by the then largely emergent Tortuga Bank. Oxic conditions existed in the deep Cariaco Basin at this time, and surface productivity was low. About 12,600 years ago, the abrupt initiation of strong upwelling over the basin and the onset of permanent anoxia in the deep waters are coincident with the rapid rise of sea level that accompanied the peak interval of meltwater discharge from the Laurentide Ice Sheet into the Gulf of Mexico. Strong upwelling between 12,600 and about 10,000 years ago may be related to intensified trade winds resulting, in part, from cooler sea surface temperatures in the Caribbean and Gulf of Mexico. After about 10,000 years ago, upwelling intensity was reduced, though highly variable. A preliminary frequency domain analysis of the Holocene portion of the Cariaco Basin time series suggests that solar forcing may explain a significant component of the century-scale variability observed in the record of upwelling and trade wind strength.

  13. Novel active kinetoplastids associated with hypersaline anoxic basins in the Eastern Mediterranean deep-sea

    NASA Astrophysics Data System (ADS)

    Edgcomb, V. P.; Orsi, W.; Breiner, H.-W.; Stock, A.; Filker, S.; Yakimov, M. M.; Stoeck, T.

    2011-10-01

    The combination of nearly saturated salt concentration and corresponding high density, high hydrostatic pressure, absence of light, anoxia, and a sharp chemocline make the deep hypersaline anoxic basins in the Eastern Mediterranean Sea some of the most polyextreme habitats on Earth. Using kinetoplastid-specific primers, we detected kinetoplastid flagellates in some of the harshest deep-sea environments known to date, including some whose small subunit ribosomal RNA gene sequences are not closely related to cultured representatives. Kinetoplastids, including presumably novel representatives appear to be specialists of halocline environments in the Eastern Mediterranean, and to comprise a significant fraction of the protist communities in the brines and haloclines of several basins. Fluorescent in situ hybridization data indicate a novel 'unidentified' sequence clade of kinetoplastids related to bodonids represents as much as 10% of the total protist community in the Discovery Basin halocline. Different kinetoplastid groups are unevenly represented in the different basins and habitats we sampled, which we discuss as a result of environmental selection.

  14. Unveiling microbial activities along the halocline of Thetis, a deep-sea hypersaline anoxic basin

    PubMed Central

    Pachiadaki, Maria G; Yakimov, Michail M; LaCono, Violetta; Leadbetter, Edward; Edgcomb, Virginia

    2014-01-01

    Deep-sea hypersaline anoxic basins (DHABs) in the Eastern Mediterranean Sea are considered some of the most hostile environments on Earth. Little is known about the biochemical adaptations of microorganisms living in these habitats. This first metatranscriptome analysis of DHAB samples provides significant insights into shifts in metabolic activities of microorganisms as physicochemical conditions change from deep Mediterranean sea water to brine. The analysis of Thetis DHAB interface indicates that sulfate reduction occurs in both the upper (7.0–16.3% salinity) and lower (21.4–27.6%) halocline, but that expression of dissimilatory sulfate reductase is reduced in the more hypersaline lower halocline. High dark-carbon assimilation rates in the upper interface coincided with high abundance of transcripts for ribulose 1,5-bisphosphate carboxylase affiliated to sulfur-oxidizing bacteria. In the lower interface, increased expression of genes associated with methane metabolism and osmoregulation is noted. In addition, in this layer, nitrogenase transcripts affiliated to uncultivated putative methanotrophic archaea were detected, implying nitrogen fixation in this anoxic habitat, and providing evidence of linked carbon, nitrogen and sulfur cycles. PMID:24950109

  15. Sulfate reduction and sulfide oxidation in anoxic confined aquifers in the northeastern Osaka Basin, Japan

    NASA Astrophysics Data System (ADS)

    Yamanaka, Masaru; Nakano, Takanori; Tase, Norio

    2007-03-01

    SummaryWe used δ 34S values and chemical compositions of groundwater to investigate the influence of sulfate reduction and sulfide oxidation processes in a confined aquifer system in the northeastern Osaka Basin (NEOB), central Japan. Shallow confined groundwater (<100 m) in the basin is recharged mainly from mountainous areas to the north, and flows south and southwest through the aquifer system. Anion composition of the groundwater is dominated by HCO3- throughout the basin. However, concentrations of redox-sensitive species such as dissolved oxygen, NO3-, Fe 2+, and Mn 2+ show that groundwater conditions become increasingly anoxic along the flowpaths. Moreover, SO 4/(SO 4 + 2HCO 3) molar ratios decrease with increasing δ 34S along the flowpaths, which demonstrates that sulfate is reduced in the NEOB aquifer system. Groundwater with both high total dissolved solids and high SO 4 content was observed mainly in areas down-flow from faults. Because of the high SO 4 content, the anion composition of this groundwater cannot be adequately explained by a simple sulfate reduction process. A Rayleigh distillation model with ɛ = -20‰, which allows for sulfide oxidation within marine sediments in proximity to faults, explains the chemistry of all groundwater samples, including those with high SO 4 content. The model demonstrates that 76% of initial sulfate is reduced at maximum, and that reduced SO42- content is up to 48.5 mg/L after sulfide oxidation in the NEOB aquifer system.

  16. Environmental selection of protistan plankton communities in hypersaline anoxic deep-sea basins, Eastern Mediterranean Sea

    PubMed Central

    Filker, Sabine; Stock, Alexandra; Breiner, Hans-Werner; Edgcomb, Virginia; Orsi, William; Yakimov, Michail M; Stoeck, Thorsten

    2013-01-01

    High salt concentrations, absence of light, anoxia, and high hydrostatic pressure make deep hypersaline anoxic basins (DHABs) in the Eastern Mediterranean Sea one of the most polyextreme habitats on Earth. Taking advantage of the unique chemical characteristics of these basins, we tested the effect of environmental selection and geographic distance on the structure of protistan communities. Terminal restriction fragment length polymorphism (T-RFLP) analyses were performed on water samples from the brines and seawater/brine interfaces of five basins: Discovery, Urania, Thetis, Tyro, and Medee. Using statistical analyses, we calculated the partitioning of diversity among the ten individual terminal restriction fragment (T-RF) profiles, based on peak abundance and peak incidence. While a significant distance effect on spatial protistan patterns was not detected, hydrochemical gradients emerged as strong dispersal barriers that likely lead to environmental selection in the DHAB protistan plankton communities. We identified sodium, magnesium, sulfate, and oxygen playing in concerto as dominant environmental drivers for the structuring of protistan plankton communities in the Eastern Mediterranean DHABs. PMID:23239531

  17. Chromium isotope composition of reducing and anoxic sediments from the Peru Margin and Cariaco Basin

    NASA Astrophysics Data System (ADS)

    Gueguen, B.; Planavsky, N.; Wang, X.; Algeo, T. J.; Peterson, L. C.; Reinhard, C. T.

    2014-12-01

    Chromium isotope systematics in marine sediments are now being used as a new redox proxy of the modern and ancient Earth's surface. Chromium is primarily delivered to the oceans by riverine inputs through weathering of Cr(III)-rich minerals present in the continental crust and oxidation of insoluble Cr(III) to soluble Cr(VI) species. Since oxidation-reduction reactions fractionate Cr isotopes whereby oxidized Cr(VI) species are preferentially enriched in heavy Cr isotopes, the Cr isotope composition of marine sediments may be useful tracers of redox conditions at the Earth's surface through geological time. Chromium is quantitatively removed in organic-rich sediments where reducing conditions prevail and promote reduction of Cr(VI) to Cr(III), and thus, these sediments should capture the ambient seawater Cr isotope composition. However, the isotopic composition of modern organic-rich sediments is poorly documented so far, and this step is essential for further modeling the global oceanic Cr isotope mass balance and assessing the effects of sedimentation and post-depositional processes on the marine Cr isotopes archive. In this study, we have characterized modern marine organic-rich sediments for their Cr isotope composition (δ53/52Cr) from two different settings, the Peru margin upwelling zone and the anoxic Cariaco Basin (Venezuela). Chromium isotopes were measured on a MC-ICP-MS (Nu Plasma) using a double-spike correction method. The authigenic fraction of shallow samples from the Peru margin sedimentary sequence with a high Total Organic Carbon (TOC) content (>10 wt%) yield an average δ53/52Crauthigenic value of +0.67 ±0.05 ‰ (2sd). However, although this value is close to the seawater value (Atlantic Ocean) and to Cariaco basin sediments (~ +0.6 ‰), reducing sediments from the Peru margin are on average isotopically slightly heavier, especially in samples having a low authigenic fraction and a low TOC content (δ53/52Crauthigenic values up to +1.30

  18. A new particulate Mn-Fe-P-shuttle at the redoxcline of anoxic basins

    NASA Astrophysics Data System (ADS)

    Dellwig, Olaf; Leipe, Thomas; März, Christian; Glockzin, Michael; Pollehne, Falk; Schnetger, Bernhard; Yakushev, Evgeniy V.; Böttcher, Michael E.; Brumsack, Hans-Jürgen

    2010-12-01

    Pelagic redoxclines of anoxic basins and deeps form the suboxic transition between oxygenated surface and anoxic or even sulfidic bottom waters. Intense element cycling, favoured by elevated microbial activity, causes steep gradients of physico-chemical parameters, nutrients and redox-sensitive trace metals. This study presents a conceptual model for authigenic particle formation at pelagic redoxclines, which is based on the tight coupling of Mn, Fe, and P cycles. Besides the well-known occurrence of Mn-oxides, textural (SEM-EDX) and geochemical (ICP-OES, ICP-MS) analyses of particles from the redoxclines of the Black Sea and the Baltic Sea (Gotland Basin, Landsort Deep) evidence the existence of earlier postulated Fe-oxyhydroxo-phosphates and emphasize mixed phases consisting of Mn-oxides and Fe-oxyhydroxo-phosphates as a new solid species. Most of the analyzed particles are star-shaped, of about 5 μm in size, and occur as single particles or aggregates without any morphological differences between Mn-oxides, Fe-oxyhydroxo-phosphates, and mixed phases. Throughout the redoxcline, these minerals show a general succession with maximum abundance of Mn-oxides above the redoxcline followed by mixed phases and almost pure Fe-phosphates within and below the redoxcline, respectively. Molar Fe/P ratios of single particles argue against the formation of known pure Fe-phosphates like vivianite or strengite at the lower end of the redox transition zone, but are consistent with recent experimental findings for colloidal P-bearing hydrous ferric oxides. Moreover, morphological similarities suggest the formation of irregular Fe-oxyhydroxo coatings due to oxidation of upward diffusing Fe 2+ by oxygen and stepwise replacement of Mn(IV) by Fe(III) on sinking MnO x particles followed by immediate adsorption or even co-precipitation of phosphate. Batch-type experiments using biogenic MnO x particles demonstrate the efficient potential of Fe 2+ oxidation by sinking MnO x particles

  19. Marine silicate weathering in the anoxic sediment of the Ulleung Basin: Evidence and consequences

    NASA Astrophysics Data System (ADS)

    Kim, Ji-Hoon; Torres, Marta E.; Haley, Brian A.; Ryu, Jong-Sik; Park, Myong-Ho; Hong, Wei-Li; Choi, Jiyoung

    2016-08-01

    Marine silicate weathering (MSiW) in anoxic sediments has been recently shown to be a significant sink for CO2 generated by methanogenesis. Independently, the roles of clay dehydration (illitization) in producing water and driving upward fluid advection have been well established in deep marine sediments, but to date the K+ source required for the reaction has not been established. Here we present chemical and strontium isotope properties of pore fluids from seven cores in the Ulleung Basin, which show radiogenic 87Sr/86Sr values (up to ˜0.71045), very high alkalinity values (maximum ˜130 mM), and enrichment in H4SiO4, Na+, K+, and Mg2+, consistent with MSiW. This reaction consumes CO2, generates alkalinity, and acts as a K+ source for illitization; water released from MSiW-supported illitization drives upward fluid flow. Our results highlight the importance of MSiW along continental margins and its underappreciated role in carbon cycling, silicate diagenesis, and hydrogeology of marine systems.

  20. Benthic protists and fungi of Mediterranean deep hypsersaline anoxic basin redoxcline sediments.

    PubMed

    Bernhard, Joan M; Kormas, Konstantinos; Pachiadaki, Maria G; Rocke, Emma; Beaudoin, David J; Morrison, Colin; Visscher, Pieter T; Cobban, Alec; Starczak, Victoria R; Edgcomb, Virginia P

    2014-01-01

    Some of the most extreme marine habitats known are the Mediterranean deep hypersaline anoxic basins (DHABs; water depth ∼3500 m). Brines of DHABs are nearly saturated with salt, leading many to suspect they are uninhabitable for eukaryotes. While diverse bacterial and protistan communities are reported from some DHAB water-column haloclines and brines, the existence and activity of benthic DHAB protists have rarely been explored. Here, we report findings regarding protists and fungi recovered from sediments of three DHAB (Discovery, Urania, L' Atalante) haloclines, and compare these to communities from sediments underlying normoxic waters of typical Mediterranean salinity. Halocline sediments, where the redoxcline impinges the seafloor, were studied from all three DHABs. Microscopic cell counts suggested that halocline sediments supported denser protist populations than those in adjacent control sediments. Pyrosequencing analysis based on ribosomal RNA detected eukaryotic ribotypes in the halocline sediments from each of the three DHABs, most of which were fungi. Sequences affiliated with Ustilaginomycotina Basidiomycota were the most abundant eukaryotic signatures detected. Benthic communities in these DHABs appeared to differ, as expected, due to differing brine chemistries. Microscopy indicated that only a low proportion of protists appeared to bear associated putative symbionts. In a considerable number of cases, when prokaryotes were associated with a protist, DAPI staining did not reveal presence of any nuclei, suggesting that at least some protists were carcasses inhabited by prokaryotic scavengers.

  1. Benthic protists and fungi of Mediterranean deep hypsersaline anoxic basin redoxcline sediments

    PubMed Central

    Bernhard, Joan M.; Kormas, Konstantinos; Pachiadaki, Maria G.; Rocke, Emma; Beaudoin, David J.; Morrison, Colin; Visscher, Pieter T.; Cobban, Alec; Starczak, Victoria R.; Edgcomb, Virginia P.

    2014-01-01

    Some of the most extreme marine habitats known are the Mediterranean deep hypersaline anoxic basins (DHABs; water depth ∼3500 m). Brines of DHABs are nearly saturated with salt, leading many to suspect they are uninhabitable for eukaryotes. While diverse bacterial and protistan communities are reported from some DHAB water-column haloclines and brines, the existence and activity of benthic DHAB protists have rarely been explored. Here, we report findings regarding protists and fungi recovered from sediments of three DHAB (Discovery, Urania, L’ Atalante) haloclines, and compare these to communities from sediments underlying normoxic waters of typical Mediterranean salinity. Halocline sediments, where the redoxcline impinges the seafloor, were studied from all three DHABs. Microscopic cell counts suggested that halocline sediments supported denser protist populations than those in adjacent control sediments. Pyrosequencing analysis based on ribosomal RNA detected eukaryotic ribotypes in the halocline sediments from each of the three DHABs, most of which were fungi. Sequences affiliated with Ustilaginomycotina Basidiomycota were the most abundant eukaryotic signatures detected. Benthic communities in these DHABs appeared to differ, as expected, due to differing brine chemistries. Microscopy indicated that only a low proportion of protists appeared to bear associated putative symbionts. In a considerable number of cases, when prokaryotes were associated with a protist, DAPI staining did not reveal presence of any nuclei, suggesting that at least some protists were carcasses inhabited by prokaryotic scavengers. PMID:25452749

  2. 6 ka anoxic condition in the Sibuyan Sea Basin, Philippines - possible link with an explosive eruption event?

    NASA Astrophysics Data System (ADS)

    Catane, S. G.; Fernando, A.; Peleo-Alampay, A.; Tejada, M. G.

    2010-12-01

    Marine tephra layers in Philippine inland seas were studied to evaluate the history of explosive volcanism in the region and their impact on the marine environment. Two discrete andesitic (SiO*blc*2*elc* = 55-63 wt%) tephra layers were found at depths 446.5-448.4 cm and 454.9-455.8 cm in the gravity core MD 3057 recovered during the Marion Dufresne Marco Polo 2 cruise in 2006. The 7m-long core was retrieved from the northern portion of the Sibuyan Sea Basin at 1660 m below sea level. A C-14 age of 6 ka was obtained for the lower tephra using benthic foraminifera collected immediately below the tephra layer. The tephra layers have similar major element compositions and follow the same fractionation trend on the basis of glass geochemistry. Compositions are distinct from the nearby active andesitic volcanoes, Taal and Mayon. Microprobe imaging showed the occurrence of authigenic pyrite within the lower andesitic tephra layer. Pyrite occurs as euhedral crystals or granular masses (framboids), which are isolated particles or foraminiferal infillings. Framboidal pyrite is associated with anoxic environments where anaerobic bacteria reduces SO*blc*4*elc* dissolved in sea water, initiating the formation of H*blc*2*elc*S. H2S reacts with iron in sediments to form pyrite. Anoxic conditions occur in ocean basins with restricted water exchange due to a physical barrier (sill), density stratification or where input of organic material is high. Alternatively, anoxic conditions may have been caused by the death of benthic organisms due to tephra deposition by depriving the organisms of their food supply. The effect of this apparent anoxic event on benthic foraminifera will be analyzed in detail. It is postulated that these anoxic conditions may cause a decline in the benthic foraminifera occurrence. The extent and duration of anoxic condition of the northern part of the Sibuyan Sea Basin 6 ka needs to be clarified because present-day water condition in the basin is normal. If

  3. Organic and black carbon 13C and 14C through the Santa Monica Basin sediment oxic-anoxic transition

    NASA Astrophysics Data System (ADS)

    Masiello, C. A.; Druffel, E. R. M.

    2003-02-01

    Black carbon (BC) is a significant percentage of sedimentary organic carbon (SOC) at abyssal ocean sites, but its presence in shelf sediments is not well studied. Approximately 1600AD, Santa Monica Basin bottom waters shifted from oxic to very low oxygen (dysoxic) deposition conditions. Under oxic deposition conditions BC was 11 +/- 4% of SOC, whereas after the overlying water became dysoxic (and sediments became anoxic), BC was 5.2 +/- 1.2% of SOC. This shift may reflect the preferential remineralization of non-black SOC under oxic conditions. There is an offset between BC and SOC 14C ages which changes with oxidation conditions, suggesting that BC storage is related to oxygen exposure and confirming a previously published report of the vulnerability of BC to sedimentary oxidation [Middelburg, 1999]. Terrestrial carbon is 17 +/- 5% of total SOC in this core's anoxic region, and 31 +/- 11% of this terrestrial carbon is BC.

  4. Basin-scale controls on the molybdenum-isotope composition of seawater during Oceanic Anoxic Event 2 (Late Cretaceous)

    NASA Astrophysics Data System (ADS)

    Dickson, Alexander J.; Jenkyns, Hugh C.; Porcelli, Donald; van den Boorn, Sander; Idiz, Erdem

    2016-04-01

    It is well established that the burial of organic carbon in marine sediments increased dramatically at a global scale at the Cenomanian-Turonian boundary (Oceanic Anoxic Event 2: OAE-2, ∼94 Myr ago, Late Cretaceous). Many localities containing chemostratigraphic expressions of this event are not, however, enriched in organic carbon, and point to a heterogeneous set of oceanographic and environmental processes operating in different ocean basins. These processes are difficult to reconstruct because of the uneven geographical distribution of sites recording OAE-2, thus limiting our understanding of the causes and palaeoceanographic consequences of the environmental changes that occurred at this time. A new, highly resolved molybdenum-isotope dataset is presented from the Cape Verde Basin (southern proto-North Atlantic Ocean) and a lower resolution record from the Tarfaya Basin, Morocco. The new data reveal periodic oscillations in the Mo-isotope composition of proto-North Atlantic Ocean sediments, from which coupled changes in the dissolved sulphide concentration and Mo inventories of the basin seawater can be inferred. The cyclic variations in sedimentary Mo-isotope compositions can be hypothetically linked to regional changes in the depth of the chemocline, and in the rate of seawater exchange between basinal waters and global seawater. The new data suggest that a global seawater Mo-isotope composition of ∼1.2‰ was reached very soon after the onset of OAE-2, implying a rapid expansion of marine deoxygenation coeval with, or slightly preceding, enhanced global rates of organic-carbon burial. During OAE-2, the modelled flux of Mo into anoxic sediments is likely to have been ∼60-125 times greater than at the present day, although the spatial extent of anoxia is unlikely to have been greater than 10% of the total seafloor.

  5. Comparison of vertical distributions of prokaryotic assemblages in the anoxic Cariaco Basin and Black Sea by use of fluorescence in situ hybridization.

    PubMed

    Lin, Xueju; Wakeham, Stuart G; Putnam, Isabell F; Astor, Yrene M; Scranton, Mary I; Chistoserdov, Andrei Y; Taylor, Gordon T

    2006-04-01

    Individual prokaryotic cells from two major anoxic basins, the Cariaco Basin and the Black Sea, were enumerated throughout their water columns using fluorescence in situ hybridization (FISH) with the fluorochrome Cy3 or horseradish peroxidase-modified oligonucleotide probes. For both basins, significant differences in total prokaryotic abundance and phylogenetic composition were observed among oxic, anoxic, and transitional (redoxcline) waters. Epsilon-proteobacteria, Crenarchaeota, and Euryarchaeota were more prevalent in the redoxclines, where previous studies reported high rates of chemoautotrophic production relative to those in waters above and below the redoxclines. Relative abundances of Archaea in both systems varied between 1% and 28% of total prokaryotes, depending on depth. The prokaryotic community composition varied between the two anoxic basins, consistent with distinct geochemical and physical conditions. In the Black Sea, the relative contributions of group I Crenarchaeota (median, 5.5%) to prokaryotic communities were significantly higher (P < 0.001; n = 20) than those of group II Euryarchaeota (median, 2.9%). In contrast, their proportions were nearly equivalent in the Cariaco Basin. Beta-proteobacteria were unexpectedly common throughout the Cariaco Basin's water column, accounting for an average of 47% of 4',6'-diamidino-2-phenylindole (DAPI)-stained cells. This group was below the detection limit (<1%) in the Black Sea samples. Compositional differences between basins may reflect temporal variability in microbial populations and/or systematic differences in environmental conditions and the populations for which they select.

  6. Protistan community patterns within the brine and halocline of deep hypersaline anoxic basins in the eastern Mediterranean Sea.

    PubMed

    Edgcomb, Virginia; Orsi, William; Leslin, Chesley; Epstein, Slava S; Bunge, John; Jeon, Sunok; Yakimov, Michail M; Behnke, Anke; Stoeck, Thorsten

    2009-01-01

    Environmental factors restrict the distribution of microbial eukaryotes but the exact boundaries for eukaryotic life are not known. Here, we examine protistan communities at the extremes of salinity and osmotic pressure, and report rich assemblages inhabiting Bannock and Discovery, two deep-sea superhaline anoxic basins in the Mediterranean. Using a rRNA-based approach, we detected 1,538 protistan rRNA gene sequences from water samples with total salinity ranging from 39 to 280 g/Kg, and obtained evidence that this DNA was endogenous to the extreme habitat sampled. Statistical analyses indicate that the discovered phylotypes represent only a fraction of species actually inhabiting both the brine and the brine-seawater interface, with as much as 82% of the actual richness missed by our survey. Jaccard indices (e.g., for a comparison of community membership) suggest that the brine/interface protistan communities are unique to Bannock and Discovery basins, and share little (0.8-2.8%) in species composition with overlying waters with typical marine salinity and oxygen tension. The protistan communities from the basins' brine and brine/seawater interface appear to be particularly enriched with dinoflagellates, ciliates and other alveolates, as well as fungi, and are conspicuously poor in stramenopiles. The uniqueness and diversity of brine and brine-interface protistan communities make them promising targets for protistan discovery.

  7. Oceanic Anoxic Event 1b: insights and new data from the Poggio le Guaine section (Umbria-Marche Basin)

    NASA Astrophysics Data System (ADS)

    Sabatino, Nadia; Sprovieri, Mario; Coccioni, Rodolfo; Salvagio Manta, Daniela; Gardin, Silvia; Baudin, François

    2015-04-01

    The upper Aptian to lower Albian interval (~114-109 Ma) represents a crucial period during Earth's history, with a major evolution in the nature of mid-Cretaceous tectonics, sea level, climate, and marine plankton communities. Interestingly, it also includes multiple prominent black shale horizons that are the sedimentary expression of oceanic anoxic event (OAE) 1b. An high-resolution planktonic foraminiferal and calcareous nannofossil biostratigraphy in combination with an integrated study of multiple geochemical proxies (δ13Ccarb, δ13Corg, TOC, HI, CaCO3, trace elements/Al ratios) of the late Aptian-early Albian OAE 1b has been performed on the pelagic sedimentary sequence of Poggio le Guaine (Umbria-Marche Basin, central Italy). A comparison of the newly collected stable isotope carbon curve with the records from the Vocontian Basin (SE France), DSDP Site 545 and Hole 1049C provided a reliable and precise identification of the four main prominent black shale levels (113/Jacob, Kilian, Urbino/Paquier and Leenhardt) that definitively punctuate the OAE 1b. The studied record shows an increase in the marine organic carbon accumulation rate, in particular in the 113/Jacob and Urbino/Paquier levels. In the other black shales, TOC values are < 1%, with evidence of degraded marine organic matter. Completely anoxic conditions were never established during the sediment deposition, although evidence of oxygen depletion at the bottom of the basin is clearly documented by the distribution pattern of redox-sensitive trace metals. The results suggest an increase in organic carbon burial rates during the OAE 1b due to the effect of enhanced surface productivity, as supported by a major increase in Ba/Al, and reduced bottom water ventilation. Noteworthy, the Kilian and Urbino/Paquier levels from the PLG section are characterized by the absence of correlative shifts in δ13Ccarb and δ13Corg. The increase in the δ13Corg, values in these levels is explained by an increase in

  8. Gene expression profiling of microbial activities and interactions in sediments under haloclines of E. Mediterranean deep hypersaline anoxic basins.

    PubMed

    Edgcomb, Virginia P; Pachiadaki, Maria G; Mara, Paraskevi; Kormas, Konstantinos A; Leadbetter, Edward R; Bernhard, Joan M

    2016-11-01

    Deep-sea hypersaline anoxic basins (DHABs) in the Eastern Mediterranean Sea are considered some of the most polyextreme habitats on Earth. In comparison to microbial activities occurring within the haloclines and brines of these unusual water column habitats near the Mediterranean seafloor, relatively little is known about microbial metabolic activities in the underlying sediments. In addition, it is not known whether activities are shaped by the unique chemistries of the different DHAB brines and whether evidence exists for active microbial eukaryotes in those sediments. Metatranscriptome analysis was applied to sediment samples collected using ROV Jason from underneath the haloclines of Urania, Discovery and L'Atalante DHABs and a control site. We report on expression of genes associated with sulfur and nitrogen cycling, putative osmolyte biosynthetic pathways and ion transporters, trace metal detoxification, selected eukaryotic activities (particularly of fungi), microbe-microbe interactions, and motility in sediments underlying the haloclines of three DHABs. Relative to our control sediment sample collected outside of Urania Basin, microbial communities (including eukaryotes) in the Urania and Discovery DHAB sediments showed upregulation of expressed genes associated with nitrogen transformations, osmolyte biosynthesis, heavy metals resistance and metabolism, eukaryotic organelle functions, and cell-cell interactions. Sediments underlying DHAB haloclines that have cumulative physico-chemical stressors within the limits of tolerance for microoorganisms can therefore be hotspots of activity in the deep Mediterranean Sea.

  9. Low Bacterial Diversity and High Labile Organic Matter Concentrations in the Sediments of the Medee Deep-Sea Hypersaline Anoxic Basin

    PubMed Central

    Akoumianaki, Ioanna; Nomaki, Hidetaka; Pachiadaki, Maria; Kormas, Konstantinos Ar.; Kitazato, Hiroshi; Tokuyama, Hidekazu

    2012-01-01

    Studies in the center and margin of the Medee Basin, a Mediterranean deep-sea hypersaline anoxic basin, and at a reference site during Penelope cruise (2007), revealed the existence of a 7 m-thick halocline, with high salinity (328 psu), and high sedimentary organic carbon and biopolymer concentrations. The 194 16S rRNA sequences retrieved were grouped into 118 unique phylotypes. Pseudomonas gessardii, dominated in the center, while 33 phylotypes were detected at the margin and 73 at the reference site. The study suggested conditions hostile to bacteria in the sediments of the Medee Basin and preservation of sedimentary labile organic matter. PMID:22504432

  10. Carbon dioxide production in surface sediments of temporarily anoxic basins (Baltic Sea) and resulting sediment-water interface fluxes

    NASA Astrophysics Data System (ADS)

    Böttcher, M. E.; Al-Raei, A. M.; Winde, V.; Lenz, C.; Dellwig, O.; Leipe, T.; Segl, M.; Struck, U.

    2009-04-01

    Organic matter is mineralized in marine sediments by microbial activity using predominantly oxygen, sulfate, and metal oxides as electron acceptors. Modern euxinic basins as found in the Baltic Sea or the Black Sea are of particular importance because they may serve as type systems for anoxia in Earth's history. We present here results from biogeochemical investigations carried out in the Baltic deeps (Gotland Basin, Landsort Deep) during the first scientific cruise of RV M.S. MERIAN in 2006, additionally during RV Prof. Penck cruises in 2006 and 2007. Short sediment cores were obtained with a multi-corer and analyzed for particulate and dissolved main, minor and trace elements, pH, DIC, methane alkalinity, besides the stable carbon isotopes of dissolved inorganic carbon (DIC). Microsensors were applied to analyze steep gradients of oxygen, sulphide and sulphate. Pore water profiles are evaluated in terms of process rates and associated element fluxes using the PROFILE software (Berg et al., 1998, L&O). Gross and net anaerobic mineralization rates were additionally obtained from core incubations with 35S. Steep gradients in DIC are associated with a strong enrichment of the light stable isotope resulting in the Gotland basin from oxidized OM. Element fluxes across the sediment-water interface are compared with literature data and show for the Baltic Sea a dependence from bottom water redox conditions, and sediment compositions and formation conditions (e.g., accumulation rates). DIC in the anoxic part of the water column in the Landsort Deep and the Gotland Deep show relatively similar isotope values, close to the bottom water value, but steep gradients towards heavier values above the pelagic redoxcline. Acknowledgements: The research was supported by Leibniz IO Warnemünde, DFG (Cruise RV MSM MERIAN 01), and MPG. Thanks to B. Schneider and F. Pollehne stimulating discussions, and S. Lage and A. Schipper for technical support.

  11. The dynamics of the bacterial diversity in the redox transition and anoxic zones of the Cariaco Basin assessed by parallel tag sequencing.

    PubMed

    Rodriguez-Mora, Maria J; Scranton, Mary I; Taylor, Gordon T; Chistoserdov, Andrei Y

    2015-09-01

    Massively parallel tag sequencing was applied to describe the bacterial diversity in the redox transition and anoxic zones of the Cariaco Basin. In total, 14 samples from the Cariaco Basin were collected over a period of eight years from two stations. A total of 244 357 unique bacterial V6 amplicons were sequenced. The total number of operational taxonomic units (OTUs) found in this study was 4692, with a range of 511-1491 OTUs per sample. Approximately 95% of the OTUs found in the redox transition zone and anoxic layers of Cariaco are represented by less than 50 amplicons suggesting that only about 5% of the bacterial OTUs are responsible for the bulk of the microbial processes in the basin redox transition and anoxic zones. The same dominant OTUs were observed across all eight years of sampling although periodic fluctuations in their proportion were apparent. No distinctive differences were observed between the bacterial communities from the redox transition and anoxic layers of the Cariaco Basin water column. The largest proportion of amplicons belongs to Gammaproteobacteria represented mostly by sulfide oxidizers, followed by Marine Group A (originally described as SAR406; Gordon and Giovannoni 1996), a group of uncultured bacteria hypothesized to be involved in metal reduction, and sulfate-reducing Deltaproteobacteria. Gammaproteobacteria, Deltaproteobacteria and Marine Group A make up 67-90% of all V6 amplicons sequenced in this study. This strongly suggests that the basin's microbial communities are actively involved in the sulfur-related metabolism and coupling of the sulfur and carbon cycles. According to detrended canonical correspondence analysis, ecological factors such as chemoautotrophy, nitrate and oxidized and reduced sulfur compounds influence the structuring and distribution of the Cariaco microbial communities.

  12. Extracellular DNA can preserve the genetic signatures of present and past viral infection events in deep hypersaline anoxic basins

    PubMed Central

    Corinaldesi, C.; Tangherlini, M.; Luna, G. M.; Dell'Anno, A.

    2014-01-01

    Deep hypersaline anoxic basins (DHABs) of the Mediterranean Sea are among the most extreme ecosystems on Earth and host abundant, active and diversified prokaryotic assemblages. However, factors influencing biodiversity and ecosystem functioning are still largely unknown. We investigated, for the first time, the impact of viruses on the prokaryotic assemblages and dynamics of extracellular DNA pool in the sediments of La Medee, the largest DHAB found on Earth. We also compared, in La Medee and L'Atalante sediments, the diversity of prokaryotic 16S rDNA sequences contained in the extracellular DNA released by virus-induced prokaryotic mortality. We found that DHAB sediments are hot-spots of viral infections, which largely contribute to the release of high amounts of extracellular DNA. DNase activities in DHAB sediments were much higher than other extracellular enzymatic activities, suggesting that extracellular DNA released from killed prokaryotes can be the most suitable trophic resource for benthic prokaryotes. Preserved extracellular DNA pools, which contained novel and diversified gene sequences, were very similar between the DHABs but dissimilar from the respective microbial DNA pools. We conclude that the strong viral impact in DHAB sediments influences the genetic composition of extracellular DNA, which can preserve the signatures of present and past infections. PMID:24523277

  13. Bio- and chemostratigraphy of the Early Aptian Oceanic Anoxic Event 1a within the mid-latitudes of northwest Europe (Germany, Lower Saxony Basin)

    NASA Astrophysics Data System (ADS)

    Heldt, Matthias; Mutterlose, Joerg; Berner, Uli; Erbacher, Jochen

    2013-04-01

    The Mid-Cretaceous period was characterised by a series of prominent anoxic events, one of these was the late Early Aptian Oceanic Anoxic Event 1a (OAE 1a). The Fischschiefer horizon is the regional sedimentary expression of this event in a small epicontinental sea in northwest Europe (Germany, Lower Saxony Basin). In the present study, two sediment cores of Lower to Upper Aptian age (Hoheneggelsen KB 9 and 40) from the Brunswick area, north Germany, have been investigated in detail with respect to their lithostratigraphy, geochemistry (CaCO3, TOC), biostratigraphy (coccoliths, nannoliths) and high-resolution chemostratigraphy (^13Ccarb and ^13Corg). Together with separately published new planktonic foraminifer data of the cores it was possible to establish a detailed time frame and to recognise the OAE 1a. The ^13C data enabled us to subdivide the deposits into isotope segments (C2-C7), which are commonly used as stratigraphic markers in coeval sediments around the world. The carbon isotope curves are compared to recently published Aptian curves from other parts of the Lower Saxony Basin, all of which record the prominent carbon isotope anomaly of the OAE 1a. A high-resolution correlation of the typical isotope trends of OAE 1a (segments C3-6) across the Lower Saxony Basin appears difficult due to an early diagenetic overprint of the primary isotope signal. These alterations can be explained by the temporary establishment of euxinic conditions the Lower Saxony Basin during OAE 1a as consequence of an interplay of different factors, such as global warming, restricted palaeogeography, increased fluvial input and intensified stable water stratification, which is supported by several lines of regional evidence.

  14. Environmental Conditions in a Carpathian Deep Sea Basin During the Period Preceding Oceanic Anoxic Event 2 - A Case Study from the Skole Nappe

    NASA Astrophysics Data System (ADS)

    Bąk, Krzysztof; Bąk, Marta; Górny, Zbigniew; Wolska, Anna

    2015-01-01

    Hemipelagic green clayey shales and thin muddy turbidites accumulated in a deep sea environment below the CCD in the Skole Basin, a part of the Outer Carpathian realm, during the Middle Cenomanian. The hemipelagites contain numerous radiolarians, associated with deep-water agglutinated foraminifera. These sediments accumulated under mesotrophic conditions with limited oxygen concentration. Short-term periodic anoxia also occurred during that time. Muddy turbidity currents caused deposition of siliciclastic and biogenic material, including calcareous foramini-fers and numerous sponge spicules. The preservation and diversity of the spicules suggests that they originate from disarticulation of moderately diversified sponge assemblages, which lived predominantly in the neritic-bathyal zone. Analyses of radiolarian ecological groups and pellets reflect the water column properties during the sedimentation of green shales. At that time, surface and also intermediate waters were oxygenated enough and sufficiently rich in nutri-ents to enable plankton production. Numerous, uncompacted pellets with nearly pristine radiolarian skeletons inside show that pelletization was the main factor of radiolarian flux into the deep basin floor. Partly dissolved skeletons indicate that waters in the Skole Basin were undersaturated in relation to silica content. Oxygen content might have been depleted in the deeper part of the water column causing periodic anoxic conditions which prevent rapid bacterial degra-dation of the pellets during their fall to the sea floor.

  15. Diversity of ribulose-1,5-bisphosphate carboxylase/oxygenase large-subunit genes in the MgCl2-dominated deep hypersaline anoxic basin discovery.

    PubMed

    van der Wielen, Paul W J J

    2006-06-01

    Partial sequences of the form I (cbbL) and form II (cbbM) of the ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) large subunit genes were obtained from the brine and interface of the MgCl2-dominated deep hypersaline anoxic basin Discovery. CbbL and cbbM genes were found in both brine and interface of the Discovery Basin but were absent in the overlying seawater. The diversity of both genes in the brine and interface was low, which might caused by the extreme saline conditions in Discovery of approximately 5 M MgCl2. None of the retrieved sequences were closely related to sequences deposited in the GenBank database. A phylogenetic analysis demonstrated that the cbbL sequences were affiliated with a Thiobacillus sp. or with one of the RuBisCO genes from Hydrogenovibrio marinus. The cbbM sequences clustered with thiobacilli or formed a new group with no close relatives. The results implicate that bacteria with the potential for carbon dioxide fixation and chemoautotrophy are present in the Discovery Basin. This is the first report demonstrating that RuBisCO genes are present under hypersaline conditions of 5 M MgCl2.

  16. Comparative studies of pelagic microbial methane oxidation within two anoxic basins of the central Baltic Sea (Gotland Deep and Landsort Deep)

    NASA Astrophysics Data System (ADS)

    Jakobs, G.; Rehder, G.; Jost, G.; Kießlich, K.; Labrenz, M.; Schmale, O.

    2013-07-01

    Pelagic methane oxidation was investigated in dependence on differing environmental conditions within the redox zone of the Gotland Deep (GD) and Landsort Deep (LD), central Baltic Sea. The redox zone of both deeps, which indicates the transition between oxic and anoxic conditions, was characterized by a pronounced methane concentration gradient between the deep water (GD: 1233 nM, LD: 2935 nM) and the surface water (GD and LD < 10 nM), together with a 13C CH4 enrichment (δ13C CH4 deep water: GD -84‰, LD -71‰ ; redox zone: GD -60‰, LD -20‰ ; δ13C CH4 vs. Vienna Pee Dee Belemnite standard), clearly indicating microbial methane consumption in that specific depth interval. Expression analysis of the methane monooxygenase identified one active type I methanotrophic bacterium in both redox zones. In contrast, the turnover of methane within the redox zones showed strong differences between the two basins (GD: max. 0.12 nM d-1 and LD: max. 0.61 nM d-1), with a four times higher turnover rate constant (k) in the LD (GD: 0.0022 d-1, LD: 0.0079 d-1). Vertical mixing rates for both deeps were calculated on the base of the methane concentration profile and the consumption of methane in the redox zone (GD: 2.5 × 10-6 m2 s-1 LD: 1.6 × 10-5 m2 s-1). Our study identified vertical transport of methane from the deep water body towards the redox zone as well as differing hydrographic conditions within the oxic/anoxic transition zone of these deeps as major factors that determine the pelagic methane oxidation.

  17. Diversity and community structure within anoxic sediment from marine salinity meromictic lakes and a coastal meromictic marine basin, Vestfold Hilds, Eastern Antarctica.

    PubMed

    Bowman, J P; Rea, S M; McCammon, S A; McMeekin, T A

    2000-04-01

    16S rDNA clone library analysis was used to examine the biodiversity and community structure within anoxic sediments of several marine-type salinity meromictic lakes and a coastal marine basin located in the Vestfolds Hills area of Eastern Antarctica. From 69 to 130 (555 total) 16S rDNA clones were analysed from each sediment sample, and restriction fragment length polymorphism (RFLP) and sequence analysis grouped the clones into 202 distinct phylotypes (a clone group with sequence similarity of >0.98). A number of phylotypes and phylotype groups predominated in all libraries, with a group of 10 phylotypes (31% of clones) forming a novel deep branch within the low G+C Gram-positive division. Other abundant phylotypes detected in several different clone libraries grouped with Prochlorococcus cyanobacteria, diatom chloroplasts, delta proteobacteria (Desulfosarcina group, Syntrophus and Geobacterl Pelobacter/Desulphuromonas group), order Chlamydiales (Parachlamydiaceae) and Spirochaetales (wall-less Antarctic spirochaetes). Most archaeal clones detected (3.1% of clones) belonged to a highly diverged group of Euryarchaeota clustering with clones previously detected in rice soil, aquifer sediments and hydrothermal vent material. Little similarity existed between the phylotypes detected in this study and other clone libraries based on marine sediment, suggesting that an enormous prokaryotic diversity occurs within marine and marine-derived sediments.

  18. Post-depositional Diagenetic Carbonate Precipitation, Methane Production and Climate- Driven Sedimentary Processes in the Northeastern Pacific Nitinat Fan

    NASA Astrophysics Data System (ADS)

    Knudson, K. P.; Hendy, I. L.

    2008-12-01

    Ocean Drilling Program (ODP) Core 888B (48°10'N, 126°39'W), from the Nitinat Fan, Cascadia Margin is dominated by sediment deposited during glacial conditions and contains unconformities due to both non- deposition and turbidity current erosion. However, this core also displays a unique chemical signature indicative of post-depositional diagenetic CaCO3 precipitation due to CH4 oxidation. Climate history has been reconstructed based on core lithology, δ13C and δ18O of Globigerina bulloides, magnetic susceptibility, coiling ratios of Neogloboquadrina pachyderma, and 14C dates. The δ13C of marine carbonate, usually related to nutrient utilization, cannot account for the extremely negative G. bulloides δ13C at depths 110 mbsf (-6.5‰), 115 mbsf (-3.0‰), and 225 mbsf (-3.5‰). Instead, we posit that these spikes are a post-depositional diagenetic result of CaCO3 precipitation occurring where porewater alkalinity is rapidly changing due to CH4 oxidation. This secondary CaCO3 is strongly depleted in 12C due to the anaerobic oxidation of CH4 mediated by bacteria, which both favor the 12C isotope and consume CH4 with very negative δ13C. Finally, a telling correlation appears to exist between core lithology and CH4 peaks, leading us to conclude that the CH4 peaks and resulting diagenesis are thus a secondary consequence of climate- driven sedimentary processes. The first CH4 peak (93 ppmv; 78-113 mbsf) occurs within a sandy sediment facies containing wood fragments, possibly deposited during an early glacial period (Marine Isotope Stage 4), in which advancing ice carried terrigenous organic matter to the shelf edge. This wood matter then slowly decayed, consuming oxidants to the extent that methanogenesis occurred. The second CH4 peak (6863 ppmv; 185-240 mbsf), also correlated with a coarse sand facies, lacks evidence of terrigenous organic matter and thus may be related to lateral CH4 gas flow through the porous facies. Therefore, by providing coarse-grained and

  19. Molecular analyses of the microbial community composition of an anoxic basin of a municipal wastewater treatment plant reveal a novel lineage of proteobacteria.

    PubMed

    Chouari, Rakia; Le Paslier, Denis; Daegelen, Patrick; Dauga, Catherine; Weissenbach, Jean; Sghir, Abdelghani

    2010-08-01

    bacterial population rRNA within the anoxic basin.

  20. Onset and demise of Cretaceous oceanic anoxic events: The coupling of surface and bottom oceanic processes in two pelagic basins of the western Tethys

    NASA Astrophysics Data System (ADS)

    Gambacorta, G.; Bersezio, R.; Weissert, H.; Erba, E.

    2016-06-01

    The upper Albian-lower Turonian pelagic successions of the Tethys record processes acting during the onset, core, and recovery from perturbed conditions across oceanic anoxic event (OAE) 1d, OAE 2, and the mid-Cenomanian event I (MCE I) relative to intervening intervals. Five sections from Umbria-Marche and Belluno Basins (Italy) were analyzed at high resolution to assess processes in surface and deep waters. Recurrent facies stacking patterns (SP) and their associations record periods of bottom current activity coupled with surface changes in trophic level. Climate changes appear to have been influential on deep circulation dynamics. Under greenhouse conditions, vigorous bottom currents were arguably induced by warm and dense saline deep waters originated on tropical shelves in the Tethys and/or proto-Atlantic Ocean. Tractive facies postdating intermittent anoxia during OAE 1d and in the interval bracketed by MCE I and OAE 2 are indicative of feeble bottom currents, though capable of disrupting stratification and replenish deep water with oxygen. The major warming at the onset of OAE 2 might have enhanced the formation of warm salty waters, possibly producing local hiatuses at the base of the Bonarelli Level and winnowing at the seafloor. Hiatuses detected at the top of the Bonarelli Level possibly resulted from most effective bottom currents during the early Turonian thermal maximum. Times of minimal sediment displacement correlate with cooler climatic conditions and testify a different mechanism of deep water formation, as further suggested by a color change to reddish lithologies of the post-OAE 1d and post-OAE 2 intervals.

  1. Unraveling the onset of Cretaceous Oceanic Anoxic Event 2 in an extended sediment archive from the Tarfaya-Laayoune Basin, Morocco

    NASA Astrophysics Data System (ADS)

    Kuhnt, Wolfgang; Holbourn, Ann E.; Beil, Sebastian; Aquit, Mohamed; Krawczyk, Tim; Flögel, Sascha; Chellai, El Hassane; Jabour, Haddou

    2017-08-01

    We investigated the onset and development of Cretaceous Oceanic Anoxic Event 2 (OAE2) in a newly drilled core (SN°4) from the Tarfaya Basin (southern Morocco), where this interval is unusually expanded. High-resolution (centimeter-scale equivalent to centennial) analysis of bulk organic and carbonate stable isotopes and of carbonate and organic carbon content in combination with XRF scanner derived elemental distribution reveal that the ocean-climate system behaved in a highly dynamic manner prior to and during the onset of OAE2. Correlation with the latest orbital solution indicates that the main carbon isotope shift occurred during an extended minimum in orbital eccentricity ( 400 kyr cycle). Shorter-term fluctuations in carbonate and organic carbon accumulation and in sea level related terrigenous discharge were predominantly driven by variations in orbital obliquity. Negative excursions in organic and carbonate δ13C preceded the global positive δ13C shift marking the onset of OAE2, suggesting injection of isotopically depleted carbon into the atmosphere. The main δ13C increase during the early phase of OAE2 in the late Cenomanian was punctuated by a transient plateau. Maximum organic carbon accumulation occurred during the later part of the main δ13C increase and was associated with climate cooling events, expressed as three consecutive maxima in bulk carbonate δ18O. The extinctions of the thermocline dwelling keeled planktonic foraminifers Rotalipora greenhornensis and Rotalipora cushmani occurred during the first and last of these cooling events and were likely associated with obliquity paced, ocean-wide expansions, and intensifications of the oxygen minimum zone, affecting their habitat space on a global scale.

  2. Methane oxidation in anoxic lake waters

    NASA Astrophysics Data System (ADS)

    Su, Guangyi; Zopfi, Jakob; Niemann, Helge; Lehmann, Moritz

    2017-04-01

    Freshwater habitats such as lakes are important sources of methante (CH4), however, most studies in lacustrine environments so far provided evidence for aerobic methane oxidation only, and little is known about the importance of anaerobic oxidation of CH4 (AOM) in anoxic lake waters. In marine environments, sulfate reduction coupled to AOM by archaea has been recognized as important sinks of CH4. More recently, the discorvery of anaerobic methane oxidizing denitrifying bacteria represents a novel and possible alternative AOM pathway, involving reactive nitrogen species (e.g., nitrate and nitrite) as electron acceptors in the absence of oxygen. We investigate anaerobic methane oxidation in the water column of two hydrochemically contrasting sites in Lake Lugano, Switzerland. The South Basin displays seasonal stratification, the development of a benthic nepheloid layer and anoxia during summer and fall. The North Basin is permanently stratified with anoxic conditions below 115m water depth. Both Basins accumulate seasonally (South Basin) or permanently (North Basin) large amounts of CH4 in the water column below the chemocline, providing ideal conditions for methanotrophic microorganisms. Previous work revealed a high potential for aerobic methane oxidation within the anoxic water column, but no evidence for true AOM. Here, we show depth distribution data of dissolved CH4, methane oxidation rates and nutrients at both sites. In addition, we performed high resolution phylogenetic analyses of microbial community structures and conducted radio-label incubation experiments with concentrated biomass from anoxic waters and potential alternative electron acceptor additions (nitrate, nitrite and sulfate). First results from the unamended experiments revealed maximum activity of methane oxidation below the redoxcline in both basins. While the incubation experiments neither provided clear evidence for NOx- nor sulfate-dependent AOM, the phylogenetic analysis revealed the

  3. Methane oxidation coupled to oxygenic photosynthesis in anoxic waters.

    PubMed

    Milucka, Jana; Kirf, Mathias; Lu, Lu; Krupke, Andreas; Lam, Phyllis; Littmann, Sten; Kuypers, Marcel M M; Schubert, Carsten J

    2015-09-01

    Freshwater lakes represent large methane sources that, in contrast to the Ocean, significantly contribute to non-anthropogenic methane emissions to the atmosphere. Particularly mixed lakes are major methane emitters, while permanently and seasonally stratified lakes with anoxic bottom waters are often characterized by strongly reduced methane emissions. The causes for this reduced methane flux from anoxic lake waters are not fully understood. Here we identified the microorganisms and processes responsible for the near complete consumption of methane in the anoxic waters of a permanently stratified lake, Lago di Cadagno. Interestingly, known anaerobic methanotrophs could not be detected in these waters. Instead, we found abundant gamma-proteobacterial aerobic methane-oxidizing bacteria active in the anoxic waters. In vitro incubations revealed that, among all the tested potential electron acceptors, only the addition of oxygen enhanced the rates of methane oxidation. An equally pronounced stimulation was also observed when the anoxic water samples were incubated in the light. Our combined results from molecular, biogeochemical and single-cell analyses indicate that methane removal at the anoxic chemocline of Lago di Cadagno is due to true aerobic oxidation of methane fuelled by in situ oxygen production by photosynthetic algae. A similar mechanism could be active in seasonally stratified lakes and marine basins such as the Black Sea, where light penetrates to the anoxic chemocline. Given the widespread occurrence of seasonally stratified anoxic lakes, aerobic methane oxidation coupled to oxygenic photosynthesis might have an important but so far neglected role in methane emissions from lakes.

  4. Methane oxidation coupled to oxygenic photosynthesis in anoxic waters

    PubMed Central

    Milucka, Jana; Kirf, Mathias; Lu, Lu; Krupke, Andreas; Lam, Phyllis; Littmann, Sten; Kuypers, Marcel MM; Schubert, Carsten J

    2015-01-01

    Freshwater lakes represent large methane sources that, in contrast to the Ocean, significantly contribute to non-anthropogenic methane emissions to the atmosphere. Particularly mixed lakes are major methane emitters, while permanently and seasonally stratified lakes with anoxic bottom waters are often characterized by strongly reduced methane emissions. The causes for this reduced methane flux from anoxic lake waters are not fully understood. Here we identified the microorganisms and processes responsible for the near complete consumption of methane in the anoxic waters of a permanently stratified lake, Lago di Cadagno. Interestingly, known anaerobic methanotrophs could not be detected in these waters. Instead, we found abundant gamma-proteobacterial aerobic methane-oxidizing bacteria active in the anoxic waters. In vitro incubations revealed that, among all the tested potential electron acceptors, only the addition of oxygen enhanced the rates of methane oxidation. An equally pronounced stimulation was also observed when the anoxic water samples were incubated in the light. Our combined results from molecular, biogeochemical and single-cell analyses indicate that methane removal at the anoxic chemocline of Lago di Cadagno is due to true aerobic oxidation of methane fuelled by in situ oxygen production by photosynthetic algae. A similar mechanism could be active in seasonally stratified lakes and marine basins such as the Black Sea, where light penetrates to the anoxic chemocline. Given the widespread occurrence of seasonally stratified anoxic lakes, aerobic methane oxidation coupled to oxygenic photosynthesis might have an important but so far neglected role in methane emissions from lakes. PMID:25679533

  5. Combining local lithofacies and global geochemical signals to test the acidification hypothesis for the onset of Oceanic Anoxic Event 2 in the U.S. Western Interior Basin

    NASA Astrophysics Data System (ADS)

    Jones, M. M.; Sageman, B. B.; Selby, D. S.; Oakes, R. L.; Bralower, T. J.; Parker, A. L.; Leckie, R. M.; Sepulveda, J.

    2015-12-01

    Strata preserving Oceanic Anoxic Event 2 (OAE2), which span the Cenomanian-Turonian (C/T; Late Cretaceous), exhibit evidence of widespread anoxia, a major perturbation to the global carbon cycle, and increased biotic turnover rates. It has been hypothesized that a major volcanic (LIP) eruption, increased CO2 levels, and significant climate warming triggered the event. Recently, OAE2 has also been cited as a potential example of ocean acidification in Earth history and therefore has potential to offer predictive insights on impacts of increasing modern pCO2 levels. As part of an effort to test this hypothesis, the 131-m Smoky Hollow #1 (SH-1) core was drilled near Big Water, Utah during the summer of 2014. The core recovered an expanded stratigraphic record of OAE2 from the mud-rich western margin of the Western Interior Seaway. A high-resolution stable carbon isotope record from bulk organic carbon (δ13Corg) indicates near-continuous preservation of OAE2 with a sustained +2.5‰ excursion that is over 5 times the thickness of the same excursion at the C/T GSSP in Pueblo, Colorado. Notably, this record is characterized by a 1-m thick carbonate-barren interval at the δ13C excursion's onset. This may indicate an episode of ocean acidification driving suppressed carbonate sedimentation or carbonate dissolution. An alternative interpretation is that variations in carbonate concentrations are unrelated to changes in ocean chemistry and are instead driven by changes in local sedimentation patterns (e.g. transgressive-regressive parasequences). To test these hypotheses, a regional lithostratigraphic correlation to the nearshore Cottonwood Canyon section is constructed to assess whether prograding sandy parasequences may have altered carbonate sedimentation rates at the SH-1 locality. Initial osmium and δ13C chemostratigraphies are also developed to constrain the timing of perturbations in global geochemical cycles at the initiation of OAE2, including the onset of large

  6. Characterization of the Lower Aptian Oceanic Anoxic Event (OAE) 1a in the Eastern Iberian Chain (Maestrat Basin, E Spain) by Means of Ammonite Biostratigraphy

    NASA Astrophysics Data System (ADS)

    Moreno-Bedmar, J. A.; Company, M.; Bover-Arnal, T.; Delanoy, G.; Martinez, R.; Grauges, A.; Salas, R.

    2008-05-01

    Oceanic Anoxic Event 1a (OAE1a) is now generally recognized to correlate with the lower part of the Leupoldina cabri planktonic foraminifer Zone. Unfortunately, the calibration of this zone against the standard ammonite scale has remained uncertain. Our recent high-resolution geochemical study (Carbon-isotope) of Lower Aptian sequences in the Iberian Chain of eastern Spain (Moreno-Bedmar et al., in prep) was used as proxy to further characterize OAE 1a. The sequence provides additional ammonite biostratigraphic data that permit correlation of the ammonite zonation with the isotopic signature of OAE1a. That interval includes specimens we identified with affinity for species of Roloboceras and Megatyloceras in the same beds that contain species of Deshayesites forbesi Casey, and Deshayesites gr. euglyphus/spathi, which are characteristic of the Deshayesites weissi Zone. Our results also indicate that D. deshayesi (d'Orbigny), the nominate taxon which marks the base of the superjacent Zone, first occurs a few meters above the geochemical signature corresponding to OAE 1a. Our isotopic data correlated with the ammonite occurrences are in further agreement with Roloboceras beds in England (Casey, 1961a, b; Casey et al., 1998) that are correlational with the Boreal Deshayesites forbesi Zone, which is coeval with the Mediterranean Deshayesites weissi Zone. Similarly, in the Cassis-La Bédoule area (SE France) the OAE 1a interval also corresponds to the Roloboceras beds, but they have been assigned to the Deshayesites deshayesi biozone (Ropolo et al., 2000; 2006). Here we argue that specimens attributed to D. deshayesi (d'Orbigny) and D. dechyi (Papp) from the Roloboceras levels (Ropolo et al., 2006) can be reinterpreted as belonging to D. forbesi, characteristic species of Deshayesites weissi Zone. Stratigraphic data from Roloboceras beds in le Teil region (Ardech patform, SE France) also reveal the presence of Deshayesites consobrinus (d'Orbigny) and Deshayesites gr

  7. The first metazoa living in permanently anoxic conditions

    PubMed Central

    2010-01-01

    Background Several unicellular organisms (prokaryotes and protozoa) can live under permanently anoxic conditions. Although a few metazoans can survive temporarily in the absence of oxygen, it is believed that multi-cellular organisms cannot spend their entire life cycle without free oxygen. Deep seas include some of the most extreme ecosystems on Earth, such as the deep hypersaline anoxic basins of the Mediterranean Sea. These are permanently anoxic systems inhabited by a huge and partly unexplored microbial biodiversity. Results During the last ten years three oceanographic expeditions were conducted to search for the presence of living fauna in the sediments of the deep anoxic hypersaline L'Atalante basin (Mediterranean Sea). We report here that the sediments of the L'Atalante basin are inhabited by three species of the animal phylum Loricifera (Spinoloricus nov. sp., Rugiloricus nov. sp. and Pliciloricus nov. sp.) new to science. Using radioactive tracers, biochemical analyses, quantitative X-ray microanalysis and infrared spectroscopy, scanning and transmission electron microscopy observations on ultra-sections, we provide evidence that these organisms are metabolically active and show specific adaptations to the extreme conditions of the deep basin, such as the lack of mitochondria, and a large number of hydrogenosome-like organelles, associated with endosymbiotic prokaryotes. Conclusions This is the first evidence of a metazoan life cycle that is spent entirely in permanently anoxic sediments. Our findings allow us also to conclude that these metazoans live under anoxic conditions through an obligate anaerobic metabolism that is similar to that demonstrated so far only for unicellular eukaryotes. The discovery of these life forms opens new perspectives for the study of metazoan life in habitats lacking molecular oxygen. PMID:20370908

  8. Corrigendum to "Basin-scale controls on the molybdenum-isotope composition of seawater during Oceanic Anoxic Event 2 (Late Cretaceous)" [Geochim. Cosmochim. Acta 178 (2016) 291-306

    NASA Astrophysics Data System (ADS)

    Dickson, Alexander J.; Jenkyns, Hugh C.; Porcelli, Donald; van den Boorn, Sander; Idiz, Erdem; Owens, Jeremy D.

    2016-09-01

    A recent molybdenum-isotope estimate of the extent of anoxic and euxinic conditions in the world ocean during Oceanic Anoxic Event 2 (∼94 Ma) concluded by discussing a contrast between the new results with existing estimates of marine euxinia based on sulphur isotopes. This suggested contrast was erroneous; when areal extents of marine anoxia and euxinia are calculated for both isotopic proxies, the agreement is actually striking, and highlights the fact that large areas of the global ocean probably remained well ventilated during this event.

  9. Microbial oceanography of anoxic oxygen minimum zones.

    PubMed

    Ulloa, Osvaldo; Canfield, Donald E; DeLong, Edward F; Letelier, Ricardo M; Stewart, Frank J

    2012-10-02

    Vast expanses of oxygen-deficient and nitrite-rich water define the major oxygen minimum zones (OMZs) of the global ocean. They support diverse microbial communities that influence the nitrogen economy of the oceans, contributing to major losses of fixed nitrogen as dinitrogen (N(2)) and nitrous oxide (N(2)O) gases. Anaerobic microbial processes, including the two pathways of N(2) production, denitrification and anaerobic ammonium oxidation, are oxygen-sensitive, with some occurring only under strictly anoxic conditions. The detection limit of the usual method (Winkler titrations) for measuring dissolved oxygen in seawater, however, is much too high to distinguish low oxygen conditions from true anoxia. However, new analytical technologies are revealing vanishingly low oxygen concentrations in nitrite-rich OMZs, indicating that these OMZs are essentially anoxic marine zones (AMZs). Autonomous monitoring platforms also reveal previously unrecognized episodic intrusions of oxygen into the AMZ core, which could periodically support aerobic metabolisms in a typically anoxic environment. Although nitrogen cycling is considered to dominate the microbial ecology and biogeochemistry of AMZs, recent environmental genomics and geochemical studies show the presence of other relevant processes, particularly those associated with the sulfur and carbon cycles. AMZs correspond to an intermediate state between two "end points" represented by fully oxic systems and fully sulfidic systems. Modern and ancient AMZs and sulfidic basins are chemically and functionally related. Global change is affecting the magnitude of biogeochemical fluxes and ocean chemical inventories, leading to shifts in AMZ chemistry and biology that are likely to continue well into the future.

  10. Microbial oceanography of anoxic oxygen minimum zones

    PubMed Central

    Ulloa, Osvaldo; Canfield, Donald E.; DeLong, Edward F.; Letelier, Ricardo M.; Stewart, Frank J.

    2012-01-01

    Vast expanses of oxygen-deficient and nitrite-rich water define the major oxygen minimum zones (OMZs) of the global ocean. They support diverse microbial communities that influence the nitrogen economy of the oceans, contributing to major losses of fixed nitrogen as dinitrogen (N2) and nitrous oxide (N2O) gases. Anaerobic microbial processes, including the two pathways of N2 production, denitrification and anaerobic ammonium oxidation, are oxygen-sensitive, with some occurring only under strictly anoxic conditions. The detection limit of the usual method (Winkler titrations) for measuring dissolved oxygen in seawater, however, is much too high to distinguish low oxygen conditions from true anoxia. However, new analytical technologies are revealing vanishingly low oxygen concentrations in nitrite-rich OMZs, indicating that these OMZs are essentially anoxic marine zones (AMZs). Autonomous monitoring platforms also reveal previously unrecognized episodic intrusions of oxygen into the AMZ core, which could periodically support aerobic metabolisms in a typically anoxic environment. Although nitrogen cycling is considered to dominate the microbial ecology and biogeochemistry of AMZs, recent environmental genomics and geochemical studies show the presence of other relevant processes, particularly those associated with the sulfur and carbon cycles. AMZs correspond to an intermediate state between two “end points” represented by fully oxic systems and fully sulfidic systems. Modern and ancient AMZs and sulfidic basins are chemically and functionally related. Global change is affecting the magnitude of biogeochemical fluxes and ocean chemical inventories, leading to shifts in AMZ chemistry and biology that are likely to continue well into the future. PMID:22967509

  11. Methane oxidation and methane fluxes in the ocean surface layer and deep anoxic waters

    NASA Technical Reports Server (NTRS)

    Ward, B. B.; Kilpatrick, K. A.; Novelli, P. C.; Scranton, M. I.

    1987-01-01

    Measured biological oxidation rates of methane in near-surface waters of the Cariaco Basin are compared with the diffusional fluxes computed from concentration gradients of methane in the surface layer. Methane fluxes and oxidation rates were investigated in surface waters, at the oxic/anoxic interface, and in deep anoxic waters. It is shown that the surface-waters oxidation of methane is a mechanism which modulates the flux of methane from marine waters to the atmosphere.

  12. The challenge of proving the existence of metazoan life in permanently anoxic deep-sea sediments.

    PubMed

    Danovaro, Roberto; Gambi, Cristina; Dell'Anno, Antonio; Corinaldesi, Cinzia; Pusceddu, Antonio; Neves, Ricardo Cardoso; Kristensen, Reinhardt Møbjerg

    2016-06-07

    The demonstration of the existence of metazoan life in absence of free oxygen is one of the most fascinating and difficult challenges in biology. Danovaro et al. (2010) discovered three new species of the Phylum Loricifera, living in the anoxic sediments of the L'Atalante, a deep-hypersaline anoxic basin of the Mediterranean Sea. Multiple and independent analyses based on staining, incorporation of radiolabeled substrates, CellTracker Green incorporation experiments and ultra-structure analyses, allowed Danovaro et al. (2010) to conclude that these animals were able to spend their entire life cycle under anoxic conditions. Bernhard et al. (2015) investigated the same basin. Due to technical difficulties in sampling operations, they could not collect samples from the permanently anoxic sediment, and sampled only the redoxcline portion of the L'Atalante basin. They found ten individuals of Loricifera and provided alternative interpretations of the results of Danovaro et al. (2010). Here we analyze these interpretations, and present additional evidence indicating that the Loricifera encountered in the anoxic basin L'Atalante were actually alive at the time of sampling. We also discuss the reliability of different methodologies and approaches in providing evidence of metazoans living in anoxic conditions, paving the way for future investigations.This paper is a response to Bernhard JM, Morrison CR, Pape E, Beaudoin DJ, Todaro MA, Pachiadaki MG, Kormas KAr, Edgcomb VG. 2015. Metazoans of redoxcline sediments in Mediterranean deep-sea hypersaline anoxic basins. BMC Biology 2015 13:105.See research article at http://bmcbiol.biomedcentral.com/articles/10.1186/s12915-015-0213-6.

  13. Anoxic monimolimnia: Nutrients devious feeders or bombs ready to explode?

    NASA Astrophysics Data System (ADS)

    Gianni, Areti; Zacharias, Ierotheos

    2015-04-01

    Coastal regions are under strong human influence and its environmental impact is reflected into their water quality. Oligotrophic estuaries and coastal systems have changed in mesotrophic and/or eutrophic, shown an increase in toxic algal blooms, hypoxic/anoxic events, and massive mortalities of many aquatic and benthic organisms. In strongly stratified and productive water basins, bottom water dissolved oxygen is depleted due to the excessive organic matter decomposition in these depths. Distribution and recycling of nutrients in their water column is inextricably dependent on oxygenation and redox conditions. Bottom water anoxia accelerates PO43-, NH4+ and H2S recycling and accumulation from organic matter decomposition. The anoxic, H2S, PO43- and NH4+ rich bottom water constitutes a toxic layer, threatening the balance of the entire ecosystem. In permanently stratified water basins, storm events could result in stratification destruction and water column total mixing. The turnover brings large amounts of H2S to the surface resulting in low levels of oxygen and massive fish kills. PO43- and NH4+ are released to the interface and surface waters promoting algal blooms. Μore organic matter is produced fueling anoxia. The arising question is, whether the balance of an anoxic water ecosystem is under the threat of its hypolimnetic nutrient and sulfide load, only in the case of storm events and water column total mixing. In polymictic water basins it is clear that the accumulated, in the bottom layer, nutrients will supply surface waters, after the pycnocline overturn. Besides this mechanism of basins' water quality degradation is nowadays recognized as one of the biggest obstacles in eutrophic environments management and restoration efforts. The role of internal load, in permanently stratified water basins, is not so clear. In the present study the impact of storm events on water column stability and bottom water anoxia of meromictic coastal basins, is investigated

  14. Biogeochemical consequences of an oxygenated intrusion into an anoxic fjord

    PubMed Central

    2014-01-01

    Background This paper is based on the studies of the biogeochemical structure of the water column in the anoxic Fjord Hunnbunn (south-eastern Norway) performed in 2009, 2011 and 2012. This Fjord is an enclosed basin of brackish water separated by a narrow and shallow outlet to the sea with a permanently anoxic layer. We show how an oxygenated intrusion could lead to both positive and negative effects on the ecosystem state in Hunnbunn due to a change in the biogeochemical structure. Results During the stratified periods in 2009 and 2012 the anoxic layer amounted to approximately 10% of the total water volume in the Fjord, while dissolved oxygen (DO) was present in 80-90% of the water. In the autumn of 2011 the water chemistry structure observed in Fjord Hunnbunn was clearly affected by a recent oxygenated intrusion defined by abnormal salinity patterns. This led to a shift of the DO boundary position to shallower depths, resulting in a thicker anoxic layer comprising approximately 40% of the total water volume, with DO present only in approximately 60% of the water. The oxygenated water intrusions led to a twofold decrease of the concentrations of hydrogen sulphide, ammonia, phosphate and silicate in the deep layers with a simultaneous increase of these nutrients and a decrease of the pH level in the surface layers. The concentrations of manganese, iron, and mercury species changed dramatically and in particular revealed a significant supply of iron and methylmercury to the water column. Conclusions Oxic water intrusions into anoxic fjords could lead not only to the flushing of the bottom anoxia, but to a dispersal of sulphidic and low oxygen conditions to the larger bottom area. The elevation of the hydrogen sulphide to the shallower layers (that can be rapidly oxidized) is accompanied by the appearance in the subsurface water of methylmercury, which is easily accumulated by organisms and can be transported to the surrounding waters, affecting the ecosystem over a

  15. Advancing Knowledge of Anoxic Systems of the World Ocean

    NASA Astrophysics Data System (ADS)

    Neretin, Lev N.; Jørgensen, Bo Barker; Polikarpov, Igor G.

    2004-02-01

    Life on Earth emerged under anaerobic conditions. Many fundamental biochemical and metabolic pathways evolved before the atmosphere contained oxygen. At present, anaerobic (anoxic) conditions in marine milieu are generally restricted to sediments and to basins isolated from oxygenated deep-sea circulation. Enhanced oxygen consumption by organic matter decomposition and slow downward mixing and diffusion of dissolved oxygen from the surface waters can lead to oxygen deficiency in the water column in highly productive waters, forming the Oxygen Minimum Zone (OMZ). Bottom waters of coastal upwelling regions are frequently exposed to anaerobic conditions owing to extremely high primary productivity. In the past, such conditions in the water column may have developed more readily; for example, in the mid-Cretaceous. Oceanic anoxic events (OAE) were episodes of globally enhanced organic carbon burial that have significantly affected global climate by reducing atmospheric CO2.

  16. BASINS

    EPA Pesticide Factsheets

    Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) is a multipurpose environmental analysis system designed to help regional, state, and local agencies perform watershed- and water quality-based studies.

  17. Pyritization of trace metals in anoxic marine sediments

    NASA Astrophysics Data System (ADS)

    Huerta-Diaz, Miguel A.; Morse, John W.

    1992-07-01

    The pyritization of reactive trace elements in different anoxic marine sediments was investigated to determine the importance of factors such as ∑H 2S, reactive-Fe, pyrite content and salinity in controlling this process. The areas studied included anoxic-sulfidic sediments (Baffin Bay, a hypersaline coastal lagoon from Texas and Green Canyon, a hemipelagic oil seepage area), anoxic-nonsulfidic sediments with high sedimentation rates (Atchafalaya Bay-Mississippi Delta system), hemipelagic anoxic-nonsulfidic sediments with low sedimentation rates (Gulf of Mexico shelf and slope and Orca Basin, an euxinic hypersaline basin) and organic-rich marsh sediments (Atchafalaya Bay). Results indicate that the degree of trace metal pyritization (DTMP) of all trace metals, except Cd, increased with increasing degree of pyritization (DOP), irrespective of the type of sedimentary environment involved. However, for As, Hg and Mo, the DTMP/DOP values were generally above the 1:1 ratio line, whereas the transition metals Co, Cu, Mn and Ni displayed a close to linear increase in DTMP with DOP and moderate incorporation into pyrite. Chromium and the class B metals Pb and Zn were also gradually incorporated into the pyrite phase but without reaching the DTMP levels exhibited by the transition metals. Cadmium was not incorporated to a significant extent. These results are consistent with the chemical attributes of these different classes of trace elements. Availability of dissolved trace metals and organic matter content are apparently important factors controlling the incorporation of Co, Cr, Cu and Ni into pyrite in anoxicsulfidic (Fe-poor and H 2S-rich) environments.

  18. Dense bottom gravity currents and their impact on pelagic methanotrophy at oxic/anoxic transition zones

    NASA Astrophysics Data System (ADS)

    Schmale, Oliver; Krause, Srefan; Holtermann, Peter; Power Guerra, Nicole C.; Umlauf, Lars

    2016-04-01

    Interfaces between oxic and anoxic water bodies represent distinct zones in which the activity of specially adapted microbes often controls biogeochemical transformations. Anoxic basins as the Black Sea, the Cariaco Basin, and the Baltic Sea represent ideal locations to examine these processes, the involved microorganisms, and the influence of their metabolism on the turnover of different substances. Taking the Baltic Sea as an example, it is shown here that turbulent mixing of sulfidic and oxic waters may have a strong impact on microbially-mediated transformations. Direct evidence for these processes was derived from observations of methane oxidizing bacteria (MOB), their activity, and turbulence inside a sharp redox interface, freshly generated by a large-scale intrusion of oxic waters into the sulfidic deep layers of the central Baltic Sea (Gotland Basin). Based on detailed turbulence measurements, different mixing regimes along the basin slope were defined in our study to characterize the effect of turbulent mixing on MOB abundances and methanotrophic activities. We found that methane oxidation rates inside the oxic/anoxic transition zone at the shallow entrance of the basin were five times higher compared to the weakly turbulent redoxcline region in the deep interior of the basin. We propose that high mixing rates in the entrance and the close vicinity of two oxic/anoxic transition zones increased the flux of oxygen and methane into the transition zone, and consequently stimulated the growth of the MOB population and their activity. In contrast, low mixing rates in the stagnant interior of the basin reduced the flux of these gases into the transition zone, explaining the relatively small MOB population size and low methane turnover rates observed in the center of the basin.

  19. Increased thermohaline stratification as a possible cause for an ocean anoxic event in the Cretaceous period.

    PubMed

    Erbacher, J; Huber, B T; Norris, R D; Markey, M

    2001-01-18

    Ocean anoxic events were periods of high carbon burial that led to drawdown of atmospheric carbon dioxide, lowering of bottom-water oxygen concentrations and, in many cases, significant biological extinction. Most ocean anoxic events are thought to be caused by high productivity and export of carbon from surface waters which is then preserved in organic-rich sediments, known as black shales. But the factors that triggered some of these events remain uncertain. Here we present stable isotope data from a mid-Cretaceous ocean anoxic event that occurred 112 Myr ago, and that point to increased thermohaline stratification as the probable cause. Ocean anoxic event 1b is associated with an increase in surface-water temperatures and runoff that led to decreased bottom-water formation and elevated carbon burial in the restricted basins of the western Tethys and North Atlantic. This event is in many ways similar to that which led to the more recent Plio-Pleistocene Mediterranean sapropels, but the greater geographical extent and longer duration (approximately 46 kyr) of ocean anoxic event 1b suggest that processes leading to such ocean anoxic events in the North Atlantic and western Tethys were able to act over a much larger region, and sequester far more carbon, than any of the Quaternary sapropels.

  20. Anoxic gas recirculation system for fouling control in anoxic membrane reactor.

    PubMed

    Lee, Hansaem; Lee, Daeju; Hong, Seongwan; Yun, Geum Hee; Kim, Sungpyo; Hwang, Jung Ki; Lee, Woojae; Yun, Zuwhan

    2014-06-01

    Anoxic gas recirculation system was applied to control the membrane fouling in pilot-scale 4-stage anoxic membrane bioreactor (MBR). In the anaerobic-anoxic-anoxic-aerobic flow scheme, hydrophilic polytetrafluoroethylene (PTFE) membrane (0.2 μm, 7.2 m(2)/module) was submerged in the second anoxic zone. During 8 months operation, the average flux of the membrane was 21.3 L/(m(2)·hr). Chemical cleaning of the membrane was conducted only once with sodium hydroxide and sodium hypochlorite. Dissolved oxygen (DO) concentration in the second anoxic zone was maintained with an average of 0.19 ± 0.05 mg/L. Gas chromatography analysis showed that the headspace gas in the second anoxic reactor was mainly consisted of N2 (93.0% ± 2.5%), O2 (3.8% ± 0.6%), and CO2 (3.0% ± 0.5%), where the saturation DO concentration in liquid phase was 1.57 mg/L. Atmospheric O2 content (20.5% ± 0.8%) was significantly reduced in the anoxic gas. The average pH in the reactor was 7.2 ± 0.4. As a result, the recirculation of the anoxic gas was successfully applied to control the membrane fouling in the anoxic MBR. Copyright © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

  1. Valanginian Weissert oceanic anoxic event

    NASA Astrophysics Data System (ADS)

    Erba, Elisabetta; Bartolini, Annachiara; Larson, Roger L.

    2004-02-01

    Biotic changes in nannofossils and radiolarians associated with the Valanginian δ13C anomaly are documented at Ocean Drilling Program Hole 1149B in the Pacific Ocean: they are coeval and similar to those previously documented in the Tethys, suggesting a global perturbation of marine ecosystems. A marked increase in abundance of Diazomatolithus, absence of nannoconids, and a Pantanellium peak characterize the Valanginian δ13C excursion. Such changes are interpreted as being due to global enhanced fertility and a biocalcification crisis under conditions of excess CO2. The occurrence of organic C rich black shales in the Southern Alps and in the Pacific in the interval corresponding to the δ13C excursion suggests a Valanginian oceanic anoxic event (OAE). Volcanism of the Paranà-Etendeka large igneous province (ca. 132 Ma) was presumably responsible for an increase of CO2, triggering a climate change and accelerated hydrological cycling, possibly causing an indirect fertilization of the oceans. Widespread nutrification via introduction of biolimiting metals at spreading ridges could have significantly increased during the Gondwana breakup and simultaneous tectonic events in three separate oceans. There is no paleontological or δ18O evidence of warming during the Valanginian OAE. On the contrary, both nannofossils and oxygen isotopes record a cooling event at the climax of the δ13C excursion. Weathering of basalts and burial of organic C rich black shales were presumably responsible for CO2 drawdown and establishment of reversed greenhouse conditions.

  2. Carbon sequestration in an expanded lake system during the Toarcian oceanic anoxic event

    NASA Astrophysics Data System (ADS)

    Xu, Weimu; Ruhl, Micha; Jenkyns, Hugh C.; Hesselbo, Stephen P.; Riding, James B.; Selby, David; Naafs, B. David A.; Weijers, Johan W. H.; Pancost, Richard D.; Tegelaar, Erik W.; Idiz, Erdem F.

    2017-01-01

    The Early Jurassic Toarcian oceanic anoxic event (~183 Ma) was marked by marine anoxia-euxinia and globally significant organic-matter burial, accompanied by a major global carbon-cycle perturbation probably linked to Karoo-Ferrar volcanism. Although the Toarcian oceanic anoxic event is well studied in the marine realm, accompanying climatic and environmental change on the continents is poorly understood. Here, utilizing radioisotopic, palynological and geochemical data from lacustrine black shales, we demonstrate that a large lake system developed contemporaneously with the Toarcian oceanic anoxic event in the Sichuan Basin, China, probably due to enhanced hydrological cycling under elevated atmospheric pCO 2. We attribute increased lacustrine organic productivity to elevated fluvial nutrient supply, which resulted in the burial of ~460 Gt of organic carbon in the Sichuan Basin alone, creating an important negative feedback in the global exogenic carbon cycle. We suggest that enhanced nutrient delivery to marine and large lacustrine systems was a key component in the global carbon cycle recovery during the Toarcian oceanic anoxic event and acted to shorten the duration of the recovery of global δ13C values.

  3. Apparent removal of the transient tracer carbon tetrachloride from anoxic seawater

    SciTech Connect

    Krysell, M.; Fogelqvist, E.; Tanhua, T. |

    1994-11-01

    Two chlorofluorocarbons (CFC-11 and carbon tetrachloride, CCl4) widely used as tracers for dating water masses, were measured in the Gotland Basin of the Baltic Sea. At the time of the survey, the bottom water of the basin had remained stagnant for 15 years and anoxic for about the same period of time, and the concentrations of both CFC-11 and CCl4 decrease dramatically with depth below the mixed layer. Furthermore, the ratio of CFC-11 to CCl4 increases with depth under the mixed layer along with a steep decrease in oxygen concentration. This is contrary to what would be expected from the atmospheric histories. The most plausible explanation for this is that there is a mechanism whereby the CCl4 is removed from the water mass under anoxic and suboxide conditions.

  4. Oceanic Anoxic Events: 30 Years on

    NASA Astrophysics Data System (ADS)

    Jenkyns, H. C.

    2006-12-01

    1. Oceanic Anoxic Events are regional black-shale events Of course they are - because that is the nature of the definition! The recognition of Cretaceous Oceanic Anoxic Events in 1976 stemmed from the finding, by the Deep Sea Drilling Project, of black organic-rich shales from the Pacific and Atlantic Oceans that were of equal age to similar facies exposed in northern and southern Europe and recognized as early as 1891. However, when calibrated against high-resolution carbon-isotope curves, based on carbonate and organic matter, the most organic-rich and/or carbonate-poor sediments can be slightly diachronous, as a result of local depositional and diagenetic conditions. For this reason, the onset and the termination of an Oceanic Anoxic Event may be less ambiguously defined using characteristic peaks and inflections in the associated carbon- isotope curve. As well as the two major Cretaceous Oceanic Anoxic Events (early Aptian Selli Event; Cenomanian Turonian Bonarelli Event) that were clearly global in their effect, other events that apparently left a spatially more limited record include: Valanginian Weissert Event, Hauterivian Faraoni Event, Early Albian Paquier Event, Late Albian Breistroffer Event and a possible Santonian Coniacian Event. These events produced significant black-shale deposits primarily in the Atlantic Tethyan region. The only Jurassic OAE recognized to date is that of the early Toarcian. 2. Oceanic Anoxic Events were characterized by the widespread distribution of anoxic watermasses Indeed they were! The presence of delicate millimetre-scale laminations in the black shales deposited during Oceanic Anoxic Events implies a lack of bottom-dwelling fauna, generally attributed to anoxia. Furthermore, the presence, in Toarcian, Aptian and Cenomanian Turonian black shales, of molecular fossils derived from green sulphur bacteria, indicates that free hydrogen sulphide existed in the relatively shallow illuminated levels of the ocean during OAEs. An

  5. Photochemical synthesis of biomolecules under anoxic conditions

    NASA Technical Reports Server (NTRS)

    Folsome, C.; Brittain, A.; Zelko, M.

    1983-01-01

    The long-wavelength UV anoxic photosynthesis of uracil, various sugars (including deoxyribose and glycoaldehyde), amino acids, and other organic photoproducts is reported. The reactions were conducted in a mixture of water, calcium carbonate, hydrazine, and formaldehyde which were subjected to 24 hr or 72 hr radiation. Product yields were greatest when the hydrazine/formaldehyde ratio was one, and when the reactant concentrations were low. These data suggest that organic products can be formed in variety from those amounts of formaldehyde and hydazine precursors which are themselves formed under anoxic UV photochemical conditions.

  6. Photochemical synthesis of biomolecules under anoxic conditions

    NASA Technical Reports Server (NTRS)

    Folsome, C.; Brittain, A.; Zelko, M.

    1983-01-01

    The long-wavelength UV anoxic photosynthesis of uracil, various sugars (including deoxyribose and glycoaldehyde), amino acids, and other organic photoproducts is reported. The reactions were conducted in a mixture of water, calcium carbonate, hydrazine, and formaldehyde which were subjected to 24 hr or 72 hr radiation. Product yields were greatest when the hydrazine/formaldehyde ratio was one, and when the reactant concentrations were low. These data suggest that organic products can be formed in variety from those amounts of formaldehyde and hydazine precursors which are themselves formed under anoxic UV photochemical conditions.

  7. Gradual and sustained carbon dioxide release during Aptian Oceanic Anoxic Event 1a

    NASA Astrophysics Data System (ADS)

    Naafs, B. D. A.; Castro, J. M.; de Gea, G. A.; Quijano, M. L.; Schmidt, D. N.; Pancost, R. D.

    2016-02-01

    During the Aptian Oceanic Anoxic Event 1a, about 120 million years ago, black shales were deposited in all the main ocean basins. The event was also associated with elevated sea surface temperatures and a calcification crisis in calcareous nannoplankton. These environmental changes have been attributed to variations in atmospheric CO2 concentrations, but the evolution of the carbon cycle during this event is poorly constrained. Here we present records of atmospheric CO2 concentrations across Oceanic Anoxic Event 1a derived from bulk and compound-specific δ13C from marine rock outcrops in southern Spain and Tunisia. We find that CO2 concentrations doubled in two steps during the oceanic anoxic event and remained above background values for approximately 1.5-2 million years before declining. The rise of CO2 concentrations occurred over several tens to hundreds of thousand years, and thus was unlikely to have resulted in any prolonged surface ocean acidification, suggesting that CO2 emissions were not the primary cause of the nannoplankton calcification crisis. We find that the period of elevated CO2 concentrations coincides with a shift in the oceanic osmium-isotope inventory associated with emplacement of the Ontong Java Plateau flood basalts, and conclude that sustained volcanic outgassing was the primary source of carbon dioxide during Oceanic Anoxic Event 1a.

  8. Arctic Ocean circulation during the anoxic Eocene Azolla event

    NASA Astrophysics Data System (ADS)

    Speelman, Eveline; Sinninghe Damsté, Jaap; März, Christian; Brumsack, Hans; Reichart, Gert-Jan

    2010-05-01

    The Azolla interval, as encountered in Eocene sediments from the Arctic Ocean, is characterized by organic rich sediments ( 4wt% Corg). In general, high levels of organic matter may be caused by increased productivity, i.e. extensive growth of Azolla, and/or enhanced preservation of organic matter, or a combination of both. Anoxic (bottom) water conditions, expanded oxygen minimum zones, or increased sedimentation rates all potentially increase organic matter preservation. According to plate tectonic, bathymetric, and paleogeographic reconstructions, the Arctic Ocean was a virtually isolated shallow basin, with one possible deeper connection to the Nordic Seas represented by a still shallow Fram Strait (Jakobsson et al., 2007), hampering ventilation of the Arctic Basin. During the Azolla interval surface waters freshened, while at the same time bottom waters appear to have remained saline, indicating that the Arctic was highly stratified. The restricted ventilation and stratification in concert with ongoing export of organic matter most likely resulted in the development of anoxic conditions in the lower part of the water column. Whereas the excess precipitation over evaporation maintained the freshwater lid, sustained input of Nordic Sea water is needed to keep the deeper waters saline. To which degree the Arctic Ocean exchanged with the Nordic Seas is, however, still largely unknown. Here we present a high-resolution trace metal record (ICP-MS and ICP-OES) for the expanded Early/Middle Eocene section capturing the Azolla interval from Integrated Ocean Drilling Program (IODP) Expedition 302 (ACEX) drilled on the Lomonosov Ridge, central Arctic Ocean. Euxinic conditions throughout the interval resulted in the efficient removal of redox sensitive trace metals from the water column. Using the sedimentary trace metal record we also constrained circulation in the Arctic Ocean by assessing the relative importance of trace metal input sources (i.e. fluvial, eolian, and

  9. Will hypolimnetic waters become anoxic in all deep tropical lakes?

    NASA Astrophysics Data System (ADS)

    Fukushima, Takehiko; Matsushita, Bunkei; Subehi, Luki; Setiawan, Fajar; Wibowo, Hendro

    2017-03-01

    To elucidate trends of hypolimnetic oxygen concentrations, vertical distributions of dissolved oxygen were measured in eight deep tropical bodies of water (one natural lake with two basins, five natural lakes, and one reservoir) in Indonesia. A comparison of those concentrations with previously reported data revealed that shoaling of hypolimnetic oxygen-deficient (around a few decimeters to a few meter per year) water had occurred in all of the lakes. Calculated areal hypolimnetic oxygen depletion rates were 0.046-5.9 g m-2 y-1. The oligomictic or meromictic characteristics of the bodies of water suppressed circulation and mixing in the hypolimnions and thus resulted in continuous shoaling of the uppermost oxygen-deficient layers. In some lakes, millions of fish sometimes died suddenly, probably owing to upward movement of oxygen-deficient water to near the surface during periods of strong winds. In the future, the rate of shoaling will be accelerated by human impacts in the basins and by climate warming, the influence of which has already been manifested by rising water temperatures in these lakes. Appropriate monitoring and discussions of future restoration challenges are urgently needed to prevent the hypolimnions of the lakes from becoming completely anoxic.

  10. Will hypolimnetic waters become anoxic in all deep tropical lakes?

    PubMed Central

    Fukushima, Takehiko; Matsushita, Bunkei; Subehi, Luki; Setiawan, Fajar; Wibowo, Hendro

    2017-01-01

    To elucidate trends of hypolimnetic oxygen concentrations, vertical distributions of dissolved oxygen were measured in eight deep tropical bodies of water (one natural lake with two basins, five natural lakes, and one reservoir) in Indonesia. A comparison of those concentrations with previously reported data revealed that shoaling of hypolimnetic oxygen-deficient (around a few decimeters to a few meter per year) water had occurred in all of the lakes. Calculated areal hypolimnetic oxygen depletion rates were 0.046–5.9 g m−2 y−1. The oligomictic or meromictic characteristics of the bodies of water suppressed circulation and mixing in the hypolimnions and thus resulted in continuous shoaling of the uppermost oxygen-deficient layers. In some lakes, millions of fish sometimes died suddenly, probably owing to upward movement of oxygen-deficient water to near the surface during periods of strong winds. In the future, the rate of shoaling will be accelerated by human impacts in the basins and by climate warming, the influence of which has already been manifested by rising water temperatures in these lakes. Appropriate monitoring and discussions of future restoration challenges are urgently needed to prevent the hypolimnions of the lakes from becoming completely anoxic.

  11. Sea-floor drainage features of Cascadia Basin and the adjacent continental slope, northeast Pacific Ocean

    USGS Publications Warehouse

    Hampton, M.A.; Karl, Herman A.; Kenyon, Neil H.

    1989-01-01

    Sea-floor drainage features of Cascadia Basin and the adjacent continental slope include canyons, primary fan valleys, deep-sea valleys, and remnant valley segments. Long-range sidescan sonographs and associated seismic-reflection profiles indicate that the canyons may originate along a mid-slope escarpment and grow upslope by mass wasting and downslope by valley erosion or aggradation. Most canyons are partly filled with sediment, and Quillayute Canyon is almost completely filled. Under normal growth conditions, the larger canyons connect with primary fan valleys or deep-sea valleys in Cascadia Basin, but development of accretionary ridges blocks or re-routes most canyons, forcing abandonment of the associated valleys in the basin. Astoria Fan has a primary fan valley that connects with Astoria Canyon at the fan apex. The fan valley is bordered by parallel levees on the upper fan but becomes obscure on the lower fan, where a few valley segments appear on the sonographs. Apparently, Nitinat Fan does not presently have a primary fan valley; none of the numerous valleys on the fan connect with a canyon. The Willapa-Cascadia-Vancouver-Juan de Fuca deep-sea valley system bypasses the submarine fans and includes deeply incised valleys to broad shallow swales, as well as within-valley terraces and hanging-valley confluences. ?? 1989.

  12. Oxic and Anoxic Regions of Subseafloor Sediment

    NASA Astrophysics Data System (ADS)

    D'Hondt, S.; Pockalny, R. A.; Spivack, A. J.; Inagaki, F.; Murray, R. W.; Adhikari, R. R.; Gribsholt, B.; Kallmeyer, J.; McKinley, C. C.; Morono, Y.; Røy, H.; Sauvage, J.; Ziebis, W.

    2015-12-01

    Dissolved oxygen content defines two broad categories of subseafloor sediment. In areas with high rates of microbial respiration, most of the sediment column is anoxic and active anaerobic microbial communities are present for hundreds of meters or more below the seafloor. In these regions, O2 and aerobic communities penetrate only millimeters to centimeters into the sediment from the sediment-water interface. In some areas of active fluid flow through the underlying basalt, O2 may also penetrate meters upward into the sediment from the basalt. In areas with low sedimentary respiration, O2 and aerobic communities penetrate tens of meters downward from the seafloor and may persist throughout the entire sediment column. IODP Expedition 329 showed that microbial cells and aerobic respiration persist through the entire sediment sequence (to depths of at least 75 meters below seafloor) in the South Pacific Gyre. Extrapolating from these results and a global relationship of O2 penetration depth to sedimentation rate and sediment thickness, we suggest that oxygen and aerobic communities occur throughout the entire sediment sequence in 15-44% of the Pacific and 9-37% of the global seafloor. Subduction of sediment from largely anoxic regions and subduction of sediment and basalt from fully oxic regions are respectively sources of reduced and oxidized material to the mantle. The balance between oxic and anoxic regions has presumably changed considerably throughout Earth history. Regions with largely anoxic sediment and regions with fully oxic sediment present fundamentally different opportunities for understanding of (i) paleoceanographic history and (ii) the nature of microbial life under extreme energy limitations.

  13. Impact of Cretaceous sea level rise and anoxic events on the Mesozoic carbonate platform of Yugoslavia

    SciTech Connect

    Jenkyns, H.C. )

    1991-06-01

    The Adriatic/Dinaric carbonate platform of Yugoslavia was influenced by rapid sea level rise and an oceanic anoxic event during the Cenomanian-Turonian. Open-marine biota such as planktonic foraminifera, radiolarians, and locally even ammonites, associated with and bracketed by successions of typical shallow-water carbonates, indicate partial drowning of substantial areas of the platform during this time, suggestive furthermore that the rate of increase of water depth was locally great enough to outpace carbonate production. The presence of carbon-rich and fish-bearing platy limestones, commonly cherty, as an associated coeval facies indicates the development of anoxic or euxinic environments, and the stromatolitic laminations in such rocks are attributed to the action of bacterial mats. It is suggested that an extensive column of deoxygenated water developed in the neighboring Marche-Umbrian-Adriatic deep-water basin and was carried on to the carbonate platform during the Cenomanian-Turonian transgression.

  14. Enhancement of dimethylsulfide production by anoxic stress in natural seawater

    NASA Astrophysics Data System (ADS)

    Omori, Yuko; Tanimoto, Hiroshi; Inomata, Satoshi; Wada, Shigeki; Thume, Kathleen; Pohnert, Georg

    2015-05-01

    Dimethylsulfide (DMS) is produced by phytoplankton in the ocean and plays an important role in biogeochemical cycles and climate system of the Earth. Previous field studies reported a possible relationship between DMS enhancement and anoxic condition, although the governing processes are still to be identified. Here we show the first direct evidence for the enhancement of DMS production by natural planktonic assemblages caused by anoxic stress. Under the anoxic condition, DMS production was considerably enhanced and DMS bacterial consumption was inhibited, resulting in an eightfold higher rate of gross DMS production than that under the oxic condition. Our results demonstrated that anoxic stress is one of important "environmental factors" in the marine DMS dynamics, suggesting the possible global importance due to ubiquity of anoxic conditions in the coastal oceans. This process would become more important in the future due to expansion of coastal hypoxic and anoxic zones by global warming.

  15. Are iron-phosphate minerals a sink for phosphorus in anoxic Black Sea sediments?

    PubMed

    Dijkstra, Nikki; Kraal, Peter; Kuypers, Marcel M M; Schnetger, Bernhard; Slomp, Caroline P

    2014-01-01

    Phosphorus (P) is a key nutrient for marine organisms. The only long-term removal pathway for P in the marine realm is burial in sediments. Iron (Fe) bound P accounts for a significant proportion of this burial at the global scale. In sediments underlying anoxic bottom waters, burial of Fe-bound P is generally assumed to be negligible because of reductive dissolution of Fe(III) (oxyhydr)oxides and release of the associated P. However, recent work suggests that Fe-bound P is an important burial phase in euxinic (i.e. anoxic and sulfidic) basin sediments in the Baltic Sea. In this study, we investigate the role of Fe-bound P as a potential sink for P in Black Sea sediments overlain by oxic and euxinic bottom waters. Sequential P extractions performed on sediments from six multicores along two shelf-to-basin transects provide evidence for the burial of Fe-bound P at all sites, including those in the euxinic deep basin. In the latter sediments, Fe-bound P accounts for more than 20% of the total sedimentary P pool. We suggest that this P is present in the form of reduced Fe-P minerals. We hypothesize that these minerals may be formed as inclusions in sulfur-disproportionating Deltaproteobacteria. Further research is required to elucidate the exact mineral form and formation mechanism of this P burial phase, as well as its role as a sink for P in sulfide-rich marine sediments.

  16. Are Iron-Phosphate Minerals a Sink for Phosphorus in Anoxic Black Sea Sediments?

    PubMed Central

    Dijkstra, Nikki; Kraal, Peter; Kuypers, Marcel M. M.; Schnetger, Bernhard; Slomp, Caroline P.

    2014-01-01

    Phosphorus (P) is a key nutrient for marine organisms. The only long-term removal pathway for P in the marine realm is burial in sediments. Iron (Fe) bound P accounts for a significant proportion of this burial at the global scale. In sediments underlying anoxic bottom waters, burial of Fe-bound P is generally assumed to be negligible because of reductive dissolution of Fe(III) (oxyhydr)oxides and release of the associated P. However, recent work suggests that Fe-bound P is an important burial phase in euxinic (i.e. anoxic and sulfidic) basin sediments in the Baltic Sea. In this study, we investigate the role of Fe-bound P as a potential sink for P in Black Sea sediments overlain by oxic and euxinic bottom waters. Sequential P extractions performed on sediments from six multicores along two shelf-to-basin transects provide evidence for the burial of Fe-bound P at all sites, including those in the euxinic deep basin. In the latter sediments, Fe-bound P accounts for more than 20% of the total sedimentary P pool. We suggest that this P is present in the form of reduced Fe-P minerals. We hypothesize that these minerals may be formed as inclusions in sulfur-disproportionating Deltaproteobacteria. Further research is required to elucidate the exact mineral form and formation mechanism of this P burial phase, as well as its role as a sink for P in sulfide-rich marine sediments. PMID:24988389

  17. MERCURY RELEASE FROM DISTURBED ANOXIC SOILS

    SciTech Connect

    Jaroslav Solc; Bethany A. Bolles

    2001-07-16

    The primary objectives of experiments conducted at the Energy & Environmental Research Center (EERC) were to provide information on the secondary release of mercury from contaminated anoxic sediments to an aqueous environment after disturbance/change of in situ physical conditions and to evaluate its migration and partitioning under controlled conditions, including implications of these processes for treatment of contaminated soils. Experimental work included (1) characterization of the mercury-contaminated sediment; (2) field bench-scale dredging simulation; (3) laboratory column study to evaluate a longer-term response to sediment disturbance; (4) mercury volatilization from sediment during controlled drying; (5) resaturation experiments to evaluate the potential for secondary release of residual mercury after disturbance, transport, drying, and resaturation, which simulate a typical scenario during soil excavation and transport to waste disposal facilities; and (6) mercury speciation and potential for methylation during column incubation experiments.

  18. Contrasting `Oceanic Anoxic Events' in Earth's History

    NASA Astrophysics Data System (ADS)

    Clarkson, M. O.; Stirling, C. H.; Jenkyns, H. C.; Cooke, I. R.; Dickson, A.; Porcelli, D.; Pogge von Strandmann, P.

    2016-12-01

    Oxygen is fundamental to the evolution of life and a lack of oxygen in marine environments is often cited as a causal mechanism for mass extinctions. Anoxia was likely a main contributor to the Permo-Triassic extinction and also important for causing the delayed and complex recovery that took place during the Early Triassic. Despite strong evidence for anoxia, at various places, times and water depths, the extended Permo-to-Early Triassic interval was exceptionally complex and multiple environmental pressures occurred simultaneously. Each kill-mechanism holds a unique position in the carbon cycle and yet they are all inter-related. For example, oceanic anoxia is intimately linked to changes in weathering and nutrient availability, biological productivity and temperature increases. It also represents one of many powerful mechanisms that can help stabilize the global climate, where carbon burial under anoxic conditions can drive dramatic cooling. Here we examine the details of anoxia development for the Permo-Triassic extinction and Early Triassic recovery period, calling upon comparisons to the well-studied Mesozoic Oceanic Anoxic Events (OAEs). The OAEs represent discrete intervals of anoxia that may offer a framework for understanding oxygenation around the Permo-Triassic. In particular, we question whether the Early Triassic represents a series of separate carbon-cycle perturbations, like the OAEs, or a complex internal response to extreme environmental change. We present independent evidence for the global extent of anoxia during OAE2, using 238U/235U (δ238U). These data are placed into the wider carbon-cycle context in order to unravel the driving mechanisms and potential feedback responses of anoxia development. This conceptual OAE model will then be applied to the complexities of the extended Permo-Triassic interval to examine the details of carbon cycle behaviour.

  19. The key features of the bottom sediment composition in the anoxic Lake Mogil'noe

    NASA Astrophysics Data System (ADS)

    Emel'Yanov, E. M.; Kravtsov, V. A.; Tarasov, G. A.

    2010-06-01

    In the summer 2006, integrated geological, geochemical, hydrological, and hydrochemical studies were performed on the relict anoxic Lake Mogil’noe (down to 16 m depths) located on Kil’din Island in the Barents Sea. The chemical and grain-size composition of the bottom sediments were compared for the lake (a permanently anoxic basin) and the Baltic Sea Deeps (periodically anoxic basins). The vertical location of the hydrogen sulfide layer boundary in the lake (9-11 m depths) was practically the same from 1974 up to now. The concentrations of suspended particulate matter in the lake in June and July 2006 appeared to be close to its summer concentrations in the seawaters of the open part of the Baltic Sea. The mud from Lake Mogil’noe compared to those of the Baltic Sea Deeps are characterized by fluid and flake consistency and by pronounced admixtures of sandy and silty fractions probably of eolic origin. The lacustrine mud contain much plant remains; iron sulfides and vivanite were also found in ooze. The concentrations of 22 elements determined in the lacustrine bottom sediments were of the same levels as those found here 33 years ago. The concentrations also appeared to be close to those in the corresponding grain-size types of the bottom sediments in the Baltic Sea. The low Corg/N value (5% on average) in the mud of Mogil’noe Lake compared to the values for the mud of the Baltic Sea Deeps (10% on average) points to the considerable planktogenic component in the organic matter composition of the lacustrine mud. No indications were reveled for anthropogenic contaminations of the lacustrine bottom sediments with toxic metals.

  20. Investigating phosphorus uptake in anoxic and sulfidic surface sediments with 33P radiotracer experiments

    NASA Astrophysics Data System (ADS)

    Dijkstra, Nikki; Kraal, Peter; Gonzalez, Santiago; Slomp, Caroline

    2016-04-01

    Phosphorus (P) is a key nutrient for marine organisms. Enhanced P availability in the water column can fuel algal blooms and the development of bottom water anoxia. Recently, it was suggested that micro-organisms in sediments overlain by anoxic and sulfidic bottom waters might take up dissolved P and form Fe(II)-P minerals, thereby enhancing P removal. In this study, we investigated the uptake of P in surface sediments with 33P radiotracer experiments. The sediments were recovered from the anoxic and sulfidic deep basin of the Black Sea and, for comparison, from the adjacent oxic shelf. Results suggest a very fast sedimentary uptake of 33P at all sites but in particular for sediments from the oxic shelf. At all sites, most 33P was sequestered in the citrate-dithionite-bicarbonate-(CDB)-extractable sediment P fraction. No significant differences with abiotic controls were observed, implying that micro-organisms were not directly involved in the P uptake. Whereas 33P uptake by the oxic shelf sediment was likely controlled by sorption of 33P to iron(Fe)-(oxyhydr)oxides, the nature of the CDB-extractable P fraction in the deep basin sediments remains unclear. We discuss whether authigenic formation of Fe(II)-P minerals or fast adsorption of P to calcites may explain our findings.

  1. Sludge minimization using aerobic/anoxic treatment technology

    SciTech Connect

    Mines, R.O. Jr.; Kalch, R.S.

    1999-07-01

    The objective of this investigation was to demonstrate through a bench-scale study that using an aerobic/anoxic sequence to treat wastewater and biosolids could significantly reduce the production of biosolids (sludge). A bench-scale activated sludge reactor and anoxic digester were operated for approximately three months. The process train consisted of a completely-mixed aerobic reactor with wasting of biosolids to an anoxic digester for stabilization. The system was operated such that biomass produced in the aerobic activated sludge process was wasted to the anoxic digester; and biomass produced in the anoxic digester was wasted back to the activated sludge process. A synthetic wastewater consisting of bacto-peptone nutrient broth was fed to the liquid process train. Influent and effluent to the aerobic biological process train were analytically tested, as were the contents of mixed liquor in the aerobic reactor and anoxic digester. Overall removal efficiencies for the activated sludge process with regard to COD, TKN, NH{sub 3}-N, and alkalinity averaged 91, 89, 98, and 38%, respectively. The overall average sludge production for the aerobic/anoxic process was 24% less than the overall average sludge production from a conventional activated sludge bench-scale system fed the same substrate and operated under similar mean cell residence times.

  2. Deciphering the evolution of Oceanic Anoxic Event 2 (OAE2)

    NASA Astrophysics Data System (ADS)

    Li, Y. X.; Ma, L.

    2015-12-01

    Oceanic anoxic event 2 (OAE2), which occurred at the Cenomanian/Turonian Boundary (CTB, ~93.9 Ma), is characterized by enhanced burial of organic matter in ocean basins that was accompanied by a pronounced positive carbon isotope excursion (CIE) in both marine and terrestrial realms, thus representing a major perturbation to global carbon cycle. Although OAE2 is increasingly recognized, its detailed evolution including initiation, maintenance, and termination remains poorly understood. To unravel the evolution of OAE2, we have carried out a high-resolution magnetic and carbon isotope investigation of an expanded Cenomanian-Turonian boundary section at Tingri in southern Tibet, China. The studied section consists of a hemipelagic succession that was accumulated on the northern margin of India plate in eastern Tethys. Close-spacing sampling every 10 to 20 cm was conducted on the 76 m thick section. Magnetic susceptibility (MS) data of the samples display cyclic variations and spectral analysis of the MS data reveals dominant sedimentary cycles with cycle wavelength ratios similar to those of short eccentricity and precession. Thus, sedimentary cycles representing short eccentricity were used to establish an orbital timescale for the studied section. High-resolution carbon isotope data show a brief negative excursion preceding a relatiely prolonged positive CIE. Also, the new high-resolution carbon isotope data show that each stage of the positive CIE is not monotonic but contains stepwise, short-lived shifts, suggesting that carbon isotope variations were highly dynamic during OAE2. With the new orbital timescale, the OAE2 interval in the Tibetan section is estimated to last for ~870 kyr, which is in striking similarity to the duration estimate of 847 to 885 kyr from the CTB stratotype section. Correlation of our new high-resolution data with other OAE2 records permits detailed examination of the evolution OAE2, especially for unravelling the complicated feedbacks

  3. Origin of first cells at terrestrial, anoxic geothermal fields.

    PubMed

    Mulkidjanian, Armen Y; Bychkov, Andrew Yu; Dibrova, Daria V; Galperin, Michael Y; Koonin, Eugene V

    2012-04-03

    All cells contain much more potassium, phosphate, and transition metals than modern (or reconstructed primeval) oceans, lakes, or rivers. Cells maintain ion gradients by using sophisticated, energy-dependent membrane enzymes (membrane pumps) that are embedded in elaborate ion-tight membranes. The first cells could possess neither ion-tight membranes nor membrane pumps, so the concentrations of small inorganic molecules and ions within protocells and in their environment would equilibrate. Hence, the ion composition of modern cells might reflect the inorganic ion composition of the habitats of protocells. We attempted to reconstruct the "hatcheries" of the first cells by combining geochemical analysis with phylogenomic scrutiny of the inorganic ion requirements of universal components of modern cells. These ubiquitous, and by inference primordial, proteins and functional systems show affinity to and functional requirement for K(+), Zn(2+), Mn(2+), and phosphate. Thus, protocells must have evolved in habitats with a high K(+)/Na(+) ratio and relatively high concentrations of Zn, Mn, and phosphorous compounds. Geochemical reconstruction shows that the ionic composition conducive to the origin of cells could not have existed in marine settings but is compatible with emissions of vapor-dominated zones of inland geothermal systems. Under the anoxic, CO(2)-dominated primordial atmosphere, the chemistry of basins at geothermal fields would resemble the internal milieu of modern cells. The precellular stages of evolution might have transpired in shallow ponds of condensed and cooled geothermal vapor that were lined with porous silicate minerals mixed with metal sulfides and enriched in K(+), Zn(2+), and phosphorous compounds.

  4. Microbially mediated barite dissolution in anoxic brines

    USGS Publications Warehouse

    Ouyang, Bingjie; Akob, Denise M.; Dunlap, Darren S.; Renock, Devon

    2017-01-01

    Fluids injected into shale formations during hydraulic fracturing of black shale return with extraordinarily high total-dissolved-solids (TDS) and high concentrations of barium (Ba) and radium (Ra). Barite, BaSO4, has been implicated as a possible source of Ba as well as a problematic mineral scale that forms on internal well surfaces, often in close association with radiobarite, (Ba,Ra)SO4. The dissolution of barite by abiotic processes is well quantified. However, the identification of microbial communities in flowback and produced water necessitates the need to understand barite dissolution in the presence of bacteria. Therefore, we evaluated the rates and mechanisms of abiotic and microbially-mediated barite dissolution under anoxic and hypersaline conditions in the laboratory. Barite dissolution experiments were conducted with bacterial enrichment cultures established from produced water from Marcellus Shale wells located in northcentral Pennsylvania. These cultures were dominated by anaerobic halophilic bacteria from the genus Halanaerobium. Dissolved Ba was determined by ICP-OES and barite surfaces were investigated by SEM and AFM. Our results reveal that: 1) higher amounts of barium (up to ∼5 × ) are released from barite in the presence of Halanaerobium cultures compared to brine controls after 30 days of reaction, 2) etch pits that develop on the barite (001) surface in the presence of Halanaerobium exhibit a morphology that is distinct from those that form during control experiments without bacteria, 3) etch pits that develop in the presence of Halanaerobium exhibit a morphology that is similar to the morphology of etch pits formed in the presence of strong organic chelators, EDTA and DTPA, and 4) experiments using dialysis membranes to separate barite from bacteria suggest that direct contact between the two is not required in order to promote dissolution. These results suggest that Halanaerobium increase the rate of barite dissolution in anoxic and

  5. The Toarcian Oceanic Anoxic Event: a shallow-water perspective

    NASA Astrophysics Data System (ADS)

    Bodin, Stephane; Krencker, Francois-Nicolas; Kabiri, Lahcen; Immenhauser, Adrian

    2015-04-01

    The Toarcian ocean anoxic event (T-OAE, ca. 183 Ma) corresponds to a major perturbation of the carbon cycle as reflected by a marked decrease (2 to 7 per mil) in carbon-isotope ratios of various carbonate and organic matter phases. Severe environmental perturbations and biotic turnovers are accompanying the unfolding of the T-OAE, which is thought to be initiated by the activity of the Karoo-Ferrar large igneous province. Most of the studies dedicated to the T-OAE were however undertaken in mud-rich, deep-water setting, leaving vast uncertainties about its shallow-water expression and accompanying sea-level fluctuations. Here we present an extensive sedimentological dataset of the shallow-water record of the T-OAE within the Central High Atlas Basin of Morocco. The combination of ammonite and brachiopod biostratigraphy, together with carbon-isotope chemostratigraphy (on both carbonate and organic matter) allows a precise location of the T-OAE in the studied shallow-water sections. Thanks to well-exposed and thick successions, relative sea-level variations were reconstructed on a high-resolution scale, highlighting several important facts. Firstly, the T-OAE interval is preceded by a 50 meters-deep incised valley, observed within the uppermost Polymorphum ammonite zone. Similar observations have been reported from Euro-boreal basins and, together with published evidences of coeval occurrence of relatively cool seawater temperature and low atmospheric pCO2, we postulate that this forced regression is driven by glacio-eustasy. This points at the occurrence of a "cold snap" event just prior to the onset of the T-OAE. Secondly, the inception of the T-OAE is marked by the demise of the Lithiotid-dominated neritic carbonate factory, replaced by siliciclastic-dominated sedimentation during the T-OAE negative carbon isotope shift. Thirdly, an important progradation of oo-biodetritic shoal occurs during the negative carbon isotope plateau, underlying that the renewal of

  6. Dysoxic/anoxic episodes in the Aptian-Albian (Early Cretaceous)

    NASA Astrophysics Data System (ADS)

    Bralower, Timothy J.; Sliter, William V.; Arthur, Michael A.; Leckie, R. Mark; Allard, David; Schlanger, Seymour O.

    New biostratigraphic data suggest, for the first time, that the long Aptian-Albian Oceanic Anoxic Event was marked by at least three distinct, relatively brief episodes of widespread dysoxia/anoxia which interrupted generally oxygenated conditions. The high-resolution, integrated foraminiferal and nannofossil biostratigraphy derived here allows recognition of an apparently ocean-wide dysoxic/anoxic episode in the early Aptian (Globigerinelloides blowi foraminiferal Zone, Chiastozygus litterarius nannofossil Zone, Conusphaera rothii nannofossil Subzone, shortly after magnetic Chron CMO). Equally widespread, but distributionally patchier dysoxic/anoxic episodes occurred in the early Albian (Hedbergella planispira foraminiferal Zone, Prediscosphaera columnata nannofossil Zone, subzone NC8B) and early late Albian (Biticinella breggiensis foraminiferal Zone, Axopodorhabdus albianus nannofossil Zone, subzone NC9B). These episodes can be best recognized in highly carbonaceous sediments deposited in epicontinental basins, now exposed on land, including the lower Aptian "Livello Selli" of the Italian Apennines, the lower Albian "Niveau Paquier" of the Fosse Vocontienne, France, and the lower upper Albian Toolebuc Formation of the Eromanga Basin, Queensland, Australia. Our data indicate that these horizons correlate at the nannofossil subzonal level to carbonaceous intervals in DSDP/ODP sites which were deposited in pelagic and hemipelagic oceanic settings. Although none of these episodes is associated with major biotic extinctions, they are characterized by changes, of variable magnitude, in the community structure of planktonic foraminifera, which commonly consist of a low-diversity assemblage of opportunistic taxa or are entirely absent. Nannofossil taxa in these horizons do not change as radically, but in some sites show marked nearshore affinities or, in other sequences, are possibly replaced by other phytoplankton. Dissolution events cannot be entirely ruled out as a

  7. Chlorofluorocarbon-11 removal in anoxic marine waters

    SciTech Connect

    Bullister, J.L.; Lee, B.S.

    1995-07-15

    Measurements of the chlorofluorocarbons CCl{sub 3}F (F-11) and CCl{sub 2}F{sub 2}(F-12) made in the subsurface anoxic zones of the Black Sea and Saanich Inlet, B.C., Canada show a pronounced depletion of dissolved F-11. These zones are strongly reducing and are characterized by the absence of dissolved nitrate (NO{sub 3}{sup {minus}}) and the presence of hydrogen sulfide (H{sub 2}S). Models incorporating the atmospheric input histories of these CFCs and the observed distributions are used to estimate residence times for water in these zones and first order in-situ removal rates for F-11. In contrast, measurements in the mid-depth low-oxygen zone of the eastern Pacific (where NO{sub 3}{sup {minus}} is present and H{sub 2}S is below detection limits) do not show evidence of similar rapid F-11 removal. 22 refs., 3 figs., 1 tab.

  8. Oxygenation of anoxic sediments triggers hatching of zooplankton eggs.

    PubMed

    Broman, Elias; Brüsin, Martin; Dopson, Mark; Hylander, Samuel

    2015-10-22

    Many coastal marine systems have extensive areas with anoxic sediments and it is not well known how these conditions affect the benthic-pelagic coupling. Zooplankton lay their eggs in the pelagic zone, and some sink and lie dormant in the sediment, before hatched zooplankton return to the water column. In this study, we investigated how oxygenation of long-term anoxic sediments affects the hatching frequency of dormant zooplankton eggs. Anoxic sediments from the brackish Baltic Sea were sampled and incubated for 26 days with constant aeration whereby, the sediment surface and the overlying water were turned oxic. Newly hatched rotifers and copepod nauplii (juveniles) were observed after 5 and 8 days, respectively. Approximately 1.5 × 10(5) nauplii m(-2) emerged from sediment turned oxic compared with 0.02 × 10(5) m(-2) from controls maintained anoxic. This study demonstrated that re-oxygenation of anoxic sediments activated a large pool of buried zooplankton eggs, strengthening the benthic-pelagic coupling of the system. Modelling of the studied anoxic zone suggested that a substantial part of the pelagic copepod population can derive from hatching of dormant eggs. We suggest that this process should be included in future studies to understand population dynamics and carbon flows in marine pelagic systems.

  9. Oxygenation of anoxic sediments triggers hatching of zooplankton eggs

    PubMed Central

    Broman, Elias; Brüsin, Martin; Dopson, Mark; Hylander, Samuel

    2015-01-01

    Many coastal marine systems have extensive areas with anoxic sediments and it is not well known how these conditions affect the benthic–pelagic coupling. Zooplankton lay their eggs in the pelagic zone, and some sink and lie dormant in the sediment, before hatched zooplankton return to the water column. In this study, we investigated how oxygenation of long-term anoxic sediments affects the hatching frequency of dormant zooplankton eggs. Anoxic sediments from the brackish Baltic Sea were sampled and incubated for 26 days with constant aeration whereby, the sediment surface and the overlying water were turned oxic. Newly hatched rotifers and copepod nauplii (juveniles) were observed after 5 and 8 days, respectively. Approximately 1.5 × 105 nauplii m−2 emerged from sediment turned oxic compared with 0.02 × 105 m−2 from controls maintained anoxic. This study demonstrated that re-oxygenation of anoxic sediments activated a large pool of buried zooplankton eggs, strengthening the benthic–pelagic coupling of the system. Modelling of the studied anoxic zone suggested that a substantial part of the pelagic copepod population can derive from hatching of dormant eggs. We suggest that this process should be included in future studies to understand population dynamics and carbon flows in marine pelagic systems. PMID:26468249

  10. The History and Dynamics of Anoxia in Cariaco Basin

    NASA Astrophysics Data System (ADS)

    Peterson, L. C.; Gibson, K. A.; Black, D. E.; Thunell, R. C.; Lea, D. W.; Haug, G. H.

    2007-12-01

    The Cariaco Basin is the largest modern anoxic marine basin in the world after the Black Sea. Although anoxia involves complex interactions between biological, chemical, and physical processes, the presence or absence of anoxic conditions in the marine environment ultimately reflects a balance between oxygen consumption and supply. A history of this balance in Cariaco Basin, and clues to the climatic and oceanographic controls, is preserved in the underlying sediment record. Much of the late Quaternary sequence in Cariaco Basin is laminated, indicating deposition under anoxic conditions that preclude biological mixing. However, the existence of significant bioturbated intervals indicate past oscillations between oxic and anoxic conditions in the deep basin. To a first-order, glacioeustatic sea level changes appear to play a key role in whether or not anoxic conditions in Cariaco Basin develop, with the effects of sea level on sill depth controlling the availability of nutrients and hence surface productivity. During glacial lowstands, reduced input of nutrients to the basin results in low productivity and oxygenated conditions, while interglacial times of high sea level are linked to strong upwelling, an increased supply of sinking organic detritus and sea floor anoxia. Superimposed on this pattern are millennial-scale oscillations in oxygen levels, best revealed by high-resolution scanning XRF analyses of redox-sensitive elements such as Mo and Cd. During the last glacial, intervals of anoxic deposition coincide one for one with warm interstadials as recorded in Greenland ice cores and require a different explanation. At such times, high productivity may be stimulated by riverine delivery of nutrients rather than by upwelling.

  11. Internal load management in eutrophic, anoxic environments. The role of natural zeolite.

    NASA Astrophysics Data System (ADS)

    Gianni, Areti; Zacharias, Ierotheos

    2015-04-01

    During the last decades, the increase of the nutrient and organic load inflows in the coastal zone increased the number of the anoxic environments. Inputs' control constitutes one of the basic practices for the eutrophic/anoxic aquatic ecosystems management. However, the induced changes at the ecosystem characteristics resulting from the trophic state alteration, and anoxic conditions prevalence, render the ecosystem's restoration difficult if not impossible. Bottom water anoxia accelerates PO43-, NH4+ and S2- recycling and accumulation from organic matter decomposition. This, toxic layer is a permanent menace for the balance of the entire ecosystem, as it can supply PO43-, NH4+ and S2- to the surface layers altering their qualitative character and threatening the welfare of fishes and other aquatic organisms. Having as objective the water basins' internal load control and based on practices are used in eutrophic environments' restoration, this study is referred to the role of the natural zeolite in eutrophic/anoxic ecosystems management. For the first time are presented, results from S2- removal experiments using the zeolitic mineral mordenite, [(Na2, Ca, K2)4 (H2O)28] [Al8Si40O96]. Four different sets of experiments were conducted, in order to examine zeolite's removal capacity of S2- in aquatic solutions, under a wide range of physicochemical parameters. More specific: a) the effect of initial pH on the removal process, b) the removal process kinetics, c) the removal process isotherms and d) the effect of salinity on the removal process were studied. Natural zeolite has the ability to neutralize the pH of aqueous solutions, thus all the experiments were practically performed at pH 7. Initially sulfides concentration range from 1 to 10mg/l. Zeolite's removal capability appeared to be directly depended on the S2- initial concentration. For initial concentration of 1mg/l, the removal rate reached up to 90% after 24h. The maximum zeolite removal capacity was

  12. Extreme seawater compositions during Oceanic Anoxic Events

    NASA Astrophysics Data System (ADS)

    Cohen, A.; Bottini, C.; Dickson, A. J.; Izon, G. J.; Coe, A. L.

    2012-12-01

    For almost the entire duration of the Phanerozoic, the oceans have remained well oxygenated and highly conducive to the development of animal and plant life. However, there have been relatively brief intervals, known as Oceanic Anoxic Events (OAEs), when a very significant expansion of low-oxygen regions occurred throughout the world's oceans. OAEs were characterised by highly atypical seawater chemistry, as reflected in the chemical and isotopic compositions of contemporaneous sediments and fossil remains. These oxygen-deficient intervals also exerted profound pressures on many marine species as indicated by major changes in species populations and distributions. High-resolution chemical and isotopic data recovered from marine sediments and sedimentary rocks, together with biotic information, provide us with the best means of understanding the significance of OAEs and their place in the evolution of the Earth system. We present new Mo- and Os-isotope and geochemical data from OAE 1a (early Cretaceous), which help define how this event evolved in relation to the other major environmental parameters - including global warming, continental weathering and Ontong-Java volcanism - of that time. We compare these new observations with published results from other Mesozoic OAEs and the PETM. Recently published Os-isotope data from DSDP site 463 (mid-Pacific) [1] and northern Italy [1, 2] show that the Os budget of the oceans was dominated for a period of c. 880 ka during OAE 1a by the hydrothermal flux of unradiogenic Os from the Ontong-Java province. The observation of identical Os-isotope compositions at these two very distant sites indicates that seawater was well mixed at that time. Over the same interval, the seawater Mo-isotope composition, based upon well-preserved samples from Italy, was persistently atypical, with δ98/95Mo ranging between -0.7 and +0.7 permil [3]. All the samples analysed here accumulated under highly anoxic conditions and contain highly abundant

  13. Model photoautrophs isolated from a Proterozoic ocean analog - aerobic life under anoxic conditions

    NASA Astrophysics Data System (ADS)

    Hamilton, T. L.; de Beer, D.; Klatt, J.; Macalady, J.; Weber, M.; Lott, C.; Chennu, A.

    2016-12-01

    The 1-2 billion year delay before the final rise of oxygen at the end of the Proterozoic represents an important gap in our understanding of ancient biogeochemical cycling. Primary production fueled by sulfide-dependent anoxygenic photosynthesis, including the activity of metabolically versatile cyanobacteria, has been invoked as a mechanism for sustaining low atmospheric O2 throughout much of the Proterozoic. However, we understand very little about photoautotrophs that inhabit Proterozoic-like environments present on Earth today. Here we report on the isolation and characterization of a cyanobacterium and a green sulfur bacterium that are the dominant members of pinnacle mats in Little Salt Spring—a karst sinkhole in Florida with perennially low levels of dissolved oxygen and sulfide. The red pinnacle mats bloom in the anoxic basin of the sinkhole and receive light that is of very poor quality to support photosynthesis. Characterization of the isolates is consistent with observations of oxygenic and anoxygenic photosynthesis in situ—both organisms perform anoxygenic photosynthesis under conditions of very low light quality and quantity. Oxygenic photosynthesis by the cyanobacterium isolate is inhibited by the presence of sulfide and under optimal light conditions, rates of anoxygenic photosynthesis are nearly double that of oxygenic photosynthesis. The green sulfur bacterium is tolerant of oxygen and has a very low affinity for sulfide. In Little Salt Spring, oxygenic photosynthesis occurs for only four hours a day and the water column remains anoxic because of a continuous supply of sulfide. Isolation and characterization of these photoautotrophs combined with our high resolution microsensor data in situ highlight microbial biogeochemical cycling in this exceptional site where aerobic microorganisms persist in a largely anoxic ecosystem.

  14. Molybdenum-isotope chemostratigraphy and paleoceanography of the Toarcian Oceanic Anoxic Event (Early Jurassic)

    NASA Astrophysics Data System (ADS)

    Dickson, Alexander J.; Gill, Benjamin C.; Ruhl, Micha; Jenkyns, Hugh C.; Porcelli, Donald; Idiz, Erdem; Lyons, Timothy W.; van den Boorn, Sander H. J. M.

    2017-08-01

    Molybdenum (Mo)-isotope chemostratigraphy of organic-rich mudrocks has been a valuable tool for testing the hypothesis that the Toarcian Oceanic Anoxic Event (T-OAE, Early Jurassic, 183 Ma) was characterized by the spread of marine euxinia (and organic matter burial) at a global scale. However, the interpretation of existing Mo-isotope data for the T-OAE (from Yorkshire, Cleveland Basin, U.K.) is equivocal. In this study, three new Mo-isotope profiles are presented: from Dotternhausen Quarry (South German Basin, Germany), the Rijswijk core (West Netherlands Basin, Netherlands), and the Dogna core (Belluno Basin, northern Italy). Precise biostratigraphic and chemostratigraphic correlation between the three sites allows a direct comparison of the data, enabling some key conclusions to be reached: (i) The Mo-isotope composition of seawater during the peak of the T-OAE was probably close to 1.45‰, implicating a greater removal flux of sulphides from seawater, and a larger extent of global seafloor euxinia compared to the present day; (ii) Mo-isotope cycles previously identified in the Yorkshire sedimentary succession are attributed to changes in the degree of local Mo drawdown from overlying Cleveland Basin seawater; (iii) The consistency of the new multisite Mo-isotope data set indicates a secular reduction in the burial of Mo globally in the late stages of the T-OAE, implying a contraction in the extent of global marine euxinia; (iv) Subtle differences in the Mo-isotope composition of deposits formed in different euxinic subbasins of the European epicontinental shelf were probably governed by local variations in basin hydrography and rates of water renewal.

  15. The Cenomanian-Turonian oceanic anoxic event in Tibet, a real anoxic condition? Clues from Phosphorus, Carbon and Traces Elements accumulations.

    NASA Astrophysics Data System (ADS)

    Bomou, B.; Adatte, T.; Föllmi, K. B.; Caron, M.; Tantawy, A. A.; Fleitmann, D.; Matera, V.; Huang, Y.

    2009-04-01

    The Cenomanian-Turonian boundary is marked by an Oceanic Anoxic Event (OAE 2) characterized by finely laminated organic carbon rich sediments deposited under oxygen depleted conditions, coinciding with a positive shift in δ13C isotope excursion. The main goal of the present research is to get a better understanding of mechanisms which triggered these OAEs, and particularly the paleoenvironmental conditions which characterized the onset of that major anoxic event and their evolution. Mort (2007) demonstrated that the onset of the Cenomanian-Turonian OAE was triggered by a short-lived but significant increase in phosphorus burial. Then bottom waters became anoxic and switched from being a P sink to a P source, sustaining the productivity in a positive feedback loop. Increased aridity, removal of atmospheric CO2 by burial as organic carbon in black shales and reduction in nutrient availability may have been factors bringing about the return to more oxic oceans. However, Total Phosphorus (Ptot) and trace metals behaviour is not well known at larger scale, away from main black shales source (Western Tethys and Central Atlantic). It is especially interesting to see if P distribution will show a similar maximum predating the positive carbon excursion. We investigate therefore the section of Gongzha (Tibet, China) located at the north margin of the Indian plate in the Tethys Himalayas zone (SE Tethys). These sediments are deposited in open marine basin and slope settings under hemipelagic environment (Li et al., 2006). Clay analyses show that the sediments have been overprinted by burial diagenesis and tectonic processes, but the biostratigraphy by foraminifera and nannofossils, microfacies and carbon stable isotopes data indicate a quite good preservation and absence of significant hiatus. Carbon isotope analyses exhibit the classical C-T positive shift with a first peak near the end of R. cushmani zone, a second in the lower part of W. archaeocretacea zone, followed by

  16. Nitrogen losses in anoxic marine sediments driven by Thioploca-anammox bacterial consortia.

    PubMed

    Prokopenko, M G; Hirst, M B; De Brabandere, L; Lawrence, D J P; Berelson, W M; Granger, J; Chang, B X; Dawson, S; Crane, E J; Chong, L; Thamdrup, B; Townsend-Small, A; Sigman, D M

    2013-08-08

    Ninety per cent of marine organic matter burial occurs in continental margin sediments, where a substantial fraction of organic carbon escapes oxidation and enters long-term geologic storage within sedimentary rocks. In such environments, microbial metabolism is limited by the diffusive supply of electron acceptors. One strategy to optimize energy yields in a resource-limited habitat is symbiotic metabolite exchange among microbial associations. Thermodynamic and geochemical considerations indicate that microbial co-metabolisms are likely to play a critical part in sedimentary organic carbon cycling. Yet only one association, between methanotrophic archaea and sulphate-reducing bacteria, has been demonstrated in marine sediments in situ, and little is known of the role of microbial symbiotic interactions in other sedimentary biogeochemical cycles. Here we report in situ molecular and incubation-based evidence for a novel symbiotic consortium between two chemolithotrophic bacteria--anaerobic ammonium-oxidizing (anammox) bacteria and the nitrate-sequestering sulphur-oxidizing Thioploca species--in anoxic sediments of the Soledad basin at the Mexican Pacific margin. A mass balance of benthic solute fluxes and the corresponding nitrogen isotope composition of nitrate and ammonium fluxes indicate that anammox bacteria rely on Thioploca species for the supply of metabolic substrates and account for about 57 ± 21 per cent of the total benthic N2 production. We show that Thioploca-anammox symbiosis intensifies benthic fixed nitrogen losses in anoxic sediments, bypassing diffusion-imposed limitations by efficiently coupling the carbon, nitrogen and sulphur cycles.

  17. Metallogeny, structural, lithological and time controls of ore deposition in anoxic environments

    NASA Astrophysics Data System (ADS)

    Kříbek, B.

    1991-04-01

    Accumulation of metals in anoxic environments occurs by sorption and precipitation from seawater, fossil brines or hydrothermal solutions. Metals can be remobilized during subsequent metamorphic and magmatic processes and form ore deposits. This type of mineralization is governed chiefly by the type of tectonic setting of the anoxic environment. Carbonaceous sediments of passive margins contain only subeconomic concentrations of uranium, vanadium and molybdenum. Cubearing black shales and the submarine-exhalative type of mineralization are confined to the environments of continental rifts and aulacogens or to back-arc basins of active margins. Metamorphogenic deposits are mainly connected with collision margins but they may also occur in other types of tectonic environments. The formation of Cu-bearing black shales was controlled by period of low sea-level during the break-up of supercontinents in the Earth's evolution. Increased contents of uranium and vanadium accumulated in black shales in periods of sealevel highstands. Lithological control is apparent in deposits of Cu-bearing and uraniferous black shales. On the contrary, the occurrence of polymetallic mineralization does not depend on the lithological maturity of carbonaceous sediments.

  18. Dynamic anoxic ferruginous conditions during the end-Permian mass extinction and recovery

    PubMed Central

    Clarkson, M. O.; Wood, R. A.; Poulton, S. W.; Richoz, S.; Newton, R. J.; Kasemann, S. A.; Bowyer, F.; Krystyn, L.

    2016-01-01

    The end-Permian mass extinction, ∼252 million years ago, is notable for a complex recovery period of ∼5 Myr. Widespread euxinic (anoxic and sulfidic) oceanic conditions have been proposed as both extinction mechanism and explanation for the protracted recovery period, yet the vertical distribution of anoxia in the water column and its temporal dynamics through this time period are poorly constrained. Here we utilize Fe–S–C systematics integrated with palaeontological observations to reconstruct a complete ocean redox history for the Late Permian to Early Triassic, using multiple sections across a shelf-to-basin transect on the Arabian Margin (Neo-Tethyan Ocean). In contrast to elsewhere, we show that anoxic non-sulfidic (ferruginous), rather than euxinic, conditions were prevalent in the Neo-Tethys. The Arabian Margin record demonstrates the repeated expansion of ferruginous conditions with the distal slope being the focus of anoxia at these times, as well as short-lived episodes of oxia that supported diverse biota. PMID:27433855

  19. Dynamic anoxic ferruginous conditions during the end-Permian mass extinction and recovery

    NASA Astrophysics Data System (ADS)

    Clarkson, M. O.; Wood, R. A.; Poulton, S. W.; Richoz, S.; Newton, R. J.; Kasemann, S. A.; Bowyer, F.; Krystyn, L.

    2016-07-01

    The end-Permian mass extinction, ~252 million years ago, is notable for a complex recovery period of ~5 Myr. Widespread euxinic (anoxic and sulfidic) oceanic conditions have been proposed as both extinction mechanism and explanation for the protracted recovery period, yet the vertical distribution of anoxia in the water column and its temporal dynamics through this time period are poorly constrained. Here we utilize Fe-S-C systematics integrated with palaeontological observations to reconstruct a complete ocean redox history for the Late Permian to Early Triassic, using multiple sections across a shelf-to-basin transect on the Arabian Margin (Neo-Tethyan Ocean). In contrast to elsewhere, we show that anoxic non-sulfidic (ferruginous), rather than euxinic, conditions were prevalent in the Neo-Tethys. The Arabian Margin record demonstrates the repeated expansion of ferruginous conditions with the distal slope being the focus of anoxia at these times, as well as short-lived episodes of oxia that supported diverse biota.

  20. Microbial community dynamics in a seasonally anoxic fjord: Saanich Inlet, British Columbia.

    PubMed

    Zaikova, Elena; Walsh, David A; Stilwell, Claire P; Mohn, William W; Tortell, Philippe D; Hallam, Steven J

    2010-01-01

    Dissolved oxygen concentration plays a major role in shaping biotic interactions and nutrient flows within marine ecosystems. Throughout the global ocean, regions of low dissolved oxygen concentration (hypoxia) are a common and expanding feature of the water column, with major feedback on productivity and greenhouse gas cycling. To better understand microbial diversity underlying biogeochemical transformations within oxygen-deficient oceanic waters, we monitored and quantified bacterial and archaeal community dynamics in relation to dissolved gases and nutrients during a seasonal stratification and deep water renewal cycle in Saanich Inlet, British Columbia, a seasonally anoxic fjord. A number of microbial groups partitioned within oxygen-deficient waters including Nitrospina and SAR324 affiliated with the delta-proteobacteria, SAR406 and gamma-proteobacteria related to thiotrophic gill symbionts of deep-sea clams and mussels. Microbial diversity was highest within the hypoxic transition zone decreasing dramatically within anoxic basin waters and temporal patterns of niche partitioning were observed along defined gradients of oxygen and phosphate. These results provide a robust comparative phylogenetic framework for inferring systems metabolism of nitrogen, carbon and sulfur cycling within oxygen-deficient oceanic waters and establish Saanich Inlet as a tractable model for studying the response of microbial communities to changing levels of water column hypoxia.

  1. Uranium(IV) adsorption by natural organic matter in anoxic sediments

    DOE PAGES

    Bone, Sharon E.; Dynes, James J.; Cliff, John; ...

    2017-01-24

    Uranium is an important carbon-free fuel source and environmental contaminant that accumulates in the tetravalent state, U(IV), in anoxic sediments, such as ore deposits, marine basins, and contaminated aquifers. However, little is known about the speciation of U(IV) in low-temperature geochemical environments, inhibiting the development of a conceptual model of U behavior. Until recently, U(IV) was assumed to exist predominantly as the sparingly soluble mineral uraninite (UO2+x) in anoxic sediments; however, studies now show that this is not often the case. Yet a model of U(IV) speciation in the absence of mineral formation under field-relevant conditions has not yet beenmore » developed. Uranium(IV) speciation controls its reactivity, particularly its susceptibility to oxidative mobilization, impacting its distribution and toxicity. Here we show adsorption to organic carbon and organic carbon-coated clays dominate U(IV) speciation in an organic-rich natural substrate under field-relevant conditions. Whereas previous research assumed that U(IV) speciation is dictated by the mode of reduction (i.e., whether reduction is mediated by microbes or by inorganic reductants), our results demonstrate that mineral formation can be diminished in favor of adsorption, regardless of reduction pathway. Projections of U transport and bioavailability, and thus its threat to human and ecosystem health, must consider U(IV) adsorption to organic matter within the sediment environment.« less

  2. Uranium(IV) adsorption by natural organic matter in anoxic sediments

    DOE PAGES

    Bone, Sharon E.; Dynes, James J.; Cliff, John; ...

    2017-01-24

    Uranium is an important carbon-free fuel source and environmental contaminant that accumulates in the tetravalent state, U(IV), in anoxic sediments, such as ore deposits, marine basins, and contaminated aquifers. However, little is known about the speciation of U(IV) in low-temperature geochemical environments, inhibiting the development of a conceptual model of U behavior. Until recently, U(IV) was assumed to exist predominantly as the sparingly soluble mineral uraninite (UO2+x) in anoxic sediments; however, studies now show that this is not often the case. Yet a model of U(IV) speciation in the absence of mineral formation under field-relevant conditions has not yet beenmore » developed. Uranium(IV) speciation controls its reactivity, particularly its susceptibility to oxidative mobilization, impacting its distribution and toxicity. Here we show adsorption to organic carbon and organic carbon-coated clays dominate U(IV) speciation in an organic-rich natural substrate under field-relevant conditions. Whereas previous research assumed that U(IV) speciation is dictated by the mode of reduction (i.e., whether reduction is mediated by microbes or by inorganic reductants), our results demonstrate that mineral formation can be diminished in favor of adsorption, regardless of reduction pathway. Projections of U transport and bioavailability, and thus its threat to human and ecosystem health, must consider U(IV) adsorption to organic matter within the sediment environment.« less

  3. Dynamic anoxic ferruginous conditions during the end-Permian mass extinction and recovery.

    PubMed

    Clarkson, M O; Wood, R A; Poulton, S W; Richoz, S; Newton, R J; Kasemann, S A; Bowyer, F; Krystyn, L

    2016-07-19

    The end-Permian mass extinction, ∼252 million years ago, is notable for a complex recovery period of ∼5 Myr. Widespread euxinic (anoxic and sulfidic) oceanic conditions have been proposed as both extinction mechanism and explanation for the protracted recovery period, yet the vertical distribution of anoxia in the water column and its temporal dynamics through this time period are poorly constrained. Here we utilize Fe-S-C systematics integrated with palaeontological observations to reconstruct a complete ocean redox history for the Late Permian to Early Triassic, using multiple sections across a shelf-to-basin transect on the Arabian Margin (Neo-Tethyan Ocean). In contrast to elsewhere, we show that anoxic non-sulfidic (ferruginous), rather than euxinic, conditions were prevalent in the Neo-Tethys. The Arabian Margin record demonstrates the repeated expansion of ferruginous conditions with the distal slope being the focus of anoxia at these times, as well as short-lived episodes of oxia that supported diverse biota.

  4. Microbial Community of a Hydrothermal Mud Vent Underneath the Deep-Sea Anoxic Brine Lake Urania (Eastern Mediterranean)

    NASA Astrophysics Data System (ADS)

    Yakimov, Michail M.; Giuliano, Laura; Cappello, Simone; Denaro, Renata; Golyshin, Peter N.

    2007-04-01

    The composition of a metabolically active prokaryotic community thriving in hydrothermal mud fluids of the deep-sea hypersaline anoxic Western Urania Basin was characterized using rRNA-based phylogenetic analysis of a clone library. The physiologically active prokaryotic assemblage in this extreme environment showed a great genetic diversity. Most members of the microbial community appeared to be affiliated to yet uncultured organisms from similar ecosystems, i.e., deep-sea hypersaline basins and hydrothermal vents. The bacterial clone library was dominated by phylotypes affiliated with the epsilon- Proteobacteria subdivision recognized as an ecologically significant group of bacteria inhabiting deep-sea hydrothermal environments. Almost 18% of all bacterial clones were related to delta- Proteobacteria, suggesting that sulfate reduction is one of the dominant metabolic processes occurring in warm mud fluids. The remaining bacterial phylotypes were related to alpha- and beta- Proteobacteria, Actinobacteria, Bacteroides, Deinococcus-Thermus, KB1 and OP-11 candidate divisions. Moreover, a novel monophyletic clade, deeply branched with unaffiliated 16S rDNA clones was also retrieved from deep-sea sediments and halocline of Urania Basin. Archaeal diversity was much lower and detected phylotypes included organisms affiliated exclusively with the Euryarchaeota. More than 96% of the archaeal clones belonged to the MSBL-1 candidate order recently found in hypersaline anoxic environments, such as endoevaporitic microbial mats, Mediterranean deep-sea mud volcanoes and anoxic basins. Two phylotypes, represented by single clones were related to uncultured groups DHVE-1 and ANME-1. Thus, the hydrothermal mud of hypersaline Urania Basin seems to contain new microbial diversity. The prokaryotic community was significantly different from that occurring in the upper layers of the Urania Basin since 60% of all bacterial and 40% of all archaeal phylotypes were obtained only from mud

  5. Microbial community of a hydrothermal mud vent underneath the deep-sea anoxic brine lake Urania (eastern Mediterranean).

    PubMed

    Yakimov, Michail M; Giuliano, Laura; Cappello, Simone; Denaro, Renata; Golyshin, Peter N

    2007-04-01

    The composition of a metabolically active prokaryotic community thriving in hydrothermal mud fluids of the deep-sea hypersaline anoxic Western Urania Basin was characterized using rRNA-based phylogenetic analysis of a clone library. The physiologically active prokaryotic assemblage in this extreme environment showed a great genetic diversity. Most members of the microbial community appeared to be affiliated to yet uncultured organisms from similar ecosystems, i.e., deep-sea hypersaline basins and hydrothermal vents. The bacterial clone library was dominated by phylotypes affiliated with the epsilon-Proteobacteria subdivision recognized as an ecologically significant group of bacteria inhabiting deep-sea hydrothermal environments. Almost 18% of all bacterial clones were related to delta-Proteobacteria, suggesting that sulfate reduction is one of the dominant metabolic processes occurring in warm mud fluids. The remaining bacterial phylotypes were related to alpha- and beta-Proteobacteria, Actinobacteria, Bacteroides, Deinococcus-Thermus, KB1 and OP-11 candidate divisions. Moreover, a novel monophyletic clade, deeply branched with unaffiliated 16S rDNA clones was also retrieved from deep-sea sediments and halocline of Urania Basin. Archaeal diversity was much lower and detected phylotypes included organisms affiliated exclusively with the Euryarchaeota. More than 96% of the archaeal clones belonged to the MSBL-1 candidate order recently found in hypersaline anoxic environments, such as endoevaporitic microbial mats, Mediterranean deep-sea mud volcanoes and anoxic basins. Two phylotypes, represented by single clones were related to uncultured groups DHVE-1 and ANME-1. Thus, the hydrothermal mud of hypersaline Urania Basin seems to contain new microbial diversity. The prokaryotic community was significantly different from that occurring in the upper layers of the Urania Basin since 60% of all bacterial and 40% of all archaeal phylotypes were obtained only from mud

  6. Sequential anaerobic, aerobic/anoxic treatment of simulated landfill leachate.

    PubMed

    Agdag, O N; Sponza, D T

    2008-02-01

    In this study COD, ammonia and nitrate were treated through methanogenesis, nitrification denitrification and anammox processes in anaerobic-aerobic and anaerobic/anoxic sequential in leachate samples produced from municipal solid waste in an anaerobic simulated landfilling bioreactor. The experiments were performed in an upflow anaerobic sludge blanket reactor (UASB), aerobic completely stirred tank reactor (CSTR) and upflow anaerobic/anoxic sludge blanket reactor (UA/A(N)SB). Hydraulic retention times in anaerobic, aerobic and anaerobic/anoxic stages were 1, 3.6 and 1 days, respectively, through 244 days of total operation period with 168 days of adaptation period of microorganisms to the reactors. The organic loading rates increased from 5.9 to 50 kg COD m(-3) day(-1). The total COD and TN removal efficiencies of the anaerobic-aerobic-anoxic system were 96% and 99%, respectively, at an influent OLR as high as 50 kg COD m(-3) day(-1). The maximum methane percentage in the UASB reactor was 82% while the methane percentage was zero in UA/A(N)SB reactor for the aforementioned OLR at the end of steady-state conditions. NH4-N removal efficiency of the aerobic reactor was 90% while anaerobic ammonia oxidation was measured as 99% in the anoxic reactor. The denitrification efficiency was 99% in the same reactor. Total TN removal of the whole system was 99%.

  7. Expression profile of rice Hsp genes under anoxic stress.

    PubMed

    Mertz-Henning, L M; Pegoraro, C; Maia, L C; Venske, E; Rombaldi, C V; Costa de Oliveira, A

    2016-05-09

    Although flooding is one of the most important environmental stresses worldwide, not all plant species are intolerant to its effects. Species from semi-aquatic environments, such as rice, have the capacity to cope with flooding stress. Heat-shock proteins (Hsps) are thought to contribute to cellular homeostasis under both optimal and adverse growth conditions. Studies of gene expression in plants exposed to low levels of oxygen revealed the up-regulation of Hsp genes. However, it is not clear whether Hsp genes are transcribed as a function of tolerance or whether they represent a response to anoxic stress. Therefore, the accumulation of Hsp gene transcripts was investigated in two different cultivars, "Nipponbare" (flooding tolerant) and "IPSL 2070" (flooding sensitive), subjected to anoxic stress. Fifteen-day-old rice root seedlings from both cultivars were used. Four different treatments were performed: no anoxia (control); 24-h anoxia; 48-h anoxia; and 72-h anoxia. Anoxic stress was confirmed by the increased gene expression of alcohol dehydrogenase. The data obtained showed that both rice cultivars ("Nipponbare" and "IPSL 2070") accumulated Hsp gene transcripts under anoxic stress; however, the majority of the Hsp genes evaluated were responsive to anoxic stress in "IPSL 2070" (flooding sensitive), whereas in "Nipponbare" (flooding tolerant), only six genes were highly up-regulated. This suggests that although Hsps have an important role in the response to anoxia, they are not the major cause of tolerance.

  8. Initial steps in anoxic testosterone degradation by Steroidobacter denitrificans.

    PubMed

    Chiang, Yin-Ru; Fang, Jia-You; Ismail, Wael; Wang, Po-Hsiang

    2010-07-01

    Steroid compounds have many important physiological activities in higher organisms. Testosterone and related steroids are important environmental contaminants that disrupt the endocrine systems of animals. The degradation of steroids, especially under anoxic conditions, is challenging because of their complex chemical structure. A denitrifying gamma-proteobacterium, Steroidobacter denitrificans, able to grow anaerobically on a variety of steroids as the sole carbon and energy source was adopted as a model organism to study the anoxic degradation of testosterone. We identified the initial intermediates involved in the anoxic testosterone degradation pathway of S. denitrificans. We demonstrated that under anoxic conditions, S. denitrificans initially oxidizes testosterone to 1-dehydrotestosterone, which is then transformed to androsta-1,4-diene-3,17-dione. In addition, it seems that androst-4-en-3,17-dione can also be directly produced from testosterone by S. denitrificans cells. In general, the initial steps of anoxic testosterone degradation by S. denitrificans are similar to those of the oxic pathway demonstrated in Comamonas testosteroni.

  9. Fallout plutonium in two oxic-anoxic environments

    SciTech Connect

    Sanchez, A.L.; Murray, J.W.; Schell, W.R.; Miller, L.G.

    1986-09-01

    The profiles of soluble fallout plutonium in two partially anoxic waters revealed minimum concentrations at the O/sub 2/-H/sub 2/S interface, indicating Pu removal onto particulate phases of Fe and other oxidized species that form during the redox cycle. In Saanich Inlet, an intermittently anoxic fjord in Vancouver Island, Canada, the concentration of soluble Pu in the anoxic zone was slightly less than in the oxygenated surface layer. In Soap Lake, a saline meromictic lake in eastern Washington State, Pu concentrations i the permanently anoxic zone were at least an order of magnitude higher than at the surface. Differences in the chemical characteristics of these two waters suggest important chemical species that influenced the observed Pu distribution. In the permanently anoxic zone of Soap Lake, high values of total alkalinity ranging from 940 to 1500 meq liter/sup -1/, sulfide species from 38 to 128 ..mu..M, dissolved organic carbon from 163 to 237 mg liter/sup -1/, and total dissolved solids from 80 to 140 ppt, all correlated with the observed high concentration of Pu. In Saanich Inlet, where total alkalinity ranged from 2.1 to 2.4 meq liter/sup -1/ and salinity from 25 to 32 per thousand and H/sub 2/S concentration in May 1981 showed a maximum of 8..mu..M, the observed Pu concentrations were significantly lower than for the Soap Lake monimolimnion.

  10. Aptian anoxia in the Pacific Basin

    SciTech Connect

    Sliter, W.V. )

    1989-10-01

    Marine strata of Aptian age in the Pacific Basin include two distinct levels that represent episodes during which sediments rich in organic carbon were deposited. Both episodes lasted less than 1 m.y., as revealed in strata deposited atop submerged topographic highs. One unusually widespread episode of early Aptian age ({approximately}117.5 Ma) correlates with coeval units in Europe and thus is analogous to the Cenomanian-Turonian oceanic anoxic event in its short duration and wide geographic extent. The second episode of late Aptian age ({approximately}116.5 Ma) is restricted to allochthonous pelagic deposits in the Franciscan Complex of California. These results support the concept of widespread and narrowly synchronous anoxic events. Further, they show that organic carbon deposition in the Pacific Basin took place in intermediate water oxygen-minimum zones and thus differed in the mode of deposition, and hence paleoceanography, from that in other middle Cretaceous ocean basins.

  11. The early Toarcian anoxic event: what the beginning and the end of the story are?

    NASA Astrophysics Data System (ADS)

    Mattioli, Emanuela; Plancq, Julien; Raucsik, Béla

    2010-05-01

    The early Toarcian anoxic event: what the beginning and the end of the story are? E. Mattioli (1), J. Plancq (1), and B. Rauksik (2) (1) UMR 5125 PEPS, CNRS, France; Université Lyon 1, Campus de la DOUA, Bâtiment Géode, 69622 Villeurbanne Cedex, France (emanuela.mattioli@univ-lyon1.fr) (2) Department of Earth and Environmental Sciences, University of Pannonia, Veszprém, Hungary The early Toarcian anoxic event (T-OAE) and the associated biotic crisis have received much attention in the last decade. However, the events forewarning the crisis as well as its aftermath are still poorly known. The T-OAE coincides with a prominent carbon isotope negative excursion (T-CIE) that is preceded by an excursion of similar intensity at the Pliensbachian-Toarcian boundary (Hesselbo et al., 2007). The onset of T-CIE occurred some 700 kyr later than the end of the Boundary-CIE (Suan et al., 2008a). This succession of events demonstrates that the T-OAE was a complex suite of environmental perturbations. In this work, we focused on calcareous nannofossil assemblages occurring in the Peniche section (Portugal) during the Boundary-CIE with the aim to understand if calcifying plankton reacted in a similar/different way to the two CIEs. Also, two sections and one borehole located along a W-E transect, along the NW-Tethyan shelf (in the Yorkshire coast, in the E Paris Basin, and in Mecsek Basin, respectively), were investigated to assess which way calcareous nannoplankton recovered after the crisis, and if the recovery was a synchronous event. The production by nannoplankton collapsed during the T-CIE, as demonstrated by the lowest absolute abundance of nannofossils measured in Peniche and other studied sites (Mattioli et al., 2008). Besides this nannofossil abundance decrease, also the size of the incertae sedis Schizosphaerella test was drastically reduced (Suan et al., 2008b). If a similar size decrease is also recorded during the Boundary-CIE, calcareous nannofossil abundances are

  12. Anoxic survival of the Pacific hagfish (Eptatretus stoutii).

    PubMed

    Cox, Georgina K; Sandblom, Eric; Richards, Jeffrey G; Farrell, Anthony P

    2011-04-01

    It is not known how the Pacific hagfish (Eptatretus stoutii) can survive extended periods of anoxia. The present study used two experimental approaches to examine energy use during and following anoxic exposure periods of different durations (6, 24 and 36 h). By measuring oxygen consumption prior to anoxic exposure, we detected a circadian rhythm, with hagfish being active during night and showing a minimum routine oxygen consumption (RMR) during the daytime. By measuring the excess post-anoxic oxygen consumption (EPAOC) after 6 and 24 h it was possible to mathematically account for RMR being maintained even though heme stores of oxygen would have been depleted by the animal's metabolism during the first hours of anoxia. However, EPAOC after 36 h of anoxia could not account for RMR being maintained. Measurements of tissue glycogen disappearance and lactate appearance during anoxia showed that the degree of glycolysis and the timing of its activation varied among tissues. Yet, neither measurement could account for the RMR being maintained during even the 6-h anoxic period. Therefore, two independent analyses of the metabolic responses of hagfish to anoxia exposure suggest that hagfish utilize metabolic rate suppression as part of the strategy for longer-term anoxia survival.

  13. Sulfur during the Transition from Anoxic to Oxic Atmospheres

    NASA Technical Reports Server (NTRS)

    Zahnle, Kevin; Catling, David; Claire, Mark

    2006-01-01

    The invention of oxygenic photosynthesis was likely accompanied by the introduction of large amounts of O2 and complementary reduced gases (chiefly CH4) into the atmosphere. To first approximation the venting of O2 and CH4 are stochiometrically linked. We therefore present a suite of numerical photochemical models that address the anoxic-oxic transition in an atmosphere driven by large linked inputs of biogenic 02 and CH4. We find in general that, in steady state, there are two solutions, one oxic and the other anoxic. The anoxic solution appears to be linearly stable. If volcanic SO2 fluxes are large, S disproportionates into oxidized (H2S04) and reduced (S8) exit channels. As elemental sulfur is insoluble it provides a means of preserving photochemical mass-independent fractionation (MIF). On the other hand, if the source of volcanic SO2 is smaller than today, all S can leave the atmosphere as S8. Under these conditions there would be no MIF signal. The oxic solution appears to be linearly unstable. In the oxic solutions S is invariably oxidized to sulfate, and the MIF signal would be absent. The transitional atmosphere is relatively unstable and is also the most photochemically active. Consequently it is the transitional atmosphere, not the oxic or anoxic atmospheres, that has the lowest CH4 levels and weakest greenhouse warming. As a practical matter we expect the transitional atmospheres to vary strongly in response to diurnal and seasonal biological forcing.

  14. Sulfur during the Transition from Anoxic to Oxic Atmospheres

    NASA Technical Reports Server (NTRS)

    Zahnle, Kevin; Catling, David; Claire, Mark

    2006-01-01

    The invention of oxygenic photosynthesis was likely accompanied by the introduction of large amounts of O2 and complementary reduced gases (chiefly CH4) into the atmosphere. To first approximation the venting of O2 and CH4 are stochiometrically linked. We therefore present a suite of numerical photochemical models that address the anoxic-oxic transition in an atmosphere driven by large linked inputs of biogenic 02 and CH4. We find in general that, in steady state, there are two solutions, one oxic and the other anoxic. The anoxic solution appears to be linearly stable. If volcanic SO2 fluxes are large, S disproportionates into oxidized (H2S04) and reduced (S8) exit channels. As elemental sulfur is insoluble it provides a means of preserving photochemical mass-independent fractionation (MIF). On the other hand, if the source of volcanic SO2 is smaller than today, all S can leave the atmosphere as S8. Under these conditions there would be no MIF signal. The oxic solution appears to be linearly unstable. In the oxic solutions S is invariably oxidized to sulfate, and the MIF signal would be absent. The transitional atmosphere is relatively unstable and is also the most photochemically active. Consequently it is the transitional atmosphere, not the oxic or anoxic atmospheres, that has the lowest CH4 levels and weakest greenhouse warming. As a practical matter we expect the transitional atmospheres to vary strongly in response to diurnal and seasonal biological forcing.

  15. Isotope studies of carbonate rocks of La Luna Formation (Venezuela) to constrain the oceanic anoxic event 3 (OAE3)

    NASA Astrophysics Data System (ADS)

    Machado, M. C.; Chemale, F., Jr.; Kawashita, K.; Rey, O.; Moura, C. A. V.

    2016-12-01

    87Sr/86Sr ratios, δ13C, and δ18O determinations performed on 30 bulk carbonate rocks are presented to constrain the isotope characteristics regarding Oceanic Anoxic Event 3 in the La Luna Formation, Maracaibo Basin. The samples were collected along a 22 m profile in San Miguel region (Merida State, Venezuela). The exhibited 87Sr/86Sr ratios are between 0.707659, at the base, and 0.707733 at the top of studied section, corresponding estimated younger numerical ages than the inferred ages dated as Santonian (85.8-83.5 Ma) based on occurrence of Dicarinella asymetrica. The obtained 87Sr/86Sr ratios are certainly higher than expected for Santonian sea Sr and they are attributed to regular riverine strontium fluxes in the restricted (gulf-like) Maracaibo Basin. The values of δ18O data between -3.76‰ and -11.76‰ are distributed in two distinct clusters in a same way and coherent as for δ13C data which are in a range between -1.75‰ and -13.87‰. One of the clusters δ13C = -2.5 ± 1.0‰ and δ18O = -10.0 ± 1.5‰), illustrate the homogeneous marine deposition under tropical conditions, while the other, more variable, probably could reflect the cyclicity of temporally changes in Pacific versus Atlantic Ocean circulation with cooling water or cooling trend climate. These δ13C values around -2.5 ± 1.0‰ do not fit with the significant carbon isotope excursion as expected for the oceanic anoxic event (OAE) and support the work hypothesis that Coniacian-Santonian anoxic event (denominate as OAE3) is not a global one.

  16. Oceanic oxygenation events in the anoxic Ediacaran ocean.

    PubMed

    Sahoo, S K; Planavsky, N J; Jiang, G; Kendall, B; Owens, J D; Wang, X; Shi, X; Anbar, A D; Lyons, T W

    2016-09-01

    The ocean-atmosphere system is typically envisioned to have gone through a unidirectional oxygenation with significant oxygen increases in the earliest (ca. 635 Ma), middle (ca. 580 Ma), or late (ca. 560 Ma) Ediacaran Period. However, temporally discontinuous geochemical data and the patchy metazoan fossil record have been inadequate to chart the details of Ediacaran ocean oxygenation, raising fundamental debates about the timing of ocean oxygenation, its purported unidirectional rise, and its causal relationship, if any, with the evolution of early animal life. To better understand the Ediacaran ocean redox evolution, we have conducted a multi-proxy paleoredox study of a relatively continuous, deep-water section in South China that was paleogeographically connected with the open ocean. Iron speciation and pyrite morphology indicate locally euxinic (anoxic and sulfidic) environments throughout the Ediacaran in this section. In the same rocks, redox sensitive element enrichments and sulfur isotope data provide evidence for multiple oceanic oxygenation events (OOEs) in a predominantly anoxic global Ediacaran-early Cambrian ocean. This dynamic redox landscape contrasts with a recent view of a redox-static Ediacaran ocean without significant change in oxygen content. The duration of the Ediacaran OOEs may be comparable to those of the oceanic anoxic events (OAEs) in otherwise well-oxygenated Phanerozoic oceans. Anoxic events caused mass extinctions followed by fast recovery in biologically diversified Phanerozoic oceans. In contrast, oxygenation events in otherwise ecologically monotonous anoxic Ediacaran-early Cambrian oceans may have stimulated biotic innovations followed by prolonged evolutionary stasis. © 2016 John Wiley & Sons Ltd.

  17. Sulfur isotopic trends and pathways of iron sulfide formation in upper Holocene sediments of the anoxic Black Sea

    NASA Astrophysics Data System (ADS)

    Lyons, Timothy W.

    1997-08-01

    Down-core trends for extents of iron sulfidation in upper Holocene microlaminated deposits of the Black Sea abyssal plain imply that most of the pyrite in these sediments is formed in the sulfidic water column and/or very close to the sediment-water interface. Sulfur isotopic data for pyrite within microlaminated muds from two localities in the deep basin show striking uniformity between sites and down core, with a mean δ 34S CDT value of -37.2 ± 0.9‰ (1σ, n = 18). These isotopic trends support the hypothesis of early pyrite formation. Isotopic compositions of pyrite sulfur in the microlaminated bottom sediments are similar to those reported for particulate reduced sulfur collected in middepth sediment traps and toδ 34S values for water-column dissolved sulfide within a narrow zone immediately below the O 2/H 2S interface. These three sulfur reservoirs are distinctly different from the isotopic composition of ambient dissolved sulfide of the deep water column (>175 m), with δ 34S values for the deep dissolved sulfide reservoir being consistently lower by ˜2 to 4‰. These isotopic relationships suggest that iron sulfidation is occurring dominantly within a narrow, shallow region at the top of the sulfidic water mass. Isotopic data from a fine-grained turbidite collected in the deep basin and from rapidly accumulating, iron monosulfide-rich muds on the anoxic upper slope are enriched in 34S relative to the microlaminated deposits. The enrichments on the basin margin reflect a large component of iron sulfide formed during rapid burial. A broad suite of geochemical data, including sulfur isotopic results, are consistent with an upper-slope sediment source for the ubiquitous muddy turbidites of the deep basin. The collective effects of reworking, transport, and redeposition result in a complete conversion of AVS to pyrite with little additional iron sulfidation. This conclusion is supported by a detailed isotopic mass balance. The present isotopic study also

  18. Radiolaria and Global Oceanic Anoxic Event-2 in the Upper Cretaceous sections of Western Caucasus

    NASA Astrophysics Data System (ADS)

    Bragina, Liubov; Bragin, Nikita

    2010-05-01

    The Tethyan Upper Cretaceous deposits rich in organic carbon are currently regarded as indications of anoxic condition. Such sediments (predominantly black bituminous shales) are common in the Cenomanian-Turonian boundary and reflect worldwide episode of anomalous environmental conditions that has been called "Global Oceanic Anoxic Event 2" (OAE-2) (Schlanger et al., 1987). Various groups of marine organisms were influenced by this event and displayed different changes related with oxygen-poor environment. The aim of this report is to analyse changes of radiolarian assemblages during late Cenomanian - early Turonian in various Tethyan regions. Micropalaeontological investigation was carried out on a number of samples from the western part of Great Caucasus. Upper Cenomanian to lower Turonian sediments are studied in southern slope of Great Caucasus in the vicinity of Sochi and Novorossiisk. They are represented by deep-water thin-graded flysh composed of clastics and carbonates. The radiolarian assemblages of Caucasian sequences were compared to the findings of O'Dogherty (1994) from the coeval Bonarelli horizon in the Umbra-Marche Apennines, Italy. These two different palaeogeographical regions (O'Dogherty, 1994; Bragina et al., 2007) are characterized by similar radiolarian assemblages. Upper Cenomanian to lower Turonian deposits related with OAE-2 have rich content of organic matter and therefore may be recognized as important regional markers. Such marker named "Bonarelli horizon" is known in the Umbria section of central Italy (Marcucci et al., 1991). It is characterized by black bituminous shales deposited in deep-water pelagic environment together with cherts and pelagic limestones. Lithologically similar regional marker is situated in the flysh deposits of Western Caucasus (Keller, 1940; Afanasyev, 2004) and represents black shales named as "Ananur horizon". This horizon was observed in 4 sections: Volkonka and Mamedova Schel' near Sochi, and Andreevsky

  19. Early Cretaceous High Arctic Magmatism and the Oceanic Anoxic Event 1a

    NASA Astrophysics Data System (ADS)

    Planke, Sverre; Polteau, Stephane; Faleide, Jan Inge; Svensen, Henrik; Myklebust, Reidun; Midtkandal, Ivar; Corfu, Fernando

    2014-05-01

    The High Arctic Large Igneous Province (HALIP) comprises Early and Late Cretaceous igneous deposits extending from the Canadian Arctic Archipelago in the west to the east Siberian Island in the east. It also includes anomalously thick igneous crust in the Canada Basin. We have mapped out the distribution of HALIP volcanic extrusive and intrusive rocks in the Barents Sea based on field work and borehole data in Svalbard and extensive geophysical data in the offshore areas. The volcanic extrusive and intrusive rocks in the Barents Sea Large Igneous Province (BLIP) are present in a 700 000 km2 large region extending across the northern and eastern Barents Sea. The igneous complex is dominated by a large sill complex intruded into organic-rich Jurassic to Permian age sequences in the East Barents Basin, on Svalbard and on Franz Josef Land. Geochemical data suggest that the tholeiitic igneous rocks were likely formed during a short-lived melting event. New geochronology data (U/Pb on zircons) suggest that the igneous event occurred in the Early Aptian or Barremian. Marine and terrestrial Cretaceous shales and sandstones of the Carolinefjellet, Helvetiafjellet, and Rurikfjellet formations have recently been cored in four boreholes on Svalbard (the Longyearbyen CO2 Laboratory). We have completed a comprehensive analytical program of samples from the boreholes, including geochronology (Ar/Ar and zircon U/Pb), biostratigraphy (palynology), and geochemistry (ICP-MS, RockEval, TOC). In the boreholes, the Barremian-early Aptian Helvetiafjellet Formation is overlaid by early Aptian sapropel-rich shales of the Carolinefjellet Formation. Carbon isotope data reveal a negative excursion in this anoxic interval, most likely representing the Oceanic Anoxic Event 1a (OAE1a). The geochronology data suggest that the intrusive BLIP volcanism occurred at the tim e of the early Aptian OAE1a. We propose that the link between the BLIP and the OAE1a is a massive release of thermogenic methane

  20. Isotopic fractionation of dissolved ammonium at the oxygen-hydrogen sulfide interface in anoxic waters

    SciTech Connect

    Velinsky, D.J. ); Fogel, M.L.; Todd, J.F.; Tebo, B.M.

    1991-04-01

    The {delta}{sup 15}N of dissolved ammonium was determined in three anoxic marine basins: Black Sea, Saanich Inlet, B.C., Canada, and Framvaren Fjord, Norway. In each basin, the {delta}{sup 15}N-NH{sub 4{sup +}} was greatest near the O{sub 2}/H{sub 2}S interface, with {delta}{sup 15}N as high as +21{per thousand}. The depth distributions of NH{sub 4{sup +}} and {delta}{sup 15}N-NH{sub 4{sup +}} for Black Sea and Framvaren Fjord were examined with a one-dimensional, steady-state, vertical advection-diffusion model to calculate the isotope fractionation during the consumption of NH{sub 4{sup +}} by bacteria. Isotope enrichments, {var epsilon}, for Black Sea were between 5 and 15{per thousand}, whereas in Framvaren Fjord {var epsilon} ranged from 20 to 30{per thousand}. These differences are related mainly to the ambient concentration of NH{sub 4{sup +}}. Biosynthetic uptake of NH{sub 4{sup +}} rather than nitrification was responsible for the fractionation. The {delta}{sup 15}N-NH{sub 4{sup +}} in Saanich Inlet appears related to in-situ regeneration of NH{sub 4{sup +}} with little isotopic fractionation between dissolved and particulate nitrogen (PN).

  1. Witwatersrand gold deposits formed by volcanic rain, anoxic rivers and Archaean life

    NASA Astrophysics Data System (ADS)

    Heinrich, Christoph A.

    2015-03-01

    The Witwatersrand Basin in South Africa is one of the best-preserved records of fluvial sedimentation on an Archaean continent. The basin hosts the worlds biggest gold resource in thin pebble beds, but the process for gold enrichment is debated. Mechanical accumulation of gold particles from flowing river water is the prevailing hypothesis, yet there is evidence for hydrothermal mobilization of gold by fluids invading the metasedimentary rocks after their burial. Earth's atmosphere three billion years ago was oxygen free, but already sustained some of the oldest microbial life on land. Here I use thermodynamic modelling and mass-balance calculations to show that these conditions could have led to the chemical transport and precipitation of gold in anoxic surface waters, reconciling the evidence for fluvial deposition with evidence for hydrothermal-like chemical reactions. I suggest that the release of sulphurous gases from large volcanic eruptions created acid rain that enabled the dissolution and transport of gold in surface waters as sulphur complexes. Precipitation of the richest gold deposits could have been triggered by chemical reduction of the dissolved gold onto organic material in shallow lakes and pools. I conclude that the Witwatersrand gold could have formed only during the Archaean, after the emergence of continental life but before the rise of oxygen in the Earth's atmosphere.

  2. Concurrent Salinization and Development of Anoxic Conditions in a Confined Aquifer, Southern Israel.

    PubMed

    Burg, Avihu; Gavrieli, Ittai; Guttman, Joseph

    2017-03-01

    An ancient, brackish, anoxic, and relatively hot water body exists within the Yarqon-Tanninim Aquifer in southern Israel. A hydrogeological-geochemical conceptual model is presented, whereby the low water quality is the outcome of three conditions that are met simultaneously: (1) Presence of an organic-rich unit with low permeability that overlies and confines the aquifer; the confining unit contains perched horizons with relatively saline water. (2) Local phreatic/roofed conditions within the aquifer that enable seepage of the organic-rich brackish water from above. The oxidation of the dissolved organic matter in the seeping water consumes the dissolved oxygen and continues through bacterial sulfate reduction, with H2 S as a product. These exothermic reactions result in some heating. (3) The seeping water comprises a relatively large portion of the water volume. In the presented case study, the latter condition first developed in the Late Pleistocene following climate change, which led to a dramatic decline in recharge. Consequently, water flow in the local basin has nearly ceased, as evident by old water ages, specific isotopic composition, and nearly equipotential water levels. The continuous seepage from above into the almost stagnant water body has resulted in degraded water quality. Seepages of organic-rich brackish water exist at other sites throughout the aquifer but have limited impact on the salinity and redox conditions due to the dynamic water flow, which flushes the seeping water, that is, the third condition is not met. The coexistence of the above three conditions may explain the development of anoxic and saline groundwater in other aquifers worldwide.

  3. Rapid changes in the redox conditions of the western Tethys Ocean during the early Aptian oceanic anoxic event

    NASA Astrophysics Data System (ADS)

    Westermann, Stéphane; Stein, Melody; Matera, Virginie; Fiet, Nicolas; Fleitmann, Dominik; Adatte, Thierry; Föllmi, Karl B.

    2013-11-01

    The early Aptian (125 to 121 Ma) records an episode of severe environmental change including a major perturbation of the carbon cycle, an oceanic anoxic event (OAE 1a, 122.5 Ma), a platform drowning episode and a biocalcification crisis. We propose to trace changes in the oxygenation state of the ocean during the early Aptian anoxic event using the redox-sensitive trace-element (RSTE) distribution, phosphorus accumulation rates (PARs) and organic-matter characterization in three different basins of the western Tethys. The following sections have been investigated: Gorgo a Cerbara (central Italy) in the Umbria Marche basin, Glaise (SE France) in the Vocontian basin and Cassis/La Bédoule (SE France) located in the Provencal basin. In the Gorgo a Cerbara section, RSTE distributions show a low background level along the main part of the section, contrasted by different maxima in concentrations within the Selli level. In the Glaise section, the Goguel level displays a weak increase in RSTE contents coeval with moderate TOC values. At Cassis/La Bédoule, no significant RSTE enrichments have been observed in sediments equivalent to the Selli level. These differences in the records of the geochemical proxies of the Selli level or its equivalent indicate the deposition under different redox conditions, probably related to the paleogeography. Our data indicate the development of anoxic-euxinic conditions in the deeper part of the Tethys during OAE 1a, whereas in the shallower environments, conditions were less reducing. Moreover, at Gorgo a Cerbara, the Selli level is characterized by rapid changes in the intensity of reducing conditions in the water column. Ocean eutrophication seems to be a major factor in the development and the persistence of anoxia as suggested by the PAR evolution. Higher PAR values at the onset of OAE 1a suggest an increase in nutrient input, whereas the return to lower values through the first part of the OAE 1a interval may be related to the

  4. Competitive adsorption of VOCcs and BOM: Oxic and anoxic environments

    SciTech Connect

    Sorial, G.A.; Papadimas, S.P.; Suidan, M.T.; Speth, T.F.

    1994-01-01

    The effect of the presence of molecular oxygen on the adsorption of volatile organic compounds (VOCs) in distilled Milli-Q water and in water supplemented with background organic matter (BOM) is evaluated. Experiments are conducted under conditions where molecular oxygen is present in the test environment (oxic adsorption), and where oxygen is absent from the test environment (anoxic adsorption). Adsorption isotherms for tetrachloroethylene (PCE) and trichloroethylene (TCE) in Milli-Q water showed no impact of the presence of oxygen on their adsorption behavior, while adsorption isotherms for cis-1,2-dichloroethylene (DCE) showed higher capacities under toxic conditions. The Ideal Adsorbed Solution Theory (IAST) successfully predicted the VOCs anoxic adsorption isotherms in BOM. However, the IAST model did not predict the VOCs oxic adsorption isotherms in BOM.

  5. Uranium behavior in a permanently anoxic Fjord: Microbial control

    SciTech Connect

    McKee, B.A. ); Todd, J.F. )

    1993-03-01

    Uranium contamination of groundwaters resulting from U mining activities and the leakage of nuclear waste from storage facilities is a growing concern. In Framvern Fjord (southern Norway), dissolved [sup 238]U concentrations at the bacterial maximum layer (24 m), which is situated a few meters below the oxic-anoxic (i.e. oxygen-hydrogen sulfide) interface (18 m), are observed to be [approximately]60% lower than concentrations above and below this depth. Removal of U occurs well below the depth at which Fe and Mn oxyhydroxides are precipitated and under conditions inconsistent with abiological reduction of soluble U(VI) to particle-reactive U(IV). Our observations suggest that the microbial population in the anoxic waters near the O[sub 2]-H[sub 2]S interface in the fjord exerts an effective control on the aquatic biogeochemistry of U in this environment. 27 refs., 3 figs., 1 tab.

  6. The psychosocial outcomes of anoxic brain injury following cardiac arrest.

    PubMed

    Wilson, Michelle; Staniforth, Andrew; Till, Richard; das Nair, Roshan; Vesey, Patrick

    2014-06-01

    This exploratory study aimed to investigate the psychosocial outcomes for cardiac arrest survivors and explore if there is a greater impact on psychosocial outcome for individuals experiencing anoxic brain injury as a result of the cardiac arrest. Self-report measures were used to compare the quality of life, social functioning and symptoms of anxiety, depression and post-traumatic stress of individuals with and without anoxic brain injury. Secondary measures of subjective memory and executive difficulties were also used. Fifty-six participants (27 with anoxia, 29 without anoxia) took part in the study between six months and four years after experiencing cardiac arrest. A MANOVA identified a significant difference between the two groups, with the anoxia group reporting more psychosocial difficulties. They reported more social functioning difficulties and more anxiety, depression and post-traumatic stress symptoms. There was, however, no significant difference in self-reported quality of life between the two groups. As the first known study to compare psychosocial outcomes for cardiac arrest survivors experiencing anoxic brain injury with those without anoxia, the current results suggest that cardiac arrest survivors with subsequent acquired brain injury experience more psychosocial difficulties. This could be due to a combination of neuropsychological, social and psychological factors. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  7. Anoxic survival potential of bivalves: (arte)facts.

    PubMed

    de Zwaan, Albertus; Babarro, Jose M F; Monari, Marta; Cattani, Otello

    2002-03-01

    The anoxic survival time of the bivalves Chamelea gallina, Cerastoderma edule and Scapharca inaequivalvis from two different ecosystems and differing anoxia tolerances was studied in static (closed) and flow-through systems. The antibiotics chloramphenicol, penicillin and polymyxin were added, and molybdate (specific inhibitor of the process of sulfate reduction). Survival in (near) anoxic seawater of Chamelea was studied in a static system by comparing untreated seawater with autoclaved seawater and untreated clams with clams incubated in well-aerated seawater, containing the broad-spectrum antibiotic chloramphenicol, prior to the anoxic survival test. With untreated clams and natural seawater (median mortality time 2.4 days) a decrease in pH and exponential accumulation of sulfide and ammonium was observed in the anoxic medium, indicating excessive growth of (sulfate reducing) bacteria. In sterilized seawater LT50 (2.1 days) was not significantly different and again considerable amounts of ammonium and sulfide accumulated. However, pre-treatment of clams with chloramphenicol resulted in an increase of LT50 (11.0 days) by approximately fivefold. Accumulation of ammonium and sulfide was retarded, but was finally even stronger than in the medium containing untreated clams. Median mortality times were 2.5 and 2.4 days for Chamelea and 2.7 and 2.9 days for Cerastoderma for static and flow-through incubations, respectively. Addition of chloramphenicol increased strongly survival time in both systems with corresponding values of 11.0 and 16.3 days for Chamelea, and 6.4 and 6.5 days for Cerastoderma. LT50 of Scapharca in anoxic seawater was 14.4 days. Chloramphenicol and penicillin increased median survival time to 28.5 and 28.7 days, respectively, whereas polymyxin displayed no effect (LT50=13.6 days). Molybdate added to artificial sulfate free seawater blocked biotic sulfide formation, but did not improve survival time (LT50=13.7 days). Overall the results indicate

  8. Effect of anoxic decay process on simultaneous nitrification denitrification in a membrane bioreactor operated without an anoxic tank.

    PubMed

    Sarioglu, M; Insel, G; Artan, N; Orhon, D

    2010-01-01

    This study was focused on evaluating the role and the effect of anoxic decay on the extent of simultaneous nitrification-denitrification (SNdN) process sustained in a single membrane bioreactor. The membrane bioreactor was fed with relatively strong domestic sewage and operated at steady state at a sludge age of 36 days at a corresponding suspended solids level maintained in the range of 17,500-21,000 mg/L. The SNdN could be sustained due to diffusion limitation of oxygen into the flocs. The evaluation identified an MLSS threshold level of around 17,000-18,000 mg/L below which nitrogen removal was essentially controlled by denitrification and above, the rate limiting mechanism shifted to nitrification maintaining total nitrogen removal efficiency of 85-95% for a typical domestic sewage. The contribution of anoxic decay process to the overall denitrification potential was evaluated as 60%, substantially higher than the remaining 40% associated with the anoxic growth during the SNdN process.

  9. Anaerobes into heavy metal: Dissimilatory metal reduction in anoxic environments

    USGS Publications Warehouse

    Lovley, D.R.

    1993-01-01

    Within the last decade, a novel form of microbial metabolism of major environmental significance has been elucidated. In this process, known as dissimilatory metal reduction, specialized microorganisms, living in anoxic aquatic sediments and ground water, oxidize organic compounds to carbon dioxide with metals serving as the oxidant. Recent studies have demonstrated that this metabolism explains a number of important geochemical phenomena in ancient and modern sedimentary environments, affecting not only the cycling of metals but also the fate of organic matter. Furthermore, this metabolism may have practical application in remediation of environments contaminated with toxic metals and/or organics.

  10. Biogeochemical Cycle of Methanol in Anoxic Deep-Sea Sediments.

    PubMed

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

    2016-06-25

    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.

  11. Decoupling of the Carbon Cycle during Ocean Anoxic Event-2

    NASA Astrophysics Data System (ADS)

    Eldrett, J.; Bergman, S. C.; Minisini, D.

    2013-12-01

    The Cenomanian to Turonian Boundary transition (95-93 Ma) represents one of the most profound global perturbations in the carbon cycle of the last 140 million years. This interval is characterized by widespread deposition of organic-rich fine-grained sediment marked by a globally recognised positive carbon isotope excursion (CIE) reflecting the widespread removal of 12C-enriched organic matter in marine sediments under global anoxic conditions. However, the exact timing and trigger of this inferred global phenomenon, termed Oceanic Anoxic Event-2 is still debated, with recent studies showing diachroneity between the deposition of the organic-rich sediment and the CIE, and conflicting interpretations on detailed redox analyses in several of these inferred anoxic settings. Here we present the first evidence for widespread and persistent oxygenation during OAE-2 based primarily on the distribution of redox-sensitive trace metals preserved in sediments from the Eagle Ford Formation, Western Interior Seaway of North America. We generated a δ13C curve which indicates an earlier initiation of the CIE in Texas compared to the Global Stratotype and Point Section at Pueblo, Colorado. Our data also indicate anoxic-euxinic conditions in the mid-late Cenomanian, but improved bottom-water oxygenation prior to and during the CIE, corroborated by increased bioturbation, abundance of benthic foraminifera and reduced total organic carbon values. Trace metal enrichments support large volumes of mafic volcanism possibly from the High Arctic Large Igneous Province (LIP), which occur during peak bottom-water oxygenation and a plateau in δ13Corg values and does not immediately precede the Cenomanian-Turonian CIE, as previously stated. This suggests that the emplacement of a LIP was not the primary trigger of the OAE-2 event. It is also unlikely that bottom-water oxygenation was promoted by the introduction of volcanogenic Fe inhibiting sulfate reduction, as the depletion in redox

  12. Mixing between oxic and anoxic waters of the Black Sea as traced by Chernobyl cesium isotopes. (Reannouncement with new availability information). Technical report

    SciTech Connect

    Buesseler, K.O.; Livingston, H.D.; Casso, S.A.

    1991-12-31

    The Chernobyl nuclear power station accident in 1986 released readily measureable quantities of fallout 134 Cs and 137 Cs to Black Sea surface waters. This pulse-like input of tracers can be used to follow the physical mixing of the surface oxic waters, now labeled with the Chernobyl tracers, and the deeper anoxic waters, which were initially Chernobyl free. By 1988, there is clear evidence of Chernobyl Cs penetration below the oxic/anoxic interface at deep water stations in the western and eastern basins of the Black Sea. This rapid penetration of surface waters across the pycnocline cannot be explained by vertical mixing processes alone. Data from profiles at the mouth of the Bosporus suggest that significant ventilation of intermediate depths can occur as the outflowing Black Sea waters are entrained with the inflowing Mediterranean waters. forming a sub-surface water mass which is recognized by its surface water characteristics, i.e. initially a relatively high oxygen content and Chernobyl Cs signal. The lateral propagation of this signal along isopycnals into the basin interior would provide a rapid and effective mechanism for ventilating intermediate depths of the Black Sea. This process could also account for the lateral injection of resuspended margin sediments into the basin interior. The temperature and salinity data suggest that the entrainment process occurs at depths of 50-80 m, mixing waters from the Cold Intermediate Layer with the incoming, denser Mediterranean waters.

  13. The Leucine Incorporation Method Estimates Bacterial Growth Equally Well in Both Oxic and Anoxic Lake Waters

    PubMed Central

    Bastviken, David; Tranvik, Lars

    2001-01-01

    Bacterial biomass production is often estimated from incorporation of radioactively labeled leucine into protein, in both oxic and anoxic waters and sediments. However, the validity of the method in anoxic environments has so far not been tested. We compared the leucine incorporation of bacterial assemblages growing in oxic and anoxic waters from three lakes differing in nutrient and humic contents. The method was modified to avoid O2 contamination by performing the incubation in syringes. Isotope saturation levels in oxic and anoxic waters were determined, and leucine incorporation rates were compared to microscopically observed bacterial growth. Finally, we evaluated the effects of O2 contamination during incubation with leucine, as well as the potential effects of a headspace in the incubation vessel. Isotope saturation occurred at a leucine concentration of above about 50 nM in both oxic and anoxic waters from all three lakes. Leucine incorporation rates were linearly correlated to observed growth, and there was no significant difference between oxic and anoxic conditions. O2 contamination of anoxic water during 1-h incubations with leucine had no detectable impact on the incorporation rate, while a headspace in the incubation vessel caused leucine incorporation to increase in both anoxic and O2-contaminated samples. The results indicate that the leucine incorporation method relates equally to bacterial growth rates under oxic and anoxic conditions and that incubation should be performed without a headspace. PMID:11425702

  14. Marine ecosystem resilience during extreme deoxygenation: the Early Jurassic oceanic anoxic event.

    PubMed

    Caswell, Bryony A; Frid, Christopher L J

    2017-01-01

    Global warming during the Early Jurassic, and associated widespread ocean deoxygenation, was comparable in scale with the changes projected for the next century. This study quantifies the impact of severe global environmental change on the biological traits of marine communities that define the ecological roles and functions they deliver. We document centennial-millennial variability in the biological trait composition of Early Jurassic (Toarcian) seafloor communities and examine how this changed during the event using biological traits analysis. Environmental changes preceding the global oceanic anoxic event (OAE) produced an ecological shift leading to stressed benthic palaeocommunities with reduced resilience to the subsequent OAE. Changes in traits and ecological succession coincided with major environmental changes; and were of similar nature and magnitude to those in severely deoxygenated benthic communities today despite the very different timescales. Changes in community composition were linked to local redox conditions whereas changes in populations of opportunists were driven by primary productivity. Throughout most of the OAE substitutions by tolerant taxa conserved the trait composition and hence functioning, but periods of severe deoxygenation caused benthic defaunation that would have resulted in functional collapse. Following the OAE recovery was slow probably because the global nature of the event restricted opportunities for recruitment from outside the basin. Our findings suggest that future systems undergoing deoxygenation may initially show functional resilience, but severe global deoxygenation will impact traits and ecosystem functioning and, by limiting the species pool, will slow recovery rates.

  15. H2 cycling and microbial bioenergetics in anoxic sediments

    NASA Technical Reports Server (NTRS)

    Hoehler, Tori M.; DeVincenzi, Donald (Technical Monitor)

    2001-01-01

    The simple biochemistry of H2 is central to a large number of microbial processes, affecting the interaction of organisms with each other and with the environment. In anoxic sediments, the great majority of microbial redox processes involve H2 as a reactant, product, or potential by-product, and the thermodynamics of these processes are thus highly sensitive to fluctuations in environmental H2 concentrations. In turn, H2 concentrations are controlled by the activity of H2-consuming microorganisms, which efficiently utilize this substrate down to levels which correspond to their bioenergetic limitations. Consequently, any environmental change which impacts the thermodynamics of H2-consuming organisms is mirrored by a corresponding change in H2 concentrations. This phenomenon is illustrated in anoxic sediments from Cape Lookout Bight, NC, USA: H2 concentrations are controlled by a suite of environmental parameters (e.g., temperature, sulfate concentrations) in a fashion which can be quantitatively described by a simple thermodynamic model. These findings allow us to calculate the apparent minimum quantity of biologically useful energy in situ. We find that sulfate reducing bacteria are not active at energy yields below -18 kJ per mole sulfate, while methanogenic archaea exhibit a minimum close to -10 kJ per mole methane.

  16. Microbiological reduction of Sb(V) in anoxic freshwater sediments

    USGS Publications Warehouse

    Oremland, Ronald S.; Kulp, Thomas R.; Miller, Laurence G.; Braiotta, Franco; Webb, Samuel M.; Kocar, Benjamin D; Blum, Jodi S.

    2014-01-01

    Microbiological reduction of millimolar concentrations of Sb(V) to Sb(III) was observed in anoxic sediments from two freshwater settings: (1) a Sb- and As-contaminated mine site (Stibnite Mine) in central Idaho and 2) an uncontaminated suburban lake (Searsville Lake) in the San Francisco Bay Area. Rates of Sb(V) reduction in anoxic sediment microcosms and enrichment cultures were enhanced by amendment with lactate or acetate as electron donors but not by H2, and no reduction occurred in sterilized controls. Addition of 2-14C-acetate to Stibnite Mine microcosms resulted in the production of 14CO2 coupled to Sb(V) reduction, suggesting that this process proceeds by a dissimilatory respiratory pathway in those sediments. Antimony(V) reduction in Searsville Lake sediments was not coupled to acetate mineralization and may be associated with Sb-resistance. The microcosms and enrichment cultures also reduced sulfate, and the precipitation of insoluble Sb(III)-sulfide complexes was a major sink for reduced Sb. The reduction of Sb(V) by Stibnite Mine sediments was inhibited by As(V), suggesting that As(V) is a preferred electron acceptor for the indigenous community. These findings indicate a novel pathway for anaerobic microbiological respiration and suggest that communities capable of reducing high concentrations of Sb(V) commonly occur naturally in the environment.

  17. Microbiological reduction of Sb(V) in anoxic freshwater sediments

    USGS Publications Warehouse

    Oremland, Ronald S.; Kulp, Thomas R.; Miller, Laurence G.; Braiotta, Franco; Webb, Samuel M.; Kocar, Benjamin D; Blum, Jodi S.

    2013-01-01

    Microbiological reduction of millimolar concentrations of Sb(V) to Sb(III) was observed in anoxic sediments from two freshwater settings: (1) a Sb- and As-contaminated mine site (Stibnite Mine) in central Idaho and 2) an uncontaminated suburban lake (Searsville Lake) in the San Francisco Bay Area. Rates of Sb(V) reduction in anoxic sediment microcosms and enrichment cultures were enhanced by amendment with lactate or acetate as electron donors but not by H2, and no reduction occurred in sterilized controls. Addition of 2-14C-acetate to Stibnite Mine microcosms resulted in the production of 14CO2 coupled to Sb(V) reduction, suggesting that this process proceeds by a dissimilatory respiratory pathway in those sediments. Antimony(V) reduction in Searsville Lake sediments was not coupled to acetate mineralization and may be associated with Sb-resistance. The microcosms and enrichment cultures also reduced sulfate, and the precipitation of insoluble Sb(III)-sulfide complexes was a major sink for reduced Sb. The reduction of Sb(V) by Stibnite Mine sediments was inhibited by As(V), suggesting that As(V) is a preferred electron acceptor for the indigenous community. These findings indicate a novel pathway for anaerobic microbiological respiration and suggest that communities capable of reducing high concentrations of Sb(V) commonly occur naturally in the environment.

  18. Diatoms respire nitrate to survive dark and anoxic conditions.

    PubMed

    Kamp, Anja; de Beer, Dirk; Nitsch, Jana L; Lavik, Gaute; Stief, Peter

    2011-04-05

    Diatoms survive in dark, anoxic sediment layers for months to decades. Our investigation reveals a correlation between the dark survival potential of marine diatoms and their ability to accumulate NO(3)(-) intracellularly. Axenic strains of benthic and pelagic diatoms that stored 11-274 mM NO(3)(-) in their cells survived for 6-28 wk. After sudden shifts to dark, anoxic conditions, the benthic diatom Amphora coffeaeformis consumed 84-87% of its intracellular NO(3)(-) pool within 1 d. A stable-isotope labeling experiment proved that (15)NO(3)(-) consumption was accompanied by the production and release of (15)NH(4)(+), indicating dissimilatory nitrate reduction to ammonium (DNRA). DNRA is an anaerobic respiration process that is known mainly from prokaryotic organisms, and here shown as dissimilatory nitrate reduction pathway used by a eukaryotic phototroph. Similar to large sulfur bacteria and benthic foraminifera, diatoms may respire intracellular NO(3)(-) in sediment layers without O(2) and NO(3)(-). The rapid depletion of the intracellular NO(3)(-) storage, however, implies that diatoms use DNRA to enter a resting stage for long-term survival. Assuming that pelagic diatoms are also capable of DNRA, senescing diatoms that sink through oxygen-deficient water layers may be a significant NH(4)(+) source for anammox, the prevalent nitrogen loss pathway of oceanic oxygen minimum zones.

  19. Diatoms respire nitrate to survive dark and anoxic conditions

    PubMed Central

    Kamp, Anja; de Beer, Dirk; Nitsch, Jana L.; Lavik, Gaute; Stief, Peter

    2011-01-01

    Diatoms survive in dark, anoxic sediment layers for months to decades. Our investigation reveals a correlation between the dark survival potential of marine diatoms and their ability to accumulate NO3− intracellularly. Axenic strains of benthic and pelagic diatoms that stored 11–274 mM NO3− in their cells survived for 6–28 wk. After sudden shifts to dark, anoxic conditions, the benthic diatom Amphora coffeaeformis consumed 84–87% of its intracellular NO3− pool within 1 d. A stable-isotope labeling experiment proved that 15NO3− consumption was accompanied by the production and release of 15NH4+, indicating dissimilatory nitrate reduction to ammonium (DNRA). DNRA is an anaerobic respiration process that is known mainly from prokaryotic organisms, and here shown as dissimilatory nitrate reduction pathway used by a eukaryotic phototroph. Similar to large sulfur bacteria and benthic foraminifera, diatoms may respire intracellular NO3− in sediment layers without O2 and NO3−. The rapid depletion of the intracellular NO3− storage, however, implies that diatoms use DNRA to enter a resting stage for long-term survival. Assuming that pelagic diatoms are also capable of DNRA, senescing diatoms that sink through oxygen-deficient water layers may be a significant NH4+ source for anammox, the prevalent nitrogen loss pathway of oceanic oxygen minimum zones. PMID:21402908

  20. Anaerobic animals from an ancient, anoxic ecological niche

    PubMed Central

    2010-01-01

    Tiny marine animals that complete their life cycle in the total absence of light and oxygen are reported by Roberto Danovaro and colleagues in this issue of BMC Biology. These fascinating animals are new members of the phylum Loricifera and possess mitochondria that in electron micrographs look very much like hydrogenosomes, the H2-producing mitochondria found among several unicellular eukaryotic lineages. The discovery of metazoan life in a permanently anoxic and sulphidic environment provides a glimpse of what a good part of Earth's past ecology might have been like in 'Canfield oceans', before the rise of deep marine oxygen levels and the appearance of the first large animals in the fossil record roughly 550-600 million years ago. The findings underscore the evolutionary significance of anaerobic deep sea environments and the anaerobic lifestyle among mitochondrion-bearing cells. They also testify that a fuller understanding of eukaryotic and metazoan evolution will come from the study of modern anoxic and hypoxic habitats. PMID:20370917

  1. Degradation of triclosan under aerobic, anoxic, and anaerobic conditions.

    PubMed

    Gangadharan Puthiya Veetil, Prajeesh; Vijaya Nadaraja, Anupama; Bhasi, Arya; Khan, Sudheer; Bhaskaran, Krishnakumar

    2012-07-01

    Triclosan (2, 4, 4'-trichloro-2'-hydroxyl diphenyl ether) is a broad-spectrum antimicrobial agent present in a number of house hold consumables. Aerobic and anaerobic enrichment cultures tolerating triclosan were developed and 77 bacterial strains tolerating triclosan at different levels were isolated from different inoculum sources. Biodegradation of triclosan under aerobic, anoxic (denitrifying and sulphate reducing conditions), and anaerobic conditions was studied in batch cultures with isolated pure strains and enrichment consortium developed. Under aerobic conditions, the isolated strains tolerated triclosan up to 1 g/L and degraded the compound in inorganic-mineral-broth and agar media. At 10 mg/L level triclosan, 95 ± 1.2% was degraded in 5 days, producing phenol, catechol and 2, 4-dichlorophenol as the degradation products. The strains were able to metabolize triclosan and its degradation products in the presence of monooxygenase inhibitor 1-pentyne. Under anoxic/anaerobic conditions highest degradation (87%) was observed in methanogenic system with acetate as co-substrate and phenol, catechol, and 2, 4-dichlorophenol were among the products. Three of the isolated strains tolerating 1 g/L triclosan were identified as Pseudomonas sp. (BDC 1, 2, and 3).

  2. Microbiological reduction of Sb(V) in anoxic freshwater sediments.

    PubMed

    Kulp, Thomas R; Miller, Laurence G; Braiotta, Franco; Webb, Samuel M; Kocar, Benjamin D; Blum, Jodi S; Oremland, Ronald S

    2014-01-01

    Microbiological reduction of millimolar concentrations of Sb(V) to Sb(III) was observed in anoxic sediments from two freshwater settings: (1) a Sb- and As-contaminated mine site (Stibnite Mine) in central Idaho and 2) an uncontaminated suburban lake (Searsville Lake) in the San Francisco Bay Area. Rates of Sb(V) reduction in anoxic sediment microcosms and enrichment cultures were enhanced by amendment with lactate or acetate as electron donors but not by H2, and no reduction occurred in sterilized controls. Addition of 2-(14)C-acetate to Stibnite Mine microcosms resulted in the production of (14)CO2 coupled to Sb(V) reduction, suggesting that this process proceeds by a dissimilatory respiratory pathway in those sediments. Antimony(V) reduction in Searsville Lake sediments was not coupled to acetate mineralization and may be associated with Sb-resistance. The microcosms and enrichment cultures also reduced sulfate, and the precipitation of insoluble Sb(III)-sulfide complexes was a major sink for reduced Sb. The reduction of Sb(V) by Stibnite Mine sediments was inhibited by As(V), suggesting that As(V) is a preferred electron acceptor for the indigenous community. These findings indicate a novel pathway for anaerobic microbiological respiration and suggest that communities capable of reducing high concentrations of Sb(V) commonly occur naturally in the environment.

  3. Biotransformation potential of phytosterols under anoxic and anaerobic conditions.

    PubMed

    Dykstra, C M; Giles, H D; Banerjee, S; Pavlostathis, S G

    2014-01-01

    The biotransformation potential of three phytosterols (campesterol, stigmasterol and β-sitosterol) under denitrifying, sulfate-reducing and fermentative/methanogenic conditions was assessed. Using a group contribution method, the standard Gibbs free energy of phytosterols was calculated and used to perform theoretical energetic calculations. The oxidation of phytosterols under aerobic, nitrate-reducing, sulfate-reducing and methanogenic conditions was determined to be energetically feasible. However, using semi-continuously fed cultures maintained at 20-22 °C over 16 weekly feeding cycles (112 days; retention time, 21 days), phytosterol removal was observed under nitrate-reducing and sulfate-reducing conditions, but not under fermentative/methanogenic conditions. Under sulfate-reducing conditions, stigmast-4-en-3-one was identified as an intermediate of phytosterol biotransformation, a reaction more likely carried out by dehydrogenases/isomerases, previously reported to act on cholesterol under both oxic and anoxic (denitrifying) conditions. Further study of the biotransformation of phytosterols under anoxic/anaerobic conditions is necessary to delineate the factors and conditions leading to enhanced phytosterol biodegradation and the development of effective biological treatment systems for the removal of phytosterols from pulp and paper wastewaters and other phytosterol-bearing waste streams.

  4. H2 cycling and microbial bioenergetics in anoxic sediments

    NASA Technical Reports Server (NTRS)

    Hoehler, Tori M.; DeVincenzi, Donald (Technical Monitor)

    2001-01-01

    The simple biochemistry of H2 is central to a large number of microbial processes, affecting the interaction of organisms with each other and with the environment. In anoxic sediments, the great majority of microbial redox processes involve H2 as a reactant, product, or potential by-product, and the thermodynamics of these processes are thus highly sensitive to fluctuations in environmental H2 concentrations. In turn, H2 concentrations are controlled by the activity of H2-consuming microorganisms, which efficiently utilize this substrate down to levels which correspond to their bioenergetic limitations. Consequently, any environmental change which impacts the thermodynamics of H2-consuming organisms is mirrored by a corresponding change in H2 concentrations. This phenomenon is illustrated in anoxic sediments from Cape Lookout Bight, NC, USA: H2 concentrations are controlled by a suite of environmental parameters (e.g., temperature, sulfate concentrations) in a fashion which can be quantitatively described by a simple thermodynamic model. These findings allow us to calculate the apparent minimum quantity of biologically useful energy in situ. We find that sulfate reducing bacteria are not active at energy yields below -18 kJ per mole sulfate, while methanogenic archaea exhibit a minimum close to -10 kJ per mole methane.

  5. Kinetic and stoichiometric characterization of anoxic sulfide oxidation by SO-NR mixed cultures from anoxic biotrickling filters.

    PubMed

    Mora, Mabel; Fernández, Maikel; Gómez, José Manuel; Cantero, Domingo; Lafuente, Javier; Gamisans, Xavier; Gabriel, David

    2015-01-01

    Monitoring the biological activity in biotrickling filters is difficult since it implies estimating biomass concentration and its growth yield, which can hardly be measured in immobilized biomass systems. In this study, the characterization of a sulfide-oxidizing nitrate-reducing biomass obtained from an anoxic biotrickling filter was performed through the application of respirometric and titrimetric techniques. Previously, the biomass was maintained in a continuous stirred tank reactor under steady-state conditions resulting in a growth yield of 0.328 ± 0.045 g VSS/g S. To properly assess biological activity in respirometric tests, abiotic assays were conducted to characterize the stripping of CO2 and sulfide. The global mass transfer coefficient for both processes was estimated. Subsequently, different respirometric tests were performed: (1) to solve the stoichiometry related to the autotrophic denitrification of sulfide using either nitrate or nitrite as electron acceptors, (2) to evaluate the inhibition caused by nitrite and sulfide on sulfide oxidation, and (3) to propose, calibrate, and validate a kinetic model considering both electron acceptors in the overall anoxic biodesulfurization process. The kinetic model considered a Haldane-type equation to describe sulfide and nitrite inhibitions, a non-competitive inhibition to reflect the effect of sulfide on the elemental sulfur oxidation besides single-step denitrification since no nitrite was produced during the biological assays.

  6. Seismically triggered turbidites in small margin basins: Alfonso Basin, Western Gulf of California and Santa Monica Basin, California Borderland

    NASA Astrophysics Data System (ADS)

    Gorsline, D. S.; De Diego, T.; Nava-Sanchez, E. H.

    2000-09-01

    Box cores and gravity cores collected in Santa Monica Basin, California Continental Borderland, and in Alfonso Basin, western Gulf of California, contain turbidites, some of which can be traced over much of the respective basin floors. In Santa Monica Basin, at least six of these basin-wide flows have been deposited over the past four to five centuries. In Alfonso Basin, 9-10 basin-wide turbidites have been deposited over the past few millenia. Both Santa Monica and Alfonso Basins have anoxic conditions over the deep basin floors, which inhibit bioturbation and preserve primary laminations. These deposits have been dated using the 210Pb and AMS 14C methods, and varve counting so it is therefore possible to date the turbidites. Those that were deposited during historic time can be matched with major floods or earthquakes in the region. In Santa Monica Basin, turbidity currents can be generated directly from decadal major flood discharges, or by centennial slope failures triggered by major earthquake shocks. The flood-generated turbidites are typically a fifth or less of the volume of the earthquake-generated turbidites. In Alfonso Basin, the tributary coastal canyon discharges are small and have a high proportion of coarse-grained sand, which is trapped on the shelves, and cannot directly supply turbidite volumes of basin-wide magnitude. Thus the turbidites seen in that basin floor are probably produced by slope failures of silty clay deposits which were seismically generated. The distribution of the dated turbidites, and a slip face in one box core from the landward slope, indicates a source on the landward depositional slope of the fault-bounded basin. Similar discontinuities of the same age have been reported on the eastern side of the Gulf in the Guaymas area. In ancient basins, the criteria that may distinguish seismo-turbidites are areal extent and volume where those factors can be estimated. Basin-wide turbidites are probably seismically triggered. If

  7. Records of past mid-depth ventilation: Cretaceous ocean anoxic event 2 vs. Recent oxygen minimum zones

    NASA Astrophysics Data System (ADS)

    Schönfeld, J.; Kuhnt, W.; Erdem, Z.; Flögel, S.; Glock, N.; Aquit, M.; Frank, M.; Holbourn, A.

    2015-02-01

    Present day oceans are well ventilated, with the exception of mid-depth oxygen minimum zones (OMZs) under high surface water productivity, regions of sluggish circulation, and restricted marginal basins. In the Mesozoic, however, entire oceanic basins transiently became dysoxic or anoxic. The Cretaceous ocean anoxic events (OAEs) were characterised by laminated organic-carbon rich shales and low-oxygen indicating trace fossils preserved in the sedimentary record. Yet assessments of the intensity and extent of Cretaceous near-bottom water oxygenation have been hampered by deep or long-term diagenesis and the evolution of marine biota serving as oxygen indicators in today's ocean. Sedimentary features similar to those found in Cretaceous strata were observed in deposits underlying Recent OMZs, where bottom-water oxygen levels, the flux of organic matter, and benthic life have been studied thoroughly. Their implications for constraining past bottom-water oxygenation are addressed in this review. We compared OMZ sediments from the Peruvian upwelling with deposits of the late Cenomanian OAE 2 from the north-west African shelf. Holocene laminated sediments are encountered at bottom-water oxygen levels of < 7 μmol kg-1 under the Peruvian upwelling and < 5 μmol kg-1 in California Borderland basins and the Pakistan Margin. Seasonal to decadal changes of sediment input are necessary to create laminae of different composition. However, bottom currents may shape similar textures that are difficult to discern from primary seasonal laminae. The millimetre-sized trace fossil Chondrites was commonly found in Cretaceous strata and Recent oxygen-depleted environments where its diameter increased with oxygen levels from 5 to 45 μmol kg-1. Chondrites has not been reported in Peruvian sediments but centimetre-sized crab burrows appeared around 10 μmol kg-1, which may indicate a minimum oxygen value for bioturbated Cretaceous strata. Organic carbon accumulation

  8. Influence of different anoxic time exposures on active biomass, protozoa and filamentous bacteria in activated sludge.

    PubMed

    Rodriguez-Perez, S; Fermoso, F G; Arnaiz, C

    Medium-sized wastewater treatment plants are considered too small to implement anaerobic digestion technologies and too large for extensive treatments. A promising option as a sewage sludge reduction method is the inclusion of anoxic time exposures. In the present study, three different anoxic time exposures of 12, 6 and 4 hours have been studied to reduce sewage sludge production. The best anoxic time exposure was observed under anoxic/oxic cycles of 6 hours, which reduced 29.63% of the biomass production compared with the oxic control conditions. The sludge under different anoxic time exposures, even with a lower active biomass concentration than the oxic control conditions, showed a much higher metabolic activity than the oxic control conditions. Microbiological results suggested that both protozoa density and abundance of filamentous bacteria decrease under anoxic time exposures compared to oxic control conditions. The anoxic time exposures 6/6 showed the highest reduction in both protozoa density, 37.5%, and abundance of filamentous bacteria, 41.1%, in comparison to the oxic control conditions. The groups of crawling ciliates, carnivorous ciliates and filamentous bacteria were highly influenced by the anoxic time exposures. Protozoa density and abundance of filamentous bacteria have been shown as promising bioindicators of biomass production reduction.

  9. Superoxide metabolism is correlated to the post-anoxic injury of soybean (Glycine max) roots

    SciTech Connect

    Bolles, C.S.; Van Toai, T.T. )

    1990-05-01

    Post-anoxic injury of root tips of soybean seedlings is more severe following a very short (1 hour) period of anoxia than a longer (3-5 hour) period. Anaerobic incubation of root tips in the presence of 100 mM ascorbate, an antioxidant and free-radical-scavenging compound, alleviates the detrimental post-anoxia effects of a very short anoxic treatment. Extracts of root tips which have been treated anoxically for 1 hour have an elevated capacity to produce superoxide anions when subsequently exposed to air, than extracts from seedlings treated anoxically for longer time. Changes in superoxide dismutase (SOD) enzyme activity and SOD-specific RNA sequences will be presented. The results support that post-anoxic injury occurs in soybean roots and that SOD plays a role in the detoxification of superoxide anions.

  10. Transformation of Monoaromatic hydrocarbons to organic acids in anoxic groundwater environment

    USGS Publications Warehouse

    Cozzarelli, I.M.; Eganhouse, R.P.; Baedecker, M.J.

    1990-01-01

    The transformation of benzene and a series of alkylbenzenes was studied in anoxic groundwater of a shallow glacial-outwash aquifer near Bemidji, Minnesota, U.S.A. Monoaromatic hydrocarbons, the most water-soluble components of crude oil, were transported downgradient of an oil spill, forming a plume of contaminated groundwater. Organic acids that were not original components of the oil were identified in the anoxic groundwater. The highest concentrations of these oxidized organic compounds were found in the anoxic plume where a decrease in concentrations of structurally related alkylbenzenes was observed. These results suggest that biological transformation of benzene and alkylbenzenes to organic acid intermediates may be an important attenuation process in anoxic environments. The transformation of a complex mixture of hydrocarbons to a series of corresponding oxidation products in an anoxic subsurface environment provides new insight into in situ anaerobic degradation processes. ?? 1990 Springer-Verlag New York Inc.

  11. Integrated stratigraphy of the Cenomanian-Turonian boundary interval: improving understanding of Oceanic Anoxic Events

    NASA Astrophysics Data System (ADS)

    Jarvis, Ian

    2014-05-01

    The Cenomanian-Turonian boundary (CTB) interval ~ 94 Ma represented a period of major global palaeoenvironmental change. Increasingly detailed multidisciplinary studies integrating sedimentological, palaeontological and geochemical data from multiple basins, are enabling the development of refined but complex models that aid understanding of the mechanisms driving changes in ocean productivity and climate. This paper reviews some of the exciting new developments in this field. Facies change characterizes the CTB interval in most areas. In the Chalk seas of northern Europe, a widespead hiatus was followed by the deposition of clay-rich organic-lean beds of the Plenus Marl and its equivalents, and then nodular chalks. In the North Sea basin and its onshore extension in eastern England and northern Germany, black shales of the Black Band (Blodøks Formation, Hasseltal Formation) occur. Similarly, in northern Tethys, a brief interval of black shale accumulation within a predominantly carbonate succession, is exemplified by the Niveau Thomel in the Vocontian Basin (SE France), and the Livello Bonarelli in Italy. Widespread deposition of organic-rich marine sediments during CTB times led to 12C depletion in surface carbon reservoirs (oceans, atmosphere, biosphere), and a large positive global δ13C excursion preserved in marine carbonates and both marine and terrestrial organic matter (Oceanic Anoxic Event 2). Significant biotic turnover characterises the boundary interval, and inter-regional correlation may be achieved at high resolution using integrated biostratigraphy employing macrofossils (ammonites, inoceramid bivalves), microfossils (planktonic foraminifera, dinoflagellate cysts) and calcareous nannofossils. Correlations can be tested against those based on comparison of δ13C profiles - carbon isotope chemostratigraphy, supplemented by oxygen isotope and elemental data. Interpretation of paired carbonate - organic matter δ13C data from multiple CTB sections

  12. Bruxism Associated with Anoxic Encephalopathy: Successful Treatment with Baclofen

    PubMed Central

    Janati, A. Bruce; ALGhasab, Naif Saad; ALGhassab, Fahad Saad

    2013-01-01

    Introduction. Bruxism is a movement disorder characterized by grinding and clenching of the teeth. Etiology of bruxism can be divided into three groups: psychosocial factors, peripheral factors, and pathophysiological factors. Methods. The clinical investigation was conducted at King Khaled Hospital in Hail, Saudi Arabia, in 2012. Results. A 16-year-old Saudi female was brought to the hospital in a comatose state and with generalized convulsive seizures secondary to acute anoxic encephalopathy. In the third week of hospitalization, while still in a state of akinetic mutism, she developed incessant bruxism which responded favorably to a GABA receptor agonist (baclofen). Conclusion. Our data support the hypothesis that bruxism emanates from imbalance or dysregulation of the neurotransmitter system. Larger scale studies will be needed to confirm this hypothesis. PMID:24455317

  13. Spatiometabolic stratification of anoxic biofilm in prototype bioelectrogenic system.

    PubMed

    Mohanakrishna, G; Butti, Sai Kishore; Kannaiah Goud, R; Venkata Mohan, S

    2017-06-01

    A prototype bio-catalyzed electrogenic system integrated with a biological treatment process (SBR-BET) was evaluated to study specific function of anoxic condition on the electrogenic activity. A multiphasic approach was employed, where the influence of DO on bio-electrogenic activity was optimized initially, later optimal anode to cathode inter-electrode distance was enumerated. Amongst the four electrode distances evaluated, 2cm showed higher power output. Bioelectrokinetics analysis was used to validate the system performance with the experimental variation studied. The redox behavior showed an increase in cathodic catalytic activity with an increase in the inter-electrode distance. Spatiometabolic distribution depicted the microbial stratification on the anode. Electrochemically active bacteria present on the anode surface (inner and outer layers of biofilms) showed relatively uniform diversity compared with the suspension culture. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Stabilization of lysosomes in anoxic myocardium by propranolol.

    PubMed Central

    Welman, E

    1979-01-01

    1. Isolated hearts of guinea-pigs were perfused aerobically and anoxically for 60 min. (+/-)-Propranolol was added to the perfusion medium in concentrations ranging from 10 ng to 10 microgram/ml. 2. Lysosome stability was assessed by measurements of latent acid hydrolase activity in homogenates of left ventricular tissue. 3. In the absence of propranolol, the integrity of the myocardial lysosomes was considerably reduced after 60 min anoxia. Lysosome stability was enhanced by the presence of (+/-)-propranolol. The optimal concentration was found to be 0.1 microgram/ml. This concentration of the (+)-isomer alone was less effective. 4. It was concluded that beta-adrenoceptor blockade was the major mechanism by which lysosome disruption was prevented but that some direct membrane effect of propranolol may also be involved. PMID:427322

  15. Denitrification kinetics in anoxic/aerobic activated sludge systems

    SciTech Connect

    Horne, G.M.

    1998-12-11

    Nitrogen removal needs at municipal wastewater treatment plants (WWTPs) have increased due to greater concerns about eutrophication and increased interest in reuse of treated municipal effluents. Biological processes are the most cost-effective method for nitrogen removal. Biological nitrogen removal is accomplished in two distinctly different processes by the conversion of nitrogen in the wastewater from organic nitrogen and ammonia to nitrate, followed by reduction of the nitrate to nitrogen gas. Nitrate production occurs in an aerobic activated sludge treatment zone during a process called nitrification. The nitrate is then converted through a series of intermediate steps to nitrogen gas in an anoxic zone (an anaerobic condition with nitrate present) during a process called denitrification, effectively removing the nitrogen from the wastewater. Many different WWTP designs have been developed to incorporate these two conditions for nitrogen removal.

  16. Oxygen intrusion into anoxic fjords leads to increased methylmercury availability

    NASA Astrophysics Data System (ADS)

    Veiteberg Braaten, Hans Fredrik; Pakhomova, Svetlana; Yakushev, Evgeniy

    2013-04-01

    Mercury (Hg) appears in the oxic surface waters of the oceans at low levels (sub ng/L). Because inorganic Hg can be methylated into the toxic and bioaccumulative specie methylmercury (MeHg) levels can be high at the top of the marine food chain. Even though marine sea food is considered the main risk driver for MeHg exposure to people most research up to date has focused on Hg methylation processes in freshwater systems. This study identifies the mechanisms driving formation of MeHg during oxygen depletion in fjords, and shows how MeHg is made available in the surface water during oxygen intrusion. Studies of the biogeochemical structure in the water column of the Norwegian fjord Hunnbunn were performed in 2009, 2011 and 2012. In autumn of 2011 mixing flushing events were observed and lead to both positive and negative effects on the ecosystem state in the fjord. The oxygenated water intrusions lead to a decrease of the deep layer concentrations of hydrogen sulfide (H2S), ammonia and phosphate. On the other hand the intrusion also raised the H2S boundary from 8 m to a shallower depth of just 4 m. Following the intrusion was also observed an increase at shallower depths of nutrients combined with a decrease of pH. Before flushing events were observed concentrations of total Hg (TotHg) increased from 1.3 - 1.7 ng/L in the surface layer of the fjord to concentrations ranging from 5.2 ng/L to 6.4 ng/L in the anoxic zone. MeHg increased regularly from 0.04 ng/L in the surface water to a maximum concentration of 5.2 ng/L in the deeper layers. This corresponds to an amount of TotHg present as MeHg ranging from 2.1 % to 99 %. The higher concentrations of MeHg in the deeper layer corresponds to an area where no oxygen is present and concentrations of H2S exceeds 500 µM, suggesting a production of MeHg in the anoxic area as a result of sulphate reducing bacteria activity. After flushing the concentrations of TotHg showed a similar pattern ranging from 0.6 ng/L in the

  17. Cr Isotope Response to Ocean Anoxic Event 2

    NASA Astrophysics Data System (ADS)

    Holmden, C. E.; Jacobson, A. D.; Sageman, B. B.; Hurtgen, M.

    2015-12-01

    The element Cr offers a redox sensitive isotopic proxy with potential for tracing past oxygen levels in the oceans. We examine this potential in a marine carbonate section deposited during Cretaceous Ocean Anoxic Event 2 (OAE 2) in the Western Interior Seaway, Colorado. Redox changes are the main source of Cr isotope fractionation in Earth surface environments. Cr(VI), in the form of the chromate oxyanion, is the thermodynamically favoured species in oxygenated seawater. Reduction of Cr(VI) causes light isotopes to partition into Cr(III), which is reactive and susceptible to removal into marine sediment. Therefore, widespread ocean anoxia should correlate with positive shifts in seawater chromate Cr isotope values (δ53Cr), assuming that all Cr input fluxes remained constant during the event. We find instead that inferred seawater δ53Cr values decreased during OAE 2. The minima of the sedimentary δ53Cr excursion coincides with the peak interval of anomalously enriched concentrations of Cr and other trace metals of basaltic affinity attributed to eruption of the Caribbean Large Igneous Province (CLIP). We propose that an anoxic, hydrothermal plume enriched in Cr(III) with low δ53Cr values characteristic of igneous rocks moved from deep waters of the CLIP eruption site in the eastern Pacific into deep waters of the proto-North Atlantic through an oceanic gateway in the Central Americas. Once inside, metal-rich waters upwelled against the surrounding continental margins. CLIP volcanism delivered a submarine weathering flux of Cr to the oceans during OAE 2 that was large enough to mask the expected isotopic response of the ocean Cr cycle to increasing anoxia, particularly in the proto-North Atlantic Ocean.

  18. Organomineral nanocomposite carbon burial during Oceanic Anoxic Event 2

    NASA Astrophysics Data System (ADS)

    Löhr, S. C.; Kennedy, M. J.

    2014-05-01

    Organic carbon (OC) enrichment in sediments deposited during Oceanic Anoxic Events (OAEs) is commonly attributed to elevated productivity and marine anoxia. We find that OC enrichment in the late Cenomanian aged OAE2 at Demerara Rise was controlled by co-occurrence of anoxic bottom-water, sufficient productivity to saturate available mineral surfaces and variable deposition of high surface area detrital smectite clay. Redox indicators show consistently oxygen-depleted conditions, while a strong correlation between OC concentration and sediment mineral surface area (R2=0.92) occurs across a range of TOC values from 9-33%. X-ray diffraction data indicates intercalation of OC in smectite interlayers while electron, synchrotron infrared and X-ray microscopy show an intimate association between clay minerals and OC, consistent with preservation of OC as organomineral nanocomposites and aggregates rather than discrete, μm-scale pelagic detritus. Since the consistent ratio between TOC and mineral surface area suggests that excess OC relative to surface area is lost, we propose that it is the varying supply of smectite that best explains variable organic enrichment against a backdrop of continuous anoxia, which is conducive to generally high TOC during OAE2 at Demerara Rise. Smectitic clays are unique in their ability to form stable organomineral nanocomposites and aggregates that preserve organic matter, and are common weathering products of continental volcanic deposits. An increased flux of smectite coinciding with high carbon burial is consistent with evidence for widespread volcanism during OAE2, so that organomineral carbon burial may represent a potential feedback to volcanic degassing of CO2.

  19. Organomineral nanocomposite carbon burial during Oceanic Anoxic Event 2

    NASA Astrophysics Data System (ADS)

    Löhr, S. C.; Kennedy, M. J.

    2014-09-01

    Organic carbon (OC) enrichment in sediments deposited during Oceanic Anoxic Events (OAEs) is commonly attributed to elevated productivity and marine anoxia. We find that OC enrichment in the late Cenomanian aged OAE 2 at the Demerara Rise was controlled by the co-occurrence of anoxic bottom water, sufficient productivity to saturate available mineral surfaces, and variable deposition of high surface area detrital smectite clay. Redox indicators show consistently oxygen-depleted conditions, while a strong correlation between OC concentration and sediment mineral surface area (R2 = 0.92) occurs across a range of total organic carbon (TOC) values from 9 to 33%. X-ray diffraction data indicate the intercalation of OC in smectite interlayers, while electron, synchrotron infrared and X-ray microscopy show an intimate association between clay minerals and OC, consistent with preservation of OC as organomineral nanocomposites and aggregates rather than discrete, μm-scale pelagic detritus. Since the consistent ratio between TOC and mineral surface area suggests that excess OC relative to surface area is lost, we propose that it is the varying supply of smectite that best explains variable organic enrichment against a backdrop of continuous anoxia, which is conducive to generally high TOC during OAE 2 at the Demerara Rise. Smectitic clays are unique in their ability to form stable organomineral nanocomposites and aggregates that preserve organic matter, and are common weathering products of continental volcanic deposits. An increased flux of smectite coinciding with high carbon burial is consistent with evidence for widespread volcanism during OAE 2, so that organomineral carbon burial may represent a potential feedback to volcanic degassing of CO2.

  20. Great Basin paleontological database

    USGS Publications Warehouse

    Zhang, N.; Blodgett, R.B.; Hofstra, A.H.

    2008-01-01

    The U.S. Geological Survey has constructed a paleontological database for the Great Basin physiographic province that can be served over the World Wide Web for data entry, queries, displays, and retrievals. It is similar to the web-database solution that we constructed for Alaskan paleontological data (www.alaskafossil.org). The first phase of this effort was to compile a paleontological bibliography for Nevada and portions of adjacent states in the Great Basin that has recently been completed. In addition, we are also compiling paleontological reports (Known as E&R reports) of the U.S. Geological Survey, which are another extensive source of l,egacy data for this region. Initial population of the database benefited from a recently published conodont data set and is otherwise focused on Devonian and Mississippian localities because strata of this age host important sedimentary exhalative (sedex) Au, Zn, and barite resources and enormons Carlin-type An deposits. In addition, these strata are the most important petroleum source rocks in the region, and record the transition from extension to contraction associated with the Antler orogeny, the Alamo meteorite impact, and biotic crises associated with global oceanic anoxic events. The finished product will provide an invaluable tool for future geologic mapping, paleontological research, and mineral resource investigations in the Great Basin, making paleontological data acquired over nearly the past 150 yr readily available over the World Wide Web. A description of the structure of the database and the web interface developed for this effort are provided herein. This database is being used ws a model for a National Paleontological Database (which we am currently developing for the U.S. Geological Survey) as well as for other paleontological databases now being developed in other parts of the globe. ?? 2008 Geological Society of America.

  1. PNAS Plus: Origin of first cells at terrestrial, anoxic geothermal fields

    NASA Astrophysics Data System (ADS)

    Mulkidjanian, Armen Y.; Bychkov, Andrew Yu.; Dibrova, Daria V.; Galperin, Michael Y.; Koonin, Eugene V.

    2012-04-01

    All cells contain much more potassium, phosphate, and transition metals than modern (or reconstructed primeval) oceans, lakes, or rivers. Cells maintain ion gradients by using sophisticated, energy-dependent membrane enzymes (membrane pumps) that are embedded in elaborate ion-tight membranes. The first cells could possess neither ion-tight membranes nor membrane pumps, so the concentrations of small inorganic molecules and ions within protocells and in their environment would equilibrate. Hence, the ion composition of modern cells might reflect the inorganic ion composition of the habitats of protocells. We attempted to reconstruct the "hatcheries" of the first cells by combining geochemical analysis with phylogenomic scrutiny of the inorganic ion requirements of universal components of modern cells. These ubiquitous, and by inference primordial, proteins and functional systems show affinity to and functional requirement for K+, Zn2+, Mn2+, and phosphate. Thus, protocells must have evolved in habitats with a high K+/Na+ ratio and relatively high concentrations of Zn, Mn, and phosphorous compounds. Geochemical reconstruction shows that the ionic composition conducive to the origin of cells could not have existed in marine settings but is compatible with emissions of vapor-dominated zones of inland geothermal systems. Under the anoxic, CO2-dominated primordial atmosphere, the chemistry of basins at geothermal fields would resemble the internal milieu of modern cells. The precellular stages of evolution might have transpired in shallow ponds of condensed and cooled geothermal vapor that were lined with porous silicate minerals mixed with metal sulfides and enriched in K+, Zn2+, and phosphorous compounds.

  2. Calcareous nannoplankton changes across the early Toarcian oceanic anoxic event in the western Tethys

    NASA Astrophysics Data System (ADS)

    Mattioli, Emanuela; Pittet, Bernard; Suan, Guillaume; Mailliot, Samuel

    2008-09-01

    Calcareous nannoplankton were profoundly affected by environmental perturbations coincident with the early Toarcian oceanic anoxic event (T-OAE). We quantify the abundance of nannofossils across the T-OAE at three locations in Western Europe, where the event is marked by a prominent negative carbon isotope excursion (CIE). Data were treated by statistical analysis, and the Shannon diversity index was applied in order to describe nannofossil assemblage changes related to paleoenvironmental evolution. In the basal Toarcian, before the T-OAE, high proportions of taxa with an affinity for low temperature (e.g., P. liasicus, T. patulus, Bussonius) occurred. This observation is consistent with interpretations of published oxygen isotope records. During the T-OAE, the lowest abundance of nannofossils is observed, but there is a peak of a coccolith (Calyculus) from an organism that probably thrived in low-saline surface waters depleted of nitrate. At the end of the perturbation, the lowest diversities of nannofossils occurred, and assemblages are dominated by Crepidolithus crassus, a deep dweller. This interval corresponded to progressive reoxygenation of deep water and the reoccupation of the deep photic zone by nannoplankton. The highest abundance of nannofossils is recorded above the CIE and testifies to the recovery of the entire nannoplankton community. The T-OAE was widespread (perhaps global) and probably linked to major changes in the atmosphere and hydrosphere. However, the record of this event varies in the basins surrounding the western Tethys, suggesting regional imprints on the global signal. The regional variability may attest to establishment of effective connections between the Arctic and Tethys oceans, which allowed cool, low-saline water formed at high latitudes to stream toward the western Tethys.

  3. Degradation of trifluoroacetate in oxic and anoxic sediments

    USGS Publications Warehouse

    Visscher, P.T.; Culbertson, C.W.; Oremland, R.S.

    1994-01-01

    THE deleterious effect of chlorofluorocarbons on stratospheric ozone has led to international cooperation to end their use. The search for acceptable alternatives has focused on hydrofluorocarbons (HFCs) or hydrochlorofluorocarbons (HCFCs) which are attractive because they have relatively short atmospheric residence times. HFCs and HCFCs are attacked by tropospheric hydroxyl radicals, leading to the formation of trifluoroacetate (TFA). Most of the atmospheric TFA is deposited at the Earth's surface, where it is thought to be highly resistant to bacterial attack. Therefore, use of HCFCs and HFCs may lead to accumulation of TFA in soils, where it could prove toxic or inhibitory to plants and soil microbial communities. Although little is known about the toxicity of TFA, monofluoroacetate, which occurs at low levels in some plants and which is susceptible to slow attack by aerobic soil microbes, is known to be acutely toxic. Here we report that TFA can be rapidly degraded microbially under anoxic and oxic conditions. These results imply that significant microbial sinks exist in nature for the elimination of TFA from the environment. We also show that oxic degradation of TFA leads to the formation of fluoroform, a potential ozone-depleting compound with a much longer atmospheric lifetime than the parent compounds.The deleterious effect of chlorofluorcarbons on stratospheric ozone has led to international cooperation to end their use. The search for acceptable alternatives has focused on hydroflnorocarbons (HFCs) or hydrochloroflnorcarbons (HCFs) which are attractive because they have relatively short atmospheric residence times. HFCs and HCFs are attacked by tropospheric hydroxyl radicals, leading to the formation of trifluoroacetate (TFA). Most of the atmospheric TFA is deposited at the Earth's surface, where it is thought to be highly resistant to bacterial attack. Therefore, use of HCFs and HCFs may lead to accummulation of TFA in soils, where it could prove toxic

  4. Understanding Oceanic Anoxic Events: An Integrated Geochemical Approach

    NASA Astrophysics Data System (ADS)

    Cohen, A. S.; Coe, A. L.; Kemp, D. B.; Pearce, C. R.

    2007-12-01

    Discrete intervals of widespread organic carbon accumulation, termed Oceanic Anoxic Events (OAEs), occurred at a few relatively brief intervals during the Mesozoic. Recent studies have shown that these events took place at the same time as other substantial environmental changes that included global warming, ocean acidification, and unusually high levels of species extinctions. However, many factors relating to the behaviour of the Earth System during OAEs remain unclear. These include: The primary driving mechanism(s) - was there one common mechanism or were OAEs the result of different processes; the spatial and temporal extent of seawater anoxia during OAEs; the precise effects on marine and terrestrial biota; variations in atmospheric CO2 and global temperature; and the mechanism and timescale of Earth's recovery process. The records of environmental change during OAEs are best preserved in marine deposits, with continental shelf sections being particularly well studied. The combined use of geochemical, sedimentological and palaeontological observations indicates a complex interplay of factors. Significant advances in our understanding of OAEs have taken place in the last decade or so using new geochemical and isotopic proxies and a high- resolution, multidisciplinary approach. For example, Sr- and Os-isotope data indicate that rates of chemical weathering increased markedly during the Toarcian (Early Jurassic) OAE, whilst Mo-isotope data suggest that the areal extent of seawater anoxia fluctuated during the OAE despite the persistence of euxinic conditions in some regions. The pattern of Mo-isotope data for the Toarcian contrasts strongly with new Mo-isotope results from the Kimmeridge Clay Formation (Late Jurassic), when anoxic conditions were confined to European epicontinental seas and were likely to have resulted from very different primary causes. Cyclostratigraphic analysis has been used to provide a temporal framework for the timescale of OAEs at sub

  5. The behavior of scavenged isotopes in marine anoxic environments: 210Pb and 210Po in the water column of the Black Sea

    NASA Astrophysics Data System (ADS)

    Wei, Ching-Ling; Murray, James W.

    1994-04-01

    Vertical profiles of dissolved and particulate 210Pb and 210Po were determined at two stations in the Black Sea in June 1988. Vertical fluxes of 210Pb and 210Po were also measured in the upper 150 m, using floating sediment traps. The fractionation of 210Pb between dissolved and particulate phases in the Black Sea is strongly influenced by the redox conditions in the water column. Dissolved 210Pb dominates in the oxic zone, while particulate 210Pb is the major form in the deep sulfide-rich anoxic zone. The distribution of 210Pb across the suboxic zone appears to be mainly controlled by redox cycling of manganese and iron. In the sulfide-rich layer coprecipitation of lead with iron sulfide is probably the dominant scavenging mechanism. A simple scavenging model was used to calculate the residence times of dissolved and particulate 210Pb in the oxic, suboxic, and anoxic zones. The residence times of dissolved 210Pb relative to scavenging by particles are 0.5-1, 2-3, and 3.5 years in the oxic, suboxic, and anoxic layers, respectively. The corresponding residence times of particulate 210Pb relative to particle removal processes in the same layers are 0.1, 1.5-2.5, and 8.5 years, respectively. A particle settling velocity of about 40 m y -1 was derived from the 210Pb /226Ra disequilibrium in the deep Black Sea. The relatively short residence times of 210Pb support the hypothesis that anoxic basins are important sites for boundary scavenging of 210Pb. The 210Po profiles indicate that biological rather than inorganic particles are the major carrier phases for polonium in the Black sea. Dissolved 210Po is deficient relative to dissolved 210Pb in the euphotic zone, suggesting preferential uptake of 210Po over 210Pb by particles residing in that layer. The residence time of dissolved 210Po, with respect to scavenging by particles in the euphotic zone, is about 200 days. Below the mid-depth of the suboxic zone, 210Po is in excess relative to 210Pb, and is thought to originate

  6. Caloris Basin

    NASA Image and Video Library

    1999-12-07

    Caloris Basin on Mercury, is one of the largest basins in the solar system, its diameter exceeds 1300 kilometers and is in many ways similar to the great Imbrium basin on the Moon. This image is from NASA Mariner 10 spacecraft which launched in 1974.

  7. Late Pliensbachian (Early Jurassic) Cold Seep Carbonates: Methane Release Prior to the Toarcian Oceanic Anoxic Event

    NASA Astrophysics Data System (ADS)

    van de Schootbrugge, B.; Harazim, D.; Sorichter, K.; Fiebig, J.; Zanella, F.; Oschmann, W.; Rosenthal, Y.

    2008-12-01

    We present evidence for methane seepage during the Early Jurassic (~ 185 Ma) in the form of newly discovered extensive occurrences of carbonate concretions that resemble the subsurface plumbing system of better known Cenozoic to Recent examples of cold seep carbonates. Columnar carbonate concretions of up to 1 m in length that are perpendicular to bedding, occur abundantly in the Upper Pliensbachian (upper Amaltheus margaritatus Zone, gibbosus Subzone) in outcrops in the vicinity of Riviere-sur-Tarn, southern France. Stable isotope analyses of these nodules show depleted δ13C values that decrease from the rim to the center from -18.8 to -25.7‰ (V-PDB), but normal marine δ18O values (-1.8‰). Computer tomographic (CT) scanning of the columnar concretions show one or more central canals that are lined or filled entirely with pyrite and late diagenetic minerals. Septarian cracks are also filled with secondary calcite and/or siderite. Based on our preliminary geochemical and sedimentological observations we suggest that these concretions formed as a combination of the anaerobic oxidation of methane (AOM) and sulfate reduction within the sediment. Previously, these concretions with one, two or more central tubes have been ascribed to the activity of an enigmatic organism, possibly with annelid or arthropod affinities, known as Tisoa siphonalis. Our results suggest tisoan structures are abiogenic. Interestingly, Tisoa siphonalis has been described from many locations in the Grands Causses Basin in southern France, and from northern France and Luxemburg, always occurring at the same stratigraphic level. Upper Pliensbachian cold seep carbonates thus possibly cover an area of several thousand square kilometers, largely distributed across the basin centres of the NW European epicontinental seaway. Our findings may have far reaching implications for understanding the Toarcian Oceanic Anoxic Event, which is interpreted to bear the hallmarks of catastrophic methane release

  8. Anoxic stress leads to hydrogen peroxide formation in plant cells.

    PubMed

    Blokhina, O B; Chirkova, T V; Fagerstedt, K V

    2001-06-01

    Hydrogen peroxide (H2O2) was detected cytochemically in plant tissues during anoxia and re-oxygenation by transmission electron microscopy using its reaction with cerium chloride to produce electron dense precipitates of cerium perhydroxides. Anoxia-tolerant yellow flag iris (Iris pseudacorus) and rice (Oryza sativa), and anoxia-intolerant wheat (Triticum aestivum) and garden iris (Iris germanica) were used in the experiments. In all plants tested, anoxia and re-oxygenation increased H2O2 in plasma membranes and the apoplast. In the anoxia-tolerant species the response was delayed in time, and in highly tolerant I. pseudacorus plasma membrane associated H2O2 was detected only after 45 d of oxygen deprivation. Quantification of cerium precipitates showed a statistically significant increase in the amount of H2O2 caused by anoxia in wheat root meristematic tissue, but not in the anoxia-tolerant I. pseudacorus rhizome parenchyma. Formation of H2O2 under anoxia is considered mainly an enzymatic process (confirmed by an enzyme inhibition analysis) and is due to the trace amount of dissolved oxygen (below 10(-5) M) present in the experimental system. The data suggest oxidative stress is an integral part of oxygen deprivation stress, and emphasize the importance of the apoplast and plasma membrane in the development of the anoxic stress response.

  9. Anoxic marine lakes - an analogue environment for insular phosphorite formation

    SciTech Connect

    Burnett, W.C. )

    1990-06-01

    Hundreds of islands in the tropical Pacific Ocean contain phosphate deposits ranging from inconsequential to economically significant in size. Although many of these deposits clearly have formed by the interaction of avian guano with underlying limestone, some display evidence of having developed within an aqueous environment. Several of the emergent carbonate islands in the southern part of Palau contain phosphate deposits that the authors speculate formed in anoxic marine lakes, similar to those which still occur on a few of these islands. Lake water, sediments, and sediment pore waters from Jellyfish Lake, on the island of Eil Malk in Palau, were analyzed during an expedition in 1987. The results of this investigation supported, but did not provide, conclusive evidence of our hypothesis. Pore water profiles of phosphate and fluoride confirmed precipitation of carbonate fluorapatite. However, the extremely high bulk sediment accumulation rate, driven by the high biological productivity of the surface waters of the lake, dilutes authigenic phosphate to low levels. They have refined their original proposal to suggest that phosphate deposits may form either by: (1) subaerial weathering and concentration of phosphatic sediments after these lakes disappear; or (2) interaction of phosphate-enriched sediment pore solutions with limestone at the underlying contact. Another expedition to test these concepts is being planned.

  10. Influence of substrate on fouling in anoxic immersed membrane bioreactors.

    PubMed

    McAdam, Ewan J; Judd, Simon J; Cartmell, Elise; Jefferson, Bruce

    2007-09-01

    The influence of carbon substrate chemistry on membrane bioreactor (MBR) fouling in anoxic conditions has been evaluated. The use of a weak carboxylic acid (acetic acid) resulted in the production of large open-floc structures (up to 508microm) that were susceptible to breakage. Primary particles (d(10) and d(20) particle sizes, 5.5+/-1.3 and 15.3+/-8.2microm, respectively) and macromolecular soluble microbial products (SMPs) were generated, directly impacting on membrane fouling. The use of a primary alcohol (ethanol), on the other hand, encouraged the growth of flocs similar to activated sludge. These flocs produced low concentrations of primary particles (d(10) and d(20) particle sizes, 120.6+/-36.1 and 185.2+/-62.7microm, respectively) and high-molecular-weight SMP, and the particles had sufficient mechanical integrity to withstand shear. Consequently, the use of ethanol resulted in sufficient suppression of fouling to extend the filtration time by a factor of three. An increase in MLSS concentration did not directly impact upon fouling when operating with ethanol, primarily because of the low concentration of particulate matter produced.

  11. Trace metal dynamics in a seasonally anoxic lake

    NASA Astrophysics Data System (ADS)

    Morfett, K.; Davison, W.; Hamilton-Taylor, J.

    1988-02-01

    Selected results are presented from a detailed 12-month study of trace metals in a seasonally anoxic lake. Dissolved concentrations of Fe, Mn, organic carbon, Cd, Cu, Pb, Zn, and pH were determined in the water column and the interstitial waters on 39 occasions. Trace metal concentrations remained low throughout the year in both water column and pore waters. There was evidence for some remobilization at the sediment-water interface but sediments deeper than 3 cm acted as a sink throughout the year. Variations in the water concentrations were largely associated with increased loading during periods of heavy rainfall. During the summer, concentrations of Cu and Zn in the waters overlying the sediments were enhanced by release from decomposing algal material. Similarly, enhanced concentrations of Cd, Cu, Pb, and Zn were observed during periods of much reduced mixing during ice-cover. Although there were large seasonal variations in the concentrations of dissolved and particulate Fe and Mn, there were no comparable changes in the concentrations of trace metals.

  12. Minimum Energy Requirements for Sustained Microbial Activity in Anoxic Sediments

    NASA Technical Reports Server (NTRS)

    Hoehler, Tori M.; Alperin, Marc J.; Albert, Daniel B.; Martens, Christoper S.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Currently understood mechanisms of biochemical energy conservation dictate that, in order to be biologically useful, energy must be available to organisms in "quanta" equal to, at minimum one-third to one-fifth of the energy required to synthesize ATP in vivo. The existence of this biological energy quantum means that a significant fraction of the chemical amp on Earth cannot be used to drive biological productivity, and places a fundamental thermodynamic constraint on the origins, evolution, and distribution of life. We examined the energy requirements of intact microbial assemblages in anoxic sediments from Cape Lookout Bight, NC, USA, using dissolved hydrogen concentrations as a non-invasive probe. In this system, the thermodynamics of metabolic processes occurring inside microbial cells is reflected quantitatively by H2 concentrations measured outside those cells. We find that methanogenic archaea are supported by energy yields as small as 10 kJ per mol, about half the quantity calculated from studies of microorganisms in culture. This finding implies that a significantly broader range of geologic and chemical niches might be exploited by microorganisms than would otherwise be expected.

  13. Microbial community- and metabolite dynamics of an anoxic dechlorinating bioreactor.

    PubMed

    Maphosa, Farai; Smidt, Hauke; de Vos, Willem M; Röling, Wilfred F M

    2010-07-01

    Monitoring and quantification of organohalide respiring bacteria is essential for optimization of on-site bioremediation of anoxic subsurface sites contaminated with chloroethenes. Molecular monitoring and model simulations were applied to determine degradation performance of an in situ dechlorinating bioreactor and its influence on the contamination plume. Dehalococcoides was the dominant dechlorinating microorganism as revealed by qPCR targeting 16S rRNA- and chloroethene reductive dehalogenase-encoding genes (tceA, vcrA, bvcA). The presence of all three reductive dehalogenases genes indicated coexistence of several distinct organohalide respiring bacterial populations in the bioreactor and groundwater. Mass balancing revealed that main dechlorinating activities were reduction of cis-dichloroethene and vinyl chloride. Analysis of growth kinetics showed that when performance of the bioreactor improved due to especially the addition of molasses, dechlorinating microorganisms were growing close to their maximum growth rate. Once near-complete dehalogenation was achieved, Dehalococcoides only grew slowly and population density did not further increase. The bioreactor influenced dechlorinating populations in the plume with subsequent decrease in chlorinated compound concentrations over time. In the present study, a combination of molecular diagnostics with mass-balancing and kinetic modeling improved insight into organohalide respiring bacteria and metabolite dynamics in an in situ dechlorinating bioreactor and showed its utility in monitoring bioremediation.

  14. Minimum Energy Requirements for Sustained Microbial Activity in Anoxic Sediments

    NASA Technical Reports Server (NTRS)

    Hoehler, Tori M.; Alperin, Marc J.; Albert, Daniel B.; Martens, Christoper S.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Currently understood mechanisms of biochemical energy conservation dictate that, in order to be biologically useful, energy must be available to organisms in "quanta" equal to, at minimum one-third to one-fifth of the energy required to synthesize ATP in vivo. The existence of this biological energy quantum means that a significant fraction of the chemical amp on Earth cannot be used to drive biological productivity, and places a fundamental thermodynamic constraint on the origins, evolution, and distribution of life. We examined the energy requirements of intact microbial assemblages in anoxic sediments from Cape Lookout Bight, NC, USA, using dissolved hydrogen concentrations as a non-invasive probe. In this system, the thermodynamics of metabolic processes occurring inside microbial cells is reflected quantitatively by H2 concentrations measured outside those cells. We find that methanogenic archaea are supported by energy yields as small as 10 kJ per mol, about half the quantity calculated from studies of microorganisms in culture. This finding implies that a significantly broader range of geologic and chemical niches might be exploited by microorganisms than would otherwise be expected.

  15. Anoxic biodegradation of petroleum hydrocarbons in saline media using denitrifier biogranules.

    PubMed

    Moussavi, Gholamreza; Shekoohiyan, Sakine; Naddafi, Kazem

    2016-07-01

    The total petroleum hydrocarbons (TPH) biodegradation was examined using biogranules at different initial TPH concentration and contact time under anoxic condition in saline media. The circular compact biogranules having the average diameter between 2 and 3mm were composed of a dense population of Bacillus spp. capable of biodegrading TPH under anoxic condition in saline media were formed in first step of the study. The biogranules could biodegrade over 99% of the TPH at initial concentration up to 2g/L at the contact time of 22h under anoxic condition in saline media. The maximum TPH biodegradation rate of 2.6 gTPH/gbiomass.d could be obtained at initial TPH concentration of 10g/L. Accordingly, the anoxic biogranulation is a possible and promising technique for high-rate biodegradation of petroleum hydrocarbons in saline media. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. ENANTIOSELECTIVE MICROBIAL TRANSFORMATION OF THE PHENYLPYRAZOLE INSECTICIDE FIPRONIL IN ANOXIC SEDIMENTS

    EPA Science Inventory

    Fipronil, a chiral insecticide, was biotransformed initially to fipronil sulfide in anoxic sediment slurries following a short lag period. Sediment slurries characterized as either sulfidogenic or methanogenic transformed fipronil with half-lives of approximately 35 and 40 days, ...

  17. ENVIRONMENTAL CHARACTERISTICS AFFECTING REDUCTIVE TRANSFORMATION OF ORGANIC POLLUTANTS IN ANOXIC SEDIMENTS

    EPA Science Inventory

    Reductive transformations are important processes for determining the fate of organic pollutants in anoxic environments. These processes are most often microbially mediated by both direct and indirect means. For example, specific bacteria transform organic pollutants directly as ...

  18. ENVIRONMENTAL CHARACTERISTICS AFFECTING REDUCTIVE TRANSFORMATION OF ORGANIC POLLUTANTS IN ANOXIC SEDIMENTS

    EPA Science Inventory

    Reductive transformations are important processes for determining the fate of organic pollutants in anoxic environments. These processes are most often microbially mediated by both direct and indirect means. For example, specific bacteria transform organic pollutants directly as ...

  19. Treatment of synthetic refinery wastewater in anoxic-aerobic sequential moving bed reactors and sulphur recovery.

    PubMed

    Mallick, Subrat Kumar; Chakraborty, Saswati

    2017-09-18

    Objective of the present study was to simultaneously biodegrade synthetic petroleum refinery wastewater containing phenol (750 mg/L), sulphide (750 mg/L), hydrocarbon (as emulsified diesel of 300 mg/L), ammonia-nitrogen (350 mg/L) at pH >9 in anoxic-aerobic sequential moving bed reactors. The optimum mixing speed of anoxic reactor was observed at 20 rpm and beyond that, removal rate remained constant. In anoxic reactor the minimum hydraulic retention time was observed to be 2 days for complete removal of sulphide, 40-50% removal of phenol and total hydrocarbons and 52% of sulphur recovery. The optimum HRT of aerobic moving bed reactor was observed as 16 h (total HRT of 64 h for anoxic and aerobic reactors) for complete removals of phenol, total hydrocarbons, COD (chemical oxygen demand) and ammonia-nitrogen with nitrification.

  20. ENANTIOSELECTIVE MICROBIAL TRANSFORMATION OF THE PHENYLPYRAZOLE INSECTICIDE FIPRONIL IN ANOXIC SEDIMENTS

    EPA Science Inventory

    Fipronil, a chiral insecticide, was biotransformed initially to fipronil sulfide in anoxic sediment slurries following a short lag period. Sediment slurries characterized as either sulfidogenic or methanogenic transformed fipronil with half-lives of approximately 35 and 40 days, ...

  1. Activation of DOR Attenuates Anoxic K+ Derangement via Inhibition of Na+ Entry in Mouse Cortex

    PubMed Central

    Chao, Dongman; Bazzy-Asaad, Alia; Balboni, Gianfranco; Salvadori, Severo

    2008-01-01

    We have recently found that in the mouse cortex, activation of δ-opioid receptor (DOR) attenuates the disruption of K+ homeostasis induced by hypoxia or oxygen–glucose deprivation. This novel observation suggests that DOR may protect neurons from hypoxic/ischemic insults via the regulation of K+ homeostasis because the disruption of K+ homeostasis plays a critical role in neuronal injury under hypoxic/ischemic stress. The present study was performed to explore the ionic mechanism underlying the DOR-induced neuroprotection. Because anoxia causes Na+ influx and thus stimulates K+ leakage, we investigated whether DOR protects the cortex from anoxic K+ derangement by targeting the Na+-based K+ leakage. By using K+-sensitive microelectrodes in mouse cortical slices, we showed that 1) lowering Na+ concentration and substituting with impermeable N-methyl-D-glucamine caused a concentration-dependent attenuation of anoxic K+ derangement; 2) lowering Na+ concentration by substituting with permeable Li+ tended to potentiate the anoxic K+ derangement; and 3) the DOR-induced protection against the anoxic K+ responses was largely abolished by low-Na+ perfusion irrespective of the substituted cation. We conclude that external Na+ concentration greatly influences anoxic K+ derangement and that DOR activation likely attenuates anoxic K+ derangement induced by the Na+-activated mechanisms in the cortex. PMID:18203692

  2. Na+ mechanism of δ-opioid receptor induced protection from anoxic K+ leakage in the cortex

    PubMed Central

    Chao, Dongman; Balboni, Gianfranco; Lazarus, Lawrence H; Salvadori, Severo; Xia, ing

    2009-01-01

    Activation of δ-opioid receptors (DOR) attenuates anoxic K+ leakage and protects cortical neurons from anoxic insults by inhibiting Na+ influx. It is unknown, however, which pathway(s) that mediates the Na+ influx is the target of DOR signal. In the present work, we found that in the cortex, 1) DOR protection was largely dependent on the inhibition of anoxic Na+ influxes mediated by voltage-gated Na+ channels; 2) DOR activation inhibited Na+ influx mediated by ionotropic glutamate NMDA receptors, but not that by non-NMDA receptors though both played a role in anoxic K+ derangement; and 3) DOR activation had little effect on Na+/Ca2+ exchanger-based response to anoxia. We conclude that, 1) DOR activation attenuates anoxic K+ derangement by restricting Na+ influx mediated by Na+ channels and NMDA receptors, and 2) non-NMDA receptors and Na+/Ca2+ exchangers, though involved in anoxic K+ derangement in certain degrees, are less likely the targets of DOR signal. PMID:19189047

  3. Functional integrity in children with anoxic brain injury from drowning.

    PubMed

    Ishaque, Mariam; Manning, Janessa H; Woolsey, Mary D; Franklin, Crystal G; Tullis, Elizabeth W; Beckmann, Christian F; Fox, Peter T

    2017-10-01

    Drowning is a leading cause of accidental injury and death in young children. Anoxic brain injury (ABI) is a common consequence of drowning and can cause severe neurological morbidity in survivors. Assessment of functional status and prognostication in drowning victims can be extremely challenging, both acutely and chronically. Structural neuroimaging modalities (CT and MRI) have been of limited clinical value. Here, we tested the utility of resting-state functional MRI (rs-fMRI) for assessing brain functional integrity in this population. Eleven children with chronic, spastic quadriplegia due to drowning-induced ABI were investigated. All were comatose immediately after the injury and gradually regained consciousness, but with varying ability to communicate their cognitive state. Eleven neurotypical children matched for age and gender formed the control group. Resting-state fMRI and co-registered T1-weighted anatomical MRI were acquired at night during drug-aided sleep. Network integrity was quantified by independent components analysis (ICA), at both group- and per-subject levels. Functional-status assessments based on in-home observations were provided by families and caregivers. Motor ICNs were grossly compromised in ABI patients both group-wise and individually, concordant with their prominent motor deficits. Striking preservations of perceptual and cognitive ICNs were observed, and the degree of network preservation correlated (ρ = 0.74) with the per-subject functional status assessments. Collectively, our findings indicate that rs-fMRI has promise for assessing brain functional integrity in ABI and, potentially, in other disorders. Furthermore, our observations suggest that the severe motor deficits observed in this population can mask relatively intact perceptual and cognitive capabilities. Hum Brain Mapp 38:4813-4831, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  4. Anoxic biodegradation of BTEX in a biotrickling filter.

    PubMed

    Akmirza, Ilker; Pascual, Celia; Carvajal, Andrea; Pérez, Rebeca; Muñoz, Raúl; Lebrero, Raquel

    2017-02-27

    Emissions of BTEX (benzene, toluene, ethylbenzene and xylene) from the petrochemical industry are characterized by a low pollutants concentration and the absence of oxygen. Biodegradation of these pollutants using nitrate as the electron acceptor is of key interest to reuse the residual gas for inertization purposes. However, the biological mineralization of BTEX is often limited by their recalcitrant nature and the toxicity of the secondary metabolites produced. The potential of an anoxic biotrickling filter for the treatment of a model O2-free BTEX-laden emission at inlet individual concentrations of ~700mgm(-3) was here evaluated. A UV oxidation step was also tested both in the recycling liquid and in the inlet gas emission prior to biofiltration. Removal efficiencies >90% were achieved for both toluene and ethylbenzene, corresponding to elimination capacities (ECs) of 1.4±0.2gm(-3)h(-1) and 1.5±0.3gm(-3)h(-1), respectively, while ~45% of xylene (EC=0.6±0.1g m(-3)h(-1)) was removed at a liquid recycling rate of 2mh(-1). Benzene biodegradation was however limited by the accumulation of toxic metabolites in the liquid phase. The oxidation of these intermediates in the recycling liquid by UV photolysis boosted benzene abatement, achieving an average EC of 0.5±0.2gm(-3)h(-1) and removals of ~40%. However, the implementation of UV oxidation as a pretreatment step in the inlet gas emission resulted in the deterioration of the BTEX biodegradation capacity of the biotrickling filter. Finally, a high bacterial diversity was observed throughout the entire experiment, the predominant phyla being Proteobacteria and Deinococcus-thermus.

  5. Anoxic deep-sea microbial dolomite as a paleoceanographic archive - new insights from old "bugs"

    NASA Astrophysics Data System (ADS)

    Miller, N. R.; Leybourne, M. I.

    2010-12-01

    Earth’s history of biogenic carbonate production is dominated by pre-skeletal (late Ediacaran) microbe-catalyzed carbonate, including low T/P microbial (aka organogenic) dolomite, but paleoceanographic contexts are unclear due to the lack of proxy control provided by skeletal analogs and/or diagenesis. Microbial communities affiliated with dolomite generation (chiefly sulfate reducers and methanogens) are now known to persist in a diversity of Recent anoxic environments, but only deep-sea settings are sufficiently insulated from eustatic-meteoric diagenesis to preserve long-term records of possible paleoceanographic significance. The Miocene Monterey Formation contains episodic-to-cyclic microbial dolomite intervals interstratified with microfossil calcite, and thereby offers an excellent test the paleoceoanographic archive potential of microbial dolomite. Accordingly, we established a detailed dolomite chemostratigraphic profile (δ18O, δ13C, TOC, trace elements/REEs) from a continuous, thermally immature, Monterey core (offshore Santa Barbara-Ventura Basin), preserving >100 distinct early diagenetic (pre significant compaction, pre-diatom dissolution, post-pyrite) microbial dolomite intervals. Despite dolomite horizons being physically separate from one stratum to the next, they exhibit regular core-wide variations in δ13C and δ18O. Dolomite within the main Monterey depositional interval has entirely negative δ13C values (-2 to -16‰) consistent with generation in the zone of microbial sulfate reduction, whereas positive δ13C values (+2 to +9‰) consistent with generation from methanogenic pore-waters occur in lithologic transitions with bounding formations. Dolomites within the main Monterey depositional interval mirror microfossil calcite δ18O variations, notably pronounced global mid-Miocene enrichment after ~14 Ma linked to cooling and significant expansion of Antarctic ice. Dolomite δ13C mirrors sediment accumulation rate, with lightest values

  6. Phylogenetic Diversity of Bacterial and Archaeal Communities in the Anoxic Zone of the Cariaco Basin†

    PubMed Central

    Madrid, Vanessa M.; Taylor, Gordon T.; Scranton, Mary I.; Chistoserdov, Andrei Y.

    2001-01-01

    Microbial community samples were collected from the anoxic zone of the Cariaco Basin at depths of 320, 500, and 1,310 m on a November 1996 cruise and were used to construct 16S ribosomal DNA libraries. Of 60 nonchimeric sequences in the 320-m library, 56 belonged to the ɛ subdivision of the Proteobacteria (ɛ-Proteobacteria) and 53 were closely related to ectosymbionts of Rimicaris exoculata and Alvinella pompejana, which are referred to here as epsilon symbiont relatives (ESR). The 500-m library contained sequences affiliated with the fibrobacteria, the Flexibacter-Cytophaga-Bacteroides division, the division Verrucomicrobia, the division Proteobacteria, and the OP3 candidate division. The Proteobacteria included members of the γ, δ, ɛ and new candidate subdivisions, and γ-proteobacterial sequences were dominant (25.6%) among the proteobacterial sequences. As in the 320-m library, the majority of the ɛ-proteobacteria belonged to the ESR group. The genus Fibrobacter and its relatives were the second largest group in the library (23.6%), followed by the δ-proteobacteria and the ɛ-proteobacteria. The 1,310-m library had the greatest diversity; 59 nonchimeric clones in the library contained 30 unique sequences belonging to the planctomycetes, the fibrobacteria, the Flexibacter-Cytophaga-Bacteroides division, the Proteobacteria, and the OP3 and OP8 candidate divisions. The proteobacteria included members of new candidate subdivisions and the β, γ, δ, and ɛ-subdivisions. ESR sequences were still present in the 1,310-m library but in a much lower proportion (8.5%). One archaeal sequence was present in the 500-m library (2% of all microorganisms in the library), and eight archaeal sequences were present in the 1,310-m library (13.6%). All archaeal sequences fell into two groups; two clones in the 1,310-m library belonged to the kingdom Crenarchaeota and the remaining sequences in both libraries belonged to the kingdom Euryarchaeota. The latter group appears to

  7. Attenuation and colloidal mobilization of bacteriophages in natural sediments under anoxic as compared to oxic conditions.

    PubMed

    Klitzke, Sondra; Schroeder, Jendrik; Selinka, Hans-Christoph; Szewzyk, Regine; Chorus, Ingrid

    2015-06-15

    Redox conditions are known to affect the fate of viruses in porous media. Several studies report the relevance of colloid-facilitated virus transport in the subsurface, but detailed studies on the effect of anoxic conditions on virus retention in natural sediments are still missing. Therefore, we investigated the fate of viruses in natural flood plain sediments with different sesquioxide contents under anoxic conditions by considering sorption to the solid phase, sorption to mobilized colloids, and inactivation in the aqueous phase. Batch experiments were conducted under oxic and anoxic conditions at pH values between 5.1 and 7.6, using bacteriophages MS2 and PhiX174 as model viruses. In addition to free and colloid-associated bacteriophages, dissolved and colloidal concentrations of Fe, Al and organic C as well as dissolved Ca were determined. Results showed that regardless of redox conditions, bacteriophages did not adsorb to mobilized colloids, even under favourable charge conditions. Under anoxic conditions, attenuation of bacteriophages was dominated by sorption over inactivation, with MS2 showing a higher degree of sorption than PhiX174. Inactivation in water was low under anoxic conditions for both bacteriophages with about one log10 decrease in concentration during 16 h. Increased Fe/Al concentrations and a low organic carbon content of the sediment led to enhanced bacteriophage removal under anoxic conditions. However, even in the presence of sufficient Fe/A-(hydr)oxides on the solid phase, bacteriophage sorption was low. We presume that organic matter may limit the potential retention of sesquioxides in anoxic sediments and should thus be considered for the risk assessment of virus breakthrough in the subsurface. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Anoxic stress and rapid cold hardening enhance cold tolerance of the migratory locust.

    PubMed

    Cui, Feng; Wang, Hongsheng; Zhang, Hanying; Kang, Le

    2014-10-01

    Anoxia and rapid cold hardening (RCH) can increase the cold tolerance of many animals. However, mechanisms underlying these two kinds of stresses remain unclear. In this study, we aimed to explore the relationship of acclimation to cold stress with acclimation to anoxic stress in the migratory locust, Locusta migratoria. RCH at 0°C for 3h promoted the survival of cold stress-exposed locusts. Anoxic hypercapnia (CO2 anoxic treatment) for 40 min exerted an effect similar to that of RCH. Anoxic hypercapnia within 1h can all promote the cold hardiness of locusts. We investigated the transcript levels of six heat shock protein (Hsp) genes, namely, Hsp20.5, Hsp20.6, Hsp20.7, Hsp40, Hsp70, and Hsp90. Four genes, namely, Hsp90, Hsp40, Hsp20.5, and Hsp20.7, showed differential responses to RCH and anoxic hypercapnia treatments. Under cold stress, locusts exposed to the two regimens showed different responses for Hsp90, Hsp20.5, and Hsp20.7. However, the varied responses disappeared after recovery from cold stress. Compared with the control group, the transcript levels of six Hsp genes were generally downregulated in locusts subjected to anoxic hypercapnia or/and RCH. These results indicate that anoxic stress and RCH have different mechanisms of regulating the transcription of Hsp family members even if the two treatments exerted similar effects on cold tolerance of the migratory locust. However, Hsps may not play a major role in the promotion of cold hardiness by the two treatments.

  9. Influence of oxic/anoxic condition on sorption behavior of PFOS in sediment.

    PubMed

    Ololade, Isaac Ayodele; Zhou, Qin; Pan, Gang

    2016-05-01

    Sediment components and redox properties change with oxic/anoxic condition, which affect the environmental transport of perfluorooctane sulfonate (PFOS). Herein, the influence of oxic/anoxic condition on the variation of redox and residual components of sediments, where organic matter, iron and manganese oxides are separated from the original sediment collected from Lake Taihu, China, are investigated. Meanwhile, the distinguishing sorption behaviors of PFOS on various residual sediments under oxic and anoxic condition are studied. Sediment after extracting iron and manganese (S-FeMn), which possessed the highest organic carbon (0.99%), had the highest affinity for PFOS under oxic condition. However, anoxic environment resulted in an increase of the pH, dissolving of organic carbon and de-protonation of S-FeMn, which caused the lower sorption capacity of PFOS on S-FeMn. Sediment after extracting manganese (S-Mn) had the higher sorption ability in anoxic environment because the Fe(2+) from S-Mn provided more effective electrostatic sites for anionic PFOS. When the environment changed to oxic condition, the iron existed as trivalent form in S-Mn, which resulted in a block of effective sorption site and reduced the sorption amounts of PFOS. The higher percentage of manganese oxides restrained the sorption of PFOS. Hence, whether or not oxic/anoxic condition promoted the PFOS sorption depended on both the percentage and form of various components in the sediment. The study generated further insight into the environmental transport of PFOS in the sediments with different properties and the wetland system, where oxic/anoxic subsurface flow was constructed. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. A comparative study of phosphate sorption in lowland soils under oxic and anoxic conditions.

    PubMed

    Heiberg, Lisa; Pedersen, Thomas Vils; Jensen, Henning S; Kjaergaard, Charlotte; Hansen, Hans Christian Bruun

    2010-01-01

    Phosphate (P(i)) release due to Fe(III) oxide dissolution is well documented for soils undergoing reduction. The P(i) sorption properties of soils in anoxic conditions are, however, still under consideration. In this investigation, P(i) sorption to strictly anoxic soils was compared with oxic conditions to assess the potential of lowland soils to function as traps for P(i) when flooded with drainage water. Batch sorption experiments were performed on seven minerogenic soils. Sorption to the anoxic soils was conducted after anoxic incubation, resulting in reduction of 36 to 93% of the dithionite-extractable Fe(III) (Fe(BD)). Langmuir fitted P(i) sorption isotherms showed a P(i) release of up to 1.1 mmol kg(-1) in six soils when P(i) concentrations in the matrix (P(sol)) were lower than 10 microM. Phosphate desorption was attributed to dissolution of amorphous iron oxides, and higher pH under anoxic conditions. The point of zero net sorption (EPC(0)) increased 2- to 10-fold on reduction. Five soils showed higher P(i) sorption capacities in the anoxic than in the oxic state at higher P(sol) concentrations. Solubility calculations indicated that precipitation of vivianite or similar Fe(II) phosphates may have caused the higher sorption capacities. Use of maximum sorption capacity (S(max)) is therefore misleading as a measure of P(i) sorption at low P(sol) concentrations. The results demonstrate that none of the strongly anoxic soils, irrespective of the initial Fe(III) oxide content, the P saturation, and the degree of Fe(III) oxide reduction, could retain P(i) at natural P(sol) concentrations in agricultural drainage water.

  11. Shewanella denitrificans sp. nov., a vigorously denitrifying bacterium isolated from the oxic-anoxic interface of the Gotland Deep in the central Baltic Sea.

    PubMed

    Brettar, Ingrid; Christen, Richard; Höfle, Manfred G

    2002-11-01

    Three strains of denitrifying estuarine bacteria, OS217(T), 05220 and OS226, were characterized for their physiological and biochemical features, fatty acid profiles and their phylogenetic position based on 16S rDNA sequences. The strains were isolated from the oxic-anoxic interface of an anoxic basin of the central Baltic Sea. Phylogenetic analyses of the 16S rDNA sequences revealed a clear affiliation with members of the genus Shewanella of the gamma-Proteobacteria. The closest sequence similarity was seen with Shewanella baltica, Shewanella putrefaciens and Shewanella frigidimarina (95-96%). The dominant fatty acids were 16:1omega7c, 15:0 iso, 16:0 and 13:0 iso. The G+C content of the DNA ranged from 46.8 to 48.1 mol%. The strains were unpigmented, polarly flagellated, mesophilic, facultatively anaerobic and able to use nitrate, nitrite and sulphite as electron acceptors. Growth was observed at salinities from 0 to 6%, with an optimum between 1 and 3%. According to their morphology, physiology, fatty acid composition and 16S rRNA sequences, the described bacteria fitted well into the genus Shewanella, but could be easily distinguished from the Shewanella species described to date. Because of their capacity for vigorous denitrification, the name Shewanella denitrificans sp. nov. is suggested for the Baltic isolates, for which the type strain is OS217(T) (= DSM 15013(T) = LMG 21692(T)).

  12. Microbial Formation of Dimethyl Sulfide in Anoxic Sphagnum Peat

    PubMed Central

    Kiene, R. P.; Hines, M. E.

    1995-01-01

    Peat bogs dominated by Sphagnum spp. have relatively high areal rates of dimethyl sulfide (DMS) emission to the atmosphere. DMS was produced in anoxic slurries of Sphagnum peat with a linear time course and with an average rate of 40.4 (range, 22.0 to 68.6) nmol per liter of slurry (middot) day(sup-1) observed in nine batches of slurry. Methanethiol (MeSH) was produced at roughly similar rates over the typical 4- to 8-day incubations. DMS and MeSH production in these acidic (pH 4.2 to 4.6) peats were biological, as they were stopped completely by autoclaving and inhibited strongly by addition of antibiotics and 500 (mu)M chloroform. Endogenous DMS production may be due to the degradation of S-methyl-methionine, dimethyl sulfoxide, or methoxyaromatic compounds (e.g., syringic acid), each of which stimulated DMS formation when added at 5 to 10 (mu)M concentrations. However, on the basis of the high rates of thiol (MeSH and ethanethiol) methylation activity that we observed and the availability of endogenous MeSH, we suggest that methylation of MeSH is the major pathway leading to DMS formation in anaerobic peat. Solid-phase adsorption of MeSH plays a key role in its availability for biomethylation reactions. Additions of acetate (1.5 mM) or compounds which could cause acetate to accumulate (e.g., glucose, alanine, and 2-bromoethanesulfonate) suppressed DMS formation. It is likely that acetogenic bacteria are involved in DMS formation, but our data are insufficient to allow firm conclusions about the metabolic pathways or organisms involved. Our observations are the first which point to the methylation of MeSH as the major mechanism for endogenous DMS production in any environment. The rates of net DMS production observed are sufficient to explain the relatively high fluxes of DMS emitted to the atmosphere from Sphagnum sp.-dominated wetlands. PMID:16535080

  13. Pennsylvanian-Permian tectonism in the Great Basin: The Dry Mountain trough and related basins

    SciTech Connect

    Snyder, W.S.; Spinosa, C.; Gallegos, D.M. )

    1991-02-01

    Pennsylvanian-Permian tectonism affected the continental margin of western North America from the Yukon to the Mojave Desert. Specific signatures of this tectonism include local angular unconformities, regional disconformities, renewed outpouring of clastic debris from a reactivated Antler and related highlands, and development of deeper water basins with anoxic sediments deposited below wave base. The basins formed include Ishbel trough (Canada), the Wood River basin (Idaho), Cassia basin, Ferguson trough, Dry Mountain trough (all Nevada), and unnamed basins in Death Valley-Mojave Desert region. The Dry Mountain trough (DMT) was initiated during early Wolfcampian and received up to 1,200 m of sediment by the late Leonardian. The lower contact is a regional unconformity with the Ely Limestone, or locally with the Diamond Peak or Vinini formations. Thus, following a period of localized regional uplift that destroyed the Ely basin, portions of the uplifted and exposed shelf subsided creating the Dry Mountain trough. Evidence suggesting a tectonic origin for the DMT includes (1) high subsidence rates (60-140 m/m.y.); (2) renewed influx of coarse clastic debris from the Antler highlands: (3) possible pre-Early Permian folding, thrusting, and tilting within the highlands; and (4) differential subsidence within the Dry Mountain trough, suggesting the existence of independent fault blocks.

  14. New stratigraphic and isotopic record of the Toarcian Oceanic Anoxic Event from Hungary

    NASA Astrophysics Data System (ADS)

    Müller, Tamás; Price, Gregory; Bajnai, Dávid; Nyerges, Anita; Pálfy, József; May, Zoltán

    2016-04-01

    In the Early Toarcian (˜183 Ma) major global environmental changes took place in the ocean-atmosphere system, including the widely discussed Toarcian Oceanic Anoxic Event (T-OAE). This phenomenon is characterized by strong perturbation of the carbon-cycle and other geochemical systems. A peculiar negative carbon-isotope excursion (CIE) is a hallmark of the event, reflecting the injection of large amount of isotopically light carbon into the ocean-atmosphere system, possible due to dissociation of gas-hydrate from shelf areas. This observed negative CIE and a subsequent broad positive anomaly could be also key signals for chemostratigraphical correlation. In our study we obtained new, high-resolution organic carbon isotope data from the Réka Valley section of the Mecsek Mts. in southern Hungary. The Mecsek Basin was located at the European margin where a thick Lower Jurassic succession of siliciclastic hemipelagic sediments is interrupted by 13 m of organic-rich black shales in the Lower Toarcian. The δ13Corg data from the Réka Valley section is characterized by very negative values (averaging -32), with apparently cyclic fluctuation. The shape of the δ13Corg shows that a continuous and complete record can be found in the Réka Valley and also suggests mixed features between the carbon isotope record of the NW European and Tethyan regions. We have also carried out high resolution handheld XRF analyzes to study cyclostratigraphic signals in the section. The distribution of four elements Ti, Ca, Si and Al were used in our studies beside the δ13Corg data. The duration for the negative shift at Réka Valley, calculated from XRF signals, is either 550-750 kyr, 200-275 kyr or 116-158 kyr, based on 100 kyr short eccentricity, 36.6 kyr obliquity or 21.1 kyr precession signals, respectively. Several previous studies concluded that the most probable astronomical forcing factor during the CIE of the Toarcian OAE is obliquity. Therefore, we assume a duration around 200

  15. Thallium Isotopes Tracking Mn-Oxide Burial - A Proxy for Deoxygenation During Oceanic Anoxic Event 2

    NASA Astrophysics Data System (ADS)

    Ostrander, C.; Owens, J. D.; Nielsen, S.

    2015-12-01

    Thallium (Tl) is proving to be a useful paleoredox proxy given that the Tl isotope composition of seawater is highly dependent on the magnitude of manganese (Mn) oxide burial in the ocean. In turn, Mn oxides require oxygen at the sediment-water interface to precipitate, linking the Tl isotope cycle to ocean oxygenation. Currently, the marine residence time of Tl is ~20kyrs and the Tl isotope composition of seawater is invariant, which suggests Tl isotopes could be a global tracer of marine Mn-oxide burial. Importantly, recent research suggests sediments deposited under a euxinic water column faithfully record the Tl isotope value of the overlying oxic water column (e.g. Black Sea and Cariaco Basin). Therefore, analysis of organic-rich black shales may prove useful in evaluating the seawater Tl isotope composition of past oceans and, hence, large-scale burial of Mn-oxides and the extent of bottom water ocean oxygenation. A logical test for this proxy is during the well-studied Cenomanian-Turonian boundary event termed Oceanic Anoxic Event 2 (OAE-2) at ~94 Ma. It is known that the global extent of anoxia and euxinia increased during this event, however, to what extent global bottom water deoxygenation occured is unconstrained. If deep water deoxygenation occurred, it would be hypothesized that Mn-oxide precipitation would decrease, resulting in a positive Tl isotope excursion during OAE-2. We have analyzed the Tl isotope composition of organic-rich black shales from Site 1258 of the Ocean Drilling Program (ODP) spanning the period before, during, and after OAE-2. Based on Fe redox proxies, the entire section is euxinic and thus no Mn-oxides are present (i.e. no local redox changes). Before the event, Tl isotope compositions are similar or slightly heavier than modern seawater values. Just prior to the onset of OAE-2, a positive shift occurs and is maintained until recovery, slightly before the termination of the event. The shift to heavier values and subsequent

  16. Trace Metal Associations in an Anoxic Lake: the Relative Roles of Organic Carbon and Reduced Sulfur

    NASA Astrophysics Data System (ADS)

    Poulson Brucker, R.; McManus, J.; Severmann, S.; Owens, J.; Lyons, T.

    2008-12-01

    We investigate the geochemistry of the trace elements Mo, U, and Re in sediments from a transect through the chemocline of Lake Tanganyika, East Africa. In addition to these relatively shallow cores (70 to 330m), we present data from a longer core representing ~30,000 years of lake history, which was taken within the sulfidic waters that lie well below the chemocline (~900m water depth). Our goal is to establish a framework for trace metal deposition within the context of organic carbon and sulfur burial - two important carrier phases for these metals. Sediment organic carbon contents are high, generally between 5 and 10 wt% at the shallow sites, and up to 16 wt% in the deep basin. Despite the very low sulfate (~35 μM) and sulfide (~30 μM) concentrations in the lake water, sediment reduced sulfur contents are up to 1.5 wt% in the shallow sites and as high as 5 wt% in the deepest sediments. Sediment C:S ratios for all study sites are consistent with these sediments generally being sulfur limited. Sediment C:S ratios decrease from ~22, which agree well with previously published freshwater values, to ~6 with increasing site depth. The lower C:S ratios are more comparable to the marine value (2.8), and suggest that a considerable amount of organic carbon must be decomposing via sulfate reduction. C:S ratios in the deepest site are highly variable, with some even lower than the marine threshold. In light of the sedimentary organic carbon and sulfur data, trace metal distributions imply that U deposition is closely associated with organic carbon deposition and is independent of sulfur cycling. In contrast, Mo behavior suggests both an association with organic carbon as well as sulfur, but is subject to poor preservation where the sediment C:S ratios are highest. Rhenium accumulation only appears significant at the deepest most sulfur-rich site, and there is a close correspondence between Mo and Re distributions. These latter observations suggest that sulfur burial is

  17. Microbial oxidation of pyrite coupled to nitrate reduction in anoxic groundwater sediment.

    PubMed

    Jørgensen, Christian Juncher; Jacobsen, Ole Stig; Elberling, Bo; Aamand, Jens

    2009-07-01

    Although many areas in Denmark are intensively agricultured, the discharge of nitrate from groundwater aquifers to surface water is often lower than expected. In this study it is experimentally demonstrated that anoxic nitrate reduction in sandy sediment containing pyrite is a microbially mediated denitrification process with pyrite as the primary electron donor. The process demonstrates a temperature dependency (Q10) of 1.8 and could be completely inhibited by addition of a bactericide (NaN3). Experimentally determined denitrification rates show that more than 50% of the observed nitrate reduction can be ascribed to pyrite oxidation. The apparent zero-order denitrification rate in anoxic pyrite containing sediment at groundwater temperature has been determined to be 2-3 micromol NO3- kg(-1) day(-1). The in situ groundwater chemistry at the boundary between the redoxcline and the anoxic zone reveals that between 65 and 80% of nitrate reduction in the lower part of the redoxcline is due to anoxic oxidation of pyrite by nitrate with resulting release of sulfate. It is concluded that microbes can control groundwater nitrate concentrations by denitrification using primarily pyrite as electron donor at the oxic-anoxic boundary in sandy aquifers thus determining the position and downward progression of the redox boundary between nitrate-containing and nitrate-free groundwater.

  18. Nitrification and aerobic denitrification in anoxic-aerobic sequencing batch reactor.

    PubMed

    Alzate Marin, Juan C; Caravelli, Alejandro H; Zaritzky, Noemí E

    2016-01-01

    The aim of this study was to evaluate the feasibility of achieving nitrogen (N) removal using a lab-scale sequencing batch reactor (SBR) exposed to anoxic/aerobic (AN/OX) phases, focusing to achieve aerobic denitrification. This process will minimize emissions of N2O greenhouse gas. The effects of different operating parameters on the reactor performance were studied: cycle duration, AN/OX ratio, pH, dissolved oxygen concentration (DOC), and organic load. The highest inorganic N removal (NiR), close to 70%, was obtained at pH=7.5, low organic load (440mgCOD/(Lday)) and high aeration given by 12h cycle, AN/OX ratio=0.5:1.0 and DOC higher than 4.0mgO2/L. Nitrification followed by high-rate aerobic denitrification took place during the aerobic phase. Aerobic denitrification could be attributed to Tetrad-forming organisms (TFOs) with phenotype of glycogen accumulating organisms using polyhydroxyalkanoate and/or glycogen storage. The proposed AN/OX system constitutes an eco-friendly N removal process providing N2 as the end product.

  19. The metabolic consequences of repeated anoxic stress in the western painted turtle, Chrysemys picta bellii.

    PubMed

    Warren, Daniel E; Jackson, Donald C

    2017-01-01

    The painted turtle is known for its extreme tolerance to anoxia, but it is unknown whether previous experience with anoxic stress might alter physiological performance during or following a test bout of anoxia. Repeatedly subjecting 25°C-acclimated painted turtles to 2h of anoxic stress every other day for 19days (10 submergence bouts total) caused resting levels of liver glycogen to decrease by 17% and liver citrate synthase (CS) and cytochrome oxidase (COX) activities to increase by 33% and 112%, respectively. When the repeatedly submerged turtles were studied during a subsequent anoxic stress test, liver COX and CS activities decreased during anoxia to the same levels of naïve turtles, which were unchanged, and remained there throughout metabolic recovery. There were no effects of the repeated anoxia treatment on any of the other measured variables, which included lactate dehydrogenase and phosphofructokinase activities in liver, skeletal muscle, and ventricle, blood acid-base status, hemoglobin, hematocrit and plasma ion (Na, K, Ca, Mg, Cl) and metabolite concentrations (lactate, glucose, free-fatty acids), before, during, or after the anoxic stress test. We conclude that although painted turtles can show a physiological reaction to repeated anoxic stress, the changes appear to have no measurable effect on anaerobic physiological performance or ability to recover from anoxia. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Factors influencing deterioration of denitrification by oxygen entering an anoxic reactor through the surface.

    PubMed

    Plósz, Benedek Gy; Jobbágy, Andrea; Grady, C P Leslie

    2003-02-01

    The purpose of the paper is to examine the factors that influence the deterioration of denitrification in open anoxic reactors. For this investigation an ASM 1-based simulation model was developed and successfully applied to fit data from batch experiments carried out in lab-scale reactor vessels (uncovered and covered) using both clarified domestic wastewater and synthetic wastewater. Applying the verified model, simulation studies were performed to investigate the effects of available denitrifiable substrate, biomass concentration, oxygen transfer rate, and temperature on deterioration of denitrification in open anoxic reactors. It has been shown that oxygen entering an anoxic reactor through the surface may not just affect denitrification metabolically, but also kinetically, due to increased dissolved oxygen (DO) concentration exerting an inhibitory effect on the denitrification rate. When the exogenous substrate concentration in the reactor vessel is high enough for a high consumption rate, the DO concentration is kept low. The higher the biomass concentration, and thereby the consumption rate of endogenous substrate, the lower the DO concentration during the low-rate denitrification phase. At low substrate removal rates, decreasing temperature will cause the DO concentration in anoxic vessels to increase. The results suggest that assuring removal of available exogenous carbon source at high rate by staging of open anoxic bioreactors may significantly improve denitrification efficiency.

  1. Differential induction of pyruvate decarboxylase subunits and transcripts in anoxic rice seedlings.

    PubMed Central

    Rivoal, J; Thind, S; Pradet, A; Ricard, B

    1997-01-01

    In 2-d-old rice (Oryza sativa L.) seedlings subjected to anoxic stress, pyruvate decarboxylase (PDC) activity increased 9-fold during a 168-h period. A polyclonal PDC antiserum that recognized alpha- and beta-subunits was used to quantify PDC protein by an enzyme-linked immunosorbant assay and showed a 5.6-fold increase, suggesting that the anoxically induced enzyme has a higher specific activity than the PDC isoform present under normoxia. Immunoblot analysis showed that levels of both PDC subunits were induced by anoxia. Immunoprecipitation of proteins labeled in vivo during anoxic treatment demonstrated that the alpha-subunit was preferentially synthesized at the onset of anoxia. Two partial cDNAs, including a novel sequence, were cloned from a cDNA library made from seedlings subjected to anoxia for 6 h. Gene-specific probes used to quantify northern blots showed that two or three PDC mRNAs are differentially induced by anoxia in rice seedlings. Immunoprecipitation of in vitro translation products of mRNAs isolated a different times of anoxic treatment confirmed this findings Our results suggest that anoxic induction of rice PDC involves transcriptional and posttranscriptional regulation of gene expression as well as differences in enzyme characteristics. PMID:9232881

  2. Authigenic carbonate precipitation at the end-Guadalupian (Middle Permian) in China: Implications for the carbon cycle in ancient anoxic oceans

    NASA Astrophysics Data System (ADS)

    Saitoh, Masafumi; Ueno, Yuichiro; Isozaki, Yukio; Shibuya, Takazo; Yao, Jianxin; Ji, Zhansheng; Shozugawa, Katsumi; Matsuo, Motoyuki; Yoshida, Naohiro

    2015-12-01

    Carbonate precipitation is a major process in the global carbon cycle. It was recently proposed that authigenic carbonate (carbonate precipitated in situ at the sediment-water interface and/or within the sediment) played a major role in the carbon cycle throughout Earth's history. The carbon isotopic composition of authigenic carbonates in ancient oceans have been assumed to be significantly lower than that of dissolved inorganic carbon (DIC) in seawater, as is observed in the modern oceans. However, the δ13Ccarb values of authigenic carbonates in the past has not been analyzed in detail. Here, we report authigenic carbonates in the uppermost Guadalupian (Middle Permian) rocks at Chaotian, Sichuan, South China. Monocrystalline calcite crystals <20 mm long are common in the black mudstone/chert sequence that was deposited on a relatively deep anoxic slope/basin along the continental margin. Textures of the crystals indicate in situ precipitation on the seafloor and/or within the sediments. The calcite precipitation corresponds stratigraphically with denitrification and sulfate reduction in the anoxic deep-water mass, as indicated by previously reported nitrogen and sulfur isotope records, respectively. Relatively high δ13Ccarb values of the authigenic carbonates (largely -1 ‰) compared with those of organic matter in the rocks (ca. -26 ‰) suggest that the main carbon source of the carbonates was DIC in the water column. The calcite crystals precipitated in an open system with respect to carbonate, possibly near the sediment-water interface rather than deep within the sediments. The δ13Ccarb values of the carbonates were close to the δ13CDIC value of seawater due to mixing of 13C-depleted remineralized organic carbon (that was released into the water column by the water-mass anaerobic respiration) with the large DIC pool in the oceans. Our results imply that δ13Ccarb values of authigenic carbonates in the anoxic oceans might have been systematically

  3. Live (Rose-bengal stained) foraminifera from deep-sea anoxic salt brine in the Eastern Mediterranean: toward understanding limit of life for single-celled eukaryotes (foraminifera)

    NASA Astrophysics Data System (ADS)

    Kitazato, H.; Ohkawara, N.; Iwasaki, A.; Nomaki, H.; Akoumianaki, I.; Tokuyama, H.

    2012-04-01

    What is a limit of life for the eukaryotes? Eukaryotes are thought to adapt and evolve under oxic environmental conditions. Recently, there are many exceptions for this hypothesis, as many eukaryotes including metazoan groups are found in anoxic environmental conditions. We found many rose-bengal stained foraminifera from a deep-hypersaline anoxic basin (DHAB) in the eastern Mediterranean. During KH06-04 cruise, we conducted oceanographic research at Medée Lake, the largest DHAB, that is located 100km southwest of Crete Island in the eastern Mediterranean. The lake situates at 2920m in water depth. Depth of saline water is 120m in maximum. Both water and sediment samplings were carried out both with Niskin bottles and multiple corer attached to camera watching sampling system at three sites, inside of the lake (CS), the edge of the lake (OMS) and the normal deep-sea floor (RS). Temperature, salinity, and dissolved oxygen concentrations at central saline lake are 15.27 oC, 328PSU, and 0.0 ml/L, respectively. Strong smell of hydrogen sulfide was detected from the lake sediment. Subsamples were conducted for multiple core samples using 3 subcores(φ 2.9cm) from each core tube (φ 8.2cm). Sediment samples were fixed with 4% formalin Rose Bengal solution on board. In laboratory, samples were washed with 32μm sieve. Rose Bengal stained specimens were picked under binocular stereomicroscope (Zeiss Stemi SV11) for surface 0.5cm layer, and identified with inverted microscope (Nikon ECLIPSE TE300). In total, 26 species belonging to 9 genera were identified from three sites. Six species belonging to two genera were identified in the center of the salt brine. Only a few species are common among three sites, even though the numbers of common species were 10 between OMS and RS sites. In DHAB, spherical organic-walled species, such as allogromiid and psammosphaerid, are dominant. In contrast, tube-like chitinous foraminifera, such as Resigella, Conicotheca and Nodellum, are

  4. Enhanced biological nutrient removal in sequencing batch reactors operated as static/oxic/anoxic (SOA) process.

    PubMed

    Xu, Dechao; Chen, Hongbo; Li, Xiaoming; Yang, Qi; Zeng, Tianjing; Luo, Kun; Zeng, Guangming

    2013-09-01

    An innovative static/oxic/anoxic (SOA) activated sludge process characterized by static phase as a substitute for conventional anaerobic stage was developed to enhance biological nutrient removal (BNR) with influent ammonia of 20 and 40 mg/L in R1 and R2 reactors, respectively. The results demonstrated that static phase could function as conventional anaerobic stage. In R1 lower influent ammonia concentration facilitated more polyphosphate accumulating organisms (PAOs) growth, but secondary phosphorus release occurred due to NOx(-) depletion during post-anoxic period. In R2, however, denitrifying phosphorus removal proceeded with sufficient NOx(-). Both R1 and R2 saw simultaneous nitrification-denitrification. Glycogen was utilized to drive post-denitrification with denitrification rates in excess of typical endogenous decay rates. The anoxic stirring duration could be shortened from 3 to 1.5h to avoid secondary phosphorus release in R1 and little adverse impact was found on nutrients removal in R2.

  5. Influence of an oxic settling anoxic system on biomass yield, protozoa and filamentous bacteria.

    PubMed

    Rodriguez-Perez, Santiago; Fermoso, Fernando G

    2016-01-01

    An oxic settling anoxic system coupled with an activated sludge process has been studied to reduce sewage sludge production. The reduction of sludge yield, excess sludge production and active biomass yield were 51.7%, 52.9% and 67.1%, respectively, compared with the control system. The oxic reactor of the oxic settling anoxic system, even with a lower active biomass concentration than the oxic reactor of control system, showed a higher metabolic activity in their active biomass. Diversity and crawling ciliates group have been shown as promising bioindicators of active biomass yield reduction. The identification of floc-forming bacteria in the control system suggested that oxic settling anoxic system will improve settling properties compared to a Conventional Activated Sludge process.

  6. Inhibition of Sporosarcina pasteurii under anoxic conditions: implications for subsurface carbonate precipitation and remediation via ureolysis.

    PubMed

    Martin, Derek; Dodds, Kevin; Ngwenya, Bryne T; Butler, Ian B; Elphick, Stephen C

    2012-08-07

    The use of Sporosarcina pasteurii to precipitate calcium carbonate in the anoxic subsurface via ureolysis has been proposed for reducing porosity and sealing fractures in rocks. Here we show that S. pasteurii is unable to grow anaerobically and that the ureolytic activity previously shown under anoxic conditions is a consequence of the urease enzyme already present in the cells of the aerobically grown inoculum. The implications are discussed, suggesting that de novo synthesis of urease under anoxic conditions is not possible and that ureolysis may decline over time without repeated injection of S. pasteurii as the urease enzyme degrades and/or becomes inhibited. Augmentation with a different ureolytic species that is able to grow anaerobically or stimulation of natural communities may be preferable for carbonate precipitation over the long term.

  7. A critical comparison of the measured solubilities of ferrous sulphide in natural waters

    NASA Astrophysics Data System (ADS)

    Davison, W.

    1980-06-01

    A critical review of activity coefficients and calculation procedures appropriate to the numerical definition of the solubility of ferrous sulfide is presented. Past difficulties encountered when comparing results from waters of different ionic strengths are discussed and a new operational solubility product, which overcomes some of these problems, is defined. The available data for known anoxic basins are re-calculated and presented in this revised form. Analysis of the data suggests that the residence time in the water body of the particulate ferrous sulfide phase may influence the solubility. In a deep basin, such as the Black Sea, there may be a long residence time which allows the particulate matter to age and become less soluble. Very shallow basins do not allow substantial ageing to occur. It is probable that the anoxic waters of Lake Nitinat and the Cariaco Trench are not saturated with respect to ferrous sulfide. The inadequacy of using filtration for distinguishing soluble and hence ferrous iron is highlighted and polarographic or well defined colorimetric procedures are recommended for future work so that results may be unambiguously interpreted.

  8. South Atlantic sag basins: new petroleum system components

    SciTech Connect

    Henry, S.G. Mohriak, W.U.; Mello, M.R.

    1996-08-01

    Newly discovered pre-salt source rocks, reservoirs and seals need to be included as components to the petroleum systems of both sides of the South Atlantic. These new components lie between the pre-salt rift strata and the Aptian salt layers, forming large, post-rift, thermal subsidence sag basins. These are differentiated from the older rift basins by the lack of syn-rift faulting and a reflector geometry that is parallel to the base salt regional unconformity rather than to the Precambrian basement. These basins are observed in deep water regions overlying areas where both the mantle and the crust have been involved in the extension. This mantle involvement creates post-rift subsiding depocenters in which deposition is continuous while proximal rift-phase troughs with little or no mantle involvement are bypassed and failed to accumulate potential source rocks during anoxic times. These features have been recognized in both West African Kwanza Basin and in the East Brasil Rift systems. The pre-salt source rocks that are in the West African sag basins were deposited in lacustrine brackish to saline water environment and are geochemically distinct from the older, syn-rift fresh to brackish water lakes, as well as from younger, post-salt marine anoxic environments of the drift phase. Geochemical analyses of the source rocks and their oils have shown a developing source rock system evolving from isolated deep rift lakes to shallow saline lakes, and culminating with the infill of the sag basin by large saline lakes to a marginally marine restricted gulf. Sag basin source rocks may be important in the South Atlantic petroleum system by charging deep-water prospects where syn-rift source rocks are overmature and the post-salt sequences are immature.

  9. Survival and Recovery of Methanotrophic Bacteria Starved Under Oxic and Anoxic Conditions

    NASA Technical Reports Server (NTRS)

    Roslev, Peter; King, Gary M.

    1994-01-01

    The effects of carbon deprivation on survival of methanotrophic bacteria were compared in cultures incubated in the presence and absence of oxygen in the starvation medium. Survival and recovery of the examined methanotrophs were generally highest for cultures starved under anoxic conditions as indicated by poststarvation measurements of methane oxidation, tetrazolium salt reduction, plate counts, and protein synthesis. Methylosinus trichosporium OB3b survived up to 6 weeks of carbon deprivation under anoxic conditions while maintaining a physiological state that allowed relatively rapid (hours) methane oxidation after substrate addition. A small fraction of cells starved under oxic and anoxic conditions (4 and 10%, respectively) survived more than 10 weeks but required several days for recovery on plates and in liquid medium. A non-spore-forming methanotroph, strain WP 12, displayed 36 to 118% of its initial methane oxidation capacity after 5 days of carbon deprivation. Oxidation rates varied with growth history prior to the experiments as well as with starvation conditions. Strain WP 12 starved under anoxic conditions showed up to 90% higher methane oxidation activity and 46% higher protein production after starvation than did cultures starved under oxic conditions. Only minor changes in biomass and niorpholow were seen for methanotrophic bacteria starved tinder anoxic conditions. In contrast, starvation under oxic conditions resulted in morphology changes and an initial 28 to 35% loss of cell protein. These data suggest that methanotrophic bacteria can survin,e carbon deprivation under anoxic conditions by using maintenance energy derived Solelyr from an anaerobic endogenous metabolism. This capability could partly explain a significant potential for methane oxidation in environments not continuously, supporting aerobic methanotrophic growth.

  10. Chemical and physical speciation of mercury in Offatts Bayou: A seasonally anoxic bayou in Galveston Bay

    SciTech Connect

    Han, Seunghee; Lehman, Ronald D.; Choe, Key-Young; Gill, Gary A.

    2007-07-01

    A chemical equilibrium model was used to predict the solution speciation of dissolved mercury (Hg) in the stratified water column of Offatts Bayou, a subestuary in Galveston Bay, Texas, which undergoes seasonal anoxia in bottom waters. Chemical equilibrium modeling was conducted using conditional stability constants and concentrations of Hg-complexing organic ligands experimentally determined by competitive ligand equilibration methods. Dissolved Hg complexation was dominated by interactions with sulfide and dissolved organic matter (DOM) (HOHgHS0, HOHgHS(DOM), HgSHS2, and HgS 2{ 2 ) at all depths. Sulfide and glutathione competed for methylmercury (MeHg) complexation in oxic layers; in anoxic waters, sulfide complexation dominated MeHg speciation. The particle–water distribution coefficient (Kd) of Hg decreased in the anoxic layer of the water column, where the dissolved sulfide concentration increased, providing evidence that sulfide complexation influences the solubility of Hg. The solubility of MeHg was elevated in the anoxic as compared to the oxic layers, and this distributional feature was coincident with a change in the solution speciation of dissolved MeHg from glutathione/sulfide complexation in the oxic layers to a predominantly sulfide complexation in the anoxic layers. Maximum enrichment of Hg, MeHg, and iron (Fe) in suspended particulate matter was observed in the lower layer of the pycnocline, most likely resulting from formation of insoluble Fe oxide, which scavenged dissolved Hg sulfide and MeHg-sulfide species. The concomitant decrease in dissolved inorganic Hg, Fe, and sulfide in the anoxic layers is suggested to result from scavenging of inorganic Hg by FeS, which is in accordance with the Hg speciation model. Overall, Hg cycling in the water column of Offatts Bayou was associated with sulfide and DOM complexation, Fe dissolution/precipitation, water column production of MeHg, and/or efflux of MeHg from anoxic sediment.

  11. Survival and Recovery of Methanotrophic Bacteria Starved Under Oxic and Anoxic Conditions

    NASA Technical Reports Server (NTRS)

    Roslev, Peter; King, Gary M.

    1994-01-01

    The effects of carbon deprivation on survival of methanotrophic bacteria were compared in cultures incubated in the presence and absence of oxygen in the starvation medium. Survival and recovery of the examined methanotrophs were generally highest for cultures starved under anoxic conditions as indicated by poststarvation measurements of methane oxidation, tetrazolium salt reduction, plate counts, and protein synthesis. Methylosinus trichosporium OB3b survived up to 6 weeks of carbon deprivation under anoxic conditions while maintaining a physiological state that allowed relatively rapid (hours) methane oxidation after substrate addition. A small fraction of cells starved under oxic and anoxic conditions (4 and 10%, respectively) survived more than 10 weeks but required several days for recovery on plates and in liquid medium. A non-spore-forming methanotroph, strain WP 12, displayed 36 to 118% of its initial methane oxidation capacity after 5 days of carbon deprivation. Oxidation rates varied with growth history prior to the experiments as well as with starvation conditions. Strain WP 12 starved under anoxic conditions showed up to 90% higher methane oxidation activity and 46% higher protein production after starvation than did cultures starved under oxic conditions. Only minor changes in biomass and niorpholow were seen for methanotrophic bacteria starved tinder anoxic conditions. In contrast, starvation under oxic conditions resulted in morphology changes and an initial 28 to 35% loss of cell protein. These data suggest that methanotrophic bacteria can survin,e carbon deprivation under anoxic conditions by using maintenance energy derived Solelyr from an anaerobic endogenous metabolism. This capability could partly explain a significant potential for methane oxidation in environments not continuously, supporting aerobic methanotrophic growth.

  12. Survival and Recovery of Methanotrophic Bacteria Starved under Oxic and Anoxic Conditions †

    PubMed Central

    Roslev, Peter; King, Gary M.

    1994-01-01

    The effects of carbon deprivation on survival of methanotrophic bacteria were compared in cultures incubated in the presence and absence of oxygen in the starvation medium. Survival and recovery of the examined methanotrophs were generally highest for cultures starved under anoxic conditions as indicated by poststarvation measurements of methane oxidation, tetrazolium salt reduction, plate counts, and protein synthesis. Methylosinus trichosporium OB3b survived up to 6 weeks of carbon deprivation under anoxic conditions while maintaining a physiological state that allowed relatively rapid (hours) methane oxidation after substrate addition. A small fraction of cells starved under oxic and anoxic conditions (4 and 10%, respectively) survived more than 10 weeks but required several days for recovery on plates and in liquid medium. A non-spore-forming methanotroph, strain WP 12, displayed 36 to 118% of its initial methane oxidation capacity after 5 days of carbon deprivation. Oxidation rates varied with growth history prior to the experiments as well as with starvation conditions. Strain WP 12 starved under anoxic conditions showed up to 90% higher methane oxidation activity and 46% higher protein production after starvation than did cultures starved under oxic conditions. Only minor changes in biomass and morphology were seen for methanotrophic bacteria starved under anoxic conditions. In contrast, starvation under oxic conditions resulted in morphology changes and an initial 28 to 35% loss of cell protein. These data suggest that methanotrophic bacteria can survive carbon deprivation under anoxic conditions by using maintenance energy derived solely from an anaerobic endogenous metabolism. This capability could partly explain a significant potential for methane oxidation in environments not continuously supporting aerobic methanotrophic growth. PMID:16349336

  13. Involvement of plasma membrane H+-ATPase in anoxic elongation of stems in pondweed (Potamogeton distinctus) turions.

    PubMed

    Koizumi, Yayoi; Hara, Yoshinao; Yazaki, Yoshiaki; Sakano, Katsuhiro; Ishizawa, Kimiharu

    2011-04-01

    • Pondweed (Potamogeton distinctus) turions can elongate in the absence of O(2). Alcoholic fermentation serves to produce energy for anoxic elongation via the breakdown of starch stored in cells. However, the mechanism of cell growth during anoxic elongation is not fully understood. • Changes in pH, H(+) equivalent and lactate content of the incubation medium were measured during anoxic elongation. The effects of fusicoccin (FC), indole-3-acetic acid (IAA), vanadate, erythrosine B and K(+) channel blockers on anoxic elongation were examined. Cytoplasmic pH and vacuolar pH were measured by (31)P nuclear magnetic resonance (NMR) spectroscopy. • Acidification of the incubation medium occurred during anoxic elongation. The contribution of CO(2) and lactic acid was not sufficient to explain the acidification. FC and IAA enhanced the elongation of stem segments. Vanadate and erythrosine B inhibited anoxic elongation. Acid growth of notched segments was observed. The activity of plasma membrane H(+)-ATPase extracted from pondweed turions was increased slightly in anoxic conditions, but that from pea epicotyls sensitive to anoxic conditions was decreased by incubation in anoxic conditions. Both the cytoplasmic pH and vacuolar pH of pondweed turion cells chased by (32)P NMR spectroscopy were stabilized during a short period < 3 h after anoxic conditions. • We propose that the enhancement of H(+) extrusion by anoxic conditions induces acidification in the apoplast and may contribute to the stabilization of pH in the cytoplasm. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

  14. BASINS Publications

    EPA Pesticide Factsheets

    Although BASINS has been in use for the past 10 years, there has been limited modeling guidance on its applications for complex environmental problems, such as modeling impacts of hydro modification on water quantity and quality.

  15. Basin analysis

    SciTech Connect

    Lerche, I. )

    1989-01-01

    The exploration for oil is a high-risk game. Worldwide drilling success is around 5-10%, the average cost of drilling is around $1000 a foot, and the average well is now around 15,000 feet deep. Over the years, two fundamental avenues of attack have been developed: methods designed to locate oil in situ from direct measurement ahead of the drill and methods focusing on the dynamic evolution of a sedimentary basin in relation to the timing of hydrocarbon generation, migration, and accumulation to provide an assessment of which areas in a basin might be the most prospective for oil accumulations today. This volume addresses the problem of quantitative basin analysis in relation to oil accumulations. Emphasis is placed on the uncertainties and resolution limits of basin analysis given constraints derived from surface and downhole data and the sensitivity to model input parameters and assumptions.

  16. Callisto basin

    NASA Technical Reports Server (NTRS)

    1979-01-01

    This picture of a multi=ring basin on Callisto was taken the morning of March 6, 1979, from a distance of about 200,000 km. The complicated circular structure seen at left center is similar to the large circular impact basins that dominate the surface of the Earth's moon and also the planet Mercury. The inner parts of these basins are generally surrounded by radially lineated ejecta and several concentric mountainous ring structures that are thought to form during the impact event. This multi-ring basin on Callisto consists of light floored central basin some 300 k m in diameter surrounded by at least eight to ten discontinuous rhythmically spaced ridges. No radially lineated ejecta can be seen. The ring structures on Moon and Mercury have been likened to ripples produced on a pond by a rock striking the water. The great number of rings observed around this basin on Callisto is consistent with its low planetary density and probable low internal strength. JPL manages and controls the Voyager project for NASA's Office of Space Science.

  17. Parana basin

    SciTech Connect

    Zalan, P.V.; Wolff, S.; Conceicao, J.C.J.; Vieira, I.S.; Astolfi, M.A.; Appi, V.T.; Zanotto, O.; Neto, E.V.S.; Cerqueira, J.R.

    1987-05-01

    The Parana basin is a large intracratonic basin in South America, developed entirely on continental crust and filled with sedimentary and volcanic rocks ranging in age from Silurian to Cretaceous. It occupies the southern portion of Brazil (1,100,000 km/sup 2/ or 425,000 mi/sup 2/) and the eastern half of Paraguay (100,000 km/sup 2/ or 39,000 mi/sup 2/); its extension into Argentina and Uruguay is known as the Chaco-Parana basin. Five major depositional sequences (Silurian, Devonian, Permo-Carboniferous, Triassic, Juro-Cretaceous) constitute the stratigraphic framework of the basin. The first four are predominantly siliciclastic in nature, and the fifth contains the most voluminous basaltic lava flows of the planet. Maximum thicknesses are in the order of 6000 m (19,646 ft). The sequences are separated by basin wide unconformities related in the Paleozoic to Andean orogenic events and in the Mesozoic to the continental breakup and sea floor spreading between South America and Africa. The structural framework of the Parana basin consists of a remarkable pattern of criss-crossing linear features (faults, fault zones, arches) clustered into three major groups (N45/sup 0/-65/sup 0/W, N50/sup 0/-70/sup 0/E, E-W). The northwest- and northeast-trending faults are long-lived tectonic elements inherited from the Precambrian basement whose recurrent activity throughout the Phanerozoic strongly influenced sedimentation, facies distribution, and development of structures in the basin. Thermomechanical analyses indicate three main phases of subsidence (Silurian-Devonian, late Carboniferous-Permian, Late Jurassic-Early Cretaceous) and low geothermal gradients until the beginning of the Late Jurassic Permian oil-prone source rocks attained maturation due to extra heat originated from Juro-Cretaceous igneous intrusions. The third phase of subsidence also coincided with strong tectonic reactivation and creation of a third structural trend (east-west).

  18. The enemy at the gates. Ca2+ entry through TRPM7 channels and anoxic neuronal death.

    PubMed

    Nicotera, Pierluigi; Bano, Daniele

    2003-12-26

    In brain ischemia, gating of postsynaptic glutamate receptors is thought to initiate Ca2+ overload leading to excitotoxic neuronal death. In this issue, Aarts and colleagues describe a novel mechanism, whereby gating of TRPM7, a Ca2+-permeable nonselective cation channel, mediates Ca2+ overload and demise of anoxic neurons.

  19. Volcanic triggering of a biogeochemical cascade during Oceanic Anoxic Event 2

    NASA Astrophysics Data System (ADS)

    Adams, Derek D.; Hurtgen, Matthew T.; Sageman, Bradley B.

    2010-03-01

    During the Cretaceous period (~145-65million years ago), there were several periods of global ocean anoxia, each lasting less than onemillion years. These events, known as ocean anoxic events, were marked by significant increases in organic carbon burial, and are generally attributed to increased primary productivity in surface waters. The details underpinning the initiation, maintenance and termination of these events, however, remain equivocal. Here we present sulphur isotope data spanning the Ocean Anoxic Event 2 (about 94.5million years ago) from sedimentary rocks in Colorado that were formed in the Western Interior Seaway; this seaway ran north-south, splitting North America during the Cretaceous. Sulphate levels increased rapidly from relatively low background levels at the onset of the event, most likely from the release of sulphur by massive volcanism, and fell during the anoxic event. We infer that the input of sulphate facilitated increased carbon remineralization, which enhanced nutrient recycling and increased global primary productivity, eventually resulting in widespread ocean anoxia. Our scenario indicates that Ocean Anoxic Event 2may have persisted until sulphate levels were stabilized by the formation and burial of the sulphur mineral pyrite, which returned primary productivity to background levels. We suggest that fluctuations in sulphate levels may have regulated the marine carbon cycle during past periods of low oceanic sulphate concentration.

  20. Effect of induced hypercapnia on anaerobic metabolic rate of anoxic musk turtles.

    PubMed

    Jackson, D C; Wasser, J S; Silver, R B

    1988-06-01

    To evaluate the possible effect of induced hypercapnia on anaerobic metabolic rate during anoxia, musk turtles (Sternotherus odoratus) were submerged in N2-equilibrated water at 10 degrees C for 3 days either with (anoxic hypercapnic) or without (anoxic normocapnic) elevated aquatic PCO2 (30-40 Torr). Control animals had access to air at 10 degrees C. Plasma [lactate] was significantly higher (P less than 0.01) in the normocapnic [59.4 +/- 7.4 (SD) mM; n = 22] than in the hypercapnic (47.4 +/- 8.5 mM; n = 19) anoxic turtles, although the hypercapnic turtles had lower blood pH (P less than 0.05). Plasma ion concentrations (Na, K, Cl, Ca, and Mg), however, were no different in the two groups, although all values other than Na were different from control. In some of the animals, [lactate] and [glycogen] (per g wet wt) of skeletal muscle, heart, and liver were measured in addition to blood acid-base values and lactate. Tissue lactates, although significantly elevated from control, and glycogens, although (with the exception of skeletal muscle) significantly reduced from control, were no different in the two anoxic groups. We suggest that these tissue data are more valid indicators of anaerobic metabolic rate than is plasma lactate and therefore conclude that induced hypercapnia does not significantly depress anaerobiosis in musk turtles at 10 degrees C.

  1. Open Questions on the Origin of Life at Anoxic Geothermal Fields

    NASA Astrophysics Data System (ADS)

    Mulkidjanian, Armen Y.; Bychkov, Andrew Yu.; Dibrova, Daria V.; Galperin, Michael Y.; Koonin, Eugene V.

    2012-10-01

    We have recently reconstructed the `hatcheries' of the first cells by combining geochemical analysis with phylogenomic scrutiny of the inorganic ion requirements of universal components of modern cells (Mulkidjanian et al. Proc Natl Acad Sci U S A 109:E821-830, 2012). These ubiquitous, and by inference primordial, proteins and functional systems show affinity to and functional requirement for K+, Zn2+, Mn2+, and phosphate. Thus, protocells must have evolved in habitats with a high K+/Na+ ratio and relatively high concentrations of Zn, Mn and phosphorous compounds. Geochemical reconstruction shows that the ionic composition conducive to the origin of cells could not have existed in marine settings but is compatible with emissions of vapor-dominated zones of inland geothermal systems. Under an anoxic, CO2-dominated atmosphere, the ionic composition of pools of cool, condensed vapor at anoxic geothermal fields would resemble the internal milieu of modern cells. Such pools would be lined with porous silicate minerals mixed with metal sulfides and enriched in K+ ions and phosphorous compounds. Here we address some questions that have appeared in print after the publication of our anoxic geothermal field scenario. We argue that anoxic geothermal fields, which were identified as likely cradles of life by using a top-down approach and phylogenomics analysis, could provide geochemical conditions similar to those which were suggested as most conducive for the emergence of life by the chemists who pursuit the complementary bottom-up strategy.

  2. Community Shift from Phototrophic to Chemotrophic Sulfide Oxidation following Anoxic Holomixis in a Stratified Seawater Lake

    PubMed Central

    Korlević, Marino; Berg, Jasmine S.; Bura-Nakić, Elvira; Ciglenečki, Irena; Amann, Rudolf; Orlić, Sandi

    2014-01-01

    Most stratified sulfidic holomictic lakes become oxygenated after annual turnover. In contrast, Lake Rogoznica, on the eastern Adriatic coast, has been observed to undergo a period of water column anoxia after water layer mixing and establishment of holomictic conditions. Although Lake Rogoznica's chemistry and hydrography have been studied extensively, it is unclear how the microbial communities typically inhabiting the oxic epilimnion and a sulfidic hypolimnion respond to such a drastic shift in redox conditions. We investigated the impact of anoxic holomixis on microbial diversity and microbially mediated sulfur cycling in Lake Rogoznica with an array of culture-independent microbiological methods. Our data suggest a tight coupling between the lake's chemistry and occurring microorganisms. During stratification, anoxygenic phototrophic sulfur bacteria were dominant at the chemocline and in the hypolimnion. After an anoxic mixing event, the anoxygenic phototrophic sulfur bacteria entirely disappeared, and the homogeneous, anoxic water column was dominated by a bloom of gammaproteobacterial sulfur oxidizers related to the GSO/SUP05 clade. This study is the first report of a community shift from phototrophic to chemotrophic sulfide oxidizers as a response to anoxic holomictic conditions in a seasonally stratified seawater lake. PMID:25344237

  3. Electrophysiological Correlates of Deficient Encoding in a Case of Post-Anoxic Amnesia

    ERIC Educational Resources Information Center

    Lehmann, Sandra; Morand, Stephanie; James, Clara; Schnider, Armin

    2007-01-01

    Little is known about the initial stages of information processing in amnesia as compared to normal memory. In this study, we used electrical spatiotemporal mapping to compare cortical activation during encoding and recognition in a 56-year-old patient with severe, chronic post-anoxic amnesia and an age-matched control group. Event-related…

  4. Factors predicting functional and cognitive recovery following severe traumatic, anoxic, and cerebrovascular brain damage.

    PubMed

    Smania, Nicola; Avesani, Renato; Roncari, Laura; Ianes, Patrizia; Girardi, Paolo; Varalta, Valentina; Gambini, Maria Grazia; Fiaschi, Antonio; Gandolfi, Marialuisa

    2013-01-01

    To compare demographic data, clinical data, and rate of functional and cognitive recovery in patients with severe traumatic, cerebrovascular, or anoxic acquired brain injury (ABI) and to identify factors predicting discharge home. Three hundred twenty-nine patients with severe ABI (192 with traumatic, 104 with cerebrovascular, and 33 with anoxic brain injury). Longitudinal prospective study of inpatients attending the intensive Rehabilitation Department of the "Sacro Cuore" Don Calabria Hospital (Negrar, Verona, Italy). Etiology, sex, age, rehabilitation admission interval, rehabilitation length of stay, discharge destination, Glasgow Coma Scale, Disability Rating Scale (DRS), Glasgow Outcome Scale, Levels of Cognitive Functioning, and Functional Independence Measure. Predominant etiology was traumatic; male gender was prevalent in all the etiologic groups; patients with traumatic brain injury were younger than the patients in the other groups and had shorter rehabilitation admission interval, greater functional and cognitive outcomes on all considered scales, and a higher frequency of returning home. Patients with anoxic brain injury achieved the lowest grade of functional and cognitive recovery. Age, etiology, and admission DRS score predicted return home. Patients with traumatic brain injury achieved greater functional and cognitive improvements than patients with cerebrovascular and anoxic ABI. Age, etiology, and admission DRS score can assist in predicting discharge destination.

  5. ENVIRONMENTAL FACTORS INFLUENCING METHANOGENESIS IN A SHALLOW ANOXIC AQUIFER: A FIELD AND LABORATORY STUDY

    EPA Science Inventory

    The environmental factors influencing methanogenesis in a shallow anoxic aquifer were probed in a combined field and laboratory study. Field data collected over a year revealed that in situ rates of methane production were depressed in winter and elevated in summer. Over the same...

  6. Electrophysiological Correlates of Deficient Encoding in a Case of Post-Anoxic Amnesia

    ERIC Educational Resources Information Center

    Lehmann, Sandra; Morand, Stephanie; James, Clara; Schnider, Armin

    2007-01-01

    Little is known about the initial stages of information processing in amnesia as compared to normal memory. In this study, we used electrical spatiotemporal mapping to compare cortical activation during encoding and recognition in a 56-year-old patient with severe, chronic post-anoxic amnesia and an age-matched control group. Event-related…

  7. Oxic and anoxic conditions affect arsenic (As) accumulation and arsenite transporter expression in rice.

    PubMed

    Wu, Chuan; Huang, Liu; Xue, Sheng-Guo; Pan, Wei-Song; Zou, Qi; Hartley, William; Wong, Ming-Hung

    2017-02-01

    Arsenic (As) exposure from rice consumption has now become a global health issue. This study aimed to investigate the effects of rice rhizosphere oxic conditions on silicate transporter (responsible for arsenite transportation) expressions, and on As accumulation and speciation in four rice genotypes, including two hybrid genotypes (Xiangfengyou9, Shenyou9586) and two indica subspecies (Xiangwanxian17, Xiangwanxian12). Oxic and anoxic treatments have different effects on root length (p < 0.001) and weight (p < 0.05). Total As concentrations in roots were dramatically lower in oxic treatments (88.8-218 mg/kg), compared to anoxic treatments (147-243 mg/kg) (p < 0.001). Moreover, root and shoot arsenite concentrations in oxic treatments were lower than that in anoxic treatments in arsenite treatments. The relative abundance of silicate transporter expressions displayed a trend of down-regulation in oxic treatments compared to anoxic treatments, especially significantly different for Xiangwanxian17, Xiangwanxian12 in Lsi1 expressions (p < 0.05), Xiangfengyou9, Shenyou9586, Xiangwanxian17 in Lsi2 expressions (p < 0.05). However, there were no significant differences of transporter expressions in different As treatments and genotypes. It may be a possible reason for low As accumulation in rice growing aerobically compared to flooded condition and a potential route to reduce the health risk of As in rice.

  8. Modeling anoxic aggregates in the ocean - implications for nitrogen, sulfur and trace metal cycling

    NASA Astrophysics Data System (ADS)

    Bianchi, D.; Weber, T. S.; Deutsch, C.

    2016-02-01

    Anoxic conditions are uncommon in the open ocean, and mostly confined to the cores of oxygen minimum zones (OMZs). When oxygen runs out, a suite of alternative electron acceptors are used, leading to denitrification and, rarely in open waters, sulfate reduction. Anoxic conditions have been shown to develop inside millimeter-scale organic particles and aggregates, establishing microscale gradients that could sustain diverse microbial communities along a sequence of redox niches. We develop a model of the biogeochemistry of anoxic aggregates that includes aerobic and anaerobic reactions in a diffusion-limited environment, and present analytical and numerical solutions for the conditions that allow denitrification and sulfate reduction inside aggregates. The model is applied to realistic size spectra of particles sinking through the water column, and used to estimate the potential for particle-bound denitrification and sulfate reduction in the global ocean. We show that anoxia inside aggregates may be common throughout low oxygen waters, extending the niche of denitrifying metabolisms beyond fully anoxic zones. In the OMZ cores, aggregates can sustain pockets of sulfate reduction in otherwise non-sulfidic waters, depending on ambient nitrate concentrations, particle respiration rates, and other factors. We further discuss the implications for nitrogen, sulfur and trace metal cycling in the ocean.

  9. Genesis of selected Triassic basins on the Italian peninsula: Their origin and hydrocarbon potential

    SciTech Connect

    Rigo de Righi, L.L.

    1990-01-01

    The paleogeographic evolution of the southern Alpine Lombardy Basin, the Central Adriatic Pescara Basin, and the Sicilian Ragusa Basin in Italy document the depositional and structural evolution of the Mesozoic Apulian Plate. These Mesozoic basins formed as a response to the Jurassic opening of the Tethyan Ocean. Due to their respective position in relation to the Mesozoic Tethyan spreading center, each of the three basins formed with unique structural entities. The Mesozoic paleogeographic history of the Lombardy Basin suggests that it initially formed a continental arc basin on the northern margin of the Apulian Plate. As Tethyan rifting progressed, the basin subsequently evolved into an Early Jurassic passive continental rift margin. The Pescara Basin, with its central Apulian paleogeographic location, developed as a Tethyan rift basin in the Jurassic. The Ragusa Basin represents Mesozoic developments along the southern portion of the Apulian Plate. Depositionally, paleohighs and periods of tectonic stability are typically represented by extensive carbonate platform deposits. Within these carbonate platforms incipient stages of faulting are characterized by shallow anoxic lagoonal deposits. These structurally weak ones were subsequently incorporated within the Tethyan Jurassic rift. Synrift deposits are predominantly characterized by thick sequences of Jurassic and Cretaceous pelagic carbonates.

  10. Depositional model for carbonate-evaporite cyclicity: Middle Pennsylvanian of Paradox basin

    SciTech Connect

    Kendall, A.C.

    1987-05-01

    The Paradox basin is a classic area for the study of relations between carbonates and evaporites. Previous depositional models assume carbonates and evaporites are coeval, implying that the evaporites were deep water deposits. Stratigraphic relationships are, however, complicated by previously unrecognized salt dissolution. Restoration of the missing salts indicates that evaporites entirely postdate marine carbonates in each cycle. Anhydrites and silty dolomites that succeed halites are reinterpreted as shallow hypersaline to subaerial deposits. These playa-like sediments are abruptly overlain by organic-rich shales that represent anoxic and the deepest-water deposits in the sequence. Paradox basin salts and succeeding playa deposits formed in a deep but desiccated basin. Sea level rises drowned the formerly exposed basin rims, causing sudden complete floodings of the basin and the abrupt contacts between playa deposits and deep-water shales. The shale-carbonate-evaporite sequences that form lower parts of cycles resulted from sea level falls. These ultimately exposed basin rims, isolating the basin, and allowed evaporative draw down and the deposition of basin-central evaporites. In contrast, the halite-anhydrite-silty dolomite sequences of the upper parts of cycles arose when sediment aggradation caused expansion of the evaporite depositional area onto basin flanks. There brine reflux became more significant. This reduced residence times of brines in the basin so that, progressively, salinities decreased and only less-saline sediments were able to persist in the playa environment. Cycles end (or begin) when renewed sea level rises drowned the basin-central playas.

  11. Large CH4 production fueled by autochthonous OC in an anoxic sediment

    NASA Astrophysics Data System (ADS)

    Grasset, Charlotte; Mendonça, Raquel; Villamor Saucedo, Gabriella; Sobek, Sebastian

    2017-04-01

    River damming and human-induced eutrophication both affect river and lake functioning, increase organic carbon (OC) sedimentation rates and generate anoxic conditions in bottom waters. Under these conditions, OC in sediments is decomposed into CO2 and CH4, a high potential greenhouse gas. It has been shown that the decomposition of land-derived (allochthonous) OC is inhibited at anoxic conditions, compared to OC internally produced (autochthonous). However, the overall extent and end products (CO2 or CH4) of anoxic decomposition remain poorly known for different types of OC, making it difficult to judge the effect of river damming and eutrophication on greenhouse gas emissions from inland waters. We incubated different types of allochthonous OC (terrestrial plants) and autochthonous OC (phytoplankton and aquatic vascular plants) in an anoxic sediment during 130 days. We aimed to test 1) if this addition of relatively fresh OC resulted in an increase of CH4 production and 2) if autochthonous OC would produce more CH4 than allochthonous OC. We assessed the contribution to CH4 production of the different OC sources (i.e. sediment or added OC) with stable isotope measurements. We found that the addition of relatively fresh OC greatly increased CH4 production. Autochthonous OC generally produced more CH4 than allochthonous OC, but the overall extent of CH4 production was highly variable between the different autochthonous OC types. The d13C-CH4 measurements indicated that CH4 originated exclusively from the added OC. We conclude that the production of CH4 is likely to to be high in eutrophic as well as in artificial lakes, especially when these systems have anoxic bottom waters and high internal primary productivity and thus a high supply of autochthonous OC to the sediment. The current expansion of reservoir construction in concert with almost globally prevalent anthropogenic eutrophication are therefore likely to increase CH4 production in inland waters.

  12. Open Questions on the Origin of Life at Anoxic Geothermal Fields

    PubMed Central

    Mulkidjanian, Armen Y.; Bychkov, Andrew Yu.; Dibrova, Daria V.; Galperin, Michael Y.; Koonin, Eugene V.

    2014-01-01

    We have recently reconstructed the ‘hatcheries’ of the first cells by combining geochemical analysis with phylogenomic scrutiny of the inorganic ion requirements of universal components of modern cells (Mulkidjanian et al.: Origin of first cells at terrestrial, anoxic geothermal fields. Proc Natl Acad Sci USA 2012, 109:E821–830). These ubiquitous, and by inference primordial, proteins and functional systems show affinity to and functional requirement for K+, Zn2+, Mn2+, and phosphate. Thus, protocells must have evolved in habitats with a high K+/Na+ ratio and relatively high concentrations of Zn, Mn and phosphorous compounds. Geochemical reconstruction shows that the ionic composition conducive to the origin of cells could not have existed in marine settings but is compatible with emissions of vapor-dominated zones of inland geothermal systems. Under anoxic, CO2-dominated atmosphere, the ionic composition of pools of cool, condensed vapor at anoxic geothermal fields would resemble the internal milieu of modern cells. Such pools would be lined with porous silicate minerals mixed with metal sulfides and enriched in K+ ions and phosphorous compounds. Here we address some questions that have appeared in print after the publication of our anoxic geothermal field scenario. We argue that anoxic geothermal fields, which were identified as likely cradles of life by using a top-down approach and phylogenomics analysis as a tool, could provide geochemical conditions similar to those which were suggested as most conducive for the emergence of life by the chemists who pursuit the complementary bottom-up strategy. PMID:23132762

  13. Fate of trace organic contaminants in oxic-settling-anoxic (OSA) process applied for biosolids reduction during wastewater treatment.

    PubMed

    Semblante, Galilee U; Hai, Faisal I; McDonald, James; Khan, Stuart J; Nelson, Mark; Lee, Duu-Jong; Price, William E; Nghiem, Long D

    2017-09-01

    This study investigated the fate of trace organic contaminants (TrOCs) in an oxic-settling-anoxic (OSA) process consisting of a sequencing batch reactor (SBR) with external aerobic/anoxic and anoxic reactors. OSA did not negatively affect TrOC removal of the SBR. Generally, low TrOC removal was observed under anoxic and low substrate conditions, implicating the role of co-metabolism in TrOC biodegradation. Several TrOCs that were recalcitrant in the SBR (e.g., benzotriazole) were biodegraded in the external aerobic/anoxic reactor. Some hydrophobic TrOCs (e.g., triclosan) were desorbed in the anoxic reactor possibly due to loss of sorption sites through volatile solids destruction. In OSA, the sludge was discharged from the aerobic/anoxic reactor which contained lower concentration of TrOCs (e.g., triclosan and triclocarban) than that of the control aerobic digester, suggesting that OSA can also help to reduce TrOC concentration in residual biosolids. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Preparation and Characterization of Uranium Oxides in Support of the K Basin Sludge Treatment Project

    SciTech Connect

    Sinkov, Sergey I.; Delegard, Calvin H.; Schmidt, Andrew J.

    2008-07-08

    Uraninite (UO2) and metaschoepite (UO3·2H2O) are the uranium phases most frequently observed in K Basin sludge. Uraninite arises from the oxidation of uranium metal by anoxic water and metaschoepite arises from oxidation of uraninite by atmospheric or radiolytic oxygen. Studies of the oxidation of uraninite by oxygen to form metaschoepite were performed at 21°C and 50°C. A uranium oxide oxidation state characterization method based on spectrophotometry of the solution formed by dissolving aqueous slurries in phosphoric acid was developed to follow the extent of reaction. This method may be applied to determine uranium oxide oxidation state distribution in K Basin sludge. The uraninite produced by anoxic corrosion of uranium metal has exceedingly fine particle size (6 nm diameter), forms agglomerates, and has the formula UO2.004±0.007; i.e., is practically stoichiometric UO2. The metaschoepite particles are flatter and wider when prepared at 21°C than the particles prepared at 50°C. These particles are much smaller than the metaschoepite observed in prolonged exposure of actual K Basin sludge to warm moist oxidizing conditions. The uraninite produced by anoxic uranium metal corrosion and the metaschoepite produced by reaction of uraninite aqueous slurries with oxygen may be used in engineering and process development testing. A rapid alternative method to determine uranium metal concentrations in sludge also was identified.

  15. Performance of a wetland/anoxic limestone drain treatment system at the Douglas abandoned mine land project

    SciTech Connect

    Sterner, P.L.; Cliff, J.B.; Skousen, J.G.; Sexstone, A.J.

    1996-12-31

    Acid Mine Drainage (AMD) exiting West Virginia`s Abandoned Mine Land (AML) sites often is remediated using passive treatment systems. A new passive treatment technology which employs a combination wetland/anoxic limestone drain (WALD) is currently being evaluated at one AML site near Thomas, WV. The WALD utilizes a three cell design to complete treatment. Cell 1 (dimensions 365.8m x 2.5m x 1.8m- L x W x D) employs a 0.6m base of limestone overlain by 1.2m of organic material. Cell 2 (dimensions 457.2m x 9.1m x 2.4m) employs a 1.5m limestone base overlain by 0.9m of organic material. Cell 3 (dimensions 25m x 9.1 in x 1.2m) is a sedimentation basin which allows deposition of precipitating metals. Thirteen polyvinyl chloride (PVC) cylinders with multiple ports were installed throughout the system so that water sampling at various locations and depths can be conducted. The working hypotheses to be tested is whether microbial iron reduction in organic sediments is sufficient to prevent limestone coating by iron oxyhydroxides, thus allowing continuous limestone dissolution and subsequent pH increase of the treated AMD. Influent water enters the system via surface flow at a rate of approximately 240 gpm from pipes draining an underground coal mine. Average influent AMD parameters over the study period were: pH = 3.0, total acidity = 426 mg/L, total alkalinity = 0 mg/L, total iron = 20 mg/L, total manganese = 6 mg/L and aluminum = 31 mg/L. Results based on effluent water quality indicate that AMD is being treated by the WALD.

  16. Uranium(IV) oxidation during anoxic chemical extractions of natural sediment: Importance of Fe(III)

    NASA Astrophysics Data System (ADS)

    Campbell, K. M.; Davis, J. A.; Fuller, C. C.

    2008-12-01

    In situ reduction of soluble U(VI) to insoluble U(IV) precipitates is one promising solution for the remediation of U-contaminated aquifers. U(VI) reduction can occur upon stimulation of the native microbial community by injection of an electron donor or by the presence of natural organic matter. Contamination from a former U mill tailings repository (Rifle, CO) provides a research site to study the effects of in situ and natural bioreduction. An accurate method for determining solid-phase U oxidation state in sediments with elevated amounts of Fe and organic matter is necessary to evaluate the extent of bioreduction. The oxidation state of U in anaerobic sediment is often measured by a two-step bicarbonate/carbonate chemical extraction when spectroscopic methods are infeasible. In this study, anaerobic sediment samples from Rifle were analyzed for labile U(VI) content by extraction in anoxic conditions (pH 9.4, 14mM NaHCO3, 2.8 mM Na2CO3). A subset of each sediment sample was oxidized by exposure to air for 2 weeks. The extraction was repeated in air, and the amount of U(IV) present in the anaerobic sample was calculated by difference between the anoxic and oxidized extractions. For comparison, the U oxidation state was measured in several preserved samples by collecting X-ray absorption spectra (XANES). The XANES measurement indicated that approximately 90% was present as U(IV) prior to the extraction. In contrast, the extractions suggested evidence of substantial oxidation (<5% as U(IV)) even in an anoxic extraction. This discrepancy was eliminated when the anoxic extractions were repeated at pH 12, suggesting that Fe(III) may be an important oxidant for reduced U species during an anoxic extraction at pH 9.4, since the thermodynamic driving force for this reaction decreases at high pH. The results of an investigation of biogenic uraninite (UO2) oxidation by ferrihydrite in the pH range 7-12 under bicarbonate/carbonate extraction concentrations will be presented

  17. Nutrients as the dominant control on the spread of anoxia and euxinia across the Cenomanian-Turonian oceanic anoxic event (OAE2): Model-data comparison

    NASA Astrophysics Data System (ADS)

    Monteiro, F. M.; Pancost, R. D.; Ridgwell, A.; Donnadieu, Y.

    2012-12-01

    The Cenomanian-Turonian oceanic anoxic event (OAE2) is characterized by large perturbations in the oxygen and sulfur cycles of the ocean, potentially resulting from changes in oxygen supply (via oxygen solubility and ocean circulation) and in marine productivity. We assess the relative impact of these mechanisms, comparing model experiments with a new compilation of observations for seafloor dysoxia/anoxia and photic zone euxinia. The model employed is an intermediate-complexity Earth system model which accounts for the main ocean dynamics and biogeochemistry of the Cretaceous climate. The impact of higher temperature and marine productivity is evaluated in the model as a result of higher atmospheric carbon dioxide and oceanic nutrient concentrations. The model shows that temperature is not alone able to reproduce the observed patterns of oceanic redox changes associated with OAE2. Observations are reproduced in the model mainly via enhanced marine productivity due to higher nutrient content (responsible for 85% of the change). Higher phosphate content could have been sustained by increased chemical weathering and phosphorus regeneration from anoxic sediments, which in turn induced an enhanced nitrogen nutrient content of the ocean via nitrogen fixation. The model also shows that the presence of seafloor anoxia, as suggested by black-shale deposition in the proto-North Atlantic Ocean before the event, might be the result of the silled shape and lack of deep-water formation of this basin at the Late Cretaceous. Overall our model-data comparison shows that OAE2 anoxia was quasi-global spreading from 5% of the ocean volume before the event to at least 50% during OAE2.

  18. Cryogenic formation of brine and sedimentary mirabilite in submergent coastal lake basins, Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Grasby, Stephen E.; Rod Smith, I.; Bell, Trevor; Forbes, Donald L.

    2013-06-01

    Two informally named basins (Mirabilite Basins 1 and 2) along a submergent coastline on Banks Island, Canadian Arctic Archipelago, host up to 1 m-thick accumulations of mirabilite (Na2SO4·10H2O) underlying stratified water bodies with basal anoxic brines. Unlike isostatically uplifting coastlines that trap seawater in coastal basins, these basins formed from freshwater lakes that were transgressed by seawater. The depth of the sill that separates the basins from the sea is shallow (1.15 m), such that seasonal sea ice formation down to 1.6 m isolates the basins from open water exchange through the winter. Freezing of seawater excludes salts, generating dense brines that sink to the basin bottom. Progressive freezing increases salinity of residual brines to the point of mirabilite saturation, and as a result sedimentary deposits of mirabilite accumulate on the basin floors. Brine formation also leads to density stratification and bottom water anoxia. We propose a model whereby summer melt of the ice cover forms a temporary freshwater lens, and rather than mixing with the underlying brines, it is exchanged with seawater once the ice plug that separates the basins from the open sea melts. This permits progressive brine development and density stratification within the basins.

  19. Hydrocarbon source potential in Brazilian margin basins

    SciTech Connect

    Mello, M.R.; Estrella, G.D.O.; Gaglianone, P.C.

    1984-04-01

    Twenty thousand samples from the Brazilian continental shelf basins were analyzed to characterize and evaluate the hydrocarbon source potential of the areas. The geochemical evaluation of the rock and oil samples was performed by organic carbon determinations, Rock-Eval pyrolysis, vitrinite reflectance, thermal alteration index, liquid and gas chromatographies, gas chromatography-mass spectrometry, and carbon isotope analyses. Three source rock systems have been identified: lower Neocomian shales deposited in a continental environment, upper Neocomian shales grading from continental to lagoonal environment, and Aptian shales related to evaporitic and lacustrine sequences. Upper Cretaceous and Tertiary open marine slope sediments are not considered as source rocks. Locally, these sediments present high organic carbon content but show an extremely poor hydrocarbon yield. Anoxic depositional conditions, nevertheless, can be traced locally along some levels of the Santonian to Cenomanian shales and marls. These sediments are generally immature in the Brazilian margin basins and no oil was generated from this section. Three oil families were distinguished through oil-to-oil and oil-to-source rock correlations: the lower Neocomian continental type, the upper Neocomian continental to lagoonal type, and the Aptian evaporitic to lacustrine related sequences. The geochemical studies, together with geologic and geophysical data, provided the basis to display some models for the migration pathways and habitat of oils in the Brazilian margin basins.

  20. Calcium isotope evidence for dramatic increase of continental weathering during the Toarcian oceanic anoxic event (Early Jurassic)

    NASA Astrophysics Data System (ADS)

    Brazier, Jean-Michel; Suan, Guillaume; Tacail, Théo; Simon, Laurent; Martin, Jeremy E.; Mattioli, Emanuela; Balter, Vincent

    2015-02-01

    The early Toarcian was punctuated by pulses of massive carbon injection that are thought to have triggered, through increased greenhouse conditions, elevated continental discharge and nutrient input, marine anoxia, seawater acidification and species extinctions. Nevertheless, the mode and tempo of changes in continental weathering across this interval remains highly debated, leading to considerable uncertainty about the main causes of these perturbations. In this study we present calcium isotope measurements (δ44/40Ca) of well-preserved brachiopods and bulk rock samples from the hemipelagic strata of Pliensbachian-Toarcian age of Peniche in Portugal in order to constrain changes in the calcium cycle and hence changes in continental weathering during the early Toarcian. The data reveal a similar trend as carbon isotope data from the same section and show negative excursions of about 0.5‰ at the Pliensbachian-Toarcian transition (Pl-To) and at the base of the Toarcian Oceanic Anoxic Event (T-OAE) interval. The comparison of δ44/40Ca ratios recorded in brachiopods and bulk rock corrected for variable dolomite contribution indicates that these excursions reflect changes in the global isotopic composition of seawater rather than changes in the dominant mineralogy of calcifying organisms or in hydrological budget of the considered basin. Box modeling results suggest that the Pl-To and T-OAE δ44/40Ca excursions can be explained by a transient 90% decrease of carbonate accumulation due to seawater acidification followed by a 500% increase in continental weathering rates. The sharp increases in continental weathering inferred from the δ44/40Ca ratios seem overall consistent with lower Toarcian sedimentological and biotic records that document rapid crises in carbonate production followed by episodes of increased calcium carbonate burial. Nevertheless, the maximum of carbonate burial recorded by most NW European basinal successions occurs several hundreds of kyrs after

  1. Geochemical evidence for anoxic deep water in the Arabian Sea during the last glaciation

    SciTech Connect

    Sarkar, A.; Bhattacharya, S.K.; Sarin, M.M. )

    1993-03-01

    Various paleoceanographic studies have indicated that the deep ocean was probably depleted in dissolved oxygen during the last glacial period ([approximately]18 kyr B.P.; [delta][sup 18]O, stage 2) compared to present time. However, direct evidence of low oxygen content in the deep waters has been lacking. Here, the authors report geochemical evidence of near anoxic conditions in the deep Arabian Sea during the entire last glacial cycle ([delta][sup 18]O; stages 2, 3, and 4). Anoxia is inferred from the concomitant enrichment of organic carbon and authigenic uranium in the glacial sections of a core from the deep eastern Arabian Sea. The anoxic conditions during the last glacial period, probably caused by a change in deep water circulation, evidently enhanced preservation of organic matter and simultaneous removal of uranium from seawater. 57 refs., 3 figs., 2 tabs.

  2. Multiple S-isotopic evidence for episodic shoaling of anoxic water during Late Permian mass extinction.

    PubMed

    Shen, Yanan; Farquhar, James; Zhang, Hua; Masterson, Andrew; Zhang, Tonggang; Wing, Boswell A

    2011-02-22

    Global fossil data show that profound biodiversity loss preceded the final catastrophe that killed nearly 90% marine species on a global scale at the end of the Permian. Many hypotheses have been proposed to explain this extinction and yet still remain greatly debated. Here, we report analyses of all four sulphur isotopes ((32)S, (33)S, (34)S and (36)S) for pyrites in sedimentary rocks from the Meishan section in South China. We observe a sulphur isotope signal (negative δ(34)S with negative Δ(33)S) that may have resulted from limitation of sulphate supply, which may be linked to a near shutdown of bioturbation during shoaling of anoxic water. These results indicate that episodic shoaling of anoxic water may have contributed to the profound biodiversity crisis before the final catastrophe. Our data suggest a prolonged deterioration of oceanic environments during the Late Permian mass extinction.

  3. Algae after dark: mechanisms to cope with anoxic/hypoxic conditions.

    PubMed

    Yang, Wenqiang; Catalanotti, Claudia; Wittkopp, Tyler M; Posewitz, Matthew C; Grossman, Arthur R

    2015-05-01

    Chlamydomonas reinhardtii is a unicellular, soil-dwelling (and aquatic) green alga that has significant metabolic flexibility for balancing redox equivalents and generating ATP when it experiences hypoxic/anoxic conditions. The diversity of pathways available to ferment sugars is often revealed in mutants in which the activities of specific branches of fermentative metabolism have been eliminated; compensatory pathways that have little activity in parental strains under standard laboratory fermentative conditions are often activated. The ways in which these pathways are regulated and integrated have not been extensively explored. In this review, we primarily discuss the intricacies of dark anoxic metabolism in Chlamydomonas, but also discuss aspects of dark oxic metabolism, the utilization of acetate, and the relatively uncharacterized but critical interactions that link chloroplastic and mitochondrial metabolic networks. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

  4. Is anoxic depolarisation associated with an ADC threshold? A Markov chain Monte Carlo analysis.

    PubMed

    King, Martin D; Crowder, Martin J; Hand, David J; Harris, Neil G; Williams, Stephen R; Obrenovitch, Tihomir P; Gadian, David G

    2005-12-01

    A Bayesian nonlinear hierarchical random coefficients model was used in a reanalysis of a previously published longitudinal study of the extracellular direct current (DC)-potential and apparent diffusion coefficient (ADC) responses to focal ischaemia. The main purpose was to examine the data for evidence of an ADC threshold for anoxic depolarisation. A Markov chain Monte Carlo simulation approach was adopted. The Metropolis algorithm was used to generate three parallel Markov chains and thus obtain a sampled posterior probability distribution for each of the DC-potential and ADC model parameters, together with a number of derived parameters. The latter were used in a subsequent threshold analysis. The analysis provided no evidence indicating a consistent and reproducible ADC threshold for anoxic depolarisation.

  5. Dynamic interplay between microbial denitrification and antibiotic resistance under enhanced anoxic denitrification condition in soil.

    PubMed

    Sun, Mingming; Ye, Mao; Liu, Kuan; Schwab, Arthur P; Liu, Manqiang; Jiao, Jiaguo; Feng, Yanfang; Wan, Jinzhong; Tian, Da; Wu, Jun; Li, Huixin; Hu, Feng; Jiang, Xin

    2017-03-01

    Mixed contamination of nitrate and antibiotics/antibiotic-resistant genes (ARGs) is an emerging environmental risk to farmland soil. This is the first study to explore the role of excessive anthropogenic nitrate input in the anoxic dissipation of soil antibiotic/ARGs. During the initial 10 days of incubation, the presence of soil antibiotics significantly inhibited NO3(-) dissipation, N2O production rate, and denitrifying genes (DNGs) abundance in soil (p < 0.05). Between days 10 and 30, by contrast, enhanced denitrification clearly prompted the decline in antibiotic contents and ARG abundance. Significantly negative correlations were detected between DNGs and ARGs, suggesting that the higher the DNG activity, the more dramatic is the denitrification and the greater are the antibiotic dissipation and ARG abundance. This study provides crucial knowledge for understanding the mutual interaction between soil DNGs and ARGs in the enhanced anoxic denitrification condition.

  6. Internal recycle to improve denitrification in a step feed anoxic/aerobic activated sludge system.

    PubMed

    Boyle, C A; McKenzie, C J; Morgan, S

    2009-01-01

    During periods of low load (weekends and holidays) the Mangere wastewater treatment plant effluent has breached the summer consent conditions for total nitrogen. The purpose of this research was to determine if an internal recycle would improve nitrogen removal in the anoxic/aerobic activated sludge reactors sufficient to meet the summer resource consent standard. The recycle returned nitrate rich mixed liquor from the downstream aerobic zone back to the initial anoxic zone, thus potentially improving denitrification. A full scale trial showed that installation of the internal recycle on each RC would have satisfied the resource consent for total nitrogen in most cases over the three summer resource consent periods since the upgrade. However, further modifications of the internal recycle would be required to ensure that consent conditions were satisfied at all times and to improve the consistency of the results.

  7. The Anoxic Corrosion of Copper in Pure Water and Chloride Rich Brines

    NASA Astrophysics Data System (ADS)

    Ilic, Emilija

    The Nuclear Waste Management Organization (NWMO) is developing an approach for the permanent geological disposal of nuclear waste. The waste will be encased in copper coated used fuel containers (UFCs) and placed in a deep geological repository (DGR). To support the NWMO in their investigations on the long-term corrosion of copper a lab scale simulation of the DGR environment was created. Copper wires were placed in glass electrochemical cells and exposed to one of two environments; pure anoxic water or chloride-rich anoxic brine. The systems were allowed to freely corrode and accumulate hydrogen within their headspaces over extended durations at 30 to 75 °C. The hydrogen was periodically purged and subsequently analyzed using a highly sensitive amperometric sensor; these measurements were utilized to calculate the corresponding copper corrosion rates. Corrosion with hydrogen evolution was demonstrated in both pure water and brines at slow rates below 1 and 10 nm/year, respectively.

  8. Multiple S-isotopic evidence for episodic shoaling of anoxic water during Late Permian mass extinction

    PubMed Central

    Shen, Yanan; Farquhar, James; Zhang, Hua; Masterson, Andrew; Zhang, Tonggang; Wing, Boswell A.

    2011-01-01

    Global fossil data show that profound biodiversity loss preceded the final catastrophe that killed nearly 90% marine species on a global scale at the end of the Permian. Many hypotheses have been proposed to explain this extinction and yet still remain greatly debated. Here, we report analyses of all four sulphur isotopes (32S, 33S, 34S and 36S) for pyrites in sedimentary rocks from the Meishan section in South China. We observe a sulphur isotope signal (negative δ34S with negative Δ33S) that may have resulted from limitation of sulphate supply, which may be linked to a near shutdown of bioturbation during shoaling of anoxic water. These results indicate that episodic shoaling of anoxic water may have contributed to the profound biodiversity crisis before the final catastrophe. Our data suggest a prolonged deterioration of oceanic environments during the Late Permian mass extinction. PMID:21343928

  9. Stimulated anoxic biodegradation of aromatic hydrocarbons using Fe(III) ligands

    USGS Publications Warehouse

    Lovley, D.R.; Woodward, J.C.; Chapelle, F.H.

    1994-01-01

    Contamination of ground waters with water-soluble aromatic hydrocarbons, common components of petroleum pollution, often produces anoxic conditions under which microbial degradation of the aromatics is slow. Oxygen is often added to contaminated ground water to stimulate biodegradation, but this can be technically difficult and expensive. Insoluble Fe(III) oxides, which are generally abundant in shallow aquifers, are alternative potential oxidants, but are difficult for microorganisms to access. Here we report that adding organic ligands that bind to Fe(III) dramatically increases its bioavailability, and that in the presence of these ligands, rates of degradation of aromatic hydrocarbons in anoxic aquifer sediments are comparable to those in oxic sediments. We find that even benzene, which is notoriously refractory in the absence of oxygen, can be rapidly degraded. Our results suggest that increasing the bioavailability of Fe(III) by adding suitable ligands provides a potential alternative to oxygen addition for the bioremediation of petroleum-contaminated aquifers.Contamination of ground waters with water-soluble aromatic hydrocarbons, common components of petroleum pollution, often produces anoxic conditions under which microbial degradation of the aromatics is slow. Oxygen is often added to contaminated ground water to stimulate biodegradation, but this can be technically difficult and expensive. Insoluble Fe(III) oxides, which are generally abundant in shallow aquifers, are alternative potential oxidants, but are difficult for microorganisms to access. Here we report that adding organic ligands that bind to Fe(III) dramatically increases its bioavailability, and that in the presence of these ligands, rates of degradation of aromatic hydrocarbons in anoxic aquifer sediments are comparable to those in oxic sediments. We find that even benzene, which is notoriously refractory in the absence of oxygen, can be rapidly degraded. Our results suggest that increasing

  10. Poor outcome prediction by burst suppression ratio in adults with post-anoxic coma without hypothermia.

    PubMed

    Yang, Qinglin; Su, Yingying; Hussain, Mohammed; Chen, Weibi; Ye, Hong; Gao, Daiquan; Tian, Fei

    2014-05-01

    Burst suppression ratio (BSR) is a quantitative electroencephalography (qEEG) parameter. The purpose of our study was to compare the accuracy of BSR when compared to other EEG parameters in predicting poor outcomes in adults who sustained post-anoxic coma while not being subjected to therapeutic hypothermia. EEG was registered and recorded at least once within 7 days of post-anoxic coma onset. Electrodes were placed according to the international 10-20 system, using a 16-channel layout. Each EEG expert scored raw EEG using a grading scale adapted from Young and scored amplitude-integrated electroencephalography tracings, in addition to obtaining qEEG parameters defined as BSR with a defined threshold. Glasgow outcome scales of 1 and 2 at 3 months, determined by two blinded neurologists, were defined as poor outcome. Sixty patients with Glasgow coma scale score of 8 or less after anoxic accident were included. The sensitivity (97.1%), specificity (73.3%), positive predictive value (82.5%), and negative prediction value (95.0%) of BSR in predicting poor outcome were higher than other EEG variables. BSR1 and BSR2 were reliable in predicting death (area under the curve > 0.8, P < 0.05), with the respective cutoff points being 39.8% and 61.6%. BSR1 was reliable in predicting poor outcome (area under the curve  =  0.820, P < 0.05) with a cutoff point of 23.9%. BSR1 was also an independent predictor of increased risk of death (odds ratio  =  1.042, 95% confidence intervals: 1.012-1.073, P  =  0.006). BSR may be a better predictor in prognosticating poor outcomes in patients with post-anoxic coma who do not undergo therapeutic hypothermia when compared to other qEEG parameters.

  11. Open questions on the origin of life at anoxic geothermal fields.

    PubMed

    Mulkidjanian, Armen Y; Bychkov, Andrew Yu; Dibrova, Daria V; Galperin, Michael Y; Koonin, Eugene V

    2012-10-01

    We have recently reconstructed the 'hatcheries' of the first cells by combining geochemical analysis with phylogenomic scrutiny of the inorganic ion requirements of universal components of modern cells (Mulkidjanian et al. Proc Natl Acad Sci U S A 109:E821-830, 2012). These ubiquitous, and by inference primordial, proteins and functional systems show affinity to and functional requirement for K⁺, Zn²⁺, Mn²⁺, and phosphate. Thus, protocells must have evolved in habitats with a high K⁺/Na⁺ ratio and relatively high concentrations of Zn, Mn and phosphorous compounds. Geochemical reconstruction shows that the ionic composition conducive to the origin of cells could not have existed in marine settings but is compatible with emissions of vapor-dominated zones of inland geothermal systems. Under an anoxic, CO₂-dominated atmosphere, the ionic composition of pools of cool, condensed vapor at anoxic geothermal fields would resemble the internal milieu of modern cells. Such pools would be lined with porous silicate minerals mixed with metal sulfides and enriched in K⁺ ions and phosphorous compounds. Here we address some questions that have appeared in print after the publication of our anoxic geothermal field scenario. We argue that anoxic geothermal fields, which were identified as likely cradles of life by using a top-down approach and phylogenomics analysis, could provide geochemical conditions similar to those which were suggested as most conducive for the emergence of life by the chemists who pursuit the complementary bottom-up strategy.

  12. Long-chain acylhomoserine lactones increase the anoxic ammonium oxidation rate in an OLAND biofilm.

    PubMed

    De Clippeleir, Haydée; Defoirdt, Tom; Vanhaecke, Lynn; Vlaeminck, Siegfried E; Carballa, Marta; Verstraete, Willy; Boon, Nico

    2011-05-01

    The oxygen-limited autotrophic nitrification/denitrification (OLAND) process comprises one-stage partial nitritation and anammox, catalyzed by aerobic and anoxic ammonium-oxidizing bacteria (AerAOB and AnAOB), respectively. The goal of this study was to investigate whether quorum sensing influences anoxic ammonium oxidation in an OLAND biofilm, with AnAOB colonizing 13% of the biofilm, as determined with fluorescent in situ hybridization (FISH). At high biomass concentrations, the specific anoxic ammonium oxidation rate of the OLAND biofilm significantly increased with a factor of 1.5 ± 0.2 compared to low biomass concentrations. Supernatant obtained from the biofilm showed no ammonium-oxidizing activity on itself, but its addition to low OLAND biomass concentrations resulted in a significant activity increase of the biomass. In the biofilm supernatant, the presence of long-chain acylhomoserine lactones (AHLs) was shown using the reporter strain Chromobacterium violaceum CV026, and one specific AHL, N-dodecanoyl homoserine lactone (C(12)-HSL), was identified via LC-MS/MS. Furthermore, C(12)-HSL was detected in an AnAOB-enriched community, but not in an AerAOB-enriched community. Addition of C(12)-HSL to low OLAND biomass concentrations resulted in a significantly higher ammonium oxidation rate (p < 0.05). To our knowledge, this is the first report demonstrating that AHLs enhance the anoxic ammonium oxidation process. Future work should confirm which species are responsible for the in situ production of C(12)-HSL in AnAOB-based applications.

  13. Comment on "Calcareous nannoplankton response to surface-water acidification around Oceanic Anoxic Event 1a".

    PubMed

    Gibbs, Samantha J; Robinson, Stuart A; Bown, Paul R; Jones, Tom Dunkley; Henderiks, Jorijntje

    2011-04-08

    Erba et al. (Reports, 23 July 2010, p. 428) attributed calcareous nannofossil morphology and assemblage changes across Cretaceous Oceanic Anoxic Event 1a to the effects of surface ocean acidification. We argue that the quality of carbonate preservation in these sequences, the unsupported assumptions of the biotic response to acidity, and the absence of independent proxy estimates for ocean pH or atmospheric pCO(2) render this conclusion questionable.

  14. Tritirachium candoliense sp. nov., a novel basidiomycetous fungus isolated from the anoxic zone of the Arabian Sea.

    PubMed

    Manohar, Cathrine Sumathi; Boekhout, Teun; Müller, Wally H; Stoeck, Thorsten

    2014-02-01

    A fungal culture (FCAS11) was isolated from coastal sediments of the Arabian Sea during the anoxic season. Multigene phylogenetic analyses confidentially place the organism as a novel species within the recently defined class Tritirachiomycetes, subphylum Pucciniomycotina, phylum Basidiomycota. We named the new species Tritirachium candoliense and provide the first description of a member of this class from a marine environment. DNA sequences and morphological characters distinguish T. candoliense from previously described Tritirachium species. Its growth characteristics, morphology, and ultrastructural features showed that under anoxic conditions the species grows slowly and produces mainly hyphae with only few blastoconidia. Electron microscopy revealed differences when the culture was exposed to anoxic stress. Notable ultrastructural changes occur for example in mitochondrial cristae, irregularly shaped fat globules and the presence of intracellular membrane invaginations. We assume that the growth characteristics and substrate utilization patterns are an adaptation to its source location, the seasonally anoxic environment of the Arabian Sea.

  15. The Role of Cell Volume in the Dynamics of Seizure, Spreading Depression, and Anoxic Depolarization

    PubMed Central

    Ullah, Ghanim; Wei, Yina; Dahlem, Markus A; Wechselberger, Martin; Schiff, Steven J

    2015-01-01

    Cell volume changes are ubiquitous in normal and pathological activity of the brain. Nevertheless, we know little of how cell volume affects neuronal dynamics. We here performed the first detailed study of the effects of cell volume on neuronal dynamics. By incorporating cell swelling together with dynamic ion concentrations and oxygen supply into Hodgkin-Huxley type spiking dynamics, we demonstrate the spontaneous transition between epileptic seizure and spreading depression states as the cell swells and contracts in response to changes in osmotic pressure. Our use of volume as an order parameter further revealed a dynamical definition for the experimentally described physiological ceiling that separates seizure from spreading depression, as well as predicted a second ceiling that demarcates spreading depression from anoxic depolarization. Our model highlights the neuroprotective role of glial K buffering against seizures and spreading depression, and provides novel insights into anoxic depolarization and the relevant cell swelling during ischemia. We argue that the dynamics of seizures, spreading depression, and anoxic depolarization lie along a continuum of the repertoire of the neuron membrane that can be understood only when the dynamic ion concentrations, oxygen homeostasis,and cell swelling in response to osmotic pressure are taken into consideration. Our results demonstrate the feasibility of a unified framework for a wide range of neuronal behaviors that may be of substantial importance in the understanding of and potentially developing universal intervention strategies for these pathological states. PMID:26273829

  16. Contrasting strategies for anoxic brain survival--glycolysis up or down.

    PubMed

    Lutz, P L; Nilsson, G E

    1997-01-01

    Anoxia-tolerant turtles and carp (Carassius) exhibit contrasting strategies for anoxic brain survival. In the turtle brain, the energy consumption is deeply depressed to the extent of producing a comatose-like state. Brain metabolic depression is brought about by activating channel arrest to reduce ion flux and through the release of inhibitory gamma-aminobutyric acid (GABA) and the upregulation of GABAA receptors. Key glycolytic enzymes are down-regulated during prolonged anoxia. The result is a suppression of neurotransmission and a substantial depression in brain electrical activity. By contrast, Carassius remain active during anoxia, though at a reduced level. As in the turtle, there is an adenosine-mediated increase in brain blood flow but, in contrast to the turtle, this increase is sustained throughout the anoxic period. Key glycolytic enzymes are up-regulated and anaerobic glycolysis is enhanced. There is no evidence of channel arrest in Carassius brain. The probable result is that electrical activity in the brain is not suppressed but instead maintained at a level sufficient to regulate and control the locomotory and sensory activities of the anoxic carp. The key adaptations permitting the continued high level of glycolysis in Carassius are the production and excretion of ethanol as the glycolytic end-product, which avoids self-pollution by lactate produced during glycolysis that occurs in other vertebrates.

  17. Biological nutrient removal in a sequencing batch reactor operated as oxic/anoxic/extended-idle regime.

    PubMed

    Li, Xiao-ming; Chen, Hong-bo; Yang, Qi; Wang, Dong-bo; Luo, Kun; Zeng, Guang-ming

    2014-06-01

    Previous researches have demonstrated that biological phosphorus removal from wastewater could be induced by oxic/extended-idle (O/EI) regime. In this study, an anoxic period was introduced after the aeration to realize biological nutrient removal. High nitrite accumulation ratio and polyhydroxyalkanoates biosynthesis were obtained in the aeration and biological nutrient removal could be well achieved in oxic/anoxic/extended-idle (O/A/EI) regime for the wastewater used. In addition, nitrogen and phosphorus removal performance in O/A/EI regime was compared with that in conventional anaerobic/anoxic/aerobic (A(2)/O) and O/EI processes. The results showed that O/A/EI regime exhibited higher nitrogen and phosphorus removal than A(2)/O and O/EI processes. More ammonium oxidizing bacteria and polyphosphate accumulating organisms and less glycogen accumulating organisms containing in the biomass might be the principal reason for the better nitrogen and phosphorus removal in O/A/EI regime. Furthermore, biological nutrient removal with O/A/EI regime was demonstrated with municipal wastewater. The average TN, SOP and COD removal efficiencies were 93%, 95% and 87%, respectively. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Using Biogenic Sulfur Gases as Remotely Detectable Biosignatures on Anoxic Planets

    PubMed Central

    Meadows, Victoria S.; Claire, Mark W.; Kasting, James F.

    2011-01-01

    Abstract We used one-dimensional photochemical and radiative transfer models to study the potential of organic sulfur compounds (CS2, OCS, CH3SH, CH3SCH3, and CH3S2CH3) to act as remotely detectable biosignatures in anoxic exoplanetary atmospheres. Concentrations of organic sulfur gases were predicted for various biogenic sulfur fluxes into anoxic atmospheres and were found to increase with decreasing UV fluxes. Dimethyl sulfide (CH3SCH3, or DMS) and dimethyl disulfide (CH3S2CH3, or DMDS) concentrations could increase to remotely detectable levels, but only in cases of extremely low UV fluxes, which may occur in the habitable zone of an inactive M dwarf. The most detectable feature of organic sulfur gases is an indirect one that results from an increase in ethane (C2H6) over that which would be predicted based on the planet's methane (CH4) concentration. Thus, a characterization mission could detect these organic sulfur gases—and therefore the life that produces them—if it could sufficiently quantify the ethane and methane in the exoplanet's atmosphere. Key Words: Exoplanets—Biosignatures—Anoxic atmospheres—Planetary atmospheres—Remote life detection—Photochemistry. Astrobiology 11, 419–441. PMID:21663401

  19. Intracellular pH in rice and wheat root tips under hypoxic and anoxic conditions

    PubMed Central

    Chirkova, Tamara V; Fagerstedt, Kurt V

    2008-01-01

    The influence of anoxia and hypoxia on dynamic of intracellurar pH and ATP content in rice and wheat root tips was investigated with 31P-NMR spectroscopy. Both cereals responded to hypoxia similarly, by rapid cytoplasmic acidification (from pH 7.6–7.7 to 7.1), which was followed by slow partial recovery (0.3 units). Anoxia led to a dramatic pHcyt drop in tissues of both species (from pH 7.6–7.7 to less than 7.0) and partial recovery took place in rice only. In wheat, the acidification continued to pH 6.8 after 6 h of exposure. Anoxic wheat root tips were deficient in ADH induction, whereas increased activity of alcoholic fermentation enzymes took place in anoxic rice root tips, as well as in both species after hypoxic treatment. In both plants, NTP content followed the dynamics of pHcyt. There was a strong correlation between NTP content and cytoplasmic H+ activity ([H+]cyt = 10−pHcyt) for both hypoxic and anoxic conditions. In this addendum we want to focus the reader's attention on the importance of adequate experimental design when hypoxia is under investigation and on some further perspectives of intracellular pH regulation in plants under anaerobic conditions. PMID:19704641

  20. Large iron isotope fractionation at the oxic-anoxic boundary in Lake Nyos

    NASA Astrophysics Data System (ADS)

    Teutsch, Nadya; Schmid, Martin; Müller, Beat; Halliday, Alex N.; Bürgmann, Helmut; Wehrli, Bernhard

    2009-07-01

    The degassing of volcanic Lake Nyos (Cameroon) provides the opportunity to study the strong isotopic variation of dissolved Fe(II) in a well constrained redox cycle and to identify the governing processes by reaction-transport modeling. Two depth profiles sampled in the lake in March 2004 and 2005 reveal an increase in iron concentrations and δ57Fe from around 1 mg L - 1 and - 1.88‰ at 55 m depth up to 344 mg L - 1 and + 0.83‰ at the bottom of the lake, respectively. A steep increase in δ57Fe was observed across the oxic-anoxic boundary. As many biological and geochemical processes are known to fractionate Fe isotopes, we used a calibrated reaction-transport model to disentangle the processes governing the Fe cycle. The model combines the isotopic signatures of dissolved Fe(II) and settling Fe(III) particles with the concentration profiles and settling fluxes of the Fe particles in the lake. We show that the strong shift in δ57Fe is caused by isotopic fractionation via dissimilatory Fe reduction across the oxic-anoxic boundary of Lake Nyos. The shift towards more positive values below the oxic-anoxic interface could be attributed to vertical mixing of a heavier component from the bottom of the lake.

  1. Anoxic Conditions Promote Species-Specific Mutualism between Gut Microbes In Silico

    PubMed Central

    Heinken, Almut

    2015-01-01

    The human gut is inhabited by thousands of microbial species, most of which are still uncharacterized. Gut microbes have adapted to each other's presence as well as to the host and engage in complex cross feeding. Constraint-based modeling has been successfully applied to predicting microbe-microbe interactions, such as commensalism, mutualism, and competition. Here, we apply a constraint-based approach to model pairwise interactions between 11 representative gut microbes. Microbe-microbe interactions were computationally modeled in conjunction with human small intestinal enterocytes, and the microbe pairs were subjected to three diets with various levels of carbohydrate, fat, and protein in normoxic or anoxic environments. Each microbe engaged in species-specific commensal, parasitic, mutualistic, or competitive interactions. For instance, Streptococcus thermophilus efficiently outcompeted microbes with which it was paired, in agreement with the domination of streptococci in the small intestinal microbiota. Under anoxic conditions, the probiotic organism Lactobacillus plantarum displayed mutualistic behavior toward six other species, which, surprisingly, were almost entirely abolished under normoxic conditions. This finding suggests that the anoxic conditions in the large intestine drive mutualistic cross feeding, leading to the evolvement of an ecosystem more complex than that of the small intestinal microbiota. Moreover, we predict that the presence of the small intestinal enterocyte induces competition over host-derived nutrients. The presented framework can readily be expanded to a larger gut microbial community. This modeling approach will be of great value for subsequent studies aiming to predict conditions favoring desirable microbes or suppressing pathogens. PMID:25841013

  2. [Analysis of hydrolytic enzyme activities on sludge aerobic/anoxic digestion after ultrasonic pretreatment].

    PubMed

    Ye, Yun-di; Sun, Shui-yu; Zheng, Li; Liu, Bao-jian; Xu, Yan-bin; Zhan, Xing-xing; Liu, Jing-yong

    2012-08-01

    In order to evaluate the function of sludge aerobic/anoxic digestibility by ultrasonic pretreatment. The SS, VSS and hydrolytic enzyme activities (amylase, glucosidase, protease, phosphatase) were measured before and after ultrasonic pretreatment (28 kHz, 0.15 kW x L(-1), 10 min). The results showed that the performances of aerobic/anoxic were greatly improved after ultrasonic pretreatment, the removal efficiency of VSS went to 44.3%, 7.8% better than of traditional aerobic/anoxic digestion. The variational trend of sludge hydrolytic enzyme activities increased firstly and then fell off during 13d digestion, the maximum of amylase activity and glucosidase activity in ultrasonic sludge, appeared in the 5 d, amylase activity was 0.104 micromol x g(-1) and glucosidase activity was 0.637 (micromol x g(-1). The maximum of intracellular protease activity and extracellular proteases activity in ultrasonic sludge, appeared in the 7 d, intracellular protease activity was 23.68 micromol x g(-1), higher than extracellular proteases activity, and it was playing a leading role in sludge digestion. The acid phosphatase activity of ultrasonic sludge was higher than the control sludge, and the alkaline phosphatase was sensitive to environment. So the alkaline phosphatase activity reduced when the internal properties of sludge was changed.

  3. The removal of cyanobacteria and their metabolites through anoxic biodegradation in drinking water sludge.

    PubMed

    Ma, Guangxiang; Pei, Haiyan; Hu, Wenrong; Xu, Xiangchao; Ma, Chunxia; Li, Xiuqing

    2014-08-01

    The effects of environmental factors on cyanobacteria damage and microcystin-LR degradation in drinking water sludge were investigated under anoxic conditions. The rates of microcystin-LR release and degradation increased rapidly with the increasing temperature from 15°C to 40°C and the highest degradation rate of 99% was observed at 35°C within 10days. Compared to acidic conditions, microcystin-LR degraded more rapidly in weak alkali environments. In addition, the microbial community structures under different anoxic conditions were studied. The sequencing results showed that four phyla obtained from the DGGE profiles were as follows: Proteobacteria, Acidobacteria, Firmicutes and Cyanobacteria. Proteobacteria containing nine genera were the most common species. Pseudomonas, Methylosinus and Sphingomona all showed stronger activities and had significant increase as microcystin-LR degraded, so they should be responsible for the microcystin-LR degradation. This is the first report of Pseudomonas, Methylosinus and Sphingomonas as the microcystins-degrading microorganisms in anoxic drinking water sludge.

  4. Mercury reduction and complexation by natural organic matter in anoxic environments

    PubMed Central

    Gu, Baohua; Bian, Yongrong; Miller, Carrie L.; Dong, Wenming; Jiang, Xin; Liang, Liyuan

    2011-01-01

    Mercuric Hg(II) species form complexes with natural dissolved organic matter (DOM) such as humic acid (HA), and this binding is known to affect the chemical and biological transformation and cycling of mercury in aquatic environments. Dissolved elemental mercury, Hg(0), is also widely observed in sediments and water. However, reactions between Hg(0) and DOM have rarely been studied in anoxic environments. Here, under anoxic dark conditions we show strong interactions between reduced HA and Hg(0) through thiolate ligand-induced oxidative complexation with an estimated binding capacity of ~3.5 μmol Hg/g HA and a partitioning coefficient >106 mL/g. We further demonstrate that Hg(II) can be effectively reduced to Hg(0) in the presence of as little as 0.2 mg/L reduced HA, whereas production of Hg(0) is inhibited by complexation as HA concentration increases. This dual role played by DOM in the reduction and complexation of mercury is likely widespread in anoxic sediments and water and can be expected to significantly influence the mercury species transformations and biological uptake that leads to the formation of toxic methylmercury. PMID:21220311

  5. PHA storage from several substrates by different morphological types in an anoxic/aerobic SBR.

    PubMed

    Dionisi, D; Levantesi, C; Renzi, V; Tandoi, V; Majone, M

    2002-01-01

    An activated sludge was cultivated on a mixture of several soluble substrates (acetate, ethanol, glucose, glutamic acid, peptone, Tween 80, starch, yeast extract) in an anoxic/aerobic SBR. Highly dynamic conditions in the SBR (feast famine regime) caused fast removal of most COD in the anoxic phase (in particular acetate, ethanol, glutamic acid and glucose were totally removed) and relevant contribution of storage. In spite of that, filament abundance was always high, as is typical of bulking sludges. Filaments which developed in the reactor were characterized on a morphological basis and on the basis of their ability to grow and to store polyhydroxyalkanoates (PHAs). Three main filaments prevailed in the biocenosis, whose relative abundance was varyng with time: Nostocoida limicola II, (two different morphological types), Haliscomenobacter hydrossis and an unidentified one. It was found that maximum growth rate was higher for flocformers than for filaments on each of the tested substrates. Epifluorescence showed that storage ability was more widespread among flocformers than in the filaments. Only one type of Nostocoida limicola II was able to store PHAs. The obtained data show that aerobic growth on the little residual fraction of COD from the anoxic phase was enough to support high abundance of filamentous microorganisms.

  6. Enhanced Biotransformation of Triclocarban by Ochrobactrum sp. TCC-1 Under Anoxic Nitrate Respiration Conditions.

    PubMed

    Yun, Hui; Liang, Bin; Kong, Deyong; Li, Zhiling; Qi, Guoshu; Wang, Aijie

    2017-04-01

    Antimicrobial triclocarban (3,4,4'-trichlorocarbanilide, TCC) is frequently detected in soils and sediments for the widely reclaim of sewage sludge or biosolid in recent decades. This resulted from a weak removal of TCC during wastewater treatment, and most of it adsorbed onto sewage sludge. As the toxicity and persistence of TCC in the environment, the elimination of TCC from the source of output is of great importance, particularly in anoxic process. In this study, the biotransformation of TCC by a newly isolated TCC-degrading strain Ochrobactrum sp. TCC-1 under anoxic conditions was investigated. By testing different carbon nitrogen ratios (C/N), it showed that nitrate could support the growth of strain TCC-1 and enhance the hydrolysis of TCC to more biodegradable chloroanilines, especially with a higher C/N of 10 and under anaerobic conditions. In wastewater sewage sludge, strain TCC-1 colonized and maintained the TCC-hydrolyzing activity under the nitrate respiration mode. These results would lay a basic foundation for the potential bioremediation of TCC-contaminated anoxic sites with TCC-degrading strain.

  7. Modeling of an anoxic/methanogenic biofilm: effect of pH calculation within the biofilm.

    PubMed

    César, Huiliñir; Silvio, Montalvo

    2013-11-01

    The models of anoxic/methanogenic processes in biofilm reactors published until now have supposed that pH does not change between the bulk liquid and biofilm. These assumptions are not necessarily valid for processes in reactors with biofilms. The present work studied an anoxic/methanogenic biofilm reactor incorporating the pH variation in both bulk and biofilm. Two dynamic models, one including the calculation of pH throughout the biofilm, were solved numerically and compared with each other. The results showed that the inclusion of a pH algorithm calculation produces different profiles and efficiencies on an anoxic/methanogenic biofilm system. Values of C/N ratio higher than 20 mg TOC/mg NO3-N and values of HRT lower than 4.5 h produce differences of up to 46 % with a traditional model that does not include pH calculation inside the biofilm. Thus, the assumption of a constant pH within the biofilm when using the traditional model does not accurately describe the performance of the system under these conditions, and pH calculation inside the biofilm should be included.

  8. Bacterial adaptation of respiration from oxic to microoxic and anoxic conditions: redox control.

    PubMed

    Bueno, Emilio; Mesa, Socorro; Bedmar, Eulogio J; Richardson, David J; Delgado, Maria J

    2012-04-15

    Under a shortage of oxygen, bacterial growth can be faced mainly by two ATP-generating mechanisms: (i) by synthesis of specific high-affinity terminal oxidases that allow bacteria to use traces of oxygen or (ii) by utilizing other substrates as final electron acceptors such as nitrate, which can be reduced to dinitrogen gas through denitrification or to ammonium. This bacterial respiratory shift from oxic to microoxic and anoxic conditions requires a regulatory strategy which ensures that cells can sense and respond to changes in oxygen tension and to the availability of other electron acceptors. Bacteria can sense oxygen by direct interaction of this molecule with a membrane protein receptor (e.g., FixL) or by interaction with a cytoplasmic transcriptional factor (e.g., Fnr). A third type of oxygen perception is based on sensing changes in redox state of molecules within the cell. Redox-responsive regulatory systems (e.g., ArcBA, RegBA/PrrBA, RoxSR, RegSR, ActSR, ResDE, and Rex) integrate the response to multiple signals (e.g., ubiquinone, menaquinone, redox active cysteine, electron transport to terminal oxidases, and NAD/NADH) and activate or repress target genes to coordinate the adaptation of bacterial respiration from oxic to anoxic conditions. Here, we provide a compilation of the current knowledge about proteins and regulatory networks involved in the redox control of the respiratory adaptation of different bacterial species to microxic and anoxic environments.

  9. Small sewage treatment system with an anaerobic-anoxic-aerobic combined biofilter.

    PubMed

    Park, S M; Jun, H B; Hong, S P; Kwon, J C

    2003-01-01

    The objective of this study was to investigate a small sewage treatment system that could improve nitrogen and BOD5 removal efficiency as well as generate less solid using an anaerobic-anoxic-aerobic biofiltration system. Wastewater temperature was in the range of 14-25 degrees C, and hydraulic residual times were 12 h for each reactor. The upflow anaerobic digester equipped with anoxic filter was fed with both raw sewage and recycled effluent from the aerobic filter to induce denitrification and solid reduction simultaneously. In the subsequent aerobic filter, residual organic carbon and ammonia might be oxidized and finally nitrate formed. In the anaerobic reactor, about 71% of influent TCOD was removed by sedimentation of the un-filterable COD at the recycle ratio of 300%. Another 20% of influent TCOD was removed in the anoxic filter by denitrification of the recycled nitrate. After 100 days operation, solid reduction and nitrification efficiency were about 30% and 95%, respectively. Overall removal efficiencies of COD and total nitrogen (T-N) were above 94% and 70% at the recycle ratio of 300%, respectively. Total wasted solid from the system after 100 days operation was about 316 g, which was only 44% of the solid generated from a controlled activated sludge system operated at sludge retention time of 8 days.

  10. Protistan grazing in a meromictic freshwater lake with anoxic bottom water.

    PubMed

    Oikonomou, Andreas; Pachiadaki, Maria; Stoeck, Thorsten

    2014-03-01

    Phagotrophic protists are an important mortality factor of prokaryotes in most aquatic habitats. However, no study has assessed protistan grazing as loss factor of bacterial biomass across the stratification gradient of a temperate freshwater meromictic lake. Protistan grazing effect was quantified in the mixolimnion, the transition zone, and the sulfidic anoxic monimolimnion of Lake Alatsee (Germany). Grazing experiments were performed using prey analogues from the natural prokaryotic assemblage. Daily grazing effect declined from the mixolimnion to the monimolimnion. Heterotrophic flagellates were phagotrophically active in all three water horizons and the main grazers in the monimolimnion. Pigmented flagellates accounted for 70% of total grazing in the mixolimnion and ciliates only for a small fraction of grazing in each depth. Prokaryotic biomass removal peaked in the interface, but protistan impact on the respective prokaryotic abundance was low. Grazing in the anoxic monimolimnion was negligible, with prokaryotic turnover rate being only 0.4% of standing stock. Our results support the assumption that protistan predation in anoxic waters is lower than in oxygenated ones and identify the interface as a microhabitat that supports high grazer biomass, pinpointing the importance of purple sulfur bacteria as carbon source for the upper mixolimnion and the bottom monimolimnion. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

  11. The temperature sensitivity of microbial respiration after permafrost thaw under oxic and anoxic conditions

    NASA Astrophysics Data System (ADS)

    Ernakovich, J. G.; Lynch, L.; Wallenstein, M. D.

    2013-12-01

    Carbon in permafrost soils may be vulnerable to decomposition under climate warming. The ensuing release of carbon dioxide (CO2) and methane (CH4) into the atmosphere would result in a positive climate feedback. General theory dictates that the activity of biological and chemical reactions doubles for every ten degree increase in temperature. However in Arctic soils, the temperature sensitivity of CO2 production is often larger than two, especially in experiments conducted at field relevant temperatures. Less is known about the temperature sensitivity of microbial CH4 production, which can occur after permafrost thaw if field conditions remain anoxic. We investigated the temperature sensitivity (Q10) of CO2 and CH4 production from thawed permafrost under oxic and anoxic conditions, as well as the effect of the chemical recalcitrance of soil organic matter (SOM) constituents on the Q10 of respiration. We hypothesized that (1) CH4 production under anoxic conditions would be more sensitive to increasing temperature than CO2 production under oxic conditions, and (2) the Q10 of respiration from permafrost with more labile material would be lower than for permafrost with more chemically recalcitrant material. Permafrost soil was collected from Sagwon Hills, Alaska, a region in the continuous permafrost zone. Previously, we found that the top 0-10 cm of the permafrost contained more labile material than 'deeper' (16-25 cm) permafrost cores using Fourier-transformed Mid-infrared spectroscopy (FT-IR). The 'top' and 'deeper' permafrost soils were submitted to oxic and anoxic incubation treatments at 1°C and 15°C for two weeks. CO2 and CH4 were measured and the Q10 was calculated on the cumulative gas flux. After two weeks of incubation, the Q10 of CH4 production was very high (Q10= 25.1+12.7), whereas the Q10 of CO2 production was equal to the theoretical Q10 of 2 (Q10= 2.0+0.3). The depth of the soil affected the Q10 of decomposition, however the results varied by

  12. Devonian Winnipegosis reefs of Manitoba outcrop belt - possible basin model

    SciTech Connect

    McCabe, H.R.

    1988-07-01

    Devonian Winnipegosis reefs crop out intermittently along a 350-km belt in southwestern Manitoba and represent an almost complete facies sequence ranging from central-basin reefs in the northwest to shelf-edge reefs in the southeast. In addition, structural complexities of the overlying Devonian strata mirror precisely the configuration of the underlying reefs. These outcrop data, supplemented by closely spaced stratigraphic core holes that have been sited specifically with respect to reef-controlled structures, permit development of a tentative reef model. Reef parameters are (a) size, from less than 0.5 km to a maximum of about 12 km; (b) shape, small pinnacle-type features to broad, irregular, flat-topped, atoll-like complexes, all with relatively steep margins (5/degrees/-20/degrees/); and (c) height, uniform in any given area, ranging from 40-50 m at shelf edge to 65-90 m in central basin areas. Internal reef structure shows flat central beds, and flank dips ranging from 20/degrees/ to 45/degrees/ or more in the most basinward reefs. Locally, reefs are abundantly fossiliferous, but organic framework is difficult to identify. Black bituminous mudstones in the interreef and reef-flank areas, with or without reef-derived carbonate detritus, are the only time-stratigraphic equivalents of the reefs. (The Ratner-type bituminous carbonate laminites appear to entirely postdate reef development.) Configuration of the steep-sided reefs and the well-defined shelf edge may have been controlled not only by organic (biohermal.) development, but also by anoxic containment resulting from restriction of lateral growth by anoxic bottom waters. Pinnacle reefs could thus have developed, in part, as anoxically contained pinnacle mounds rather than true bioherms.

  13. San Mateo Creek Basin

    EPA Pesticide Factsheets

    The San Mateo Creek Basin comprises approximately 321 square miles within the Rio San Jose drainage basin in McKinley and Cibola counties, New Mexico. This basin is located within the Grants Mining District (GMD).

  14. Oil exploration in nonmarine rift basins of interior Sudan

    SciTech Connect

    Schull, T.J.

    1984-04-01

    In early 1975 Chevron Overseas Petroleum Inc. commenced a major petroleum exploration effort in previously unexplored interior Sudan. With the complete cooperation of the Sudanese Government, Chevron has acquired a vast amount of geologic and geophysical data during the past 9 years. These data include extensive aeromagnetic and gravity surveys, 25,000 mi (40,200 km) of seismic data, and the results of 66 wells. This information has defined several large rift basins which are now recognized as a major part of the Central African rift system. The sedimentary basins of interior Sudan are characterized by thick Cretaceous and Tertiary nonmarine clastic sequences. Over 35,000 ft (10,600 m) of sediment have been deposited in the deepest trough, and extensive basinal areas are underlain by more than 20,000 ft (6100 m) of sediment. The depositional sequence includes thick lacustrine shales and claystones, flood plain claystones, and lacustrine, fluvial, and alluvial sandstones and conglomerates. Those lacustrine claystones which were deposited in an anoxic environment provide oil-prone source rocks. Reservoir sandstones have been found in a wide variety of nonmarine sandstone facies. The extensional tectonism which formed these basins began in the Early Cretaceous. Movement along major fault trends continued intermittently into the Miocene. This deformation resulted in a complex structural history which led to the formation of several deep fault-bounded troughs, major interbasin high trends, and complex basin flanks. This tectonism has created a wide variety of structures, many of which have become effective hydrocarbon traps.

  15. The Changing Microbial Community Along the Orca Basin Pycnocline

    NASA Astrophysics Data System (ADS)

    Hyde, A.; Nigro, L. M.; Montoya, J. P.; Joye, S. B.; Teske, A.

    2016-02-01

    Orca Basin in the Gulf of Mexico is the largest seafloor brine basin in the world, with a brine depth up to 220 m and an areal extent of 123 km2. Within the chemocline and pycnocline of Orca Basin, salinity, temperature, oxygen concentration, porewater chemistry, and microbial community composition change within approx. 100 meters, from fully oxic and marine saline deepwater conditions at 2150 m to anoxic hypersaline brine at 2250 m depth. Previous surveys of Orca Basin have detected distinct peaks of metal-cycling bacteria, and of archaeal lipids in the Orca Basin chemocline. The steep pycnocline slows down the sinking speed and therefore concentrates organic matter and microbial populations from the water column; it also allows in-situ growth of microbial populations that can take advantage of coexisting electron donors and acceptors. To survey the microbial community structure and stratification in Orca Basin, we performed a high-throughput bacterial 16S rRNA gene sequencing of filter samples from the Orca Basin deep water, chemocline and brine, collected in April 2014 on RV Atlantis. Widely spaced 50 m sample intervals from 1800 to 2350 m depth were complemented with fine-scale sampling every ten meters between 2150 and 2250 m depth, centered on the pycno- and chemocline as evident from CTD data, and with additional samples taken at 2125, 2275, and 2375 m depth. While we expect abundant and diverse chemosynthetic interface bacteria and halophiles, we are also exploring the possibility that the Orca Basin pycnocline preserves and amplifies microbial hydrocarbon signatures in the Gulf of Mexico, as in a long-term particle trap.

  16. Cretaceous sedimentation in the outer Eastern Carpathians: Implications for the facies model reconstruction of the Moldavide Basin

    NASA Astrophysics Data System (ADS)

    Roban, R. D.; Krézsek, C.; Melinte-Dobrinescu, M. C.

    2017-06-01

    The mid Cretaceous is characterized by high eustatic sea-levels with widespread oxic conditions that made possible the occurrence of globally correlated Oceanic Red Beds. However, very often, these eustatic signals have been overprinted by local tectonics, which in turn resulted in Lower Cretaceous closed and anoxic basins, as in the Eastern Carpathians. There, the black shale to red bed transition occurs in the latest Albian up to the early Cenomanian. Although earlier studies discussed the large-scale basin configuration, no detailed petrography and sedimentology study has been performed in the Eastern Carpathians. This paper describes the Hauterivian to Turonian lithofacies and interprets the depositional settings based on their sedimentological features. The studied sections crop out only in tectonic half windows of the Eastern Carpathians, part of the Vrancea Nappe. The lithofacies comprises black shales interbedded with siderites and sandstones, calcarenites, marls, radiolarites and red shales. The siliciclastic muddy lithofacies in general reflects accumulation by suspension settling of pelagites and hemipelagites in anoxic (black shale) to dysoxic (dark gray and gray to green shales) and oxic (red shales) conditions. The radiolarites alternate with siliceous shales and are considered as evidence of climate changes. The sandstones represent mostly low and high-density turbidite currents in deep-marine lobes, as well as channel/levee systems. The source area is an eastern one, e.g., the Eastern Carpathians Foreland, given the abundance of low grade metamorphic clasts. The Hauterivian - lower Albian sediments are interpreted as deep-marine, linear and multiple sourced mud dominated systems deposited in a mainly anoxic to dysoxic basin. The anoxic conditions existed in the early to late Albian, but sedimentation changed to a higher energy mud/sand-dominated submarine channels and levees. This coarsening upwards tendency is interpreted as the effect of the

  17. Oxic and anoxic mineralization of simple carbon substrates in peat at low temperatures

    NASA Astrophysics Data System (ADS)

    Segura, Javier; Sparrman, Tobias; Nilsson, Mats; Schleucher, Jürgen; Öquist, Mats

    2016-04-01

    Northern peatlands store approximately one-quarter of the world's soil carbon and typically act as net carbon sinks. However a large fraction of the carbon fixed during the growing season can be emitted back to the atmosphere during winter as CO2 and CH4, despite low temperatures and frozen conditions, making low temperature biogeochemical processes crucial for the long-term net ecosystem carbon balance. However, the metabolic processes driving carbon mineralization under winter conditions are poorly understood and whether or not peat microbial communities can maintain metabolic activity at temperatures below freezing is uncertain. Here we present results from an incubation study aimed at elucidating the potential of peat microbial communities to mineralize simple carbon substrates to CO2 and CH4 at low temperatures. Peat samples from the acrotelm were amended with [13C]- glucose and incubated at -5 °C, -3 °C, +4 °C, and +9 °C under both oxic and anoxic conditions, and rates of CO2 and CH4 production were determined. In addition, incorporation of the labelled substrate into phospholipid fatty acids (PLFAs) were determined to account for microbial growth during mineralization and the metabolic partitioning between catabolic and anabolic activity. Biogenic [13C]-CO2 was produced from the added substrate in peat samples incubated both under oxic and anoxic conditions. Under oxic conditions the production rates were 3.5, 2.3, 0.3 and 0.07 mg CO2 g SOM-1day-1 at +9 °C, +4 °C, -3 °C and -5 °C, respectively, and corresponding rates for anoxic conditions were 1.1, 1.0, 0.03 and 0.01 mg CO2 g SOM-1day-1. Consequently the observed Q10 values of the temperature sensitivity under both oxic and anoxic conditions increased dramatically upon soil freezing. However, anoxic mineralization appears less sensitive to temperature as compared to when oxygen is present. Methane was also produced and detected across the range of the incubation temperatures in the anoxic

  18. Anoxic carbon degradation in Arctic sediments: Microbial transformations of complex substrates

    NASA Astrophysics Data System (ADS)

    Arnosti, C.; Finke, N.; Larsen, O.; Ghobrial, S.

    2005-05-01

    Complex substrates are degraded in anoxic sediments by the concerted activities of diverse microbial communities. To explore the effects of substrate complexity on carbon transformations in permanently cold anoxic sediments, four substrates— Spirulina cells, Isochrysis cells, and soluble high molecular weight carbohydrate-rich extracts of these cells (Spir-Ex and Iso-Ex)—were added to sediments collected from Svalbard. The sediments were homogenized, incubated anaerobically in gas-tight bags at 0°C, and enzyme activities, fermentation, and terminal respiration were monitored over a 1134 h time course. All substrate additions yielded a fraction (8%-13%) of carbon that was metabolized to CO 2 over the first 384 h of incubation. The timecourse of VFA (volatile fatty acid) production and consumption, as well as the suite of VFAs produced, was similar for all substrates. After this phase, pathways of carbon degradation diverged, with an additional 43%, 32%, 33%, and 8% of Isochrysis, Iso-Ex, Spirulina, and Spir-Ex carbon respired to CO 2 over the next 750 h of incubation. Somewhat surprisingly, the soluble, carbohydrate-rich extracts did not prove to be more labile substrates than the whole cells from which they were derived. Although Spirulina and Iso-Ex differed in physical and chemical characteristics (solid/soluble, C/N ratio, lipid and carbohydrate content), nearly identical quantities of carbon were respired to CO 2. In contrast, only 15% of Spir-Ex carbon was respired, despite the initial burst of activity that it fueled, its soluble nature, and its relatively high (50%) carbohydrate content. The microbial community in these cold anoxic sediments clearly has the capacity to react rapidly to carbon input; extent and timecourse of remineralization of added carbon is similar to observations made at much higher temperatures in temperate sediments. The extent of carbon remineralization from these specific substrates, however, would not likely have been predicted

  19. Redox processes in pore water of anoxic sediments with shallow gas.

    PubMed

    Ramírez-Pérez, A M; de Blas, E; García-Gil, S

    2015-12-15

    The Ría de Vigo (NW Spain) has a high organic matter content and high rates of sedimentation. The microbial degradation of this organic matter has led to shallow gas accumulations of methane, currently distributed all along the ría. These peculiar characteristics favor the development of anoxic conditions that can determine the dynamics of iron and manganese. In order to study the role played by iron and manganese in the processes that take place in anoxic sediments with shallow gas, four gravity cores were retrieved in anoxic sediments of the Ría de Vigo in November 2012. Methane was present in two of them, below 90cm in the inner zone and below 200cm, in the outer zone. Pore water was collected and analyzed for vertical profiles of pH, sulfide, sulfate, iron and manganese concentrations. Sulfate concentrations decreased with depth but never reached the minimum detection limit. High sulfide concentrations were measured in all cores. The highest sulfide concentrations were found in the inner zone with methane and the lowest were in the outer zone without methane. Concentrations of iron and manganese reached maximum values in the upper layers of the sediment, decreasing with depth, except in the outer zone without gas, where iron and manganese concentration increased strongly toward the bottom of the sediment. In areas with shallow gas iron reduction, sulfate reduction and methane production processes coexist, showing that the traditional redox cascade is highly simplified and suggesting that iron may be involved in a cryptic sulfur cycle and in the oxidation of methane.

  20. Microbial responses to chitin and chitosan in oxic and anoxic agricultural soil slurries

    NASA Astrophysics Data System (ADS)

    Wieczorek, A. S.; Hetz, S. A.; Kolb, S.

    2014-02-01

    Chitin is the second most abundant biopolymer in terrestrial ecosystems and is subject to microbial degradation. Chitin can be deacetylated to chitosan or can be hydrolyzed to N,N'-diacetylchitobiose and oligomers of N-acetylglucosamine by aerobic and anaerobic microorganisms. Which pathway of chitin hydrolysis is preferred by soil microbial communities has previously been unknown. Supplementation of chitin stimulated microbial activity under oxic and anoxic conditions in agricultural soil slurries, whereas chitosan had no effect. Thus, the soil microbial community likely was more adapted to chitin as a substrate. In addition, this finding suggested that direct hydrolysis of chitin was preferred to the pathway that starts with deacetylation. Chitin was apparently degraded by aerobic respiration, ammonification, and nitrification to carbon dioxide and nitrate under oxic conditions. When oxygen was absent, fermentation products (acetate, butyrate, propionate, hydrogen, carbon dioxide) and ammonia were detected, suggesting that butyric and propionic acid fermentation were along with ammonification likely responsible for apparent anaerobic chitin degradation. In total, 42 different chiA genotypes were detected of which twenty were novel at an amino acid sequence dissimilarity of >50%. Various chiA genotypes responded to chitin supplementation and affiliated with a novel deep-branching bacterial chiA genotype (anoxic conditions), genotypes of Beta- and Gammaproteobacteria (oxic and anoxic conditions), and Planctomycetes (oxic conditions). Thus, this study provides evidence that detected chitinolytic bacteria were catabolically diverse and occupied different ecological niches with regard to oxygen availability enabling chitin degradation under various redox conditions at the level of the community.

  1. Microbial responses to chitin and chitosan in oxic and anoxic agricultural soil slurries

    NASA Astrophysics Data System (ADS)

    Wieczorek, A. S.; Hetz, S. A.; Kolb, S.

    2014-06-01

    Microbial degradation of chitin in soil substantially contributes to carbon cycling in terrestrial ecosystems. Chitin is globally the second most abundant biopolymer after cellulose and can be deacetylated to chitosan or can be hydrolyzed to N,N'-diacetylchitobiose and oligomers of N-acetylglucosamine by aerobic and anaerobic microorganisms. Which pathway of chitin hydrolysis is preferred by soil microbial communities is unknown. Supplementation of chitin stimulated microbial activity under oxic and anoxic conditions in agricultural soil slurries, whereas chitosan had no effect. Thus, the soil microbial community likely was more adapted to chitin as a substrate. In addition, this finding suggested that direct hydrolysis of chitin was preferred to the pathway that starts with deacetylation. Chitin was apparently degraded by aerobic respiration, ammonification, and nitrification to carbon dioxide and nitrate under oxic conditions. When oxygen was absent, fermentation products (acetate, butyrate, propionate, hydrogen, and carbon dioxide) and ammonia were detected, suggesting that butyric and propionic acid fermentation, along with ammonification, were likely responsible for anaerobic chitin degradation. In total, 42 different chiA genotypes were detected of which twenty were novel at an amino acid sequence dissimilarity of less than 50%. Various chiA genotypes responded to chitin supplementation and affiliated with a novel deep-branching bacterial chiA genotype (anoxic conditions), genotypes of Beta- and Gammaproteobacteria (oxic and anoxic conditions), and Planctomycetes (oxic conditions). Thus, this study provides evidence that detected chitinolytic bacteria were catabolically diverse and occupied different ecological niches with regard to oxygen availability enabling chitin degradation under various redox conditions on community level.

  2. Shewanella oneidensis MR-1 sensory box protein involved in aerobic and anoxic growth.

    PubMed

    Sundararajan, A; Kurowski, J; Yan, T; Klingeman, D M; Joachimiak, M P; Zhou, J; Naranjo, B; Gralnick, J A; Fields, M W

    2011-07-01

    Although little is known of potential function for conserved signaling proteins, it is hypothesized that such proteins play important roles to coordinate cellular responses to environmental stimuli. In order to elucidate the function of a putative sensory box protein (PAS domains) in Shewanella oneidensis MR-1, the physiological role of SO3389 was characterized. The predicted open reading frame (ORF) encodes a putative sensory box protein that has PAS, GGDEF, and EAL domains, and an in-frame deletion mutant was constructed (ΔSO3389) with approximately 95% of the ORF deleted. Under aerated conditions, wild-type and mutant cultures had similar growth rates, but the mutant culture had a lower growth rate under static, aerobic conditions. Oxygen consumption rates were lower for mutant cultures (1.5-fold), and wild-type cultures also maintained lower dissolved oxygen concentrations under aerated growth conditions. When transferred to anoxic conditions, the mutant did not grow with fumarate, iron(III), or dimethyl sulfoxide (DMSO) as electron acceptors. Biochemical assays demonstrated the expression of different c-type cytochromes as well as decreased fumarate reductase activity in the mutant transferred to anoxic growth conditions. Transcriptomic studies showed the inability of the mutant to up-express and down-express genes, including c-type cytochromes (e.g., SO4047/SO4048, SO3285/SO3286), reductases (e.g., SO0768, SO1427), and potential regulators (e.g., SO1329). The complemented strain was able to grow when transferred from aerobic to anoxic growth conditions with the tested electron acceptors. The modeled structure for the SO3389 PAS domains was highly similar to the crystal structures of FAD-binding PAS domains that are known O2/redox sensors. Based on physiological, genomic, and bioinformatic results, we suggest that the sensory box protein, SO3389, is an O2/redox sensor that is involved in optimization of aerobic growth and transitions to anoxia in S

  3. Enzymatic control of glycogenolysis during anoxic submergence in the freshwater turtle Trachemys scripta.

    PubMed

    Mehrani, H; Storey, K B

    1995-08-01

    Freshwater turtles Trachemys scripta elegans endure prolonged severe hypoxia, and even complete anoxia, while diving or hibernating underwater. Metabolic adaptations supporting survival include the activation of glycogenolysis and glucose output from liver, as well as strong metabolic rate depression. The present study analyzes the enzymes of both the phosphorolytic (glycogen phosphorylase, phosphorylase b kinase, cAMP-dependent protein kinase) and glucosidic (alpha-glucosidase) pathways of glycogenolysis in turtle organs. Turtles were subjected to 5 hr of submergence in N2-bubbled water at 7 degrees C and then activities of phosphorolytic and glucosidic enzymes were assayed in liver, heart, brain, and red and white skeletal muscle, and compared with aerobic controls. In vitro incubations also assessed protein kinase A control of phosphorolytic enzymes. A functional enzyme cascade system for the activation of glycogen phosphorylase was found in all organs, and both phosphorylase and phosphorylase kinase were stimulated by in vitro incubation with the catalytic subunit of cAMP-dependent protein kinase. Anoxic submergence led to significant increases in phosphorylase activities in liver and heart (phosphorylase a rose 2- and 2.5-fold, respectively) but phosphorylase kinase and protein kinase A activities in liver were reduced after 5 hr exposure. Both acidic (pH 4) and neutral (pH 7) forms of alpha-glucosidase were detected in all five organs with highest activities in liver. Activity of acid alpha-glucosidase, which degrades lysosomal glycogen, increased by 2-fold in liver during anoxic submergence. The data show that glycogen breakdown in turtle liver during anoxic submergence may result from coordinated activations of both the cytoplasmic phosphorolytic and the lysosomal glucosidic pathways of glycogenolysis.

  4. [Construction and evaluation of an engineered bacterial strain for producing lipopeptide under anoxic conditions].

    PubMed

    Liang, Xiao-long; Zhao, Feng; Shi, Rong-jiu; Ban, Yun-he; Zhou, Ji-dong; Han, Si-qin; Zhang, Ying

    2015-08-01

    Biosurfactant-facilitated oil recovery is one of the most important aspects of microbial enhanced oil recovery (MEOR). However, the biosurfactant production by biosurfactant-producing microorganisms, most of which are aerobes, is severely suppressed due to the in-situ anoxic conditions within oil reservoirs. In this research, we successfully engineered a strain JD-3, which could grow rapidly and produce lipopeptide under anoxic conditions, by protoplast confusion using a Bacillus amyloliquefaciens strain BQ-2 which produces biosurfactant aerobically, and a facultative anaerobic Pseudomonas stutzeri strain DQ-1 as parent strains. The alignment of 16S rDNA sequence (99% similarity) and comparisons of cell colony morphology showed that fusant JD-3 was closer to the parental strain B. amyloliquefaciens BQ-2. The surface tension of culture broth of fusant JD-3, after 36-hour cultivation under anaerobic conditions, decreased from initially 63.0 to 32.5 mN · m(-1). The results of thin layer chromatography and infrared spectrum analysis demonstrated that the biosurfactant produced by JD-3 was lipopeptide. The surface-active lipopeptide had a low critical micelle concentration (CMC) of 90 mg · L(-1) and presented a good ability to emulsify various hydrocarbons such as crude oil, liquid paraffin, and kerosene. Strain JD-3 could utilize peptone as nitrogen source and sucrose, glucose, glycerin or other common organics as carbon sources for anaerobic lipopeptide synthesis. The subculture of fusant JD-3 showed a stable lipopeptide-producing ability even after ten serial passages. All these results indicated that fusant JD-3 holds a great potential to microbially enhance oil recovery under anoxic conditions.

  5. Bacterial Adaptation of Respiration from Oxic to Microoxic and Anoxic Conditions: Redox Control

    PubMed Central

    Bueno, Emilio; Mesa, Socorro; Bedmar, Eulogio J.; Richardson, David J.

    2012-01-01

    Abstract Under a shortage of oxygen, bacterial growth can be faced mainly by two ATP-generating mechanisms: (i) by synthesis of specific high-affinity terminal oxidases that allow bacteria to use traces of oxygen or (ii) by utilizing other substrates as final electron acceptors such as nitrate, which can be reduced to dinitrogen gas through denitrification or to ammonium. This bacterial respiratory shift from oxic to microoxic and anoxic conditions requires a regulatory strategy which ensures that cells can sense and respond to changes in oxygen tension and to the availability of other electron acceptors. Bacteria can sense oxygen by direct interaction of this molecule with a membrane protein receptor (e.g., FixL) or by interaction with a cytoplasmic transcriptional factor (e.g., Fnr). A third type of oxygen perception is based on sensing changes in redox state of molecules within the cell. Redox-responsive regulatory systems (e.g., ArcBA, RegBA/PrrBA, RoxSR, RegSR, ActSR, ResDE, and Rex) integrate the response to multiple signals (e.g., ubiquinone, menaquinone, redox active cysteine, electron transport to terminal oxidases, and NAD/NADH) and activate or repress target genes to coordinate the adaptation of bacterial respiration from oxic to anoxic conditions. Here, we provide a compilation of the current knowledge about proteins and regulatory networks involved in the redox control of the respiratory adaptation of different bacterial species to microxic and anoxic environments. Antioxid. Redox Signal. 16, 819–852. PMID:22098259

  6. Coupled BAS and anoxic USB system to remove urea and formaldehyde from wastewater.

    PubMed

    Campos, J L; Sánchez, M; Mosquera-Corral, A; Méndez, R; Lema, J M

    2003-08-01

    Wastewater containing formaldehyde and urea was treated using a coupled system consisting of a biofilm airlift suspension (BAS) reactor and an anoxic upflow sludge blanket (USB) reactor. The anoxic USB reactor was used to carry out denitrification and urea hydrolysis, while the BAS reactor was used to carry out nitrification. In a first step, individual experiments were carried out to investigate the effects of both compounds on the nitrifying and denitrifying biomass. The BAS reactor was fed with a synthetic medium containing 500 mg N-NH4(+)l(-1) and 100mg N-urea l(-1), that were added continuously to this medium. Neither urea hydrolysis nor inhibition of nitrification was observed. Nitrification efficiency decreased when formaldehyde was fed during shocks at concentrations of 40, 80 and 120 mg C-formaldehyde l(-1). The anoxic USB reactor was fed with a synthetic medium containing nitrate, formaldehyde and urea. Concentrations of formaldehyde in the reactor of 100-120 mg C-formaldehyde l(-1) caused a decrease in the denitrification and urea hydrolysis rates. In a second step, the coupled system was operated at recycling ratios (R) of 3 and 9. Fed C/N ratios of 0.58, 1.0 and 1.5 g C-formaldehyde g(-1) N-NH4(+) were used for every recycling ratio. The maximum nitrogen removal percentages were achieved at a C/N ratio of 1.0 g C-formaldehyde g(-1) N-NH4(+) for both recycling ratios. A fed C/N ratio of 1.5 g C-formaldehyde g(-1) N-NH4(+) caused a decrease in the efficiency of the system with respect to nitrogen removal, due to the presence of formaldehyde in the BAS reactor, which decreased the nitrification. Formaldehyde was completely removed in the BAS reactor and a heterotrophic layer formed around the nitrifying biofilm.

  7. Vasoactivity of hydrogen sulfide in normoxic and anoxic turtles (Trachemys scripta).

    PubMed

    Stecyk, Jonathan A W; Skovgaard, Nini; Nilsson, Göran E; Wang, Tobias

    2010-05-01

    Systemic vascular resistance (R(sys)) of freshwater turtles increases substantially during anoxia, but the underlying mechanisms are not fully understood. We investigated whether hydrogen sulfide (H(2)S), an endogenously produced metabolite believed to be an O(2) sensor/transducer of vasomotor tone, contributes to the increased R(sys) of anoxic red-eared slider turtles (Trachemys scripta). Vascular infusion of the H(2)S donor NaHS in anesthetized turtles at 21 degrees C and fully recovered normoxic turtles at 5 degrees C and 21 degrees C revealed H(2)S to be a potent vasoconstrictor of the systemic circulation. Likewise, wire myography of isolated turtle mesenteric and pulmonary arteries demonstrated H(2)S to mediate an anoxia-induced constriction. Intriguingly, however, NaHS did not exert vasoconstrictory effects during anoxia (6 h at 21 degrees C; 14 days at 5 degrees C) when plasma H(2)S concentration, estimated from the colorimetric measurement of plasma acid-labile sulfide concentration, likely increased by approximately 3- and 4-fold during anoxia at 21 degrees C, and 5 degrees C, respectively. Yet, blockade of endogenous H(2)S production by DL-propargylglycine or hydroxylamine (0.44 mmol/kg) partially reversed the decreased systemic conductance (G(sys)) exhibited by 5 degrees C anoxic turtles. These findings suggest that the signal transduction pathway of H(2)S-mediated vasoactivity is either maximally activated in the systemic circulation of anoxic turtles and/or that it is oxygen dependent.

  8. Vivianite precipitation and phosphate sorption following iron reduction in anoxic soils.

    PubMed

    Heiberg, Lisa; Koch, Christian Bender; Kjaergaard, Charlotte; Jensen, Henning S; Hans Christian, B Hansen

    2012-01-01

    Phosphorus retention in lowland soils depends on redox conditions. The aim of this study was to evaluate how the Fe(III) reduction degree affects phosphate adsorption and precipitation. Two similarly P-saturated, ferric Fe-rich lowland soils, a sandy and a peat soil, were incubated under anaerobic conditions. Mössbauer spectroscopy demonstrated that Fe(III) in the sandy soil was present as goethite and phyllosilicates, whereas Fe(III) in the peat soil was mainly present as polynuclear, Fe-humic complexes. Following anoxic incubation, extensive formation of Fe(II) in the solids occurred. After 100 d, the Fe(II) production reached its maximum and 34% of the citrate-bicarbonate-dithionite extractable Fe (Fe(CBD)) was reduced to Fe(II) in the sandy soil. The peat soil showed a much faster reduction of Fe(III) and the maximum reduction of 89% of Fe(CBD) was reached after 200 d. Neoformation of a metavivianite/vivianite phase under anoxic conditions was identified by X-ray diffraction in the peat. The sandy soil exhibited small changes in the point of zero net sorption (EPC₀) and P(i) desorption with increasing Fe(III) reduction, whereas in the peat soil P desorption increased from 80 to 3100 μmol kg⁻¹ and EPC₀ increased from 1.7 to 83 μM, after 322 d of anoxic incubation. The fast Fe(III) reduction made the peat soils particularly vulnerable to changes in redox conditions. However, the precipitation of vivianite/metavivianite minerals may control soluble P(i) concentrations to between 2 and 3 μM in the long term if the soil is not disturbed. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  9. Simultaneous carbon and nitrogen removal in anoxic-aerobic circulating fluidized bed biological reactor (CFBBR).

    PubMed

    Cui, Y; Nakhla, G; Zhu, J; Patel, A

    2004-06-01

    Biological nutrient removal (BNR) in municipal wastewater treatment to remove carbonaceous substrates and nutrients, has recently become increasingly popular worldwide due to increasingly stringent regulations. Biological fluidized bed (BFB) technology, which could be potentially used for BNR, can provide some advantages such as high efficiency and a compact structure. This work shows the results of simultaneous elimination of organic carbon and nitrogen using a circulating fluidized bed biological reactor (CFBBR, which has been developed recently for chemical engineering processes. The CFBBR has two fluidized beds, running as anoxic and aerobic processes to accomplish simultaneous nitrification and denitrification, with continuous liquid recirculation through the anoxic bed and the aerobic bed. Soluble COD concentrations in the effluent ranging from 4 to 20 mg l(-1) were obtained at varying COD loading rates; ammonia nitrogen removal efficiencies averaged in excess of 99% at a minimum total hydraulic retention time (HRT) of 2.0 hours over a temperature range of 25 degrees C to 28 degrees C. Effluent nitrate nitrogen concentration of less than 5 mg l(-1) was achieved by increasing effluent recycle rate. No nitrite accumulation was observed either in the anoxic bed or in the aerobic bed. The system was able to treat grit chamber effluent wastewater at a HRT of 2.0 hours while achieving average effluent BOD, COD, NH3-N, TKN, nitrates, total phosphate, TSS and VSS concentrations of 10 mg l(-1), 18 mg l(-1), 1.3 mg l(-1), 1.5 mg l(-1), 7 mg l(-1), 2.0 mg l(-1), 10 mg l(-1) and 8 mg l(-1) respectively. The CFBBR appears to be not only an excellent alternative for conventional activated sludge type BNR technologies but also capable of processing much higher loadings that are suitable for industrial applications.

  10. PROGRESSIVE VENTILATION OF THE OCEANS - POTENTIAL FOR RETURN TO ANOXIC CONDITIONS IN THE POST-PALEOZOIC

    SciTech Connect

    Wilde, Pat; Berry, William B.N.

    1980-09-01

    After the ventilation of the residual anoxic layer in the late Paleozoic (Berry and Wilde, 1978) a return to ephemeral anoxic conditions in the ocean is suggested by anoxic sediments found in the Mesozoic cores of the deep-sea drilling program (Schlanger and Jenkyns 1977, and Theide and Van Andel 1977). A preliminary physical oceanographic model is presented to explain the development of oxygen depleted layers in mid-waters below the surface wind-mixed layer during non-glacial climates. The model shows the range of temperature, salinity and density values for hypothetical water masses for two climatically related oceanographic situations: Case A where bottom waters are formed at mid-latitudes at the surface salinity maxima, and Case B where bottom waters are produced at high latitudes but not by sea-ice formation as in the modern ocean. The hypothetical water masses are characterized by examples from the modern ocean and extrapolation to non-glacial times is made by eliminating water masses produced by or influenced by sea-ice formation in modern glacial times. The state of oxidation is made by plotting the model water masses on an oxygen saturation diagram and comparing the relative oxygen capacity with modern conditions of zonal organic productivity. The model indicates for Case A (high latitude temperatures above 5°C) two oxygen, depleted layers in the equatorial regions (1) from about 200m to the depth of completed oxidation of surface material separated by an oxygenated zone to (2) a deep depleted zone along the base of the pycnocline at 2900 M. The deep depleted zone extends along the Case A pycnocline polarward toward the high latitude productivity maximum. For case B with a pycnocline at about 1500m the deep anoxic layer is not sustained. Considerations of density only, suggest that neutral stratification and the potential for overturn is enhanced for climates transitional between Case A and Case B where the density contrast between major water masses

  11. Jellyfish Lake, Palau: early diagenesis of organic matter in sediments of an anoxic marine lake

    USGS Publications Warehouse

    Orem, W.H.; Burnett, W.C.; Landing, W.M.; Lyons, W.B.; Showers, W.

    1991-01-01

    The major postdepositional change in the sedimentary organic matter is carbohydrate biodegradation. Lignin and aliphatic substances are preserved in the sediments. Dissolved organic matter in pore waters is primarily composed of carbohydrates, reflecting the degradation of sedimentary carbohydrates. Rate constants for organic carbon degradation and sulfate reduction in sediments of the lake are about 10?? lower than in other anoxic sediments. This may reflect the vascular plant source and partly degraded nature of the organic matter reaching the sediments of the lake. -from Authors

  12. Anoxic atmospheres on Mars driven by volcanism: Implications for past environments and life

    NASA Astrophysics Data System (ADS)

    Sholes, Steven F.; Smith, Megan L.; Claire, Mark W.; Zahnle, Kevin J.; Catling, David C.

    2017-07-01

    Mars today has no active volcanism and its atmosphere is oxidizing, dominated by the photochemistry of CO2 and H2O. Mars experienced widespread volcanism in the past and volcanic emissions should have included reducing gases, such as H2 and CO, as well as sulfur-bearing gases. Using a one-dimensional photochemical model, we consider whether plausible volcanic gas fluxes could have switched the redox-state of the past martian atmosphere to reducing conditions. In our model, the total quantity and proportions of volcanic gases depend on the water content, outgassing pressure, and oxygen fugacity of the source melt. We find that, with reasonable melt parameters, the past martian atmosphere (∼3.5 Gyr to present) could have easily reached reducing and anoxic conditions with modest levels of volcanism, >0.14 km3 yr-1, which are well within the range of estimates from thermal evolution models or photogeological studies. Counter-intuitively we also find that more reducing melts with lower oxygen fugacity require greater amounts of volcanism to switch a paleo-atmosphere from oxidizing to reducing. The reason is that sulfur is more stable in such melts and lower absolute fluxes of sulfur-bearing gases more than compensate for increases in the proportions of H2 and CO. These results imply that ancient Mars should have experienced periods with anoxic and reducing atmospheres even through the mid-Amazonian whenever volcanic outgassing was sustained at sufficient levels. Reducing anoxic conditions are potentially conducive to the synthesis of prebiotic organic compounds, such as amino acids, and are therefore relevant to the possibility of life on Mars. Also, anoxic reducing conditions should have influenced the type of minerals that were formed on the surface or deposited from the atmosphere. We suggest looking for elemental polysulfur (S8) as a signature of past reducing atmospheres. Finally, our models allow us to estimate the amount of volcanically sourced atmospheric

  13. Arsenic in an Alkaline AMD Treatment Sludge: Characterization and Stability Under Prolonged Anoxic Conditions

    SciTech Connect

    Beauchemin, S.; Fiset, J; Poirier, G; Ablett, J

    2010-01-01

    Lime treatment of acid mine drainage (AMD) generates large volumes of neutralization sludge that are often stored under water covers. The sludge consists mainly of calcite, gypsum and a widespread ferrihydrite-like Fe phase with several associated species of metal(loid) contaminants. The long-term stability of metal(loid)s in this chemically ill-defined material remains unknown. In this study, the stability and speciation of As in AMD sludge subjected to prolonged anoxic conditions is determined. The total As concentration in the sludge is 300 mg kg{sup -1}. In the laboratory, three distinct water cover treatments were imposed on the sludge to induce different redox conditions (100%N{sub 2}, 100%N{sub 2} + glucose, 95%N{sub 2}:5%H{sub 2}). These treatments were compared against a control of oxidized, water-saturated sludge. Electron micro-probe (EMP) analysis and spatially resolved synchrotron X-ray fluorescence (SXRF) results indicate that As is dominantly associated with Fe in the sludge. In all treatments and throughout the experiment, measured concentrations of dissolved As were less than 5 {micro}g L{sup -1}. Dissolved Mn concentration in the N{sub 2} + glucose treatment increased significantly compared to other treatments. Manganese and As K-edge X-ray absorption near edge structure spectroscopy (XANES) analyses showed that Mn was the redox-active element in the solid-phase, while As was stable. Arsenic(V) was still the dominant species in all water-covered sludges after 9 months of anoxic treatments. In contrast, Mn(IV) in the original sludge was partially reduced into Mn(II) in all water-covered sludges. The effect was most pronounced in the N{sub 2} + glucose treatment, suggesting microbial reduction. Micro-scale SXRF and XANES analysis of the treated sludge showed that Mn(II) accumulated in areas already enriched in Fe and As. Overall, the study shows that AMD sludges remain stable under prolonged anoxic conditions. External sources of chemical reductants

  14. Functional neuroimaging after severe anoxic brain injury in children may reveal preserved, yet covert, cognitive function.

    PubMed

    Owen, Adrian M

    2017-10-01

    A growing body of evidence has confirmed that, after severe brain injury in adults, motoric and task-dependent factors that are essential for reliable communication, frequently interfere with an accurate assessment of cognitive status. In the current study, resting state functional magnetic resonance imaging (fMRI) in children who have sustained an anoxic brain injury following a near drowning incident suggests a similar pattern; preserved cognition amidst severe motoric impairment that effectively precludes accurate clinical diagnosis at the bedside. Hum Brain Mapp 38:4832-4833, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  15. Systematics of past changes in ocean ventilation: a comparison of Cretaceous Ocean Anoxic Event 2 and Pleistocene to Holocene Oxygen Minimum Zones

    NASA Astrophysics Data System (ADS)

    Schönfeld, J.; Kuhnt, W.; Erdem, Z.; Flögel, S.; Glock, N.; Aquit, M.; Frank, M.; Holbourn, A.

    2014-09-01

    Present day oceans are generally well ventilated except mid-depth oxygen minimum zones (OMZs) under high surface water productivity regimes, regions of sluggish circulation, and restricted marginal basins. In the Mesozoic, however, entire oceanic basins transiently became dysoxic or even anoxic. In particular the Cretaceous Ocean Anoxic Events (OAEs) were characterised by laminated organic-carbon rich shales and low-oxygen indicating trace fossil assemblages preserved in the sedimentary record. Yet both, qualitative and quantitative assessments of intensity and extent of Cretaceous near-bottom water oxygenation have been hampered by deep or long-term diagenesis and the evolution of marine biota serving as oxygen indicators in today's ocean. Sedimentary features similar to those found in Cretaceous strata were observed in deposits underlying Recent OMZs, where bottom-water oxygen levels, the flux of organic matter, and benthic life are well known. Their implications for constraining past bottom-water oxygenation are addressed in this review, with emphasis on comparing OMZ sediments from the Peruvian upwelling with deposits of the late Cenomanian OAE 2 from the Atlantic NW African shelf. Holocene laminated sediments were encountered at bottom-water oxygen levels of <7 μmol kg-1 under the Peruvian upwelling and <5 μmol kg-1 in California Borderland basins and the Pakistan Margin. Changes of sediment input on seasonal to decadal time scales are necessary to create laminae of different composition. However, bottom currents may shape similar textures that are difficult to discern from primary seasonal laminae in sediment cores. The millimetre-sized trace fossil Chondrites was commonly found in Cretaceous strata and Recent oxygen-depleted environments where its diameter increased with oxygen levels from 5 to 45 μmol kg-1. This ichnogenus has not been reported from Peruvian sediments but cm-sized crab burrows appeared around 10 μmol kg-1, which may indicate a minimum

  16. Is the Coniacian-Santonian OAE3 a real and global anoxic event ? Insights from Spain, Texas and Egypt

    NASA Astrophysics Data System (ADS)

    Bomou, Brahimsamba; Adatte, Thierry; De Kaenel, Eric; Spangenberg, Jorge; Gertsch, Brian; Föllmi, Karl B.

    2013-04-01

    Several oceanic anoxic episodes (OAE) occurred on a worldwide scale throughout the Cretaceous. They are defined by the widespread accumulation of laminated organic-rich sediments and coincide with a positive excursion in δ13C. The Coniacian-Santonian OAE (= OAE3) is less well known and appears less expressed than the early Aptian and latest Cenomanian OAEs. This OAE appears not to be truly important on a global scale but was more dependent on local or regional conditions, as suggested by the paleogeographic distribution of organic-rich sediments. These are mainly restricted to the equatorial and South Atlantic basins and the Western Interior Seaway, and therein mostly to shallow-water settings and epicontinental seas. The mechanisms and paleoenvironmental conditions leading to and through OAE3 are poorly known, particularly with regards to the marine phosphorus cycle and changes therein, and to the climate conditions in general. Specifically, in our study, we focus on bulk and clay mineralogy, phosphorus, carbon isotopes, high-resolution biostratigraphy, and changes in climate and primary productivity. Several sections from different paleogeographic areas at different paleodepths were studied. Two sections were investigated, are candidates for the global boundary stratotype section and point (GSSP), Olazagutia (NW Spain) and Ten Mile Creek-Arbor Park (Texas, USA); an additional section was analysed in Gabal Ekma (Sinai, Egypt), which exhibits several layers enriched in organic matter associated with extensive bonebeds. In the Olazagutia section, the inoceramid Platyceramus undulatoplicatus, which marks the base of Santonian, occurs well above the Coniacian-Santonian boundary indicated by nannofossil biostratigraphy, and its first occurrence appears to have been environmentally controlled. In Texas, several bentonite layers have been recognized just above the proposed Coniacian-Santonian boundary, which may provide a more accurate age. Based on a weathering index

  17. Evaluation of metal partitioning and mobility in a sulfidic mine tailing pile under oxic and anoxic conditions.

    PubMed

    Pinto, Patricio X; Al-Abed, Souhail R; Holder, Christopher; Reisman, David J

    2014-07-01

    Mining-influenced water emanating from mine tailings and potentially contaminating surface water and groundwater is one of the most important environmental issues linked to the mining industry. In this study, two subsets of Callahan Mine tailings (mainly comprised of silicates, sulfides, and carbonates) were collected using sealed containers, which allowed keeping the samples under anoxic conditions during transportation and storage. Among the potential contaminants, in spite of high concentrations of Cu, Mn, Pb, and Zn present in the solid mine tailings, only small amounts of Mn and Zn were found in the overlying pore water. The samples were subjected to leaching tests at different reduction-oxidation (redox) conditions to compare metal and S mobilization under oxic and anoxic conditions. It was observed that Cd, Cu, Mn, Pb, S, and Zn were mobilized at higher rates under oxic conditions, while Fe was mobilized at a higher rate under anoxic conditions in comparable constant pH experiments. These results suggest that metal mobilization is significantly impacted by redox conditions. When anoxic metal mobilization assessment is required, it is recommended to always maintain anoxic conditions because oxygen exposure may affect metal mobilization. A sequential extraction performed under oxic conditions revealed that most of the metals in the samples were associated with the sulfidic fraction and that the labile fraction was associated with Mn and moderate amounts of Pb and Zn.

  18. Effects of Methyl Jasmonate on Acute Stress Responses in Mice Subjected to Forced Swim and Anoxic Tests.

    PubMed

    Aluko, Oritoke M; Umukoro, Solomon; Annafi, Olajide S; Adewole, Folashade A; Omorogbe, Osarume

    2015-01-01

    Methyl jasmonate (MJ) is an anti-stress hormone released by plants in response to external stressors and aids adaptation to stress. In this study, we evaluated the anti-stress activity of MJ using the forced swim endurance test (FSET) and anoxic tolerance test in mice. Male Swiss mice were given MJ (25-100 mg/kg, i.p) 30 min before the FSET and anoxic test were carried out. The first occurrence of immobility, duration of immobility, time spent in active swimming, and latency to exhaustion were assessed in the FSET. The onset to anoxic convulsion was measured in the anoxic tolerance test. MJ significantly (p < 0.05) delayed the first occurrence of immobility and shortened the period of immobility, which indicates anti-stress property. MJ also increased the time spent in active swimming and prolonged the latency to exhaustion, which further suggests anti-stress activity. In addition, it also exhibited anti-stress property as evidenced by prolonged latency to first appearance of anoxic convulsions. The results of this study suggest that MJ demonstrated anti-stress activity and may be useful as an energizer in times of body weakness or exhaustion. Although more studies are necessary before concluding on how MJ exerts its anti-stress activity, the present data suggest an action similar to adaptogens in boosting energy and resilience in the face of stress.

  19. Effects of Methyl Jasmonate on Acute Stress Responses in Mice Subjected to Forced Swim and Anoxic Tests

    PubMed Central

    Aluko, Oritoke M.; Umukoro, Solomon; Annafi, Olajide S.; Adewole, Folashade A.; Omorogbe, Osarume

    2015-01-01

    Methyl jasmonate (MJ) is an anti-stress hormone released by plants in response to external stressors and aids adaptation to stress. In this study, we evaluated the anti-stress activity of MJ using the forced swim endurance test (FSET) and anoxic tolerance test in mice. Male Swiss mice were given MJ (25–100 mg/kg, i.p) 30 min before the FSET and anoxic test were carried out. The first occurrence of immobility, duration of immobility, time spent in active swimming, and latency to exhaustion were assessed in the FSET. The onset to anoxic convulsion was measured in the anoxic tolerance test. MJ significantly (p < 0.05) delayed the first occurrence of immobility and shortened the period of immobility, which indicates anti-stress property. MJ also increased the time spent in active swimming and prolonged the latency to exhaustion, which further suggests anti-stress activity. In addition, it also exhibited anti-stress property as evidenced by prolonged latency to first appearance of anoxic convulsions. The results of this study suggest that MJ demonstrated anti-stress activity and may be useful as an energizer in times of body weakness or exhaustion. Although more studies are necessary before concluding on how MJ exerts its anti-stress activity, the present data suggest an action similar to adaptogens in boosting energy and resilience in the face of stress. PMID:26839844

  20. Full-scale demonstration of step feed concept for improving an anaerobic/anoxic/aerobic nutrient removal process.

    PubMed

    Ge, Shijian; Zhu, Yunpeng; Lu, Congcong; Wang, Shuying; Peng, Yongzhen

    2012-09-01

    A small wastewater treatment plant (WWTP) failed to meet effluent requirements of the first-A discharge standard in China, with the anaerobic/anoxic/oxic (A/A/O) process treating municipal and partial industrial wastewater. Thus an A/O step feed process (Anoxic/oxic/anoxic/oxic/anoxic/oxic) with floating plastic carriers in aerobic units was proposed to improve nutrient removal within the existing WWTP. Four main reform strategies were applied: (1) the original influent was divided into three streams which led into corresponding anoxic units; (2) floating plastic carriers were placed in the second and third oxic units; (3) nitrified liquid recycling was omitted; (4) channel shapes and sizes were adjusted between adjacent units to prevent backflow. After these modifications were implemented, the total nitrogen and phosphorus concentrations in the effluent were reduced from 20.8 to 14.2mg/L, and from 1.89 to 0.57 mg/L, respectively. Moreover, annual electricity consumption in the WWTP was reduced by 245 MWh as a result of these modifications.

  1. Diversity of methanogens and sulfate-reducing bacteria in the interfaces of five deep-sea anoxic brines of the Red Sea.

    PubMed

    Guan, Yue; Hikmawan, Tyas; Antunes, André; Ngugi, David; Stingl, Ulrich

    2015-11-01

    Oceanic deep hypersaline anoxic basins (DHABs) are characterized by drastic changes in physico-chemical conditions in the transition from overlaying seawater to brine body. Brine-seawater interfaces (BSIs) of several DHABs across the Mediterranean Sea have been shown to possess methanogenic and sulfate-reducing activities, yet no systematic studies have been conducted to address the potential functional diversity of methanogenic and sulfate-reducing communities in the Red Sea DHABs. Here, we evaluated the relative abundance of Bacteria and Archaea using quantitative PCR and conducted phylogenetic analyses of nearly full-length 16S rRNA genes as well as functional marker genes encoding the alpha subunits of methyl-coenzyme M reductase (mcrA) and dissimilatory sulfite reductase (dsrA). Bacteria predominated over Archaea in most locations, the majority of which were affiliated with Deltaproteobacteria, while Thaumarchaeota were the most prevalent Archaea in all sampled locations. The upper convective layers of Atlantis II Deep, which bear increasingly harsh environmental conditions, were dominated by members of the class Thermoplasmata (Marine Benthic Group E and Mediterranean Sea Brine Lakes Group 1). Our study revealed unique microbial compositions, the presence of niche-specific groups, and collectively, a higher diversity of sulfate-reducing communities compared to methanogenic communities in all five studied locations. Copyright © 2015 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

  2. Multi-proxy study of Ocean Anoxic Event 2 (Cenomanian-Turonian) yields new perspective on the drivers for Mesozoic anoxic events

    NASA Astrophysics Data System (ADS)

    Sageman, B. B.; Hurtgen, M.; Jacobson, A. D.; Selby, D. S.

    2015-12-01

    Mesozoic ocean anoxic events have long been a focus of intense study because they appear to reflect a large-scale oscillation of the marine redox state from oxic to anoxic, and at least locally sulfidic. The consensus view on the cause of these events has changed over the past 39 years, since they were first defined. A global net increase in primary production is now widely accepted as the key driver, and the evidence for a volcanic trigger of this process is strong. However, the exact pathway from volcanism to OAE is less certain. Some authors favor the direct role of a massive load of reduced compounds in LIP hydrothermal fluxes for consuming available marine oxygen. Others prefer the indirect pathway of oxygen consumption by enhanced organic matter flux, which requires a major increase in nutrient budgets. Metallic micronutrients in the hydrothermal fluxes have been hypothesized, as have increases in riverine phosphorus fluxes due to enhanced weathering that would result from volcanic CO2 driven warming. Our recent work on the OAE2 interval has led to some new ideas about these hypothesized drivers. In particular, refinement of the Late Cenomanian time scale, and comparison of the geochemical records of d13C, d34S, Osi, P phases, and d44Ca between selected sections in North America and Europe has suggested the following sequence of events: 1) Osi data indicate that the onset of a major volcanic event precedes the positive shift in C-isotopes by at least 40 to possibly 180 kyr; 2) a positive shift in d44Ca data interpreted to indicate ocean acidification is coincident with the volcanic event; 3) the positive shift in C-isotopes is interpreted to reflect the accumulated burial of marine organic matter sufficient to shift the C-reservoir to heavier values; thus, our data suggest that up to 180 kyr was required for the shift in nutrient supply, productivity increase, and organic matter burial. Two mechanisms that conceivably match the lagged character of the event

  3. Lenticulostriate arterial distribution pathology may underlie pediatric anoxic brain injury in drowning

    PubMed Central

    Ishaque, Mariam; Manning, Janessa H.; Woolsey, Mary D.; Franklin, Crystal G.; Tullis, Elizabeth W.; Fox, Peter T.

    2016-01-01

    Drowning is a leading cause of neurological morbidity and mortality in young children. Anoxic brain injury (ABI) can result from nonfatal drowning and typically entails substantial neurological impairment. The neuropathology of drowning-induced pediatric ABI is not well established. Specifically, quantitative characterization of the spatial extent and tissue distribution of anoxic damage in pediatric nonfatal drowning has not previously been reported but could clarify the underlying pathophysiological processes and inform clinical management. To this end, we used voxel-based morphometric (VBM) analyses to quantify the extent and spatial distribution of consistent, between-subject alterations in gray and white matter volume. Whole-brain, high-resolution T1-weighted MRI datasets were acquired in 11 children with chronic ABI and 11 age- and gender-matched neurotypical controls (4–12 years). Group-wise VBM analyses demonstrated predominantly central subcortical pathology in the ABI group in both gray matter (bilateral basal ganglia nuclei) and white matter (bilateral external and posterior internal capsules) (P < 0.001); minimal damage was found outside of these deep subcortical regions. These highly spatially convergent gray and white matter findings reflect the vascular distribution of perforating lenticulostriate arteries, an end-arterial watershed zone, and suggest that vascular distribution may be a more important determinant of tissue loss than oxygen metabolic rate in pediatric ABI. Further, these results inform future directions for diagnostic and therapeutic modalities. PMID:26937385

  4. Metabolism in anoxic permeable sediments is dominated by eukaryotic dark fermentation

    NASA Astrophysics Data System (ADS)

    Bourke, Michael F.; Marriott, Philip J.; Glud, Ronnie N.; Hasler-Sheetal, Harald; Kamalanathan, Manoj; Beardall, John; Greening, Chris; Cook, Perran L. M.

    2017-01-01

    Permeable sediments are common across continental shelves and are critical contributors to marine biogeochemical cycling. Organic matter in permeable sediments is dominated by microalgae, which as eukaryotes have different anaerobic metabolic pathways to bacteria and archaea. Here we present analyses of flow-through reactor experiments showing that dissolved inorganic carbon is produced predominantly as a result of anaerobic eukaryotic metabolic activity. In our experiments, anaerobic production of dissolved inorganic carbon was consistently accompanied by large dissolved H2 production rates, suggesting the presence of fermentation. The production of both dissolved inorganic carbon and H2 persisted following administration of broad spectrum bactericidal antibiotics, but ceased following treatment with metronidazole. Metronidazole inhibits the ferredoxin/hydrogenase pathway of fermentative eukaryotic H2 production, suggesting that pathway as the source of H2 and dissolved inorganic carbon production. Metabolomic analysis showed large increases in lipid production at the onset of anoxia, consistent with documented pathways of anoxic dark fermentation in microalgae. Cell counts revealed a predominance of microalgae in the sediments. H2 production was observed in dark anoxic cultures of diatoms (Fragilariopsis sp.) and a chlorophyte (Pyramimonas) isolated from the study site, substantiating the hypothesis that microalgae undertake fermentation. We conclude that microalgal dark fermentation could be an important energy-conserving pathway in permeable sediments.

  5. Anoxic bio-electrochemical system for treatment of complex chemical wastewater with simultaneous bioelectricity generation.

    PubMed

    Velvizhi, G; Goud, R Kannaiah; Venkata Mohan, S

    2014-01-01

    Bioelectrochemical treatment system (BET) with anoxic anodic microenvironment was studied with chemical wastewater (CW) in comparison with anoxic treatment (AxT, sequencing batch reactor (SBR)) with same parent anaerobic consortia. BET system documented relatively higher treatment efficiency at higher organic load (5.0 kg COD/m(3)) accounting for COD removal efficiency of (90%) along with nitrate (48%), phosphate (51%), sulphates (68%), colour (63%) and turbidity (90%) removal, compared to AxT operation (COD, 47%; nitrate, 36%; phosphate, 32%; sulphate, 35%; colour, 45% and turbidity, 54%). The self-induced bio-potential developed due to the electrode assembly in BET resulted in effective treatment with simultaneous bioelectricity generation (631 mA/m(2)). AxT operation showed persistent reduction behaviour, while simultaneous redox behaviour was observed with BET indicating balanced electron transfer. BET operation illustrated higher wastewater toxicity reduction compared to the AxT system which documents the variation in bio-electrocatalytic behaviour of same consortia under different microenvironment.

  6. Cross-regulation by CrcZ RNA controls anoxic biofilm formation in Pseudomonas aeruginosa

    PubMed Central

    Pusic, Petra; Tata, Muralidhar; Wolfinger, Michael T.; Sonnleitner, Elisabeth; Häussler, Susanne; Bläsi, Udo

    2016-01-01

    Pseudomonas aeruginosa (PA) can thrive in anaerobic biofilms in the lungs of cystic fibrosis (CF) patients. Here, we show that CrcZ is the most abundant PA14 RNA bound to the global regulator Hfq in anoxic biofilms grown in cystic fibrosis sputum medium. Hfq was crucial for anoxic biofilm formation. This observation complied with an RNAseq based transcriptome analysis and follow up studies that implicated Hfq in regulation of a central step preceding denitrification. CrcZ is known to act as a decoy that sequesters Hfq during relief of carbon catabolite repression, which in turn alleviates Hfq-mediated translational repression of catabolic genes. We therefore inferred that CrcZ indirectly impacts on biofilm formation by competing for Hfq. This hypothesis was supported by the findings that over-production of CrcZ mirrored the biofilm phenotype of the hfq deletion mutant, and that deletion of the crcZ gene augmented biofilm formation. To our knowledge, this is the first example where competition for Hfq by CrcZ cross-regulates an Hfq-dependent physiological process unrelated to carbon metabolism. PMID:28000785

  7. Effect of high nitrate concentration on PHB storage in sequencing batch reactor under anoxic conditions.

    PubMed

    Ciğgin, Asli S; Karahan, Ozlem; Orhon, Derin

    2009-02-01

    The study investigated effect of high influent nitrate concentration on poly-beta-hydroxybutyrate, (PHB), storage in a sequencing batch reactor, (SBR), under anoxic conditions. Acetate was fed as pulse during anoxic phase, sustained with external nitrate feeding. SBR operation involved three runs at steady state with COD/N ratios of 3.84, 2.93 and 1.54 gCOD/gN, where external nitrate concentrations gradually increased from 50 mg N/l to 114 mg N/l and 226 mg N/l, in 1st, 2nd and 3rd runs, respectively. In 1st run, acetate was fully converted into PHB with the storage yield value of 0.57-0.59 gCOD/gCOD, calculated both in terms of PHB formation and NO(X) utilization, confirming storage was the sole substrate utilization mechanism. In the following runs, PHB formation was reduced and the storage yield based on PHB dropped down to 0.40 and 0.33 gCOD/gCOD with increasing influent nitrate concentrations, indicating that higher portions of acetate were diverted to simultaneous direct growth. The observations suggested that nitrite accumulation detected at low COD/N ratios was responsible for inhibition of PHB storage.

  8. Anoxic Oxidation of Arsenite Linked to Denitrification in Sludges and Sediments

    PubMed Central

    Sun, Wenjie; Sierra, Reyes; Field, Jim A.

    2008-01-01

    In this study, denitrification linked to the oxidation of arsenite (As(III)) to arsenate (As(V)) was shown to be a widespread microbial activity in anaerobic sludge and sediment samples that were not previously exposed to arsenic contamination. When incubated with 0.5 mM As(III) and 10 mM NO3−, the anoxic oxidation of As(III) commenced within a few days, achieving specific activities of up to 1.24 mmol As(V) formed g−1 volatile suspended solids d−1 due to growth (doubling times of 0.74 to 1.4 d). The anoxic oxidation of As(III) was partially to completely inhibited by 1.5 and 5 mM As(III), respectively. Inhibition was minimized by adding As(III) adsorbed onto activated aluminum (AA). The oxidation of As(III) was shown to be linked to the complete denitrification of NO3− to N2 by demonstrating a significantly enhanced production of N2 beyond the background endogenous production as a result of adding As(III)-AA to the cultures. The N2 production corresponded closely the expected stoichiometry of the reaction, 2.5 mol As(III) mol−1 N2-N. The oxidation of As(III) linked to the use of common occuring nitrate as an electron acceptor may be an important missing link in the biogeochemical cycling of arsenic. PMID:18762312

  9. Periodic Mid-cretaceous Ocean Anoxic Events Linked By Oscillations of The Phosphorus and Oxygen Cycles

    NASA Astrophysics Data System (ADS)

    Lenton, T.; Handoh, I.

    A series of ocean anoxic events (OAEs) occurred in the mid-Cretaceous warm period (120-80 Ma) that have been linked with high rates of organic carbon burial, warm high- and low- latitude temperatures and sea-level changes. OAEs have been studied individually, but a causal mechanism that connects them has been lacking. We show that peaks in global reactive phosphorus accumulation rate coincide with OAEs 1d, 2 and 3, and exhibit a 6 Myr periodicity over 100-80 Ma. Oxic-anoxic oscillations of 6 Myr period can be triggered in a model of the coupled N, P, C and O2 biogeochemical cycles, by increasing phosphorus weathering rates. The oscillations are sustained by a positive feedback between phosphate concentration, new production and anoxia and a counteracting but slower negative feedback between atmospheric oxygen and anoxia. We suggest that elevated atmospheric CO2 and global warmth driven by increased tectonic and volcanic activity 120-80 Ma, together with the rise of flowering plants 100 Ma, drove increased phosphorus weathering rates and triggered periodic OAEs in the mid-Cretaceous.

  10. Oxidation of dissolved elemental mercury by thiol compounds under anoxic conditions

    SciTech Connect

    Zheng, Wang; Lin, Hui; Mann, Benjamin F; Liang, Liyuan; Gu, Baohua

    2013-01-01

    Mercuric mercury, Hg(II), forms strong complexes with thiol compounds that commonly dominate Hg(II) speciation in natural freshwater. However, reactions between dissolved elemental Hg(0) and thiols are not well understood although these processes are likely to be important in determining Hg speciation and geochemical cycling in the environment. In this study, reaction rates and mechanisms between dissolved Hg(0) and a number of selected organic ligands with varying molecular structures and sulfur (S) oxidation states were determined to assess the role of these ligands in Hg(0) redox transformation. We found that all thiols caused oxidation of Hg(0) under anoxic conditions but, contrary to expectation, compounds with higher S-oxidation states (e.g., disulfide) than thiols exhibited little or no reactivity with Hg(0) at pH 7. The rate and extent of Hg(0) oxidation varied widely, with smaller aliphatic thiols showing the greatest degree of oxidation. The mechanism of the oxidation is attributed to a two-step process involving adsorption of Hg(0) to thiols followed by the charge transfer from Hg(0) to electron acceptors. These observations demonstrate a unique thiol-induced oxidation pathway of dissolved Hg(0), with important implications for the redox transformation, speciation, and bioavailability of Hg for microbial methylation in anoxic environments.

  11. Oxidation of dissolved elemental mercury by thiol compounds under anoxic conditions.

    PubMed

    Zheng, Wang; Lin, Hui; Mann, Benjamin F; Liang, Liyuan; Gu, Baohua

    2013-11-19

    Mercuric ion, Hg(2+), forms strong complexes with thiolate compounds that commonly dominate Hg(II) speciation in natural freshwater. However, reactions between dissolved aqueous elemental mercury (Hg(0)aq) and organic ligands in general, and thiol compounds in particular, are not well studied although these reactions likely affect Hg speciation and cycling in the environment. In this study, we compared the reaction rates between Hg(0)aq and a number of selected organic ligands with varying molecular structures and sulfur (S) oxidation states in dark, anoxic conditions to assess the role of these ligands in Hg(0)aq oxidation. Significant Hg(0)aq oxidation was observed with all thiols but not with ligands containing no S. Compounds with oxidized S (e.g., disulfide) exhibited little or no reactivity toward Hg(0)aq either at pH 7. The rate and extent of Hg(0)aq oxidation varied greatly depending on the chemical and structural properties of thiols, thiol/Hg ratios, and the presence or absence of electron acceptors. Smaller aliphatic thiols and higher thiol/Hg ratios resulted in higher Hg(0)aq oxidation rates than larger aromatic thiols at lower thiol/Hg ratios. The addition of electron acceptors (e.g., humic acid) also led to substantially increased Hg(0)aq oxidation. Our results suggest that thiol-induced oxidation of Hg(0)aq is important under anoxic conditions and can affect Hg redox transformation and bioavailability for microbial methylation.

  12. Perils of categorical thinking: "Oxic/anoxic" conceptual model in environmental remediation

    USGS Publications Warehouse

    Bradley, Paul M.

    2012-01-01

    Given ambient atmospheric oxygen concentrations of about 21 percent (by volume), the lower limit for reliable quantitation of dissolved oxygen concentrations in groundwater samples is in the range of 0.1–0.5 mg/L. Frameworks for assessing in situ redox condition are often applied using a simple two-category (oxic/anoxic) model of oxygen condition. The "oxic" category defines the environmental range in which dissolved oxygen concentrations are clearly expected to impact contaminant biodegradation, either by supporting aerobic biodegradation of electron-donor contaminants like petroleum hydrocarbons or by inhibiting anaerobic biodegradation of electron-acceptor contaminants like chloroethenes. The tendency to label the second category "anoxic" leads to an invalid assumption that oxygen is insignificant when, in fact, the dissolved oxygen concentration is less than detection but otherwise unknown. Expressing dissolved oxygen concentrations as numbers of molecules per volume, dissolved oxygen concentrations that fall below the 0.1 mg/L field detection limit range from 1 to 1017 molecules/L. In light of recent demonstrations of substantial oxygen-linked biodegradation of chloroethene contaminants at dissolved oxygen concentrations well below the 0.1–0.5 mg/L field detection limit, characterizing "less than detection" oxygen concentrations as "insignificant" is invalid.

  13. ATP-sensitive K+ channel activation provides transient protection to the anoxic turtle brain.

    PubMed

    Pék-Scott, M; Lutz, P L

    1998-12-01

    There is wide speculation that ATP-sensitive K+ (KATP) channels serve a protective function in the mammalian brain, being activated during periods of energy failure. The aim of the present study was to determine if KATP channels also have a protective role in the anoxia-tolerant turtle brain. After ouabain administration, rates of change in extracellular K+ were measured in the telencephalon of normoxic and anoxic turtles (Trachemys scripta). The rate of K+ efflux was reduced by 50% within 1 h of anoxia and by 70% at 2 h of anoxia, and no further decrease was seen at 4 h of anoxia. The addition of the KATP channel blocker glibenclamide or 2,3-butanedione monoxime prevented the anoxia-induced decrease in K+ efflux during the first hour of anoxia, but the effect of these blockers was diminished at 2 h of anoxia and was not seen after 4 h of anoxia. This pattern of change in KATP channel blocker sensitivity can be related to a previously established temporary fall and subsequent recovery of tissue ATP during early anoxia. We suggest that activated KATP channels are involved in the downregulation of membrane ion permeability (channel arrest) during the initial energy crisis period but are switched off when the full anoxic state is established and tissue ATP levels have been restored. We also found that, in contrast to those in mammals, KATP channels are not a major route for K+ efflux in the energy-depleted turtle brain.

  14. Na(+)/K(+)-ATPase activity in the anoxic turtle (Trachemys scripta) brain at different acclimation temperature.

    PubMed

    Stecyk, Jonathan A W; Farrell, Anthony P; Vornanen, Matti

    2017-04-01

    Survival of prolonged anoxia requires a balance between cellular ATP demand and anaerobic ATP supply from glycolysis, especially in critical tissues such as the brain. To add insight into the ATP demand of the brain of the anoxia-tolerant red-eared slider turtle (Trachemys scripta) during prolonged periods of anoxic submergence, we quantified and compared the number of Na(+)-K(+)-ATPase units and their molecular activity in brain tissue from turtles acclimated to either 21°C or 5°C and exposed to either normoxia or anoxia (6h 21°C; 14days at 5°C). Na(+)-K(+)-ATPase activity and density per g tissue were similar at 21°C and 5°C in normoxic turtles. Likewise, anoxia exposure at 21°C did not induce any change in Na(+)-K(+)-ATPase activity or density. In contrast, prolonged anoxia at 5°C significantly reduced Na(+)-K(+)-ATPase activity by 55%, which was largely driven by a 50% reduction of the number of Na(+)-K(+)-ATPase units without a change in the activity of existing Na(+)-K(+)-ATPase pumps or α-subunit composition. These findings are consistent with the "channel arrest" hypothesis to reduce turtle brain Na(+)-K(+)-ATPase activity during prolonged, but not short-term anoxia, a change that likely helps them overwinter under low temperature, anoxic conditions. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Microbial diversity of an anoxic zone of a hydroelectric power station reservoir in Brazilian Amazonia.

    PubMed

    Graças, Diego A; Miranda, Paulo R; Baraúna, Rafael A; McCulloch, John A; Ghilardi, Rubens; Schneider, Maria Paula C; Silva, Artur

    2011-11-01

    Microbial diversity was evaluated in an anoxic zone of Tucuruí Hydroelectric Power Station reservoir in Brazilian Amazonia using a culture-independent approach by amplifying and sequencing fragments of the 16S rRNA gene using metagenomic DNA as a template. Samples obtained from the photic, aphotic (40 m) and sediment (60 m) layers were used to construct six 16S rDNA libraries containing a total of 1,152 clones. The sediment, aphotic and photic layers presented 64, 33 and 35 unique archaeal operational taxonomic units (OTUs). The estimated richness of these layers was evaluated to be 153, 106 and 79 archaeal OTUs, respectively, using the abundance-based coverage estimator (ACE) and 114, 83 and 77 OTUs using the Chao1 estimator. For bacterial sequences, 114, 69 and 57 OTUs were found in the sediment, aphotic and photic layers, which presented estimated richnesses of 1,414, 522 and 197 OTUs (ACE) and 1,059, 1,014 and 148 OTUs (Chao1), respectively. Phylogenetic analyses of the sequences obtained revealed a high richness of microorganisms which participate in the carbon cycle, namely, methanogenic archaea and methanotrophic proteobacteria. Most sequences obtained belong to non-culturable prokaryotes. The present study offers the first glimpse of the huge microbial diversity of an anoxic area of a man-made lacustrine environment in the tropics.

  16. Methane production and simultaneous sulphate reduction in anoxic, salt marsh sediments

    USGS Publications Warehouse

    Oremland, R.S.; Marsh, L.M.; Polcin, S.

    1982-01-01

    It has been generally believed that sulphate reduction precludes methane generation during diagenesis of anoxic sediments1,2. Because most biogenic methane formed in nature is thought to derive either from acetate cleavage or by hydrogen reduction of carbon dioxide3-6, the removal of these compounds by the energetically more efficient sulphate-reducing bacteria can impose a substrate limitation on methanogenic bacteria 7-9. However, two known species of methanogens, Methanosarcina barkeri and Methanococcus mazei, can grow on and produce methane from methanol and methylated amines10-13. In addition, these compounds stimulate methane production by bacterial enrichments from the rumen11,14 and aquatic muds13,14. Methanol can enter anaerobic food webs through bacterial degradation of lignins15 or pectin16, and methylated amines can be produced either from decomposition of substances like choline, creatine and betaine13,14 or by bacterial reduction of trimethylamine oxide17, a common metabolite and excretory product of marine animals. However, the relative importance of methanol and methylated amines as precursors of methane in sediments has not been previously examined. We now report that methanol and trimethylamine are important substrates for methanogenic bacteria in salt marsh sediments and that these compounds may account for the bulk of methane produced therein. Furthermore, because these compounds do not stimulate sulphate reduction, methanogenesis and sulphate reduction can operate concurrently in sulphate-containing anoxic sediments. ?? 1982 Nature Publishing Group.

  17. Using biogenic sulfur gases as remotely detectable biosignatures on anoxic planets.

    PubMed

    Domagal-Goldman, Shawn D; Meadows, Victoria S; Claire, Mark W; Kasting, James F

    2011-06-01

    We used one-dimensional photochemical and radiative transfer models to study the potential of organic sulfur compounds (CS(2), OCS, CH(3)SH, CH(3)SCH(3), and CH(3)S(2)CH(3)) to act as remotely detectable biosignatures in anoxic exoplanetary atmospheres. Concentrations of organic sulfur gases were predicted for various biogenic sulfur fluxes into anoxic atmospheres and were found to increase with decreasing UV fluxes. Dimethyl sulfide (CH(3)SCH(3), or DMS) and dimethyl disulfide (CH(3)S(2)CH(3), or DMDS) concentrations could increase to remotely detectable levels, but only in cases of extremely low UV fluxes, which may occur in the habitable zone of an inactive M dwarf. The most detectable feature of organic sulfur gases is an indirect one that results from an increase in ethane (C(2)H(6)) over that which would be predicted based on the planet's methane (CH(4)) concentration. Thus, a characterization mission could detect these organic sulfur gases-and therefore the life that produces them-if it could sufficiently quantify the ethane and methane in the exoplanet's atmosphere.

  18. Denitrifying phosphorus removal in a step-feed CAST with alternating anoxic-oxic operational strategy.

    PubMed

    Ma, Juan; Peng, Yongzhen; Wang, Shuying; Wang, Li; Liu, Yang; Ma, Ningping

    2009-01-01

    A bench-scale cyclic activated sludge technology (CAST) was operated to study the biological phosphorus removal performance and a series of batch tests was carried out to demonstrate the accumulation of denitrifying polyphosphate-accumulating organisms (DNPAOs) in CAST system. Under all operating conditions, step-feed CAST with enough carbon sources in influent had the highest nitrogen and phosphorus removal efficiency as well as good sludge settling performance. The average removal rate of COD, NH4+-N, PO4(3-)-P and total nitrogen (TN) was 88.2%, 98.7%, 97.5% and 92.1%, respectively. The average sludge volume index (SVI) was 133 mL/g. The optimum anaerobic/aerobic/anoxic (AOA) conditions for the cultivation of DNPAOs could be achieved by alternating anoxic/oxic operational strategy, thus a significant denitrifying phosphorus removal occurred in step-feed CAST. The denitrification of NOx(-)-N completed quickly due to step-feed operation and enough carbon sources, which could enhance phosphorus release and further phosphorus uptake capability of the system. Batch tests also proved that polyphosphate-accumulating organisms (PAOs) in the step-feed process had strong denitrifying phosphorus removal capacity. Both nitrate and nitrite could be used as electron acceptors in denitrifying phosphorus removal. Low COD supply with step-feed operation strategy would favor DNPAOs accumulation.

  19. Iron-mediated microbial oxidation and abiotic reduction of organic contaminants under anoxic conditions.

    PubMed

    Tobler, Nicole B; Hofstetter, Thomas B; Straub, Kristina L; Fontana, Daniela; Schwarzenbach, René P

    2007-11-15

    In anoxic environments, the oxidation of organic compounds, such as BTEX fuel components, by dissimilatory Fe(III) reduction can generate reactive mineral-bound Fe(II) species, which in turn are able to reduce other classes of organic and inorganic groundwater contaminants. In this study, we designed and evaluated an anaerobic batch reactor that mimicks iron-reducing conditions to investigate the factors that favor the coupling of microbial toluene oxidation and abiotic reduction of nitroaromatic contaminants. We investigated the influence of different Fe(III)-bearing minerals and combinations thereof on the coupling of these two processes. Results from laboratory model systems show that complete oxidation of toluene to CO2 by Geobacter metallireducens in the presence of Fe(III)-bearing minerals leads to the formation of mineral-bound Fe(II) species capable of the reduction of 4-nitroacetophenone. Whereas significant microbial toluene oxidation was only observed in the presence of amorphous Fe(III) phases, reduction of nitroaromatic compounds only proceeded with Fe(II) species bound to crystalline Fe(III) oxides. Our results suggest that in anoxic soils and sediments containing amorphous and crystalline iron phases simultaneously, coupling of microbial oxidation and abiotic reduction of organic compounds may allow for concurrent natural attenuation of different contaminant classes.

  20. Metabolism in anoxic permeable sediments is dominated by eukaryotic dark fermentation.

    PubMed

    Bourke, Michael F; Marriott, Philip J; Glud, Ronnie N; Hasler-Sheetal, Harald; Kamalanathan, Manoj; Beardall, John; Greening, Chris; Cook, Perran L M

    2017-01-01

    Permeable sediments are common across continental shelves and are critical contributors to marine biogeochemical cycling. Organic matter in permeable sediments is dominated by microalgae, which as eukaryotes have different anaerobic metabolic pathways to prokaryotes such as bacteria and archaea. Here we present analyses of flow-through reactor experiments showing that dissolved inorganic carbon is produced predominantly as a result of anaerobic eukaryotic metabolic activity. In our experiments, anaerobic production of dissolved inorganic carbon was consistently accompanied by large dissolved H2 production rates, suggesting the presence of fermentation. The production of both dissolved inorganic carbon and H2 persisted following administration of broad spectrum bactericidal antibiotics, but ceased following treatment with metronidazole. Metronidazole inhibits the ferredoxin/hydrogenase pathway of fermentative eukaryotic H2 production, suggesting that pathway as the source of H2 and dissolved inorganic carbon production. Metabolomic analysis showed large increases in lipid production at the onset of anoxia, consistent with documented pathways of anoxic dark fermentation in microalgae. Cell counts revealed a predominance of microalgae in the sediments. H2 production was observed in dark anoxic cultures of diatoms (Fragilariopsis sp.) and a chlorophyte (Pyramimonas) isolated from the study site, substantiating the hypothesis that microalgae undertake fermentation. We conclude that microalgal dark fermentation could be an important energy-conserving pathway in permeable sediments.

  1. Anoxic biodegradation of dimethyl phthalate (DMP) by activated sludge cultures under nitrate-reducing conditions.

    PubMed

    Wu, Dong-lei; Hu, Bao-lan; Zheng, Ping; Qaisar, Mahmood

    2007-01-01

    Worldwide extensive use of plasticized plastics has resulted in phthalates pollution in different environment. Nitrates from industry and agriculture are also widely disseminated in the soils, natural waters and wastewaters. Dimethyl phthalate (DMP) biodegradation by activated sludge cultures under nitrate-reducing conditions was investigated. Under one optimized condition, DMP was biodegraded from 102.20 mg/L to undetectable level in 56 h under anoxic conditions and its reaction fitted well with the first-order kinetics. Using the high-performance liquid chromatography (HPLC) and liquid chromatography mass spectrometry (LC-MS) analysis, mono-methyl phthalate (MMP) and phthalic acid (PA) were detected as the major intermediates of DMP biodegradation. When combined with the determination of chemical oxygen demand (COD(Cr)) removal capacity and pH, DMP was found to be mineralized completely under anoxic conditions. The biodegradation pathway was proposed as DMP -->MMP-->PA-->...-->CO2 + H2O. The molar ratio ofDMP to nitrate consumed was found to be 9.0:1, which agrees well with the theoretical stoichiometric values of DMP biodegradation by nitrate-reducing bacteria. The results of the non-linear simulation showed that the optimum pH and temperature for the degradation were 7.56 and 31.4 degrees C, respectively.

  2. Nitrogen isotope evidence for water mass denitrification during the Early Toarcian (Jurassic) oceanic anoxic event

    NASA Astrophysics Data System (ADS)

    Jenkyns, Hugh C.; GröCke, Darren R.; Hesselbo, Stephen P.

    2001-12-01

    Bulk sedimentary nitrogen isotope (δ15Ntot) data have been generated from Lower Jurassic black, carbon-rich shales in the British Isles and northern Italy deposited during the early Toarcian oceanic anoxic event. A pronounced positive δ15Ntot excursion through the exaratum Subzone of the falciferum Zone (defined by characteristic ammonites in the British Isles) broadly correlates with a relative maximum in weight percent total organic carbon and, in some sections, with a negative δ13Corg excursion. Upwelling of a deoxygenated water mass that had undergone partial denitrification is the likely explanation for relative enrichment of δ15Ntot, and parallels may be drawn with Quaternary sediments of the Arabian Sea, Gulf of California, and northwest Mexican margin. The development of Early Toarcian suboxic water masses and consequent partial denitrification is attributed to increases in organic productivity. Approximately coincident phenomena include the following: a relative climatic optimum, realignment of major oceanic current systems, and a possible release of methane gas hydrates from continental margin sediments early in the history of the oceanic anoxic event.

  3. The impact of feed composition on biodegradation of benzoate under cyclic (aerobic/anoxic) conditions.

    PubMed

    Cinar, Ozer

    2004-02-09

    The response of a mixed microbial culture to different feed compositions, that is, containing benzoate and pyruvate as sole carbon sources at different levels, was studied in a chemostat with a 48-h hydraulic residence time under cyclic aerobic and anoxic (denitrifying) conditions. The cyclic bacterial culture was well adapted to different feed compositions as evidenced by the lack of accumulation of benzoate or pyruvate in the chemostat. Both the benzoate-degrading capabilities and the in vitro catechol 2,3-dioxygenase (C23DO) activities of the cyclic bacterial cultures were in direct proportion to the flux through the chemostat of the substrate degraded by the pathway containing C23DO, with some exceptions. The quantity of C23DO showed a transient decrease during the initial portion of the aerobic period before returning to the level present during the anoxic period. That decrease was most likely caused by the production of H(2)O(2) by the cells upon being returned to aerobic conditions.

  4. Metabolism in anoxic permeable sediments is dominated by eukaryotic dark fermentation

    PubMed Central

    Bourke, Michael F; Marriott, Philip J.; Glud, Ronnie N.; Hasler-Sheetal, Harald; Kamalanathan, Manoj; Beardall, John; Greening, Chris; Cook, Perran L.M.

    2016-01-01

    Permeable sediments are common across continental shelves and are critical contributors to marine biogeochemical cycling. Organic matter in permeable sediments is dominated by microalgae, which as eukaryotes have different anaerobic metabolic pathways to prokaryotes such as bacteria and archaea. Here we present analyses of flow-through reactor experiments showing that dissolved inorganic carbon is produced predominantly as a result of anaerobic eukaryotic metabolic activity. In our experiments, anaerobic production of dissolved inorganic carbon was consistently accompanied by large dissolved H2 production rates, suggesting the presence of fermentation. The production of both dissolved inorganic carbon and H2 persisted following administration of broad spectrum bactericidal antibiotics, but ceased following treatment with metronidazole. Metronidazole inhibits the ferredoxin/hydrogenase pathway of fermentative eukaryotic H2 production, suggesting that pathway as the source of H2 and dissolved inorganic carbon production. Metabolomic analysis showed large increases in lipid production at the onset of anoxia, consistent with documented pathways of anoxic dark fermentation in microalgae. Cell counts revealed a predominance of microalgae in the sediments. H2 production was observed in dark anoxic cultures of diatoms (Fragilariopsis sp.) and a chlorophyte (Pyramimonas) isolated from the study site, substantiating the hypothesis that microalgae undertake fermentation. We conclude that microalgal dark fermentation could be an important energy-conserving pathway in permeable sediments. PMID:28070216

  5. The utility of median somatosensory evoked potentials in anoxic-ischemic coma.

    PubMed

    Rothstein, Ted L

    2009-01-01

    The early recognition of comatose patients with a hopeless prognosis--regardless of how aggressively they are managed--is of utmost importance. Median somatosensory evoked potentials (SSEP) supplement and enhance neurological examination findings in anoxic-ischemic coma and are useful as an early guide in predicting outcome. The key finding is that bilateral absence of cortical evoked potentials reliably predicts unfavorable outcome in comatose patients after cardiac arrest. The author studied 50 comatose patients with preserved brainstem function after cardiac arrest. All 23 patients with bilateral absence of cortical evoked potentials died without awakening. Neuropathological study in seven patients disclosed widespread ischemic changes or frank cortical laminar necrosis. The remaining 27 patients with normal or delayed central conduction times had an uncertain prognosis because some died without awakening or entered a persistent vegetative state. The majority of patients with normal central conduction times had a good outcome, whereas a delay in central conduction times increased the likelihood of neurological deficit or death. Greater use of SSEP in anoxic-ischemic coma would identify those patients unlikely to recover and would avoid costly medical care that is to no avail.

  6. Methanogenic archaea are globally ubiquitous in aerated soils and become active under wet anoxic conditions

    PubMed Central

    Angel, Roey; Claus, Peter; Conrad, Ralf

    2012-01-01

    The prototypical representatives of the Euryarchaeota—the methanogens—are oxygen sensitive and are thought to occur only in highly reduced, anoxic environments. However, we found methanogens of the genera Methanosarcina and Methanocella to be present in many types of upland soils (including dryland soils) sampled globally. These methanogens could be readily activated by incubating the soils as slurry under anoxic conditions, as seen by rapid methane production within a few weeks, without any additional carbon source. Analysis of the archaeal 16S ribosomal RNA gene community profile in the incubated samples through terminal restriction fragment length polymorphism and quantification through quantitative PCR indicated dominance of Methanosarcina, whose gene copy numbers also correlated with methane production rates. Analysis of the δ13C of the methane further supported this, as the dominant methanogenic pathway was in most cases aceticlastic, which Methanocella cannot perform. Sequences of the key methanogenic enzyme methyl coenzyme M reductase retrieved from the soil samples before incubation confirmed that Methanosarcina and Methanocella are the dominant methanogens, though some sequences of Methanobrevibacter and Methanobacterium were also detected. The global occurrence of only two active methanogenic archaea supports the hypothesis that these are autochthonous members of the upland soil biome and are well adapted to their environment. PMID:22071343

  7. High-Resolution Dynamics of Microbial Communities during Dissimilatory Selenate Reduction in Anoxic Soil.

    PubMed

    Navarro, Ronald R; Aoyagi, Tomo; Kimura, Makoto; Itoh, Hideomi; Sato, Yuya; Kikuchi, Yoshitomo; Ogata, Atsushi; Hori, Tomoyuki

    2015-07-07

    Selenate is one of the most common toxic metal compounds in contaminated soils. Its redox status can be changed by microbial activity, thus affecting its water solubility and soil mobility. However, current knowledge of microbial dynamics has been limited by the low sensitivity of past isolation and identification protocols. Here, high-throughput Illumina sequencing of 16S rRNA genes was applied to monitor the shift of the microorganisms in an anoxic contaminated soil after Se(VI) and acetate amendment. An autoclaved soil with both chemicals and a live soil with acetate alone were used as controls. Preliminary chemical analysis clearly showed the occurrence of biological selenate reduction coupled with acetate oxidation. Principal coordinate analysis and diversity indices of Illumina-derived sequence data showed dynamic succession and diversification of the microbial community in response to selenate reduction. High-resolution phylogenetic analysis revealed that the relative frequency of an operational taxonomic unit (OTU) from the genus Dechloromonas increased remarkably from 0.2% to 36% as a result of Se(VI) addition. Multiple OTUs representing less abundant microorganisms from the Rhodocyclaceae and Comamonadaceae families had significant increases as well. This study demonstrated that these microorganisms are concertedly involved in selenate reduction of the employed contaminated soil under anoxic conditions.

  8. Evolutionary and geologic consequences of organic carbon fixing in the primitive anoxic ocean

    NASA Astrophysics Data System (ADS)

    Berry, W. B. N.; Wilde, P.

    1983-03-01

    Steps leading to development of the modern photic-based marine food web are postulated as the result of modifications of the environment, enhanced by the activity of Archean sulfur chemoautotrophs. Such organisms (Anoxium) evolved in an anoxic ocean prior to 3.9 × 109 yr ago at Archean analogs of modern oceanic hydrothermal vents. At this time geothermal energy was more readily available to organisms than photic energy, given atmospheric conditions at the surface similar to Venus, where intensity is low and only middle and red visible wavelengths penetrate the cloudy CO2-rich atmosphere. Competition for the reduced sulfur developed due to oxidation and loss of sulfur to sediments. Consequently, evolutionary advantage shifted to Anoxium isolates that could use alternate energy sources such as light to supplement the diminished supplies of reduced sulfur. Initially, photo-sulfur organisms evolved similar to modern purple bacteria that absorb in the red visible spectra. Subsequent carbon fixing and oxidation improved both the quantity and range of light reaching the ocean surface. This permitted absorption in the blue visible range so that water splitting was now feasible, releasing free oxygen and accelerating oxidation. Eventually, reducing environments became restricted, completing the shift in the principal marine carbon-fixing activity from anoxic chemoautotrophic to aerobic photosynthetic organisms.

  9. Cross-regulation by CrcZ RNA controls anoxic biofilm formation in Pseudomonas aeruginosa

    NASA Astrophysics Data System (ADS)

    Pusic, Petra; Tata, Muralidhar; Wolfinger, Michael T.; Sonnleitner, Elisabeth; Häussler, Susanne; Bläsi, Udo

    2016-12-01

    Pseudomonas aeruginosa (PA) can thrive in anaerobic biofilms in the lungs of cystic fibrosis (CF) patients. Here, we show that CrcZ is the most abundant PA14 RNA bound to the global regulator Hfq in anoxic biofilms grown in cystic fibrosis sputum medium. Hfq was crucial for anoxic biofilm formation. This observation complied with an RNAseq based transcriptome analysis and follow up studies that implicated Hfq in regulation of a central step preceding denitrification. CrcZ is known to act as a decoy that sequesters Hfq during relief of carbon catabolite repression, which in turn alleviates Hfq-mediated translational repression of catabolic genes. We therefore inferred that CrcZ indirectly impacts on biofilm formation by competing for Hfq. This hypothesis was supported by the findings that over-production of CrcZ mirrored the biofilm phenotype of the hfq deletion mutant, and that deletion of the crcZ gene augmented biofilm formation. To our knowledge, this is the first example where competition for Hfq by CrcZ cross-regulates an Hfq-dependent physiological process unrelated to carbon metabolism.

  10. Microbial community in anoxic-oxic-settling-anaerobic sludge reduction process revealed by 454 pyrosequencing analysis.

    PubMed

    Ning, Xinqiang; Qiao, Wenwen; Zhang, Lei; Gao, Xu

    2014-12-01

    Modification of the anoxic-oxic (AO) process by inserting a sludge holding tank (SHT) into the sludge return line forms an anoxic-oxic-settling-anaerobic (A+OSA) process that can achieve a 48.98% sludge reduction rate. The 454 pyrosequencing method was used to obtain the microbial communities of the AO and A+OSA processes. Results showed that the microbial community structures of the 2 processes were different as a result of the SHT insertion. Bacteria assigned to the phyla Proteobacteria and Bacteroidetes commonly existed and dominated the microbial populations of the 2 processes. However, the relative abundance of these populations shifted in the presence of SHT. The relative abundance of Proteobacteria decreased during the A+OSA process. A specific comparison at the class level showed that Sphingobacteria was enriched in the A+OSA process. The result suggested that the fermentative bacteria Sphingobacteria may have key functions in reducing the sludge from the A+OSA process. Uncultured Nitrosomonadaceae gradually became the dominant ammonia-oxidizing bacteria, and the nitrite-oxidizing bacterium Nitrospira was enriched in the A+OSA process. Both occurrences were favorable for stabilized nitrogen removal. The known denitrifying species in the A+OSA process were similar to those in the AO process; however, their relative abundance also decreased.

  11. Lenticulostriate arterial distribution pathology may underlie pediatric anoxic brain injury in drowning.

    PubMed

    Ishaque, Mariam; Manning, Janessa H; Woolsey, Mary D; Franklin, Crystal G; Tullis, Elizabeth W; Fox, Peter T

    2016-01-01

    Drowning is a leading cause of neurological morbidity and mortality in young children. Anoxic brain injury (ABI) can result from nonfatal drowning and typically entails substantial neurological impairment. The neuropathology of drowning-induced pediatric ABI is not well established. Specifically, quantitative characterization of the spatial extent and tissue distribution of anoxic damage in pediatric nonfatal drowning has not previously been reported but could clarify the underlying pathophysiological processes and inform clinical management. To this end, we used voxel-based morphometric (VBM) analyses to quantify the extent and spatial distribution of consistent, between-subject alterations in gray and white matter volume. Whole-brain, high-resolution T1-weighted MRI datasets were acquired in 11 children with chronic ABI and 11 age- and gender-matched neurotypical controls (4-12 years). Group-wise VBM analyses demonstrated predominantly central subcortical pathology in the ABI group in both gray matter (bilateral basal ganglia nuclei) and white matter (bilateral external and posterior internal capsules) (P < 0.001); minimal damage was found outside of these deep subcortical regions. These highly spatially convergent gray and white matter findings reflect the vascular distribution of perforating lenticulostriate arteries, an end-arterial watershed zone, and suggest that vascular distribution may be a more important determinant of tissue loss than oxygen metabolic rate in pediatric ABI. Further, these results inform future directions for diagnostic and therapeutic modalities.

  12. Constraining the rate of oceanic deoxygenation leading up to a Cretaceous Oceanic Anoxic Event (OAE-2: ~94 Ma)

    PubMed Central

    Ostrander, Chadlin M.; Owens, Jeremy D.; Nielsen, Sune G.

    2017-01-01

    The rates of marine deoxygenation leading to Cretaceous Oceanic Anoxic Events are poorly recognized and constrained. If increases in primary productivity are the primary driver of these episodes, progressive oxygen loss from global waters should predate enhanced carbon burial in underlying sediments—the diagnostic Oceanic Anoxic Event relic. Thallium isotope analysis of organic-rich black shales from Demerara Rise across Oceanic Anoxic Event 2 reveals evidence of expanded sediment-water interface deoxygenation ~43 ± 11 thousand years before the globally recognized carbon cycle perturbation. This evidence for rapid oxygen loss leading to an extreme ancient climatic event has timely implications for the modern ocean, which is already experiencing large-scale deoxygenation. PMID:28808684

  13. Constraining the rate of oceanic deoxygenation leading up to a Cretaceous Oceanic Anoxic Event (OAE-2: ~94 Ma).

    PubMed

    Ostrander, Chadlin M; Owens, Jeremy D; Nielsen, Sune G

    2017-08-01

    The rates of marine deoxygenation leading to Cretaceous Oceanic Anoxic Events are poorly recognized and constrained. If increases in primary productivity are the primary driver of these episodes, progressive oxygen loss from global waters should predate enhanced carbon burial in underlying sediments-the diagnostic Oceanic Anoxic Event relic. Thallium isotope analysis of organic-rich black shales from Demerara Rise across Oceanic Anoxic Event 2 reveals evidence of expanded sediment-water interface deoxygenation ~43 ± 11 thousand years before the globally recognized carbon cycle perturbation. This evidence for rapid oxygen loss leading to an extreme ancient climatic event has timely implications for the modern ocean, which is already experiencing large-scale deoxygenation.

  14. Consequences of artificial deepwater ventilation in the Bornholm Basin for oxygen conditions, cod reproduction and benthic biomass - a model study

    NASA Astrophysics Data System (ADS)

    Stigebrandt, A.; Rosenberg, R.; Råman Vinnå, L.; Ödalen, M.

    2014-07-01

    We develop and use a circulation model to estimate hydrographical and ecological changes in the isolated basin water of the Bornholm Basin. By pumping well oxygenated so-called winter water, residing beneath the level of the summer thermocline, to the greatest depth of the basin, where it is forced to mix with the resident water, the rate of density reduction should increase and thereby the frequency of intrusions of new oxygen-rich deepwater. We show that pumping 1000 m3 s-1 should increase the rates of water exchange and oxygen supply by 2.5 and 3 times, respectively. The CRV (Cod Reproduction Volume), the volume of water in the isolated basin meeting the requirements for successful cod reproduction (S > 11, O2 > 2 mL L-1), should every year be greater than 54 km3, which is an immense improvement since it in certain years is currently much less. Anoxic bottoms should no longer occur in the basin and hypoxic events will become rare. This should permit extensive colonization of fauna on the earlier periodically anoxic bottoms. Increased biomass of benthic fauna should also mean increased food supply to economically valuable demersal fish like cod and flatfish. In addition, the bioturbation activity and re-oxygenation of the sediments should lead to increased phosphorus retention by the sediments.

  15. Why Oceanic Anoxic Events Terminated? Data and Speculations About the end of OAE1a.

    NASA Astrophysics Data System (ADS)

    Erba, E.

    2006-12-01

    After three decades of research on oceanic anoxic events (OAEs), an impressive amount of geo-data has generated models that try to explain the peculiar mid Cretaceous ocean/atmosphere system. Plausible causes of oceanic anoxia have been identified and somehow substantiated with geological data. Refined and improved chronology has allowed the dating of events that perhaps accidentally concurred to trigger and maintain oceanic anoxia for long time intervals. Based on the original definition, OAEs are intervals of abnormal primary productivity in surface seawaters and oxygen-depletion in bottom seawaters. There is a general consensus on the role of carbon dioxide increases, and implicit tectonic-igneous events, triggering a major climate change, responses of marine biota and restructuring of chemical and physical characteristics of the ocean. An improved understanding of processes at the onset and during OAEs has been achieved, but less attention has been paid to the termination of anoxia. The early Aptian OAE 1a is an extreme and long lasting perturbation of the Cretaceous. It is associated with geochemical anomalies and fundamental changes in marine and terrestrial ecosystems. The end of OAE1a was characterized in pelagic sections, allowing the identification, dating and quantification of paleonvironmental changes. Specifically, nannofossil assemblages were quantified to estimate biogenic calcite production and fluxes, and reconstruct the evolution of calcareous phytoplankton, relative to changes in planktonic communities and in the ocean/atmosphere composition. The restoration of oxygenated bottom waters correlates with a renewal of nannoplankton calcification and a short- lived but distinctive cooling episode. The end of anoxia appears to be abrupt and unambiguously anticipates the long-lasting C isotopic positive excursion that is detached from organic carbon-rich black shales in pelagic sequences. The sharp re-oxygenation might imply a major external cause and

  16. Transport, anoxia and energy control on anaerobic respiration and methanogenesis in anoxic peat soils

    NASA Astrophysics Data System (ADS)

    Bonaiuti, Simona; Blodau, Christian; Knorr, Klaus-Holger

    2017-04-01

    In deep and permanently water saturated peat deposits, extremely low diffusive transport and concomitant build-up of metabolic end-products, i.e of dissolved inorganic carbon (DIC) and methane (CH4), have been found to slow-down anaerobic respiration and methanogenesis. Such accumulation of DIC and CH4 lowers the Gibbs free energy yield of terminal respiration and methanogenesis, which can inhibit the course of anaerobic metabolic processes. In particular, this affects terminal steps of the breakdown of organic carbon (C), such as methanogenesis, acetogenesis and fermentation processes, which occur near thermodynamic minimum energy thresholds. This effect is thus of critical importance for the long-term C sequestration, as the slow-down of decomposition ultimately regulates the long-term fate of C in deep peat deposits. The exact controls of this observed slow-down of organic matter mineralization are not yet fully understood. Moreover, altered patterns of water or gas transport due to predicted changes in climate may affect these controls in peat soils. Therefore, the aim of this study was to investigate how burial of peat leads to an inactivation of anaerobic decomposition and to investigate the effects of advective water transport and persistently anoxic conditions on anaerobic decomposition, temporal evolution of thermodynamic energy yields to methanogenesis and methanogenic pathways. To this end, we conducted a column experiment with homogenized, ombrotrophic peat over a period of 300 days at 20˚ C. We tested i) a control treatment under diffusive transport only, ii) an advective flow treatment with a flow of 10 mm d-1, and iv) an anoxic treatment to evaluate changes in decomposition in absence of oxygen in the unsaturated zone of the cores. A slow-down of anaerobic respiration and methanogenesis generally set in at larger depths after 150 days at CH4 concentrations of 0.6-0.9 mmol L-1 and DIC concentrations of 6-12 mmol L-1. This effect occurred at higher

  17. Oxygen as Intermediate in Anoxic Environments: Nitrite-Dependent Methane Oxidation and Beyond

    NASA Astrophysics Data System (ADS)

    Ettwig, K. F.

    2014-12-01

    In recent years the known diversity of hydrocarbon activation mechanisms under anaerobic conditions has been extended by intra-aerobic denitrification, a process in which oxygen is derived from NO and used for substrate activation. For two phylogenetically unrelated bacterial species, the freshwater NC10 phylum bacterium Methylomirabilis oxyfera [1] and the marine γ-proteobacterial strain HdN1 [2] it has been shown that, under anoxic conditions with nitrate and/or nitrite, mono-oxygenases are used for methane and hexadecane oxidation, respectively. No degradation was observed with nitrous oxide (N2O) only. In the anaerobic methanotroph M. oxyfera, which lacks apparent nitrous oxide reductase in its genome, substrate activation in the presence of nitrite was directly associated with both O2 and N2 formation. These findings strongly argue for the role of nitric oxide (NO), or an oxygen species derived from it, in the activation reaction of methane. Although intracellular oxygen generation has been experimentally documented and elegantly explains the utilization of 'aerobic' pathways under anoxic conditions, research about the underlying molecular mechanism has just started. The proposed candidate enzymes for oxygen (or possibly another another reactive intermediate) production from NO, an NO dismutase (NOD) [3], related to quinol-dependent NO reductases (qNORs), is present and highly expressed in both M. oxyfera and strain HdN1. Besides that, several recently sequenced species from the Cytophaga-Flavobacterium-Bacteroides group harbor Nod/Nor genes, but experimential evidence is needed to show if these have NOD activity, are unusual but functional qNORs, or represent transition states between the two. Additionally, for several anaerobic hydrocarbon-degrading organisms the biochemical mechanism of substrate activation has not been elucidated yet: whereas signature genes of anaerobic degradation are missing, monooxygenase genes are present. Also these microorganisms

  18. Metabolic Strategies in Energy-Limited Microbial Communities in the Anoxic Subsurface (Frasassi Cave System, Italy)

    NASA Astrophysics Data System (ADS)

    McCauley, R. L.; Jones, D. S.; Schaperdoth, I.; Steinberg, L.; Macalady, J. L.

    2010-12-01

    Two major sources of energy, light and chemical potential, are available to microorganisms. However, energy is not always abundant and is often a limiting factor in microbial survival and replication. The anoxic, terrestrial subsurface offers a unique opportunity to study microorganisms and their potentially novel metabolic strategies that are relevant for understanding biogeochemistry and biosignatures as related to the non-photosynthetic, energy-limited environments on the modern and ancient Earth and elsewhere in the solar system. Geochemical data collected in a remote stratified lake 600 m below ground surface in the sulfidic Frasassi cave system (Italy) suggest that little redox energy is available for life, consistent with low signal from domain-specific FISH probes. The carbon isotope signatures of biofilms (-33‰) and DIC (-9‰) in the anoxic water suggest in situ production by lithoautotrophs using RuBisCO. 16S rDNA libraries constructed from the biofilm are dominated by diverse sulfate reducing bacteria. The remaining bacterial and archaeal clones affiliate with more than 11 major uncultivated or novel prokaryotic lineages. Diverse dsrAB gene sequences are consistent with high sulfate concentrations and undetectable or extremely low oxygen, nitrate, and iron concentrations. However, the electron donor for sulfate reduction is unclear. Methane is detectable in the anoxic water although no 16S rDNA sequences associated with known methanogens or anaerobic methane oxidizers were retrieved. mcrA gene sequences retrieved from the biofilm by cloning are not related to cultivated methanogens or to known anaerobic methane oxidizers. Non-purgable organic carbon (NPOC) is below detection limits (i.e. <42 μM acetate) suggesting that alternative electron donors or novel metabolisms may be important. A sample collected by cave divers in October 2009 was pyrosequenced at the Pennsylvania State University Genomics Core Facility using Titanium chemistry (454 Life

  19. Anoxic metabolism and biochemical production in Pseudomonas putida F1 driven by a bioelectrochemical system.

    PubMed

    Lai, Bin; Yu, Shiqin; Bernhardt, Paul V; Rabaey, Korneel; Virdis, Bernardino; Krömer, Jens O

    2016-01-01

    Pseudomonas putida is a promising host for the bioproduction of chemicals, but its industrial applications are significantly limited by its obligate aerobic character. The aim of this paper is to empower the anoxic metabolism of wild-type Pseudomonas putida to enable bioproduction anaerobically, with the redox power from a bioelectrochemical system (BES). The obligate aerobe Pseudomonas putida F1 was able to survive and produce almost exclusively 2-Keto-gluconate from glucose under anoxic conditions due to redox balancing with electron mediators in a BES. 2-Keto-gluconate, a precursor for industrial anti-oxidant production, was produced at an overall carbon yield of over 90 % based on glucose. Seven different mediator compounds were tested, and only those with redox potential above 0.207 V (vs standard hydrogen electrode) showed interaction with the cells. The productivity increased with the increasing redox potential of the mediator, indicating this was a key factor affecting the anoxic production process. P. putida cells survived under anaerobic conditions, and limited biofilm formation could be observed on the anode's surface. Analysis of the intracellular pools of ATP, ADP and AMP showed that cells had an increased adenylate energy charge suggesting that cells were able to generate energy using the anode as terminal electron acceptor. The analysis of NAD(H) and NADP(H) showed that in the presence of specific extracellular electron acceptors, the NADP(H) pool was more oxidised, while the NAD(H) pool was unchanged. This implies a growth limitation under anaerobic conditions due to a shortage of NADPH and provides a way to limit biomass formation, while allowing cell maintenance and catalysis at high purity and yield. For the first time, this study proved the principle that a BES-driven bioconversion of glucose can be achieved for a wild-type obligate aerobe. This non-growth bioconversion was in high yields, high purity and also could deliver the necessary

  20. Availability of free oxygen in deep bottom water of some Archean-Early Paleoproterozoic ocean basins as derived from iron formation facies analyses

    NASA Astrophysics Data System (ADS)

    Beukes, N. J.; Smith, A.

    2013-12-01

    Archean to Early Paleoproterozoic ocean basins are commonly, although not exclusively, depicted as rather static systems; either permanently stratified with shallow mixed oxygenated water overlying anoxic deep water or with a totally anoxic water column. The anoxic water columns are considered enriched in dissolved ferrous iron derived from hydrothermal plume activity. These sourced deposition of iron formations through precipitation of mainly ferrihydrite via reaction with free oxygen in the stratified model or anaerobic iron oxidizing photoautotrophs in the anoxic model. However, both these models face a simple basic problem if detailed facies reconstructions of deepwater microbanded iron formations (MIFs) are considered. In such MIFs it is common that the deepest water and most distal facies is hematite rich followed shoreward by magnetite, iron silicate and siderite facies iron formation. Examples of such facies relations are known from jaspilitic iron formation of the ~3,2 Ga Fig Tree Group (Barberton Mountainland), ~ 2,95 Ga iron formations of the Witwatersrand-Mozaan basin and the ~2,5 Ga Kuruman Iron Formation, Transvaal Supergroup, South Africa. Facies relations of these MIFs with associated siliciclastics or carbonates also indicate that the upper water columns of the basins, down to below wave base, were depleted in iron favoring anoxic-oxic stratification rather than total anoxia. In the MIFs it can be shown that hematite in the distal facies represents the earliest formed diagenetic mineral; most likely crystallized from primary ferrihydrite. The problem is one of how ferrihydrite could have been preserved on the ocean floor if it was in direct contact with reducing ferrous deep bottom water. Rather dissolved ferrous iron would have reacted with ferrihydrite to form diagenetic magnetite. This dilemma is resolved if in the area of deepwater hematite MIF deposition, the anoxic ferrous iron enriched plume was detached from the basin floor due to buoyancy

  1. Characterization of phosphorus in sinking particles in Cariaco Basin, Venezuela

    NASA Astrophysics Data System (ADS)

    Ranhofer, M. L.; Benitez-Nelson, C.; Thunell, R.

    2004-12-01

    Phosphorus (P) is an essential nutrient utilized by all organisms for biological productivity, yet little is known about its cycling within the marine realm. In this study, we used a five-step sequential sediment extraction method (SEDEX) to examine the composition of P in sinking particles obtained from one of the world's largest anoxic basins, Cariaco Basin, Venezuela. This method, which is usually applied to sediments, chemically separates particulate P into 5 phases: loosely bound or exchangeable (PEx), iron-bound (PFe), authigenic (PAut), detrital (PDet), and organic (POrg). Samples were collected from November 2000 to April 2002 using four automated sediment traps moored at depths of 275, 455, 930 and 1250 m, with the 275 m trap located just above the oxic/anoxic interface. Our results indicate that the composition of particulate P changes dramatically as the material sinks through the water column. The 275 m trap was comprised of a mixture of PEx (57 %), POrg (23 %) and PFe (15 %), whereas the deepest trap was dominated by POrg (55 %) and PEx (26 %). Total P fluxes decreased by a factor of four between 275 and 1250 m (85.7 versus 18.5 \\mu mol m-2 d-1), with much of this decrease due to the > 75 % loss of PEx (49.2 to 4.9 \\mu mol m-2 d-1) and PFe (12.6 to 1.8 \\mu mol m-2 d-1). POrg decreased by only 50 % between these two depths (19.9 versus 10.2 \\mu mol m-2 d-1). Our results are consistent with the expectation that PEx is the most labile fraction of P and PFe is rapidly reduced in the anoxic bottom waters of Cariaco Basin. PEx correlates well with organic C (COrg) only in samples from the shallowest trap (r2 = 0.6), while in the deeper traps there is a strong correlation with terrigenous material (r2 = 0.6). This implies a change in the major source, and hence lability of this material as it sinks to the sea floor. POrg was very well correlated to COrg at all depths (r2 > 0.9), implying little to no preferential remineralization below 275 m. Additional

  2. Assessing the Record of Anoxic/Dysoxic Events in Lower Aptian Cupido/La Peña Formations, Northeastern Mexico

    NASA Astrophysics Data System (ADS)

    Maurrasse, F. J.; Barragan-Manzo, R.; Ponton, C.

    2008-05-01

    Lower Aptian series at the la Huasteca Canyon, Nuevo Leon, NE Mexico, include the uppermost part of the Cupido Formation, a shallow-platform facies (TIC > 60%) succeeded by the La Peña Formation (TIC very variable 17 - 92 %). The change indicated a long-term shift in sedimentation characterized by distinct periodic increase in terrigenous, organic matter and abundant occurrence of ammonites. The interbeds of marls, calcareous shales, marly calcilutites and calcirudites of the La Peña facies contain abundant thin-shelled ammonites, and few planktonic foraminifera. The change occurred in the Dufrenoya justinae ammonite Zone, coeval with the Dufrenoya furcata Zone of the standard ammonite biochronostratigraphy of the Mediterranean province for the uppermost Early Aptian (Barragan-Manzo and Mendez-Franco, 2005; Barragan and Maurrasse, 2008). These zones differentiate the upper part of the Lower Aptian, therefore posterior to OAE1a. Nonetheless, while microfacies of the La Peña Fm show also intermittent belemnites, small pelecypods other than rudists, and sea urchins, benthic foraminifera are mostly absent occurring toward younger levels in the Gargasian coincident with highest taxonomic diversity. Benthic foraminifers are conspicuously absent particularly at the levels closest to the transition zone with the infrajacent Cupido facies. Also, despite increase in TOC (up to 2.6 %) in the La Peña facies, ∂13 Corg curve shows little co-variation with increasing OM, which we interpret to represent a regional phenomenon related to super-productivity in the isolated sub-basin of the Mexican platform (Maurrasse et al., 2006). In contrast, typical Cupido Fm microfacies exhibit abundant miliolids (20-30 %), fragments of rudists, echinoids, ostracods (> 30-40%), very few thin ammonite shell debris, and oolites at intermittent levels. Rich benthic foraminifer assemblages are indicative of well-oxygenated bottom conditions. However, there are three horizons about 60 cm

  3. Reduction of Biological Sludge Production Applying an Alternating Oxic/anoxic Process in Water Line.

    PubMed

    Eusebi, Anna Laura; Panigutti, Maximiliano; Battistoni, Paolo

    2016-06-01

    Alternating oxic/anoxic process, applied for the main objective of the improvement of nitrogen performances, was studied in terms of secondary effect of biomass reduction. The process was carried out in one real water resource recovery facility and the data were compared with the previous conventional period when a conventional process was adopted. The main mechanism of the process for the sludge minimization is recognized in the metabolic uncoupling. In fact, an increase of the specific oxygen uptake rate in the biological reactor was recorded stimulated by the change of the oxidation reduction potential environment. Moreover, the heterotrophic growth yield was measured equal to 0.385 kgVSS/kgCOD. The global percentage of reduction was tested with the mass balance of solids. The process is able to decrease the observed sludge yield up to 20%. The specific energy consumption was evaluated.

  4. Mid-Cretaceous carbon cycle perturbations and Oceanic Anoxic Events recorded in southern Tibet

    PubMed Central

    Zhang, Xiaolin; Chen, Kefan; Hu, Dongping; Sha, Jingeng

    2016-01-01

    The organic carbon isotope (δ13Corg) curve for ~1.7-km-thick mid-Cretaceous strata of the Chaqiela section in Gamba area, southern Tibet is presented in this study. C-isotopic chemostratigraphic correlation combined with biostratigraphic constraints show that the Chaqiela section spans early Aptian through early Campanian period, and that almost all of the carbon cycle perturbations and Oceanic Anoxic Events during the mid-Cretaceous period are well recorded in the continental margin area of the southeastern Tethys Ocean. Significantly, two levels of methane-derived authigenic carbonates were identified at the onset of OAE1b near the Aptian-Albian boundary. We suggest that an increase in methane release from gas hydrates, potentially driven by sea-level fall and bottom water temperature increase, may have contributed to the large negative δ13Corg excursions and global warming during OAE1b. PMID:28000797

  5. Optimization of the activated sludge anoxic reactor configuration as a means to control nutrient removal kinetically.

    PubMed

    Plósz, Benedek Gy

    2007-04-01

    Factors influencing the determination of optimum reactor configuration for activated sludge denitrification are investigated in this paper. A kinetic optimization method is presented to evaluate optimal pre- and post-denitrification bioreactor stages. Applying the method developed, simulation studies were carried out to investigate the impacts of the ratio of the influent readily biodegradable and slowly biodegradable substrates and the oxygen entering the denitrification zones on the optimal anoxic reactor configuration. In addition, the paper describes the effects of the slowly biodegradable substrate on the denitrification efficiency using external substrate dosing, and it demonstrates kinetic considerations concerning the hydrolysis process. It has been shown that as a function of the biodegradable substrate composition, the stage system design with three optimized reactor compartments can effectively increase reaction rates in the denitrification zones, and can provide flexibility for varying operation conditions.

  6. Mid-Cretaceous carbon cycle perturbations and Oceanic Anoxic Events recorded in southern Tibet.

    PubMed

    Zhang, Xiaolin; Chen, Kefan; Hu, Dongping; Sha, Jingeng

    2016-12-21

    The organic carbon isotope (δ(13)Corg) curve for ~1.7-km-thick mid-Cretaceous strata of the Chaqiela section in Gamba area, southern Tibet is presented in this study. C-isotopic chemostratigraphic correlation combined with biostratigraphic constraints show that the Chaqiela section spans early Aptian through early Campanian period, and that almost all of the carbon cycle perturbations and Oceanic Anoxic Events during the mid-Cretaceous period are well recorded in the continental margin area of the southeastern Tethys Ocean. Significantly, two levels of methane-derived authigenic carbonates were identified at the onset of OAE1b near the Aptian-Albian boundary. We suggest that an increase in methane release from gas hydrates, potentially driven by sea-level fall and bottom water temperature increase, may have contributed to the large negative δ(13)Corg excursions and global warming during OAE1b.

  7. Mid-Cretaceous carbon cycle perturbations and Oceanic Anoxic Events recorded in southern Tibet

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaolin; Chen, Kefan; Hu, Dongping; Sha, Jingeng

    2016-12-01

    The organic carbon isotope (δ13Corg) curve for ~1.7-km-thick mid-Cretaceous strata of the Chaqiela section in Gamba area, southern Tibet is presented in this study. C-isotopic chemostratigraphic correlation combined with biostratigraphic constraints show that the Chaqiela section spans early Aptian through early Campanian period, and that almost all of the carbon cycle perturbations and Oceanic Anoxic Events during the mid-Cretaceous period are well recorded in the continental margin area of the southeastern Tethys Ocean. Significantly, two levels of methane-derived authigenic carbonates were identified at the onset of OAE1b near the Aptian-Albian boundary. We suggest that an increase in methane release from gas hydrates, potentially driven by sea-level fall and bottom water temperature increase, may have contributed to the large negative δ13Corg excursions and global warming during OAE1b.

  8. The carbon isotope biogeochemistry of methane production in anoxic sediments. 1: Field observations

    NASA Technical Reports Server (NTRS)

    Blair, Neal E.; Boehme, Susan E.; Carter, W. Dale, Jr.

    1993-01-01

    The natural abundance C-13/C-12 ratio of methane from anoxic marine and freshwater sediments in temperate climates varies seasonally. Carbon isotopic measurements of the methanogenic precursors, acetate and dissolved inorganic carbon, from the marine sediments of Cape Lookout Bight, North Carolina were used to determine the sources of the seasonal variations at that site. Movement of the methanogenic zone over an isotopic gradient within the dissolved CO2 pool appears to be the dominant control of the methane C-13/C-12 ratio from February to June. The onset of acetoclastic methane-production is a second important controlling process during mid-summer. An apparent temperature dependence on the fractionation factor for CO2-reduction may have a significant influence on the isotopic composition of methane throughout the year.

  9. Methane production from bicarbonate and acetate in an anoxic marine sediment

    NASA Technical Reports Server (NTRS)

    Crill, P. M.; Martens, C. S.

    1986-01-01

    Methane production from C-14 labeled bicarbonate and acetate was measured over the top 28 cm of anoxic Cape Lookout Bight sediments during the summer of 1983. The depth distribution and magnitude of summed radioisotopically determined rates compare well with previous measurements of total methane production and the sediment-water methane flux. Methane production from CO2 reduction and acetate fermentation accounts for greater than 80 percent of the total production rate and sediment-water flux. Methane production from bicarbonate was found to occur in all depth intervals sampled except those in the top 2 cm, whereas significant methane production from acetate only occurred at depths below 10 cm where sulfate was exhausted. Acetate provided 20 to 29 percent of the measured methane production integrated over the top 30 cm of the sediments.

  10. Genomic potential for nitrogen assimilation in uncultivated members of Prochlorococcus from an anoxic marine zone

    PubMed Central

    Astorga-Eló, Marcia; Ramírez-Flandes, Salvador; DeLong, Edward F; Ulloa, Osvaldo

    2015-01-01

    Cyanobacteria of the genus Prochlorococcus are the most abundant photosynthetic marine organisms and key factors in the global carbon cycle. The understanding of their distribution and ecological importance in oligotrophic tropical and subtropical waters, and their differentiation into distinct ecotypes, is based on genetic and physiological information from several isolates. Currently, all available Prochlorococcus genomes show their incapacity for nitrate utilization. However, environmental sequence data suggest that some uncultivated lineages may have acquired this capacity. Here we report that uncultivated low-light-adapted Prochlorococcus from the nutrient-rich, low-light, anoxic marine zone (AMZ) of the eastern tropical South Pacific have the genetic potential for nitrate uptake and assimilation. All genes involved in this trait were found syntenic with those present in marine Synechococcus. Genomic and phylogenetic analyses also suggest that these genes have not been aquired recently, but perhaps were retained from a common ancestor, highlighting the basal characteristics of the AMZ lineages within Prochlorococcus. PMID:25700337

  11. Calcareous Nannoplankton Response to Surface-Water Acidification Around Oceanic Anoxic Event 1a

    NASA Astrophysics Data System (ADS)

    Erba, Elisabetta; Bottini, Cinzia; Weissert, Helmut J.; Keller, Christina E.

    2010-07-01

    Ocean acidification induced by atmospheric CO2 may be a major threat to marine ecosystems, particularly to calcareous nannoplankton. We show that, during the Aptian (~120 million years ago) Oceanic Anoxic Event 1a, which resulted from a massive addition of volcanic CO2, the morphological features of calcareous nannofossils traced the biological response to acidified surface waters. We observe the demise of heavily calcified nannoconids and reduced calcite paleofluxes at the beginning of a pre-anoxia calcification crisis. Ephemeral coccolith dwarfism and malformation represent species-specific adjustments to survive lower pH, whereas later, abundance peaks indicate intermittent alkalinity recovery. Deepwater acidification occurred with a delay of 25,000 to 30,000 years. After the dissolution climax, nannoplankton and carbonate recovery developed over ~160,000 years under persisting global dysoxia-anoxia.

  12. Rogoznica Lake (Croatia), a unique anoxic seawater system on the Adriatic coast under the anthropogenic pressures

    NASA Astrophysics Data System (ADS)

    Ciglenečki, Irena; Bura-Nakić, Elvira; Marguš, Marija; Čanković, Milan; Carić, Marina; Viličić, Damir; Ljubešić, Zrinka; Kršinić, Frano; Batistić, Mirna; Janeković, Ivica; Plavčić, Filip

    2014-05-01

    Rogoznica Lake is a typical example of euxinic saline lake, situated on the eastern Adriatic coast (43o32'N 15o58'E). It is a karstic depression filled with seawater, with an area of 10276 m2 and a maximum depth of 15m The lake has circular shape and is surrounded with sheer, karstic cliffs (4-23 m high), which completely protect the lake from the influence of the wind. During the year the lake is thermally, densely and chemically stratified into oxic and anoxic layers. The surface water is well oxygenated, while hypoxia/anoxia occurs in the bottom layer. The mixolimnion varies seasonally and it is greatly influenced by meteorological conditions (temperature, wind, rainfall) which also influence the water layer mixing. Vertical mixing usually occurs during autumn/winter when cold, oxygen-rich water from the surface sinks downwards. Depending on the intensity of the mixing process anoxic conditions in the entire water column could appear. At the boundary oxia-anoxia usually a pinky colored chemocline layer, cca 50 cm thick develops. Anoxic deep water is characterized by high concentrations of reduced sulfur compounds (RSS up to 1mM, mainly in the form of sulfide), and nutrients (NH4+, up to 150 μM; PO43-, up to 22 μM; SiO44-, up to 400 μM) as well as dissolved organic carbon (DOC up to 6 mg l-1) indicating the pronounced remineralization of allochthonous organic matter produced in the surface water The eutrophication of the lake is strongly influenced by nutrient recycling under anaerobic conditions. Due to the extreme ecological conditions which prevail in this lake, phyto- and zooplankton populations are represented by a relatively small number of species, some of them, however, in the populations denser than those in the surrounding sea. After the period of total anoxia appearance, the number of species and their abundance are significantly reduced in comparison with the pre-anoxia values. Diatoms were found to be the dominant microphytoplankton group while

  13. Methane production from bicarbonate and acetate in an anoxic marine sediment

    NASA Technical Reports Server (NTRS)

    Crill, P. M.; Martens, C. S.

    1986-01-01

    Methane production from C-14 labeled bicarbonate and acetate was measured over the top 28 cm of anoxic Cape Lookout Bight sediments during the summer of 1983. The depth distribution and magnitude of summed radioisotopically determined rates compare well with previous measurements of total methane production and the sediment-water methane flux. Methane production from CO2 reduction and acetate fermentation accounts for greater than 80 percent of the total production rate and sediment-water flux. Methane production from bicarbonate was found to occur in all depth intervals sampled except those in the top 2 cm, whereas significant methane production from acetate only occurred at depths below 10 cm where sulfate was exhausted. Acetate provided 20 to 29 percent of the measured methane production integrated over the top 30 cm of the sediments.

  14. Characteristics of Biological Nitrogen Removal in a Multiple Anoxic and Aerobic Biological Nutrient Removal Process

    PubMed Central

    Wang, Huoqing; Guan, Yuntao; Li, Li; Wu, Guangxue

    2015-01-01

    Two sequencing batch reactors, one with the conventional anoxic and aerobic (AO) process and the other with the multiple AO process, were operated to examine characteristics of biological nitrogen removal, especially of the multiple AO process. The long-term operation showed that the total nitrogen removal percentage of the multiple AO reactor was 38.7% higher than that of the AO reactor. In the multiple AO reactor, at the initial SBR cycle stage, due to the occurrence of simultaneous nitrification and denitrification, no nitrite and/or nitrate were accumulated. In the multiple AO reactor, activities of nitrite oxidizing bacteria were inhibited due to the multiple AO operating mode applied, resulting in the partial nitrification. Denitrifiers in the multiple AO reactor mainly utilized internal organic carbon for denitrification, and their activities were lower than those of denitrifiers in the AO reactor utilizing external organic carbon. PMID:26491676

  15. Genomic potential for nitrogen assimilation in uncultivated members of Prochlorococcus from an anoxic marine zone.

    PubMed

    Astorga-Eló, Marcia; Ramírez-Flandes, Salvador; DeLong, Edward F; Ulloa, Osvaldo

    2015-05-01

    Cyanobacteria of the genus Prochlorococcus are the most abundant photosynthetic marine organisms and key factors in the global carbon cycle. The understanding of their distribution and ecological importance in oligotrophic tropical and subtropical waters, and their differentiation into distinct ecotypes, is based on genetic and physiological information from several isolates. Currently, all available Prochlorococcus genomes show their incapacity for nitrate utilization. However, environmental sequence data suggest that some uncultivated lineages may have acquired this capacity. Here we report that uncultivated low-light-adapted Prochlorococcus from the nutrient-rich, low-light, anoxic marine zone (AMZ) of the eastern tropical South Pacific have the genetic potential for nitrate uptake and assimilation. All genes involved in this trait were found syntenic with those present in marine Synechococcus. Genomic and phylogenetic analyses also suggest that these genes have not been aquired recently, but perhaps were retained from a common ancestor, highlighting the basal characteristics of the AMZ lineages within Prochlorococcus.

  16. Photocatalytic decomposition of humic acids in anoxic aqueous solutions producing hydrogen, oxygen and light hydrocarbons.

    PubMed

    Klauson, Deniss; Budarnaja, Olga; Beltran, Ignacio Castellanos; Krichevskaya, Marina; Preis, Sergei

    2014-01-01

    Photocatalytic water splitting for hydrogen and oxygen production requires sacrificial electron donors, for example, organic compounds. Titanium dioxide catalysts doped with platinum, cobalt, tungsten, copper and iron were experimentally tested for the production of hydrogen, oxygen and low molecular weight hydrocarbons from aqueous solutions of humic substances (HS). Platinum-doped catalyst showed the best results in hydrogen generation, also producing methane, ethene and ethane, whereas the best oxygen production was exhibited by P25, followed by copper--and cobalt-containing photocatalysts. Iron-containing photocatalyst produced carbon monoxide as a major product. HS undergoing anoxic photocatalytic degradation produce hydrogen with minor hydrocarbons, and/or oxygen. It appears that better hydrogen yield is achieved when direct HS splitting takes place, as opposed to HS acting as electron donors for water splitting.

  17. Superparamagnetic Fe3O4 particles formed by oxidation of pyrite heated in an anoxic atmosphere

    USGS Publications Warehouse

    Thorpe, A.N.; Senftle, F.E.; Talley, R.; Hetherington, S.; Dulong, F.

    1990-01-01

    As a follow-up to previous gas analysis experiments in which pyrite was heated to 681 K in an anoxic (oxygen starved) atmosphere, the first oxidation product, FeSO4, was studied as a bulk material. No decomposition of FeSO4 to Fe3O4 was observed in the temperature range studied. The lack of decomposition of bulk FeSO4 to Fe3O4 suggests that FeS2 oxidizes directly to Fe3O4, or that FeSO4, FeS2 and O2 react together to form Fe3O4. Magnetic susceptibility and magnetization measurements, along with magnetic hysteresis curves, show that small particles of Fe3O4 form on the pyrite surface, rather than a continuous layer of bulk Fe3O4. A working model describing the oxidation steps is presented. ?? 1990.

  18. Reduction of selenite and selenate on anoxically corroded iron and the synergistic effect of uranyl reduction

    NASA Astrophysics Data System (ADS)

    Puranen, Anders; Jonsson, Mats; Dähn, Rainer; Cui, Daqing

    2010-11-01

    In this work the uptake of dissolved selenium in the form of selenite and selenate on iron covered by a magnetite corrosion layer and the effect of dissolved uranyl on this process is studied. Under simulated anoxic groundwater conditions (bicarbonate and chloride solutions) no immobilization of selenate was found in the absence of uranyl whereas selenite was immobilized, albeit slowly. When uranyl was present, it was found to become reduced and greatly enhanced the rate of reductive immobilization of the dissolved selenite as well as selenate. The increased rate of immobilization is proposed to be due to the oxidative transformation of the passifying magnetite layer as the uranyl is reduced with the observed formation of a transient mixed Fe(II)/Fe(III) oxyhydroxide phase. The iron oxide, and selenium speciation on the surfaces were investigated by Raman spectroscopy. X-ray Absorption Spectroscopy was used to determine the oxidation state of the selenium and uranium on the surfaces.

  19. Evaluation of different packing media for anoxic H2S control in biogas.

    PubMed

    Soreanu, Gabriela; Béland, Michel; Falletta, Patricia; Ventresca, Bert; Seto, Peter

    2009-11-01

    This paper presents the experimental results obtained during the operation of two biotrickling filters packed with 6.7 L of commercially available plastic fibres and lava rocks, respectively. The biotrickling filters were tested under similar operating conditions for hydrogen sulphide (H2S) removal from biogas under anoxic conditions, in order to determine the influence of biogas flow rate and H2S concentration on the process performance and to facilitate process modelling. The biogas flow rate was adjusted to between 25 and 75 L/h, while the input H2S concentration was varied between 500 and 1500 ppmv. The process performance was evaluated by two simultaneous system responses, namely the H2S removal efficiency and H2S loading rate, which were subsequently described by a second-order empirical model and an interaction model, respectively. Good agreement between the experimental results, model prediction and simultaneous dual-response simulation was obtained.

  20. From clinical judgment to odds: a history of prognostication in anoxic-ischemic coma.

    PubMed

    Wijdicks, Eelco F M

    2012-08-01

    Persistent coma from a major anoxic-ischemic injury to the brain may indicate there is less chance for full recovery. The tools of prognostication to assess comatose survivors of cardiopulmonary resuscitation have developed over several decades. Physicians would initially base their judgment on experience and data on outcome in these patients in the early years were merely on awakening not on disability. In the late 1970s, a large multicenter prospective study was performed on outcome in nontraumatic coma. The impetus for this study was the result of Plum and Jennet's collaboration. In 1981--for the first time--complex statistics were used to improve the accuracy of prognosis and became known as the "Levy algorithms." These early seminal studies shaped the prediction models and implied that clinical information alone could assist physicians in making a prediction. Later, probabilistic methods became more commonplace. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  1. Coming back to oneself: a case of anoxic brain damage from a phenomenological perspective.

    PubMed

    Fürst, Elisabeth L'orange

    2015-03-01

    Struck by a cardiac arrest that lasted 3/4 of an hour, a 53-year-old man suddenly collapsed one day at work. The result was a serious anoxic brain damage that developed into dementia. This essay presents the process of 'coming back to himself' while it questions what this concept might imply. The descriptions and analyses rest upon an ethnographic study of his life, at hospitals and then at home, assisted by his wife, who is also the author of this article. Theoretically, the analysis depends on Merleau-Ponty's phenomenology of perception and is also based on the therapeutic use of music in treating people with dementia championed by Oliver Sachs. It is argued that the field of medicine has much to learn from the anthropological method of long-term observation, as well as theories of embodiment that see the body as simultaneously being an object and a subject.

  2. Anoxic carbon flux in photosynthetic microbial mats as revealed by metatranscriptomics.

    PubMed

    Burow, Luke C; Woebken, Dagmar; Marshall, Ian P G; Lindquist, Erika A; Bebout, Brad M; Prufert-Bebout, Leslie; Hoehler, Tori M; Tringe, Susannah G; Pett-Ridge, Jennifer; Weber, Peter K; Spormann, Alfred M; Singer, Steven W

    2013-04-01

    Photosynthetic microbial mats possess extraordinary phylogenetic and functional diversity that makes linking specific pathways with individual microbial populations a daunting task. Close metabolic and spatial relationships between Cyanobacteria and Chloroflexi have previously been observed in diverse microbial mats. Here, we report that an expressed metabolic pathway for the anoxic catabolism of photosynthate involving Cyanobacteria and Chloroflexi in microbial mats can be reconstructed through metatranscriptomic sequencing of mats collected at Elkhorn Slough, Monterey Bay, CA, USA. In this reconstruction, Microcoleus spp., the most abundant cyanobacterial group in the mats, ferment photosynthate to organic acids, CO2 and H2 through multiple pathways, and an uncultivated lineage of the Chloroflexi take up these organic acids to store carbon as polyhydroxyalkanoates. The metabolic reconstruction is consistent with metabolite measurements and single cell microbial imaging with fluorescence in situ hybridization and NanoSIMS.

  3. Anoxic photochemical oxidation of siderite generates molecular hydrogen and iron oxides

    PubMed Central

    Kim, J. Dongun; Yee, Nathan; Nanda, Vikas; Falkowski, Paul G.

    2013-01-01

    Photochemical reactions of minerals are underappreciated processes that can make or break chemical bonds. We report the photooxidation of siderite (FeCO3) by UV radiation to produce hydrogen gas and iron oxides via a two-photon reaction. The calculated quantum yield for the reaction suggests photooxidation of siderite would have been a significant source of molecular hydrogen for the first half of Earth’s history. Further, experimental results indicate this abiotic, photochemical process may have led to the formation of iron oxides under anoxic conditions. The reaction would have continued through the Archean to at least the early phases of the Great Oxidation Event, and provided a mechanism for oxidizing the atmosphere through the loss of hydrogen to space, while simultaneously providing a key reductant for microbial metabolism. We propose that the photochemistry of Earth-abundant minerals with wide band gaps would have potentially played a critical role in shaping the biogeochemical evolution of early Earth. PMID:23733945

  4. Microbial pathways for the mobilization of mercury as Hg(O) in anoxic subsurface environments

    SciTech Connect

    Barkay, Tamar

    2005-06-01

    The goal of our project which was initiated in June 2005 is focused on the presence of merA in microbial communities of anoxic environments and the effect of anaerobic respiratory pathways on MR expression and activities. The following progress has been made to date: PCR primers were designed to span the known phylogenetic range of merA genes of Gram-negative bacteria. In control experiments, these primers successfully amplified a 288 bp region at the 3? end of previously characterized merA genes from Shewanella putrefaciens pMERPH, Acidithiobacillus ferrooxidans, Pseudomonas stutzeri pPB, Tn5041, Pseudomonas sp. K-62, and Serratia marcescens pDU1358.

  5. pH-dependent degradation of p-nitrophenol by sulfidated nanoscale zerovalent iron under aerobic or anoxic conditions.

    PubMed

    Tang, Jing; Tang, Lin; Feng, Haopeng; Zeng, Guangming; Dong, Haoran; Zhang, Chang; Huang, Binbin; Deng, Yaocheng; Wang, Jiajia; Zhou, Yaoyu

    2016-12-15

    Sulfidated nanoscale zerovalent iron (S-NZVI) is attracting considerable attention due to its easy production and high reactivity to pollutants. We studied the reactivity of optimized S-NZVI (Fe/S molar ratio 6.9), comparing with pristine nanoscale zerovalent iron (NZVI), at various pH solutions (6.77-9.11) towards p-nitrophenol (PNP) under aerobic and anoxic conditions. Studies showed that the optimized extent of sulfidation could utterly enhance PNP degradation compared to NZVI. Batch experiments indicated that in anoxic S-NZVI systems the degradation rate constant increased with increasing pH up to 7.60, and then declined. However, in aerobic S-NZVI, and in anoxic or aerobic NZVI systems, it decreased as pH increased. It was manifested that anoxic S-NZVI systems preferred to weaker alkaline solutions, whereas aerobic S-NZVI systems performed better in acidic solutions. The highest TOC removal efficiency of PNP (17.59%) was achieved in the aerobic S-NZVI system at pH 6.77, revealing that oxygen improved the degradation of PNP by excessive amounts of hydroxyl radicals in slightly acidic conditions, and the TOC removal efficiency was supposed to be further improved in moderate acidic solutions. Acetic acid, a nontoxic ring opening by-product, confirms that the S-NZVI system could be a promising process for industrial wastewater containing sulfide ions.

  6. Simultaneous nitrification/denitrification and trace organic contaminant (TrOC) removal by an anoxic-aerobic membrane bioreactor (MBR).

    PubMed

    Phan, Hop V; Hai, Faisal I; Kang, Jinguo; Dam, Hoa K; Zhang, Ren; Price, William E; Broeckmann, Andreas; Nghiem, Long D

    2014-08-01

    Simultaneous nitrification/denitrification and trace organic contaminant (TrOC) removal during wastewater treatment by an integrated anoxic-aerobic MBR was examined. A set of 30 compounds was selected to represent TrOCs that occur ubiquitously in domestic wastewater. The system achieved over 95% total organic carbon (TOC) and over 80% total nitrogen (TN) removal. In addition, 21 of the 30 TrOCs investigated here were removed by over 90%. Low oxidation reduction potential (i.e., anoxic/anaerobic) regimes were conducive to moderate to high (50% to 90%) removal of nine TrOCs. These included four pharmaceuticals and personal care products (primidone, metronidazole, triclosan, and amitriptyline), one steroid hormone (17β-estradiol-17-acetate), one industrial chemical (4-tert-octylphenol) and all three selected UV filters (benzophenone, oxybenzone, and octocrylene). Internal recirculation between the anoxic and aerobic bioreactors was essential for anoxic removal of remaining TrOCs. A major role of the aerobic MBR for TOC, TN, and TrOC removal was observed.

  7. Simultaneous organic carbon and nitrogen removal in an anoxic-oxic activated sludge system under various operating conditions.

    PubMed

    Rasool, Kashif; Ahn, Dae Hee; Lee, Dae Sung

    2014-06-01

    This study investigated a bench-scale anoxic-oxic activated sludge system for integrated removal of COD and nitrogen. The experimental unit includes four chambers and continuous feeding in first chamber without recycle of nitrified liquid from aerobic to anoxic chamber unlike the conventional anoxic-oxic process. Recycled excessive sludge was used for the purpose of recycling nitrified mixed liquor. Synthetic wastewater with average loading rates of 0.53 kg COD/m(3)/d and 0.067 kg NH4(+)-N/m(3)/d was fed to the reactor system at hydraulic residence times (HRT) of 24 and 18 h. The results of 100 days operation showed high removal efficiencies of organic matter of about 97% as total COD and more than 99% removal of ammonia-nitrogen. In anoxic-oxic operation phase, total inorganic nitrogen (TIN) removal was about 66% by pre-denitrification. Moreover, the solid liquid separation through final clarifier was excellent without any suspended solid in the effluent.

  8. Treatment of phenolics, aromatic hydrocarbons, and cyanide-bearing wastewater in individual and combined anaerobic, aerobic, and anoxic bioreactors.

    PubMed

    Sharma, Naresh K; Philip, Ligy

    2015-01-01

    Studies were conducted on a mixture of pollutants commonly found in coke oven wastewater (CWW) to evaluate the biodegradation of various pollutants under anaerobic, aerobic, and anoxic conditions. The removal of the pollutants was monitored during individual bioreactor operation and using a combination of bioreactors operating in anaerobic-aerobic-anoxic sequence. While studying the performance of individual reactors, it was observed that cyanide removal (83.3 %) was predominant in the aerobic bioreactor, while much of the chemical oxygen demand (COD) (69 %) was consumed in the anoxic bioreactor. With the addition of cyanide, the COD removal efficiency was affected in all the bioreactors, and several intermediates were detected. While treating synthetic CWW using the combined bioreactor system, the overall COD removal efficiency was 86.79 % at an OLR of 2.4 g COD/L/day and an HRT of 96 h. The removal efficiency of 3,5-xylenol and cyanide, with inlet concentration of 150 and 10 mg/L, was found to be 91.8 and 93.6 % respectively. It was found that the impact of xylenol on the performance of the bioreactors was less than cyanide toxicity. Molecular analysis using T-RFLP revealed the dominance of strictly aerobic, mesophilic proteobacterium, Bosea minatitlanensis, in the aerobic bioreactor. The anoxic bioreactor was dominant with Rhodococcus pyridinivorans, known for its remarkable aromatic decomposing activity, while an unclassified Myxococcales bacterium was identified as the predominant bacterial species in the anaerobic bioreactor.

  9. Application of nitrate to enhance biodegradation of gasoline components in soil by indigenous microorganisms under anoxic condition.

    PubMed

    Yang, Su-Cai; Song, Yun; Wang, Dong; Wei, Wen-Xia; Yang, Yan; Men, Bin; Li, Jia-Bin

    2016-01-01

    Anaerobic/anoxic biodegradation of hydrocarbons offers an attractive approach to the removal of these compounds from polluted environments such as aquifers, aquatic sediments, submerged soils and subsurface soils. The application of nitrate was investigated to accelerate the degradation of gasoline components such as mono-aromatic hydrocarbons and total petroleum hydrocarbons (TPH) in soil by indigenous microorganisms under anoxic condition. The addition of nitrate had little effect on the degradation of mono-aromatic hydrocarbons m- & p-xylene, o-xylene, sec-butylbenzene and 1,2,4-trimethylbenzene, but facilitated the degradation of TPH (C6-C12) and mono-aromatic hydrocarbons toluene and ethylbenzene markedly. Furthermore, the more nitrate added, the higher the percentage of toluene, ethylbenzene and TPH (C6-C12) degraded after 180 days of anoxic incubation. Microorganisms capable of degrading toluene, ethylbenzene and TPH (C6-C12) with nitrate as the electron acceptor under anaerobic/anoxic condition are composed predominantly of Alpha-, Beta-, Gamma- or Delta-proteobacteria. Beta- and Gamma-proteobacteria were the main components of indigenous microorganisms, and accounted for 83-100% of the total amount of indigenous microorganisms in soil used in this study. Furthermore, the total amount of indigenous microorganisms increased with nitrate added. The addition of nitrate stimulated the growth of indigenous microorganisms, and therefore facilitated the degradation of toluene, ethylbenzene and TPH (C6-C12).

  10. Transport and removal of viruses in saturated sand columns under oxic and anoxic conditions--Potential implications for groundwater protection.

    PubMed

    Frohnert, Anne; Apelt, Susann; Klitzke, Sondra; Chorus, Ingrid; Szewzyk, Regine; Selinka, Hans-Christoph

    2014-11-01

    To protect groundwater as a drinking water resource from microbiological contamination, protection zones are installed. While travelling through these zones, concentrations of potential pathogens should decline to levels that pose no risks to human health. Removal of viruses during subsurface passage is influenced by physicochemical conditions, such as oxygen concentration, which also affects virus survival. The aim of our study was to evaluate the effect of redox conditions on the removal of viruses during sand filtration. Experiments in glass columns filled with medium-grained sand were conducted to investigate virus removal in the presence and absence of dissolved oxygen. Bacteriophages MS2 and PhiX174, as surrogates for human enteric viruses were spiked in pulsed or in continuous mode and pumped through the columns at a filter velocity of about 1m/d. Virus breakthrough curves were analyzed by calculating total viral elimination and fitted using one-dimensional transport models (CXTFIT and HYDRUS-1D). While short-term experiments with pulsed virus application showed only small differences with regard to virus removal under oxic and anoxic conditions, a long-term experiment with continuous dosing revealed a clearly lower elimination of viruses under anoxic conditions. These findings suggest that less inactivation and less adsorption of viruses in anoxic environments affect their removal. Therefore, in risk assessment studies aimed to secure drinking water resources from viral contamination and optimization of protection zones, the oxic and anoxic conditions in the subsurface should also be considered.

  11. Nitrate-dependent iron oxidation limits iron transport in anoxic ocean regions

    NASA Astrophysics Data System (ADS)

    Scholz, Florian; Löscher, Carolin R.; Fiskal, Annika; Sommer, Stefan; Hensen, Christian; Lomnitz, Ulrike; Wuttig, Kathrin; Göttlicher, Jörg; Kossel, Elke; Steininger, Ralph; Canfield, Donald E.

    2016-11-01

    Iron is an essential element for life on Earth and limits primary production in large parts of the ocean. Oxygen-free continental margin sediments represent an important source of bioavailable iron to the ocean, yet little of the iron released from the seabed reaches the productive sea surface. Even in the anoxic water of oxygen minimum zones, where iron solubility should be enhanced, most of the iron is rapidly re-precipitated. To constrain the mechanism(s) of iron removal in anoxic ocean regions we explored the sediment and water in the oxygen minimum zone off Peru. During our sampling campaign the water column featured two distinct redox boundaries separating oxic from nitrate-reducing (i.e., nitrogenous) water and nitrogenous from weakly sulfidic water. The sulfidic water mass in contact with the shelf sediment contained elevated iron concentrations >300 nM. At the boundary between sulfidic and nitrogenous conditions, iron concentrations dropped sharply to <20 nM coincident with a maximum in particulate iron concentration. Within the iron gradient, we found an increased expression of the key functional marker gene for nitrate reduction (narG). Part of this upregulation was related to the activity of known iron-oxidizing bacteria. Collectively, our data suggest that iron oxidation and removal is induced by nitrate-reducing microbes, either enzymatically through anaerobic iron oxidation or by providing nitrite for an abiotic reaction. Given the important role that iron plays in nitrogen fixation, photosynthesis and respiration, nitrate-dependent iron oxidation likely represents a key-link between the marine biogeochemical cycles of nitrogen, oxygen and carbon.

  12. Uranium and plutonium in anoxic marine sediments of the Santiago River mouth (Eastern Pacific, Mexico).

    PubMed

    Almazán-Torres, María Guadalupe; Ordóñez-Regil, Eduardo; Ruiz-Fernández, Ana Carolina

    2016-11-01

    The uranium (U) and plutonium (Pu) content with depth in a sediment core collected in the continental shelf off the mouth of the Santiago River in the Mexican Pacific was studied to evaluate the contamination effects of the effluent of the Santiago-Lerma River as it moves into the sea. The large mass of terrestrial detritus delivered by the river influences the physicochemical and geochemical processes in the seafloor. Abnormal concentrations of U and Pu in sediments were examined as indicative of the effects of anoxic conditions. One of the indicators of pollution of seawater is the bacterial activity of the shallow seabed layer; and among the prevailing bacteria, the magnetotactic ones induce the formation of euhedral and framboidal shapes (pyrite). These pyrite entities are by-products of anoxic environments loaded with decomposing detrital material and are very abundant in the surface layers of the sediment core analyzed. The pyrite formation is the result of a biochemical reaction between iron and organic sulphur reduced by bacteria, and the pyrite entities precipitate to the seafloor. In the same upper zone of the profile, (238)U is readily immobilized, while (234)U is oxidized and dissolved in seawater by the effect of hot atom chemistry. This may cause the activity ratio (AR) (234)U/(238)U disequilibrium (near 0.41). Furthermore, in the shallow layer of the sediment core, an abnormally high concentration of (239+240)Pu was detected. In this upper layer, the activity concentrations found were 3.19 Bq kg(-1) for (238)U, 1.32 kg(-1) for (234)U and 2.78 Bq kg(-1) for (239+240)Pu. In the lower fractions of the sediment core, normal values of AR (234)U/(238)U (≈1) were found, with traces of (239+240)Pu.

  13. Temporal and spatial distribution of hypoxic/seasonal anoxic zone in Amvrakikos Gulf, Western Greece

    NASA Astrophysics Data System (ADS)

    Kountoura, K.; Zacharias, I.

    2011-08-01

    Coastal hypoxia and anoxia have become a serious environmental problem in many coastal ecosystems, and recent evidence suggests an increase in the number of systems experiencing hypoxia globally and an increased frequency and duration of hypoxia in many historically hypoxic systems. Eutrophication, low physical energy and large freshwater input are some of the most important factors, which lead to the development of hypoxia in coastal areas. The Amvrakikos Gulf, located in western Greece, is one of the most important protected areas in Greece and in Europe and past studies indicated that some regions of the Gulf experience hypoxia. Despite the importance of the Amvrakikos Gulf ecosystem, little is known about key ecological, chemical, and physical processes in the Gulf and their relationship with oxygen depletion. In the present study, authors try to answer some important questions regarding the distribution and variation of the hypoxic zone. After a year of measurements, it was concluded that according to spatial distribution of DO, the gulf can be divided into two parts, the western and eastern areas, with important differences occurring between them. Within the western area, the water column was well oxygenated during winter and spring and hypoxic conditions occurred only in summer and autumn. The eastern area was hypoxic throughout the year and anoxic conditions occurred only during autumn. In conclusion, taking into account the author's measurements and previous studies, the seasonally hypoxic eastern area in 1987 converted into a seasonally anoxic area in 2009 and the western part of the gulf, remained seasonally hypoxic, indicating the degradation of the gulf's environmental state within the last 20 years.

  14. Anoxic Androgen Degradation by the Denitrifying Bacterium Sterolibacterium denitrificans via the 2,3-seco Pathway

    PubMed Central

    Wang, Po-Hsiang; Yu, Chang-Ping; Lee, Tzong-Huei; Lin, Ching-Wen; Ismail, Wael; Wey, Shiaw-Pyng; Kuo, An-Ti

    2014-01-01

    The biodegradation of steroids is a crucial biochemical process mediated exclusively by bacteria. So far, information concerning the anoxic catabolic pathways of androgens is largely unknown, which has prevented many environmental investigations. In this work, we show that Sterolibacterium denitrificans DSMZ 13999 can anaerobically mineralize testosterone and some C19 androgens. By using a 13C-metabolomics approach and monitoring the sequential appearance of the intermediates, we demonstrated that S. denitrificans uses the 2,3-seco pathway to degrade testosterone under anoxic conditions. Furthermore, based on the identification of a C17 intermediate, we propose that the A-ring cleavage may be followed by the removal of a C2 side chain at C-5 of 17-hydroxy-1-oxo-2,3-seco-androstan-3-oic acid (the A-ring cleavage product) via retro-aldol reaction. The androgenic activities of the bacterial culture and the identified intermediates were assessed using the lacZ-based yeast androgen assay. The androgenic activity in the testosterone-grown S. denitrificans culture decreased significantly over time, indicating its ability to eliminate androgens. The A-ring cleavage intermediate (≤500 μM) did not exhibit androgenic activity, whereas the sterane-containing intermediates did. So far, only two androgen-degrading anaerobes (Sterolibacterium denitrificans DSMZ 13999 [a betaproteobacterium] and Steroidobacter denitrificans DSMZ 18526 [a gammaproteobacterium]) have been isolated and characterized, and both of them use the 2,3-seco pathway to anaerobically degrade androgens. The key intermediate 2,3-seco-androstan-3-oic acid can be used as a signature intermediate for culture-independent environmental investigations of anaerobic degradation of C19 androgens. PMID:24657867

  15. Iron reactivity in anoxic sediments in the Ría de Vigo (NW Spain).

    PubMed

    Ramírez-Pérez, A M; de Blas, E

    2017-05-01

    The high sedimentation rates and high organic matter contents in the sediments of the Ría de Vigo (NW Spain) promote the development of anoxic conditions, determining the dynamics of elements like Fe and conditioning his speciation and reactivity. Four gravity cores were retrieved in anoxic sediments of the Ría de Vigo in November 2012. In order to understand the behavior of Fe in these complex environments different fractions of reactive iron were analyzed. The decrease in highly reactive iron and sulfide contents with depth showed the relationship between the iron and sulfur cycle in the middle and outer zones of the ría. In the inner zone, the apparition of shallow methane gas may cause the slower decrease of the highly reactive iron contents. In zones without methane, sediment layers enriched in iron -with a reactivity higher than in other sediment samples- were observed. An increase was observed in the dithionite and total reactive iron contents from the inner to the outer zone of the ría, according to the gas depth. Furthermore, a decrease in Fe (III)-bearing minerals contents with depth was observed in the outer and middle zones, but not in the innermost area where the gas is shallow. The high organic matter and sulfide contents, mainly in the inner zone of the ría, indicate that the most of the Fe (II) is FeS. Moreover, the high contents of total reactive iron and pH values (6.86-7.98) could contribute the formation of stable minerals like pyrite along the Ría de Vigo. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Sulfur isotopes track the global extent and dynamics of euxinia during Cretaceous Oceanic Anoxic Event 2

    PubMed Central

    Owens, Jeremy D.; Gill, Benjamin C.; Jenkyns, Hugh C.; Bates, Steven M.; Severmann, Silke; Kuypers, Marcel M. M.; Woodfine, Richard G.; Lyons, Timothy W.

    2013-01-01

    The Mesozoic Era is characterized by numerous oceanic anoxic events (OAEs) that are diagnostically expressed by widespread marine organic-carbon burial and coeval carbon-isotope excursions. Here we present coupled high-resolution carbon- and sulfur-isotope data from four European OAE 2 sections spanning the Cenomanian–Turonian boundary that show roughly parallel positive excursions. Significantly, however, the interval of peak magnitude for carbon isotopes precedes that of sulfur isotopes with an estimated offset of a few hundred thousand years. Based on geochemical box modeling of organic-carbon and pyrite burial, the sulfur-isotope excursion can be generated by transiently increasing the marine burial rate of pyrite precipitated under euxinic (i.e., anoxic and sulfidic) water-column conditions. To replicate the observed isotopic offset, the model requires that enhanced levels of organic-carbon and pyrite burial continued a few hundred thousand years after peak organic-carbon burial, but that their isotope records responded differently due to dramatically different residence times for dissolved inorganic carbon and sulfate in seawater. The significant inference is that euxinia persisted post-OAE, but with its global extent dwindling over this time period. The model further suggests that only ∼5% of the global seafloor area was overlain by euxinic bottom waters during OAE 2. Although this figure is ∼30× greater than the small euxinic fraction present today (∼0.15%), the result challenges previous suggestions that one of the best-documented OAEs was defined by globally pervasive euxinic deep waters. Our results place important controls instead on local conditions and point to the difficulty in sustaining whole-ocean euxinia. PMID:24170863

  17. Effects of Mn(II) on UO2 dissolution under anoxic and oxic conditions.

    PubMed

    Wang, Zimeng; Tebo, Bradley M; Giammar, Daniel E

    2014-05-20

    Groundwater composition and coupled redox cycles can affect the long-term stability of U(IV) products from bioremediation. The effects of Mn(II), a redox active cation present at uranium-contaminated sites, on UO2 dissolution in both oxic and anoxic systems were investigated using batch and continuous-flow reactors. Under anoxic conditions Mn(II) inhibited UO2 dissolution, which was probably due to adsorption of Mn(II) and precipitation of MnCO3 that decreased exposure of U(IV) surface sites to oxidants. In contrast, Mn(II) promoted UO2 dissolution under oxic conditions through Mn redox cycling. Oxidation of Mn(II) by O2 produced reactive Mn species, possibly short-lived Mn(III) in solution or at the surface, that oxidatively dissolved the UO2 more rapidly than could the O2 alone. At pH 8 the Mn cycling was such that there was no measurable accumulation of particulate Mn oxides. At pH 9 Mn oxides could be produced and accumulate, while they were continuously reduced by UO2, with Mn(II) returning to the aqueous phase. With the rapid turnover of Mn in the redox cycle, concentrations of Mn as low as 10 μM could maintain an enhanced UO2 dissolution rate. The presence of the siderophore desferrioxamine B (a strong Mn(III)-complexing ligand) effectively decoupled the redox interactions of uranium and manganese to suppress the promotional effect of Mn(II).

  18. Sulfur isotopes track the global extent and dynamics of euxinia during Cretaceous Oceanic Anoxic Event 2.

    PubMed

    Owens, Jeremy D; Gill, Benjamin C; Jenkyns, Hugh C; Bates, Steven M; Severmann, Silke; Kuypers, Marcel M M; Woodfine, Richard G; Lyons, Timothy W

    2013-11-12

    The Mesozoic Era is characterized by numerous oceanic anoxic events (OAEs) that are diagnostically expressed by widespread marine organic-carbon burial and coeval carbon-isotope excursions. Here we present coupled high-resolution carbon- and sulfur-isotope data from four European OAE 2 sections spanning the Cenomanian-Turonian boundary that show roughly parallel positive excursions. Significantly, however, the interval of peak magnitude for carbon isotopes precedes that of sulfur isotopes with an estimated offset of a few hundred thousand years. Based on geochemical box modeling of organic-carbon and pyrite burial, the sulfur-isotope excursion can be generated by transiently increasing the marine burial rate of pyrite precipitated under euxinic (i.e., anoxic and sulfidic) water-column conditions. To replicate the observed isotopic offset, the model requires that enhanced levels of organic-carbon and pyrite burial continued a few hundred thousand years after peak organic-carbon burial, but that their isotope records responded differently due to dramatically different residence times for dissolved inorganic carbon and sulfate in seawater. The significant inference is that euxinia persisted post-OAE, but with its global extent dwindling over this time period. The model further suggests that only ~5% of the global seafloor area was overlain by euxinic bottom waters during OAE 2. Although this figure is ~30× greater than the small euxinic fraction present today (~0.15%), the result challenges previous suggestions that one of the best-documented OAEs was defined by globally pervasive euxinic deep waters. Our results place important controls instead on local conditions and point to the difficulty in sustaining whole-ocean euxinia.

  19. Evidence for Global Biogeochemical Changes During the Toarcian Oceanic Anoxic Event

    NASA Astrophysics Data System (ADS)

    Them, T. R., II; Gill, B. C.; Gröcke, D. R.; Selby, D. S.; Martindale, R. C.; Caruthers, A. H.; Tulsky, E. T. T.

    2015-12-01

    The global versus regional nature of the Toarcian Oceanic Anoxic Event (T-OAE; ~183 million years ago) has been heavily debated over the course of the last decade. Several lines of geochemical evidence support a significant perturbation to the carbon cycle and redox-sensitive elemental cycles across this interval. It is thought that these represent feedbacks to the emplacement of the Karoo-Ferrar large igneous province. These include: elevated atmospheric pCO2, an enhanced greenhouse effect and hydrologic cycle leading to increased weathering rates, dissociation of biogenic methane clathrates, and widespread ocean anoxia. Despite evidence for these global phenomena, the overwhelming majority of stratigraphic successions studied are located in Europe. The global magnitude of these biogeochemical perturbations has been challenged, with some considering that this event was regional to Europe, and others suggesting that the carbon isotope excursion (CIE) itself is not a reliable stratigraphic marker. In order to test these competing hypotheses, we have generated a geochemical dataset to reconstruct paleoceanographic and paleoclimatological changes across the T-OAE from western North America. The Toarcian strata in western Alberta consist primarily of organic-rich calcareous siltstones and shales. These deposits represent ideal sedimentary facies to reconstruct environmental changes through the use of geochemical proxy data, especially those that use redox-sensitive transition metals. Ammonite biostratigraphy suggests a nearly continuous sequence from the late Pliensbachian to middle Toarcian. The organic carbon isotopes show the prominent negative CIE interpreted to relate to the release of isotopically depleted carbon at the onset of the T-OAE. Pyrite sulfur weight percentages increase across the CIE and remain elevated, and iron speciation data suggest the development of anoxic conditions. Initial osmium isotope compositions become more radiogenic during the CIE

  20. Timing and evolution of ocean anoxic event during Early Cambrian in south China

    NASA Astrophysics Data System (ADS)

    Yang, J.; Jiang, S.; Pi, D.; Ling, H.

    2008-12-01

    The Precambrian/Cambrian (PC-C) interval is one of the most interesting intervals in the evolution of life because of the sudden diversification of animals with mineralized skeletons, known as "Cambrian Explosion". The Yangtze Platform in south China is one of the best occurrences that can provide excellent insights into the palaeo-environmental and biological changes across the PC-C boundary. Our study show that the ocean anoxia were widespread during the Early Cambrian period, however, the start of this anoxic event was not from the PC-C boundary (i.e., 542 Ma), but some 7 Ma later (~535 Ma) when the Niutitang Formation black rock series (black phosphorite, chert, and black shale) deposited along a thousand kilometer long NEE zone in the transitional facies in the Yangtze Platform, while the major Cambrian radiation (Changjiang fauna) took place during 521-511 Ma. During the Niutitang period, the depositional environment of the Early Cambrian sedimentary sequence in south China have evolved from an initial oxic/dysoxic to a major anoxic/euxinic environment, and then back to dysoxic/oxic environment. A Ni-Mo sulfide layer occurred in the lower part of the Niutitang black shales which contains extremely enrichments of many metals, and can serve as a marker layer in south China when the depositional environment turned into euxinic condition. Re-Os isotope study of the sulfide ores and host black shales show an age of 535 Ma. Initial Os isotopic compositions, Mo isotopic compositions, and rare earth elements and Pt group element geochemistry suggest involvement of submarine hydrothermal fluids during the metal enrichments in black shale.

  1. Identification of Methanoculleus spp. as Active Methanogens during Anoxic Incubations of Swine Manure Storage Tank Samples

    PubMed Central

    Barret, Maialen; Gagnon, Nathalie; Kalmokoff, Martin L.; Topp, Edward; Verastegui, Yris; Brooks, Stephen P. J.; Matias, Fernando; Neufeld, Josh D.

    2013-01-01

    Methane emissions represent a major environmental concern associated with manure management in the livestock industry. A more thorough understanding of how microbial communities function in manure storage tanks is a prerequisite for mitigating methane emissions. Identifying the microorganisms that are metabolically active is an important first step. Methanogenic archaea are major contributors to methanogenesis in stored swine manure, and we investigated active methanogenic populations by DNA stable isotope probing (DNA-SIP). Following a preincubation of manure samples under anoxic conditions to induce substrate starvation, [U-13C]acetate was added as a labeled substrate. Fingerprint analysis of density-fractionated DNA, using length-heterogeneity analysis of PCR-amplified mcrA genes (encoding the alpha subunit of methyl coenzyme M reductase), showed that the incorporation of 13C into DNA was detectable at in situ acetate concentrations (∼7 g/liter). Fingerprints of DNA retrieved from heavy fractions of the 13C treatment were primarily enriched in a 483-bp amplicon and, to a lesser extent, in a 481-bp amplicon. Analyses based on clone libraries of the mcrA and 16S rRNA genes revealed that both of these heavy DNA amplicons corresponded to Methanoculleus spp. Our results demonstrate that uncultivated methanogenic archaea related to Methanoculleus spp. were major contributors to acetate-C assimilation during the anoxic incubation of swine manure storage tank samples. Carbon assimilation and dissimilation rate estimations suggested that Methanoculleus spp. were also major contributors to methane emissions and that the hydrogenotrophic pathway predominated during methanogenesis. PMID:23104405

  2. Enhanced dechlorination of tetrachloroethylene by zerovalent silicon in the presence of polyethylene glycol under anoxic conditions.

    PubMed

    Lee, Chun-Chi; Doong, Ruey-An

    2011-03-15

    The combination of zerovalent silicon (Si(0)) with polyethylene glycol (PEG) is a novel technique to enhance the dechlorination efficiency and rate of chlorinated hydrocarbons. In this study, the dechlorination of tetrachloroethylene (PCE) by Si(0) in the presence of various concentrations of PEG was investigated under anoxic conditions. Several surfactants including cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and Tween 80 were also selected for comparison. Addition of SDS and Tween 80 had little effect on the enhancement of PCE dechlorination, while CTAB and PEG significantly enhanced the dechlorination efficiency and rate of PCE by Si(0) under anoxic conditions. The Langmuir-Hinshelwood model was used to describe the dechlorination kinetics of PCE and could be simplified to pseudo-first-order kinetics at low PCE concentration. The rate constants (k(obs)) for PCE dechlorination were 0.21 and 0.36 h(-1) in the presence of CTAB and PEG, respectively. However, the reaction mechanisms for CTAB and PEG are different. CTAB could enhance the apparent water solubility of PCE in solution containing Si(0), leading to the enhancement of dechlorination efficiency and rate of PCE, while PEG prevented the formation of silicon dioxide, and significantly enhanced the dechlorination efficiency and rate of PCE at pH 8.3 ± 0.2. In addition, the dechlorination rate increased upon increasing PEG concentration and then leveled off to a plateau when the PEG concentration was higher than 0.2 μM. The k(obs) for PCE dechlorination by Si(0) in the presence of PEG was 106 times higher than that by Si(0) alone. Results obtained in this study would be helpful in facilitating the development of processes that could be useful for the enhanced degradation of cocontaminants by zerovalent silicon.

  3. Microstructural Characterization of U Coprecipitated Phases Formed in Bentonic-Granitic Groundwater and Under Anoxic Conditions

    SciTech Connect

    Quinones, Javier; Iglesias, Eduardo; Cobo, Jose M.; Martinez Esparza, Aurora; Gomez de Salazar, Jose Maria

    2007-07-01

    For improving the accuracy of the performance assessment studies related to the spent fuel safety under storage conditions, it is necessary to develop a new matrix alteration model. These models must be based on laboratory experiences and they should be capable of extrapolating storage environmental conditions. The most recent models developed include the oxidation and dissolution process of the spent fuel matrix, but the influence of a possible process of secondary phase formation over the spent fuel surface was not yet taken into account. This is a key process that could produce a reduction of the matrix dissolution rate/radiation shielding behaviour; however, the surface precipitation of the secondary phase could induce a localized corrosion process, in which case the dissolution rate of the spent fuel would be increased. This paper is focussed on microstructural characterization of secondary phases formed in co-precipitation experiments performed under anoxic conditions in granitic-bentonitic simulated groundwater. In order to simulate the influence of the container material, the co-precipitation experiments were performed in the absence and presence of iron powder. The solid phases formed were characterized using the following techniques: XRD; SEM-EDX, and TEM-EDX. The XRD diffraction pattern showed that under anoxic conditions, a mixture of phases were obtained (sodium and potassium uranate and schoepite), whereas uranate phases were detected when only iron was present. The characterization study indicates that the U secondary phase formed (under reducing conditions and in the presence of iron powder) growth from the iron surface. The crystal size of the secondary phase is independent of the presence of iron powder (and it is always less than 3 {mu}m). Furthermore, the microstructural study showed the growing of U phases over iron powder. (authors)

  4. Simulating the onset and spread of anoxic conditions during Cretaceous OAE2

    NASA Astrophysics Data System (ADS)

    Wallmann, Klaus; Floegel, S.; Poulsen, C.; Voigt, S.; Kuhnt, W.

    2010-05-01

    A new model of the global atmosphere-ocean-continent-mantle system was set-up to investigate the triggering of the Oceanic Anoxic Event OAE2 through volcanic degassing processes at large igneous provinces (LIPs). The model simulates the changes in oceanic dissolved oxygen, phosphate, and carbon and the evolution of atmospheric pCO2 values under mid-Cretaceous boundary conditions. It considers the effects of pCO2 on element ratios in marine plankton (C : P) and includes new parameterizations for phosphorus and carbon burial at the seafloor based on modern observations. Independent isotopic and chemical time-series of ocean and atmosphere change over OAE2 are applied to evaluate the model results. The model results support the hypothesis that OAE2 was triggered by massive CO2 emissions at LIPs. According to the model, the phosphorus weathering flux into the ocean and the C : P ratio in marine plankton were enhanced by the rise in surface temperature and atmosphere pCO2 caused by mantle degassing. Marine export production and oxygen consumption in intermediate and deep water masses increased in response to the expansion of the dissolved phosphate inventory of the ocean and the change in plankton element ratios. The spread of anoxic conditions in bottom waters -induced by enhanced carbon export and respiration- was further amplified by the oxygen-dependent burial of phosphorus in marine sediments in a positive feedback loop. The modeling implies that enhanced CO2 emissions favor the spread of low-oxygen conditions also in modern oceans.

  5. Simultaneous removal of organic matter and nitrogen compounds by an aerobic/anoxic membrane biofilm reactor.

    PubMed

    Hasar, Halil; Xia, Siqing; Ahn, Chang Hoon; Rittmann, Bruce E

    2008-09-01

    The hydrogen-based membrane biofilm reactor (MBfR) has been well studied and applied for denitrification of nitrate-containing water and wastewater. Adding an oxygen-based MBfR allows total-nitrogen removal when the input nitrogen is ammonium. However, most wastewaters also contain a significant concentration or organic material, measured as chemical oxygen demand (COD). This study describes experiments to investigate the removal of organic and nitrogenous compounds in the combined Aerobic/Anoxic MBfR, in which an Aerobic MBfR (Aer MBfR) precedes an Anoxic MBfR (An MBfR). The experiments demonstrate that the Aer/An MBfR combination accomplished COD oxidation and nitrogen removal for a total oxygen demand flux (i.e., from COD and NH(4) oxidations) in the range of 1.2-7.2 g O(2)/m(2)-d for 4.5 psi (0.3 atm) oxygen pressure to the Aer MBfR, but was overloaded and did not accomplish nitrification for the total oxygen demand load higher than 14 g O(2)/m(2)-d. Total-nitrogen removal was controlled by nitrification in the Aer MBfR, because the An MBfR denitrified all NO(3)(-) provided to it by the Aer MBfR. The overload of total oxygen demand did not affect COD oxidation in the Aer MBfR, but caused a small increase of COD in the An MBfR due to net release of soluble microbial products (SMP).

  6. Effect of Cretaceous oceanic anoxic events on the evolutionary trend of planktonic foraminifera

    NASA Astrophysics Data System (ADS)

    Kuroyanagi, A.; Ozaki, K.; Kawahata, H.

    2014-12-01

    It is widely thought that oceanic redox state is essential for the evolutionary history of life on the earth, and "anoxic events" have been proposed as one of the causal mechanisms for mass extinctions. During mid-Cretaceous, widely known as the extremely warm period, oceanic anoxic events (OAEs) occurred several times and they would have caused a substantial impact on the biosphere. Planktonic foraminifera are marine planktons with calcite tests and their productions constitute ~30-80% of the modern deep-marine calcite budget, thus they play an important role in the global carbon cycle. Previous study reported that planktonic foraminifera displayed the high turnover (extinction and speciation) rate at or near the major OAEs. However, the impact of Cretaceous OAEs on the evolutionary trend of planktonic foraminifera remains obscure. In this study, we investigated the role of spatiotemporal extent of anoxia on the evolutionary trend of planktonic foraminifera by assessing the extinction/speciation rate of planktonic foraminifera around Cretaceous OAEs. The number of foraminiferal species increased across the OAE1a and then showed a peak after this episode. Around OAE2, several planktonic foraminifera species became extinct and several speciated, however, long-term trends in foraminiferal evolution showed no drastic changes near the event. Therefore these results suggest that the ocean surface environment at OAEs would not have a direct effect on foraminiferal extinction/speciation. This interpretation is reinforced when considering the recent culturing results, which demonstrate that modern planktonic foraminifera have a high tolerance to extremely low dissolved oxygen levels than expected. Accumulating geochemical data also suggest a spatial heterogeneity of oceanic anoxia/euxinia during OAE2. These results lead us to conclude that Cretaceous OAEs would not directly related to planktonic foraminiferal extinction due to regional distribution of anoxia/euxinia.

  7. Intracellular glutathione in the protection from anoxic injury in renal proximal tubules.

    PubMed Central

    Mandel, L J; Schnellmann, R G; Jacobs, W R

    1990-01-01

    Previous results (Weinberg, J. M., J. A. David, M. Abarzua, and T. Rajan. 1987. J. Clin. Invest. 80:1446-1454) have shown that GSH and glycine (GLY) are cytoprotective during anoxia when added extracellularly. The present studies investigate the role that intracellular GSH plays in this cytoprotection. Proximal renal tubules in suspension prepared with either high (11 +/- 1 nmol/mg protein) or low (6 +/- 1 nmol/mg protein) GSH contents were subjected to 40 min of anoxia and 40 min of reoxygenation. Low GSH tubules were protected from plasma membrane damage during anoxia by exogenous addition of 1 mM GSH or GLY, reducing lactate dehydrogenase (LDH) release from 42 +/- 7 to 14 +/- 1 and 10 +/- 1%, respectively. High GSH tubules were equally protected from anoxic damage without exogenous additions. Since the high GSH content approximates the in vivo values, it may be concluded that GSH may be cytoprotective during anoxia in vivo. However, it is not the intracellular GSH itself that is cytoprotective; rather, this protection resides in the ability to produce GLY, which appears to be the cytoprotective agent. Alanine was also shown to have similar cytoprotective properties, although higher concentrations were required. Sulfhydryl reducing agents such as cysteine and dithiothreitol offered less, but significant protection from anoxic damage. Protection by GSH, GLY, or alanine was not associated with higher ATP levels during anoxia. Tubules that were protected from membrane damage during anoxia recovered oxygen consumption and K and ATP contents significantly better during reoxygenation than unprotected tubules. Images PMID:2298907

  8. Characterization of microbial arsenate reduction in the anoxic bottom waters of Mono Lake, California

    USGS Publications Warehouse

    Hoeft, S.E.; Lucas, F.; Hollibaugh, J.T.; Oremland, R.S.

    2002-01-01

    Dissimilatory reduction of arsenate (DAsR) occurs in the arsenic-rich, anoxic water column of Mono Lake, California, yet the microorganisms responsible for this observed in situ activity have not been identified. To gain insight as to which microorganisms mediate this phenomenon, as well as to some of the biogeochemical constraints on this activity, we conducted incubations of arsenate-enriched bottom water coupled with inhibition/amendment studies and Denaturing Gradient Gel Electrophoresis (DGGE) characterization techniques. DAsR was totally inhibited by filter-sterilization and by nitrate, partially inhibited (~50%) by selenate, but only slightly (~25%) inhibited by oxyanions that block sulfate-reduction (molybdate and tungstate). The apparent inhibition by nitrate, however, was not due to action as a preferred electron acceptor to arsenate. Rather, nitrate addition caused a rapid, microbial re-oxidation of arsenite to arsenate, which gave the overall appearance of no arsenate loss. A similar microbial oxidation of As(III) was also found with Fe(III), a fact that has implications for the recycling of As(V) in Mono Lake's anoxic bottom waters. DAsR could be slightly (10%) stimulated by substrate amendments of lactate, succinate, malate, or glucose, but not by acetate, suggesting that the DAsR microflora is not electron donor limited. DGGE analysis of amplified 16S rDNA gene fragments from incubated arsenate-enriched bottom waters revealed the presence of two bands that were not present in controls without added arsenate. The resolved sequences of these excised bands indicated the presence of members of the epsilon (Sulfurospirillum) and delta (Desulfovibrio) subgroups of the Proteobacteria, both of which have representative species that are capable of anaerobic growth using arsenate as their electron acceptor.

  9. BASINS Tutorials and Training

    EPA Pesticide Factsheets

    A series of lectures and exercises on how to use BASINS for water quality modeling and watershed assessment. The lectures follow sequentially. Companion exercises are provided for users to practice different BASINS water quality modeling techniques.

  10. BASINS Technical Notes

    EPA Pesticide Factsheets

    EPA has developed several technical notes that provide in depth information on a specific function in BASINS. Technical notes can be used to answer questions users may have, or to provide additional information on the application of features in BASINS.

  11. Los Angeles Basin

    NASA Image and Video Library

    2009-06-29

    The Los Angeles Basin is bordered on the north by the San Gabriel Mountains. Other smaller basins are separated by smaller mountain ranges, like the Verdugo Hills, and the Santa Monica Mountains in this image from NASA Terra spacecraft.

  12. Geochemical and biostratigraphic characterization of an upper Cretaceous organic-rich condensed section in the Santos Basin, Brazil

    SciTech Connect

    Trindade, L.A.F., Porsche, E.; Penteado, H.L.B. )

    1996-01-01

    The Cenomanian-Turonian section is worldwide recognized as an organic- rich interval associated with a widespread anoxic event. Samples from this interval, representing proximal sedimentary conditions have been well characterized in the Santos Basin, Brazil, where it reaches 300m thickness. The main objective of this study is to characterize the geochemical and paleoecological attributes as well as to ascertain the biostratigraphic position of this organic-rich section in a more distal location, at ODP Site 356. Biostratigraphic analyses identify die interval at ODP Site 356 as a condensed section ranging in age from Cenomanian to Coniacian (11 m), deposited under anoxic conditions associated with a warm, and climate in the adjacent continental areas. Geochemical analyses indicate high total organic carbon contents (up tp 6.7%), dominance of algal derived material, high relative abundances of homohopanes and methylsteranes, [delta][sup 13]C around -27[per thousand], indicating a typical marine anoxic section. Despite the high content of oil-prone organic matter, this section has not attained thermal evolution appropriated for hydrocarbon generation due to its shallow burial. In proximal areas of the basin, this section is interpreted as a transgressive system tract which is composed by a series of sequences, that are enriched in organic material at their bases. Basinward the interval is thinner, but presents higher organic carbon contents according to geochemical data of ODP Site 356, typical of a condensed section.

  13. Geochemical and biostratigraphic characterization of an upper Cretaceous organic-rich condensed section in the Santos Basin, Brazil

    SciTech Connect

    Trindade, L.A.F., Porsche, E.; Penteado, H.L.B.

    1996-12-31

    The Cenomanian-Turonian section is worldwide recognized as an organic- rich interval associated with a widespread anoxic event. Samples from this interval, representing proximal sedimentary conditions have been well characterized in the Santos Basin, Brazil, where it reaches 300m thickness. The main objective of this study is to characterize the geochemical and paleoecological attributes as well as to ascertain the biostratigraphic position of this organic-rich section in a more distal location, at ODP Site 356. Biostratigraphic analyses identify die interval at ODP Site 356 as a condensed section ranging in age from Cenomanian to Coniacian (11 m), deposited under anoxic conditions associated with a warm, and climate in the adjacent continental areas. Geochemical analyses indicate high total organic carbon contents (up tp 6.7%), dominance of algal derived material, high relative abundances of homohopanes and methylsteranes, {delta}{sup 13}C around -27{per_thousand}, indicating a typical marine anoxic section. Despite the high content of oil-prone organic matter, this section has not attained thermal evolution appropriated for hydrocarbon generation due to its shallow burial. In proximal areas of the basin, this section is interpreted as a transgressive system tract which is composed by a series of sequences, that are enriched in organic material at their bases. Basinward the interval is thinner, but presents higher organic carbon contents according to geochemical data of ODP Site 356, typical of a condensed section.

  14. The abiotic degradation of methyl parathion in anoxic sulfur-containing system mediated by natural organic matter.

    PubMed

    Liao, Xiaoping; Zhang, Caixiang; Wang, Yanxin; Tang, Mi

    2017-06-01

    Although the kinetics and transformation of methyl parathion have been investigated extensively, its abiotic degradation mechanism in anoxic sulfur-containing groundwater system is still not clear. In this work, the abiotic degradation of methyl parathion in anoxic sulfur-containing system mediated by natural organic matter (NOM) was investigated in batch experiments. It was found that the removal of methyl parathion (up to 80.7%) was greatly improved in sulfide containing NOM compared to those in sulfide alone (with 15.5%) and in NOM alone (almost negligible). Various sulfur species presented significant differences in behaviors methyl parathion degradation, but followed by the pseudo-first-order model well. No facilitated degradation of methyl parathion was observed in sulfite (SO3(2-)) or thiosulfate (S2O3(2-)) containing NOM such as anthraquinone. Although elemental sulfur (S(0)) and cysteine could further improve the degradation rate of methyl parahtion, their impacts was very limited. The removal efficiency of methyl parathion in anoxic sulfur-containing system were related remarkably with NOM concentration and solution pH. Based on the transformation products identified by gas chromatography-mass spectrometer (GC/MS) and liquid chromatography high resolution mass spectrometer (LC/HRMS), both the nitro group reduction and hydrolysis (SN@C) processes by sulfide (HS(-)) were further proved to be two predominant reaction mechanisms for the abiotic degradation of methyl parathion in anoxic sulfur-containing system. The results of this study help to understand the natural attenuation of methyl parathion under anoxic sulfide-containing groundwater system mediated by NOM.

  15. Metatranscriptomic Analyses of Plankton Communities Inhabiting Surface and Subpycnocline Waters of the Chesapeake Bay during Oxic-Anoxic-Oxic Transitions

    PubMed Central

    Eggleston, Erin M.; Doherty, Mary; Lee, Dong Yoon; Owens, Michael; Shapleigh, James P.; Cornwell, Jeffrey C.; Crump, Byron C.

    2014-01-01

    We used metatranscriptomics to study the gene transcription patterns of microbial plankton (0.2 to 64 μm) at a mesohaline station in the Chesapeake Bay under transitions from oxic to anoxic waters in spring and from anoxic to oxic waters in autumn. Samples were collected from surface (i.e., above pycnocline) waters (3 m) and from waters beneath the pycnocline (16 to 22 m) in both 2010 and 2011. Metatranscriptome profiles based on function and potential phylogeny were different between 2010 and 2011 and strongly variable in 2011. This difference in variability corresponded with a highly variable ratio of eukaryotic to bacterial sequences (0.3 to 5.5), reflecting transient algal blooms in 2011 that were absent in 2010. The similarity between metatranscriptomes changed at a lower rate during the transition from oxic to anoxic waters than after the return to oxic conditions. Transcripts related to photosynthesis and low-affinity cytochrome oxidases were significantly higher in shallow than in deep waters, while in deep water genes involved in anaerobic metabolism, particularly sulfate reduction, succinyl coenzyme A (succinyl-CoA)-to-propionyl-CoA conversion, and menaquinone synthesis, were enriched relative to in shallow waters. Expected transitions in metabolism between oxic and anoxic deep waters were reflected in elevated levels of anaerobic respiratory reductases and utilization of propenediol and acetoin. The percentage of archaeal transcripts increased in both years in late summer (from 0.1 to 4.4% of all transcripts in 2010 and from 0.1 to 6.2% in 2011). Denitrification-related genes were expressed in a predicted pattern during the oxic-anoxic transition. Overall, our data suggest that Chesapeake Bay microbial assemblages express gene suites differently in shallow and deep waters and that differences in deep waters reflect variable redox states. PMID:24162577

  16. Effect of H2S concentration on planktonic foraminifera through laboratory culture experiments and implications for oceanic anoxic events

    NASA Astrophysics Data System (ADS)

    Kuroyanagi, A.; Toyofuku, T.; Nagai, Y.; Kimoto, K.; Kawahata, H.; Takashima, R.; Nishi, H.

    2016-12-01

    During Cretaceous oceanic anoxic events (OAEs), substantial turnover of planktonic foraminiferal species occurred, however, the direct effects of the anoxic condition on planktonic foraminifera remain obscure. Culture experiments controlling dissolved oxygen levels exhibited that modern planktonic foraminifera (both symbiont and non-symbiont species) could survive, add chambers, feed, and undergo gametogenesis even under dysoxic conditions (> 0.7 mg O2 L-1 or 22 µmol O2 L-1), thus dysoxic condition could not have directly caused the extinction of planktonic foraminifera during OAEs. However, the biological responses under more reductive condition (i.e., anoxic and/or occurrence of hydrogen sulfide) have been still unknown. In the study, we cultured various foraminiferal species under different hydrogen sulfide (H2S) concentrations, and examined the biological effect of anoxic condition on planktonic foraminifera. In this study, we cultured 6 species (n = 31) in all at three treatments: 2 mg H2S l-1 (H1 treatments), 9 mg H2S l-1 (H2 treatments), and control (without H2S). All planktonic foraminifera could not survive more than 48 hours with H2S of > 2 mg l-1 except for control treatments. Furthermore, gametogenesis ratio of each H2S treatments showed considerable low value; 8% (H1) and 17% (H2), and time to gametogenesis was also very short in both treatments. The results revealed that the presence of H2S have a fairly serious biological effect on planktonic foraminifera, and suggests that the disoxic condition (i.e., low dissolved oxygen, DO10%) should be fundamentally different from anoxic with the presence of H2S in biological responses, when it comes to oxygen-depleted environments for planktonic foraminifera at OAEs.

  17. Metatranscriptomic analyses of plankton communities inhabiting surface and subpycnocline waters of the Chesapeake Bay during oxic-anoxic-oxic transitions.

    PubMed

    Hewson, Ian; Eggleston, Erin M; Doherty, Mary; Lee, Dong Yoon; Owens, Michael; Shapleigh, James P; Cornwell, Jeffrey C; Crump, Byron C

    2014-01-01

    We used metatranscriptomics to study the gene transcription patterns of microbial plankton (0.2 to 64 μm) at a mesohaline station in the Chesapeake Bay under transitions from oxic to anoxic waters in spring and from anoxic to oxic waters in autumn. Samples were collected from surface (i.e., above pycnocline) waters (3 m) and from waters beneath the pycnocline (16 to 22 m) in both 2010 and 2011. Metatranscriptome profiles based on function and potential phylogeny were different between 2010 and 2011 and strongly variable in 2011. This difference in variability corresponded with a highly variable ratio of eukaryotic to bacterial sequences (0.3 to 5.5), reflecting transient algal blooms in 2011 that were absent in 2010. The similarity between metatranscriptomes changed at a lower rate during the transition from oxic to anoxic waters than after the return to oxic conditions. Transcripts related to photosynthesis and low-affinity cytochrome oxidases were significantly higher in shallow than in deep waters, while in deep water genes involved in anaerobic metabolism, particularly sulfate reduction, succinyl coenzyme A (succinyl-CoA)-to-propionyl-CoA conversion, and menaquinone synthesis, were enriched relative to in shallow waters. Expected transitions in metabolism between oxic and anoxic deep waters were reflected in elevated levels of anaerobic respiratory reductases and utilization of propenediol and acetoin. The percentage of archaeal transcripts increased in both years in late summer (from 0.1 to 4.4% of all transcripts in 2010 and from 0.1 to 6.2% in 2011). Denitrification-related genes were expressed in a predicted pattern during the oxic-anoxic transition. Overall, our data suggest that Chesapeake Bay microbial assemblages express gene suites differently in shallow and deep waters and that differences in deep waters reflect variable redox states.

  18. Crude oil in a shallow sand and gravel aquifer-III. Biogeochemical reactions and mass balance modeling in anoxic groundwater

    USGS Publications Warehouse

    Baedecker, M.J.; Cozzarelli, I.M.; Eganhouse, R.P.; Siegel, D.I.; Bennett, P.C.

    1993-01-01

    Crude oil floating on the water table in a sand and gravel aquifer provides a constant source of hydrocarbons to the groundwater at a site near Bemidji, Minnesota. The degradation of hydrocarbons affects the concentrations of oxidized and reduced aqueous species in the anoxic part of the contaminant plume that developed downgradient from the oil body. The concentrations of Fe2+, Mn2+ and CH4, Eh measurements, and the ??13C ratios of the total inorganic C indicate that the plume became more reducing ver a 5-a period. However, the size of the contaminant plume remained stable during this time. Field data coupled with laboratory microcosm experiments indicate that benzene and the alkylbenzenes are degraded in an anoxic environment. In anaerobic microcosm experiments conducted under field conditions, almost complete degradation (98%) was observed for benzene in 125 d and for toluene in 45 d. Concentrations of aqueous Fe2+ and Mn2+ increased in these experiments, indicating that the primary reactions were hydrocarbon degradation coupled with Fe and Mn reduction. Mass transfer calculations on a 40-m flowpath in the anoxic zone, downgradient from the oil body, indicated that the primary reactions in the anoxic zone are oxidation of organic compounds, precipitation of siderite and a ferroan calcite, dissolution of iron oxide and outgassing of CH4 and CO2. The major difference in the two models presented is the ratio of CO2 and CH4 that outgasses. Both models indicate quantitatively that large amounts of Fe are dissolved and reprecipitated as ferrous iron in the anoxic zone of the contaminant plume. ?? 1993.

  19. New data on the Vrancea Nappe (Moldavidian Basin, Outer Carpathian Domain, Romania): paleogeographic and geodynamic reconstructions

    NASA Astrophysics Data System (ADS)

    Amadori, Maria Letizia; Belayouni, Habib; Guerrera, Francesco; Martín-Martín, Manuel; Martin-Rojas, Iván; Miclăuş, Crina; Raffaelli, Giuliana

    2012-09-01

    A study has been performed on the Cretaceous to Early Miocene succession of the Vrancea Nappe (Outer Carpathians, Romania), based on field reconstruction of the stratigraphic record, mineralogical-petrographic and geochemical analyses. Extra-basinal clastic supply and intra-basinal autochthonous deposits have been differentiated, appearing laterally inter-fingered and/or interbedded. The main clastic petrofacies consist of calcarenites, sub-litharenites, quartzarenites, sub-arkoses, and polygenic conglomerates derived from extra-basinal margins. An alternate internal and external provenance of the different supplies is the result of the paleogeographic re-organization of the basin/margins system due to tectonic activation and exhumation of rising areas. The intra-basinal deposits consist of black shales and siliceous sediments (silexites and cherty beds), evidencing major environmental changes in the Moldavidian Basin. Organic-matter-rich black shales were deposited during anoxic episodes related to sediment starvation and high nutrient influx due to paleogeographic isolation of the basin caused by plate drifting. The black shales display relatively high contents in sub-mature to mature, Type II lipidic organic matter (good oil and gas-prone source rocks) constituting a potentially active petroleum system. The intra-basinal siliceous sediments are related to oxic pelagic or hemipelagic environments under tectonic quiescence conditions although its increase in the Oligocene part of the succession can be correlated with volcanic supplies. The integration of all the data in the "progressive reorientation of convergence direction" Carpathian model, and their consideration in the framework of a foreland basin, led to propose some constrains on the paleogeographic-geodynamic evolutionary model of the Moldavidian Basin from the Late Cretaceous to the Burdigalian.

  20. Consequences of artificial deepwater ventilation in the Bornholm Basin for oxygen conditions, cod reproduction and benthic biomass - a model study

    NASA Astrophysics Data System (ADS)

    Stigebrandt, A.; Rosenberg, R.; Råman Vinnå, L.; Ödalen, M.

    2015-01-01

    We develop and use a circulation model to estimate hydrographical and ecological changes in the isolated basin water of the Bornholm Basin. By pumping well-oxygenated so-called winter water to the greatest depth, where it is forced to mix with the resident water, the rate of deepwater density reduction increases as well as the frequency of intrusions of new oxygen-rich deepwater. We show that pumping 1000 m3 s-1 should increase the rates of water exchange and oxygen supply by 2.5 and 3 times, respectively. The CRV (cod reproduction volume), the volume of water in the isolated basin meeting the requirements for successful cod reproduction (S > 11, O2 > 2 mL L-1), should every year be greater than 54 km3, which is an immense improvement, since it has been much less in certain years. Anoxic bottoms should no longer occur in the basin, and hypoxic events will become rare. This should permit extensive colonization of fauna on the earlier periodically anoxic bottoms. Increased biomass of benthic fauna should also mean increased food supply to economically valuable demersal fish like cod and flatfish. In addition, re-oxygenation of the sediments should lead to increased phosphorus retention by the sediments.

  1. Redox Conditions and Microbial Particle Association: A Multi-Year Study in the Cariaco Basin

    NASA Astrophysics Data System (ADS)

    Suter, E.; Pachiadaki, M.; Edgcomb, V. P.; Scranton, M. I.; Taylor, G. T.

    2016-02-01

    Using multiple approaches we have revealed fine-scale complexity in the aggregate association of microbial genes, transcripts, and phylogenetic groups across the redox gradient of the permanently anoxic Cariaco Basin. Spanning 3 years, we examined more than 100 samples from depths between 100 and 1300m. A consistent average of 10% of all microbes were associated with small aggregates (<2.0µm) or organic particles. However, certain biogeochemically relevant processes mediated by microbes (sulfate reduction, sulfur oxidation, denitrification, anammox) had depth-dependent aggregate associations. While certain targeted processes were most common in the upper part of the anoxic portion of the water column, they also occurred in oxic and hypoxic layers. Anaerobic processes that were observed in oxic environments were preferentially associated with aggregates. Thin layers of intruding oxic water into anoxic water also led to the preferential association of these processes with aggregates. RT-qPCR revealed that genes for these anaerobic processes were actively transcribed within the particulate size fraction in both oxic and hypoxic environments. These results widen the conceivable ecological niche of microbial anaerobic processes in the ocean, particularly those associated with nitrogen and sulfur cycling.

  2. An endobiont-bearing allogromiid from the Santa Barbara Basin: Implications for the early diversification of foraminifera

    NASA Astrophysics Data System (ADS)

    Bernhard, Joan M.; Habura, Andrea; Bowser, Samuel S.

    2006-09-01

    Our current understanding of paleoecology and paleoceanography is largely based on the superb Phanerozoic fossil record of foraminiferan protists. The early history of the group is unresolved, however, because basal foraminiferans (allogromiids) are unmineralized and thus fossilize poorly. Molecular-clock studies date foraminiferal origins to the Neoproterozoic, but the deep sea, one of Earth's most extensive habitats and presently hosting a significant fraction of basal foraminiferal diversity, was probably anoxic at that time and, until now, anaerobic allogromiids were unknown. Molecular, cell, and ecological analyses reveal the presence of a previously unknown allogromiid inhabiting anoxic, sulfidic deep-sea sediments (Santa Barbara Basin, California). The fact that the new foraminifer harbors prokaryotic endobionts implicates symbiogenesis as a driving force in early foraminiferal diversification.

  3. In situ Measurement of Pore-Water pH in Anoxic Sediments Using Laser Raman Spectrometry

    NASA Astrophysics Data System (ADS)

    Peltzer, E. T.; Luna, M.; Walz, P. M.; Zhang, X.; Brewer, P. G.

    2010-12-01

    Accurate measurement of the geochemical properties of sediment pore waters is of fundamental importance in ocean geochemistry and microbiology. Recent work has shown that the properties of pore waters can be measured rapidly in situ with a novel Raman based insertion probe (Zhang et al., 2010), and that data obtained from anoxic sediments on in situ dissolved methane concentrations are very different (~30x) than from recovered cores due the large scale degassing that occurs during core recovery (Zhang et al., submitted). Degassing of methane must carry with it via Henry’s Law partioning significant quantities of H2S, which is clearly detectable by smell during sample processing, and thus in situ measurement of H2S is also highly desirable. In practice, dissolved H2S is partitioned between the HS- and H2S species as a function of pH with pKa ~7 for the acid dissociation reaction. Since both species are Raman active full determination of the sulfide system is possible if the relative Raman cross sections are known. The diagenetic equations for these reactions are commonly summarized as: 2CH2O + SO4= ↔ 2HCO3- + H2S CH4 + SO4= ↔ HCO3- + HS- + H2O Three of the major components of these equations, CH4, SO4=, and H2S/HS-, are all observable directly by Raman spectroscopy; but the detection of HCO3- presents a challenge due to its low Raman cross section and thus poor sensitivity. We show that pore water pH, which is a good estimator of HCO3- if total CO2 or alkalinity are known, can be measured by observing the H2S / HS- ratio via the equation: pH = pKa + log([HS-]/[H2S]) thereby fully constraining these equations within a single measurement protocol. The Raman peak for HS- is at 2573 cm-1 and for H2S is at 2592 cm-1; thus the peaks are well separated and may easily be deconvoluted from the observed spectrum. We have determined the relative Raman cross sections by a series of laboratory measurements over a range of pH and by using the definition that when pH = p

  4. Decoupling of carbon isotope records between organic matter and carbonate prior to the Toarcian Oceanic Anoxic Event (Early Jurassic)

    NASA Astrophysics Data System (ADS)

    Bodin, Stephane; Kothe, Tim; Krencker, Francois-Nicolas; Suan, Guillaume; Heimhofer, Ulrich; Immenhauser, Adrian

    2014-05-01

    Across the Pliensbachian-Toarcian boundary (P-To, Early Jurassic), ca. 1 Myr before the Toarcian Oceanic Anoxic Event (T-OAE), an initial negative carbon isotope excursion has been documented in western Tethys sedimentary rocks. In carbonate, its amplitude (2-3 permil) is similar to the subsequent excursion recorded at the onset of the T-OAE. Being also associated with a rapid warming event, the significance of this first carbon isotope shift, in terms of paleoenvironmental interpretation and triggering mechanism, remains however elusive. Taking advantage of expanded and rather continuous sections in the High Atlas of Morocco, several high-resolution, paired organic-inorganic carbon isotope records have been obtained across the Upper Pliensbachian - Lower Toarcian interval. At the onset of the T-OAE, an abrupt 1-2 permil negative shift is recorded in both organic and inorganic phases, succeeded by a relatively longer term 1-2 permil negative trend and a final slow return to pre-excursion conditions. In accordance with previous interpretations, this pattern indicates a perturbation of the entire exogenic carbon isotope reservoir at the onset of the T-OAE by the sudden release of isotopically light carbon into the atmosphere. By contrast, there is no negative shift in carbon isotopes for the P-To event recorded in bulk organic matter of Morocco. Given the strong dominance of terrestrial particles in the bulk organic matter fraction, this absence indicates that massive input of 12C-rich carbon into the atmosphere is not likely to have happened during the P-To event. A pronounced (2 permil) and abrupt negative shift in carbon isotope is however recorded in the bulk carbonate phase. We suggest that this decoupling between organic and inorganic phase is due to changes in the nature of the bulk carbonate phase. Indeed, the negative shift occurs at the lithological transition between Pliensbachian-lowermost Toarcian limestone-marl alternations and the Lower Toarcian marl

  5. Petroleum geology and resources of the West Siberian Basin, Russia

    USGS Publications Warehouse

    Ulmishek, Gregory F.

    2003-01-01

    The West Siberian basin is the largest petroleum basin in the world covering an area of about 2.2 million km2. The basin occupies a swampy plain between the Ural Mountains and the Yenisey River. On the north, the basin extends offshore into the southern Kara Sea. On the west, north, and east, the basin is surrounded by the Ural, Yenisey Ridge, and Turukhan-Igarka foldbelts that experienced major deformations during the Hercynian tectonic event and the Novaya Zemlya foldbelt that was deformed in early Cimmerian (Triassic) time. On the south, the folded Caledonian structures of the Central Kazakhstan and Altay-Sayan regions dip northward beneath the basin?s sedimentary cover. The basin is a relatively undeformed Mesozoic sag that overlies the Hercynian accreted terrane and the Early Triassic rift system. The basement is composed of foldbelts that were deformed in Late Carboniferous?Permian time during collision of the Siberian and Kazakhstan continents with the Russian craton. The basement also includes several microcontinental blocks with a relatively undeformed Paleozoic sedimentary sequence. The sedimentary succession of the basin is composed of Middle Triassic through Tertiary clastic rocks. The lower part of this succession is present only in the northern part of the basin; southward, progressively younger strata onlap the basement, so that in the southern areas the basement is overlain by Toarcian and younger rocks. The important stage in tectono-stratigraphic development of the basin was formation of a deep-water sea in Volgian?early Berriasian time. The sea covered more than one million km2 in the central basin area. Highly organic-rich siliceous shales of the Bazhenov Formation were deposited during this time in anoxic conditions on the sea bottom. Rocks of this formation have generated more than 80 percent of West Siberian oil reserves and probably a substantial part of its gas reserves. The deep-water basin was filled by prograding clastic clinoforms

  6. A basin redox transect at the dawn of animal life

    NASA Astrophysics Data System (ADS)

    Sperling, Erik A.; Halverson, Galen P.; Knoll, Andrew H.; Macdonald, Francis A.; Johnston, David T.

    2013-06-01

    Multiple eukaryotic clades make their first appearance in the fossil record between ~810 and 715 Ma. Molecular clock studies suggest that the origin of animal multicellularity may have been part of this broader eukaryotic radiation. Animals require oxygen to fuel their metabolism, and low oxygen levels have been hypothesized to account for the temporal lag between metazoan origins and the Cambrian radiation of large, ecologically diverse animals. Here, paleoredox conditions were investigated in the Fifteenmile Group, Ogilvie Mountains, Yukon, Canada, which hosts an 811 Ma ash horizon and spans the temporal window that captures the inferred origin and early evolution of animals. Iron-based redox proxies, redox-sensitive trace elements, organic carbon percentages and pyrite sulfur isotopes were analyzed in seven stratigraphic sections along two parallel basin transects. These data suggest that for this basin, oxygenated shelf waters overlay generally anoxic deeper waters. The anoxic water column was dominantly ferruginous, but brief periods of euxinia likely occurred. These oscillations coincide with changes in total organic carbon, suggesting euxinia was primarily driven by increased organic carbon loading. Overall, these data are consistent with proposed quantitative constraints on Proterozoic atmospheric oxygen being greater than 1% of modern levels, but less than present levels. Comparing these oxygen levels against the likely oxygen requirements of the earliest animals, both theoretical considerations and the ecology of modern oxygen-deficient settings suggest that the inferred oxygen levels in the mixed layer would not have been prohibitive to the presence of sponges, eumetazoans or bilaterians. Thus the evolution of the earliest animals was probably not limited by the low absolute oxygen levels that may have characterized Neoproterozoic oceans, although these inferred levels would constrain animals to very small sizes and low metabolic rates.

  7. Vast Peatlands Found in the Congo Basin

    NASA Technical Reports Server (NTRS)

    Fatoyinbo, Lola

    2017-01-01

    Southeast Asias share of Earths tropical peatlands was previously put at 561, but the largest of the tropics peatland complexes might in fact lie elsewhere. On page 86, Dargie et al. combine satellite data with extensive field measurements of peat depth, carbon concentration and radiocarbon dating to produce a map of potential peat extent and carbon stocks in the Cuvette Centrale depression of the central Congo Basin. The authors propose that the Cuvette Centrale represents the worlds largest tropical peatland complex, covering 145,500 square kilometres and possibly storing about 30 petagrams of carbon (1 Pg is 1015 grams) the equivalent of 20 years of current US carbon emissions from fossil fuels. Tropical peatlands have garnered increasing attention in recent years owing to their crucial role as terrestrial organic carbon reserves and the implications of peatland loss for climate change. Thick peat soils (ranging from 30 cm to up to 30 m)3 form in areas where water-logged soils create anoxic conditions that prevent organic materials such as dead leaves and wood from fully decomposing. The largest areas of peat are in temperate regions, but large areas of forested peatlands are also found in the tropics.

  8. Nutrient recycling and the stoichiometric relationship among C, N, and P in Paleozoic anoxic sediments

    NASA Astrophysics Data System (ADS)

    Tuite, M. L., Jr.

    2016-12-01

    Remineralized organic N and P diffused into the water column from underlying anoxic sediments were important sources of macronutrients for primary production in shallow Paleozoic epicontinental seas. Ratios of total organic C to total N or P in ancient sediments that are greater than Redfield-like values are often cited as evidence for macronutrient recycling. We propose that the stoichiometric relationship among C, N, and P in anoxic Paleozoic sediments was mediated primarily by heterotrophic bacterial alkaline phosphatases. Bacterial heterotrophy in organic-rich anaerobic sediments is frequently limited by the availability of labile (low C/N) organic matter. In response, bacterial heterotrophs invest scarce C and N to produce alkaline phosphatases in order to alleviate labile organic matter limitation by hydrolysis of organophosphates. This suggests that sediment organic C/N may represent a threshold beyond which the investment of intracellular C and N in the production of alkaline phosphatase no longer results in a stoichiometrically favorable return on the investment. If this is the case, then C/P likely represents the point in the diagenesis of organic matter at which the effectiveness of alkaline phosphatase in procuring labile organic matter by remineralization of P is constrained by the lability of the organic matter itself. Because alkaline phosphatase activity is expressed in inverse proportion to the porewater concentration of phosphate, at a given distance from the terrestrial source of weathered P, an equilibrium determined by total phosphate influx results in consistent total P burial rates and consistent organic C/N values independent of the total organic content of the sediment. To account for consistent C/N in spite of variable total organic carbon at a given location, we propose that variations in the absolute abundance of organic C in organic-rich Devonian sediments were largely a function of the lipid content of algal primary producers. The

  9. Rapid Oxic/Anoxic Changes in the Sediment-Water Interface During the Eocene- Oligocene Transition

    NASA Astrophysics Data System (ADS)

    Nicholas, C. J.; O'Halloran, A.; Goodhue, R.

    2008-12-01

    The Eocene-Oligocene Transition (EOT) refers to a 500 kyr period of time, which includes the Eocene- Olicgocene Boundary, stretching from 33.5-34.0 Ma (Pearson et al. 2008). It includes all of the changes associated with the expansion of Antarctic glaciation and the concurrent changes in marine fauna and productivity, as well as any physical oceanographic changes that occurred. Shallow-level drilling recovered cores from southern Tanzania and Java, Indonesia. The cores sampled outer-shelf to slope, organic-rich marine clays which show excellent preservation of microfossils and a very low thermal maturity. As the drill sites are from either side of the Indian Ocean, at approximately 10° south of the equator, the comparison of results from these sites will allow insights into the global or regional nature of oceanic signals. Results from the Tanzanian cores have highlighted rapid oscillations in the oxic/anoxic nature of the sediment-water interface throughout the EOT. This is currently interpreted as a direct result of changes occurring in the ocean currents surrounding Antarctica. In the present, Sub-Antarctic Mode Waters (SAMW) deliver high-latitude climatic signals to the tropical Indian Ocean (Dunkley Jones et al., 2008). We suggest that during the EOT these Antarctic currents were in an infantile state, switching on and off during the transitional period, until cooling reached a stable state and the currents were able to fully establish. This could have caused the oxygenation state of the Indian Ocean bottom waters to oscillate during the EOT, only being oxygenated in a stable way after 33.5 Ma. However, the cores from Java will help us verify whether these signals are global or regional in nature. Recent studies have indicated that the heightened productivity of the time is more global than regional, and does not occur just in the high latitudes around Antarctica. Preliminary results from Indonesia indicate that the same increase in productivity was occurring

  10. Paleogene palaeogeography and basin evolution of the Western Carpathians, Northern Pannonian domain and adjoining areas

    NASA Astrophysics Data System (ADS)

    Kováč, Michal; Plašienka, Dušan; Soták, Ján; Vojtko, Rastislav; Oszczypko, Nestor; Less, György; Ćosović, Vlasta; Fügenschuh, Bernhard; Králiková, Silvia

    2016-05-01

    . The Rupelian basins gained a character of semi-closed sea spreading from the Magura Basin across the Central Western Carpathians up to the Hungarian Paleogene Basin. In the Late Oligocene, the Magura Basin connection with the Northern Hungarian Paleogene Basin remained open, probably along the northern edge of the Tisza microplate, and anoxic facies were substituted by open marine environments.

  11. Genetic Diversity of Microbial Eukaryotes in Anoxic Sediment of the Saline Meromictic Lake Namako-ike (Japan): On the Detection of Anaerobic or Anoxic-tolerant Lineages of Eukaryotes.

    PubMed

    Takishita, Kiyotaka; Tsuchiya, Masashi; Kawato, Masaru; Oguri, Kazumasa; Kitazato, Hiroshi; Maruyama, Tadashi

    2007-01-01

    Available sequence data on eukaryotic small-subunit ribosomal DNA (SSU rDNA) directly retrieved from various environments have increased recently, and the diversity of microbial eukaryotes (protists) has been shown to be much greater than previously expected. However, the molecular information accumulated to date does still not thoroughly reveal ecological distribution patterns of microbial eukaryotes. In the ongoing challenge to detect anaerobic or anoxic-tolerant lineages of eukaryotes, we directly extracted DNA from the anoxic sediment of a saline meromictic lake, constructed genetic libraries of PCR-amplified SSU rDNA, and performed phylogenetic analyses with the cloned SSU rDNA sequences. Although a few sequences could not be confidently assigned to any major eukaryotic groups in the analyses and are debatable regarding their taxonomic positions, most sequences obtained have affiliations with known major lineages of eukaryotes (Cercozoa, Alveolata, Stramenopiles, and Opisthokonta). Among these sequences, some branched with lineages predominantly composed of uncultured environmental clones retrieved from other anoxic environments, while others were closely related to those of eukaryotic parasites (e.g. Phytomyxea of Cercozoa, Gregarinea of Alveolata, and Ichthyosporea of Opisthokonta).

  12. Monitoring of anoxic/oxic process for nitrogen and chemical oxygen demand removal using fuzzy neural networks.

    PubMed

    Huang, Mingzhi; Wan, Jinquan; Ma, Yongwen

    2009-07-01

    In this paper, a software sensor based on a fuzzy neural network (FNN) approach was proposed for the real-time estimation of nutrient concentrations and overcoming the problem of delayed measurements. To improve the FNN performance, fuzzy subtractive clustering was used to identify the model's architecture and optimize the fuzzy rule; meanwhile, a split network structure, applied separately for anaerobic and aerobic conditions, was used with dynamic modeling methods, such as an auto-regressive model with exogenous inputs. The proposed methodology was applied to a bench-scale anoxic/oxic process for biological nitrogen removal. It was possible to partially overcome the extrapolation problem of FNNs with the aid of multi-way principal component analysis, because it has the ability to detect abnormal situations, which could generate extrapolation. Real-time estimation of chemical oxygen demand, nitrate, and ammonium concentrations based on the model was successfully carried out with the simple online information of the anoxic/oxic system.

  13. Treatment of petrochemical wastewater by microaerobic hydrolysis and anoxic/oxic processes and analysis of bacterial diversity.

    PubMed

    Yang, Qi; Xiong, Panpan; Ding, Pengyuan; Chu, Libing; Wang, Jianlong

    2015-11-01

    Microaerobic hydrolysis-acidification (MHA)-anoxic-oxic (A/O) processes were developed to treat actual petrochemical wastewater. The results showed that the overall COD removal efficiency was 72-79% at HRT=20h, and MHA accounted for 33-42% of COD removal, exhibiting good efficiency of acidogenic fermentation. Ammonium removal was more than 94%. The main pollutants in the influent were identified to be benzene, ketone, alcohols, amine, nitrile and phenols by GC-MS, and the majority of pollutants could be removed by MHA-A/O treatment. Proteobacteria was the most dominant bacteria in the system, accounting for more than 55% of the reads. The predominant genera in MHA, anoxic and oxic reactors were Anaerolineaceae and Sulfuritalea, Lactococcus and Blastocatella, and Saprospiraceae uncultured and Nitrosomonadaceae, respectively. This treatment system exhibited good performance in degrading the complex compounds in the petrochemical wastewater. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Improving nitrogen removal using a fuzzy neural network-based control system in the anoxic/oxic process.

    PubMed

    Huang, Mingzhi; Ma, Yongwen; Wan, Jinquan; Wang, Yan; Chen, Yangmei; Yoo, Changkyoo

    2014-10-01

    Due to the inherent complexity, uncertainty, and posterity in operating a biological wastewater treatment process, it is difficult to control nitrogen removal in the biological wastewater treatment process. In order to cope with this problem and perform a cost-effective operation, an integrated neural-fuzzy control system including a fuzzy neural network (FNN) predicted model for forecasting the nitrate concentration of the last anoxic zone and a FNN controller were developed to control the nitrate recirculation flow and realize nitrogen removal in an anoxic/oxic (A/O) process. In order to improve the network performance, a self-learning ability embedded in the FNN model was emphasized for improving the rule extraction performance. The results indicate that reasonable forecasting and control performances had been achieved through the developed control system. The effluent COD, TN, and the operation cost were reduced by about 14, 10.5, and 17 %, respectively.

  15. [High abundance of planctomycetes in anoxic layers of a Sphagnum peat bog].

    PubMed

    Ivanova, A O; Dedysh, S N

    2006-01-01

    The depth distribution of planctomycete abundance has been examined in six different sites of the Sphagnum peat bog in Bakchar, Tomsk oblast, Russia. In situ hybridization of peat with the fluorescently labeled oligonucleotide probes PLA46 and PLA886, reported to be group-specific for representatives of the phylum Planctomycetes, revealed two distinct population maxima of these bacteria in all of the profiles examined. The first population maximum was detected in the uppermost, oxic layer of the bog profile, while the second maximum was located at a depth of 30 cm below the water table level. The population sizes of planctomycetes in the uppermost layer and at a depth of 30 cm were of the same order of magnitude and comprised 0.5-1.5 x 10(7) and 0.4-0.7 x 10(7) cells per g of wet peat, respectively. Only 25-30% of the total number of planctomycete cells in the anoxic layer could be detected if the probe PLA886, whose target specificity is restricted to taxonomically characterized aerobic planctomycetes of the genera Gemmata, Planctomyces, Pirellula, and Isosphaera, was used alone. Other planctomycete cells in this layer were detected only with the probe PLA46, which possesses a much wider scope. This suggests the affiliation of these organisms with a yet undescribed phylogenetic subgroup within the Planctomycetes.

  16. Formation of methane and carbon dioxide from dimethylselenide in anoxic sediments and by a methanogenic bacterium

    USGS Publications Warehouse

    Oremland, Ronald S.; Zehr, Jon P.

    1986-01-01

    Anaerobic San Francisco Bay salt marsh sediments rapidly metabolized [14C]dimethylselenide (DMSe) to 14CH4 and 14CO2. Addition of selective inhibitors (2-bromoethanesulfonic acid or molybdate) to these sediments indicated that both methanogenic and sulfate-respiring bacteria could degrade DMSe to gaseous products. However, sediments taken from the selenium-contaminated Kesterson Wildlife Refuge produced only 14CO2 from [14C]DMSe, implying that methanogens were not important in the Kesterson samples. A pure culture of a dimethylsulfide (DMS)-grown methylotrophic methanogen converted [14C]DMSe to 14CH4 and14CO2. However, the organism could not grow on DMSe. Addition of DMS to either sediments or the pure culture retarded the metabolism of DMSe. This effect appeared to be caused by competitive inhibition, thereby indicating a common enzyme system for DMS and DMSe metabolism. DMSe appears to be degraded as part of the DMS pool present in anoxic environments. These results suggest that methylotrophic methanogens may demethylate methylated forms of other metals and metalloids found in nature.

  17. Influence of green waste compost on azimsulfuron dissipation and soil functions under oxic and anoxic conditions.

    PubMed

    García-Jaramillo, M; Cox, L; Hermosín, M C; Cerli, C; Kalbitz, K

    2016-04-15

    Concerns have been raised over the sustainability of intensive rice cultivation, where the use of chemical fertilizers and pesticides has been associated with numerous environmental problems. The objective of this study was to test the effect of the herbicide azimsulfuron on important soil functions as affected by amendment with a byproduct of the olive oil industry. Soil was collected from a Mediterranean rice field. Part of it was amended with alperujo compost (AC). Amended and unamended soils were incubated for 43days in presence or not of azimsulfuron, under anoxic-flooded (AF) and oxic-unflooded (OU) conditions. We monitored the dissipation of the herbicide azimsulfuron, C mineralization, soil microbial biomass (SMB) and dissolved organic carbon (DOC) content and its nature. Under AF conditions, the application of compost produced an increase in the dissipation of the herbicide (up to 12.4%). It was related with the higher DOC content, 4 times higher than under OU conditions. Though increases in carbon turnover (under AF and OU conditions) and reduction of SMBC after herbicide application (only under AF conditions) were observed, the differences were not statistically significant. The application of this organic amendment is presented as an efficient management strategy to increase C turnover in agricultural soils and reduce some of the negative effects derived from the application of azimsulfuron under flooded conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Bacterial ethane formation from reduced, ethylated sulfur compounds in anoxic sediments

    USGS Publications Warehouse

    Oremland, R.S.; Whiticar, Michael J.; Strohmaier, F.E.; Kiene, R.P.

    1988-01-01

    Trace levels of ethane were produced biologically in anoxic sediment slurries from five chemically different aquatic environments. Gases from these locations displayed biogenic characteristics, having 12C-enriched values of ??13CH4 (-62 to -86%.), ??13C2H6 (-35 to -55%.) and high ratios (720 to 140,000) of CH4 [C2H6 + C3H8]. Endogenous production of ethane by slurries was inhibited by autoclaving or by addition of the inhibitor of methanogenic bacteria, 2-bromoethanesulfonic acid (BES). Ethane formation was stimulated markedly by ethanethiol (ESH), and, to a lesser extent, by diethylsulfide (DES). Formation of methane and ethane in ESH- or DES-amended slurries was blocked by BES. Experiments showed that ethionine (or an analogous compound) could be a precursor of ESH. Ethylamine or ethanol additions to slurries caused only a minor stimulation of ethane formation. Similarly, propanethiol additions resulted in only a minor enhancement of propane formation. Cell suspensions of a methyltrophic methanogen produced traces of ethane when incubated in the presence of DES, although the organism did not grow on this compound. These results indicate that methanogenic bacteria produce ethane from the traces of ethylated sulfur compounds present in recent sediments. Preliminary estimates of stable carbon isotope fractionation associated with sediment methane formation from dimethylsulfide was about 40%., while ethane formation from DES and ESH was only 4. 6 and 6.5%., respectively. ?? 1988.

  19. Archaeal and bacterial community structures in the anoxic sediment of Antarctic meromictic lake Nurume-Ike

    NASA Astrophysics Data System (ADS)

    Kurosawa, Norio; Sato, Shota; Kawarabayasi, Yutaka; Imura, Satoshi; Naganuma, Takeshi

    2010-08-01

    Prokaryotic community structures in the anoxic sediment of the Antarctic meromictic Lake Nurume-Ike were revealed by sequence analysis of 16S rRNA gene clones. The archaeal clones obtained (205 total) consisted of only three phylotypes, and were dominantly affiliated with uncultured euryarchaeotes. Specifically, 93% of the clones were identified as marine benthic group-D archaeal phylotype. In contrast to the limited archaeal diversity, 53 phylotypes were detected within 312 bacterial clones. Major bacterial phylotypes were affiliated with α-Proteobacteria (20% of clones), d-Proteobacteria (9%), Planctmycetales (7%), and Cyanobacteria (7%). A small numbers of clones belonging to γ-Proteobacteria, Actinobacteria, Spirochaetes, Flavobacteria, and Verrucomicrobia were also found. A total of 53% of the bacterial clones, consisting of 13 phylotypes, could not be classified into any known group. These results indicated that the bacterial community of Lake Nurume-Ike sediment consisted of numerous phylogenetic groups and had a diversity comparable to the diversity of other Antarctic lakes communities previously reported. Interestingly, however, there were very few phylotypes shared between the communities of lakes Nurume-Ike and five other lakes located in the Vestfold Hills area. This is the first comprehensive study to analyze more than 500 16S rDNA clones for microbial community analysis of an Antarctic lake sediment sample, and the results significantly expand current views of bacterial diversity in Antarctic lakes.

  20. Electricity production and sludge reduction by integrating microbial fuel cells in anoxic-oxic process.

    PubMed

    Xiao, Benyi; Luo, Meng; Wang, Xiao; Li, Zuoxing; Chen, Hong; Liu, Junxin; Guo, Xuesong

    2017-08-01

    To produce energy and reduce sludge production from the treatment of municipal wastewater, four identical microbial fuel cells (MFCs) were constructed in an anoxic-oxic (A/O) process (MFCs-A/O system). Experimental results indicated that this system enhance the removals of chemical oxygen demand (COD) and total nitrogen (TN). The electricity produced by each MFC were ranged from 0.371 to 0.477V (voltage) and from 138 to 227mW/m(3) (power density) at the stable stage, when the external resistance was fixed at 1000Ω. The coulombic efficiency of the MFCs-A/O system ranged from 0.31% to 1.68% (mean=0.72%) at the stable stage, respectively. The removals of COD and TN in the MFCs-A/O system were slightly higher than those in the control system. Compared with the control system, the MFCs-A/O system can reduce waste activated sludge production and sludge yield by 24.0% and 24.2%, respectively. The experimental results indicated that the MFC constructed in A/O system improves wastewater treatment and the MFCs-A/O system can produce electricity while reducing sludge production and increasing wastewater treatment efficiency. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Stable sulfur and oxygen isotope fractionation of anoxic sulfide oxidation by two different enzymatic pathways.

    PubMed

    Poser, Alexander; Vogt, Carsten; Knöller, Kay; Ahlheim, Jörg; Weiss, Holger; Kleinsteuber, Sabine; Richnow, Hans-H

    2014-08-19

    The microbial oxidation of sulfide is a key reaction of the microbial sulfur cycle, recycling sulfur in its most reduced valence state back to more oxidized forms usable as electron acceptors. Under anoxic conditions, nitrate is a preferential electron acceptor for this process. Two enzymatic pathways have been proposed for sulfide oxidation under nitrate reducing conditions, the sulfide:quinone oxidoreductase (SQR) pathway and the Sox (sulfur oxidation) system. In experiments with the model strains Thiobacillus denitrificans and Sulfurimonas denitrificans, both pathways resulted in a similar small sulfur and oxygen isotope fractionation of -2.4 to -3.6‰ for (34)S and -2.4 to -3.4‰ for (18)O. A similar pattern was detected during the oxidation of sulfide in a column percolated with sulfidic, nitrate amended groundwater. In experiments with (18)O-labeled water, a strong oxygen isotope fractionation was observed for T. denitrificans and S. denitrificans, indicating a preferential incorporation of (18)O-depleted oxygen released as water by nitrate reduction to nitrogen. The study indicates that nitrate-dependent sulfide oxidation might be monitored in the environment by analysis of (18)O-depleted sulfate.

  2. Late Jurassic ocean anoxic event: evidence from voluminous sulphide deposition and preservation in the Panthalassa

    PubMed Central

    Nozaki, Tatsuo; Kato, Yasuhiro; Suzuki, Katsuhiko

    2013-01-01

    The historically productive copper-bearing Besshi-type sulphide deposits in the Japanese accretionary complex were formed as volcanogenic massive sulphide deposits on the deep-sea floor of the Panthalassa Ocean. Here we report that eleven typical Besshi-type deposits yielded Re-Os isochron ages around 150 Ma (148.4 ± 1.4 Ma from the composite isochron) in Late Jurassic time. This date coincides with the lowest marine 87Sr/86Sr ratio and highest atmospheric CO2 concentration of the past 300 million years. We infer that intense mid-ocean ridge hydrothermal and volcanic activity in the Late Jurassic produced huge sulphide deposits and large emissions of CO2 gas, leading to global warming and a stratified Panthalassa Ocean with anoxic deep seas that favored preservation of sulphides in the pelagic environment. The emergence of ocean anoxia triggered by seafloor volcanism is also consistent with a positive δ13C excursion and widespread deposition of petroleum source rocks and black shales. PMID:23712471

  3. Textiles wastewater treatment using anoxic filter bed and biological wriggle bed-ozone biological aerated filter.

    PubMed

    Fu, Zhimin; Zhang, Yugao; Wang, Xiaojun

    2011-02-01

    In this study, the performance of the anoxic filter bed and biological wriggle bed-ozone biological aerated filter (AFB-BWB-O(3)-BAF) process treating real textile dyeing wastewater was investigated. After more than 2 month process operation, the average effluent COD concentration of the AFB, BWB, O(3)-BAF were 704.8 mg/L, 294.6 mg/L and 128.8 mg/L, with HRT being 8.1-7.7h, 9.2h and 5.45 h, respectively. Results showed that the effluent COD concentration of the AFB decreased with new carriers added and the average removal COD efficiency was 20.2%. During operation conditions, HRT of the BWB and O(3)-BAF was increased, resulting in a decrease in the effluent COD concentration. However, on increasing the HRT, the COD reduction capability expressed by the unit carrier COD removal loading of the BWB reactor increased, while that of the O(3)-BAF reactor decreased. This study is a beneficial attempt to utilize the AFB-BWB-O(3)-BAF combine process for textile wastewater treatment. Copyright © 2010 Elsevier Ltd. All rights reserved.

  4. Massive dissociation of gas hydrate during a Jurassic oceanic anoxic event

    PubMed

    Hesselbo; Grocke; Jenkyns; Bjerrum; Farrimond; Morgans Bell HS; Green

    2000-07-27

    In the Jurassic period, the Early Toarcian oceanic anoxic event (about 183 million years ago) is associated with exceptionally high rates of organic-carbon burial, high palaeotemperatures and significant mass extinction. Heavy carbon-isotope compositions in rocks and fossils of this age have been linked to the global burial of organic carbon, which is isotopically light. In contrast, examples of light carbon-isotope values from marine organic matter of Early Toarcian age have been explained principally in terms of localized upwelling of bottom water enriched in 12C versus 13C (refs 1,2,5,6). Here, however, we report carbon-isotope analyses of fossil wood which demonstrate that isotopically light carbon dominated all the upper oceanic, biospheric and atmospheric carbon reservoirs, and that this occurred despite the enhanced burial of organic carbon. We propose that--as has been suggested for the Late Palaeocene thermal maximum, some 55 million years ago--the observed patterns were produced by voluminous and extremely rapid release of methane from gas hydrate contained in marine continental-margin sediments.

  5. Seasonal C-13 variations of methane from an anoxic marine sediment

    NASA Technical Reports Server (NTRS)

    Blair, Neal; Desmarais, David S.; Martens, Christopher S.

    1985-01-01

    Recent analyses of glacial ice suggest that the atmospheric concentration of methane has doubled in the last several hundred years, presumably due to anthropogenic perturbations of the relevant biogeochemical cycles. In principal, carbon isotopic measurements of atmospheric methane would provide information concerning changes in the sources and sinks of methane. The isotopic composition of methane is dependent on the source of the methane carbon, the mechanism of methane synthesis, and the degree and mode of oxidation which the methane has experienced. Unfortunately, few carbon isotopic measurements of atmospheric variations have been reported, so conclusions about temporal isotopic variations cannot be made. Also, before isotopic measurements of atmospheric methane can be used to identify changes in methane isotopic composition from different sources must be obtained. Methane bubbles from the anoxic sediments of Cape Lookout Bight, NC exhibit seasonal C-13 variations. The C-13 values ranged from -58 in August to -64 in the winter months with the evolution of the C-13 enriched gas occurring during periods of peak methane production. Even though a few intramolecular C-13 measurements of the pore water acetate have been made (methyl group, -26 per mil; carbonyl, -6 per mil), it is not clear how the acetate fermentation pathway affects the methane C-13/C-12 composition.

  6. Evidence for rapid weathering response to climatic warming during the Toarcian Oceanic Anoxic Event.

    PubMed

    Them, Theodore R; Gill, Benjamin C; Selby, David; Gröcke, Darren R; Friedman, Richard M; Owens, Jeremy D

    2017-07-10

    Chemical weathering consumes atmospheric carbon dioxide through the breakdown of silicate minerals and is thought to stabilize Earth's long-term climate. However, the potential influence of silicate weathering on atmospheric pCO2 levels on geologically short timescales (10(3)-10(5) years) remains poorly constrained. Here we focus on the record of a transient interval of severe climatic warming across the Toarcian Oceanic Anoxic Event or T-OAE from an open ocean sedimentary succession from western North America. Paired osmium isotope data and numerical modelling results suggest that weathering rates may have increased by 215% and potentially up to 530% compared to the pre-event baseline, which would have resulted in the sequestration of significant amounts of atmospheric CO2. This process would have also led to increased delivery of nutrients to the oceans and lakes stimulating bioproductivity and leading to the subsequent development of shallow-water anoxia, the hallmark of the T-OAE. This enhanced bioproductivity and anoxia would have resulted in elevated rates of organic matter burial that would have acted as an additional negative feedback on atmospheric pCO2 levels. Therefore, the enhanced weathering modulated by initially increased pCO2 levels would have operated as both a direct and indirect negative feedback to end the T-OAE.

  7. Late Jurassic ocean anoxic event: evidence from voluminous sulphide deposition and preservation in the Panthalassa.

    PubMed

    Nozaki, Tatsuo; Kato, Yasuhiro; Suzuki, Katsuhiko

    2013-01-01

    The historically productive copper-bearing Besshi-type sulphide deposits in the Japanese accretionary complex were formed as volcanogenic massive sulphide deposits on the deep-sea floor of the Panthalassa Ocean. Here we report that eleven typical Besshi-type deposits yielded Re-Os isochron ages around 150 Ma (148.4 ± 1.4 Ma from the composite isochron) in Late Jurassic time. This date coincides with the lowest marine (87)Sr/(86)Sr ratio and highest atmospheric CO2 concentration of the past 300 million years. We infer that intense mid-ocean ridge hydrothermal and volcanic activity in the Late Jurassic produced huge sulphide deposits and large emissions of CO2 gas, leading to global warming and a stratified Panthalassa Ocean with anoxic deep seas that favored preservation of sulphides in the pelagic environment. The emergence of ocean anoxia triggered by seafloor volcanism is also consistent with a positive δ(13)C excursion and widespread deposition of petroleum source rocks and black shales.

  8. Electricity generation by anaerobic bacteria and anoxic sediments from hypersaline soda lakes

    USGS Publications Warehouse

    Miller, L.G.; Oremland, R.S.

    2008-01-01

    Anaerobic bacteria and anoxic sediments from soda lakes produced electricity in microbial fuel cells (MFCs). No electricity was generated in the absence of bacterial metabolism. Arsenate respiring bacteria isolated from moderately hypersaline Mono Lake (Bacillus selenitireducens), and salt-saturated Searles Lake, CA (strain SLAS-1) oxidized lactate using arsenate as the electron acceptor. However, these cultures grew equally well without added arsenate using the MFC anode as their electron acceptor, and in the process oxidized lactate more efficiently. The decrease in electricity generation by consumption of added alternative electron acceptors (i.e. arsenate) which competed with the anode for available electrons proved to be a useful indicator of microbial activity and hence life in the fuel cells. Shaken sediment slurries from these two lakes also generated electricity, with or without added lactate. Hydrogen added to sediment slurries was consumed but did not stimulate electricity production. Finally, electricity was generated in statically incubated "intact" sediment cores from these lakes. More power was produced in sediment from Mono Lake than from Searles Lake, however microbial fuel cells could detect low levels of metabolism operating under moderate and extreme conditions of salt stress. ?? 2008 US Government.

  9. On the formation of hydrogen gas on copper in anoxic water.

    PubMed

    Johansson, Adam Johannes; Lilja, Christina; Brinck, Tore

    2011-08-28

    Hydrogen gas has been detected in a closed system containing copper and pure anoxic water [P. Szakalos, G. Hultquist, and G. Wikmark, Electrochem. Solid-State Lett. 10, C63 (2007) and G. Hultquist, P. Szakalos, M. Graham, A. Belonoshko, G. Sproule, L. Grasjo, P. Dorogokupets, B. Danilov, T. Aastrup, G. Wikmark, G. Chuah, J. Eriksson, and A. Rosengren, Catal. Lett. 132, 311 (2009)]. Although bulk corrosion into any of the known phases of copper is thermodynamically forbidden, the present paper shows how surface reactions lead to the formation of hydrogen gas in limited amounts. While water cleavage on copper has been reported and investigated before, formation of molecular hydrogen at a single-crystal Cu[100] surface is here explored using density functional theory and transition state theory. It is found that although solvent catalysis seems possible, the fastest route to the formation of molecular hydrogen is the direct combination of hydrogen atoms on the copper surface. The activation free energy (ΔG(s)(‡)(f)) of hydrogen formation in condensed phase is 0.70 eV, which corresponds to a rate constant of 10 s(-1) at 298.15 K, i.e., a relatively rapid process. It is estimated that at least 2.4 ng hydrogen gas could form per cm(2) on a perfect copper surface.

  10. The reorganization of the Golgi complex in anoxic pancreatic acinar cells.

    PubMed

    Merisko, E M; Fletcher, M; Palade, G E

    1986-01-01

    An extensive reorganization of the Golgi complex (GC) was found in the acinar cells of pancreatic lobules incubated in vitro under conditions which inhibited ATP synthesis and thereby blocked the intracellular transport of secretory proteins. After 15-min incubation under N2 or in the presence of 1 mM dinitrophenol (DNP), transitional elements of the endoplasmic reticulum (ER) lost their protrusions, small peripheral Golgi vesicles decreased drastically in number, and fibrillar aggregates approximately 0.2 to 0.5 micron in diameter appeared on the cis side of the stacks of Golgi cisternae. These aggregates often contained vesicle-free, small (approximately 40 nm), globular cages and, occasionally, vesicle-free, clathrin-like cages. Fibrillar aggregates were also observed on the trans side of Golgi stacks. Other changes included the proliferation of GERL-elements ("rigid lamellae") and a striking increase in the population of coated vesicles trans to the Golgi complex and throughout the apical region of the anoxic acinar cells. All changes were found to be reversible provided the cells were incubated for less than 1 h under N2. These observations suggest that the fibrillar elements and the associated cages described in this study may play a role in the vesicular transport of newly synthesized proteins from the ER to the Golgi complex. Further work is needed to explore this possibility.

  11. Microbial community composition of anoxic marine sediments in the Bay of Cádiz (Spain).

    PubMed

    Köchling, Thorsten; Lara-Martín, Pablo; González-Mazo, Eduardo; Amils, Ricardo; Sanz, José Luis

    2011-09-01

    The composition of the microbial community inhabiting the anoxic coastal sediments of the Bay of Cádiz (southern Spain) was investigated using a molecular approach consisting of PCR cloning and denaturing gradient gel electrophoresis (DGGE), based on 16S rRNA sequences. The total cell count was 1-5 × 10⁸ cells/g sediment and, as determined by catalyzed reporter deposition-fluorescent in situ hybridization (CARD-FISH), the proportion of Bacteria to Archaea was about 70:30. The analysis of 16S-rRNA gene sequences revealed a wide spectrum of microorganisms, which could be grouped into 111 operational taxonomic units (OTUs). Many of the OTUs showed high phylogenetic similarity to microorganisms living in marine sediments of diverse geographic origin. The phylogenetic groups that were predominantly detected were Firmicutes, Deltaproteobacteria, and Gammaproteobacteria, accounting for 23, 15, and 14% of the clones, respectively. Diversity in the domain Archaea was significantly lower than in the domain Bacteria. The majority of the archaeal OTUs belonged to the Crenarchaeota phylum. Since most of the sequences could not be identified precisely at the genus/species level, the functional roles of the microorganisms in the ecosystem could not be inferred. However, seven OTUs affiliated with the Delta- and Epsilonproteobacteria were identified down to the genus level, with all of the identified genera known to occur in sulfate-rich marine environments.

  12. Alternate anoxic/aerobic operation for nitrogen removal in a membrane bioreactor for municipal wastewater treatment.

    PubMed

    Guglielmi, G; Andreottola, G

    2011-01-01

    A large pilot-scale membrane bioreactor (MBR) with a conventional denitrification/nitrification scheme for municipal wastewater treatment has been run for one year under two different aeration strategies in the oxidation/nitrification compartment. During the first five months air supply was provided according to the dissolved-oxygen set-point and the system run as a conventional predenitrification MBR; then, an intermittent aeration strategy based on effluent ammonia nitrogen was adopted in the aerobic compartment in order to assess the impact on process performances in terms of N and P removal, energy consumption and sludge reduction. The experimental inferences show a significant improvement of the effluent quality as COD and total nitrogen, both due to a better utilization of the denitrification potential which is a function of the available electron donor (biodegradable COD) and electron acceptor (nitric nitrogen); particularly, nitrogen removal increased from 67% to 75%. At the same time, a more effective biological phosphorus removal was observed as a consequence of better selection of denitrifying phosphorus accumulating organisms (dPAO). The longer duration of anoxic phases also reflected in a lower excess sludge production (12% decrease) compared with the standard pre-denitrification operation and in a decrease of energy consumption for oxygen supply (about 50%).

  13. Oxygen Delivery from Hyperbarically Loaded Microtanks Extends Cell Viability in Anoxic Environments

    PubMed Central

    Cook, Colin A.; Hahn, Kathryn C.; Morrissette-McAlmon, Justin B.F.; Grayson, Warren L.

    2016-01-01

    Oxygen diffusion limitations within nascent tissue engineered (TE) grafts lead to the development of hypoxic regions, cell death, and graft failure. Previous efforts have been made to deliver oxygen within TE scaffolds, including peroxide-doping, perfluorocarbons, and hyperbaric oxygen therapy, to mitigate these effects and help maintain post transplantation cell viability, but these have suffered from significant drawbacks. Here we present a novel approach utilizing polymeric hollow-core microspheres that can be hyperbarically loaded with oxygen and subsequently provide prolonged oxygen delivery. These oxygen carriers are termed, microtanks. With an interest in orthopedic applications, we combined microtanks within polycaprolactone to form solid phase constructs with oxygen delivery capabilities. The mathematical laws governing oxygen delivery from microtank-loaded constructs are developed along with empirical validation. Constructs achieved periods of oxygen delivery out to 6 days, which was shown to prolong the survival of human adipose derived stem cells (hASCs) and human umbilical vein endothelial cells (HUVECs) as well as to enhance their cellular morphology under anoxic conditions. The results of this study suggest the microtank approach may be a feasible means of maintaining cell viability in TE scaffolds during the critical period of vascularization in vivo. PMID:25818444

  14. Massive palmitoylation-dependent endocytosis during reoxygenation of anoxic cardiac muscle

    PubMed Central

    Lin, Mei-Jung; Fine, Michael; Lu, Jui-Yun; Hofmann, Sandra L; Frazier, Gary; Hilgemann, Donald W

    2013-01-01

    In fibroblasts, large Ca transients activate massive endocytosis (MEND) that involves membrane protein palmitoylation subsequent to mitochondrial permeability transition pore (PTP) openings. Here, we characterize this pathway in cardiac muscle. Myocytes with increased expression of the acyl transferase, DHHC5, have decreased Na/K pump activity. In DHHC5-deficient myocytes, Na/K pump activity and surface area/volume ratios are increased, the palmitoylated regulatory protein, phospholemman (PLM), and the cardiac Na/Ca exchanger (NCX1) show greater surface membrane localization, and MEND is inhibited in four protocols. Both electrical and optical methods demonstrate that PTP-dependent MEND occurs during reoxygenation of anoxic hearts. Post-anoxia MEND is ablated in DHHC5-deficient hearts, inhibited by cyclosporine A (CsA) and adenosine, promoted by staurosporine (STS), reduced in hearts lacking PLM, and correlates with impaired post-anoxia contractile function. Thus, the MEND pathway appears to be deleterious in severe oxidative stress but may constitutively contribute to cardiac sarcolemma turnover in dependence on metabolic stress. DOI: http://dx.doi.org/10.7554/eLife.01295.001 PMID:24282237

  15. Simultaneous nitrification and denitrification with anoxic phosphorus uptake in a membrane bioreactor system.

    PubMed

    Patel, Jignesh; Nakhla, George

    2006-10-01

    The performance of an innovative membrane bioreactor (MBR) process using anoxic phosphorus uptake with nitrification and denitrification for the treatment of municipal wastewater with respect to operational performance and effluent quality is addressed in this paper. The system was operated at steady-state conditions with a synthetic acetate-based wastewater at a hydraulic retention time (HRT) of 12 hours and on degritted municipal wastewater at a total system HRT of 6 hours. The MBR system was able to achieve 99% biochemical oxygen demand (BOD), chemical oxygen demand (COD), and ammonia-nitrogen (NH4(+)-N); 98% total Kjeldahl nitrogen (TKN); and 97% phosphorus removal, producing effluent BOD, COD, NH4+-N, TKN, nitrate-nitrogen, nitrite-nitrogen, and phosphate-phosphorus of <3, 14, 0.2, 0.26, 5.8, 0.21, and <0.01 mg/L, respectively, at the 6-hour HRT. The comparison of the synthetic and municipal wastewater run is presented in this paper. Steady-state mass balance on municipal wastewater was performed to reveal some key features of the modified MBR system.

  16. Substrate Uptake and Subcellular Compartmentation of Anoxic Cholesterol Catabolism in Sterolibacterium denitrificans*

    PubMed Central

    Lin, Ching-Wen; Wang, Po-Hsiang; Ismail, Wael; Tsai, Yu-Wen; El Nayal, Ashraf; Yang, Chia-Ying; Yang, Fu-Chun; Wang, Chia-Hsiang; Chiang, Yin-Ru

    2015-01-01

    Cholesterol catabolism by actinobacteria has been extensively studied. In contrast, the uptake and catabolism of cholesterol by Gram-negative species are poorly understood. Here, we investigated microbial cholesterol catabolism at the subcellular level. 13C metabolomic analysis revealed that anaerobically grown Sterolibacterium denitrificans, a β-proteobacterium, adopts an oxygenase-independent pathway to degrade cholesterol. S. denitrificans cells did not produce biosurfactants upon growth on cholesterol and exhibited high cell surface hydrophobicity. Moreover, S. denitrificans did not produce extracellular catabolic enzymes to transform cholesterol. Accordingly, S. denitrificans accessed cholesterol by direction adhesion. Cholesterol is imported through the outer membrane via a putative FadL-like transport system, which is induced by neutral sterols. The outer membrane steroid transporter is able to selectively import various C27 sterols into the periplasm. S. denitrificans spheroplasts exhibited a significantly higher efficiency in cholest-4-en-3-one-26-oic acid uptake than in cholesterol uptake. We separated S. denitrificans proteins into four fractions, namely the outer membrane, periplasm, inner membrane, and cytoplasm, and we observed the individual catabolic reactions within them. Our data indicated that, in the periplasm, various periplasmic and peripheral membrane enzymes transform cholesterol into cholest-4-en-3-one-26-oic acid. The C27 acidic steroid is then transported into the cytoplasm, in which side-chain degradation and the subsequent sterane cleavage occur. This study sheds light into microbial cholesterol metabolism under anoxic conditions. PMID:25418128

  17. Hydrobiogeochemical interactions in 'anoxic' limestone drains for neutralization of acidic mine drainage

    USGS Publications Warehouse

    Robbins, E.I.; Cravotta, C.A.; Savela, C.E.; Nord, G.L.

    1999-01-01

    Processes affecting neutralization of acidic coal mine drainage were evaluated within 'anoxic' limestone drains (ALDs). Influents had pH???3.5 and dissolved oxygen <2 mg/l. Even though effluents were near neutral (pH 6 and alkalinity acidity), two of the four ALDs were failing due to clogging. Mineral-saturation indices indicated the potential for dissolution of calcite and gypsum, and precipitation of Al3+ and Fe3+ compounds. Cleavage mounts of calcite and gypsum that were suspended within the ALDs and later examined microscopically showed dissolution features despite coatings by numerous bacteria, biofilms, and Fe-Al-Si precipitates. In the drain exhibiting the greatest flow reduction, Al-hydroxysulfates had accumulated on limestone surfaces and calcite etch points, thus causing the decline in transmissivity and dissolution. Therefore, where Al loadings are high and flow rates are low, a pre-treatment step is indicated to promote Al removal before diverting acidic mine water into alkalinity-producing materials. ?? 1998 Elsevier Science Ltd.

  18. Bacterial dissimilatory reduction of arsenic(V) to arsenic(III) in anoxic sediments

    USGS Publications Warehouse

    Dowdle, P.R.; Laverman, A.M.; Oremland, R.S.

    1996-01-01

    Incubation of anoxic salt marsh sediment slurries with 10 mM As(V) resulted in the disappearance over time of the As(V) in conjunction with its recovery as As(III). No As(V) reduction to As(III) occurred in heat- sterilized or formalin-killed controls or in live sediments incubated in air. The rate of As(V) reduction in slurries was enhanced by addition of the electron donor lactate, H2, or glucose, whereas the respiratory inhibitor/uncoupler dinitrophenol, rotenone, or 2-heptyl-4-hydroxyquinoline N-oxide blocked As(V) reduction. As(V) reduction was also inhibited by tungstate but not by molybdate, sulfate, or phosphate. Nitrate inhibited As(V) reduction by its action as a preferred respiratory electron acceptor rather than as a structural analog of As(V). Nitrate-respiring sediments could reduce As(V) to As(III) once all the nitrate was removed. Chloramphenicol blocked the reduction of As(V) to As(III) in nitrate- respiring sediments, suggesting that nitrate and arsenate were reduced by separate enzyme systems. Oxidation of [2-14C]acetate to 14CO2 by salt marsh and freshwater sediments was coupled to As(V). Collectively, these results show that reduction of As(V) in sediments proceeds by a dissimilatory process. Bacterial sulfate reduction was completely inhibited by As(V) as well as by As(III).

  19. Contribution of microfiltration on phosphorus removal in the sequencing anoxic/anaerobic membrane bioreactor.

    PubMed

    Cho, Jinwoo; Song, Kyung-Guen; Ahn, Kyu-Hong

    2009-08-01

    This study investigated the contribution of microfiltration to phosphorus removal in the sequencing anoxic/anaerobic membrane bioreactor. The phosphorus content in activated sludge was fractionated by the Schmidt-Thannhauser-Schneider method. The size distribution of phosphorus in the influent was analyzed to estimate the portion of particulate phosphorus rejected physically by the 0.2 mum microfiltration. The result was that along with the high removal of phosphorus (83%) the phosphorus content of activated sludge was measured as 58.66 mgP/gVSS corresponding to 5.87% on dry weight basis. About 9% of total phosphorus was chemically precipitated phosphates while 56% was stored inside the microbial cell by activity of PAOs, and 35% was the sum of minor intracellular compositions and the particulate residuals, which could be rejected completely by the microfiltration. The biological activity is the dominant way of phosphorus removal in the process. However, the microfiltration also contributed significantly to phosphorus removal by retaining the particulate phosphorus inside the system.

  20. Modified aluminosilicates as low-cost sorbents of As(III) from anoxic groundwater.

    PubMed

    Dousová, Barbora; Fuitová, Lucie; Grygar, Tomás; Machovic, Vladimír; Kolousek, David; Herzogová, Lenka; Lhotka, Miloslav

    2009-06-15

    The utilization of low-grade clay materials as selective sorbents represents one of the most effective possibilities of As removal from contaminated water reservoirs. The simple pre-treatment of these materials with Fe (Al, Mn) salts can significantly improve their sorption affinity to As oxyanions. The natural kaolin calcined at 550 degrees C (mostly metakaolin) and raw bentonite (mostly montmorillonite) pre-treated with Fe(II), Fe(III), Al(III) and Mn(II) salts were used to remove of As from the model anoxic groundwater with As(III) concentration about 0.5 and 10 mg L(-1). All the pre-treating methods were appropriate for bentonite; the efficiency of As(III) sorption varied from 92 to >99%, by the sorption capacity higher than 4.5 mg g(-1). In the case of metakaolin, Fe(II)- and Mn(II)-treatments proved the high sorption efficiency (>97%), while only <50% of As was removed after Fe(III) and Al(III) pre-treatment. The sorption capacities of treated metakaolin ranged from 0.1 to 2.0 mg g(-1).

  1. Impact of Bioreduction on Remobilization of Adsorbed Cadmium on Iron Minerals in Anoxic Condition.

    PubMed

    Ghorbanzadeh, Nasrin; Lakzian, Amir; Halajnia, Akram; Choi, Ui-Kyu; Kim, Ki-Hyun; Kim, Jong-Oh; Kurade, Mayur; Jeon, Byong-Hun

    2017-06-01

      The impact of bioreduction on the remobilization of adsorbed cadmium Cd(II) on minerals, including hematite, goethite, and two iron(III)-rich clay minerals nontronites (NAU-1 and NAU-2) under anoxic conditions was investigated. Langmuir isotherm equation better described the sorption of Cd(II) onto the all minerals. The maximum adsorption capacity was 6.2, 18.1, 3.6, and 4 mg g-1 for hematite, goethite, NAU-1 and NAU-2, respectively. The desorption of Cd(II) was due to the production of Fe(II) as a result of bioreduction of structural Fe(III) in the minerals by Shewanella putrefaciens. The bioreduction of Cd(II)-loaded Fe(III) minerals was negligible during the initial 5 days followed by a rapid increase up to 20 days. The amount of Cd(II) in solution phase at the end of 30 days increased up to 0.07 mmol L-1 for hematite, NAU-1, and NAU-2 and 0.02 mmol L-1 for goethite. The X-ray diffraction study showed negligible changes in bioreduced minerals phases.

  2. Simultaneous removal of phenol and nitrate in an anoxic fluidized bed reactor.

    PubMed

    Omena, Sylvia P F; Sader, Leandro T; Silva, Edson L

    2013-01-01

    The general purpose of this study was to characterize a biological treatment system for phenol removal in an anoxic fluidized bed reactor (AFBR) that employed nitrate as the final electron acceptor. The average influent phenol concentrations in the study were 52, 107, 201, 335, and 518 mg/L so that phenol was not detected in the effluent for influent concentrations up to 335 mg/L. The removal efficiency dropped to 70% when the AFBR was operated with influent phenol concentrations above 500 mg/L. The ratio of carbon (derived solely from phenol) to nitrate (N-NO(3)) was approximately 1. Hence, the average influent N-NO(3) concentrations in the study were 45, 79, 157, 260, and 362 mg/L, with corresponding nitrogen removal efficiencies of 94%, 89%, 86%, 79%, and 51%. Nitrite accumulation was not observed because the average effluent N-NO(3) concentration during the entire reactor operation period was 1.5 mg/L.

  3. Dephosphorylation of Ezrin as an Early Event in Renal Microvillar Breakdown and Anoxic Injury

    NASA Astrophysics Data System (ADS)

    Chen, Jing; Cohn, Jonathan A.; Mandel, Lazaro J.

    1995-08-01

    Disruption of the renal proximal tubule (PT) brush border is a prominent early event during ischemic injury to the kidney. The molecular basis for this event is unknown. Within the brush border, ezrin may normally link the cytoskeleton to the cell plasma membrane. Anoxia causes ezrin to dissociate from the cytoskeleton and also causes many cell proteins to become dephosphorylated in renal PTs. This study examines the hypothesis that ezrin dephosphorylation accompanies and may mediate the anoxic disruption of the rabbit renal PT. During normoxia, 73 ±. 3% of the cytoskeleton-associated (Triton-insoluble) ezrin was phosphorylated, but 88 ± 6% of dissociated (Triton-soluble) ezrin was dephosphorylated. Phosphorylation was on serine/threonine residues, since ezrin was not detectable by an antibody against phosphotyrosine. After 60 min of anoxia, phosphorylation of total intracellular ezrin significantly decreased from 72 ± 2% to 21 ± 9%, and ezrin association with the cytoskeleton decreased from 91 ± 2% to 58 ± 2%. Calyculin A (1 μM), the serine/threonine phosphatase inhibitor, inhibited the dephosphorylation of ezrin during anoxia by 57% and also blocked the dissociation of ezrin from the cytoskeleton by 53%. Our results demonstrate that (i) the association of ezrin with the renal microvillar cytoskeleton is correlated with phosphorylation of ezrin serine/threonine residues and (ii) anoxia may cause disruption of the renal brush border by dephosphorylating ezrin and thereby dissociating the brush border membrane from the cytoskeleton.

  4. Counting clonogenic assays from normoxic and anoxic irradiation experiments manually or by using densitometric software.

    PubMed

    Wouters, An; Pauwels, Bea; Lambrechts, Hilde A J; Pattyn, Greet G O; Ides, Johan; Baay, Marc; Meijnders, Paul; Lardon, Filip; Vermorken, Jan B

    2010-04-07

    The clonogenic assay is the method of choice to determine cell reproductive death after in vitro irradiation treatment. Traditionally, colony quantification has been performed by manual counting, a very laborious, time-consuming and rather subjective task. In this study, we compared manual counting by two skilled investigators with automated counting using the freely available ClonoCounter program. Five human tumour cell lines were irradiated under normoxia (21% O(2)) or anoxia (<0.1% O(2)), after 24 h or 6 h anoxic preincubation. Colonies were quantified manually or using the ClonoCounter software. A positive correlation between the absolute number of colonies counted manually and automatically was shown. Though there was a general trend of underpredicting the absolute number of cell colonies when counting automatically, survival curves were very similar, and in none of the cell lines were significant differences in radiobiological parameters such as mean inactivation dose, surviving fraction at 2 Gy and oxygen enhancement ratio detected. Our results suggest that the ClonoCounter provides sufficient reliability to be implemented for counting human tumour colonies in in vitro irradiation experiments. In contrast to several previously reported computer-aided colony-counting methods, it is a freely available program, requiring only minimal instrument costs.

  5. Dissolved organic matter in anoxic pore waters from Mangrove Lake, Bermuda

    USGS Publications Warehouse

    Orem, W.H.; Hatcher, P.G.; Spiker, E. C.; Szeverenyi, N.M.; Maciel, G.E.

    1986-01-01

    Dissolved organic matter and dissolved inorganic chemical species in anoxic pore water from Mangrove Lake, Bermuda sediments were studied to evaluate the role of pore water in the early diagenesis of organic matter. Dissolved sulphate, titration alkalinity, phosphate, and ammonia concentration versus depth profiles were typical of many nearshore clastic sediments and indicated sulphate reduction in the upper 100 cm of sediment. The dissolved organic matter in the pore water was made up predominantly of large molecules, was concentrated from large quantities of pore water by using ultrafiltration and was extensively tudied by using elemental and stable carbon isotope analysis and high-resolution, solid state 13C nuclear magnetic resonance and infrared spectroscopy. The results indicate that this material has a predominantly polysaccharide-like structure and in addition contains a large amount of oxygen-containing functional groups (e.g., carboxyl groups). The 13C nulcear magnetic resonance spectra of the high-molecular-weight dissolved organic matter resemble those of the organic matter in the surface sediments of Mangrove Lake. We propose that this high-molecular-weight organic matter in pore waters represents the partially degraded, labile organic components of the sedimentary organic matter and that pore waters serve as a conduit for removal of these labile organic components from the sediments. The more refractory components are, thus, selectively preserved in the sediments as humic substances (primarily humin). ?? 1986.

  6. Modeling simultaneous carbon and nitrogen removal (SCNR) in anaerobic/anoxic reactor treating domestic wastewater.

    PubMed

    Mendes, Carlos; Esquerre, Karla; Queiroz, Luciano Matos

    2016-07-15

    This paper presents a mathematical model based on the Anaerobic Digestion Model No. 1 (ADM1) to simulate the effects of nitrate concentration and hydraulic retention time (HRT) on the simultaneous carbon and nitrogen removal (SCNR) in anaerobic/anoxic reactor treating domestic wastewater. The model was calibrated using previously published experimental data obtained from anaerobic batch tests for different COD/ [Formula: see text] ratios. Model simulations were performed to predict the SCNR in a completely mixed reactor (CSTR) operating under mesophilic conditions (35 °C). Six different scenarios were evaluated to investigate the performance of the SCNR based on typical influent characteristics of domestic wastewater. The variables analyzed were chemical oxygen demand (COD) removal, nitrate concentration, methane production, nitrogen gas, volatile fatty acids (VFA) concentration, pH and percentage of COD used by the denitrifying and methanogenic microorganisms. The HRT was decreased stepwise from 15 to 4 h. The results indicate that Scenario (S5) with a COD/ [Formula: see text] ratio equal to 10 and an HRT equal to 15 h ensures the occurrence of the stable SCNR. Furthermore, the accumulation of denitrification intermediates and a significant reduction in the biogas production when the organic matter is limited was verified. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Climate cooling at the onset of the early Aptian Oceanic Anoxic Event (OAE1a)

    NASA Astrophysics Data System (ADS)

    Kuhnt, W.; Floegel, S.; Holbourn, A. E.; Moullade, M.; Lorenzen, J.

    2009-12-01

    We present millennial-scale resolution stable isotope data from a marly subtropical shelf succession (La Bédoule, SE France) with minimal diagenetic overprint, which track the onset of Oceanic Anoxic Event 1a (OAE1a). Our 2 kyr-resolution δ13C record is characterized by a continuous succession of stepwise increases (overall amplitude: >2‰). In contrast, the δ18O record exhibits orbital periodicities corresponding to short eccentricity, obliquity and precession, and reveals a prominent cooling event within the initial positive δ13C shift of OAE1a. This cooling event bears similarity to glacio-eustatic sealevel falls and cooling events in the early phase of major carbon isotope shifts in the middle Cenomanian, late Cenomanian and middle Miocene. Using climate simulations with the coupled global climate model GENESIS v.3.0, we test the hypothesis that these events are related to ice-sheet buildup in Antarctica in the initial phase of positive δ13C excursions. We explore the physical potential of snow accumulation and ice-buildup in Antarctica under middle Cretaceous boundary conditions and various elevated atmospheric CO2 concentrations and changing orbital configurations (eccentricity). We suggest that snow/ice accumulation occurred during eccentricity minima, mainly due to a strong albedo feedback, when pCO2 and elevation allowed a perennial snow cover.

  8. Uranium(VI) Reduction by Nanoscale Zerovalent Iron in Anoxic Batch Systems

    SciTech Connect

    Yan, Sen; Hua, Bin; Bao, Zhengyu; Yang, John; Liu, Chongxuan; Deng, Baolin

    2010-11-17

    This study investigated the influences of pH, bicarbonate, and calcium on U(VI) adsorption and reduction by synthetic nanosize zero valent iron (nano Fe0) particles under an anoxic condition. The results showed that about 87.1%, 82.7% and 78.3% of U(VI) could be reduced within 96 hours in the presence of 10 mM bicarbonate at pHs 6.92, 8.03 and 9.03, respectively. The rates of U(VI) reduction and adsorption by nano Fe0, however, varied significantly with increasing pH and concentrations of bicarbonate and/or calcium. Solid phase analysis by X-ray photoelectron spectroscopy confirmed the formation of UO2 and iron (hydr)oxides as a result of the redox interactions between adsorbed U(VI) and nano Fe0. This study highlights the potential important role of groundwater chemical composition in controlling the rates of U(VI) reductive immobilization using nano Fe0 in subsurface environments.

  9. Effect of a Jurassic oceanic anoxic event on belemnite ecology and evolution.

    PubMed

    Ullmann, Clemens Vinzenz; Thibault, Nicolas; Ruhl, Micha; Hesselbo, Stephen P; Korte, Christoph

    2014-07-15

    The Toarcian oceanic anoxic event (T-OAE; ∼ 183 million y ago) is possibly the most extreme episode of widespread ocean oxygen deficiency in the Phanerozoic, coinciding with rapid atmospheric pCO2 increase and significant loss of biodiversity in marine faunas. The event is a unique past tipping point in the Earth system, where rapid and massive release of isotopically light carbon led to a major perturbation in the global carbon cycle as recorded in organic and inorganic C isotope records. Modern marine ecosystems are projected to experience major loss in biodiversity in response to enhanced ocean anoxia driven by anthropogenic release of greenhouse gases. Potential consequences of this anthropogenic forcing can be approximated by studying analog environmental perturbations in the past such as the T-OAE. Here we present to our knowledge the first organic carbon isotope record derived from the organic matrix in the calcite rostra of early Toarcian belemnites. We combine both organic and calcite carbon isotope analyses of individual specimens of these marine predators to obtain a refined reconstruction of the early Toarcian global exogenic carbon cycle perturbation and belemnite paleoecology. The organic carbon isotope data combined with measurements of oxygen isotope values from the same specimens allow for a more robust interpretation of the interplay between the global carbon cycle perturbation, environmental change, and biotic response during the T-OAE. We infer that belemnites adapted to environmental change by shifting their habitat from cold bottom waters to warm surface waters in response to expanded seafloor anoxia.

  10. Carbonate platform evidence of ocean acidification at the onset of the early Toarcian oceanic anoxic event

    NASA Astrophysics Data System (ADS)

    Trecalli, Alberto; Spangenberg, Jorge; Adatte, Thierry; Föllmi, Karl B.; Parente, Mariano

    2012-12-01

    The early Toarcian oceanic anoxic event (Early Jurassic;˜183 Myr ago) is associated with one of the largest negative carbon isotope excursion (CIE) in the whole Phanerozoic (3-7‰). Estimates of the magnitude and rate of CO2 injection in the ocean-atmosphere system are compatible with a scenario of ocean acidification. Many carbonate platforms drowned in the Pliensbachian, well before the early Toarcian event. In this paper we test the hypothesis of surface water ocean acidification by presenting data from a resilient carbonate platform: the Apennine Carbonate Platform of southern Italy. The studied sections document a dramatic shift of the carbonate factory from massive biocalcification to chemical precipitation. Lithiotis bivalves and calcareous algae (Palaeodasycladus mediterraneus), which were the most prolific carbonate producers of Pliensbachian carbonate platforms, disappear during the first phase of the early Toarcian CIE, before the most depleted values are reached. We discuss the local versus supraregional significance of this shift and propose a scenario involving abrupt decline of carbonate saturation, forced by CO2 release at the beginning of the early Toarcian CIE, followed by a calcification overshoot, driven by the recovery of ocean alkalinity. Attribution of the demise of carbonate platform hypercalcifiers to ocean acidification is supported by palaeophysiology and reinforced by experimental data on the detrimental effects of ocean acidification on recent shellfishes and calcareous algae.

  11. Anoxic oscillating MBR for photosynthetic bacteria harvesting and high salinity wastewater treatment.

    PubMed

    Qin, Lei; Liu, Qiuhua; Meng, Qin; Fan, Zheng; He, Jinzhe; Liu, Tao; Shen, Chong; Zhang, Guoliang

    2017-01-01

    In this study, photosynthetic bacteria (PSB) were first harvested by MBR with pendulum type oscillation (PTO) hollow fiber module in succession and on a large scale. Based on unique properties of PSB, PSB/MBR was successfully applied for high-salinity wastewater treatment. Compared with control PSB-MBR (CMBR), PSB/PTO-MBR exhibited more excellent organics removal, which was mainly attributed to much higher biomass production for utilization. Meanwhile, the influence of light irradiation and aeration on activity of PSB was investigated in detail. Results showed that PTO-MBR with 12h light irradiation proved to be a promising and economical alternative. The cycle of dark/light and anoxic had a positive effect on PSB cultivating. Moreover, PTO-MBR exhibited much higher flux than CMBR even if large amounts of biomass existed, which demonstrated that the strong shear stress on interface of liquid-membrane played important roles on membrane fouling reduction. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Increased Intracranial Pressure during Hemodialysis in a Patient with Anoxic Brain Injury

    PubMed Central

    Damholt, Mette B.; Strange, Ditte G.; Kelsen, Jesper; Møller-Sørensen, Hasse; Møller, Kirsten

    2017-01-01

    Dialysis disequilibrium syndrome (DDS) is a serious neurological complication of hemodialysis, and patients with acute brain injury are at increased risk. We report a case of DDS leading to intracranial hypertension in a patient with anoxic brain injury and discuss the subsequent dialysis strategy. A 13-year-old girl was admitted after prolonged resuscitation from cardiac arrest. Computed tomography (CT) revealed an inferior vena cava aneurysm and multiple pulmonary emboli as the likely cause. An intracranial pressure (ICP) monitor was inserted, and, on day 3, continuous renal replacement therapy (CRRT) was initiated due to acute kidney injury, during which the patient developed severe intracranial hypertension. CT of the brain showed diffuse cerebral edema. CRRT was discontinued, sedation was increased, and hypertonic saline was administered, upon which ICP normalized. Due to persistent hyperkalemia and overhydration, ultrafiltration and intermittent hemodialysis were performed separately on day 4 with a small dialyzer, low blood and dialysate flow, and high dialysate sodium content. During subsequent treatments, isolated ultrafiltration was well tolerated, whereas hemodialysis was associated with increased ICP necessitating frequent pauses or early cessation of dialysis. In patients at risk of DDS, hemodialysis should be performed with utmost care and continuous monitoring of ICP should be considered. PMID:28409034

  13. Syntrophic growth on formate: a new microbial niche in anoxic environments.

    PubMed

    Dolfing, Jan; Jiang, Bo; Henstra, Anne M; Stams, Alfons J M; Plugge, Caroline M

    2008-10-01

    Anaerobic syntrophic associations of fermentative bacteria and methanogenic archaea operate at the thermodynamic limits of life. The interspecies transfer of electrons from formate or hydrogen as a substrate for the methanogens is key. Contrary requirements of syntrophs and methanogens for growth-sustaining product and substrate concentrations keep the formate and hydrogen concentrations low and within a narrow range. Since formate is a direct substrate for methanogens, a niche for microorganisms that grow by the conversion of formate to hydrogen plus bicarbonate--or vice versa--may seem unlikely. Here we report experimental evidence for growth on formate by syntrophic communities of (i) Moorella sp. strain AMP in coculture with a thermophilic hydrogen-consuming Methanothermobacter species and of (ii) Desulfovibrio sp. strain G11 in coculture with a mesophilic hydrogen consumer, Methanobrevibacter arboriphilus AZ. In pure culture, neither Moorella sp. strain AMP, nor Desulfovibrio sp. strain G11, nor the methanogens grow on formate alone. These results imply the existence of a previously unrecognized microbial niche in anoxic environments.

  14. Knowledge about post-anoxic somatosensory evoked potentials--present or not?

    PubMed

    Jaeger, B; Bouwes, A; Binnekade, J M; Hilgevoord, A A; Horn, J; van Rootselaar, A-F

    2014-06-01

    Median nerve somatosensory evoked potential (SEP) recordings play an important role in outcome algorithms in comatose patients after cardiopulmonary resuscitation. Knowledge of technical difficulties, clinical implications and uniform interpretation of SEP recordings is crucial. The aim of this study was to evaluate the skills of neurologists to interpret SEP recordings in post-anoxic patients. Nationwide Dutch clinical neurophysiology examinations from 2007, 2008 and 2011, containing SEP related questions, were analysed. Participants were classified as neurology residents, neurologists with less than 10 years of experience, neurologists with more than 10 years of experience and clinical neurophysiologists. End-points were the knowledge of all participants about SEP recordings per year as well as improvement in knowledge over the years, as reflected by the test scores. A total of 194 participants completed the examination in 2007, 200 in 2008 and 263 in 2011. Between 2007 and 2008, all groups of respondents showed a significant increase in percentage of correct answers to SEP questions. Sixty-six participants completed all three examinations. The SEP score of this group improved in 2008 [75%, interquartile range (IQR) 50-75, P < 0.001] compared with 2007 (38%, IQR 38-50); there was no further improvement in 2011 (69%, IQR 54-77). Continuing education about technical knowledge, possible pitfalls and interpretation of SEP recordings remains of utmost importance. © 2014 The Author(s) European Journal of Neurology © 2014 EAN.

  15. Effect of substrate availability on nitrous oxide production by deammonification processes under anoxic conditions

    PubMed Central

    Schneider, Yvonne; Beier, Maike; Rosenwinkel, Karl‐Heinz

    2012-01-01

    Summary Due to its high global warming potential, nitrous oxide (N2O) emissions from wastewater treatment processes have recently received a high degree of attention. Nevertheless, there is still a lack of information regarding the microbiological processes leading to N2O production. In this study, two lab‐scale sequencing batch reactors were operated with deammonification biomass to investigate the role of denitrification and the influence of substrate availability regarding N2O formation during the anoxic phase of deammonification. Three different operational phases were established: within the first phase conversion by anammox was favoured and after a transition phase, denitrification activity was promoted. Low nitrous oxide production was observed during stable operation aiming for anammox conversion. Pulsed inflow of the wastewater containing ammonium (NH4+) and nitrite (NO2‐) led to increased N2O production rates. Within the period of denitrification as dominating nitrogen conversion process, the nitrous oxide concentration level was higher during continuous inflow conditions, but the reaction to