Evidence for habitat-driven segregation of an estuarine fish assemblage.

PubMed

Loureiro, S N; Reis-Filho, J A; Giarrizzo, T

2016-07-01

This study examined the spatio-temporal variability in fish assemblage structure and composition following monthly sampling (August 2006 to July 2007). Three estuarine zones (upper, middle and lower) of the unvegetated intertidal and subtidal channel habitats located in the Marapanim Estuary were investigated. In each of these zones, salinity, organic matter and sediment types were measured to assess any correlation between habitat types and the fish fauna. A total of 41 496 fishes, belonging to 76 species and 29 families, was recorded. Recurring changes in both species composition and trophic structure were attributed to seasonal variations, while habitat type played a more permanent role in modifying the structure of fish assemblages. Zooplanktivores (e.g. Lycengraulis grossidens) and herbivores (e.g. Cetengraulis edentulus) used the intertidal habitat almost exclusively and were associated with salinity and substratum composition (gravel, silt and mud). In contrast, benthophages (e.g. Cathorops spixii) and benthophage-ichthyophages (e.g. Cynoscion leiarchus) were primarily associated with the subtidal habitat throughout the estuary and were highly related to the presence of sandy substrata. This study highlighted the intricate roles that local factors (such as habitat connectivity) may have on the distribution of fishes at the assemblage level. As such, incorporating habitat sharing or segregation between species should be viewed as essential for any comparisons of estuaries over large geographic scales, and in particular for conservation planning and management measures. © 2016 The Fisheries Society of the British Isles.

Increased sediment load during a large-scale dam removal changes nearshore subtidal communities

PubMed Central

Foley, Melissa M.; Berry, Helen D.; Duda, Jeffrey J.; Hudson, Benjamin; Elder, Nancy E.; Beirne, Matthew M.; Warrick, Jonathan A.; McHenry, Michael L.; Stevens, Andrew W.; Eidam, Emily F.; Ogston, Andrea S.; Gelfenbaum, Guy; Pedersen, Rob

2017-01-01

The coastal marine ecosystem near the Elwha River was altered by a massive sediment influx—over 10 million tonnes—during the staged three-year removal of two hydropower dams. We used time series of bathymetry, substrate grain size, remotely sensed turbidity, scuba dive surveys, and towed video observations collected before and during dam removal to assess responses of the nearshore subtidal community (3 m to 17 m depth). Biological changes were primarily driven by sediment deposition and elevated suspended sediment concentrations. Macroalgae, predominantly kelp and foliose red algae, were abundant before dam removal with combined cover levels greater than 50%. Where persistent sediment deposits formed, macroalgae decreased greatly or were eliminated. In areas lacking deposition, macroalgae cover decreased inversely to suspended sediment concentration, suggesting impacts from light reduction or scour. Densities of most invertebrate and fish taxa decreased in areas with persistent sediment deposition; however, bivalve densities increased where mud deposited over sand, and flatfish and Pacific sand lance densities increased where sand deposited over gravel. In areas without sediment deposition, most invertebrate and fish taxa were unaffected by increased suspended sediment or the loss of algae cover associated with it; however, densities of tubeworms and flatfish, and primary cover of sessile invertebrates increased suggesting benefits of increased particulate matter or relaxed competition with macroalgae for space. As dam removal neared completion, we saw evidence of macroalgal recovery that likely owed to water column clearing, indicating that long-term recovery from dam removal effects may be starting. Our results are relevant to future dam removal projects in coastal areas and more generally to understanding effects of increased sedimentation on nearshore subtidal benthic communities. PMID:29220368

Increased sediment load during a large-scale dam removal changes nearshore subtidal communities.

PubMed

Rubin, Stephen P; Miller, Ian M; Foley, Melissa M; Berry, Helen D; Duda, Jeffrey J; Hudson, Benjamin; Elder, Nancy E; Beirne, Matthew M; Warrick, Jonathan A; McHenry, Michael L; Stevens, Andrew W; Eidam, Emily F; Ogston, Andrea S; Gelfenbaum, Guy; Pedersen, Rob

2017-01-01

The coastal marine ecosystem near the Elwha River was altered by a massive sediment influx-over 10 million tonnes-during the staged three-year removal of two hydropower dams. We used time series of bathymetry, substrate grain size, remotely sensed turbidity, scuba dive surveys, and towed video observations collected before and during dam removal to assess responses of the nearshore subtidal community (3 m to 17 m depth). Biological changes were primarily driven by sediment deposition and elevated suspended sediment concentrations. Macroalgae, predominantly kelp and foliose red algae, were abundant before dam removal with combined cover levels greater than 50%. Where persistent sediment deposits formed, macroalgae decreased greatly or were eliminated. In areas lacking deposition, macroalgae cover decreased inversely to suspended sediment concentration, suggesting impacts from light reduction or scour. Densities of most invertebrate and fish taxa decreased in areas with persistent sediment deposition; however, bivalve densities increased where mud deposited over sand, and flatfish and Pacific sand lance densities increased where sand deposited over gravel. In areas without sediment deposition, most invertebrate and fish taxa were unaffected by increased suspended sediment or the loss of algae cover associated with it; however, densities of tubeworms and flatfish, and primary cover of sessile invertebrates increased suggesting benefits of increased particulate matter or relaxed competition with macroalgae for space. As dam removal neared completion, we saw evidence of macroalgal recovery that likely owed to water column clearing, indicating that long-term recovery from dam removal effects may be starting. Our results are relevant to future dam removal projects in coastal areas and more generally to understanding effects of increased sedimentation on nearshore subtidal benthic communities.

Increased sediment load during a large-scale dam removal changes nearshore subtidal communities

USGS Publications Warehouse

Rubin, Stephen P.; Miller, Ian M.; Foley, Melissa M.; Berry, Helen D.; Duda, Jeffrey J.; Hudson, Benjamin; Elder, Nancy E.; Beirne, Matthew M.; Warrick, Jonathan; McHenry, Michael L.; Stevens, Andrew; Eidam, Emily; Ogston, Andrea; Gelfenbaum, Guy R.; Pedersen, Rob

2017-01-01

The coastal marine ecosystem near the Elwha River was altered by a massive sediment influx—over 10 million tonnes—during the staged three-year removal of two hydropower dams. We used time series of bathymetry, substrate grain size, remotely sensed turbidity, scuba dive surveys, and towed video observations collected before and during dam removal to assess responses of the nearshore subtidal community (3 m to 17 m depth). Biological changes were primarily driven by sediment deposition and elevated suspended sediment concentrations. Macroalgae, predominantly kelp and foliose red algae, were abundant before dam removal with combined cover levels greater than 50%. Where persistent sediment deposits formed, macroalgae decreased greatly or were eliminated. In areas lacking deposition, macroalgae cover decreased inversely to suspended sediment concentration, suggesting impacts from light reduction or scour. Densities of most invertebrate and fish taxa decreased in areas with persistent sediment deposition; however, bivalve densities increased where mud deposited over sand, and flatfish and Pacific sand lance densities increased where sand deposited over gravel. In areas without sediment deposition, most invertebrate and fish taxa were unaffected by increased suspended sediment or the loss of algae cover associated with it; however, densities of tubeworms and flatfish, and primary cover of sessile invertebrates increased suggesting benefits of increased particulate matter or relaxed competition with macroalgae for space. As dam removal neared completion, we saw evidence of macroalgal recovery that likely owed to water column clearing, indicating that long-term recovery from dam removal effects may be starting. Our results are relevant to future dam removal projects in coastal areas and more generally to understanding effects of increased sedimentation on nearshore subtidal benthic communities.

Macrobenthic diversity and sediment-water exchanges of oxygen and ammonium: Example of two subtidal communities of the eastern English Channel

NASA Astrophysics Data System (ADS)

Tous Rius, Armonie; Denis, Lionel; Dauvin, Jean-Claude; Spilmont, Nicolas

2018-06-01

In organic-rich shallow habitats, benthic macrofauna is known to play a major role in the geochemical functioning of surficial sediments through its metabolism, as well as its bioirrigation and/or bioturbation activity. In this paper, the effects of benthic macrofauna on metabolic fluxes at the sediment-water interface were studied at four dates, from winter to late summer, on two major macrobenthic communities of the eastern English Channel (macrotidal system): the fine sand Abra alba community (2 stations) and the sandy gravel Ophiothrix fragilis community (1 station). Oxygen and ammonium fluxes showed temporal changes that could be attributed to the variation of sea water temperature. Once the effect of temperature removed (using Q10 = 2.5), the average fauna mediated fluxes (FFauna) represented respectively 77% and 76% of average total fluxes. Considering the whole dataset, species number and biomass showed a significant correlation with fauna mediated fluxes of O2 and NH4+, while the relationships with abundance were not significant. The species composition of the community might influence ecosystem functioning, but in the present study, functional groups have a very poor relationship with FFauna (O2) and FFauna (NH4+). Despite the presence of engineer species, establishing general and simple rules to link macrofaunal parameters to functional attributes remains very difficult, suggesting that communities rather followed the idiosyncrasy and rivet hypothesis.

Sediment Transport over a Dredge Pit, Sandy Point Southeast, west flank of the Mississippi River during Summer Upcoast Currents: a Coupled Wave, Current and Sediment Numerical Model

NASA Astrophysics Data System (ADS)

Chaichitehrani, N.; Li, C.; Xu, K.; Bentley, S. J.; Miner, M. D.

2017-12-01

Sandy Point southeast, an elongated sand resource, was dredged in November 2012 to restore Pelican Island, Louisiana. Hydrodynamics and wave propagation patterns along with fluvial sediments from the Mississippi River influence the sediment and bottom boundary layer dynamics over Sandy Point. A state-of-the-art numerical model, Delft3D, was implemented to investigate current variations and wave transformation on Sandy Point as well as sediment transport pattern. Delft3d FLOW and WAVE modules were coupled and validated using WAVCIS and NDBC data. Sediment transport model was run by introducing both bed and river sediments, consisted of mainly mud and a small fraction of sand. A sediment transport model was evaluated for surface sediment concentration using data derived from satellite images. The model results were used to study sediment dynamics and bottom boundary layer characteristics focused on the Sandy Point area during summer. Two contrasting bathymetric configurations, with and without the Sandy Point dredge pit, were used to conduct an experiment on the sediment and bottom boundary layer dynamics. Preliminary model results showed that the presence of the Sandy Point pit has very limited effect on the hydrodynamics and wave pattern at the pit location. Sediments from the Mississippi River outlets, especially in the vicinity of the pit, get trapped in the pit under the easterly to the northeasterly upcoast current which prevails in August. We also examined the wave-induced sediment reworking and river-borne fluvial sediment over Sandy Point. The effect of wind induced orbital velocity increases the bottom shear stress compared to the time with no waves, relatively small wave heights (lower than 1.5 meters) along the deepest part of the pit (about 20 meters) causes little bottom sediment rework during this period. The results showed that in the summertime, river water is more likely the source of sedimentation in the pit.

Community regulation: the relative importance of recruitment and predation intensity of an intertidal community dominant in a seascape context.

PubMed

Rilov, Gil; Schiel, David R

2011-01-01

Predicting the strength and context-dependency of species interactions across multiple scales is a core area in ecology. This is especially challenging in the marine environment, where populations of most predators and prey are generally open, because of their pelagic larval phase, and recruitment of both is highly variable. In this study we use a comparative-experimental approach on small and large spatial scales to test the relationship between predation intensity and prey recruitment and their relative importance in shaping populations of a dominant rocky intertidal space occupier, mussels, in the context of seascape (availability of nearby subtidal reef habitat). Predation intensity on transplanted mussels was tested inside and outside cages and recruitment was measured with standard larval settlement collectors. We found that on intertidal rocky benches with contiguous subtidal reefs in New Zealand, mussel larval recruitment is usually low but predation on recruits by subtidal consumers (fish, crabs) is intense during high tide. On nearby intertidal rocky benches with adjacent sandy subtidal habitats, larval recruitment is usually greater but subtidal predators are typically rare and predation is weaker. Multiple regression analysis showed that predation intensity accounts for most of the variability in the abundance of adult mussels compared to recruitment. This seascape-dependent, predation-recruitment relationship could scale up to explain regional community variability. We argue that community ecology models should include seascape context-dependency and its effects on recruitment and species interactions for better predictions of coastal community dynamics and structure.

Sediment Chemistry and Toxicity in Barnegat Bay, New Jersey: Pre- and Post- Hurricane Sandy, 2012-2013.

USGS Publications Warehouse

Romanok, Kristin M.; Szabo, Zoltan; Reilly, Timothy J.; Defne, Zafer; Ganju, Neil K.

2016-01-01

Hurricane Sandy made landfall in Barnegat Bay, October, 29, 2012, damaging shorelines and infrastructure. Estuarine sediment chemistry and toxicity were investigated before and after to evaluate potential environmental health impacts and to establish post-event baseline sediment-quality conditions. Trace element concentrations increased throughout Barnegat Bay up to two orders of magnitude, especially north of Barnegat Inlet, consistent with northward redistribution of silt. Loss of organic compounds, clay, and organic carbon is consistent with sediment winnowing and transport through the inlets and sediment transport modeling results. The number of sites exceeding sediment quality guidance levels for trace elements tripled post-Sandy. Sediment toxicity post-Sandy was mostly unaffected relative to pre-Sandy conditions, but at the site with the greatest relative increase for trace elements, survival rate of the test amphipod decreased (indicating degradation). This study would not have been possible without comprehensive baseline data enabling the evaluation of storm-derived changes in sediment quality.

Sediment chemistry and toxicity in Barnegat Bay, New Jersey: Pre- and post-Hurricane Sandy, 2012-13.

PubMed

Romanok, Kristin M; Szabo, Zoltan; Reilly, Timothy J; Defne, Zafer; Ganju, Neil K

2016-06-30

Hurricane Sandy made landfall in Barnegat Bay, October, 29, 2012, damaging shorelines and infrastructure. Estuarine sediment chemistry and toxicity were investigated before and after to evaluate potential environmental health impacts and to establish post-event baseline sediment-quality conditions. Trace element concentrations increased throughout Barnegat Bay up to two orders of magnitude, especially north of Barnegat Inlet, consistent with northward redistribution of silt. Loss of organic compounds, clay, and organic carbon is consistent with sediment winnowing and transport through the inlets and sediment transport modeling results. The number of sites exceeding sediment quality guidance levels for trace elements tripled post-Sandy. Sediment toxicity post-Sandy was mostly unaffected relative to pre-Sandy conditions, but at the site with the greatest relative increase for trace elements, survival rate of the test amphipod decreased (indicating degradation). This study would not have been possible without comprehensive baseline data enabling the evaluation of storm-derived changes in sediment quality. Published by Elsevier Ltd.

Isotopic identification of natural vs. anthropogenic lead sources in marine sediments from the inner Ría de Vigo (NW Spain).

PubMed

Álvarez-Iglesias, P; Rubio, B; Millos, J

2012-10-15

San Simón Bay, the inner part of the Ría de Vigo (NW Spain), an area previously identified as highly polluted by Pb, was selected for the application of Pb stable isotope ratios as a fingerprinting tool in subtidal and intertidal sediment cores. Lead isotopic ratios were determined by inductively coupled plasma mass spectrometry on extracts from bulk samples after total acid digestion. Depth-wise profiles of (206)Pb/(207)Pb, (206)Pb/(204)Pb, (207)Pb/(204)Pb, (208)Pb/(204)Pb and (208)Pb/(207)Pb ratios showed, in general, an upward decrease for both intertidal and subtidal sediments as a consequence of the anthropogenic activities over the last century, or centuries. Waste channel samples from a nearby ceramic factory showed characteristic Pb stable isotope ratios different from those typical of coal and petrol. Natural isotope ratios from non-polluted samples were established for the study area, differentiating sediments from granitic or schist-gneiss sources. A binary mixing model employed on the polluted samples allowed estimating the anthropogenic inputs to the bay. These inputs represented between 25 and 98% of Pb inputs in intertidal samples, and 9-84% in subtidal samples, their contributions varying with time. Anthropogenic sources were apportioned according to a three-source model. Coal combustion-related emissions were the main anthropogenic source Pb to the bay (60-70%) before the establishment of the ceramic factory in the area (in the 1970s) which has since constituted the main source (95-100%), followed by petrol-related emissions. The Pb inputs history for the intertidal area was determined for the 20th century, and, for the subtidal area, the 19th and 20th centuries. Copyright © 2012 Elsevier B.V. All rights reserved.

Community Regulation: The Relative Importance of Recruitment and Predation Intensity of an Intertidal Community Dominant in a Seascape Context

PubMed Central

Rilov, Gil; Schiel, David R.

2011-01-01

Predicting the strength and context-dependency of species interactions across multiple scales is a core area in ecology. This is especially challenging in the marine environment, where populations of most predators and prey are generally open, because of their pelagic larval phase, and recruitment of both is highly variable. In this study we use a comparative-experimental approach on small and large spatial scales to test the relationship between predation intensity and prey recruitment and their relative importance in shaping populations of a dominant rocky intertidal space occupier, mussels, in the context of seascape (availability of nearby subtidal reef habitat). Predation intensity on transplanted mussels was tested inside and outside cages and recruitment was measured with standard larval settlement collectors. We found that on intertidal rocky benches with contiguous subtidal reefs in New Zealand, mussel larval recruitment is usually low but predation on recruits by subtidal consumers (fish, crabs) is intense during high tide. On nearby intertidal rocky benches with adjacent sandy subtidal habitats, larval recruitment is usually greater but subtidal predators are typically rare and predation is weaker. Multiple regression analysis showed that predation intensity accounts for most of the variability in the abundance of adult mussels compared to recruitment. This seascape-dependent, predation-recruitment relationship could scale up to explain regional community variability. We argue that community ecology models should include seascape context-dependency and its effects on recruitment and species interactions for better predictions of coastal community dynamics and structure. PMID:21887351

Spatial variability of sediment transport processes over intra‐ and subtidal timescales within a fringing coral reef system

USGS Publications Warehouse

Pomeroy, Andrew; Lowe, Ryan J.; Ghisalberti, Marco; Winter, Gundula; Storlazzi, Curt D.; Cuttler, Michael V. W.

2018-01-01

Sediment produced on fringing coral reefs that is transported along the bed or in suspension affects ecological reef communities as well as the morphological development of the reef, lagoon, and adjacent shoreline. This study quantified the physical process contribution and relative importance of incident waves, infragravity waves, and mean currents to the spatial and temporal variability of sediment in suspension. Estimates of bed shear stresses demonstrate that incident waves are the key driver of the SSC variability spatially (reef flat, lagoon, and channels) but cannot not fully describe the SSC variability alone. The comparatively small but statistically significant contribution to the bed shear stress by infragravity waves and currents, along with the spatial availability of sediment of a suitable size and volume, is also important. Although intra‐tidal variability in SSC occurs in the different reef zones, the majority of the variability occurs over longer slowly varying (subtidal) time scales, which is related to the arrival of large incident waves at a reef location. The predominant flow pathway, which can transport suspended sediment, consists of cross‐reef flow across the reef flat that diverges in the lagoon and returns offshore through channels. This pathway is primarily due to subtidal variations in wave‐driven flows, but can also be driven alongshore by wind stresses when the incident waves are small. Higher frequency (intra‐tidal) current variability also occur due to both tidal flows, as well as variations in the water depth that influence wave transmission across the reef and wave‐driven currents.

Time-lapse imagery of the breaching of Marmot Dam, Oregon, and subsequent erosion of sediment by the Sandy River, October 2007 to May 2008

USGS Publications Warehouse

Major, Jon J.; Spicer, Kurt R.; Collins, Rebecca A.

2010-01-01

In 2007, Marmot Dam on the Sandy River, Oregon, was removed and a temporary cofferdam standing in its place was breached, allowing the river to flow freely along its entire length. Time-lapse imagery obtained from a network of digital single-lens reflex cameras placed around the lower reach of the sediment-filled reservoir behind the dam details rapid erosion of sediment by the Sandy River after breaching of the cofferdam. Within hours of the breaching, the Sandy River eroded much of the nearly 15-m-thick frontal part of the sediment wedge impounded behind the former concrete dam; within 24-60 hours it eroded approximately 125,000 m3 of sediment impounded in the lower 300-meter-reach of the reservoir. The imagery shows that the sediment eroded initially through vertical incision, but that lateral erosion rapidly became an important process.

Consequences of Increasing Hypoxic Disturbance on Benthic Communities and Ecosystem Functioning

PubMed Central

Villnäs, Anna; Norkko, Joanna; Lukkari, Kaarina; Hewitt, Judi; Norkko, Alf

2012-01-01

Disturbance-mediated species loss has prompted research considering how ecosystem functions are changed when biota is impaired. However, there is still limited empirical evidence from natural environments evaluating the direct and indirect (i.e. via biota) effects of disturbance on ecosystem functioning. Oxygen deficiency is a widespread threat to coastal and estuarine communities. While the negative impacts of hypoxia on benthic communities are well known, few studies have assessed in situ how benthic communities subjected to different degrees of hypoxic stress alter their contribution to ecosystem functioning. We studied changes in sediment ecosystem function (i.e. oxygen and nutrient fluxes across the sediment water-interface) by artificially inducing hypoxia of different durations (0, 3, 7 and 48 days) in a subtidal sandy habitat. Benthic chamber incubations were used for measuring responses in sediment oxygen and nutrient fluxes. Changes in benthic species richness, structure and traits were quantified, while stress-induced behavioral changes were documented by observing bivalve reburial rates. The initial change in faunal behavior was followed by non-linear degradation in benthic parameters (abundance, biomass, bioturbation potential), gradually impairing the structural and functional composition of the benthic community. In terms of ecosystem function, the increasing duration of hypoxia altered sediment oxygen consumption and enhanced sediment effluxes of NH4 + and dissolved Si. Although effluxes of PO4 3− were not altered significantly, changes were observed in sediment PO4 3− sorption capability. The duration of hypoxia (i.e. number of days of stress) explained a minor part of the changes in ecosystem function. Instead, the benthic community and disturbance-driven changes within the benthos explained a larger proportion of the variability in sediment oxygen- and nutrient fluxes. Our results emphasize that the level of stress to the benthic habitat matters, and that the link between biodiversity and ecosystem function is likely to be affected by a range of factors in complex, natural environments. PMID:23091592

Metagenomic Analysis of Subtidal Sediments from Polar and Subpolar Coastal Environments Highlights the Relevance of Anaerobic Hydrocarbon Degradation Processes

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

Espínola, Fernando; Dionisi, Hebe M.; Borglin, Sharon

In this work, we analyzed the community structure and metabolic potential of sediment microbial communities in high-latitude coastal environments subjected to low to moderate levels of chronic pollution. Subtidal sediments from four low-energy inlets located in polar and subpolar regions from both Hemispheres were analyzed using large-scale 16S rRNA gene and metagenomic sequencing. Communities showed high diversity (Shannon’s index 6.8 to 10.2), with distinct phylogenetic structures (<40% shared taxa at the Phylum level among regions) but similar metabolic potential in terms of sequences assigned to KOs. Environmental factors (mainly salinity, temperature, and in less extent organic pollution) were drivers ofmore » both phylogenetic and functional traits. Bacterial taxa correlating with hydrocarbon pollution included families of anaerobic or facultative anaerobic lifestyle, such as Desulfuromonadaceae, Geobacteraceae, and Rhodocyclaceae. In accordance, biomarker genes for anaerobic hydrocarbon degradation (bamA, ebdA, bcrA, and bssA) were prevalent, only outnumbered by alkB, and their sequences were taxonomically binned to the same bacterial groups. BssA-assigned metagenomic sequences showed an extremely wide diversity distributed all along the phylogeny known for this gene, including bssA sensu stricto, nmsA, assA, and other clusters from poorly or not yet described variants. This work increases our understanding of microbial community patterns in cold coastal sediments, and highlights the relevance of anaerobic hydrocarbon degradation processes in subtidal environments.« less

Intensities of drilling predation of molluscan assemblages in intertidal and subtidal soft substrates in the Persian (Arabian) Gulf

NASA Astrophysics Data System (ADS)

Handler, Sabine M.; Albano, Paolo G.; Bentlage, Rudolf; Drummond, Hannah; García-Ramos, Diego A.; Zuschin, Martin

2016-04-01

Intensities of drilling predation of molluscan assemblages in intertidal and subtidal soft substrates in the Persian (Arabian) Gulf Sabine Maria Handler1, Paolo G. Albano1, Rudolf Bentlage2, Hannah Drummond2, D.A. García-Ramos1, Martin Zuschin1 1 Department of Paleontology, University of Vienna, Austria 2 St. Lawrence University, Canton, New York 13617, USA Trace fossils left by predators in the skeleton of their prey are arguably one of the most powerful sources of direct data on predator-prey interactions available in the fossil record. Drill holes, especially those attributed to naticid and muricid gastropods, are unambiguous marks of predation and allow discriminating between successful and unsuccessful predation attempts (complete and incomplete holes, respectively). Latitude and water depth influence drilling frequency. We inspected death assemblages of an intertidal flat and of two subtidal (water depth between 6 and 20 m) sandy sites in the Persian (Arabian) Gulf, off the coast of the United Arab Emirates, to determine the patterns of predation on shelled molluscs along the depth gradient. The study is based on ~7,000 and ~60,000 shells from the intertidal and subtidal, respectively. Drilling Frequency (DF, the number of drilled individuals), Incomplete Drilling Frequency (IDF, number of incomplete drill holes), and Prey Effectiveness (ratio between the number of incomplete drill holes and the total number of drilling attempts) were used as metrics of drilling intensity. We observed major differences between the intertidal and subtidal study areas. Drilling frequencies were generally remarkably low and intertidal flats showed a much lower drilling frequency than the subtidal (1.4% and 6.7%, respectively). In the subtidal, we observed significant differences of drilling intensity among bivalve species and between the two sites. However, predation metrics did not correlate with environmental factors such as substrate type and depth, nor with species life habits such as infaunal vs. epifaunal and death assemblage indices such as diversity, abundance and evenness. The abundance of naticid and muricid predators in the living and death assemblage also did not correlate with predation intensities, with the single exception of muricid abundance in the LA at one of the two subtidal sites. The study shows that bivalve predation intensity in the studied area is highly variable among prey species and depth zones (intertidal vs subtidal), but poorly dependant upon other environmental and community structure factors. Results for gastropods are currently being analysed.

Assessment of chemical and biological significance of arsenical species in the Maurice River drainage basin (N. J. ). Part II. Partitioning of arsenic into bottom sediments

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

Faust, S.D.; Winka, A.J.; Belton, T.

1987-01-01

A laboratory study was conducted on the partitioning of four arsenical species onto organic and sandy bottom sediments of Union Lake, N.J. Sandy sediments released more arsenic and sorbed less arsenic than the organic sediments. Organic sediments generally sorbed inorganic As species better than organic As species.

Modern sedimentary environments in Boston Harbor, Massachusetts

USGS Publications Warehouse

Knebel, H.J.; Rendigs, R. R.; Bothner, Michael H.

1991-01-01

Analyses of sidescan-sonar records supplemented by available bathymetric, sedimentary, subbottom, and bottom-current data reveal the distributions of the following three categories of sedimentary environments within the glaciated, topographically complex Boston Harbor estuary in Massachusetts. 1) Environments of erosion appear on the sonographs either as patterns with isolated strong reflections or as uniform patterns of strong reflectivity. These patterns define outcrops of bedrock or till and coarse lag deposits that are being scoured and winnowed by tidal- and wave-induced currents. Erosional areas are located primarily along mainland and insular shores, within large channels that have strong tidal currents, atop submerged ridges and knolls, and across much of the harbor entrance. 2) Environments of deposition are depicted on the sidescan-sonar records as smooth, featureless surfaces that have low to moderate reflectivity. Depositional environments are found predominantly over shallow subtidal flats and in broad bathymetric lows where tidal currents are weak. Sediments within depositional areas are organic-rich sandy and clayey silts that are accumulating at rates ranging from 0.01 to 0.11 g/cm 2 /yr or 4000 to 46,100 metric tons/yr. The cumulative mass of modern mud in harbor depocenters is 24.3 million metric tons. 3) Environments of sediment reworking constitute areas affected by a combination of erosional and depositional processes. They are characterized on the sonographs by mosaics of light and dark patches produced by relatively subtle and gradational changes in reflectivity. Reworked sediments have diverse grain sizes that overlap and are transitional between those of the other two sedimentary environments, and they are indicative of highly variable bottom currents.

The macrofaunal communities in the shallow subtidal areas for the first 3 years after the Hebei Spirit oil spill.

PubMed

Seo, Jin-Young; Kim, Moonkoo; Lim, Hyun-Sig; Choi, Jin-Woo

2014-05-15

In order to detect the early impact of the Hebei Spirit oil spill on the shallow subtidal macrozoobenthic communities, macrobenthic fauna were collected seasonally for 3 years. The alkylated PAHs concentrations within sediments near Mallipo beach remained as high as 129 ng g(-)(1) DW one month after the oil spill, but the concentration decreased below the background level thereafter. The number of species and density decreased in 4 months compared to those before the oil spill. An opportunistic polychaete, Prionospio paradisea, occurred as a dominant species at subtidal area near Mallipo beach in 10 months after the oil spill. Any mass mortality of amphipods and any clear dominance of opportunistic species were not detected except for the stations near Mallipo and Hagampo beaches. The macrobenthic communities at the shallow subtidal stations seemed to have a relatively stable faunal composition, even not fully recovered, in 3 years after the Hebei Spirit oil spill. Copyright © 2014 Elsevier Ltd. All rights reserved.

Estuarine sedimentation, sediment character, and foraminiferal distribution in central San Francisco Bay, California

USGS Publications Warehouse

Chin, John L.; Woodrow, Donald L.; McGann, Mary; Wong, Florence L.; Fregoso, Theresa A.; Jaffe, Bruce E.

2010-01-01

Central San Francisco Bay is the deepest subembayment in the San Francisco Bay estuary and hence has the largest water volume of any of the subembayments. It also has the strongest tidal currents and the coarsest sediment within the estuary. Tidal currents are strongest over the west-central part of central bay and, correspondingly, this area is dominated by sand-size sediment. Much of the area east of a line from Angel Island to Alcatraz Island is characterized by muddy sand to sandy mud, and the area to the west of this line is sandy. The sand-size sediment over west-central bay furthermore is molded by the energetic tidal currents into bedforms of varying sizes and wavelengths. Bedforms typically occur in water depths of 15-25 m. High resolution bathymetry (multibeam) from 1997 and 2008 allow for subdivision of the west-central bayfloor into four basic types based on morphologic expression: featureless, sand waves, disrupted/man-altered, and bedrock knobs. Featureless and sand-wave morphologies dominate the bayfloor of west-central bay. Disrupted bayfloor has a direct association with areas that are undergoing alteration due to human activities, such as sand-mining lease areas, dredging, and disposal of dredge spoils. Change detection analysis, comparing the 1997 and 2008 multibeam data sets, shows that significant change has occurred in west-central bay during the roughly 10 years between surveys. The surveyed area lost about 5.45 million m3 of sediment during the decade. Sand-mining lease areas within west-central bay lost 6.77 million m3 as the bayfloor deepened. Nonlease areas gained 1.32 million m3 of sediment as the bayfloor shallowed slightly outside of sand-mining lease areas. Furthermore, bedform asymmetry did not change significantly, but some bedforms did migrate some tens of meters. Gravity cores show that the area east of Angel and Alcatraz Islands is floored by clayey silts or silty sand whereas the area to the west of the islands is floored dominantly by sand- to coarse sand-sized sediment. Sandy areas also include Raccoon Strait, off Point Tiburon, and on the subtidal Alcatraz, Point Knox, and Presidio Shoals. Drab-colored silty clays are the dominant sediment observed in gravity cores from central bay. Their dominance along the length of the core suggests that silty clays have been deposited consistently over much of this subembayment for the time period covered by the recovered sediments (Woodrow and others, this report). Stratification types include weakly-defined laminae, 1-3 mm thick. Few examples of horizontal lamination in very fine sand or silt were observed. Cross lamination, including ripples, was observed in seven cores. Erosional surfaces were evident in almost every core where x-radiographs were available (they are very difficult to observe visually). Minor cut-and-fill structures also were noted in three cores and inclined strata were observed in three cores. Textural patterns in central bay indicate that silts and clays dominate the shallow water areas and margins of the bay. Sand dominates the tidal channel just east of Angel and Alcatraz Islands and to the west of the islands to the Golden Gate. The pattern of sand-sized sediment, as determined by particle-size analysis, suggests that sand movement is easterly from the west-central part of the bay. A second pattern of sand movement is to the south from the southwestern extremity of San Pablo Bay (boundary approximated by the location of the Richmond-San Rafael Bridge). Age dates for central bay sediment samples were obtained by carbon-14 radiometric age dating. Age dates were determined from shell material that was interpreted to be largely in-place (not transported). Age dates subsequently were reservoir corrected and then converted to calendar years. Sediments sampled from central bay cores range in age from 330 to 4,155 years before present. Foraminiferal distribution in the San Francisco Bay estuary is fairly well

Ecological Effects of Rubble Weir Jetty Construction at Murrells Inlet, South Carolina. Volume 2. Changes in Macrobenthic Communities of Sandy Beach and Nearshore ENvironments.

DTIC Science & Technology

1984-06-01

species were not commonly observed, and oligochaetes and nematodes were abundant in the area. Rany of these differences were attributed to normal...1977-78 (Table 3). Subtidally, amphipods and pelecypods were most abundant in 1982, while oligochaetes and nematodes largely dominated the intertidal...generally restricted to that level and the highest intertidal level (Table 10). Nematodes were also abundant in the upper intertidal zone, with greatest

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

Wolfe, D.A.

Three separate papers are represented in this final report; Toxicity of intertidal and subtidal sediments contaminated by the Exxon Valdez oil spill; Comparative toxicities of polar and non-polar organic fractions from sediments affected by the Exxon Valdez oil spill in Prince William Sound, Alaska; and Fate of the oil spilled from the T/V Exxon Valdez in Prince William Sound, Alaska.

Functional response of an adapted subtidal macrobenthic community to an oil spill: macrobenthic structure and bioturbation activity over time throughout an 18-month field experiment.

PubMed

Gilbert, Franck; Stora, Georges; Cuny, Philippe

2015-10-01

An experimental oil spill was carried out in order to assess in situ responses of a macrobenthic community of shallow subtidal sediments historically exposed to petroleum contamination. Both structural and functional (bioturbation activity) parameters of the community, subjected or not to a pulse acute contamination (25,000 ppm), were studied for 18 months. No difference in the community structure was detected between contaminated and control sediments, from 6 to 18 months of experimentation. Vertical distributions of organisms, however, were affected by the presence of oil contamination leading to a deeper burial of some polychaete species. In the same time, changes in sediment-reworking activity and more especially a deeper particle burying in sediments subjected to acute oil contamination were shown. These results highlight the need to complete the analysis of community structure by assessing functional aspects, such as bioturbation activity, a process integrating various aspects of benthic behaviour (e.g. feeding, locomotion, burrow building) in order to estimate real (structural and functional) and long-term effects of oil contamination on benthic communities.

Contribution of phytoplankton and benthic microalgae to inner shelf sediments of the north-central Gulf of Mexico

NASA Astrophysics Data System (ADS)

Grippo, M. A.; Fleeger, J. W.; Rabalais, N. N.; Condrey, R.; Carman, K. R.

2010-03-01

Marine sediment may contain both settled phytoplankton and benthic microalgae (BMA). In river-dominated, shallow continental shelf systems, spatial, and temporal heterogeneity in sediment type and water-column characteristics (e.g., turbidity and primary productivity) may promote spatial variation in the relative contribution of these two sources to the sediment organic matter pool available to benthic consumers. Here we use photosynthetic pigment analysis and microscopic examination of sediment microalgae to investigate how the biomass, composition, and degradation state of sediment-associated microalgae vary along the Louisiana (USA) inner shelf, a region strongly influenced by the Mississippi River. Three sandy shoals and surrounding muddy sediments with depths ranging from 4 to 20 m were sampled in April, August, and October 2007. Pigment composition suggested that sediment microalgae were primarily diatoms at all locations. We found no significant differences in sediment chlorophyll a concentrations (8-77 mg m -2) at the shoal and off-shoal stations. Epipelic pennate diatoms (considered indicative of BMA) made up a significantly greater proportion of sediment diatoms at sandy (50-98%) compared to more silty off-shoal stations (16-56%). The percentage of centric diatoms (indicators of settled phytoplankton) in the sediment was highest in August. Sediment total pheopigment concentrations on sandy stations (<20 mg m -2) were significantly lower than concentrations at nearby muddy stations (>40 mg m -2), suggesting differences in sediment microalgal degradation state. These observations suggest that BMA predominate in shallow sandy sediments and that phytodetritus predominates at muddy stations. Our results also suggest that the relative proportion of phytodetritus in the benthos was highest where phytoplankton biomass in the overlying water was greatest, independent of sediment type. The high biomass of BMA found on shoals suggests that benthic primary production on sandy sediments represents a potentially significant local source of sediment microalgal carbon that may be utilized by benthic consumers in continental shelf food webs.

Impacts of Bottom Fishing on Sediment Biogeochemical and Biological Parameters in Cohesive and Non-cohesive Sediments

NASA Astrophysics Data System (ADS)

Sciberras, M.; Hiddink, J. G.; Powell, C.; Parker, R.; Krӧger, S.; Bolam, S. G.; Robertson, C.

2016-02-01

Sediment resuspension and bed reworking by tides, waves and biological activity are frequent in the energetic coastal environments. Sediment mixing by tides and waves are generally more important in regulating sediment processes in advection-dominated system such as sandy sediments, whereas sediment reworking by bioturbation is more important in diffusion-dominated systems such as muddy sediments. Bottom fishing constitutes an additional significant impact on benthic communities and sediment biogeochemical processes in coastal areas through physical changes in sediment resuspension and mixing and changes to bioturbating fauna. This study examined the biological (macro-infaunal) and biogeochemical responses to fishing at a muddy and sandy site in the Irish Sea that were predominantly impacted by otter trawls and scallop dredges, respectively. The sandy habitat (>90% sand) was typical of a hydrodynamic environment characterized by a diverse array of small infaunal species, low organic carbon levels and fast remineralisation of organic matter in the sediment. The muddier habitat (>65% fines) was dominated by fewer but larger bioturbating species compared to sand, and illustrated highly diffusional solute transport, higher organic carbon content and a shallower oxygen penetration depth. Generally there appeared to be no clear statistically significant changes in the biogeochemistry of the sandy or muddy habitat that could be attributed to different intensities of fishing. However, pore-water nutrient profiles of ammonium, phosphate and silicate provided clear evidence of organic matter burial and/or mixing as a result of trawling at the muddy site. The biogeochemistry at the sandy site appeared to remain dominated by the natural physical environment, so impact of fishing disturbance was less evident. These results suggest that fishing does not have comparable effects on the biology and biogeochemical processes in all benthic habitats.

Ecological evaluation of an experimental beneficial use scheme for dredged sediment disposal in shallow tidal waters.

PubMed

van der Wal, Daphne; Forster, Rodney M; Rossi, Francesca; Hummel, Herman; Ysebaert, Tom; Roose, Frederik; Herman, Peter M J

2011-01-01

An experiment was performed to test an alternative dredging strategy for the Westerschelde estuary. Clean sand dredged from the navigation channel was disposed seawards of an eroding intertidal flat in order to modify morphology and hydrodynamics, improving the multi-channel system with ecologically productive shallow water habitat. Five years of intensive monitoring revealed that part of the disposed sediment moved slowly towards the flat, increasing the very shallow subtidal and intertidal area, as planned. The sand in the impact zone became gradually finer after disposal, possibly due to reduced current velocities. Nevertheless, no changes in macrobenthic biomass, density, species richness and composition were detected in the subtidal zone, also demonstrating rapid macrobenthic recovery. In the intertidal zone, no ecological effects could be revealed superimposed on trends associated with long-term sediment fining. Thus, despite morphological success and absence of detected negative ecological impacts of the experiment, new beneficial habitat was not created. Copyright © 2010 Elsevier Ltd. All rights reserved.

Assessment of heavy metal and petroleum hydrocarbon contamination in the Sultanate of Oman with emphasis on harbours, marinas, terminals and ports.

PubMed

Jupp, Barry P; Fowler, Scott W; Dobretsov, Sergey; van der Wiele, Henk; Al-Ghafri, Ahmed

2017-08-15

The assessment here includes data on levels of contaminants (petroleum hydrocarbons and heavy metals) in sediments and biomonitor organisms, including the eulittoral rock oyster Saccostrea cucullata and subtidal biomonitors, the barnacle Balanus trigonus and the antipatharian coral Antipathes sp., at harbours, marinas, terminals and large ports along the coastline of Oman. TBT levels in harbour and port sediments up to a maximum of 100ppb TBT dry weight are highlighted. Oysters contained concentrations up to 367ppm mg TPH/kg dry weight. The maximum levels of Cd, Cu, Pb and Zn were found in the subtidal sediments and barnacles at the oil tanker loading Single Buoy Mooring stations in Mina Al Fahal. In general, the levels of most of the contaminants analysed are at low to moderate concentrations compared to those in highly contaminated sites such as shipyards and dry docks, but continued monitoring is recommended especially during any dredging campaigns. Copyright © 2017 Elsevier Ltd. All rights reserved.

Near-edge wrack effects on bare sediments: Small scale variation matters in the monitoring of sandy beaches.

PubMed

MacMillan, Mitchell R; Tummon Flynn, Paula; Duarte, Cristian; Quijón, Pedro A

2016-12-01

The influence of wrack on sandy beach communities is well-documented but its effect on bare sediments located immediately beyond its edge has not yet been tested. This study aimed to explore these effects by surveying bare sediments located at increasing distances (0.5-2 m) from the wrack in five sandy beaches on Prince Edward Island, Atlantic Canada. In addition, we tested the influence of wrack with a field manipulation using wrack patches made up of rockweed bundles. The survey indicated that a modest but significant number of amphipods and beetles occupied bare sediments located 0.5 m from the edge of the wrack, but that those numbers dropped in sediments 1 m away and farther. The outcome of the field manipulation showed a similar pattern. Although small in spatial scale, our results have implications for the monitoring sandy beaches affected by scattered as well as heavy wrack input. Copyright © 2016 Elsevier Ltd. All rights reserved.

Spatial patterns of sub-tidal seagrasses and their tissue nutrients in the Torres Strait, northern Australia: Implications for management

NASA Astrophysics Data System (ADS)

Sheppard, James K.; Carter, Alex B.; McKenzie, Len J.; Pitcher, C. Roland; Coles, Robert G.

2008-09-01

The distribution and nutritional profiles of sub-tidal seagrasses from the Torres Strait were surveyed and mapped across an area of 31,000 km 2. Benthic sediment composition, water depth, seagrass species type and nutrients were sampled at 168 points selected in a stratified representative pattern. Eleven species of seagrass were present at 56 (33.3%) of the sample points. Halophila spinulosa, Halophila ovalis, Cymodocea serrulata and Syringodium isoetifolium were the most common species and these were nutrient profiled. Sub-tidal seagrass distribution (and associated seagrass nutrient concentrations) was generally confined to northern-central and south-western regions of the survey area (

Towards Predicting Basin-Wide Invertebrate Organic Biomass and Production in Marine Sediments from a Coastal Sea

PubMed Central

Burd, Brenda J.; Macdonald, Tara A.; van Roodselaar, Albert

2012-01-01

Detailed knowledge of environmental conditions is required to understand faunal production in coastal seas with topographic and hydrographic complexity. We test the hypothesis that organic biomass and production of subtidal sediment invertebrates throughout the Strait of Georgia, west coast of Canada, can be predicted by depth, substrate type and organic flux modified to reflect lability and age of material. A basin-wide database of biological, geochemical and flux data was analysed using an empirical production/biomass (P/B) model to test this hypothesis. This analysis is unique in the spatial extent and detail of P/B and concurrent environmental measurements over a temperate coastal region. Modified organic flux was the most important predictor of organic biomass and production. Depth and substrate type were secondary modifiers. Between 69–74% of variability in biomass and production could be explained by the combined environmental factors. Organisms <1 mm were important contributors to biomass and production primarily in shallow, sandy sediments, where high P/B values were found despite low organic flux. Low biomass, production, and P/B values were found in the deep, northern basin and mainland fjords, which had silty sediments, low organic flux, low biomass of organisms <1 mm, and dominance by large, slow-growing macrofauna. In the highest organic flux and biomass areas near the Fraser River discharge, production did not increase beyond moderate flux levels. Although highly productive, this area had low P/B. Clearly, food input is insufficient to explain the complex patterns in faunal production revealed here. Additional environmental factors (depth, substrate type and unmeasured factors) are important modifiers of these patterns. Potential reasons for the above patterns are explored, along with a discussion of unmeasured factors possibly responsible for unexplained (30%) variance in biomass and production. We now have the tools for basin-wide first-order estimates of sediment invertebrate production. PMID:22792267

Environmental factors controlling macrofaunal assemblages on six microtidal beaches of the Ligurian Sea (NW Mediterranean)

NASA Astrophysics Data System (ADS)

Covazzi Harriague, Anabella; Albertelli, Giancarlo

2007-06-01

Six microtidal beaches along the Ligurian coast (NW Mediterranean, Italy) were sampled in order to study their macrofaunal assemblages. All six beaches are subject to heavy tourism in the swimming season and three were subject to nourishment activities during the study period (May 2000). The beaches of Lavagna, Varazze and Pietra Ligure were sampled three times: before the nourishment and the onset of the swimming season (March 2000), after the nourishment (June 2000) and at the end of the swimming season (October 2000). The beaches of Varigotti, Albisola and Loano were sampled twice: before and after the swimming season (March and October 2000, respectively). Sampling was performed along two transects (T1 and T2), about 500 m apart, each transect having three sampling stations: one placed in the swash zone, one in the surf zone and one in the subtidal zone (depth of 3-5 m), in order to verify how far the nourishment material reached. The beaches were characterised by coarse sediments that became finer towards the sub-littoral station. The Beach Deposit Index and Beach Index classified the beaches as reflective (Lavagna, Varazze, Albisola and Varigotti) or intermediate (Pietra Ligure and Loano). Species richness showed a clearly increasing pattern from the swash zone (average 7) to the subtidal zone (average 103). The beach communities were dominated by polychaetes, in particular Saccocirrus papillocercus, which was mainly responsible for the dissimilarity between the beach and subtidal stations. The highest abundance was observed at the surf station (average 118.6 ind. m -2) and the lowest at the subtidal station (average 82.1 ind. m -2). The sediment composition and macrofaunal assemblages were not affected by the beach nourishment. The beach communities responded to different environmental descriptors: species richness seemed to be governed by environmental harshness, while abundance seemed to be linked to the degree of homogeneity of the sediments and the quality of the food supply.

Study on sound-speed dispersion in a sandy sediment at frequency ranges of 0.5-3 kHz and 90-170 kHz

NASA Astrophysics Data System (ADS)

Yu, Sheng-qi; Liu, Bao-hua; Yu, Kai-ben; Kan, Guang-ming; Yang, Zhi-guo

2017-03-01

In order to study the properties of sound-speed dispersion in a sandy sediment, the sound speed was measured both at high frequency (90-170 kHz) and low frequency (0.5-3 kHz) in laboratory environments. At high frequency, a sampling measurement was conducted with boiled and uncooked sand samples collected from the bottom of a large water tank. The sound speed was directly obtained through transmission measurement using single source and single hydrophone. At low frequency, an in situ measurement was conducted in the water tank, where the sandy sediment had been homogeneously paved at the bottom for a long time. The sound speed was indirectly inverted according to the traveling time of signals received by three buried hydrophones in the sandy sediment and the geometry in experiment. The results show that the mean sound speed is approximate 1710-1713 m/s with a weak positive gradient in the sand sample after being boiled (as a method to eliminate bubbles as much as possible) at high frequency, which agrees well with the predictions of Biot theory, the effective density fluid model (EDFM) and Buckingham's theory. However, the sound speed in the uncooked sandy sediment obviously decreases (about 80%) both at high frequency and low frequency due to plenty of bubbles in existence. And the sound-speed dispersion performs a weak negative gradient at high frequency. Finally, a water-unsaturated Biot model is presented for trying to explain the decrease of sound speed in the sandy sediment with plenty of bubbles.

Assessment of chemical and biological significance of arsenical compounds in the Maurice River drainage basin (N. J. ). Part III. Transformations in aerobic and anaerobic conditions

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

Faust, S.D.; Winka, A.J.; Belton, T.

1987-01-01

A quiescent reservoir system revealed the effects of temperature (20/sup 0/C. and 30/sup 0/C), oxygen levels (aerobic and anaerobic) on the arsenic partitioning and interconversion in organic and sandy lake sediments. Temperature had little or no effect on the specie partitioning. In aerobic reservoirs (sandy and organic), the As(V) levels increased, especially in the organic sediment. In the anaerobic reservoir, the organic sediment maintained its level of As(III). The sandy sediment has a predominance of As(V) suggesting something other than the level of oxygen is a significant controlling factor.

Magnitude and timing of downstream channel aggradation and degradation in response to a dome-building eruption at Mount Hood, Oregon

USGS Publications Warehouse

Pierson, Thomas C.; Pringle, Patrick T.; Cameron, Kenneth A.

2011-01-01

A dome-building eruption at Mount Hood, Oregon, starting in A.D. 1781 and lasting until ca. 1793, produced dome-collapse lithic pyroclastic flows that triggered lahars and intermittently fed 108 m3 of coarse volcaniclastic sediment to sediment reservoirs in headwater canyons of the Sandy River. Mobilization of dominantly sandy sediment from these reservoirs by lahars and seasonal floods initiated downstream migration of a sediment wave that resulted in a profound cycle of aggradation and degradation in the lowermost reach of the river (depositional reach), 61-87 km from the source. Stratigraphic and sedimentologic relations in the alluvial fill, together with dendrochronologic dating of degradation terraces, demonstrate that (1) channel aggradation in response to sediment loading in the headwater canyons raised the river bed in this reach at least 23 m in a decade or less; (2) the transition from aggradation to degradation in the upper part of this reach roughly coincided with the end of the dome-building eruption; (3) fluvial sediment transport and deposition, augmented by one lahar, achieved a minimum average aggradation rate of ~2 m/yr; (4) the degradation phase of the cycle was more prolonged than the aggradation phase, requiring more than half a century for the river to reach its present bed elevation; and (5) the present longitudinal profile of the Sandy River in this reach is at least 3 m above the pre-eruption profile. The pattern and rate of channel response and recovery in the Sandy River following heavy sediment loading resemble those of other rivers similarly subjected to very large sediment inputs. The magnitude of channel aggradation in the lower Sandy River, greater than that achieved at other volcanoes following much larger eruptions, was likely enhanced by lateral confinement of the channel within a narrow incised valley. A combination of at least one lahar and winter floods from frequent moderate-magnitude rainstorms and infrequent very large storms was responsible for flushing large volumes of sediment to the depositional reach. These conditions permitted a sedimentation response in the Sandy River that approached the magnitude of channel aggradation resulting elsewhere from large explosive eruptions and high-intensity rainfall regimes, despite the fact that the Sandy River aggradation was in response to an unremarkable dome-building eruption in a climate dominated by low to moderate rainfall intensities.

Giant subtidal stromatolites forming in normal salinity waters

USGS Publications Warehouse

Dill, R.F.; Shinn, E.A.; Jones, A.T.; Kelly, K.; Steinen, R.P.

1986-01-01

We report here the discovery of giant lithified subtidal columnar stromatolites (>2 m high) growing in 7-8 m of clear oceanic water in current-swept channels between the Exuma Islands on the eastern Bahama Bank. They grow by trapping ooid and pelletal carbonate sand and synsedimentary precipitation of carbonate cement within a field of giant megaripples. The discovery is important to geologists and biologists because similar organo-sedimentary structures built by a combination of cementation and the trapping of sediment by microbes were the dominant fossil types during the Precambrian. Stromatolites are thought to have been responsible for the production of free oxygen and thus the evolution of animal life1,2. Until the discovery of small lithified subtidal columnar stromatolites in the Bahamas3, the only subtidal marine examples known to be living while undergoing lithification were in the hypersaline waters of Hamelin Pool at Shark Bay, Western Australia4-7. Shark Bay stromatolites range from intertidal to the shallow subtidal with the larger columns reaching 1 m in height. The Shark Bay stromatolites have strongly influenced geological interpretation; by analogy, many ancient stromatolites have been considered to have grown in intertidal and/or hypersaline conditions8, although hypersalinity was not a necessity for growth during the Precambrian because grazing metazoan life had not then evolved. ?? 1986 Nature Publishing Group.

[Effects of sediment on the early settlement stage of Sargassum horneri on rocky subtidal reefs].

PubMed

Bi, Yuan-Xin; Zhang, Shou-Yu; Wu, Zu-Li

2013-05-01

By using sediment trap and suction pump to measure the relative sediment levels across different sites and water depths, and through the in situ measurements of Sargassum horneri density, this paper assessed the relationships between the distribution of S. horneri and the sediment levels and wave exposure on the rocky subtidal platforms around Gouqi Island, China. The laboratory-based experiments were also conducted to test the effects of different sediment levels on the attachment of S. horneri zygote and the survival rate of S. horneri germling after the attachment. S. horneri predominated at the sites with lesser sediment and wave exposure, but less distributed in the sites with high level sediment and wave-exposure. At different water depths, the distribution of S. horneri was negatively correlated with the amount of sediment. A medium dusting (dry mass 10.47 mg x cm(-2), approximate 0.543 mm deep) of sediment on the plate reduced the percentage of S. horneri zygotes attached to the substratum by 4.4%, and a heavy dusting (dry mass 13.96 mg x cm(-2), approximate 0.724 mm deep) of sediment on the plate completely prevented the attachment. One week after the settlement of the zygotes, there were 24% of the germlings still survived when the dry mass sediment coverage was 13.96 mg x cm(-2). However, when the dry mass sediment coverage was up to 34.9 mg x cm(-2) (approximate 1.81 mm deep), 100% of the germlings died. Overall, the distribution of S. horneri was not only related to sediment level, but also restricted by wave exposure to some extent. Sediment level was a critical factor affecting the distribution of S. horneri, particularly at its zygote attachment stage.

A field experimental study on recolonization and succession of subtidal macrobenthic community in sediment contaminated with industrial wastes.

PubMed

Lu, L; Wu, R S S

2007-02-01

A field experiment was carried out in Hong Kong to study the patterns of recolonization and succession of subtidal macrobenthos in defaunated sediment contaminated with industrial wastes and to determine the time required for benthic recovery in the industrial-contaminated sediment. A total of 50 species was found with an average of 172 animals/tray and 24 species/tray recorded one month after deployment. Initial colonizers were predominantly polychaetes (96 animals/tray, accounting for 55.7%) and gastropods (47 animals/tray, accounting for 27.2%). Abundance of macrobenthos increased quickly to a peak (505 animals/tray) after four months, declined afterwards, and increased again till the end of the experiment. Species number peaked (57 species/tray) in the same month as abundance did, and gradually declined thereafter. Abundance, species number and diversity were significantly lower in the industrial-contaminated sediment as compared to the controls during the early successional stages, indicating the harmful effects of industrial wastes on recolonization and succession of macrobenthos. Although no significant differences in community parameters between the industrial-contaminated and the control sediments were found after eleven months, significant difference in species composition still existed after fourteen months, showing a relatively long-term impact of industrial wastes on macrobenthic community structure.

Numerical modeling of salt marsh morphological change induced by Hurricane Sandy

USGS Publications Warehouse

Hu, Kelin; Chen, Qin; Wang, Hongqing; Hartig, Ellen K.; Orton, Philip M.

2018-01-01

The salt marshes of Jamaica Bay serve as a recreational outlet for New York City residents, mitigate wave impacts during coastal storms, and provide habitat for critical wildlife species. Hurricanes have been recognized as one of the critical drivers of coastal wetland morphology due to their effects on hydrodynamics and sediment transport, deposition, and erosion processes. In this study, the Delft3D modeling suite was utilized to examine the effects of Hurricane Sandy (2012) on salt marsh morphology in Jamaica Bay. Observed marsh elevation change and accretion from rod Surface Elevation Tables and feldspar Marker Horizons (SET-MH) and hydrodynamic measurements during Hurricane Sandy were used to calibrate and validate the wind-waves-surge-sediment transport-morphology coupled model. The model results agreed well with in situ field measurements. The validated model was then used to detect salt marsh morphological change due to Sandy across Jamaica Bay. Model results indicate that the island-wide morphological changes in the bay's salt marshes due to Sandy were in the range of −30 mm (erosion) to +15 mm (deposition), and spatially complex and heterogeneous. The storm generated paired deposition and erosion patches at local scales. Salt marshes inside the west section of the bay showed erosion overall while marshes inside the east section showed deposition from Sandy. The net sediment amount that Sandy brought into the bay is only about 1% of the total amount of reworked sediment within the bay during the storm. Numerical experiments show that waves and vegetation played a critical role in sediment transport and associated wetland morphological change in Jamaica Bay. Furthermore, without the protection of vegetation, the marsh islands of Jamaica Bay would experience both more erosion and less accretion in coastal storms.

Comparison of wastewater-associated contaminants in the bed sediment of Hempstead Bay, New York, before and after Hurricane Sandy

USGS Publications Warehouse

Fisher, Shawn C.; Phillips, Patrick J.; Brownawell, Bruce J.; Browne, James

2016-01-01

Changes in bed sediment chemistry of Hempstead Bay (HB) have been evaluated in the wake of Hurricane Sandy, which resulted in the release of billions of liters of poorly-treated sewage into tributaries and channels throughout the bay. Surficial grab samples (top 5 cm) collected before and (or) after Hurricane Sandy from sixteen sites in HB were analyzed for 74 wastewater tracers and steroid hormones, and total organic carbon. Data from pre- and post-storm comparisons of the most frequently detected wastewater tracers and ratios of steroid hormone and of polycyclic aromatic hydrocarbon concentrations indicate an increased sewage signal near outfalls and downstream of where raw sewage was discharged. Median concentration of wastewater tracers decreased after the storm at sites further from outfalls. Overall, changes in sediment quality probably resulted from a combination of additional sewage inputs, sediment redistribution, and stormwater runoff in the days to weeks following Hurricane Sandy.

Comparison of wastewater-associated contaminants in the bed sediment of Hempstead Bay, New York, before and after Hurricane Sandy.

PubMed

Fisher, Shawn C; Phillips, Patrick J; Brownawell, Bruce J; Browne, James P

2016-06-30

Changes in bed sediment chemistry of Hempstead Bay (HB) have been evaluated in the wake of Hurricane Sandy, which resulted in the release of billions of liters of poorly-treated sewage into tributaries and channels throughout the bay. Surficial grab samples (top 5cm) collected before and (or) after Hurricane Sandy from sixteen sites in HB were analyzed for 74 wastewater tracers and steroid hormones, and total organic carbon. Data from pre- and post-storm comparisons of the most frequently detected wastewater tracers and ratios of steroid hormone and of polycyclic aromatic hydrocarbon concentrations indicate an increased sewage signal near outfalls and downstream of where raw sewage was discharged. Median concentration of wastewater tracers decreased after the storm at sites further from outfalls. Overall, changes in sediment quality probably resulted from a combination of additional sewage inputs, sediment redistribution, and stormwater runoff in the days to weeks following Hurricane Sandy. Published by Elsevier Ltd.

Estuaries as Filters: The Role of Tidal Marshes in Trace Metal Removal

PubMed Central

Teuchies, Johannes; Vandenbruwaene, Wouter; Carpentier, Roos; Bervoets, Lieven; Temmerman, Stijn; Wang, Chen; Maris, Tom; Cox, Tom J. S.; Van Braeckel, Alexander; Meire, Patrick

2013-01-01

Flux calculations demonstrate that many estuaries are natural filters for trace metals. Yet, the underlying processes are poorly investigated. In the present study, it was hypothesized that intertidal marshes contribute significantly to the contaminant filter function of estuaries. Trace metal concentrations and sediment characteristics were measured along a transect from the subtidal, over an intertidal flat and marsh to a restored marsh with controlled reduced tide. Metal concentrations in the intertidal and restored marsh were found to be a factor two to five higher than values in the subtidal and intertidal flat sediments. High metal concentrations and high accretion rates indicate a high metal accumulation capacity of the intertidal marshes. Overbank sedimentation in the tidal marshes of the entire estuary was calculated to remove 25% to 50% of the riverine metal influx, even though marshes comprise less than 8% of the total surface of the estuary. In addition, the large-scale implementation of planned tidal marsh restoration projects was estimated to almost double the trace metal storage capacity of the present natural tidal marshes in the estuary. PMID:23950927

Managing Environmental Stress: An Evaluation of Environmental Management of the Long Point Sandy Barrier, Lake Erie, Canada.

PubMed

Kreutzwiser; Gabriel

2000-01-01

/ This paper assesses the extent to which key geomorphic components, processes, and stresses have been reflected in the management of a coastal sandy barrier environment. The management policies and practices of selected agencies responsible for Long Point, a World Biosphere Reserve along Lake Erie, Canada, were evaluated for consistency with these principles of environmental management for sandy barriers: maintaining natural stresses essential to sandy barrier development and maintenance;protecting sediment sources, transfers, and storage; recognizing spatial variability and cyclicity of natural stresses, such as barrier overwash events; and accepting and planning for long-term evolutionary changes in the sandy barrier environment. Generally, management policies and practices have not respected the dynamic and sensitive environment of Long Point because of limited mandates of the agencies involved, inconsistent policies, and failure to apply or enforce existing policies. This is particularly evident with local municipalities and less so for the Canadian Wildlife Service, the federal agency responsible for managing National Wildlife Areas at the point. In the developed areas of Long Point, landward sediment transfers and sediment storage in dunes have been impacted by cottage development, shore protection, and maintenance of roads and parking lots. Additionally, agencies responsible for managing Long Point have no jurisdiction over sediment sources as far as 95 km away. Evolutionary change of sandy barriers poses the greatest challenge to environmental managers.

Regional Sediment Management Studies of Matagorda Ship Channel and Matagorda Bay System, Texas

DTIC Science & Technology

2013-08-01

types of sediment, as there is more silt and clay (cohesive) material in the Lavaca Bay and upper Matagorda Bay and sandy (non- cohesive) sediment in the...Sediment varies from silt to clay in the upper and mid bays and sandy material in the lower bay. 2.5 Dredging History The SWG maintains the deep...diameter  clay mineralogy  rate of deformation (shear rate)  percentage of organic material  water chemistry (especially pH, salinity, etc

Coastal lithofacies and biofacies associated with syndepositional dolomitization and silicification (Draken Formation, Upper Riphean, Svalbard).

PubMed

Fairchild, I J; Knoll, A H; Swett, K

1991-01-01

The Draken Formation (120-250 m) of northeast Spitsbergen (Svalbard) forms part of a thick Upper Proterozoic carbonate platform succession. It consists predominantly of intraformational dolomitic conglomerates, with excellent textural preservation. Six main lithofacies were recognized in the field: quartz sandstones, stromatolitic mats, conglomerates with silicified intraclasts, dolostone conglomerates with desiccated mudrocks, oolitic/pisolitic grainstones and fenestral dolostones. A series of five main gradational biofacies were recognized from silicified (and rare calcified) microfossils. Biofacies 1 represents low-energy subtidal benthos (erect filaments) and plankton (acritarchs and vase-shaped microfossils) whereas biofacies 2 to 5 are microbial mat assemblages (with filamentous mat-builders, and associated dwellers and washed-in plankton) ranging from basal intertidal to high intertidal/supratidal. Colour values (a measure of the lightness of the colour shade) of sawn rock samples were quantified using a Munsell chart, and exhibit a pronounced variation (means of major groups varying from 4.0 to 5.95) across the spectrum of subtidal to supratidal sediments as inferred from other criteria. The lightening in progressively more exposed sediments is related to lowering of organic carbon contents, probably mainly by oxidation. Six types of early cement have been recognized. Calcite microspar (type 1) is common as a subtidal cement in many Proterozoic formations, whereas types 2 (subtidal isopachous fringes), 3 (subtidal hardground dolomicrite) and 4 (intertidal meniscus dolomicrite) are very similar to Phanerozoic examples except for their dolomitic mineralogy. Types 5 and 6 are complex and variable dolomite growths associated with expansion and replacive phenomena. They characterize the fenestral lithofacies and compare with modern supratidal cements. Consideration of diagenetic fabrics and truncation textures of intraclasts indicates that leaching, dolomitization, silicification were all significant syndepositional processes altering the original metastable carbonates. The data set provides evidence for a spectrum of peritidal environments including ooid shoals, protected subtidal, tidal sandflats and protected carbonate mudflats. Different sections show a preponderance of particular facies. The coastal lithofacies continuum was completely dolomitized, unlike offshore to ooid shoal facies of adjacent formations. Dolomitization thus bears a relationship to depositional bathymetry. Although hydrodynamics clearly have a role, the potential importance of whiting precipitation in raising Mg/Ca in marginal marine environments is also stressed.

Coastal lithofacies and biofacies associated with syndepositional dolomitization and silicification (Draken Formation, Upper Riphean, Svalbard)

NASA Technical Reports Server (NTRS)

Fairchild, I. J.; Knoll, A. H.; Swett, K.

1991-01-01

The Draken Formation (120-250 m) of northeast Spitsbergen (Svalbard) forms part of a thick Upper Proterozoic carbonate platform succession. It consists predominantly of intraformational dolomitic conglomerates, with excellent textural preservation. Six main lithofacies were recognized in the field: quartz sandstones, stromatolitic mats, conglomerates with silicified intraclasts, dolostone conglomerates with desiccated mudrocks, oolitic/pisolitic grainstones and fenestral dolostones. A series of five main gradational biofacies were recognized from silicified (and rare calcified) microfossils. Biofacies 1 represents low-energy subtidal benthos (erect filaments) and plankton (acritarchs and vase-shaped microfossils) whereas biofacies 2 to 5 are microbial mat assemblages (with filamentous mat-builders, and associated dwellers and washed-in plankton) ranging from basal intertidal to high intertidal/supratidal. Colour values (a measure of the lightness of the colour shade) of sawn rock samples were quantified using a Munsell chart, and exhibit a pronounced variation (means of major groups varying from 4.0 to 5.95) across the spectrum of subtidal to supratidal sediments as inferred from other criteria. The lightening in progressively more exposed sediments is related to lowering of organic carbon contents, probably mainly by oxidation. Six types of early cement have been recognized. Calcite microspar (type 1) is common as a subtidal cement in many Proterozoic formations, whereas types 2 (subtidal isopachous fringes), 3 (subtidal hardground dolomicrite) and 4 (intertidal meniscus dolomicrite) are very similar to Phanerozoic examples except for their dolomitic mineralogy. Types 5 and 6 are complex and variable dolomite growths associated with expansion and replacive phenomena. They characterize the fenestral lithofacies and compare with modern supratidal cements. Consideration of diagenetic fabrics and truncation textures of intraclasts indicates that leaching, dolomitization, silicification were all significant syndepositional processes altering the original metastable carbonates. The data set provides evidence for a spectrum of peritidal environments including ooid shoals, protected subtidal, tidal sandflats and protected carbonate mudflats. Different sections show a preponderance of particular facies. The coastal lithofacies continuum was completely dolomitized, unlike offshore to ooid shoal facies of adjacent formations. Dolomitization thus bears a relationship to depositional bathymetry. Although hydrodynamics clearly have a role, the potential importance of whiting precipitation in raising Mg/Ca in marginal marine environments is also stressed.

Temporally Dynamic, Spatially Static, Cobble Bedforms In Reversing Subtidal Currents

NASA Astrophysics Data System (ADS)

Abdulkade, Akirat; Carling, Paul; Zong, Quanli; Leyland, Julian; Thompson, Charlie

2016-04-01

Cobble bedforms, transverse to the reversing tidal currents, are exposed at extreme low-water Spring tides on an inter-tidal bedrock shelf in the macro-tidal Severn Estuary, UK. Near-bed flow velocities during Spring tides can exceed 1.5m/s, with water depths varying from zero to in excess of 10m. During neap tides the bedforms are not exposed, and sediment is expected to be of limited mobility. When exposed, the bedform geometry tends to be asymmetric; orientated down estuary with the ebb current. During Spring tides, vigorous bedload transport of gravel (including large cobbles) occurs during both flood and ebb over the crests and yet, despite this temporal dynamism, the bedforms remain spatially static over long time periods or show weak down-estuary migration. Stasis implies that the tidal bedload transport vectors are essentially in balance. Near-bed shear stress and bed roughness values vary systematically with the Spring-tide current speeds and the predicted grain-size of the bed load using the Shields criterion is in accord with observed coarser grain-sizes in transport. These hydrodynamic data, delimited by estimates of the threshold of motion, and integrated over either flood or ebb tides are being used to explain the apparent stability of the bedforms. The bulk hydraulic data are supplemented by particle tracer studies and laser-scanning of bed configurations between tides. The high-energy environment results in two forms of armouring. Pronounced steep imbrication of platy-cobbles visible on the exposed up-estuary side of dunes is probably disrupted during flood tides leading to rapid reworking of the toe deposits facing up-estuary. In contrast, some crest and leeside locations have been stable for prolonged periods such that closely-fitted fabrics result; these portions of the bedforms are static and effectively are 'armour-plated'. Ebb-tide deposits of finer, ephemeral sandy-units occur on the down estuary side of the bedforms. Sandy-units (although not observed at low tide) presumably also are deposited on the up estuary side during flooding tides but these deposits are destroyed by ebb flows. The implication of these sediment transport processes on the stratification of the bedforms is considered.

Sediment Transport and Slope Stability of Ship Shoal Borrow Areas for Coastal Restoration of Louisiana

NASA Astrophysics Data System (ADS)

Liu, H.; Xu, K.; Bentley, S. J.; Li, C.; Miner, M. D.; Wilson, C.; Xue, Z.

2017-12-01

Sandy barrier islands along Louisiana coast are degrading rapidly due to both natural and anthropogenic factors. Ship Shoal is one of the largest offshore sand resources, and has been used as a borrow area for Caminada Headland Restoration Project. Our knowledge of sediment transport and infilling processes in this new sandy and dynamic borrow area is rather limited. High resolution sub-bottom seismic data, side scan sonar images, multi-beam bathymetry and laser sediment grain size data were used to study seafloor morphological evolution and pit wall stability in response to both physical and geological processes. The multi-beam bathymetry and seismic profiling inside the pit showed that disequilibrium conditions led to rapid infilling in the pits at the beginning, but this process slowed down after the pit slope became stable and topography became smooth. We hypothesize that the erosion of the adjacent seabed sediment by energetic waves and longshore currents, the supply of suspended sediment from the rivers, and the erodible materials produced by local mass wasting on pit walls are three main types of infilling sediments. Compared with mud-capped dredge pits, this sandy dredge pit seems to have more gentle slopes on pit walls, which might be controlled by the angle of repose. Infilling sediment seems to be dominantly sandy, with some mud patches on bathymetric depressions. This study helps us better understand the impacts of mining sediment for coastal restoration and improves sand resource management efforts.

A model to understand the confounding effects of natural sediments in toxicity tests with Chironomus riparius.

PubMed

Péry, Alexandre R; Sulmon, Vanessa; Mons, Raphaël; Flammarion, Patrick; Lagadic, Laurent; Garric, Jeanne

2003-10-01

Recently, we built a model to link feeding input with growth, emergence, and reproduction of the midge Chironomus riparius exposed to an artificial sandy sediment. This model is based on assumptions about both feeding behavior and use of energy. Here, we show how it can be used for toxicity tests with natural sediments to understand and model the influence of sediment characteristics. We measured growth, emergence, and reproduction of chironomids exposed in beakers to four unpolluted natural sediments and three feeding conditions (no feeding, 0.2 mg Tetramin/larva/d, and 1.4 mg Tetramin/larva/d) and compared the results with data obtained on our artificial sandy sediment. Sediment characteristics had lower influence on growth than feeding level, but their influence could not be neglected. First, we could distinguish between sandy sediments and other sediments. This difference resulted in a significant delay of about 18 h in the growth curves. Second, in case of food limitation, chironomids could use the organic materials in the sediment, provided that the C:N ratio of the sediment was less than 14. Our model proved to be able to incorporate those two phenomena. As for reproduction, we observed a better reproduction (measured in number of eggs per mass) for natural sediments than for artificial sediments. We showed that this difference could be due to the lipid content of the natural sediments.

Spongy-like porosity in peritidal carbonates: An interaction of cyclic sea-level oscillations, fresh water supply and sediment texture

NASA Astrophysics Data System (ADS)

Todaro, S.; Hollis, C.; Di Stefano, P.

2016-03-01

This paper focuses upon the analysis of a complex paleokarstic system recorded within uppermost Triassic peritidal cycles in northwestern Sicily. Besides documenting spectacular karstification at the Triassic/Jurassic boundary, it provides an example of stratabound 'spongy' or 'swiss-cheese' dissolution. On the base of field observations, microfacies analysis, transmitted-light and cathodoluminescence petrography and stable-isotope analyses we put forward an original model for the formation of this peculiar stratabound dissolution. It implies a complex interaction of several controlling factors at the interface between the marine and meteoric diagenetic realms during the relative cyclic oscillations of sea-level. The presence of a fresh water supply from an adjacent emerged area is the key for the periodic formation of a mixing water lens during the relative sea level lowstand that brought about the subaerial exposure of the platform. The resulting dissolution pattern in the subtidal unit of a specific cycle is strongly controlled by the textural features of the sediments. In the case of bioturbated wackestones the 'spongy' or 'swiss-cheese' pattern develops, while in mollusk-rich beds biomoldic porosity occurs. In well-sorted subtidal members, such as algal grainstones, the dissolution originates as randomly distributed vuggy porosity. During periodic flooding of the platform, a new subtidal unit is formed and the dissolution stops as fully marine phreatic conditions are re-established.

Zonation and structuring factors of meiofauna communities in a tropical seagrass bed (Gazi Bay, Kenya)

NASA Astrophysics Data System (ADS)

De Troch, Marleen; Gurdebeke, Shirley; Fiers, Frank; Vincx, Magda

2001-02-01

This study deals with the relation between tropical meiofauna and environmental variables by comparing the 'benthic' (i.e. in the bare sediment adjacent to seagrass plants) and the 'epiphytic' (i.e. in samples including seagrass plants) meiofauna associated with five seagrass species from the high intertidal to the high subtidal zone in Gazi Bay (Kenya). Ordination and variance analysis revealed three distinct 'benthic' and two 'epiphytic' meiofauna assemblages. These assemblages corresponded entirely with those identified for the seagrass species: a high intertidal pioneer association ( Halophila ovalis/ Halodule wrightii), an intertidal climax assemblage ( Thalassia hemprichii) and a high subtidal pioneer association ( Halophila stipulacea/ Syringodium isoetifolium). These data support the hypothesis that meiofaunal communities correspond to the characteristic zonation of the seagrass vegetation in Gazi Bay. In beds of the pioneer seagrass species, the close relationship between sediment characteristics and both 'benthic' and 'epiphytic' meiofauna communities suggests that these pioneer communities were mainly driven by physical factors. The 'benthic' communities adjacent to the climax seagrass species T. hemprichii were more structured by biogenic factors, e.g. % TOM, chlorophyll a and c, fucoxanthin, habitat complexity and growth form of the seagrass species. For its associated 'epiphytic' meiofauna the latter conclusion was even more striking. These data corroborate the importance of physical factors in disturbed environments (intertidal zone, near pioneer seagrasses) and of biotic factors in more stable conditions (subtidal zone, near climax seagrasses).

Sea otter studies in Glacier Bay National Park and Preserve: annual report 2002

USGS Publications Warehouse

Bodkin, James L.; Kloecker, Kimberly A.; Esslinger, George G.; Monson, Daniel H.; Coletti, Heather A.; Doherty, Janet

2003-01-01

Since 1995, the number of sea otters in Glacier Bay proper has increased from around 5 to more than 1200. Sea otter distribution is mostly limited to the Lower Bay, south of Sandy Cove, and is not continuous within that area. Concentrations occur in the vicinity of Sita Reef and Boulder Island and between Pt. Carolus and Rush Pt. on the west side of the Bay, although there have been occasional sightings north of Sandy Cove (Figure 1). Large portions of the Bay remain unoccupied by sea otters, but recolonization is occurring rapidly. Most prey recovered by sea otters in Glacier Bay are ecologically, commercially, or socially important species. In 2002 sea otter diet consisted of 35% clam, 26% mussel, 3% crab, 3.0% snail, 2% starfish, 11% urchins, 2% other, and 20% unidentified. Dominant clam species include the butter clam, Saxidomus gigantea, the Greenland cockle, Serripes groenlandicus, and the littleneck clam, Protothaca staminea. Urchins are primarily green urchins, Strongylocentrotus droebachiensis, and the mussel is Modiolus modiolus. Crabs observed in 2002 include the Dungeness, Cancer magister, the kelp crab Pugettia gracilis, and the helmet crab, Telmessus cherigonus. Although we characterize diet at broad geographic scales, we have previously found diet to vary between sites separated by as little as several hundred meters. Dietary variation among and within sites can reflect differences in prey availability as well as individual specialization. We estimated species composition, density, biomass, and sizes of subtidal clams, urchins, and mussels at 13 sites in Glacier Bay and 5 sites in nearby Port Althorp, where sea otters have been present for at least 20 years. All sites were selected based on the presence of abundant clam siphons and the absence of sea otters (Glacier Bay) or abundant shell litter and the presence of sea otters (Port Althorp). Glacier Bay sites were selected to achieve a broad geographic sample of dense subtidal clam beds within Glacier Bay prior to occupation and foraging by sea otters. Port Althorp sites were chosen to achieve a representative sample of subtidal clam beds already under prolonged foraging pressure by sea otters. There was no direct evidence of otter foraging at any of our Glacier Bay sampling sites. In Glacier Bay, we sampled 15,338 bivalves (average of 1,180/site) representing 14 species of clam, 2 species of mussel, and a single scallop and we sampled 6,917 urchins (average of 513/site). In Port Althorp, we sampled 1,034 bivalves (average of 207/site) representing 14 species of clam. We found only 5 urchins, all S. droebachiensis. Mean densities and biomass of all subtidal clams were significantly greater in Glacier Bay (59.2 and 99/0.25m2 compared to Port Althorp (10.3 and 5.8/0.25m2 (p Our contrasts of subtidal clam populations between Glacier Bay and Port Althorp suggest that clam densities will likely decline by about a factor of six and that clam biomass estimates will decline by more than a factor of ten. Numerically dominant species of clams, P. staminea, S. gigantea, Macoma sp. and Mya sp. were all significantly greater in density and biomass in Glacier Bay, while C. nutalli density was low but significantly higher in Port Althorp. Subtidal clam species diversity was significantly greater in Port Althorp compared to Glacier Bay, although this may simply reflect habitat differences. Sea urchin densities were high in Glacier Bay, while in Port Althorp urchins were virtually absent. Sea otters are now well established in limited areas of the lower portions of Glacier Bay. It is likely that distribution and numbers of sea otters will continue to increase in Glacier Bay in the near future. Glacier Bay supports large and diverse populations of clams that are largely unexploited by sea otters at present. It is predictable that the density and sizes of clam populations will decline in response to otter predation. This will result in fewer opportunities for human harvest, but will also trigger ecosystem level changes, as prey for other predators, such as octopus, sea stars, fishes, birds and mammals are modified. Sea otters will also modify benthic habitats through excavation of sediments required to extract burrowing infauna such as clams. Effects of sediment disturbance by foraging sea otters are not understood. Glacier Bay also supports large populations of other preferred sea otter prey, such as king (Paralithodes sp.), tanner (Chionoecetes sp.) and dungeness (Cancer magister) crabs and green sea urchins (S. droebachiensis). As the colonization of Park waters by sea otters continues, it is also likely that dramatic changes will occur in the species composition, abundance, and size class distribution of many components of the nearshore marine ecosystem. Many of the changes will occur as a direct result of predation by sea otters. Others will result from indirect or cascading effects of sea otter foraging, such as increased kelp production and modified prey availability for other nearshore predators. Without recognizing and quantifying the extent of change initiated by the colonization of Glacier Bay by sea otters, management of nearshore resources will be severely constrained for many decades.

Thriving reefs in the Baltic? Diversity and small-scale variability of hard-bottom assemblages along natural and anthropogenic gradients in the German Baltic Sea

NASA Astrophysics Data System (ADS)

Beisiegel, K.; Zettler, M. L.; Darr, A.; Schiele, K.; Schwarzer, K.; Richter, P.

2016-02-01

Since the vast majority of global seafloor habitats are characterized by soft sediments, hard substrata represent rarities hosting species and functional groups not found elsewhere. The same holds true for the enclosed and brackish Baltic Sea, where hard substrata occur patchy and infrequent. Subtidal low-relief terrains with homogenous mud and sand flats form the predominant benthic substrate and the associated infaunal communities are well described. In contrast, the diverse, primarily epibenthic assemblages on subtidal hard bottoms received far less attention. Since 2011 a team of geologists and biologists aims to map the subtidal habitats and biotopes. On joint cruises, geologists use side scan sonar to map the seafloor sediments while ground truthing is performed in collaboration with biologists. Biogenic concretions like mussel beds and hard structures of geogenic origin like stones and glacial boulders form the predominant hard substrata in the German Baltic Sea. These habitats are subsequently investigated using frame sampling by SCUBA diving, dredges or towed photo/video platforms. The type of hard substratum, salinity and light availability seem to be the most important natural factors that determine the epibenthic community composition. Identified geological substrata and biological communities are matched with biotopes of the HELCOM Underwater biotope and habitat classification system. Predictive modeling approaches are used to generate biotope specific distribution patterns, based on biological point samples, area-wide sediment distribution maps and measured/modeled environmental parameters. The resulting hard-bottom biotope maps, combining geological and biological information, complement the existing area-wide biotope map of soft sediment communities. The maps are important tools both for the scientific community to understand the functioning of marine ecosystems as well as for nature conservation, e.g. for the implementation of MPA management plans and for the development of monitoring concepts and the red list classification of biotopes.

The Role of the Sedimentary Regime in Shaping the Distribution of Subtidal Sandbank Environments and the Associated Meiofaunal Nematode Communities: An Example from the Southern North Sea

PubMed Central

Schratzberger, Michaela; Larcombe, Piers

2014-01-01

We combined sediment and faunal data to explore the role of the sedimentary regime in shaping the distribution of subtidal sandbank environments and the associated meiofaunal nematode communities at Broken Bank and Swarte Bank, in the southern North Sea. A variety of sediment transport processes occur in the area, differing in the frequency and magnitude of sediment mobility, and the continuum between erosion, translation and sediment accumulation. The seabed contained a variety of bedforms, including longitudinal furrows, and small to very large sandwaves. The bed sediments were dominated by fine and medium sands, with admixtures of silt and gravel. Based on sedimentary bedforms and grain size analysis, a total of 11 sedimentary facies were delineated, of which 8 were analysed in detail for their relationships with the meiofauna. The sedimentary facies fell clearly into groups of facies, respectively representing high, high-moderate and moderate, and episodic sediment mobility. For those sedimentary facies where daily movement of sediments and bedforms occurred (‘high’ sediment mobility), the resulting spatially homogeneous environments were dominated by an impoverished nematode community comprising small deposit feeders and large predators. Resistance to sediment movement and the ability to exploit alternative food sources were prominent functional features of the successful colonisers. Those facies characterised by relatively infrequent sediment mobility (‘episodic’ and ‘high-moderate and moderate’ sediment mobility) comprised a heterogeneous suite of benthic habitats, containing taxonomically and functionally diverse assemblages of nematodes of various sizes, feeding types and reproductive potential. Faunal distribution patterns here indicated trade-offs between the resistance to sediment movement, environmental tolerance and competitive abilities. Our focus on diverse assemblages of organisms with high turnover times, inhabiting highly dynamic sedimentary environments, has revealed new animal-sediment relationships of relevance to pure and applied science. PMID:25296029

Eruption-related lahars and sedimentation response downstream of Mount Hood: Field guide to volcaniclastic deposits along the Sandy River, Oregon

USGS Publications Warehouse

Pierson, Tom C.; Scott, William E.; Vallance, James W.; Pringle, Patrick T.; O'Connor, Jim; Dorsey, Rebecca; Madin, Ian

2009-01-01

Late Holocene dome-building eruptions at Mount Hood during the Timberline and Old Maid eruptive periods resulted in numerous dome-collapse pyroclastic flows and lahars that moved large volumes of volcaniclastic sediment into temporary storage in headwater canyons of the Sandy River. During each eruptive period, accelerated sediment loading to the river through erosion and remobilization of volcanic fragmental debris resulted in very high sediment-transport rates in the Sandy River during rain- and snowmelt-induced floods. Large sediment loads in excess of the river's transport capacity led to channel aggradation, channel widening, and change to a braided channel form in the lowermost reach of the river, between 61 and 87 km downstream from the volcano. The post-eruption sediment load moved as a broad bed-material wave, which in the case of the Old Maid eruption took ~2 decades to crest 83 km downstream. Maximum post-eruption aggradation levels of at least 28 and 23 m were achieved in response to Timberline and Old Maid eruptions. In each case, downstream aggradation cycles were initiated by lahars, but the bulk of the aggradation was achieved by fluvial sediment transport and deposition. When the high rates of sediment supply began to diminish, the river degraded, incising the channel fills and forming progressively lower sets of degradational terraces. A variety of debris-flow, hyperconcentrated-flow, and fluvial (upper and lower flow regime) deposits record the downstream passage of the sediment waves that were initiated by these eruptions. The deposits also presage a hazard that may be faced by communities along the Sandy River when volcanic activity at Mount Hood resumes.

Regional variability in bed-sediment concentrations of wastewater compounds, hormones and PAHs for portions of coastal New York and New Jersey impacted by hurricane Sandy

USGS Publications Warehouse

Phillips, Patrick J.; Gibson, Cathy A; Fisher, Shawn C.; Fisher, Irene; Reilly, Timothy J.; Smalling, Kelly L.; Romanok, Kristin M.; Foreman, William T.; ReVello, Rhiannon C.; Focazio, Michael J.; Jones, Daniel K.

2016-01-01

Bed sediment samples from 79 coastal New York and New Jersey, USA sites were analyzed for 75 compounds including wastewater associated contaminants, PAHs, and other organic compounds to assess the post-Hurricane Sandy distribution of organic contaminants among six regions. These results provide the first assessment of wastewater compounds, hormones, and PAHs in bed sediment for this region. Concentrations of most wastewater contaminants and PAHs were highest in the most developed region (Upper Harbor/Newark Bay, UHNB) and reflected the wastewater inputs to this area. Although the lack of pre-Hurricane Sandy data for most of these compounds make it impossible to assess the effect of the storm on wastewater contaminant concentrations, PAH concentrations in the UHNB region reflect pre-Hurricane Sandy conditions in this region. Lower hormone concentrations than predicted by the total organic carbon relation occurred in UHNB samples, suggesting that hormones are being degraded in the UHNB region.

Regional variability in bed-sediment concentrations of wastewater compounds, hormones and PAHs for portions of coastal New York and New Jersey impacted by hurricane Sandy.

PubMed

Phillips, Patrick J; Gibson, Catherine A; Fisher, Shawn C; Fisher, Irene J; Reilly, Timothy J; Smalling, Kelly L; Romanok, Kristin M; Foreman, William T; ReVello, Rhiannon C; Focazio, Michael J; Jones, Daniel K

2016-06-30

Bed sediment samples from 79 coastal New York and New Jersey, USA sites were analyzed for 75 compounds including wastewater associated contaminants, PAHs, and other organic compounds to assess the post-Hurricane Sandy distribution of organic contaminants among six regions. These results provide the first assessment of wastewater compounds, hormones, and PAHs in bed sediment for this region. Concentrations of most wastewater contaminants and PAHs were highest in the most developed region (Upper Harbor/Newark Bay, UHNB) and reflected the wastewater inputs to this area. Although the lack of pre-Hurricane Sandy data for most of these compounds make it impossible to assess the effect of the storm on wastewater contaminant concentrations, PAH concentrations in the UHNB region reflect pre-Hurricane Sandy conditions in this region. Lower hormone concentrations than predicted by the total organic carbon relation occurred in UHNB samples, suggesting that hormones are being degraded in the UHNB region. Published by Elsevier Ltd.

Numerical modeling of the effects of Hurricane Sandy and potential future hurricanes on spatial patterns of salt marsh morphology in Jamaica Bay, New York City

USGS Publications Warehouse

Wang, Hongqing; Chen, Qin; Hu, Kelin; Snedden, Gregg A.; Hartig, Ellen K.; Couvillion, Brady R.; Johnson, Cody L.; Orton, Philip M.

2017-03-29

The salt marshes of Jamaica Bay, managed by the New York City Department of Parks & Recreation and the Gateway National Recreation Area of the National Park Service, serve as a recreational outlet for New York City residents, mitigate flooding, and provide habitat for critical wildlife species. Hurricanes and extra-tropical storms have been recognized as one of the critical drivers of coastal wetland morphology due to their effects on hydrodynamics and sediment transport, deposition, and erosion processes. However, the magnitude and mechanisms of hurricane effects on sediment dynamics and associated coastal wetland morphology in the northeastern United States are poorly understood. In this study, the depth-averaged version of the Delft3D modeling suite, integrated with field measurements, was utilized to examine the effects of Hurricane Sandy and future potential hurricanes on salt marsh morphology in Jamaica Bay, New York City. Hurricane Sandy-induced wind, waves, storm surge, water circulation, sediment transport, deposition, and erosion were simulated by using the modeling system in which vegetation effects on flow resistance, surge reduction, wave attenuation, and sedimentation were also incorporated. Observed marsh elevation change and accretion from a rod surface elevation table and feldspar marker horizons and cesium-137- and lead-210-derived long-term accretion rates were used to calibrate and validate the wind-waves-surge-sediment transport-morphology coupled model.The model results (storm surge, waves, and marsh deposition and erosion) agreed well with field measurements. The validated modeling system was then used to detect salt marsh morphological change due to Hurricane Sandy across the entire Jamaica Bay over the short-term (for example, 4 days and 1 year) and long-term (for example, 5 and 10 years). Because Hurricanes Sandy (2012) and Irene (2011) were two large and destructive tropical cyclones which hit the northeast coast, the validated coupled model was run to predict the effects of Sandy-like and Irene-like hurricanes with different storm tracks and wind intensities on wetland morphology in Jamaica Bay. Model results indicate that, in Jamaica Bay salt marshes, the morphological changes (greater than 5 millimeters [mm] determined by the long-term marsh accretion rate) caused by Hurricane Sandy were complex and spatially heterogeneous. Most of the erosion (5–40 mm) and deposition (5–30 mm) were mainly characterized by fine sand for channels and bay bottoms and by mud for marsh areas. Hurricane Sandy-generated deposition and erosion were generated locally. The storm-induced net sediment input through Rockaway Inlet was only about 1 percent of the total amount of the sediment reworked by the hurricane. Salt marshes inside the western part of the bay showed erosion overall while marshes inside the eastern part showed deposition from Hurricane Sandy. Model results indicated that most of the marshes could recover from Hurricane Sandy-induced erosion after 1 year and demonstrated continued marsh accretion after the hurricane over the course of long simulation periods although the effect (accretion) was diminished. Local waves and currents generated by Hurricane Sandy appeared to play a critical role in sediment transport and associated wetland morphological change in Jamaica Bay. Hypothetical hurricanes, depending on their track and intensity, cause variable responses in spatial patterns of sediment deposition and erosion compared to simulations without the hurricane. In general, hurricanes passing west of the Jamaica Bay estuary appear to be more destructive to the salt marshes than those passing the east. Consequently, marshes inside the western part of the bay were likely to be more vulnerable to hurricanes than marshes inside the eastern part of the bay. 

Patterns of species diversity in estuarine benthic communities along teh US west coast

EPA Science Inventory

Estuaries in the Pacific North West (PNW) were recently classified by whether the estuary is river- or ocean-dominated, the extent of intertidal to subtidal environments, and spatial salinity patterns. We examine whether these characteristics predict patterns of soft-sediment, m...

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

O`Clair, C.E.; Short, J.W.; Rice, S.D.

To determine the distribution of oil in subtidal sediments after the Exxon Valdez oil spill we sampled sediments at six depths (0, 3, 6, 20, 40 and 100 m) at 53 locations in Prince William Sound and the northern Gulf of Alaska from 1989 to 1991. Results are based on 1278 sediment samples analyzed by gas chromatography/mass spectrometry. In 1989, the oil concentration was greatest in the Sound at 0 m. Outside the Sound, Exxon Valdez oil occurred at Chugach Bay, Hallo Bay, Katmai Bay, and Windy Bay in 1989. Hydrocarbons often matched Exxon Valdez oil less closely, oil wasmore » more patchily distributed, and the oil concentration decreased in sediments after 1989.« less

Evolution of coastal and marine environments during the Holocene transgression. Ría de Vigo (Galicia, Spain).

NASA Astrophysics Data System (ADS)

Clemente, F.; Pérez-Arlucea, M.; Méndez, G.; Francés, G.; Alejo, I.; González, D.; Nombela, M.

2003-04-01

Coastal deposits are not prominent in the Ria de Vigo, high cliffs dominate the coast line, but several well-preserved sedimentary areas are observed. Beach and aeolian sand dunes are preserved in protected bays along margins between low cliffs, as Playa America, Patos and Samil. Several rivers form prominent estuaries such as the Verdugo-Oitaven, the Minor and the Lagares. Tidal flats are well preserved in the San Simon embayment and small areas of tidal flats and marshes can be found elsewhere associated with estuaries and protected by sandy spits as the Ramallosa tidal Complex, Moaña and San Simón. Four sedimentary areas were selected to study vertical sediment distribution. 6 cores were obtained. Sediment thicknesses range between 4.0m and 26.0 m. Vertical sediment distributions show 6 different lithologic units from basal fluvial (A), estuarine (B), tidal flat and peat fens (C), muddy subtidal bay (D), estuarine (E) and beach barrier (F). 10 14C age determinations were obtained from the longest core (Ladeira N) located at the Ramallosa beach barrier-lagoon complex. The oldest sample located at 22 m yields an age of 8177 y. BP in unit (B) allowing to constrain most of sediment evolution in the holocene transgressive context. The lower unit (A) composed mainly of fluvial gravels, and deposited in a palaeovalley, is attributed to the Younger Dryas although the LST could be also represented in these deposits. Units B, C and D configure the TST showing an initial rapid increase in water depth at 8177 y. BP and subsequent shallowing conditions due to progressive aggradation until 4809 y BP. Units E and F mark the HST eustatic stage being characterised by progradational shallow marine conditions and beach barrier progressive enclosing of the complex. Sedimentation rates were calculated at 7 intervals. An upward decrease is observed from 8177 y BP to 2001 y. BP, followed by a strong sudden increase, mostly in the last 500 years. Hydrology and geomorphology of river catchments were studied to evaluate sediment yields in modern conditions. 19 currents were selected on the basis of having permanent flow during the whole year and a minimum measurable discharge. Results show accelerated erosion and sediment yield which are attributed to anthropogenic causes, chiefly deforestation and soil degradation.

Sedimentary environments within a glaciated estuarine-inner shelf system: Boston Harbor and Massachusetts Bay

USGS Publications Warehouse

Knebel, H.J.

1993-01-01

Three modern sedimentary environments have been identified and mapped across the glaciated Boston Harbor estuary and adjacent inner shelf of Massachusetts Bay by means of an extensive set of sidescan sonar records and supplemental bathymetric, sedimentary, subbottom and bottom-current data. 1. (1) Environments of erosion and nondeposition appear on the sonographs either as patterns with isolated reflections (caused by outcrops of bedrock, glacial drift, and coastal plain rocks) or as patterns of strong backscatter (caused by coarse-grained lag deposits). Sediments in these environments range from boulder fields to gravelly sands with megaripples. Inside the harbor, areas of erosion or nondeposition are found primarily near mainland and insular shores and within constricted tidal channels, whereas, on the shelf, they are present over extensive areas of hummocky topography near the coast and atop local bathymetric highs offshore. 2. (2) Environments of sediment reworking are characterized on the sonographs by patterns with patches of strong to weak backscatter caused by a combination of erosional and depositional processes. These environments have diverse grain sizes that range from sandy gravels to muds. Within the harbor, the locations of reworked sediments are uncorrelated with the bottom topography, but, on the shelf, they are found on the lower flanks of bathymetric highs, within broad lows and in relatively deep water (30-50 m). 3. (3) Environments of deposition are depicted on the sonographs as uniform patterns of weak backscatter. These areas contain relatively fine-grained muddy sands and muds. Inside the harbor, depositional environments are found over extensive subtidal flats and within sheltered depressions, whereas, on the shelf, they are restricted to broad lows mainly in deep water. The extreme patchiness of modern sedimentary environments within the Boston Harbor-Massachusetts Bay system reflects the interaction between the irregular bottom topography and both geologic and oceanographic processes. The estuarine part of the system is an effective trap for fine-grained detritus because of its protected nature, low wave climate, and large supply of sediments. The open shelf, however, is largely mantled by winnowed and sorted sediments as a result of erosion during past sea-level fluctuations, sediment resuspension and transport by modern waves and currents, and a spatially variable supply of fine-grained sediments.

Depositional dynamics in the El'gygytgyn Crater margin: implications for the 3.6 Ma old sediment archive

NASA Astrophysics Data System (ADS)

Schwamborn, G.; Fedorov, G.; Ostanin, N.; Schirrmeister, L.; Andreev, A.; El'gygytgyn Scientific Party, the

2012-11-01

The combination of permafrost history and dynamics, lake level changes and the tectonical framework is considered to play a crucial role for sediment delivery to El'gygytgyn Crater Lake, NE Russian Arctic. The purpose of this study is to propose a depositional framework based on analyses of the core strata from the lake margin and historical reconstructions from various studies at the site. A sedimentological program has been conducted using frozen core samples from the 141.5 m long El'gygytgyn 5011-3 permafrost well. The drill site is located in sedimentary permafrost west of the lake that partly fills the El'gygytgyn Crater. The total core sequence is interpreted as strata building up a progradational alluvial fan delta. Four macroscopically distinct sedimentary units are identified. Unit 1 (141.5-117.0 m) is comprised of ice-cemented, matrix-supported sandy gravel and intercalated sandy layers. Sandy layers represent sediments which rained out as particles in the deeper part of the water column under highly energetic conditions. Unit 2 (117.0-24.25 m) is dominated by ice-cemented, matrix-supported sandy gravel with individual gravel layers. Most of the Unit 2 diamicton is understood to result from alluvial wash and subsequent gravitational sliding of coarse-grained (sandy gravel) material on the basin slope. Unit 3 (24.25-8.5 m) has ice-cemented, matrix-supported sandy gravel that is interrupted by sand beds. These sandy beds are associated with flooding events and represent near-shore sandy shoals. Unit 4 (8.5-0.0 m) is ice-cemented, matrix-supported sandy gravel with varying ice content, mostly higher than below. It consists of slope material and creek fill deposits. The uppermost metre is the active layer (i.e. the top layer of soil with seasonal freeze and thaw) into which modern soil organic matter has been incorporated. The nature of the progradational sediment transport taking place from the western and northern crater margins may be related to the complementary occurrence of frequent turbiditic layers in the central lake basin, as is known from the lake sediment record. Slope processes such as gravitational sliding and sheet flooding occur especially during spring melt and promote mass wasting into the basin. Tectonics are inferred to have initiated the fan accumulation in the first place and possibly the off-centre displacement of the crater lake.

Relationships between microbial communities and environmental parameters at sites impacted by mining of volcanogenic massive sulfide deposits, Prince William Sound, Alaska

USGS Publications Warehouse

Foster, A.L.; Munk, L.; Koski, R.A.; Shanks, Wayne C.; Stillings, L.L.

2008-01-01

The relations among geochemical parameters and sediment microbial communities were examined at three shoreline sites in the Prince William Sound, Alaska, which display varying degrees of impact by acid-rock drainage (ARD) associated with historic mining of volcanogenic massive sulfide deposits. Microbial communities were examined using total fatty acid methyl esters (FAMEs), a class of compounds derived from lipids produced by eukaryotes and prokaryotes (bacteria and Archaea); standard extraction techniques detect FAMEs from both living (viable) and dead (non-viable) biomass, but do not detect Archaeal FAMEs. Biomass and diversity (as estimated by FAMEs) varied strongly as a function of position in the tidal zone, not by study site; subtidal muds, Fe oxyhydroxide undergoing biogenic reductive dissolution, and peat-rich intertidal sediment had the highest values. These estimates were lowest in acid-generating, intertidal zone sediment; if valid, the estimates suggest that only one or two bacterial species predominate in these communities, and/or that Archeal species are important members of the microbial community in this sediment. All samples were dominated by bacterial FAMEs (median value >90%). Samples with the highest absolute abundance of eukaryotic FAMEs were biogenic Fe oxyhydroxides from shallow freshwater pools (fungi) and subtidal muds (diatoms). Eukaryotic FAMEs were practically absent from low-pH, sulfide-rich intertidal zone sediments. The relative abundance of general microbial functional groups such as aerobes/anaerobes and gram(+)/gram(-) was not estimated due to severe inconsistency among the results obtained using several metrics reported in the literature. Principal component analyses (PCAs) were performed to investigate the relationship among samples as separate functions of water, sediment, and FAMEs data. PCAs based on water chemistry and FAMEs data resulted in similar relations among samples, whereas the PCA based on sediment chemistry produced a very different sample arrangement. Specifically, the sediment parameter PCA grouped samples with high bulk trace metal concentration regardless of whether the metals were incorporated into secondary precipitates or primary sulfides. The water chemistry PCA and FAMEs PCA appear to be less prone to this type of artifact. Signature lipids in sulfide-rich sediments could indicate the presence of acid-tolerant and/or acidophilic members of the genus Thiobacillus or they could indicate the presence of SO4-reducing bacteria. The microbial community documented in subtidal and offshore sediments is rich in SRB and/or facultative anaerobes of the Cytophaga-Flavobacterium group; both could reasonably be expected in PWS coastal environments. The results of this study provide evidence for substantial feedback between local (meter to centimeter-scale) geochemical variations, and sediment microbial community composition, and show that microbial community signatures in the intertidal zone are significantly altered at sites where ARD drainage is present relative to sites where it is not, even if the sediment geochemistry indicates net accumulation of ARD-generated trace metals in the intertidal zone. ?? 2007 Elsevier Ltd. All rights reserved.

Study on small-strain behaviours of methane hydrate sandy sediments using discrete element method

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

Yu Yanxin; Cheng Yipik; Xu Xiaomin

Methane hydrate bearing soil has attracted increasing interest as a potential energy resource where methane gas can be extracted from dissociating hydrate-bearing sediments. Seismic testing techniques have been applied extensively and in various ways, to detect the presence of hydrates, due to the fact that hydrates increase the stiffness of hydrate-bearing sediments. With the recognition of the limitations of laboratory and field tests, wave propagation modelling using Discrete Element Method (DEM) was conducted in this study in order to provide some particle-scale insights on the hydrate-bearing sandy sediment models with pore-filling and cementation hydrate distributions. The relationship between shear wavemore » velocity and hydrate saturation was established by both DEM simulations and analytical solutions. Obvious differences were observed in the dependence of wave velocity on hydrate saturation for these two cases. From the shear wave velocity measurement and particle-scale analysis, it was found that the small-strain mechanical properties of hydrate-bearing sandy sediments are governed by both the hydrate distribution patterns and hydrate saturation.« less

Extension of 239+240Pu sediment geochronology to coarse-grained marine sediments

USGS Publications Warehouse

Kuehl, Steven A.; Ketterer, Michael E.; Miselis, Jennifer L.

2012-01-01

Sediment geochronology of coastal sedimentary environments dominated by sand has been extremely limited because concentrations of natural and bomb-fallout radionuclides are often below the limit of measurement using standard techniques. ICP-MS analyses of 239+240Pu from two sites representative of traditionally challenging (i.e., low concentration) environments provide a "proof of concept" and demonstrate a new application for bomb-fallout radiotracers in the study of sandy shelf-seabed dynamics. A kasten core from the New Zealand shelf in the Southern Hemisphere (low fallout), and a vibracore from the sandy nearshore of North Carolina (low particle surface area) both reveal measurable 239+240Pu activities at depth. In the case of the New Zealand site, independently verified steady-state sedimentation results in a 239+240Pu profile that mimics the expected atmospheric fallout. The depth profile of 239+240Pu in the North Carolina core is more uniform, indicating significant sediment resuspension, which would be expected in this energetic nearshore environment. This study, for the first time, demonstrates the utility of 239+240Pu in the study of sandy environments, significantly extending the application of bomb-fallout isotopes to coarse-grained sediments, which compose the majority of nearshore regions.

Amending soils with sediment material from constructed wetlands increases phosphorus sorption

NASA Astrophysics Data System (ADS)

Laakso, Johanna; Uusitalo, Risto; Leppänen, Janette; Yli-Halla, Markku

2017-04-01

Sediment of agricultural constructed wetlands (CWs) is comprised of matter eroded from surrounding fields. This material is rich in aluminium (Al) and iron (Fe) (hydr)oxides that have a high affinity for phosphorus (P). Sediment material returned to fields could therefore affect soil P retention characteristics. We incubated a clay soil with a high soil test P (STP, 24 mg PAc l-1; extracted with pH 4.65 ammonium acetate buffer) and a sandy loam with excessive STP (210 mg PAc l-1) for three weeks with increasing amounts of CW sediment: 0, 2, 5, 10 and 50% of the sample volume. After incubation, the soil-sediment mixtures were studied with the quantity/intensity (Q/I) technique, using chemical extractions and by exposing the mixtures to simulated rainfall. Sorption affinity for P regularly increased with increasing the sediment share of the mixtures, the 0% sediment content having the lowest and 50% sediment content the highest P sorption. With 0% sediment application, the value of equilibrium P concentration (EPC0) determined by Q/I technique, was 0.69 and 44.3 mg l-1 for clay soil and sandy loam, respectively. With 2-5% sediment amendment, the EPC0 decreased 13-36% for clay soil and 13-54% for sandy loam. The 50% sediment mixtures had EPC0 of 0.05 mg l-1 for both soils. At a practically feasible sediment addition rate of 5%, dissolved reactive P (DRP) in percolating water from simulated rainfall decreased by 55% in the clay soil and 54% in sandy loam (p<0.001 in both cases). Particulate-P (PP) also showed a decreasing trend with increasing sediment addition rate. Upon prolonged simulated rainfall, the decreasing effect of sediment on DRP and PP declined somewhat. The effects of sediment addition can be attributed partly to increased salt concentrations in the sediment, which have a short-term effect on P mobilisation, but mostly to increased concentrations of Al and Fe (hydr)oxides, increasing long-term P sorption capacity. Amending the soils with sediment material would decrease P solubility and might at large application rates hamper P uptake by plants or, on the other hand, the sediment amendment in the soil might reduce P losses by runoff.

Tidal impacts on the subtidal flow division at the main bifurcation in the Yangtze River Delta

NASA Astrophysics Data System (ADS)

Zhang, Wei; Feng, Haochuan; Hoitink, A. J. F.; Zhu, Yuliang; Gong, Fei; Zheng, Jinhai

2017-09-01

Flow division at bifurcations in the Yangtze Estuary has received ample attention, since it may control the pathways of terrestrial sediments over downstream river branches including the 12.5 m Deepwater Navigation channel. While some efforts have been made to interpret flow division at the bifurcations of the Yangtze Estuary, little attention has been paid to the role of tides. Flow division at estuarine bifurcations is made complicated by tides that propagate from the outlet of the tidal channels into the delta. To quantify the tidal influence on the distribution of river discharge, and more generally, to understand the mechanisms governing the subtidal flow division at the tidally affected bifurcation in the Yangtze River Delta, a two-dimensional hydrodynamic model is employed. In this model, the landward boundary is chosen beyond the tidal limit, where the tidal motion has faded out entirely. The seaward boundary is chosen such that the river discharge does not influence the water level. Subtidal discharges are decomposed using the method of factor separation, to distinguish between the effects of tides, river discharge and river-tide interactions on the subtidal flow division. Results indicate that tides modify the river discharge distribution over distributary channels in the Yangtze River Delta, particularly in the dry season. A significant difference in the subtidal flow division during spring tide and neap tide shows that the tidally averaged flow division over the distributaries in the delta greatly depends on tidal amplitude. By varying the river discharge at the landward boundary and amplitudes and phases of the principal tidal constituents at the seaward boundary of the established model, the sensitivities of the subtidal flow division to the river discharge and tidal amplitude variation were investigated in detail. Generally, the tidal impacts on the subtidal flow division are around 12% to 22%, with river discharge varying from 30,000 m3s-1 to 20,000 m3s-1. This effect on the flow distribution can even overwhelm the effects induced by river discharge based on geometry only, when the flow discharge is lowest. Furthermore, the fortnightly tidal cycle plays an important role in enhancing the inequality of the subtidal flow division caused by the M2 tidal component solely at the tidal bifurcation in the Yangtze River Delta during low flow.

Thiosulfate and sulfite distributions in porewater of marine sediments related to manganese, iron, and sulfur geochemistry

NASA Astrophysics Data System (ADS)

Thamdrup, Bo; Finster, Kai; Fossing, Henrik; Hansen, Jens Würgler; Jørgensen, Bo Barker

1994-01-01

Depth distributions of thiosulfate (S 2O 32-) and sulfite (SO 32-) were measured in the porewaters of a Danish salt marsh and subtidal marine sediments by HPLC analysis after derivatization with DTNP [2,2'-dithiobis(5-nitropyridine)]. The distributions were compared to the redox zonation as indicated by Eh and Mn 2+, Fe 2+ and H 2S distributions. Concentrations of S 2O 32- varied from below detection (<50 nM) to 600 nM while SO 32- concentrations generally were 2-3 times higher, 100-1500 nM. Depth distributions of the two species were roughly similar. Lowest concentrations were found in the oxidized zone, including both the oxic surface layer and the suboxic zone of intense manganese and iron reduction, and concentrations tended to increase through the suboxic and into the reduced, sulfidic zone. The similarity of SO 32- and S 2O 32- profiles suggested a close coupling of the cycling of the two species. Rates of consumption were suggested as the main factor governing their distribution. Rapid turnover times for S 2O 32- and H 2S of 4 and 1.1 h, respectively, were estimated for the upper 0-1 cm of a subtidal sediment.

Species composition, richness, and distribution of marine bivalve molluscs in Bahía de Mazatlán, México

PubMed Central

Esqueda-González, María del Carmen; Ríos-Jara, Eduardo; Galván-Villa, Cristian Moises; Rodríguez-Zaragoza, Fabian Alejandro

2014-01-01

Abstract We describe the composition and distribution of bivalve molluscs from the sandy and rocky intertidal and the shallow subtidal environments of Bahía de Mazatlán, México. The bivalve fauna of the bay is represented by 89 living species in 28 families, including 37 new records and four range extensions: Lithophaga hastasia, Adula soleniformis, Mactrellona subalata, and Strigilla ervilia. The number of species increases from the upper (44) and lower intertidal (53) to the shallow subtidal (76), but only 11 (17%) have a wide distribution in the bay (i.e., found in all sampling sites and environments). The bivalve assemblages are composed of four main life forms: 27 epifaunal species, 26 infaunal, 16 semi-infaunal, and 20 endolithic. A taxonomic distinctness analysis identified the sampling sites and environments that contribute the most to the taxonomic diversity (species to suborder categories) of the bay. The present work increased significantly (31%) to 132 species previous inventories of bivalves of Bahía de Mazatlán. These species represent 34% of the bivalve diversity of the southern Golfo de California and approximately 15% of the Eastern Tropical Pacific region. PMID:24843252

California State Waters Map Series: Drakes Bay and vicinity, California

USGS Publications Warehouse

Watt, Janet T.; Dartnell, Peter; Golden, Nadine E.; Greene, H. Gary; Erdey, Mercedes D.; Cochrane, Guy R.; Johnson, Samuel Y.; Hartwell, Stephen R.; Kvitek, Rikk G.; Manson, Michael W.; Endris, Charles A.; Dieter, Bryan E.; Sliter, Ray W.; Krigsman, Lisa M.; Lowe, Erik N.; Chinn, John L.; Watt, Janet T.; Cochran, Susan A.

2015-01-01

Sediment transport in the map area largely is controlled by surface waves and tidal currents in the nearshore and, at depths greater than 20 to 30 m, by tidal and subtidal currents. In the map area, nearshore littoral drift of sand and coarse sediment is to the south, owing to the dominant west-northwest swell direction, and scour from large waves and tidal currents removes and redistributes sediment over large areas of the inner shelf. Tidal currents are particularly strong over the shelf in the map area, and they dominate the current regime in the nearshore. Further offshore, bottom currents generally flow to the northwest, distributing finer grained sediment accordingly.

The relationship of environmental factors to the structure and distribution of subtidal seaweed vegetation of the western Basque coast (N Spain)

NASA Astrophysics Data System (ADS)

Díez, I.; Santolaria, A.; Gorostiaga, J. M.

2003-04-01

Subtidal vegetation distribution patterns in relation to environmental conditions (pollution, wave exposure, sedimentation, substratum slope and depth) were studied along the western Basque coast, northern Spain, by applying canonical correspondence analysis and log-linear regressions. A total of 90 species of macrophytes were recorded by systematic sampling along 21 transects. Mesophyllum lichenoides and Cystoseira baccata were the most abundant (accounting for 47% of the overall algal cover). Gelidium sesquipedale, Pterosiphonia complanata, Zanardinia prototypus, Codium decorticatum and Asparagopsis armata ( Falkenbergia phase) were other macrophytes with significant cover. Ordination analysis indicates that the five environmental variables explored account between them for 52% of the species data variance. Pollution, sedimentation and wave exposure were the principal factors explaining differences in flora composition and abundance (24, 14 and 12% of the explained variance, respectively). Log-linear regressions and canonical correspondence analyses reveal that C. baccata and G. sesquipedale exhibit a negative relationship with pollution, while sediment loading negatively affects G. sesquipedale, and C. baccata cannot stand high wave exposure levels. In contrast, P. complanata and C. decorticatum show a positive relationship with pollution and can bear high levels of sedimentation and wave exposure. M. lichenoides and Z. prototypus present a wide tolerance range for all these factors. Macroalgal cover, species richness and diversity remain practically constant from unpolluted to slightly polluted sites, but they decrease sharply under moderately polluted conditions. In the same way, algal cover decreases as sediment loading increases, but diversity and species richness show the highest values at intermediate levels of sedimentation. In relation to wave exposure, maximum algal cover was achieved at very exposed habitats whereas diversity and species richness were higher under semi-exposed conditions.

Tracking the Fate of Explosive-Trinitrotriazine (RDX) in Coastal Marine Ecosystems Using Stable Isotopic Tracer

NASA Astrophysics Data System (ADS)

Ariyarathna, T. S.; Ballentine, M.; Vlahos, P.; Smith, R. W.; Bohlke, J. K.; Tobias, C. R.; Fallis, S.; Groshens, T.; Cooper, C.

2017-12-01

It has been estimated that there are hundreds of explosive-contaminated sites all over the world and managing these contaminated sites is an international challenge. As coastal zones and estuaries are commonly impacted zones, it is vital to understand the fate and transport of munition compounds in these environments. The demand for data on sorption, biodegradation and mineralization of trinitrotriazine (RDX) in coastal ecosystems is the impetus for this study using stable nitrogen isotopes to track its metabolic pathways. Mesocosm experiments representing subtidal vegetated, subtidal unvegetated and intertidal marsh ecocosms were conducted. Steady state concentrations of RDX were maintained in the systems throughout two-week time duration of experiments. Sediment, pore-water and overlying water samples were analyzed for RDX and degradation products. Isotope analysis of the bulk sediments revealed an initial rising inventory of 15N followed by a decay illustrating the role of sediments on sorption and degradation of RDX in anaerobic sediments respectively. Both pore-water and overlying water samples were analyzed for 15N inventories of different inorganic nitrogen pools including ammonium, nitrate, nitrite, nitrous oxide and nitrogen gases. RDX is mineralized to nitrogen gas through a series of intermediates leaving nitrous oxide as the prominent metabolite of RDX. Significant differences in RDX metabolism were observed in the three different ecosystems based on sediment characteristics and redox conditions in the systems. Fine grained organic carbon rich sediments show notably higher mineralization rates of RDX in terms of production of its metabolites. Quantification of degradation and transformation rates leads to mass balances of RDX in the systems. Further analysis of results provides insights for mineralization pathways of RDX into both organic and inorganic nitrogen pools entering the marine nitrogen cycle.

Temporally Dynamic, Spatially Static, Cobble Bedforms in Reversing Subtidal Currents

NASA Astrophysics Data System (ADS)

Abdulkade, A.

2015-12-01

Cobble bedforms, c. 1m high with lengths of several metres and transverse to the reversing tidal currents, are exposed at extreme low-water Spring tides on an inter-tidal bedrock shelf in the macro-tidal Severn Estuary, UK. Near-bed flow velocities during Spring tides can exceed 1.5m/s, with water depths varying from zero to in excess of 10m. During neap tides the bedforms are not exposed, and sediment is expected to be of limited mobility. When exposed, the bedform geometry tends to be asymmetric; orientated down estuary with the ebb current. During Spring tides, vigorous bedload transport of gravel (including large cobbles) occurs during both flood and ebb over the crests and yet, despite this temporal dynamism, the bedforms remain spatially static over long time periods or show weak down-estuary migration. Stasis implies that the tidal bedload transport vectors are essentially in balance. Near-bed shear stress and bed roughness values vary systematically with the Spring-tide current speeds and the predicted grain-size of the bed load using the Shields criterion is in accord with observed coarser grain-sizes in transport. These hydrodynamic data, delimited by estimates of the threshold of motion, and integrated over either flood or ebb tides are being used to explain the apparent stability of the bedforms. The bulk hydraulic data are supplemented by particle tracer studies and laser-scanning of bed configurations between tides. The high-energy environment results in two forms of armouring. Pronounced steep imbrication of platy-cobbles visible on the exposed up-estuary side of dunes is probably disrupted during flood tides leading to rapid reworking of the toe deposits facing up-estuary. In contrast, some crest and leeside locations have been stable for prolonged periods such that closely-fitted fabrics result; these portions of the bedforms are static and effectively are 'armour-plated'. Ebb-tide deposits of finer, ephemeral sandy-units occur on the down estuary side of the bedforms. Sandy-units (although not observed at low tide) presumably also are deposited on the up estuary side during flooding tides but these deposits are destroyed by ebb flows. The implication of these sediment transport processes on the stratification of the bedforms is considered.

Laboratory Investigations and Numerical Modeling of Loss Mechanisms in Sound Propagation In Sandy Sediments

DTIC Science & Technology

2008-09-30

meeting of the Acoustical Society of America in Providence, RI [7]. In this model , the scalar form Biot’s poroelastic equations could be used since...Laboratory Investigations and Numerical Modeling of Loss Mechanisms in Sound Propagation in Sandy Sediments. Brian T. Hefner Applied...Number: N00014-05-1-0225 http://www.apl.washington.edu LONG-TERM GOALS To develop accurate models for high frequency sound propagation within

Early Diagenesis of Subseafloor Sandy Sediments Closely Related to Gas Hydrate Occurrences and Their Provenances in the Eastern Margin of Japan Sea

NASA Astrophysics Data System (ADS)

Uchida, T.; Sakai, H.; Horiuchi, S.; Matsumoto, R.

2015-12-01

A lot of effort have been put into recovering gas hydrate, methane induced carbonate, and associated sediments in order to develop the geologic model of gas hydrate accumulation and evaluate its possible environmental impact for the last glacial-interglacial cycles. Having investigated gas hydrate occurrences in the eastern margin of Japan Sea revealed wide distributions of chimney-shape gas hydrate concentrations beneath the seafloor, confirmed off Shimane and off Akita/Yamagata as well as off Joetsu (Niigata), which are quite different from the occurrences of pore space hydrate filling intergranular pore systems of sands recognized in Nankai Trough, Mallik and other sites. Many sediment samples have been obtained below from the Umitaka Spur, Joetsu Channel, Toyama Trough, Mogami Trough and Okushiri Ridge areas. Small amounts of sandy sediment have been retrieved as thin intercalations in Holocene and Pleistocene silty/muddy layers, where trace fossils and strong bioturbations are commonly observed. Sandy sediments consist of very fine- to fine-grained sand grains, and are sometimes tuffaceous. Pore-size distribution measurements and thin-section observations of these sands were carried out, which indicate that porosities of silty sediments are around 50 % but those of arenites range from 42 to 52 %, of which mean pore sizes and permeabilities are larger than those of silty sediments. These coarser sediments might have been transported approximately around 3 to 30 ka due to the tephra ages, where supplying sediments might be abundant due to sea level fluctuation during the Pleistocene ice age. Sandy sediments contain not only detrital quartz and feldspar but mafic minerals (pyroxene, amphibole and mica), contents of which may indicate their provenances. Silty/muddy sediments usually contain diatom tests, foraminifers and framboidal pyrites, and, in particular, the shapes of diatom are usually various, dominantly fragmental and infrequently preserved. It is remarked that physical diagenesis proceeds first due to mechanical compaction, whereas chemical diagenesis advances very slowly in early diagenesis. This study was performed as a part of the MH21 Research Consortium on methane hydrate in Japan and the METI project entitled "FY2014 promoting research and development on methane hydrate."

Lateral trends and vertical sequences in estuarine sediments, Willapa Bay, Washington

USGS Publications Warehouse

Clifton, H. Edward; Phillips, L.

1980-01-01

Willapa Bay is a sizable estuary on the southern coast of Washington- Relatively unmodified in a geologic sense by human activity the bay provides an excellent example of modern depositional facies in an estuarine setting. Studies of these deposits indicate that consistent lateral trends exist in sediment texture and sedimentary structures. The texture changes from sandy at the mouth of the bay to muddy in its upper parts. In any part of the bay , sediment is coarsest in the channel bottoms, where lag deposits accumulate. The sediment tends to fine in an upslope direction and is finest in supratidal flat deposits of silt and clay. The nature of sedimentary structures depends on the combination of physical and biological processes and sediment textures. Bedforms exist wherever the bed is sandy. In the main tidal channels sandwaves and dunes up to 4 meters high occur. In tributary channels and at the margins of the main channel, at shallower depths and under less intense currents , the structures are generally less than a meter high. Current ripples occur in t he sandy bed of all of the tidal channels and in runoff channels cross the tidal flat. Symmetric long-crested ripples are produced by wave action over the sandy intertidal flat. Internal structures in the bay's sediment depend not only on the nature of the bedform but also on the rate of bioturbation relative to physical processes. Under fields of large sandwaves or dunes, medium- to large-scale tabular and trough crossbedding predominates. This crossbedding generally is unidirectional, reflecting the locally dominant current (ebb or flood). Ripple bedding predominates elsewhere in sandy sediment within the channels. Where sand transport is diminished, as on the floor of the upper tributary channels, bioturbation exceeds the rate of production of physical structures and bedding is destroyed. The depositional banks in such areas tend to be sites of rapid sediment accumulation and bedding in the form of interlayered sand (commonly ripple bedded) and mud persists. On intertidal flats the sediment accumulates slowly and bioturbation erases nearly all physical structures. Bedding is preserved only where deposition is locally rapid , as in topographic depressions or on the depositional banks of runoff channels, or where faunal activity is inhibited, as beneath mounds of blue-green algae. The rate of sedimentation is slower still on the supratidal flats, but the general paucity of faunal activity allows the preservation of thin alternations of fine sand , silt or clay. The lateral migration of the tidal channels produces vertical sequences in which topographically higher facies are superposed on one another. Near the mouth of the estuary the upward sequence: lag deposit — crossbedded sand — ripple or planar-bedded sand is typical. The crossbedding shows a general upward decrease in thickness and a progression from trough to tabular units. In the main tidal channel - in the central estuary and in sandy tributary channels, the typical vertical sequence resembles that near the mouth , with the exception that the sequence is capped by bioturbated sandy or muddy tide flat deposits. In the upper estuary , where muddy sediment predominates, a typical sequence shows the progression-. bioturbated lag deposit — gently dipping interlaminated sand and mud layers of the accretionary bank — bioturbated mud flat deposits — thinly laminated fine supratidal deposits.

Does Encope emarginata (Echinodermata: Echinoidea) affect spatial variation patterns of estuarine subtidal meiofauna and microphytobenthos?

NASA Astrophysics Data System (ADS)

Brustolin, Marco C.; Thomas, Micheli C.; Mafra, Luiz L.; Lana, Paulo da Cunha

2014-08-01

Foraging macrofauna, such as the sand dollar Encope emarginata, can modify sediment properties and affect spatial distribution patterns of microphytobenthos and meiobenthos at different spatial scales. We adopted a spatial hierarchical approach composed of five spatial levels (km, 100 s m, 10 s m, 1 s m and cm) to describe variation patterns of microphytobenthos, meiobenthos and sediment variables in shallow subtidal regions in the subtropical Paranaguá Bay (Southern Brazil) with live E. emarginata (LE), dead E. emarginata (only skeletons - (DE), and no E. emarginata (WE). The overall structure of microphytobenthos and meiofauna was always less variable at WE and much of variation at the scale of 100 s m was related to variability within LE and DE, due to foraging activities or to the presence of shell hashes. Likewise, increased variability in chlorophyll-a and phaeopigment contents was observed among locations within LE, although textural parameters of sediment varied mainly at smaller scales. Variations within LE were related to changes on the amount and quality of food as a function of sediment heterogeneity induced by the foraging behavior of sand dollars. We provide strong evidence that top-down effects related to the occurrence of E. emarginata act in synergy with bottom-up structuring related to hydrodynamic processes in determining overall benthic spatial variability. Conversely, species richness is mainly influenced by environmental heterogeneity at small spatial scales (centimeters to meters), which creates a mosaic of microhabitats.

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

Page, D.S.; Boehm, P.D.; Douglas, G.S.

Advanced hydrocarbon fingerprinting methods and improved analytical methods make possible the quantitative discrimination of the multiple sources of hydrocarbons in the benthic sediments of Prince William Sound (PWS) and the Gulf of Alaska. These methods measure an extensive range of polycyclic aromatic hydrocarbons (PAH) at detection levels that are as much as two orders of magnitude lower than those obtained by standard Environmental Protection Agency methods. Nineteen hundred thirty six subtidal sediment samples collected in the sound and the eastern Gulf of Alaska in 1989, 1990, and 1991 were analyzed. Fingerprint analyses of gas chromatography-mass spectrometry data reveal a naturalmore » background of petrogenic and biogenic PAH. Exxon Valdez crude, its weathering products, and diesel fuel refined from Alaska North Slope crude are readily distinguished from the natural seep petroleum background and from each other because of their distinctive PAH distributions. Mixing models were developed to calculate the PAH contributions from each source to each sediment sample. These calculations show that most of the seafloor in PWS contains no detectable hydrocarbons from the Exxon Valdez spill, although elevated concentrations of PAH from seep sources are widespread. In those areas where they were detected, spill hydrocarbons were generally a small increment to the natural petroleum hydrocarbon background. Low levels of Exxon Valdez crude residue were present in 1989 and again in 1990 in nearshore subtidal sediments off some shorelines that had been heavily oiled. By 1991 these crude residues were heavily degraded and even more sporadically distributed. 58 refs., 18 figs., 5 tabs.« less

Reconstructing Mississippi River Deltaic Wetland Hydrostratigraphy Using Compositional Kriging Method - Implications for Groundwater, Groundwater-River Water Interaction, Subsidence and Deltaic Wetland Evolution

NASA Astrophysics Data System (ADS)

Li, A.; Tsai, F. T. C.; White, C.; Wang, J.; Bentley, S. J.; Xu, K.

2016-12-01

River deltaic wetlands are formed along coastal area where sediment-laden river water reaches ocean. A river deltaic wetland is a complex system that mainly consists of groundwater, soil and vegetation components. Groundwater makes up a large portion of the system. The wetlands are important to human being and wild life. This research focuses on hydrostratigraphic architecture of the Mississippi River deltaic wetland. Research area includes lower Barataria Bay and lower Breton Sound that located on the Mississippi River Delta in southern Louisiana. In this study, a three dimensional hydrostratigraphy model is constructed using coring survey grain size data and geostatistics approach. A three-dimensional grid system is firstly constructed to cover the whole research domain. Each cell of the grid has a dimension of 100 meters by 100 meters by 1 centimeter (length by width by depth). Then Compositional Kriging and Gaussian Sequential Simulation methods are adopted to estimate soil composition (sand, silt and clay fractions) for each cell. A result has been generated to reveal spatial hydro facies variation by cutting cross sections and extracting soil texture maps at different locations. In the result, bay silt makes a large portion of the sediments body and sandy sediments are shown at different depths in both sides of the river. In Barataria Bay, sand bodies are lenticular, relatively thick and vertical continuous, however, in Breton Sound, sand bodies are sheet-like, relatively thin and vertical non-continuous. It is likely that the sandy sediments in Barataria Bay and Breton Sound are deposited in distal distributary and overbank flow respectively. Larger sandy bodies are prone to form in the distal distributary than in the overbank flow. Sandy units formed in the distal distributary can provide better interconnection between river water and groundwater than that formed in the overbank flow. Larger sandy bodies also provides more space to store groundwater. More silty and clayey sediments in the Breton Sound side make it more subject to compactional subsidence. More sandy sediments occur at the shallow portion of the Breton Sound than Barataria Bay. And these sands are interpreted as transgressive product that is formed by reworking forces such as wind, tide, cold front and storm.

Comparing efficacy of different taxonomic resolutions and surrogates in detecting changes in soft bottom assemblages due to coastal defence structures.

PubMed

Bertasi, Fabio; Colangelo, Marina Antonia; Colosio, Francesco; Gregorio, Gianni; Abbiati, Marco; Ceccherelli, Victor Ugo

2009-05-01

Sandy shores on the West coast of the North Adriatic Sea are extensively protected by different types of defence structures to prevent coastal erosion. Coastal defence schemes modify the hydrodynamic regime, the sediment structure and composition thus affecting the benthic assemblages. This study examines the effectiveness in detecting changes in soft bottom assemblages caused by coastal defence structures by using different levels of taxonomic resolution, polychaetes and/or bivalves as surrogates and different data transformations. A synoptic analyses of three datasets of subtidal benthic macrofauna used in studies aimed at assessing the impact of breakwaters along the North Adriatic coast has been done. Analyses of similarities and correlations between distance matrices were done using matrices with different levels of taxonomic resolution, and with polychaetes or bivalves data alone. Lentidium mediterraneum was the most abundant species in all datasets. Its abundance was not consistently related to the presence of defence structures. Moreover, distribution patterns of L. mediterraneum were masking the structure of the whole macrofaunal assemblages. Removal of L. mediterraneum from the datasets allowed the detection of changes in benthic assemblages due to coastal defences. Analyses on different levels of taxonomic resolution showed that the level of family maintained sufficient information to detect the impacts of coastal defence structures on benthic assemblages. Moreover, the outcomes depended on the transformation used. Patterns of distribution of bivalves, used as surrogates, showed low correlations with the patterns of the total macrofaunal species assemblages. Patterns of polychaetes, if identified to the species or genus level showed higher correlations with the whole dataset. However, the identification of polychaetes to species and genus level is as costly as the identification of all macrobenthic taxa at family level. This study provided additional evidences that taxonomic sufficiency is a useful tool in environmental monitoring, also in investigations on the impacts of coastal defence structures on subtidal macrofauna. The use of coarser taxonomic level, being time-efficient, would allow improving sampling designs of monitoring programs by increasing replication in space and time and by allowing long term monitoring studies.

Benthic biological C processing patterns in two Scottish estuaries and the significance of bacterial C uptake in sandy sediments

NASA Astrophysics Data System (ADS)

Woulds, Clare; Cowie, Greg; Witte, Ursula; Middelburg, Jack

2013-04-01

The supply of detrital organic matter to marine sediments is important for the nutrition of benthic ecosystems, while its remineralisation and burial supplies nutrients to the water column, and is a significant C sequestration process. Biological processes regulate sedimentary organic matter cycling, however the dominant processes vary between sites, and our knowledge of the factors driving that variation is still limited. Isotope tracing experiments have shown that the pattern and rate of biological processing of organic carbon (C) in marine sediments allows sites to be categorised based on the relative importance of different processes and C pools. Thus, total community respiration is often the dominant process, but its dominance is maximal in deep ocean sediments. In shallower settings, with greater organic matter availability, faunal uptake of organic C becomes more significant, and, where there is particularly high faunal biomass, can become dominant. New isotope tracing experiments have been conducted which compare biological C processing patterns in two contrasting Scottish estuaries. These are Loch Etive, where muddy, comparatively organic C rich sediments become hypoxic within millimetres of the sediment-water interface; and the Ythan estuary, where organic C poor, sandy sediments are kept oxygenated by porewater advection. Taken together with other experiments from the literature, the results now suggest that estuarine and shelf sandy sediments constitute a distinct category of biological C processing, in which bacterial C uptake plays a particularly significant role.

Enhancing the biodegradation of oil in sandy sediments with choline: a naturally methylated nitrogen compound.

PubMed

Mortazavi, Behzad; Horel, Agota; Anders, Jennifer S; Mirjafari, Arsalan; Beazley, Melanie J; Sobecky, Patricia A

2013-11-01

We investigated how additions of choline, a naturally occurring methylated nitrogen-containing compound, accelerated hydrocarbon degradation in sandy sediments contaminated with moderately weathered crude oil (4000 mg kg(-1) sediment). Addition of lauroylcholine chloride (LCC) and tricholine citrate (TCC) to oil contaminated sediments resulted in 1.6 times higher hydrocarbon degradation rates compared to treatments without added choline derivatives. However, the degradation rate constant for the oil contaminated sediments amended with LCC was similar to that in contaminated sediments amended with inorganic nitrogen, phosphorus, and glucose. Additions of LLC and TCC to sediments containing extensively weathered oil also resulted in enhanced mineralization rates. Cultivation-free 16S rRNA analysis revealed the presence of an extant microbial community with clones closely related to known hydrocarbon degraders from the Gammaproteobacteria, Alphaproteobacteria, and Firmicutes phyla. The results demonstrate that the addition of minimal amounts of organic compounds to oil contaminated sediments enhances the degradation of hydrocarbons. Copyright © 2013 Elsevier Ltd. All rights reserved.

Sedimentological Properties of Natural Gas Hydrates-Bearing Sands in the Nankai Trough and Mallik Areas

NASA Astrophysics Data System (ADS)

Uchida, T.; Tsuji, T.; Waseda, A.

2009-12-01

The Nankai Trough parallels the Japanese Island, where extensive BSRs have been interpreted from seismic reflection records. High resolution seismic surveys have definitely indicated gas hydrate distributions, and drilling the MITI Nankai Trough wells in 2000 and the METI Tokai-oki to Kumano-nada wells in 2004 have revealed subsurface gas hydrate in the eastern part of Nankai Trough. In 1998 and 2002 Mallik wells were drilled at Mackenzie Delta in the Canadian Arctic that also clarified the characteristics of gas hydrate-dominant sandy layers at depths from 890 to 1110 m beneath the permafrost zone. During the field operations, the LWD and wire-line well log data were continuously obtained and plenty of gas hydrate-bearing sand cores were recovered. Subsequence sedimentological and geochemical analyses performed on those core samples revealed the crucial geologic controls on the formation and preservation of natural gas hydrate in sediments. Pore-space gas hydrates reside in sandy sediments mostly filling intergranular porosity. Pore waters chloride anomalies, core temperature depression and core observations on visible gas hydrates confirm the presence of pore-space gas hydrates within moderate to thick sandy layers, typically 10 cm to a meter thick. Sediment porosities and pore-size distributions were obtained by mercury porosimetry, which indicate that porosities of gas hydrate-bearing sandy strata are approximately 45 %. According to grain size distribution curves, gas hydrate is dominant in fine- to very fine-grained sandy strata. Gas hydrate saturations are typically up to 80 % in pore volume throughout most of the hydrate-dominant sandy layers, which are estimated by well log analyses as well as pore water chloride anomalies. It is necessary for investigating subsurface fluid flow behaviors to evaluate both porosity and permeability of gas hydrate-bearing sandy sediments, and the measurements of water permeability for them indicated that highly saturated sands should have permeability of 1 x 10-15 to 5 x 10-15 m2 (1 to 5 millidarcies). Most of gas hydrates fill the intergranular pore systems of sandy layers, which are derived from the sedimentary facies such as channels and crevasse splay/levee deposits. It is remarked that those sandy strata are usually composed of arenite sands with matrix-free intergranular pore systems. Gas hydrates are less frequently found in fine-grained sediments such as siltstone and mudstone from overbank deposits. Methane gas accumulation and original pore space large enough to occur within host sediments may be required for forming highly saturated gas hydrate in pore system. The distribution of a porous and coarser-grained host rock should be one of the important factors to control the occurrence of gas hydrate, as well as physicochemical conditions. This appears to be a similar mode for conventional oil and gas accumulations, and this knowledge is important to predicting the location of other hydrate deposits and their eventual energy resource. This study was performed as a part of the MH21 Research Consortium on methane hydrate in Japan.

Sediment and discharge yields within a minimally disturbed, headwater watershed in North Central Pennsylvania, USA, with an emphasis on Superstorm Sandy

USGS Publications Warehouse

Maloney, Kelly O.; Shull, Dustin R.

2015-01-01

We estimated discharge and suspended sediment (SS) yield in a minimally disturbed watershed in North Central Pennsylvania, USA, and compared a typical storm (September storm, 4.80 cm) to a large storm (Superstorm Sandy, 7.47 cm rainfall). Depending on branch, Sandy contributed 9.7–19.9 times more discharge and 11.5–37.4 times more SS than the September storm. During the September storm, the upper two branches accounted for 60.6% of discharge and 88.8% of SS at Lower Branch; during Sandy these percentages dropped to 36.1% for discharge and 30.1% for SS. The branch with close proximity roads had over two-three times per area SS yield than the branch without such roads. Hysteresis loops showed typical clockwise patterns for the September storm and more complicated patterns for Sandy, reflecting the multipeak event. Estimates of SS and hysteresis in minimally disturbed watersheds provide useful information that can be compared spatially and temporally to facilitate management.

Large-Scale Laboratory Experiments of Incipient Motion, Transport, and Fate of Underwater Munitions Under Waves, Currents, and Combined Flows

DTIC Science & Technology

2015-12-01

little or no sediment cover (e.g., such as on coral reefs ) versus a sandy or muddy bottom. However, there is a dearth of direct observations made under...where there is little or no sediment cover (e.g., such as on coral reefs ) versus a sandy or muddy bottom. However, there is a dearth of direct...INTERIM REPORT Large-Scale Laboratory Experiments of Incipient Motion, Transport, and Fate of Underwater Munitions under Waves , Currents, and

The distribution and utility of sea-level indicators in Eurasian sub-Arctic salt marshes (White Sea, Russia).

NASA Astrophysics Data System (ADS)

Nikitina, Daria; Kemp, Andrew; Horton, Benjamin; Van, Christopher; Potapova, Marina; Culver, Stephen; Repkina, Tatyana; Hill, David

2017-04-01

We investigated the utility of foraminifera, diatoms and bulk-sediment geochemistry (δ13C and parameters measured by RockEval pyrolysis) as sea-level indicators in Eurasian sub-Arctic salt marshes. At three salt marshes in Dvina Bay (White Sea, Russia), we collected surface sediment samples along transects sequentially crossing sub-tidal, tidal-flat, salt-marsh and Taiga forest environments. Foraminifera formed bipartite assemblages, where elevations below mean high higher water (MHHW) were dominated by Miliammina spp. and elevations between MHHW and the highest occurrence of foraminifera were dominated by Jadammina macrescens and Balticammina pseudomacrescens. Both assemblages existed on all three transects and we conclude that foraminifera are sea-level indicators in Eurasian sub-Arctic salt marshes. Five, high-diversity groups of diatoms were identified and they displayed geographic variability among the study sites (<15 km apart). RockEval pyrolysis and δ13C measurements recognized two groups (clastic-dominated environments below MHHW and organic-rich environments above MHHW). Since one group included sub-tidal elevations and the other supra-tidal elevations, we conclude that the measured geochemical parameters do not meet the criteria for being stand-alone sea-level indicators. Core JT2012 captured a regressive sediment sequence of clastic, tidal-flat sediment overlain by salt-marsh organic silt and freshwater peat. The salt-marsh sediment accumulated at 2804 ± 52 years BP years before present and preserved foraminifera (J. macrescens and B. pseudomacrescens) with a high degree of analogy to modern assemblages indicating that relative sea level was 2.60 ± 0.47 m above present at this time. Diatoms confirm that marine influence decreased through time, but the lack of analogy between modern and core assemblages limits their utility as sea-level indicators in this setting.

Hydrodynamic conditioning of diversity and functional traits in subtidal estuarine macrozoobenthic communities

NASA Astrophysics Data System (ADS)

van der Wal, Daphne; Lambert, Gwladys I.; Ysebaert, Tom; Plancke, Yves M. G.; Herman, Peter M. J.

2017-10-01

Variations in abundance and diversity of estuarine benthic macrofauna are typically described along the salinity gradient. The influence of gradients in water depth, hydrodynamic energy and sediment properties are less well known. We studied how these variables influence the distribution of subtidal macrofauna in the polyhaline zone of a temperate estuary (Westerschelde, SW Netherlands). Macrofauna density, biomass and species richness, combined in a so-called ecological richness, decreased with current velocities and median grain-size and increased with organic carbon of the sediment, in total explaining 39% of the variation. The macrofauna community composition was less well explained by the three environmental variables (approx. 12-15% in total, with current velocity explaining approx. 8%). Salinity, water depth and distance to the intertidal zone had a very limited effect on both ecological richness and the macrofauna community. The proportion of (surface) deposit feeders (including opportunistic species), decreased relative to that of omnivores and carnivores with increasing current velocity and sediment grain-size. In parallel, the proportion of burrowing sessile benthic species decreased relative to that of mobile benthic species that are able to swim. Correspondingly, spatial variations in hydrodynamics yielded distinct hotspots and coldspots in ecological richness. The findings highlight the importance of local hydrodynamic conditions for estuarine restoration and conservation. The study provides a tool based on a hydrodynamic model to assess and predict ecological richness in estuaries.

The surface sediment types and their rare earth element characteristics from the continental shelf of the northern south China sea

NASA Astrophysics Data System (ADS)

Wang, Shuhong; Zhang, Nan; Chen, Han; Li, Liang; Yan, Wen

2014-10-01

The grain size as well as some major and trace elements, including rare earth element (REE), for 273 surface sediment samples collected from the continental shelf of the northern South China Sea were analyzed in this study. The sediment types are mainly sandy silt and silt, making up 60% of the whole samples, and secondly are mud, sandy mud, muddy sand and silty sand, making up 28% of the whole samples, based on grain-size in which the Folk's classification was used. The total REE content (ΣREE) show a wide variation from 21 ppm to 244 ppm with an average value of 155 ppm, which similar to the average ΣREE of the China loess, but much different from that in deep-sea clay, showing a significant terrigenous succession. The REE contents in different sediment types vary greatly, mainly enriching in silt, sandy silt, mud and sandy mud. The REE distribution contours parallel to the coastal, presenting like strips and their contents gradually reduce with increasing distance from the coast. The high content of the western Pearl River Mouth, Shang/Xiachuan Islands and Hailing Bay might be regarded to the coastal current developed from the east to the west along to the Pearl River Mouth in the northern South China Sea. But the chondrite-normalized REE patterns in various sediment types have no difference, basically same as those of coastal rivers and upper crust. They all show relative enrichments in light rare earth element (LREE), noticeable negative Eu anomaly and no Ce anomaly, indicating that those sediments are terrigenous sediments and from the same source region. Further analysis suggest that the sedimentary environment in the study area is relatively stable and granite widely distributed in the South China mainland is the main source of REE, which are transported mainly by the Pearl River. The late diagenesis has little effect on the REE.

Taxonomic and numerical sufficiency in a Lower and Middle Miocene molluscan metacommunity of the Central Paratethys

NASA Astrophysics Data System (ADS)

Zuschin, Martin; Nawrot, Rafal; Harzhauser, Mathias; Mandic, Oleg

2015-04-01

Among the most important questions in quantitative palaeoecology is how taxonomic and numerical resolution affect the analysis of community and metacommunity patterns. A species-abundance data set (10 localities, 213 bulk samples, 478 species, > 49,000 shells) from Burdigalian, Langhian and Serravallian benthic marine molluscan assemblages of the Central Paratethys was studied for this purpose. Assemblages are from two nearshore habitats (estuarine and marine intertidal) and three subtidal habitats (estuarine, fully marine sandy, and fully marine pelitic), which represent four biozones and four 3rd order depositional sequences over more than three million years, and are developed along the same depth-related environmental gradient. Double-standardized data subsampled to 19 samples per habitat, each with a minimum of 50 specimens, were used to calculate R²-values from PERMANOVA as a measure of differences between habitats at three taxonomic levels (species, genera and families) and at five levels of data transformation (raw abundances, percentages, square-root transformed percentages, fourth-root transformed percentages, presence-absence data). Species discriminate better between habitats than genera and families, but the differences between taxonomic levels are much stronger in the subtidal, where genera and families have more species than than in the intertidal. When all habitats are compared percentages and square-root transformed percentages discriminate equally well and perform better than higher levels of data transformation. Among nearshore and among subtidal habitats, however, the ability to discriminate between habitats increases with the level of data transformation (i.e., it is best for fourth-root transformed percentages and presence-absence data). The impact of decreasing taxonomic resolution is of minor importance in nearshore habitats, which are characterized by similar assemblages showing strong dominance of few widely distributed species, and many families represented by only one species (77.9%). Consequently, the differentiation between nearshore habitats is much weaker compared to subtidal assemblages. The latter are characterized by more distinct, relatively even assemblages with comparatively few families represented by only one species (64.2%) and many rare taxa, whose importance is emphasized by higher levels of data transformation.

Contrasting sedimentation patterns in two semi-enclosed mesotidal bays along the west and south coasts of Korea controlled by their orientation to the regional monsoon climate

NASA Astrophysics Data System (ADS)

Hong, Seok Hwi; Chun, Seung Soo; Chang, Tae Soo; Jang, Dae Geon

2017-08-01

Sedimentation patterns of tidal flats along the Korean west coast have long been known to be largely controlled by the monsoon climate. On the other hand, much less is known about the effect of the monsoon on sedimentation in coastal embayments with mouths of different geographic orientations. Good examples are Hampyeong and Yeoja bays along the west and south coasts, respectively. Both have narrow entrances, but their mouths open toward the northwest and the south, respectively. With mean tidal ranges of 3.46 and 3.2 m, respectively, the two bays experience similar tidal regimes and are hence excellent candidates to compare the effect of different exposure to the same regional monsoon climate on their respective sediment distribution patterns. The winter monsoon, in particular, is characterized by strong northwesterly winds that directly impact the west coast, but blow offshore along the south coast. For the purpose of this study, surficial sediment samples were collected from intertidal and subtidal flats of the two bays, both in summer and winter. Grain-size analyses were carried out by sieving (sand fraction) and Sedigraph (mud fraction). In the case of Yeoja Bay, the sediments consist mostly of mud (mean grain sizes of 5.4 to 8.8 phi). Seasonal changes are very subtle, the sediments being slightly coarser in summer when silt-dominated sediments are supplied by two streams to the northern parts of the bay in response to heavy rainfall. With the exception of the deeper tidal channels, Yeoja Bay is characterized by a thick mud blanket the year round, which is modulated by processes associated with the summer monsoon that predominantly blows from the east. Textural parameters suggest severely restricted sediment mixing on the subtidal and intertidal flats, the overall low energy situation preventing sands from reaching the tidal flats. The sediments of Hampyeong Bay, by contrast, are characterized by a distinct shoreward fining trend. Mean grain sizes average around -2.2 phi at the mouth and 8.2 phi near the shore of the inner bay. The textural relationships suggest progressive mixing between two hydraulic populations, the overall higher energy situation allowing sands to be transported onto the tidal flats in winter. In addition, a clear seasonal signal indicating deposition in summer and erosion in winter is observed, the latter probably being controlled by waves generated by strong northwesterly winds of the winter monsoon. The contrasting energy regimes controlling sediment distribution in the two bays are particularly well reflected in ternary diagrams of sand/silt/clay ratios and bivariate plots of textural parameters. The results clearly demonstrate that tidal sedimentation along the west coast of Korea is controlled by the more energetic winter monsoon, whereas along the south coast it is modulated by the less energetic summer monsoon. As a consequence, distinct seasonal changes are particularly pronounced along the west coast, whereas these are more subtle along the south coast. The orientation of bay mouths relative to the direction of wind associated with the summer and winter monsoon is thus identified as the main reason for the completely different sedimentation patterns observed on the subtidal and intertidal flats of the two bays.

Interactive effects of vegetation and sediment properties on erosion of salt marshes in the Northern Adriatic Sea.

PubMed

Lo, V B; Bouma, T J; van Belzen, J; Van Colen, C; Airoldi, L

2017-10-01

We investigated how lateral erosion control, measured by novel photogrammetry techniques, is modified by the presence of Spartina spp. vegetation, sediment grain size, and the nutrient status of salt marshes across 230 km of the Italian Northern Adriatic coastline. Spartina spp. vegetation reduced erosion across our study sites. The effect was more pronounced in sandy soils, where erosion was reduced by 80% compared to 17% in silty soils. Erosion resistance was also enhanced by Spartina spp. root biomass. In the absence of vegetation, erosion resistance was enhanced by silt content, with mean erosion 72% lower in silty vs. sandy soils. We found no relevant relationships with nutrient status, likely due to overall high nutrient concentrations and low C:N ratios across all sites. Our results contribute to quantifying coastal protection ecosystem services provided by salt marshes in both sandy and silty sediments. Copyright © 2017 Elsevier Ltd. All rights reserved.

Seagrass impact on sediment exchange between tidal flats and salt Marsh, and the sediment budget of shallow bays

USGS Publications Warehouse

Donatelli, Carmine; Ganju, Neil Kamal; Fagherazzi, Sergio; Leonardi, Nicoletta

2018-01-01

surroundings and are therefore frequently referred to as ecological engineers. The effect of seagrasses on coastal bay resilience and sediment transport dynamics is understudied. Here we use six historical maps of seagrass distribution in Barnegat Bay, USA, to investigate the role of these vegetated surfaces on the sediment storage capacity of shallow bays. Analyses are carried out by means of the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) numerical modeling framework. Results show that a decline in the extent of seagrass meadows reduces the sediment mass potentially stored within bay systems. The presence of seagrass reduces shear stress values across the entire bay, including unvegetated areas, and promotes sediment deposition on tidal flats. On the other hand, the presence of seagrasses decreases suspended sediment concentrations, which in turn reduces the delivery of sediment to marsh platforms. Results highlight the relevance of seagrasses for the long-term survival of coastal ecosystems, and the complex dynamics regulating the interaction between subtidal and intertidal landscapes.

Levels and distributions of organic pollutants in subtidal sediments from the Loire estuary: Are there any relationships with TTR-binding activity?

NASA Astrophysics Data System (ADS)

Couderc, M.; Gandolfi, F.; Zalouk-Vergnoux, A.; Beyeler, N.; Malleret, L.; Ambidina, I.; Kamari, A.; Blanchet-Letrouvé, I.; Mouneyrac, C.; Hamers, T.; Poirier, L.

2016-12-01

The Loire estuary runs through important urban sites with shipping, industrial and agricultural activities, being the receptacle of diffusive pollutants comprising, a mixture of contaminants such as persistent organic pollutants (POPs). This work was set out to evaluate the occurrence of thyroid endocrine disruptors in sediments of this estuary. Sediments were collected in September 2012 and April 2013, in subtidal zones along the estuary. Targeted chemical analyses of five classes of pollutants, i.e. polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), and bisphenol A (BPA) were performed in sediment extracts. Extracts were further tested for their thyroid hormone (TH) disrupting potency to compete with TH for binding to its transporter protein transthyretin (TTR). The Haute-Indre site was characterized by a significant PAH contamination whereas Saint-Nazaire, Bellevue and Rezé would be particularly contaminated by PCBs. These observations could be linked to the different type of anthropogenic activities taking place close to these sites. Donges, Mindin and Paimboeuf were the sampling sites displaying the lowest contamination in PAHs, APs, PCBs and PBDEs. No inter-site difference could be observed for TTR-binding activity, which should be attributed to different compounds than the chemically analyzed compounds, as confirmed by PCA analyses. Furthermore, the TTR-binding potencies of the extracts were relatively low compared to data from literature. More investigations on the quantification of PCB and PBDE hydroxylated metabolites and other known endocrine disruptors such as pesticides or perfluorinated compounds could be considered, as well as bioassays highlighting other endocrine disrupting effects.

Soft-sediment deformation structures from an ice-marginal storm-tide interactive system, Permo-Carboniferous Talchir Formation, Talchir Coalbasin, India

NASA Astrophysics Data System (ADS)

Bhattacharya, H. N.; Bhattacharya, Biplab

2010-01-01

Permo-Carboniferous Talchir Formation, Talchir Coalbasin, India, records sedimentation during a phase of climatic amelioration in an ice-marginal storm-affected shelf. Evidences of subtidal processes are preserved only under thick mud drapes deposited during waning storm phases. Various soft-sediment deformation structures in some sandstone/siltstone-mudstone interbeds, like syn-sedimentary faults, deformed laminations, sand-silt flows, convolute laminations and various flame structures, suggest liquefaction and fluidization of the beds due to passage of syn-depositional seismic shocks. In the Late Paleozoic ice-marginal shelf, such earthquake tremors could be generated by crustal movements in response to glacioisostatic adjustments of the basin floor.

Sediment grain-size characteristics and relevant correlations to the aeolian environment in China's eastern desert region.

PubMed

Zhang, Chunlai; Shen, Yaping; Li, Qing; Jia, Wenru; Li, Jiao; Wang, Xuesong

2018-06-15

To identify characteristics of aeolian activity and the aeolian environment in China's eastern desert region, this study collected surface sediment samples from the main desert and sandy lands in this region: the Hobq Desert and the Mu Us, Otindag, Horqin, and Hulunbuir sandy lands. We analyzed the grain-size characteristics and their relationships to three key environmental indicators: drift potential, the dune mobility index, and vegetation cover. The main sediment components are fine to medium sands, with poor (Hulunbuir) to moderate (all other areas) sorting, of unimodal to bimodal distribution. This suggests that improved sorting is accomplished by the loss of both relatively coarser and finer grains. Since 2000, China's eastern desert region has generally experienced low wind energy environmental conditions, resulting in decreased dune activity. In the Hobq Desert, however, the dry climate and sparse vegetation, in conjunction with the most widely distributed mobile dune area in the eastern desert region, have led to frequent and intense aeolian activity, including wind erosion, sand transport, and deposition, resulting in conditions for good sediment sorting. In the Mu Us, Otindag, and Horqin sandy lands, mosaic distribution has resulted from wind erosion-dominated and deposition-dominated aeolian environments. In the Hulunbuir Sandy Land, high precipitation, low temperatures, and steppe vegetation have resulted in well-developed soils; however, strong winds and flat terrain have created an aeolian environment dominated by wind erosion. Copyright © 2018. Published by Elsevier B.V.

Subtidal Bathymetric Changes by Shoreline Armoring Removal and Restoration Projects

NASA Astrophysics Data System (ADS)

Wallace, J.

2016-12-01

The Salish Sea, a region with a diverse coastline, is altered by anthropogenic shoreline modifications such as seawalls. In recent years, local organizations have moved to restore these shorelines. Current research monitors the changes restoration projects have on the upper beach, lower beach, and intertidal, however little research exists to record possible negative effects on the subtidal. The purpose of this research is to utilize multibeam sonar bathymetric data to analyze possible changes to the seafloor structure of the subtidal in response to shoreline modification and to investigate potential ecosystem consequences of shoreline alteration. The subtidal is home to several species including eelgrass (Zostera marina). Eelgrass is an important species in Puget Sound as it provides many key ecosystem functions including providing habitat for a wide variety of organisms, affecting the physics of waves, and sediment transport in the subtidal. Thus bathymetric changes could impact eelgrass growth and reduce its ability to provide crucial ecosystem services. Three Washington state study sites of completed shoreline restoration projects were used to generate data from areas of varied topographic classification, Seahurst Park in Burien, the Snohomish County Nearshore Restoration Project in Everett, and Cornet Bay State Park on Whidbey Island. Multibeam sonar data was acquired using a Konsberg EM 2040 system and post-processed in Caris HIPS to generate a base surface of one-meter resolution. It was then imported into the ArcGIS software suite for the generation of spatial metrics. Measurements of change were calculated through a comparison of historical and generated data. Descriptive metrics generated included, total elevation change, percent area changed, and a transition matrix of positive and negative change. Additionally, pattern metrics such as, surface roughness, and Bathymetric Position Index (BPI), were calculated. The comparison of historical data to new data at each site allows for a calculation of change and therefore helps to identify any positive or negative consequences of shoreline alteration work. A better understanding of the impacts of shoreline restoration will help to review the current procedures and identify any that need improvement as to reduce impacts to the subtidal ecosystem.

Age determination and provenance of sandy sediments possibly hosting gas hydrate in the eastern margin of Japan Sea

NASA Astrophysics Data System (ADS)

Uchida, T.; Takashima, I.; Sasaki, S.; Matsumoto, R.

2012-12-01

In 2010 the MD179 project was undertaken by the Marion Dufresne aiming at recovery of deep seated gas and gas hydrate, methane induced carbonate, and deep sediments in order to develop the geologic model of gas hydrate accumulation and evaluate the possible environmental impact of gas hydrate for the last glacial-interglacial cycles. Sediment samples below the seafloor were obtained in the Umitaka Spur, Joetsu Channel, Toyama Trough, Japan Basin, Nishi Tsugaru and Okushiri Ridge areas by the cruise. Small amounts of sandy sediment have been retrieved as thin intercalations in Pleistocene and Holocene silty layers, where trace fossils and strong bioturbations are commonly observed. Those sandy sediments consist of very fine- to fine-grained sand grains, and are sometimes tuffaceous. Pore-size distribution measurements and thin-section observations of these arenite sands were carried out, which indicates that porosities of silty sediments are around 50 % but those of arenites range from 42 to 52 %, of which mean pore sizes and permeabilities are larger than those of silty sediments. These coarser sediments might have been transported approximately around 3 to 30 ka according to the tephra ages, where supplying sediments might have not been abundant due to sea level fluctuation during the Pleistocene ice age. While the presence of gas hydrate in intergranular pores of arenite sands has not been confirmed, the soupy occurrence in recovered sediments may strongly indicate the presence of gas hydrate filling the intergranular pore system of arenite sands that is called pore-space hydrates. They have been recognized till now in the Mallik as well as in the Nankai Trough areas, which are considered to be common even in the subsurface sandy sediments at the eastern margin of Japan Sea. Time of deposition of coarse-grained sediments can be recognized by the thermoluminescence (TL) dating method. The TL dating works on the principle that materials containing naturally occurring radioactive isotopes such as uranium, thorium or potassium are subject to low levels of radiation. Measurements of TL dating have been completed only for seven samples, which indicate 48 to 980 ka in age. Additionally they usually provide information about the provenance and the sedimentary paleoenvironment when the sediments deposited. The TL emission spectra along temperature increase from 100 to 400 degree C are divided into two types; the unimodal type and the bimodal type, which may indicate the histories of sediment transportation and their provenances. This study was performed as a part of the MH21 Research Consortium on methane hydrate in Japan.

Hurricane Sandy washover deposits on southern Long Beach Island, New Jersey

USGS Publications Warehouse

Bishop, James M.; Richmond, Bruce M.; Zaremba, Nicholas J.; Lunghino, Brent D.; Kane, Haunani H.

2016-07-22

Sedimentologic and topographic data from Hurricane Sandy washover deposits were collected from southern Long Beach Island, New Jersey, in order to document changes to the barrier-island beaches, dunes, and coastal wetlands caused by Hurricane Sandy and subsequent storm events. These data will provide a baseline dataset for use in future coastal change descriptive and predictive studies and assessments. The data presented here were collected as part of the U.S. Geological Survey’s Barrier Island and Estuarine Wetland Physical Change Assessment Project (http://coastal.er.usgs.gov/sandy-wetland-assessment/), which aims to assess ecological and societal vulnerability that results from long- and short-term physical changes to barrier islands and coastal wetlands. This report describes data that were collected in April 2015, approximately 2½ years after Hurricane Sandy’s landfall on October 29, 2012. During the field campaign, washover deposits were photographed and described, and sediment cores, sediment samples, and surface-elevation data were collected. Data collected during this study, including sample locations and elevations, core photographs, computed tomography scans, descriptive core logs, sediment grain-size data, and accompanying Federal Geographic Data Committee metadata, are available in the associated U.S. Geological Survey data release (Bishop and others, 2016; http://dx.doi.org/10.5066/F7PK0D7S).

Evolution of mud-capped dredge pits following excavation: sediment trapping and slope instability

NASA Astrophysics Data System (ADS)

Obelcz, J.; Xu, K.; Bentley, S. J.; Li, C.; Miner, M. D.; O'Connor, M. C.; Wang, J.

2016-02-01

Many fluvial channels incised the Northern Gulf of Mexico inner continental shelf during the late Quaternary. Mud-capped dredge pits (MCDPs), which are generally elongate and deep (8-10 m) excavations, target sandy fluvial channel deposits for coastal restoration projects. The morphological evolution of dredge excavations in noncohesive sandy substrate is well studied, but MCDPs have up to a several-meter-thick veneer of Holocene shelf mud overlying sandy channel deposits. This stratigraphy is hypothesized to result in more complex post-dredge morphology than pit walls simply slumping to the angle of repose shortly after excavation. Numerical modeling of MCDP post-dredge response conducted prior to excavation indicates pit walls may retrogressively fail, which is accounted for in pit design by assigning no-dredge setback buffers from pipelines or cultural and environmental resources. To validate model results and test effectiveness of setback buffers, a geophysical survey of the Sandy Point MCDP (20 km west of the Mississippi River Delta in 10m deep water), where 1.7 million m3 of sandy sediment was excavated in 2012, was conducted May 2015. A total of 84 line-km of high-resolution chirp subbottom and a 27 km2 grid of swath bathymetry and sidescan sonar were collected. The data indicate the dredge pit walls are differentially slumping, with the western pit wall in a more active state of failure than the eastern wall. The western failures morphologically resemble features observed along the muddy Mississippi River Delta Front at water depths of 20-100 m, including bowl-shaped collapse failures and retrogressive stair-stepped slumps; these failures may play a key role in evaluating the distance of setback buffer zone to pipelines. These features indicate the cohesive mud overlying the sandy infill has a prominent role in pit wall stability. A 0.5-1 m thick acoustically transparent package overlies the entire pit floor (interpreted as a possible fluid mud layer), overlying 1-3 m of post-dredge deposition that is concentrated along the western wall and center of the pit. The Sandy Point MCDP lies within a clockwise gyre, and its relief may serve as a significant trap of suspended sediment. These findings emphasize the role MCDPs play in sediment dynamics as well as their potential for submarine geohazards.

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

Jewett, S.C.; Dean, T.A.; Smith, R.O.

Injuries to several of the dominant taxa in the nearshore subtidal community were observed in the heavily oiled portions of western Prince William Sound following the Exxon Valdez oil spill of March 1989. The initial effects were most pronounced in more protected eelgrass and silled fjord habitats, where PAH (polycyclic aromatic hydrocarbon) concentrations in sediments exceeded 1000 ng g-1 in 1990. By 1993, PAH concentrations in sediments declined to less than 100 ng g-1, and there were far fewer differences between oiled and control sites with respect to the abundance of dominant plant, invertebrate, and fish taxa. However, not allmore » taxa had recovered fully.« less

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

NASA Astrophysics Data System (ADS)

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

2005-12-01

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

Hydrodynamic sorting and transport of terrestrially derived organic carbon in sediments of the Mississippi and Atchafalaya Rivers

NASA Astrophysics Data System (ADS)

Bianchi, Thomas S.; Galler, John J.; Allison, Mead A.

2007-06-01

Over the course of two years, four cruises were conducted at varying levels of discharge in the lower Mississippi and Atchafalaya Rivers (MR and AR) where grab samples were collected from sand- and mud-dominated sediments. The tetramethylammonium hydroxide (TMAH) thermochemolysis method was used to determine sources of terrestrially derived organic carbon (OC) in these two sediment types, to examine the effects of hydrodynamic sorting on lignin sources in river sediments. Average lignin concentrations in the lower MR were 1.4 ± 1.1 mg gOC -1 at English Turn (ET) and 10.4 ± 27.4 mg gOC -1 at Venice. Using these concentrations, annual lignin fluxes to the Gulf of Mexico, from tidal and estuarine mud remobilization at ET and Venice, were 3.1 ± 2.5 × 10 5 kg and 11.4 ± 30.0 × 10 5 kg, respectively. Much of the lignin-derived materials in muddy sediments appeared to be derived from non-woody grass-like sources - which should decay more quickly than the woody materials typically found in the sandy deposits. The average total OC% (1.93 ± 0.47) of English Turn sands yields an annual flux of 0.34 ± 0.09 × 10 9 kg. Lignin flux in the English Turn sands (3.6 ± 2.6 mg gC -1) using the numbers above would be 12.2 ± 9.4 × 10 5 kg. The extensive amounts of sand-sized woody materials (coffee-grinds) found in the sandy sediments in both the AR and MR are likely derived from woody plant materials. This is the first time it has been demonstrated that sandy sediments in the MR provide an equally important pathway (compared to muds) for the transport of terrestrially derived organic matter to the northern Gulf of Mexico. Using the AR average %OC in sand (1.16 ± 0.72), we estimated an annual flux of OC to the shelf of 0.13 ± 0.07 × 10 9 kg. Lignin flux for AR sands was estimated to be 12.4 ± 12.1 × 10 5 kg. Despite the high error associated with these numbers, we observe for the first time that the flux of lignin in sandy sediments in the AR to the northern Gulf of Mexico is comparable to that found in the MR. These results further support the likelihood of grain-size related hydrodynamic sorting of terrestrially derived organic carbon in the lower Mississippi and Atchafalaya Rivers, suggesting that there is a distinct sandy sediment organic fraction contributed by major rivers to the global carbon cycle.

Significance of nearshore trace-fossil assemblages of the cambro-ordovician deadwood formation and Aladdin Sandstone, South Dakota

USGS Publications Warehouse

Stanley, T.M.; Feldmann, R.M.

1998-01-01

The Cambro-Ordovician Deadwood Formation and Aladdin Sandstone represent intertidal and subtidal, nearshore deposystems that contain few well-preserved body fossils, but contain abundant trace fossils. The present study uses the much neglected trace-fossil fauna to describe the diverse paleoenvironments represented in the Deadwood-Aladdin deposystems, and to better understand the environmental conditions that controlled benthic life in the Early Paleozoic. The Deadwood-Aladdin ichnotaxa can be separated into three distinct assemblages based on the changing sedimentologic and hydrodynamic conditions that existed across the Cambro-Ordovician shelf. Trace-fossil assemblages and corresponding lithofacies characteristics indicate that the Deadwood-Aladdin deposystems formed within an intertidal-flat and subtidal-shelf environment. Based on the distribution and numbers of preserved ichnotaxa, the intertidal flat can be subdivided further into an ecologically stressful inner sand-flat environment, and a more normal marine outer sand-flat environment, both of which belong to a mixed, Skolithos-Cruziana softground ichnofacies. The inner sand flat is characterized by low diversity, low numbers, and a general lack of complexly constructed ichnotaxa. Trace fossils common to both assemblages tend to be smaller in the inner flat compared to the outer sand flat. Taphonomic effects, such as substrate type and sediment heterogeneity, also aid in differentiating between the inner and outer sand-flat assemblages. The subtidal shelf environment is categorized in the Cruziana Ichnofacies. Ichnological evidence of periodic tempestite deposition and hardground development within this subtidal regime is manifested by high diversity and low abundance of ichnogenera.

Assessment of grass root effects on soil piping in sandy soils using the pinhole test

NASA Astrophysics Data System (ADS)

Bernatek-Jakiel, Anita; Vannoppen, Wouter; Poesen, Jean

2017-10-01

Soil piping is an important land degradation process that occurs in a wide range of environments. Despite an increasing number of studies on this type of subsurface erosion, the impact of vegetation on piping erosion is still unclear. It can be hypothesized that vegetation, and in particular plant roots, may reduce piping susceptibility of soils because roots of vegetation also control concentrated flow erosion rates or shallow mass movements. Therefore, this paper aims to assess the impact of grass roots on piping erosion susceptibility of a sandy soil. The pinhole test was used as it provides quantitative data on pipeflow discharge, sediment concentration and sediment discharge. Tests were conducted at different hydraulic heads (i.e., 50 mm, 180 mm, 380 mm and 1020 mm). Results showed that the hydraulic head was positively correlated with pipeflow discharge, sediment concentration and sediment discharge, while the presence of grass roots (expressed as root density) was negatively correlated with these pipeflow characteristics. Smaller sediment concentrations and sediment discharges were observed in root-permeated samples compared to root-free samples. When root density exceeds 0.5 kg m- 3, piping erosion rates decreased by 50% compared to root-free soil samples. Moreover, if grass roots are present, the positive correlation between hydraulic head and both sediment discharge and sediment concentration is less pronounced, demonstrating that grass roots become more effective in reducing piping erosion rates at larger hydraulic heads. Overall, this study demonstrates that grass roots are quite efficient in reducing piping erosion rates in sandy soils, even at high hydraulic head (> 1 m). As such, grass roots may therefore be used to efficiently control piping erosion rates in topsoils.

Contribution of Methane Accumulation and Pore Water Flow to Forming High Concentration of Gas Hydrate in Sandy Sediments

NASA Astrophysics Data System (ADS)

Uchida, T.; Waseda, A.; Fujii, T.

2006-12-01

The geological and geophysical evaluations have suggested worldwide methane contents in gas hydrate beneath deep sea floors as well as permafrost-related zones to about twice the total reserves of conventional and unconventional hydrocarbon. In 1998 and 2002 Mallik wells were drilled in the Canadian Arctic that clarified the characteristics of gas hydrate-concentrated sandy layers at depths from 890 to 1110 m beneath the permafrost zone. Continuous downhole well log data, anomalies of chloride contents in pore waters, core temperature depression as well as visible gas hydrates have confirmed the highly saturated pore-space hydrate as intergranular pore filling, whose saturations are evaluated higher than 80 percent in pore volume. In the Nankai Trough forearc basins and accretionary prisms developed and BSRs (bottom simulating reflectors) have been recognized widely, where the multiple wells were drilled in 2000 and 2004, and revealed the presence of pore-space hydrate in sandy layers. It is remarked that there are many similar features in appearance and characteristics between the Mallik and Nankai Trough areas with observations of well- interconnected and highly saturated pore-space hydrate. High concentration of gas hydrate may need original pore space large enough to occur within a host sandy sediment, and this appears to be a similar mode for conventional petroleum accumulations. The distribution of a porous and coarser-grained sandy sediments should be one of the most important factors controlling occurrences and distributions of gas hydrate, as well as physicochemical conditions. Supplying methane for forming deep marine gas hydrate is commonly attributed to microbial conversion of organic material within the zone of stability or to migration of methane-containing fluids from a deeper source area. Pore water flows are considered to a macroscopic migration through faults/fractures and a microscopic flow in intergranular pore systems of sediment. We should assess the influence of methane supply on observable features of hydrate occurrences.

Shoreface response and recovery to Hurricane Sandy: Fire Island, NY

USGS Publications Warehouse

Nelson, Timothy R.; Hapke, Cheryl J.; Wang, Ping; Rosati, Julie D.; Cheng, Jun

2015-01-01

The shoreface of Fire Island was extensively modified by Hurricane Sandy and subsequent storms in the following winter months. The changes were evaluated using various morphometrics of the shoreface from four bathymetric surveys, one prior to Hurricane Sandy, and three over the course of twenty months following Sandy. The datasets show that the nearshore bar system moved offshore to deeper water depths following Hurricane Sandy with volume lost from the subaerial beach and surfzone. Following the offshore shift, the nearshore bar system increased in size, the trough deepened, and there has been gradual landward movement of the nearshore bar. The steepening of the upper shoreface, landward translation of the profile, and loss of sediment is indicative of barrier island transgression.

Seagrass Impact on Sediment Exchange Between Tidal Flats and Salt Marsh, and The Sediment Budget of Shallow Bays

NASA Astrophysics Data System (ADS)

Donatelli, Carmine; Ganju, Neil Kamal; Fagherazzi, Sergio; Leonardi, Nicoletta

2018-05-01

Seagrasses are marine flowering plants that strongly impact their physical and biological surroundings and are therefore frequently referred to as ecological engineers. The effect of seagrasses on coastal bay resilience and sediment transport dynamics is understudied. Here we use six historical maps of seagrass distribution in Barnegat Bay, USA, to investigate the role of these vegetated surfaces on the sediment storage capacity of shallow bays. Analyses are carried out by means of the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) numerical modeling framework. Results show that a decline in the extent of seagrass meadows reduces the sediment mass potentially stored within bay systems. The presence of seagrass reduces shear stress values across the entire bay, including unvegetated areas, and promotes sediment deposition on tidal flats. On the other hand, the presence of seagrasses decreases suspended sediment concentrations, which in turn reduces the delivery of sediment to marsh platforms. Results highlight the relevance of seagrasses for the long-term survival of coastal ecosystems, and the complex dynamics regulating the interaction between subtidal and intertidal landscapes.

Environmental implications of the use of sulfidic back-bay sediments for dune reconstruction — Lessons learned post Hurricane Sandy

USGS Publications Warehouse

Plumlee, Geoffrey S.; Benzel, William M.; Hoefen, Todd M.; Hageman, Philip L.; Morman, Suzette A.; Reilly, Timothy J.; Adams, Monique; Berry, Cyrus J.; Fischer, Jeffrey; Fisher, Irene

2016-01-01

Some barrier-island dunes damaged or destroyed by Hurricane Sandy's storm surges in October 2012 have been reconstructed using sediments dredged from back bays. These sand-, clay-, and iron sulfide-rich sediments were used to make berm-like cores for the reconstructed dunes, which were then covered by beach sand. In November 2013, we sampled and analyzed partially weathered materials collected from the cores of reconstructed dunes. There are generally low levels of metal toxicants in the reconstructed dune materials. However oxidation of reactive iron sulfides by percolating rainwater produces acid-sulfate pore waters, which evaporate during dry periods to produce efflorescent gypsum and sodium jarosite salts. The results suggest use of sulfidic sediments in dune reconstruction has both drawbacks (e.g., potential to generate acid runoff from dune cores following rainfall, enhanced corrosion of steel bulwarks) and possible benefits (e.g., efflorescent salts may enhance structural integrity).

Hydrography and bottom boundary layer dynamics: Influence on inner shelf sediment mobility, Long Bay, North Carolina

USGS Publications Warehouse

Davis, L.A.; Leonard, L.A.; Snedden, G.A.

2008-01-01

This study examined the hydrography and bottom boundary-layer dynamics of two typical storm events affecting coastal North Carolina (NC); a hurricane and the passages of two small consecutive extratropical storms during November 2005. Two upward-looking 1200-kHz Acoustic Doppler Current Profilers (ADCP) were deployed on the inner shelf in northern Long Bay, NC at water depths of less than 15 m. Both instruments profiled the overlying water column in 0.35 in bins beginning at a height of 1.35 in above the bottom (mab). Simultaneous measurements of wind speed and direction, wave and current parameters, and acoustic backscatter were coupled with output from a bottom boundary layer (bbl) model to describe the hydrography and boundary layer conditions during each event. The bbl model also was used to quantify sediment transport in the boundary layer during each storm. Both study sites exhibited similar temporal variations in wave and current magnitude, however, wave heights during the November event were higher than waves associated with the hurricane. Near-bottom mean and subtidal currents, however, were of greater magnitude during the hurricane. Peak depth-integrated suspended sediment transport during the November event exceeded transport associated with the hurricane by 25-70%. Substantial spatial variations in sediment transport existed throughout both events. During both events, along-shelf sediment transport exceeded across-shelf transport and was related to the magnitude and direction of subtidal currents. Given the variations in sediment type across the bay, complex shoreline configuration, and local bathymetry, the sediment transport rates reported here are very site specific. However, the general hydrography associated with the two storms is representative of conditions across northern Long Bay. Since the beaches in the study area undergo frequent renourishment to counter the effects of beach erosion, the results of this study also are relevant to coastal management decision-making. Specifically, these issues include 1) identification of municipalities that should share the cost for renourishment given the likelihood for significant along-shelf sand movement and 2) appropriate timing of sand placement with respect to local climatology and sea-turtle nesting restrictions.

Marine Microbial Gene Abundance and Community Composition in Response to Ocean Acidification and Elevated Temperature in Two Contrasting Coastal Marine Sediments.

PubMed

Currie, Ashleigh R; Tait, Karen; Parry, Helen; de Francisco-Mora, Beatriz; Hicks, Natalie; Osborn, A Mark; Widdicombe, Steve; Stahl, Henrik

2017-01-01

Marine ecosystems are exposed to a range of human-induced climate stressors, in particular changing carbonate chemistry and elevated sea surface temperatures as a consequence of climate change. More research effort is needed to reduce uncertainties about the effects of global-scale warming and acidification for benthic microbial communities, which drive sedimentary biogeochemical cycles. In this research, mesocosm experiments were set up using muddy and sandy coastal sediments to investigate the independent and interactive effects of elevated carbon dioxide concentrations (750 ppm CO 2 ) and elevated temperature (ambient +4°C) on the abundance of taxonomic and functional microbial genes. Specific quantitative PCR primers were used to target archaeal, bacterial, and cyanobacterial/chloroplast 16S rRNA in both sediment types. Nitrogen cycling genes archaeal and bacterial ammonia monooxygenase ( amoA ) and bacterial nitrite reductase ( nirS ) were specifically targeted to identify changes in microbial gene abundance and potential impacts on nitrogen cycling. In muddy sediment, microbial gene abundance, including amoA and nirS genes, increased under elevated temperature and reduced under elevated CO 2 after 28 days, accompanied by shifts in community composition. In contrast, the combined stressor treatment showed a non-additive effect with lower microbial gene abundance throughout the experiment. The response of microbial communities in the sandy sediment was less pronounced, with the most noticeable response seen in the archaeal gene abundances in response to environmental stressors over time. 16S rRNA genes ( amoA and nirS ) were lower in abundance in the combined stressor treatments in sandy sediments. Our results indicated that marine benthic microorganisms, especially in muddy sediments, are susceptible to changes in ocean carbonate chemistry and seawater temperature, which ultimately may have an impact upon key benthic biogeochemical cycles.

Effects of shoreline discharge of iron mine tailings on a marine soft-bottom community in northern Chile.

PubMed

Lancellotti, D A; Stotz, W B

2004-02-01

This study evaluates the magnitude and extension of the impact produced by the discharge of inert allochthonous materials, including clays and particulate iron, on macrobenthic soft-bottom assemblages in the subtidal zone of a coastal bay in north-central Chile. An average of 118 Ton h(-1) of finely divided solids were discharged into the rocky intertidal zone of the bay for a period of over 16 years, producing continuous turbidity in the water column and sedimentation in the subtidal zone. Data obtained four months before cessation of the discharge showed that the macrofauna present at 20 and 50 m depth in the bay suffered an important decrease in abundance and species richness, low diversity/high dominance, and deep changes in community structure related to the discharge. The faunal assemblages present at 110 m depth did not show effects from the discharge, suggesting that the impact was limited to the inner part of the bay. The impoverished faunal aggregates at 20 and 50 m depth showed exclusive domination by the Lumbrineris bifilaris (polychaete)-Diastylis tongoyensis (cumacean) association, representing a simple trophic guild of deposit feeders. The complete absence of opportunistic species such as capitellid, spionid, and/or cirratulid polychaetes may be associated with the turbidity and sedimentation levels in the bay.

The role of certain infauna and vascular plants in the mediation of redox reactions in marine sediments

NASA Technical Reports Server (NTRS)

Hines, Mark E.

1992-01-01

The mechanisms by which certain animals and plants affect redox processes in sediments was examined by studying three environments: (1) subtidal sediments dominated by the deposit-feeding polychaete Heteromastus filiformis; (2) a saltmarsh inhabited by the tall form of Spartina alterniflora; and (3) tropical carbonate sediments inhabited by three species of seagrasses. S-35-sulfide production rates were compared to pool sizes of dissolved sulfide and dissolved iron. In all of the sediments studied, rates of sulfide reduction were enhanced by macroorganisms while the rate of turnover of dissolved sulfide increased. The polychaete enhanced microbial activity and redox cycling primarily by subducting particles of organic matter and oxidized iron during sediment reworking. The Spartina species enhanced anaerobic activity by transporting primarily dissolved organic matter and oxidants. Although the final result of both animal and plant activities was the enhancement of sub-surface cycling of sulfur and iron, decreased dissolved sulfide and increased dissolved iron concentrations, the mechanisms which produced these results differed dramatically.

BIOREMEDIATION OF OIL-CONTAMINATED FINE SEDIMENTS.

EPA Science Inventory

Bioremediation of oil contamination has been shown to be effective for cobble and sandy shorelines. To assess the operational limitations of this technology, this project studied its potential to treat buried oil in fine sediments. The effectiveness of bioremediation by nutrient ...

Laboratory Study of Quaternary Sediment Resistivity Related to Groundwater Contamination at Mae-Hia Landfill, Mueang District, Chiang Mai Province

NASA Astrophysics Data System (ADS)

Sichan, N.

2007-12-01

This study was aimed to understand the nature of the resistivity value of the sediment when it is contaminated, in order to use the information solving the obscure interpretation in the field. The pilot laboratory experiments were designed to simulate various degree of contamination and degree of saturation then observe the resulting changes in resistivity. The study was expected to get a better understanding of how various physical parameters effect the resistivity values in term of mathematic function. And also expected to apply those obtained function to a practical quantitatively interpretation. The sediment underlying the Mae-Hia Landfill consists of clay-rich material, with interfingerings of colluvium and sandy alluvium. A systematic study identified four kinds of sediment, sand, clayey sand, sandy clay, and clay. Representative sediment and leachate samples were taken from the field and returned to the laboratory. Both the physical and chemical properties of the sediments and leachate were analyzed to delineate the necessary parameters that could be used in Archie's equation. Sediment samples were mixed with various concentration of leachate solutions. Then the resistivity values were measured at various controlled steps in the saturation degree in a well- calibrated six-electrode model resistivity box. The measured resistivity values for sand, clayey sand, sandy clay when fully and partly saturated were collected, then plotted and fitted to Archie's equation, to obtain a mathematical relationship between bulk resistivity, porosity, saturation degree and resistivity of pore fluid. The results fit well to Archie's equation, and it was possible to determine all the unknown parameters representative of the sediment samples. For sand, clayey sand, sandy clay, and clay, the formation resistivity factors (F) are 2.90, 5.77, 7.85, and 7.85 with the products of cementation factor (m) and the pore geometry factors (a) (in term of -am) are 1.49, -1.63, -1.92, -2.24 and the saturation exponents (n) are 2.06, 2.58, 3.52, and 2.46, respectively. These results were used to reinterpret the existing resistivity data of this area. The result of this reinterpretation is a map showing the quantitative distribution of the contaminant plume in the vicinity of the Mae-Hia Landfill.

Depositional facies, environments and sequence stratigraphic interpretation of the Middle Triassic-Lower Cretaceous (pre-Late Albian) succession in Arif El-Naga anticline, northeast Sinai, Egypt

NASA Astrophysics Data System (ADS)

El-Azabi, M. H.; El-Araby, A.

2005-01-01

The Middle Triassic-Lower Cretaceous (pre-Late Albian) succession of Arif El-Naga anticline comprises various distinctive facies and environments that are connected with eustatic relative sea-level changes, local/regional tectonism, variable sediment influx and base-level changes. It displays six unconformity-bounded depositional sequences. The Triassic deposits are divided into a lower clastic facies (early Middle Triassic sequence) and an upper carbonate unit (late Middle- and latest Middle/early Late Triassic sequences). The early Middle Triassic sequence consists of sandstone with shale/mudstone interbeds that formed under variable regimes, ranging from braided fluvial, lower shoreface to beach foreshore. The marine part of this sequence marks retrogradational and progradational parasequences of transgressive- and highstand systems tract deposits respectively. Deposition has taken place under warm semi-arid climate and a steady supply of clastics. The late Middle- and latest Middle/early Late Triassic sequences are carbonate facies developed on an extensive shallow marine shelf under dry-warm climate. The late Middle Triassic sequence includes retrogradational shallow subtidal oyster rudstone and progradational lower intertidal lime-mudstone parasequences that define the transgressive- and highstand systems tracts respectively. It terminates with upper intertidal oncolitic packstone with bored upper surface. The next latest Middle/early Late Triassic sequence is marked by lime-mudstone, packstone/grainstone and algal stromatolitic bindstone with minor shale/mudstone. These lower intertidal/shallow subtidal deposits of a transgressive-systems tract are followed upward by progradational highstand lower intertidal lime-mudstone deposits. The overlying Jurassic deposits encompass two different sequences. The Lower Jurassic sequence is made up of intercalating lower intertidal lime-mudstone and wave-dominated beach foreshore sandstone which formed during a short period of rising sea-level with a relative increase in clastic supply. The Middle-Upper Jurassic sequence is represented by cycles of cross-bedded sandstone topped with thin mudstone that accumulated by northerly flowing braided-streams accompanying regional uplift of the Arabo-Nubian shield. It is succeeded by another regressive fluvial sequence of Early Cretaceous age due to a major eustatic sea-level fall. The Lower Cretaceous sequence is dominated by sandy braided-river deposits with minor overbank fines and basal debris flow conglomerate.

Transport of Gas and Solutes in Permeable Estuarine Sediments

DTIC Science & Technology

2012-09-30

produce his Ph.D. dissertation based on this reserach . The acoustic method for detecting and measuring small gas bubbles in marine sands. This...the detection and quantification of small free gas volumes in sandy coastal sediments. After introducing and explaining the instrument, the paper ...influence the sediment erosion threshold, biogeochemical zonations, living space for organisms and thereby the role of the sediments in the cycles of

Lasting Impact of a Tsunami Event on Sediment-Organism Interactions in the Ocean

NASA Astrophysics Data System (ADS)

Seike, Koji; Sassa, Shinji; Shirai, Kotaro; Kubota, Kaoru

2018-02-01

Although tsunami sedimentation is a short-term phenomenon, it may control the long-term benthic environment by altering seafloor surface characteristics such as topography and grain-size composition. By analyzing sediment cores, we investigated the long-term effect of the 2011 tsunami generated by the Tohoku Earthquake off the Pacific coast of Japan on sediment mixing (bioturbation) by an important ecosystem engineer, the heart urchin Echinocardium cordatum. Recent tsunami deposits allow accurate estimation of the depth of current bioturbation by E. cordatum, because there are no preexisting burrows in the sediments. The in situ hardness of the substrate decreased significantly with increasing abundance of E. cordatum, suggesting that echinoid bioturbation softens the seafloor sediment. Sediment-core analysis revealed that this echinoid rarely burrows into the coarser-grained (medium-grained to coarse-grained) sandy layer deposited by the 2011 tsunami; thus, the vertical grain-size distribution resulting from tsunami sedimentation controls the depth of E. cordatum bioturbation. As sandy tsunami layers are preserved in the seafloor substrate, their restriction on bioturbation continues for an extended period. The results demonstrate that understanding the effects on seafloor processes of extreme natural events that occur on geological timescales, including tsunami events, is important in revealing continuing interactions between seafloor sediments and marine benthic invertebrates.

Glider Observations of Sediment Resuspension in a Middle Atlantic Bight Fall Transition Storm

DTIC Science & Technology

2008-06-14

response within the lower water column only was observed for sediment resuspension on the outer shelf during Tropical Storm Ernesto , which also occurred when...sediment types in the MAB was summarized by Amato (1994) using data mostly from U.S. Geological Survey databases or state geological surveys and...shelf ( Amato 1994) and suggests that the storm resuspended the sediment from the sandy bottom. Physical processes driving the sediment resuspension

Rare earth element compositions of core sediments from the shelf of the South Sea, Korea: Their controls and origins

NASA Astrophysics Data System (ADS)

Jung, Hoi-Soo; Lim, Dhongil; Choi, Jin-Yong; Yoo, Hae-Soo; Rho, Kyung-Chan; Lee, Hyun-Bok

2012-10-01

Rare earth elements (REEs) of bulk sediments and heavy mineral samples of core sediments from the South Sea shelf, Korea, were analyzed to determine the constraints on REE concentrations and distribution patterns as well as to investigate their potential applicability for discriminating sediment provenance. Bulk sediment REEs showed large variation in concentrations and distribution patterns primarily due to grain size and carbonate dilution effects, as well as due to an abundance of heavy minerals. In the fine sandy sediments (cores EZ02-15 and 19), in particular, heavy minerals (primarily monazite and titanite/sphene) largely influenced REE compositions. Upper continental crust-normalized REE patterns of these sand-dominated sediments are characterized by enriched light REEs (LREEs), because of inclusion of heavy minerals with very high concentrations in LREEs. Notably, such a strong LREE enrichment is also observed in Korean river sediments. So, a great care must be taken when using the REE concentrations and distribution patterns of sandy and coarse silty shelf sediments as a proxy for discriminating sediment provenance. In the fine-grained muddy sediments with low heavy mineral abundance, in contrast, REE fractionation ratios and their UCC-normalized patterns seem to be reliable proxies for assessing sediment provenance. The resultant sediment origin suggested a long lateral transportation of some fine-grained Chinese river sediments (probably the Changjiang River) to the South Sea of Korea across the shelf of the northern East China Sea.

Time- and sediment depth-related variations in bacterial diversity and community structure in subtidal sands.

PubMed

Böer, Simone I; Hedtkamp, Stefanie I C; van Beusekom, Justus E E; Fuhrman, Jed A; Boetius, Antje; Ramette, Alban

2009-07-01

Bacterial community structure and microbial activity were determined together with a large number of contextual environmental parameters over 2 years in subtidal sands of the German Wadden Sea in order to identify the main factors shaping microbial community structure and activity in this habitat. Seasonal changes in temperature were directly reflected in bacterial activities and total community respiration, but could not explain variations in the community structure. Strong sediment depth-related patterns were observed for bacterial abundances, carbon production rates and extracellular enzymatic activities. Bacterial community structure also showed a clear vertical variation with higher operational taxonomic unit (OTU) numbers at 10-15 cm depth than in the top 10 cm, probably because of the decreasing disturbance by hydrodynamic forces with sediment depth. The depth-related variations in bacterial community structure could be attributed to vertical changes in bacterial abundances, chlorophyll a and NO(3)(-), indicating that spatial patterns of microbes are partially environmentally controlled. Time was the most important single factor affecting microbial community structure with an OTU replacement of up to 47% over 2 years and a contribution of 34% to the total variation. A large part of this variation was not related to any environmental parameters, suggesting that temporal variations in bacterial community structure are caused by yet unknown environmental drivers and/or by stochastic events in coastal sand habitats. Principal ecosystem functions such as benthic oxygen consumption and extracellular hydrolysis of organic matter were, however, at a high level at all times, indicating functional redundancy in the microbial communities.

Polychlorinated biphenyls in two salt marsh sediments of the Venice Lagoon.

PubMed

Mugnai, Cristian; Giuliani, Silvia; Bellucci, Luca G; Carraro, Claudio; Favotto, Maurizio; Frignani, Mauro

2011-10-01

Polychlorinated biphenyls (PCBs) were measured in two dated salt marsh cores of the Venice Lagoon to assess their input chronology and to evaluate the importance of atmospheric deposition as a source. Sampling sites were chosen in order to evidence the differences between areas located leeward and windward with respect to inputs originating in both the city of Venice and the industrial area. Concentrations of PCB indicators (0.13-15.6 ng g⁻¹) increased gradually from the 1930s, reached maxima from the 1950s to the late 1970s, and then decreased. PCB loadings to marshes are driven by both the atmospheric deposition and the resuspension of subtidal sediments, this latter being more important for heavier congeners. The downwind marsh recorded higher fluxes (0.06-9.72 ng cm⁻² year⁻¹) than the upwind one (0.01-0.53 ng cm⁻² year⁻¹). Recent fluxes are rather consistent with bulk deposition measurements. A higher contribution of CB-101 and CB-118 was detected in the intermediate layers of the downwind site, suggesting a different PCB source for the corresponding time interval. In the other marsh, PCBs showed a rather constant composition at all levels (mostly CB-153, CB-138 and CB-180), accounting for a regional influence. Deep layers showed an enrichment of higher chlorinated congeners at both sites, whereas recent samples conserve the patterns typical of surficial and subsurficial subtidal sediments. The scientific approach adopted in this research can be considered as a sort of methodological procedure for the determination of fluxes and pathways of PCBs through the study of marsh cores.

Sediment drifts and contourites on the continental margin off northwest Britain

NASA Astrophysics Data System (ADS)

Stoker, M. S.; Akhurst, M. C.; Howe, J. A.; Stow, D. A. V.

1998-01-01

Seismic reflection profiles and short cores from the continental margin off northwest Britain have revealed a variety of sediment-drift styles and contourite deposits preserved in the northeast Rockall Trough and Faeroe-Shetland Channel. The sediment drifts include: (1) distinctly mounded elongate drifts, both single- and multi-crested; (2) broad sheeted drift forms, varying from gently domed to flat-lying; and (3) isolated patch drifts, including moat-related drifts. Fields of sediment waves are locally developed in association with the elongate and gently domed, broad sheeted drifts. The contrasting styles of the sediment drifts most probably reflect the interaction between a variable bottom-current regime and the complex bathymetry of the continental margin. The bulk of the mounded/gently domed drifts occur in the northeast Rockall Trough, whereas the flat-lying, sheet-form deposits occur in the Faeroe-Shetland Channel, a much narrower basin which appears to have been an area more of sediment export than drift accumulation. Patch drifts are present in both basins. In the northeast Rockall Trough, the along-strike variation from single- to multi-crested elongate drifts may be a response to bottom-current changes influenced by developing drift topography. Muddy, silty muddy and sandy contourites have been recovered in sediment cores from the uppermost parts of the drift sequences. On the basis of their glaciomarine origin, these mid- to high-latitude contourites can be referred to, collectively, as glacigenic contourites. Both partial and complete contourite sequences are preserved; the former consist largely of sandy (mid-only) and top-only contourites. Sandy contourites, by their coarse-grained nature and their formation under strongest bottom-current flows, are the most likely to be preserved in the rock record. However, the very large scale of sediment drifts should be borne in mind with regard to the recognition of fossil contourites in ancient successions.

Side-Scan Sonar Imagery of The Recent Seabed and Sediment Properties on The Inner Shelf Off The Lagoons of Küçükçekmece and Büyükçekmece

NASA Astrophysics Data System (ADS)

Alp, H.; Vardar, D.; Alpar, B.

2017-12-01

The sea-bottom sediment distribution, benthic habitats and erosional pathways between Küçükçekmece and Büyükçekmece lagoons at the northern margin of the Marmara Sea were mapped via 340-680 kHz dual frequency side scan sonar, one of the most effective tools for underwater exploration. In fact these lagoons were two former estuaries, later separated from the sea by coarse grained sediments mainly made up of natural sand bars and man-made barriers constructed for roads about a century ago. In the summer 2016, a total of 250-km long side scan data were acquired, with a 300 m of swath width. The coastal strip between the present coastline and the -10 m depth, the seafloor sediments are made up of coarse-grained sandy deposits and determined as continuous bright reflections on the sonograms. Silty and muddy sand units are distributed between the water depths of -10 to -20 m, and they give continuous less bright reflections on sonograms if compared to those of shallow sandy deposits. Deeper muddy units (sandy silt) appeared on the sonograms as uniform dark reflections and soft scatterings. The areal distribution of seafloor sediments and their acoustical characteristics indicated that the net sediment transport in the study area is mainly controlled under the E-W directional longshore currents and dominant southerly waves. Some strong sonar reflections observed at shallow depths (0-15 m) in the Küçükçekmece lagoon and characteristically comprised of remarkable round-shape structures, represent reefs which need sunlight and stable hydrographic conditions to be formed. Various sand ripples are defined in the lagoon, as well.

Hurricane Sandy washover deposits on Fire Island, New York

USGS Publications Warehouse

La Selle, SeanPaul M.; Lunghino, Brent D.; Jaffe, Bruce E.; Gelfenbaum, Guy; Costa, Pedro J.M.

2017-02-16

Washover deposits on Fire Island, New York, from Hurricane Sandy in 2012 were investigated a year after the storm to document the sedimentary characteristics of hurricane washover features. Sediment data collected in the field includes stratigraphic descriptions and photos from trenches, bulk sediment samples, U-channels, and gouge and push cores. Samples and push cores were further analyzed in the laboratory for grain size, density variations using x-ray computed tomography (CT), and surface microtexture using a scanning electron microscope (SEM). Elevation profiles of washover features were measured using Differential Global Positioning System (DGPS) with Real Time Kinematic processing. The DGPS elevations were compared to lidar (light detection and ranging) data from pre- and post-Sandy surveys to assess the degree to which washover deposit thicknesses changed within the year following deposition. Hurricane Sandy washover deposits as much as 1 meter thick were observed in trenches. Initial results show that the upper parts of the deposits have been reworked significantly in some places by wind, but there are still areas where the deposits are almost entirely intact. Where mostly intact, the washover deposits consist of massive or weakly laminated sand near the base, overlain by more strongly laminated sands.

Physical criteria for distinguishing sandy tsunami and storm deposits using modern examples

USGS Publications Warehouse

Morton, Robert A.; Gelfenbaum, Guy; Jaffe, Bruce E.

2007-01-01

Modern subaerial sand beds deposited by major tsunamis and hurricanes were compared at trench, transect, and sub-regional spatial scales to evaluate which attributes are most useful for distinguishing the two types of deposits. Physical criteria that may be diagnostic include: sediment composition, textures and grading, types and organization of stratification, thickness, geometry, and landscape conformity. Published reports of Pacific Ocean tsunami impacts and our field observations suggest that sandy tsunami deposits are generally 30 cm thick, generally extend The distinctions between tsunami and storm deposits are related to differences in the hydrodynamics and sediment-sorting processes during transport. Tsunami deposition results from a few high-velocity, long-period waves that entrain sediment from the shoreface, beach, and landward erosion zone. Tsunamis can have flow depths greater than 10 m, transport sediment primarily in suspension, and distribute the load over a broad region where sediment falls out of suspension when flow decelerates. In contrast, storm inundation generally is gradual and prolonged, consisting of many waves that erode beaches and dunes with no significant overland return flow until after the main flooding. Storm flow depths are commonly

Petrophysical Properties Of Sandy Sediments Possibly Hosting Gas Hydrate In The Eastern Margin Of Japan Sea

NASA Astrophysics Data System (ADS)

Uchida, T.; Takashima, I.; Sunaga, H.; Sasaki, S.; Matsumoto, R.

2011-12-01

In 2010 the MD179 project was undertaken by the Marion Dufresne aiming at recovery of deep seated gas and gas hydrate, methane induced carbonate, and deep sediments older than 300 ka in order to develop geologic model of gas hydrate accumulation and evaluate the possible environmental impact of gas hydrate for the last glacial-interglacial cycles. Sediment samples below the seafloor were obtained in the Umitaka Spur, Joetsu Channel, Toyama Trough, Japan Basin, Nishi Tsugaru and Okushiri Ridge areas by the MD179 cruise. Small amounts of sandy sediment have been retrieved as thin intercalations in Pleistocene and Holocene silty layers, where trace fossils and strong bioturbations are commonly observed. Those sandy sediments consist of very fine- to fine-grained sand grains, and are sometimes tuffaceous. Pore-size distribution measurements and thin-section observations of these arenite sands were undertaken, which indicatesd that porosities of muddy sediments are around 50 % but those of arenites range from 42 to 52 %, of which mean pore sizes and permeabilities are larger than those of siltstones and mudstones. These coarser sediments might have been transported approximately around 3 to 30 ka, where supplying sediments may not be abundant due to sea level fluctuation during the Pleistocene ice age. While the presence of gas hydrate in intergranular pores of arenite sands has not been confirmed, the soupy occurrence in recovered sediments may strongly indicate the presence of gas hydrate filling the intergranular pore system of arenite sands that is called pore-space hydrates. They have been recognized till now in the Mallik as well as in the Nankai Trough areas, which are considered to be very common even in the subsurface sandy sediments at the eastern margin of Japan Sea. Concentration of gas hydrate may need primary intergranular pores large enough to occur within a host sediment that may be arenite sand without matrix grains deposited in the sedimentary environment such as deep sea channels. The geological modeling of the gas hydrate formation and evolution system is concerned for energy resource potential in the Japan Sea as well as the Nankai Trough areas. Time of deposition of coarse-grained sediments can be recognized by the thermoluminescence (TL) dating method. TL dating works on the principle that materials containing naturally occurring radioactive isotopes such as uranium, thorium or potassium are subject to low levels of radiation. In mineral crystals, this leads to ionization of the atoms in the host material and freed electrons may become trapped in structural defects or holes in the mineral crystal lattice. These electrons can be released by heating under controlled conditions, and an emission of light occurs which is the basis of TL dating. Additionally they usually provide information about the provenance and the paleoenvironment when the sediments deposited. This study was performed as a part of the MH21 Research Consortium on methane hydrate in Japan.

Behavior and Fate of PFOA and PFOS in Sandy Aquifer Sediment (journal)

EPA Science Inventory

Microcosms were constructed with sediment from beneath a landfill that received waste containing PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonate). The microcosms were amended with PFOA and PFOS, and sampled after 91, 210, 343, 463, 574, and 740 days of incubat...

Sound Speed and Attenuation in Multiphase Media

DTIC Science & Technology

2012-03-15

wave speeds between 100 to 300 m/s for sandy sediments with porosities of 40-50%. Hastrup [21:121-127] reports empirical relationships that 12...4, pp. 689-692, 1955. [20] R.D. Stoll, Sediment Acoustics, Springer-Verlag, New York, 1989. [21] O. F. Hastrup , Acoustic Bottom Reflectivity

Peritidal cyclic sedimentation from La Manga Formation (Oxfordian), Neuquén Basin, Mendoza, Argentina

NASA Astrophysics Data System (ADS)

Palma, Ricardo M.; Kietzmann, Diego A.; Bressan, Graciela S.; Martín-Chivelet, Javier; López-Gómez, José; Farias, María E.; Iglesias Llanos, María P.

2013-11-01

The La Manga Formation consists of marine carbonates and represents most of the sedimentary record of the Callovian-Oxfordian in the Neuquén Basin. Three localities in the southern Mendoza province were studied and their cyclicity was determined by means of facies analysis and their vertical arrangement. Facies of inner ramp, that were deposited in extremely shallow-water environments with intermittent subaerial exposures have been broken down into shallow subtidal, and intertidal-supratidal environments. Shallow subtidal facies are arranged into decimetre scale upward-shallowing cycles composed of marls, laminated or massive mudstones or bioclastic wackestones and intraclastic wackestone-packstones. Intertidal-supratidal centimetre-scale cycles consist of an upward-shallowing succession of restricted facies, overlaid by horizontal or crinkle microbial laminites, flat pebble conglomerates or breccias beds. The defined cycles show a shallowing upward trend in which the evidence of relative sea-level lowering is accepted. The interpretation of Fischer plots allowed the recognition of changes in accommodation space.

Folly Beach, South Carolina. Survey Report on Beach Erosion Control and Hurricane Protection. Appendixes.

DTIC Science & Technology

1979-08-01

horseshoe crabs, sand dollars and numerous clams and gastropod mollusks i,, the beach subtidal areas. In addition, several species of fish are conyionly...bacteria and protozoa. Most benthic animals such as crustaceans, bivalve and gastropod mollusks, and burrowing and tube-dwelling polychaete worms are...due to the continual ut :ftil tidal fJ a. . , ted sediment shifting. Inlet inhabitants onsist nos ,y 1 1.., itipods, and polychaetes which are adapted

Bedform development and morphodynamics in mixed cohesive sediment substrates: the importance of winnowing and flocculation

NASA Astrophysics Data System (ADS)

Ye, Leiping; Parsons, Daniel; Manning, Andrew

2016-04-01

There remains a lack of process-based knowledge of sediment dynamics within flows over bedforms generated in complex mixtures of cohesionless sand and biologically-active cohesive muds in natural estuarine flow systems. The work to be presented forms a part of the UK NERC "COHesive BEDforms (COHBED)" project which aims to fill this gap in knowledge. Herein results from a field survey in sub-tidal zone of Dee estuary (NW, England) and a set of large-scale laboratory experiments, conducted using mixtures of non-cohesive sands, cohesive muds and Xanthan gum (as a proxy for the biological stickiness of Extracellular Polymeric Substances (EPS)) will be presented. The results indicate the significance of biological-active cohesive sediments in controlling winnowing rates and flocculation dynamics, which contributes significantly to rates of bedform evolution.

The Laurentian Fan: Sohm Abyssal Plain

USGS Publications Warehouse

Piper, D.J.W.; Stow, D.A.V.; Normark, W.R.

1984-01-01

The 0.5- to 2-km thick Quaternary Laurentian Fan is built over Tertiary and Mesozoic sediments that rest on oceanic crust. Two 400-km long fan valleys, with asymmetric levees up to 700-m high, lead to an equally long, sandy, lobate basin plain (northern Sohm Abyssal Plain). The muddy distal Sohm Abyssal Plain is a further 400-km long. The sediment supplied to the fan is glacial in origin, and in part results from seismically triggered slumping on the upper continental slope. Sandy turbidity currents, such as the 1929 Grand Banks earthquake event, probably erode the fan-valley floors; but thick muddy turbidity currents build up the high levees. ?? 1984 Springer-Verlag New York Inc.

A method to assess the evolution and recovery of heavy metal pollution in estuarine sediments: Past history, present situation and future perspectives.

PubMed

Bárcena, Javier F; Claramunt, Inigo; García-Alba, Javier; Pérez, María Luisa; García, Andrés

2017-11-15

A methodology to assess the historical evolution and recovery of heavy metal pollution in estuarine sediments was developed and is presented here. This approach quantifies the distribution of heavy metals in sediment cores, and investigates the influence of anthropogenic activities and/or core locations on the heavy metal pollution, by proposing and using sediment quality indices and polynomial regressions. The method has been applied to the Suances Estuary confirming its suitability as a comprehensive and practical management tool. In this estuary, the evolution of heavy metal pollution (since 1997-1998 to 2015) pointed out the deeper the sediments, the more polluted, indicating a recovery at the upper layers due to the closure and ending of washing discharges from mining, and the reduction of metal loads from industrial wastewaters. In terms of global pollution, the intertidal and subtidal sediments will require 43.1±2.8 and 8.6±0.6years to be unpolluted, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

Tropical Cyclone-Driven Sediment Dynamics Over the Australian North West Shelf

NASA Astrophysics Data System (ADS)

Dufois, François; Lowe, Ryan J.; Branson, Paul; Fearns, Peter

2017-12-01

Owing to their strong forcing at the air-sea interface, tropical cyclones are a major driver of hydrodynamics and sediment dynamics of continental shelves, strongly impacting marine habitats and offshore industries. Despite the North West Shelf of Australia being one of the most frequently impacted tropical cyclone regions worldwide, there is limited knowledge of how tropical cyclones influence the sediment dynamics of this shelf region, including the significance of these episodic extreme events to the normal background conditions that occur. Using an extensive 2 year data set of the in situ sediment dynamics and 14 yearlong calibrated satellite ocean-color data set, we demonstrate that alongshore propagating cyclones are responsible for simultaneously generating both strong wave-induced sediment resuspension events and significant southwestward subtidal currents. Over the 2 year study period, two particular cyclones (Iggy and Narelle) dominated the sediment fluxes resulting in a residual southwestward sediment transport over the southern part of the shelf. By analyzing results from a long-term (37 year) wind and wave hindcast, our results suggest that at least 16 tropical cyclones had a strong potential to contribute to that southwestward sediment pathway in a similar way to Iggy and Narelle.

Wrack patches and their influence on upper-shore macrofaunal abundance in an Atlantic Canada sandy beach system

NASA Astrophysics Data System (ADS)

MacMillan, Mitchell R.; Quijón, Pedro A.

2012-08-01

Patches of stranded macrophytes (wrack) are a distinctive feature of sandy beaches worldwide and a potential food subsidy for their resident communities. Despite their relevance, the spatial variation of wrack and its potential influence on upper shore beach organisms remain poorly understood. Wrack and macrofauna were surveyed on seven sandy beaches associated with dunes, till bluffs and sandstone cliffs along the north shore of Prince Edward Island, Atlantic Canada. Wrack patch density, cover, and water content were measured, and their associated macrofauna was compared to the communities inhabiting nearby bare sediments. The survey found among-site spatial differences in wrack characteristics and identified rockweeds (Fucus serratus) and eelgrass (Zostera marina) as the main macrophyte species in the area. Macrofaunal abundances were higher in wrack than in bare sediments but this varied among locations. A field manipulation was then conducted at two sandy beaches to measure macrofauna colonization on patches of fresh and aged rockweed and eelgrass. Regardless of macrophyte's age, macrofaunal organisms preferentially colonized sediments associated with rockweeds. In addition, calculations across treatments detected positive relationships between macrofaunal abundance and wet mass, dry mass and water content of the wrack patches, regardless of macrophyte species or state. Macrophyte preferences were further explored by comparing the nutritional value of the plant tissues and assessing macrofauna feeding rates under laboratory conditions. Rockweed tissues had consistently higher protein, lipid and carbohydrate contents than eelgrass and were affected by higher invertebrate consumption rates. Overall, these results suggest that spatial variation and wrack features and species composition play key roles on the structure of the supralittoral macrofauna.

Detection of Animal Viruses in Coastal Seawater and Sediments

PubMed Central

De Flora, Silvio; De Renzi, Giuseppe P.; Badolati, Giuseppe

1975-01-01

Animal viruses, predominantly enteroviruses, were detected in shallow waters at bottom depths and in clastic marine sediments. Viruses accumulated in sandy and slimy deposits of the sea bottom near the shore and could be easily released into water by means of simple mechanical shaking. Images PMID:170859

Controlling factors of recent clastic coastal sediments (Viransehir, Mersin bay, S Turkey)

NASA Astrophysics Data System (ADS)

Gül, Murat; Özbek, Ahmet; Kurt, Mehmet Ali; Zorlu, Kemal

2009-04-01

The Plio-Quaternary conglomeratic sets within the marine environment of the Viranşehir coast (W Mersin, S Turkey) are responsible for the evolution of sandy and gravely beaches due to their control on various factors such as sea floor irregularity, wave energy, and organic activity. The conglomeratic sets close to the shoreline (50-150 cm) act as wave breakers, creating hard substratum and high energy, well-oxygenated environment for organisms like Patella sp., Phoronida worms and Brachidontes pharaonis (Fischer P. 1870). The boring activities of these organisms have disintegrated the sandy matrix of these sets. Finer-grained matrix sediments have been transported to the interset and open sea, while cobble-pebbles have been carried landwards and have created imbricated gravely beach deposits without matrix. Sandy beach is evolving where the conglomeratic sets away from the shoreline (5.0-10.0 m). In this example, sets form a bar; causing fivefold division as backshore, berm, surf zone, bar and offshore from land to sea. Poorly sorted, cobbles-pebbles cobbles and pebbles are found associated with the high-energy environments of bars, whilst well-sorted sands are observed in low energetic environments on shore. The sets and recent shell fragments are the main sources of coastal sediments in Viranşehir. However, the amount of shell fragments decrease towards the active river mouth. This is due to sediment and fresh water influx from the river causing deteriorated temperature, salinity and light penetration of the marine environment resulting in less organic diversity.

Effect of salinity and inorganic nitrogen concentrations on nitrification and denitrification rates in intertidal sediments and rocky biofilms of the Douro River estuary, Portugal.

PubMed

Magalhães, Catarina M; Joye, Samantha B; Moreira, Rosa M; Wiebe, William J; Bordalo, Adriano A

2005-05-01

The regulatory effects of salinity and inorganic nitrogen compounds on nitrification and denitrification were studied in intertidal sandy sediments and rocky biofilms in the Douro River estuary, Portugal, over a 12-month period. Nitrification and denitrification rates were measured in slurries of field samples and enrichment experiments using the difluoromethane and the acetylene inhibition techniques, respectively. Salinity did not regulate denitrification in either environment, suggesting that halotolerant bacteria dominated the denitrifier communities. However, nitrification rates were stimulated when salinity increased from 0 to 15 practical salinity units. NO3- addition experiments revealed that NO3- availability stimulates denitrification rates in sandy sediments, but not in rocky biofilms; however, in rocky biofilms a positive and linear relationship was observed between denitrification rates and water column NO3- concentrations (r=0.92) during the monthly surveys. The N2O:N2 ratios increased rapidly when NO3- increased from 63 to 363 microM; however, results from monthly surveys showed that environmental parameters other than NO3- availability may be important in controlling the variation in N2O production via denitrification. Ammonium additions to sandy sediments stimulated nitrification rates by 35% for the 20 microM NH4+ addition, but NH4+ appeared to inhibit nitrification at high concentration addition (200 microM NH4+). In contrast, rocky biofilm nitrification was stimulated by 65% when 200 microM NH4+ was added.

Microbial community structure of sandy intertidal sediments in the North Sea, Sylt-Rømø Basin, Wadden Sea.

PubMed

Musat, Niculina; Werner, Ursula; Knittel, Katrin; Kolb, Steffen; Dodenhof, Tanja; van Beusekom, Justus E E; de Beer, Dirk; Dubilier, Nicole; Amann, Rudolf

2006-06-01

Molecular biological methods were used to investigate the microbial diversity and community structure in intertidal sandy sediments near the island of Sylt (Wadden Sea) at a site which was characterized for transport and mineralization rates in a parallel study (D. de Beer, F. Wenzhöfer, T. Ferdelman, S.E. Boehme, M. Huettel, J.E.E. van Beusekom, M.E. Böttcher, N. Musat, N. Dubilier, Transport and mineralization rates in North Sea sandy intertidal sediments, Sylt-Romo Basin, Wadden Sea, Limnol. Oceanogr. 50 (2005) 113-127). Comparative 16S rRNA sequence analysis revealed a high bacterial diversity. Most sequences retrieved by PCR with a general bacterial primer set were affiliated with Bacteroidetes, Gammaproteobacteria, Deltaproteobacteria and the Pirellula cluster of Planctomycetales. Fluorescence in situ hybridization (FISH) and slot-blot hybridization with group-specific rRNA-targeted oligonucleotide probes were used to characterize the microbial community structure over depth (0-12 cm) and seasons (March, July, October). We found high abundances of bacteria with total cell numbers up to 3 x 10(9) cells ml(-1) and a clear seasonal variation, with higher values in July and October versus March. The microbial community was dominated by members of the Planctomycetes, the Cytophaga/Flavobacterium group, Gammaproteobacteria, and bacteria of the Desulfosarcina/Desulfococcus group. The high abundance (1.5 x 10(7)-1.8 x 10(8) cells ml(-1) accounting for 3-19% of all cells) of presumably aerobic heterotrophic polymer-degrading planctomycetes is in line with the high permeability, deep oxygen penetration, and the high rates of aerobic mineralization of algal biomass measured in the sandy sediments by de Beer et al. (2005). The high and stable abundance of members of the Desulfosarcina/Desulfococcus group, both over depth and season, suggests that these bacteria may play a more important role than previously assumed based on low sulfate reduction rates in parallel cores (de Beer et al., 2005).

Modern Foraminifera from a depth transect offshore Brunei Darussalam: diversity, sedimentation rate and preservation pathways.

NASA Astrophysics Data System (ADS)

Briguglio, Antonino; Goeting, Sulia; Kusli, Rosnani; Roslim, Amajida; Polgar, Gianluca; Kocsis, Laszlo

2016-04-01

For this study, 11 samples have been collected by scuba diving from 5 to 35 meters water depth off shore Brunei Darussalam. The locations sampled are known as: Pelong Rock (5 samples, shallow reef with soft and stony corals and larger foraminifera, 5 to 8 meters water depth), Abana Rock (1 sample, shallow reef with mainly soft corals and larger foraminifera, 13 to 18 meters water depth), Oil Rig wreck (1 sample, very sandy bottom with larger foraminifera, 18 meters water depth), Dolphin wreck (1 sample, muddy sand with many small rotaliids, 24 meters water depth), US wreck, (1 sample, sand with small clay fraction, 28 meters water depth), Australian wreck (1 sample, mainly medium to coarse sand with larger foraminifera, 34 meters water depth) and Blue water wreck (1 sample, mainly coarse sand, coral rubble and larger foraminifera, 35 meters water depth). Those samples closer to the river inputs are normally richer in clay, while the most distant samples are purely sandy. Some additional samples have been collected next to reef environments which, even if very shallow, are mainly sandy with almost no clay fraction. The deepest sample, which is 30 km offshore, contains some planktonic foraminifera and is characterized by a large range of preservations concerning foraminifera, thus testifying the presence or relict sediments at the sea bottom. The presence of relict sediments was already pointed out by older oil-related field studies offshore Brunei Darussalam, and now it is possible to draw the depth limit of these deposits. The diversity of the benthic foraminiferal fauna is relatively high but not as higher as neighboring regions as some studies have highlighted. The species collected and identified are more than 50: in reef environment the most abundant are Calcarina defrancii, Neorotalia calcar and the amphisteginidae; deeper in the muddy sediments the most abundant is Pararotalia schroeteriana and in the deepest sandy sample the most abundant are Calcarina hispida, followed by Operculina ammonoides.

The role of sediment compaction and groundwater withdrawal in local sea-level rise, Sandy Hook, New Jersey, USA

NASA Astrophysics Data System (ADS)

Johnson, Christopher S.; Miller, Kenneth G.; Browning, James V.; Kopp, Robert E.; Khan, Nicole S.; Fan, Ying; Stanford, Scott D.; Horton, Benjamin P.

2018-02-01

The rate of relative sea-level (RSL) rise at Sandy Hook, NJ (4.0 ± 0.5 mm/yr) was higher than The Battery, NY (3.0 ± 0.3 mm/yr) from 1900 to 2012 despite being separated by just 26 km. The difference cannot be explained by differential glacial isostatic adjustment (GIA; 1.4 ± 0.4 and 1.3 ± 0.4 mm/yr RSL rise, respectively) alone. We estimate the contribution of sediment compaction to subsidence at Sandy Hook using high-resolution grain size, percent organic matter, and porosity data from three upper Quaternary (≤13,350 cal yr) cores. The organic matter content (<2%) is too low to contribute to local subsidence. However, numerical modeling of the grain size-depth-age-porosity relationship indicates that compaction of deglacial silts likely reduced the column thickness by 10-20% over the past 13,350 cal yrs. While compaction rates were high immediately after the main silt deposition (13,350-13,150 cal yrs BP), rates decreased exponentially after deposition to an average 20th century rate of 0.16 mm/yr (90% Confidence Interval (C.I.), 0.06-0.32 mm/yr). The remaining ∼0.7 mm/yr (90% C.I. 0.3-1.2 mm/yr) difference in subsidence between Sandy Hook and The Battery is likely due to anthropogenic groundwater withdrawal. Historical data from Fort Hancock wells (2 km to the southeast of the Sandy Hook tide gauge) and previous regional work show that local and regional water extraction lowered the water levels in the aquifers underlying Sandy Hook. We suggest that the modern order of contribution to subsidence (highest to lowest) appears to be GIA, local/regional groundwater extraction, and compaction of thick Quaternary silts.

Evaluating process origins of sand-dominated fluvial stratigraphy

NASA Astrophysics Data System (ADS)

Chamberlin, E.; Hajek, E. A.

2015-12-01

Sand-dominated fluvial stratigraphy is often interpreted as indicating times of relatively slow subsidence because of the assumption that fine sediment (silt and clay) is reworked or bypassed during periods of low accommodation. However, sand-dominated successions may instead represent proximal, coarse-grained reaches of paleo-river basins and/or fluvial systems with a sandy sediment supply. Differentiating between these cases is critical for accurately interpreting mass-extraction profiles, basin-subsidence rates, and paleo-river avulsion and migration behavior from ancient fluvial deposits. We explore the degree to which sand-rich accumulations reflect supply-driven progradation or accommodation-limited reworking, by re-evaluating the Castlegate Sandstone (Utah, USA) and the upper Williams Fork Formation (Colorado, USA) - two Upper Cretaceous sandy fluvial deposits previously interpreted as having formed during periods of relatively low accommodation. Both units comprise amalgamated channel and bar deposits with minor intra-channel and overbank mudstones. To constrain relative reworking, we quantify the preservation of bar deposits in each unit using detailed facies and channel-deposit mapping, and compare bar-deposit preservation to expected preservation statistics generated with object-based models spanning a range of boundary conditions. To estimate the grain-size distribution of paleo-sediment input, we leverage results of experimental work that shows both bed-material deposits and accumulations on the downstream side of bars ("interbar fines") sample suspended and wash loads of active flows. We measure grain-size distributions of bar deposits and interbar fines to reconstruct the relative sandiness of paleo-sediment supplies for both systems. By using these novel approaches to test whether sand-rich fluvial deposits reflect river systems with accommodation-limited reworking and/or particularly sand-rich sediment loads, we can gain insight into large-scale downstream-fining and mass-extraction trends in basins with limited exposure.

Photoacclimatory Responses of Zostera marina in the Intertidal and Subtidal Zones.

PubMed

Park, Sang Rul; Kim, Sangil; Kim, Young Kyun; Kang, Chang-Keun; Lee, Kun-Seop

2016-01-01

Photoacclimatory responses of the seagrass Zostera marina in the intertidal and subtidal zones were investigated by measuring chlorophyll a fluorescence parameters, photosynthetic pigments, leaf δ13C values, and shoot morphology in two bay systems. Intertidal plants had higher carotenoid concentrations than subtidal plants to avoid photodamage under excess light conditions during the day. The maximum relative electron transport rate (rETRmax) and minimum saturation irradiance (Ek) of the intertidal plants were higher than those of the subtidal plants, whereas photosynthetic efficiency (α) and maximum quantum yield (Fv/Fm) were higher in subtidal plants. The intertidal plants also had significantly greater Stern-Volmer non-photochemical quenching (NPQ) than that of the subtidal plants. These results suggest that the subtidal plants photoacclimated to use limited light more efficiently, and the intertidal plants exhibited photosynthetic responses to minimize photodamage at excess irradiance. The δ13C values of leaf tissues were more negative in the intertidal plants than those in the subtidal plants, suggesting that the intertidal plants used atmospheric or dissolved CO2 for photosynthesis during emersion. Effective quantum yield (ΔF/Fm´) in the intertidal plants decreased more slowly after emersion than that in the subtidal plants, indicating higher desiccation tolerance of the intertidal plants. The intertidal plants also recovered more rapidly from desiccation damage than the subtidal plants, suggesting photosynthetic adaptation to desiccation stress. The photosynthetic plasticity of Z. marina in response to variable environmental conditions most likely allows this species to occur in the intertidal and subtidal zones.

Cyclostratigraphy across a Mississippian carbonate ramp in the Esfahan-Sirjan Basin, Iran: implications for the amplitudes and frequencies of sea-level fluctuations along the southern margin of the Paleotethys

NASA Astrophysics Data System (ADS)

Bayet-Goll, Aram; Esfahani, Fariba Shirezadeh; Daraei, Mehdi; Monaco, Paolo; Sharafi, Mahmoud; Mohammadi, Amir Akbari

2018-03-01

The Tournaisian-Visean carbonate successions of the Esfahan-Sirjan Basin (ESB) from Sanandaj-Sirjan Zone, Iran, have been used to generate a sequence stratigraphic model that enhances facies characterization and improves paleoenvironmental interpretation of shallow marine successions deposited along the southern margin of the Paleotethys. Detailed facies analysis allowed to differentiate seven facies, which, in order of decreasing abundance, are: (1) shaly and marly, F1; (2) peloidal mudstones/wackestones, F2; (3) peloidal/bioclastic packstones, F3; (4) intraclastic/bioclastic packstones/grainstones, F4; (5) oolitic/bioclastic packstone/grainstone, F5; (6) sandy intraclastic/bioclastic grainstones, F6; (7) sandy oolitic/bioclastic grainstones, F7. The different facies can be grouped into three facies associations that correspond to different environments of a carbonate platform with ramp geometry (homoclinal), from outer ramp (F1 and F2), mid-ramp (F3, F4 and F6) to inner ramp areas (F5 and F7). Meter-scale cycles are the basic building blocks of shallow marine carbonate successions of the Tournaisian-Viséan ramp of the ESB. Small-scale cycles are stacked into medium-scale cycles that in turn are building blocks of large-scale cycles. According to the recognized facies and the stacking pattern of high-frequency cycles across the ramp, five large-scale cycles in the southeastern outcrops (Tournaisian-Viséan) and three large-scale cycles in the northwest outcrops (Viséan) related to eustatic sea-level changes can be recognized. The overall retrogradational nature of the carbonate ramp, illustrated by both vertical facies relationships and the stacking patterns of high-frequency cycles within the third-order cycles, implies that the deposition of the Tournaisian-Viséan successions mainly took place under a long-term transgressive sea-level trend. The stratigraphic architectural style of the sequences, characterized by the lack of lowstand deposits and exposure surfaces, associated with the evidence of progressive increase in the proportion of backstepping of facies belts across bounding surfaces and predominant subtidal characteristics, is in accordance with the long-term transgressive sea-level trend and greenhouse conditions during the Tournaisian-Viséan. The continued transgression on this broad shelfal platform could lead to the shutdown of the shallow water carbonate factory, reduction in sediment supply or sediment transport towards the offshore setting and the development of give-up sequences. The association of transgressive events with the deposition of thick open-marine marls/shales is a common feature in Tournaisian to Viséan times of the southern margin of the Paleotethys.

Key parameters of the sediment surface morphodynamics in an estuary - An assessment of model solutions

NASA Astrophysics Data System (ADS)

Sampath, D. M. R.; Boski, T.

2018-05-01

Large-scale geomorphological evolution of an estuarine system was simulated by means of a hybrid estuarine sedimentation model (HESM) applied to the Guadiana Estuary, in Southwest Iberia. The model simulates the decadal-scale morphodynamics of the system under environmental forcing, using a set of analytical solutions to simplified equations of tidal wave propagation in shallow waters, constrained by empirical knowledge of estuarine sedimentary dynamics and topography. The key controlling parameters of the model are bed friction (f), current velocity power of the erosion rate function (N), and sea-level rise rate. An assessment of sensitivity of the simulated sediment surface elevation (SSE) change to these controlling parameters was performed. The model predicted the spatial differentiation of accretion and erosion, the latter especially marked in the mudflats within mean sea level and low tide level and accretion was mainly in a subtidal channel. The average SSE change mutually depended on both the friction coefficient and power of the current velocity. Analysis of the average annual SSE change suggests that the state of intertidal and subtidal compartments of the estuarine system vary differently according to the dominant processes (erosion and accretion). As the Guadiana estuarine system shows dominant erosional behaviour in the context of sea-level rise and sediment supply reduction after the closure of the Alqueva Dam, the most plausible sets of parameter values for the Guadiana Estuary are N = 1.8 and f = 0.8f0, or N = 2 and f = f0, where f0 is the empirically estimated value. For these sets of parameter values, the relative errors in SSE change did not exceed ±20% in 73% of simulation cells in the studied area. Such a limit of accuracy can be acceptable for an idealized modelling of coastal evolution in response to uncertain sea-level rise scenarios in the context of reduced sediment supply due to flow regulation. Therefore, the idealized but cost-effective HESM model will be suitable for estimating the morphological impacts of sea-level rise on estuarine systems on a decadal timescale.

Impact of pore-water freshening on clays and the compressibility of hydrate-bearing reservoirs during production

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

Jang, Junbong; Cao, Shuang; Waite, William

Gas production efficiency from natural hydrate-bearing sediments depends in part on geotechnical properties of fine-grained materials, which are ubiquitous even in sandy hydrate-bearing sediments. The responses of fine-grained material to pore fluid chemistry changes due to freshening during hydrate dissociation could alter critical sediment characteristics during gas production activities. We investigate the electrical sensitivity of fine grains to pore fluid freshening and the implications of freshening on sediment compression and recompression parameters.

Nursery function of coastal temperate benthic habitats: New insight from the bivalve recruitment perspective

NASA Astrophysics Data System (ADS)

Barbier, Pierrick; Meziane, Tarik; Forêt, Martin; Tremblay, Réjean; Robert, René; Olivier, Frédéric

2017-03-01

Marine habitat function has been typically investigated in terms of biogeochemical regulation but rarely in terms of population renewal, which is mainly controlled by recruitment dynamics. The recruitment phase is crucial for organisms with a bentho-pelagic life cycle, such as bivalves, and it regulates the population renewal success. This study provides new insight on the role of temperate benthic habitats on bivalve recruitment, as a function of nursery areas. Six dominant benthic habitats of the Chausey archipelago (Normandy, France) were studied. In each habitat, bivalve recruit assemblages were described at the end of two reproductive seasons. Furthermore, Ostrea edulis juveniles were immerged on each habitat during two months to compare growth performances and feeding status, estimated by fatty acid composition. Recruit assemblages differ from each habitat according to sediment grain-size composition and bathymetrical levels. Subtidal habitats, and especially Crepidula fornicata banks and Glycymeris glycymeris coarse sands, supported the highest species abundance and richness of recruits. All O. edulis juveniles fed on the same trophic resources but digestive glands of juveniles from C. fornicata banks were more concentrated in total fatty acids than those from subtidal G. glycymeris coarse sands and maerl banks. Our results depict the key role of subtidal and structured habitats, composed of ecosystem engineers, in enhancing bivalve recruitment and extending the bivalve population renewal. This study suggests that the crucial role of these habitats as bivalve nurseries must be integrated in management perspectives. 2-column fitting image. 1-column fitting image.

Effect of alternative surface inlet designs on sediment and phosphorus drainage losses

USDA-ARS?s Scientific Manuscript database

Open surface inlets that connect to subsurface tile drainage systems provide a direct pathway for sediment, nutrients, and agrochemicals to surface waters. This study was conducted to determine whether modifying open inlets by burying them in gravel capped with 30 cm of sandy clay loam soil or in ve...

Fate and effects of picric acid and 2,6-DNT in marine environments: toxicity of degradation products.

PubMed

Nipper, Marion; Carr, R Scott; Biedenbach, James M; Hooten, Russell L; Miller, Karen

2005-11-01

The toxicity of transformation products of 2,6-dinitrotoluene (2,6-DNT) and 2,4,6-trinitrophenol (picric acid) were assessed in spiked sandy and fine-grained marine sediments and in seawater. Toxicity of pore water from sediments spiked with 2,6-DNT decreased for the macro-alga, Ulva fasciata, zoospores as biotransformation proceeded, but increased for the copepod, Schizopera knabeni, nauplii. The primary biotransformation product of 2,6-DNT, 2-amino-6-nitrotoluene, was also more toxic than the parent compound to copepod nauplii, but not to alga zoospores, in spiked seawater tests. Two biotransformation products of picric acid, picramic acid and 2,4-DNP, were more toxic than their parent compound. Porewater toxicity from picric acid-spiked sediments decreased significantly at the end of six-months incubation. Fine-grained sediment spiked with either ordnance compound had lower toxicity than its sandy counterpart after six months, suggesting faster microbial transformation in the former and production of less toxic products. Photo-transformation of 2,6-DNT in seawater resulted in a reduction in toxicity.

Discontinuity surfaces in the Lower Cretaceous of the high Andes (Mendoza, Argentina): Trace fossils and environmental implications

NASA Astrophysics Data System (ADS)

Mangano, M. G.; Buatois, L. A.

The paleoecologic and paleoenvironmental significance of trace fossils related to discontinuity surfaces in the Lower Cretaceous marine deposits of the Aconcagua area are analysed here. Carbonate-evaporite shoaling-upward cycles, developed by high organic production in a shallow hypersaline restricted environment, make up the section. Two types of cycles are defined, being mainly distinguished by their subtidal unit. Cycle I begins with a highly dolomitized lower subtidal unit (Facies A), followed upward by an intensely bioturbated upper subtidal unit (Facies B). The nodular packstone facies (B 1) is capped by a discontinuity surface (firmground or hardground) and occasionally overlain by an oystreid bed (Facies C). Cycle II is characterized by a pelletoidal subtidal unit (Facies B 2) with an abnormal salinity impoverished fauna. Both cycles end with intertidal to supratidal evaporite deposits (Facies D and E, respectively). Attention is particularly focused on cycle I due to its ichologic content. The mode of preservation and the distribution of trace fossils in nodular packstone facies are controlled by original substrate consolidation. Thalassinoides paradoxicus (pre-omission suite) represents colonization in a soft bottom, while Thalassinoides suevicus (omission suite pre-lithification) is apparently restricted to firm substrates. When consolidation processes are interrupted early, only an embryonic hard-ground that represents a minor halt in sedimentation was developed. Sometimes, consolidation processes continued leading to an intraformational hardground. Colonization by Trypanites solitarius (omission suite post-lithification) and Exogyra-like oystreids possibly characterizes hard substrate stage. When two discontinuity surfaces follow closely, a post-omission suite may be defined in relation to the lower cemented surface. As trace fossils are so closely related to changes in the degree of bottom lithification, they prove to be very useful as indicators of substrate evolution. The presence of discontinuity surfaces, evidenced by trace fossil association, suggests changes of sedimentary rate and environmental conditions that should be taken into account in future studies seeking to erect depositional models for these Cretaceous deposits.

Geomorphology of the Chippewa River delta of Glacial Lake Saginaw, central Lower Michigan, USA

NASA Astrophysics Data System (ADS)

Connallon, Christopher B.; Schaetzl, Randall J.

2017-08-01

We introduce, characterize, and interpret the geomorphic history of a relict, Pleistocene-aged delta of the Chippewa River in central Lower Michigan. The broad, sandy Chippewa delta developed into various stages of Glacial Lake Saginaw, between ca. ≈ 17 and 15 ka·BP (calibrated ages). Although the delta was first identified in 1955 on a statewide glacial geology map, neither its extent nor its Pleistocene history had been previously determined. The delta is typically forested, owing to its wet, sandy soils, which stand out against the agricultural fields of the surrounding, loamy lake plain sediments. The delta heads near the city of Mt Pleasant and extends eastward onto the Saginaw Lowlands, i.e., the plain of Glacial Lake Saginaw. Data from 3285 water well logs, 180 hand augered sites, and 185 points randomly located in a GIS on two-storied (sand over loam) soils were used to determine the extent, textural properties, and thickness of the delta. The delta is ≈ 18 km wide and ≈ 38 km long and is sandy throughout. Deltaic sediments from neighboring rivers that also drained into Glacial Lake Saginaw merge with the lower Chippewa delta, obscuring its boundary there. The delta is thickest near the delta's head and in the center, but thins to 1-2 m or less on its eastern margins. Mean thicknesses are 2.3-2.9 m, suggestive of a thin sediment body, frequently impacted by the waves and fluctuating waters of the lakes. Although beach ridges are only weakly expressed across the delta because of the sandy sediment, the coarsest parts of the delta are generally coincident with some of these inferred former shorezones and have a broad, incised channel that formed while lake levels were low. The thick upper delta generally lies above the relict shorelines of Glacial Lakes Saginaw and Arkona (≈ 17.1 to ≈ 16 ka·BP), whereas most of the thin, distal delta is associated with Glacial Lake Warren (≈ 15 ka·BP). Together, these data suggest that the Chippewa delta formed and prograded as lake levels in the Saginaw Lowlands alternated and episodically fell. The result is a delta that is comparatively thin, expansive, and sandy. In some places, these sands have subsequently been reworked into fields of small parabolic dunes.

Tidal flat sedimentation during the last millennium in the northern area of Tidra Island, Banc d’Arguin, Mauritania

NASA Astrophysics Data System (ADS)

Proske, Ulrike; Hanebuth, Till J. J.; Meggers, Helge; Leroy, Suzanne A. G.

2008-01-01

The area around the Tidra Island is a complex and highly dynamic clastic tidal flat system. The character of the northern part of this area is outlined, together with its sedimentary changes through time and the different depositional environments that shaped this coastal area in the last centuries are reconstructed. The multi-proxy approach together with 14C-dating has led to the identification of four main types of deposits using the modern facies distribution as an analogue: A ˜800-440 cal yr BP old sandy shoreface, different types of tidal flats (sand to mudflat) that discontinuously developed on top of this older shoreface deposit, seagrass stands in the most recent part of the sedimentary succession and at least two storm deposits of various ages within the record. The interpretation of the cores' highly non-continuous succession allows the postulation of a constructive sandy shoreface that covered large parts of the area. The in most cases erosive boundary between this older deposit and the overlying tidal flat deposits indicates that a short-lived event eroded parts of this sandy shoreface deposit. According to the latest studies, recent sea-level fluctuations can be excluded so it is suggested that a major storm event eroded parts of the sandy shoreface to about 2-2.5 m below the modern mean low water. This erosive storm event possibly produced accommodation space in the water column for the renewed accumulation of sediments so that tidal flat sediments could evolve on top of the sandy shoreface deposits. At least one other storm event led to further reshaping of the area and finally the modern tidal flats and seagrass stands in the proximity of Tidra Island formed. As shown in current research [e.g. Barusseau, J.P., Vernet, R., Saliège, J.F., Descamps, C., 2007. Late Holocene sedimentary forcing and human settlements in the Jerf el Oustani - Ras el Sass region (Banc d'Arguin, Mauritania). Geomorphologie-Relief Processus Environnement 1, 7-18], these observations are in contrast to the overall constructive coastline evolution the Golfe d'Arguin. This is probably linked to the exceptional position of the Tidra Island area that represents a morphological protrusion in the coastline and is thus also exposed to erosive processes rather than sediment accumulation.

Modeling of sediment transport in a saltwater lake with supplemental sandy freshwater.

PubMed

Liang, Li; Deng, Yun; Li, Ran; Li, Jia

2018-06-22

Considering the highly complex flow structure of saltwater lakes during freshwater supplementation, a three-dimensional numerical model was developed to simulate suspended sediment transport in saltwater lakes. The model was validated using measurements of the salinity and sediment concentration during a pumping test at Yamdrok Lake. The simulation results were in quantitative agreement with the measured data. The observed and simulated results also indicated that the wind stress and vertical salinity gradient have a significant influence on salinity and sediment transport in a saltwater lake. The validated model was then used to predict and analyze the contributions of wind, the supplement flow rate and salinity stratification to the sediment transport process in Yamdrok Lake during continuous river water supplementation. The simulation results showed that after the sandy river water was continuously discharged into the saltwater lake, the lateral diffusion trends of the sediment exhibited three stages: linear growth in the inflow direction, logarithmic growth in the wind direction, and stabilization. Furthermore, wind was the dominant factor in driving the lake flow pattern and sediment transport. Specifically, wind can effectively reduce the area of the sediment diffusion zone by increasing the lateral sediment carrying and dilution capacities. The effect of inflow on the lake current is negligible, but the extent of the sediment turbidity zone mainly depends on the inflow. Reducing the inflow discharge can decrease the area of the sediment turbidity zone to proportions that far exceed the proportions of inflow discharge reductions. In addition, the high-salinity lake water can support the supplemented freshwater via buoyancy forces, which weaken vertical mixing and sediment settlement and increase lake currents and sediment diffusion near the surface.

The impact of a high magnitude flood on metal pollution in a shallow subtropical estuarine embayment.

PubMed

Coates-Marnane, J; Olley, J; Burton, J; Grinham, A

2016-11-01

Drought-breaking floods pose a risk to coastal water quality as sediments, nutrients, and pollutants stored within catchments during periods of low flow are mobilized and delivered to coastal waters within a short period of time. Here we use subtidal surface sediment surveys and sediment cores to explore the effects of the 2011 Brisbane River flood on trace metals zinc (Zn), lead (Pb), copper (Cu), nickel (Ni), chromium (Cr), manganese (Mn), and phosphorus (P) deposition in Moreton Bay, a shallow subtropical bay in eastern Australia. Concentrations of Zn, Cu, and Pb in sediments in central Moreton Bay derived from the 2011 flood were the highest yet observed in the Bay. We suggest flushing of metal rich sediments which had accumulated on the Brisbane River floodplain and in its estuary during the preceding 10 to 40years of low flows to be the primary source of this increase. This highlights the importance of intermittent high magnitude floods in tidally influenced rivers in controlling metal transport to coastal waters in subtropical regions. Copyright © 2016. Published by Elsevier B.V.

Grounding of the Bahia Paraiso at Arthur Harbor, Antarctica. 1. Distribution and fate of oil spill related hydrocarbons

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

Kennicutt, M.C. II; Sweet, S.T.; Fraser, W.R.

1991-03-01

In January to March 1989 water, organisms, and sediments within a 2-mile radius of Arthur Harbor were contaminated with an estimated 600,000 L of petroleum spilled by the Bahia Paraiso. All components of the ecosystem were contaminated to varying degrees during the spill, including birds, limpets, macroalgae, clams, bottom-feeding fish, and sediments. The high-energy environment, the relatively small volume of material released, and the volatility of the released product all contributed to limiting toxic effects in time and space. The most effective removal processes were evaporation, dilution, winds, and currents. Sedimentation, biological uptake, microbial oxidation, and photooxidation accounted for removalmore » of only a minor portion of the spill. One year after the spill several areas still exhibited contamination. Subtidal sediments and the more distant intertidal locations were devoid of detectable PAH contaminants whereas sediments near the docking facility at Palmer Station continued to reflect localized nonspill-related activities in the area. Arthur Harbor and adjacent areas continue to be chronically exposed to low-level petroleum contamination emanating from the Bahia Paraiso.« less

Photoacclimatory Responses of Zostera marina in the Intertidal and Subtidal Zones

PubMed Central

Park, Sang Rul; Kim, Sangil; Kim, Young Kyun; Kang, Chang-Keun; Lee, Kun-Seop

2016-01-01

Photoacclimatory responses of the seagrass Zostera marina in the intertidal and subtidal zones were investigated by measuring chlorophyll a fluorescence parameters, photosynthetic pigments, leaf δ13C values, and shoot morphology in two bay systems. Intertidal plants had higher carotenoid concentrations than subtidal plants to avoid photodamage under excess light conditions during the day. The maximum relative electron transport rate (rETRmax) and minimum saturation irradiance (Ek) of the intertidal plants were higher than those of the subtidal plants, whereas photosynthetic efficiency (α) and maximum quantum yield (Fv/Fm) were higher in subtidal plants. The intertidal plants also had significantly greater Stern–Volmer non-photochemical quenching (NPQ) than that of the subtidal plants. These results suggest that the subtidal plants photoacclimated to use limited light more efficiently, and the intertidal plants exhibited photosynthetic responses to minimize photodamage at excess irradiance. The δ13C values of leaf tissues were more negative in the intertidal plants than those in the subtidal plants, suggesting that the intertidal plants used atmospheric or dissolved CO2 for photosynthesis during emersion. Effective quantum yield (ΔF/Fm´) in the intertidal plants decreased more slowly after emersion than that in the subtidal plants, indicating higher desiccation tolerance of the intertidal plants. The intertidal plants also recovered more rapidly from desiccation damage than the subtidal plants, suggesting photosynthetic adaptation to desiccation stress. The photosynthetic plasticity of Z. marina in response to variable environmental conditions most likely allows this species to occur in the intertidal and subtidal zones. PMID:27227327

Seafloor Mapping and Benthic Habitats off Assateague Island National Seashore: can we Resolve any Effects of Superstorm Sandy?

NASA Astrophysics Data System (ADS)

Miller, D.; Trembanis, A. C.; Kennedy, E.; Rusch, H.; Rothermel, E.

2016-02-01

The National Park Service has partnered with faculty and students at the University of Delaware to map the length of Assateague Island and sample benthic communities there for two purposes: (1) to provide a complete inventory of benthic habitats and their biota, and (2) to determine if any changes from a pre-storm survey can be ascribed to Superstorm Sandy in 2012. During the 2014 and 2015 field seasons over 75 km2 of high-resolution ( 50 cm/pixel) side-scan sonar and collocated bathymetry were collected with a surface vessel mounted bathy side-scan sonar (EdgeTech 6205), spanning the shore from depths of less than 2 m out to a distance of approximately 1 nautical mile and depths of 10-12 m. Furthermore, we have resampled using standard methodology (modified Young grab and 0.5-mm sieve) a subset of the previously sampled benthic stations that represent all sediment classes identified in prior studies. Additionally, we have obtained novel data with our ROV and AUV assets, including finer scale bottom video and multibeam bathymetry, at specifically chosen locations in order to enhance understanding of the benthic habitat and bottom type changes. In addition to providing a habitat and faunal inventory for resource management purposes, we will compare our side scan and benthic survey data to the pre-storm 2011 data products with comparable coverage. To date we have found that ArcGIS and ENVI sediment classifications agree well with those from the 2011 study, but spatially we note more areas of finer sediments and less of gravel. As was expected, 2014 benthic assemblages differ significantly among sediment classes (PRIMER ANOSIM), and sediment class is the best predictor of the benthic community (PERMANOVA+ distance-based RDA). Our goal here is to use consistent analytical approaches to characterize changes that occur over season and inter-annual time scales. This is a critical step toward attributing sediment, habitat and biological changes to Superstorm Sandy.

Methylmercury production and export from a restored tidal marsh: Crissy Field, Golden Gate National Recreation Area, San Francisco, CA

NASA Astrophysics Data System (ADS)

Windham-Myers, L.; Ward, K.; Marvin-Dipasquale, M. C.; Agee, J.; Kieu, L.; Kakouros, E.

2009-12-01

Well-mixed surface water in the restored salt marsh at Crissy Field, Golden Gate National Recreation Area, was found to have high aqueous methylmercury (MeHg) concentrations (>1 ng MeHg / L), despite its sandy substrate and low sediment total mercury (THg) concentrations. We sought to determine a) the extent to which the marsh was a source or a sink of MeHg to San Francisco Bay, b) where and when MeHg is produced within the marsh, and c) the extent to which MeHg concentrations in sediment and water varied with extended multi-week flooding events, impoundments caused by periodic sediment accumulation in the narrow inlet. Because Crissy Marsh is small in size, has a single inlet slough channel, and has a tidally-dominated water budget, we had a unique opportunity to construct a THg and MeHg flux budget for this single well-constrained wetland. A 24-hour sampling event was conducted over a full diurnal tidal cycle during August 2008. Particulate and filter-passing (0.45μm) THg and MeHg concentrations were assessed, in addition to concentrations of chlorophyll-a and total suspended solids. These measurements were coupled to water flux calculations from a USGS-derived hydrodynamic model based on tidal prism relationships at this site. The resulting Hg load calculations demonstrated that for this 24-hour period, the marsh was a net source of dissolved MeHg to the bay and a net sink of particulate THg from the bay. To determine where and when Hg was being methylated within the marsh environment, sediment percent (%) MeHg (a surrogate measure of MeHg production efficiency) was examined for 2 years along 8 transects, seasonally and across three marsh elevations (subtidal, low-intertidal, and high-intertidal). The low-intertidal zone (cordgrass-dominated) had higher sediment %MeHg than the other two elevations. Sediment %MeHg was also higher during summer than during winter, highest at the sediment surface (0-2cm), correlated with sediment organic content, and elevated during closure events at some intertidal sites, suggesting enhanced MeHg production during impoundment. However, aqueous MeHg concentrations (both filtered and unfiltered) fell during inlet closure events. Additional data suggest that increased algal production and decreased suspended solids (increased water clarity) may remove MeHg from the water column during closure events, either through settling of mineral and algal components or via photodemethylation. We conclude that MeHg production is most active in the low intertidal sediments of Crissy Marsh, and that this spatial trend is driven by both wetting/drying cycles and the comparatively elevated organic matter concentrations in this zone. We further conclude that the mercury present in Crissy Marsh, whether due to historic contamination, atmospheric deposition or tidal loads, is subject to methylation and export as MeHg. At only 18 acres, Hg fluxes between Crissy Marsh and the larger Bay may be small, but the flux dynamics demonstrated here may be representative of semi-enclosed salt marshes elsewhere in San Francisco Bay.

A new species of the ghost shrimp genus Lepidophthalmus (Crustacea: Decapoda: Axiidea) from the southwestern Gulf of Mexico.

PubMed

Felder, Darryl L

2015-07-13

A new species of Lepidophthalmus lacking a ventral median sclerite on the second abdominal somite is described from coastal waters of the southwestern Gulf of Mexico. Lepidophthalmus statoni sp. nov., originally recognized only as a unique population in allozyme studies, is sympatric with the ventrally plated species Lepidophthalmus manningi Felder & Staton, 2000, but more closely resembles Lepidophthalmus louisianensis (Schmitt, 1935) from the northern and northwestern Gulf of Mexico. Apparently restricted to intertidal and shallow subtidal tropical waters, the new species is known to range from western Campeche to middle-upper reaches of Veracruz, Mexico. As many members of the genus, it commonly inhabits euryhaline inlets, estuaries, and protected shorelines, including richly organic muddy to clayey sands and sandy muds adjacent to shoreline vegetation. Coloration is documented and discussed as a tool to facilitate field identifications, as are morphological characters.

Applications of ichnology to hydrogeology, with examples from the Cape Fear Formation (Cretaceous), South Carolina

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

Martin, A.J.; Simones, G.C.

Ichnology, the study of modern and ancient traces left by organisms, has provided supplemental information to geologic subdisciplines such as sedimentology and stratigraphy. The major objective of the authors paper is to emphasize the valuable information that can be conveyed by trace fossils in the investigation of hydrogeologic units. Bioturbation has a net effect of mixing different types and layers of sediments, such as introducing clays into sands and vice versa. This mixing can decrease porosity and permeability of sandy units, thus changing potential aquifers into confining units. For example, a sandy fluvial deposit will contain distinctive nonmarine trace fossils,more » thus defining channel sands that may serve as permeable conduits for ground-water flow. In contrast, a sandy shelf deposit will contain marine trace fossils in a sand body geometry that will be markedly different from aquifers produced in nonmarine environments. Bioturbation also causes geochemical and diagenetic changes in sediments, causing irrigation of previously anoxic sediments and precipitation of ion oxides. The Cretaceous Cape Fear Formation of the Atlantic Coastal Plain, in the subsurface of South Carolina, is presented as an example of a hydrogeologic unit that has been reinterpreted using ichnologic data. Extensive bioturbation caused mixing of clays and sands in Cape Fear sediments, which resulted in the Cape Fear becoming a regional confining system. Trace fossil assemblages indicate a brackish water environment, perhaps estuarine, for the Cape Fear, as opposed to previous interpretations of fluvial and deltaic environments. Bioturbated zones also have significantly more oxidized iron than unbioturbated zones, highlighting potential effects on ground-water quality.« less

Plant-mediated Sediment Oxygenation in Coastal Wetlands

NASA Astrophysics Data System (ADS)

Koop-Jakobsen, K.

2016-02-01

Belowground sediment oxygenation by wetland plants is an important mechanism controlling many microbial processes and chemical fluxes in coastal wetlands. Although transport of oxygen via the arenthyma tissue and subsequent oxygen loss across root surfaces is well-documented for Spartina grasses, only few studies have measured the oxygenation of sediment surrounding roots and rhizomes. In this study, the degree of sediment oxygenation in Spartina anglica rhizospheres was assessed in situ using a novel multifiber optode system inserting 100 oxygen sensing fiber optodes directly into the rhizosphere. Two closely located, but morphologically different, S. anglica populations growing in permeable sandy sediment and tidal flat deposit, respectively, were investigated. No oxygen was detected inside the rhizospheres at any depth in either location indicating that plant-mediated sediment oxygenation in S. anglica had a limited impact on the bulk anoxic sediment. This was substantiated by planar optode studies showing that sediment oxygenation was confined to the immediate vicinity of the root tips of adventitious root and root hairs stretching only up to 1.5mm away from the roots surface in permeable sandy sediment and 0.4mm in tidal flat deposit, which had a substantially higher oxygen demand. This contrasts previous studies estimating that more than half of the S. anglica rhizosphere volume may be oxygenated, and thereby suggests a high variability in the degree of sediment oxygenation among different S. anglica populations. Furthermore, there may be a significant difference in the degree of sediment oxygenation among different Spartina species; our recent in situ investigation of oxygen profiles in a Spartina alterniflora-dominated marsh suggested that oxygen leakage here may keep the bulk sediment at low oxygen concentration ranging from 0.5-4μM.

Variations of Morphologic Changes induced by Tropical Storm Debby along Three Barrier Island, West-Central Florida, USA

NASA Astrophysics Data System (ADS)

Wang, P.; Roberts, T.

2012-12-01

Tropical Storm Debby generated sustained high waves and elevated water levels for nearly three days from June 24th to 26th, 2012, inducing substantial changes in beach and nearshore morphology. In addition, the storm winds and high waves approached the coast from a highly oblique angle from the south, driving substantial northward longshore sand transport, opposite to the regional net annual southward transport. A total of 145 beach and nearshore profiles along 3 adjacent barrier islands were surveyed 2 weeks before and one week after the storm impact. Overall, dune, beach, intertidal, and immediate subtidal areas suffered erosion, while deposition was measured over the nearshore bar. Beach recovery in the form of ridge and runnel development occurred as the storm energy subsided. Substantial longshore variations of storm-induced beach changes were measured, including both severe dune/beach/berm erosion and storm berm accretion, and both onshore and offshore migration of nearshore bar. Factors controlling these longshore variations include: 1) the oblique approaching of the storm forcing, 2) pre-storm beach morphology and chronic erosional or accretional trends, 3) sediment supply, and 4) tidal inlet and beach interactions. Wide spreading dune scarping occurred along the 30-km studied coast. Based on the pre- and post-storm survey data, a balanced sediment budget is obtained accounting for sand volume loss from dune, beach, intertidal, and subtidal zones, and sand gains over the nearshore bar and along the northern sections of the beach.

Facies analysis of Lofer cycles (Upper Triassic), in the Argolis Peninsula (Greece)

NASA Astrophysics Data System (ADS)

Pomoni-Papaioannou, F.

The Upper Triassic carbonate sediments of Argolis Peninsula are part of the Upper Triassic-Lower Jurassic extensive and thick neritic carbonate formations (Pantokrator facies) that formed at the passive Pelagonian margin and are considered as Dachstein-type platform carbonates. Facies analysis of the Upper Triassic "Lofer-type" lagoonal-peritidal cycles in the Dhidimi area, proved that cycles, although mostly incomplete, were regressive shallowing-upward. The ideal elementary cyclothems are meter-scale in thickness and begin with a subtidal bed (Member C), represented by a peloidal dolostone with megalodonts (wackestone or packstone), being followed by a stromatolitic intertidal dolomitic mudstone and/or fenestral intertidal dolomitic mudstone (Member B) that is overlain by dolocrete (terrestrial stromatolites or pisoidic dolomite) or a supratidal "soil conglomerate" in red micritic matrix (Member A). Lofer-cycle boundaries are defined at the erosional surfaces and accordingly the Lofer cyclothems are unconformity-bounded units. Due to common post-depositional truncation of the subtidal and intertidal facies, the supratidal members prevail, being developed, in places, directly upon subaerial exposure surfaces (erosionally reduced cyclothems). Peritidal layers are characterized by a well-expressed lamination, sheet cracks, tepee structures, fenestral pores and karst dissolution cavities. The studied lagoonal-peritidal cycles are considered to have been deposited in a tidal-flat setting (inner platform), repeatedly exposed under subaerial conditions, in the context of a broader tropical rimmed platform. Although the studied area was tectonically active due to rift-activity and the autocyclic processes should also be taken in consideration, the great lateral correlatability of cycles, the facies shifting and the widespread erosion that resulted in superposition of supratidal-pedogenic facies directly upon subtidal members (subaerial erosional unconformity), indicating a sea-level drop, reflect allocyclic control via high-frequency eustatic sea-level oscillation (orbital forcing). Sediment deposition occurred during low-stand system tract (LST), that probably continued also in the transgressive system tract (TST) and reflects an overall sea-level fall. Under these conditions dissolution and cement precipitation episodes, as well development of paleosols and karsts, were triggered, during a relatively less arid interval.

Water level changes affect carbon turnover and microbial community composition in lake sediments

Treesearch

Lukas Weise; Andreas Ulrich; Matilde Moreano; Arthur Gessler; Zachary E. Kayler; Kristin Steger; Bernd Zeller; Kristin Rudolph; Jelena Knezevic-Jaric

2016-01-01

Due to climate change, many lakes in Europe will be subject to higher variability of hydrological characteristics in their littoral zones. These different hydrological regimes might affect the use of allochthonous and autochthonous carbon sources. We used sandy sediment microcosms to examine the effects of different hydrological regimes (wet, desiccating, and wet-...

Effect of replacing surface inlets with blind or gravel inlets on sediment and phosphorus subsurface drainage losses

USDA-ARS?s Scientific Manuscript database

Open surface inlets that connect to subsurface tile drainage systems provide a direct pathway for sediment, nutrients, and agrochemicals to surface waters. This study was conducted to determine whether modifying open inlets by burying them in gravel capped with 30 cm of sandy clay loam soil or in ve...

Macroalgal blooms alter community structure and primary productivity in marine ecosystems.

PubMed

Lyons, Devin A; Arvanitidis, Christos; Blight, Andrew J; Chatzinikolaou, Eva; Guy-Haim, Tamar; Kotta, Jonne; Orav-Kotta, Helen; Queirós, Ana M; Rilov, Gil; Somerfield, Paul J; Crowe, Tasman P

2014-09-01

Eutrophication, coupled with loss of herbivory due to habitat degradation and overharvesting, has increased the frequency and severity of macroalgal blooms worldwide. Macroalgal blooms interfere with human activities in coastal areas, and sometimes necessitate costly algal removal programmes. They also have many detrimental effects on marine and estuarine ecosystems, including induction of hypoxia, release of toxic hydrogen sulphide into the sediments and atmosphere, and the loss of ecologically and economically important species. However, macroalgal blooms can also increase habitat complexity, provide organisms with food and shelter, and reduce other problems associated with eutrophication. These contrasting effects make their overall ecological impacts unclear. We conducted a systematic review and meta-analysis to estimate the overall effects of macroalgal blooms on several key measures of ecosystem structure and functioning in marine ecosystems. We also evaluated some of the ecological and methodological factors that might explain the highly variable effects observed in different studies. Averaged across all studies, macroalgal blooms had negative effects on the abundance and species richness of marine organisms, but blooms by different algal taxa had different consequences, ranging from strong negative to strong positive effects. Blooms' effects on species richness also depended on the habitat where they occurred, with the strongest negative effects seen in sandy or muddy subtidal habitats and in the rocky intertidal. Invertebrate communities also appeared to be particularly sensitive to blooms, suffering reductions in their abundance, species richness, and diversity. The total net primary productivity, gross primary productivity, and respiration of benthic ecosystems were higher during macroalgal blooms, but blooms had negative effects on the productivity and respiration of other organisms. These results suggest that, in addition to their direct social and economic costs, macroalgal blooms have ecological effects that may alter their capacity to deliver important ecosystem services. © 2014 John Wiley & Sons Ltd.

Laboratory investigations on the role of sediment surface and ground water chemistry in transport of bacteria through a contaminated Sandy Aquifer

USGS Publications Warehouse

Scholl, M.A.; Harvey, R.W.

1992-01-01

The effects of pH and sediment surface characteristics on sorption of indigenous groundwater bacteria were determined using contaminated and uncontaminated aquifer material from Cape Cod, MA. Over the pH range of the aquifer (5-7), the extent of bacterial sorption onto sediment in uncontaminated groundwater was strongly pH-dependent, but relatively pH-insensitive in contaminated groundwater from the site. Bacterial sorption was also affected by the presence of oxyhydroxide coatings (iron, aluminum, and manganese). Surface coating effects were most pronounced in uncontaminated groundwater (pH 6.4 at 10??C). Desorption of attached bacteria (up to 14% of the total number of labeled cells added) occurred in both field and laboratory experiments upon adjustment of groundwater to pH 8. The dependence of bacterial sorption upon environmental conditions suggests that bacterial immobilization could change substantially over relatively short distances in contaminated, sandy aquifers and that effects caused by changes in groundwater geochemistry can be significant.

Biodegradation of petroleum hydrocarbons in estuarine sediments: metal influence.

PubMed

Almeida, Raquel; Mucha, Ana P; Teixeira, Catarina; Bordalo, Adriano A; Almeida, C Marisa R

2013-02-01

In this work, the potential effect of metals, such as Cd, Cu and Pb, on the biodegradation of petroleum hydrocarbons in estuarine sediments was investigated under laboratory conditions. Sandy and muddy non-vegetated sediments were collected in the Lima River estuary (NW Portugal) and spiked with crude oil and each of the metals. Spiked sediments were left in the dark under constant shaking for 15 days, after which crude oil biodegradation was evaluated. To estimate microbial abundance, total cell counts were obtained by DAPI staining and microbial community structure was characterized by ARISA. Culturable hydrocarbon degraders were determined using a modified most probable number protocol. Total petroleum hydrocarbons concentrations were analysed by Fourier Transform Infrared Spectroscopy after their extraction by sonication, and metal contents were determined by atomic absorption spectrometry. The results obtained showed that microbial communities had the potential to degrade petroleum hydrocarbons, with a maximum of 32 % degradation obtained for sandy sediments. Both crude oil and metals changed the microbial community structure, being the higher effect observed for Cu. Also, among the studied metals, only Cu displayed measurable deleterious effect on the hydrocarbons degradation process, as shown by a decrease in the hydrocarbon degrading microorganisms abundance and in the hydrocarbon degradation rates. Both degradation potential and metal influence varied with sediment characteristics probably due to differences in contaminant bioavailability, a feature that should be taken into account in developing bioremediation strategies for co-contaminated estuarine sites.

Surface Sediment Geochemistry in and around the Hudson Shelf Valley Offshore of New York

NASA Astrophysics Data System (ADS)

Mecray, E. L.; ten Brink, M. B.; Butman, B.; Denny, J.; Murray, R. W.

2001-05-01

The Hudson Shelf Valley, an ancient submerged portion of the Hudson River, extends across the continental shelf offshore of New York and New Jersey. Between 1959 and 1987, the area near the head of the valley was used for disposal of approximately 1.20 x 108 m3 of dredged material and sewage sludge. The distribution of metal concentrations and sediment characteristics were used to investigate the transport and fate of the sediments and their associated contaminants. Surface (0-2cm) sediments collected at 440 stations throughout the New York Bight between 1993 and 1998 were used to establish the regional distribution of pollutant metals, grain size, organic carbon, and Clostridium perfringens spores. Sediments in the New York Bight are generally sandy, however fine-grained sediments are found in the axis of the Valley. Statistical methods identified common sources and chemical mobility within groups of anthropogenic and naturally-occurring elements. High metal concentrations, fine-grained sediments, and higher organic carbon concentrations co-occur in depo-centers within the Valley. Normalization of the metal concentrations to these factors shows higher metal concentrations on the fine-grained particles in sandy areas of the Bight, particularly along the southern shore of Long Island. These distributions have implications for evaluating the impact of the mass distribution for contaminated metals in different habitats and areas. Decreasing concentrations of pollutants with time are observed, reflecting reduced contaminant loading in the upper region of the Valley; however, concentrations are still above natural background levels.

Consequences of spring phytodetritus sedimentation on the benthic compartment along a depth gradient in the Eastern English Channel.

PubMed

Denis, Lionel; Desroy, Nicolas

2008-11-01

Phaeocystis blooms are of major importance in the Eastern English Channel, where they significantly contribute to spring organic matter input with chlorophyll concentrations commonly higher than 30 microgl(-1) in the water column. Post-bloom deposition of Phaeocystis derived mucilaginous compounds has been shown to have a major importance on benthic intertidal systems, but resulting mineralization processes and consequences on the macrobenthic compartment remain poorly documented in subtidal areas. In this frame, a study was performed along the French coast of the English Channel to quantify mineralization processes, as well as potential consequences on subtidal sediments, especially their geochemistry and associated macrofaunal communities. Seven stations were studied along a depth gradient during four cruises: before (March), during (April, May) and after (June) the spring bloom. Sediment characteristics and organic carbon content were described, as well as sediment-water fluxes of oxygen and ammonium. Macrofaunal characteristics were also analyzed. Stations were chosen as representative of the various benthic communities present in the area, which are directly linked to the granulometric characteristics of the sediments. To account for the general functioning of the water column, characterized by a coastal flow where higher concentrations of Phaeocystis are generally recorded, similar communities were sampled inshore and offshore, when possible: (i) the Abra alba community located only close to the coast, (ii) the Ophelia borealis community located inshore and offshore, and (iii) the Amphioxus lanceolatus community located inshore and offshore. Generally, low exchange rates of oxygen and ammonium were measured (respectively, in the range 50-150 micromol O2 m(-2)h(-1) and -25 to 35 micromol NH4+ m(-2)h(-1)) between the water column and the muddy-sand to coarse sand permeable sediments, as a consequence of the low organic carbon content due to the high hydrodynamic forcing. As a consequence of organic matter accumulation in surficial sediments probably resulting from Phaeocystis post-bloom deposition, an increase of sediment oxygen demand and ammonium release was clearly evidenced up to 660 micromol O2 m(-2)h(-1) and 205 micromol NH4+ m(-2)h(-1) in May, only in stations located close to the coast (<8 kms), in the A. alba community. Despite those significant biogeochemical changes in surficial sediments, no significant consequence was pointed out on macrofauna, neither in the O. borealis and A. lanceolatus communities, nor in the coastal A. alba community. Most of the temporal variations recorded might be attributed to the common spring population dynamics, but this study highlights the potential use of geochemical parameters as a forewarning signal of benthic disequilibrium.

Distribution of Technetium-99 in sub-tidal sediments of the Irish Sea

NASA Astrophysics Data System (ADS)

McCubbin, David; Leonard, Kinson S.; McDonald, Paul; Bonfield, Rachel; Boust, Dominique

2006-03-01

To date, relatively little attention has been given to the accumulation of 99Tc discharged from Sellafield in the subtidal sediments of the Irish Sea. The potential implications for secondary seafood contamination from contaminated sediment has driven the UK Food Standards Agency to commission further research into this pathway. The work reported here reviews existing data and provides new measurements of 99Tc specific activity in surface and sub-surface sediments of the Irish Sea, together with environmental Kd values. The results are used to assess the spatial and temporal evolution of 99Tc in the seabed after 8 years of enhanced Sellafield discharges (between 1994 and 2002), of the aforementioned radionuclide. The information is discussed with reference to other studies, in an attempt to infer the processes controlling 99Tc uptake and release from seabed sediments. The average environmental Kd value for 99Tc in the Irish Sea (1.9×10 3) was more than an order of magnitude greater than the presently recommended value of 10 2 [IAEA, 2004. Sediment distribution coefficients and concentration factors for biota in the marine environment. Technical Report Series No. 422, IAEA, Vienna]. Comparison with results from laboratory studies indicates that the observed distribution may represent metastable binding rather than thermodynamic equilibrium. Activities in surface sediments decreased with increasing distance from Sellafield but were also dependent upon the nature of the underlying substrate, being greater on muddy material. Preliminary measurements of grain-size distribution indicated that the observed variation in activities was probably not due to surface area effects. There is an emerging body of evidence from other studies that indicate the differences were most likely due to variations in redox regimes between the different substrates. Vertical profiles were significantly irregular, probably due to the effects of variable sediment mixing processes. Comparison of profiles, close to the Sellafield pipeline, with a core taken over 20 years earlier (pre-EARP) indicated that the increase in the cumulative Sellafield discharge and redissolution from surficial sediment were required to explain the temporal variation. Since the surveys reported here were completed, substantial progress has been made in reducing 99Tc discharges from Sellafield. Assuming that the rate and extent of 99Tc remobilisation follows a similar pattern to that previously observed for caesium ( 137Cs), then the half-time for redissolution of 99Tc bound to sedimentary material in the Irish Sea is likely to be of the order of several tens of years. It is probable that small but nevertheless measurable 99Tc contamination of local seafood will persist for several decades, due to this secondary source.

Effects of composition of labile organic matter on biogenic production of methane in the coastal sediments of the Arabian Sea.

PubMed

Gonsalves, Maria-Judith; Fernandes, Christabelle E G; Fernandes, Sheryl Oliveira; Kirchman, David L; Bharathi, P A Loka

2011-11-01

Coastal regions are potential zones for production of methane which could be governed by ecological/environmental differences or even sediment properties of a niche. In order to test the hypothesis that methanogenesis in most marine sediments could be driven more by proteins than by carbohydrates and lipid content of labile organic matter (LOM), incubation experiments were carried out with sediments from different environmental niches to measure methane production. The methane production rates were examined in relationship to the sediment biochemistry, i.e., carbohydrates, proteins, and lipids. The gas production measured by head space method ranged from 216 ng g( -1) day( -1) in the mangrove sediments to 3.1 μg g( -1) day( -1) in the shallow Arabian Sea. LOM ranged from 1.56 to 2.85 mg g( -1) in the shallow Arabian Sea, from 3.35 to 5.43 mg g( -1) in the mangrove estuary, and from 0.66 to 0.70 mg g( -1) in the sandy sediments with proteins contributing maximum to the LOM pool. Proteins influenced methane production in the clayey sediments of shallow depths of the Arabian Sea (r = 0.933, p < 0.001) and mangrove estuary (r = 0.981, p < 0.001) but in the sandy beach sediments, carbohydrates (r = 0.924, p < 0.001) governed the net methane production. The gas production was more pronounced in shallow and surface sediments and it decreased with depth apparently governed by the decrease in lability index. Thus, the lability index and protein content are important factors that determine methane production rates in these coastal ecosystems.

The role of bio-physical cohesive substrates on sediment winnowing and bedform development

NASA Astrophysics Data System (ADS)

Ye, Leiping; Parsons, Daniel; Manning, Andrew

2017-04-01

Existing sediment transport and bedform size predictions for natural open-channel flows in many environments are seriously impeded by a lack of process-based knowledge concerning the dynamics of complex bed sediment mixtures comprising cohesionless sand and biologically-active cohesive muds. A series of flume experiments (14 experimental runs) with different substrate mixtures of sand-clay-EPS (Extracellular Polymeric Substance) are combined with a detailed estuarine field survey (Dee estuary, NW England) to investigate the development of bedform morphologies and characteristics of suspended sediment over bio-physical cohesive substrates. The experimental results indicate that winnowing and sediment sorting can occur pervasively in bio-physical cohesive sediment - flow systems. Importantly however, the evolution of the bed and bedform dynamics, and hence turbulence production, is significantly reduced as bed substrate cohesivity increases. The estuarine subtidal zone survey also revealed that the bio-physical cohesion provided by both the clay and microorganism fractions in the bed plays a significant role in controlling the interactions between bed substrate and sediment suspension, deposition and bedform generation. The work will be presented here concludes by outlining the need to extend and revisit the effects of cohesivity in morphodynamic systems and the sets of parameters presently used in numerical modelling, particularly in the context of the impact of climate change on estuarine and coastal systems.

Experimental Study of Sound Waves in Sandy Sediment

DTIC Science & Technology

2003-05-01

parameter model ) and measurements (using a reflection ratio technique) includes derivations and measurements of acoustic imped- ances, effective densities...22 2.9 Model Used to Find Acoustic Impedance of Biot Medium . . . . . . . . . . . . . . 24 2.10 Free Body Diagram of...38] derived the complex reflection coefficient of plane acoustic waves from a poro-elastic sediment half-space. The boundary condition model is

Estuarine bed-sediment-quality data collected in New Jersey and New York after Hurricane Sandy, 2013

USGS Publications Warehouse

Fischer, Jeffrey M.; Phillips, Patrick J.; Reilly, Timothy J.; Focazio, Michael J.; Loftin, Keith A.; Benzel, William M.; Jones, Daniel K.; Smalling, Kelly L.; Fisher, Shawn C.; Fisher, Irene J.; Iwanowicz, Luke R.; Romanok, Kristin M.; Jenkins, Darkus E.; Bowers, Luke; Boehlke, Adam; Foreman, William T.; Deetz, Anna C.; Carper, Lisa G.; Imbrigiotta, Thomas E.; Birdwell, Justin E.

2015-01-01

Bed-sediment samples were collected from June to October 2013 from 167 estuarine sites extending from Cape May, New Jersey, to the New York Harbor and the eastern end of Long Island. Each sampling location and study region was characterized by using geographic information to identify potential contaminant sources. Characterizations included land cover, locations and types of businesses (industrial, financial, and others), spills (sewage, chemical, and others), bulk storage facilities, effluent discharges within 2 kilometers of the sampling point, and discharges within inundated and non-inundated regions near the sampling location. Samples were analyzed for particle size, total organic carbon, metals and trace elements, semivolatile organic compounds, wastewater compounds, hormones, and sediment toxicity. Samples were also screened using x-ray fluorescence, Fourier transform infrared spectroscopy, and x-ray diffraction. In addition, bioassays for endocrine disruptors and protein phosphatase 2A inhibition were conducted. The study was designed to provide the data needed to understand the extent and sources of contamination resulting from Hurricane Sandy, to compare the chemistry and toxicity of estuarine bed sediments before and after the storm, and to evaluate the usefulness of rapid screening and bioassay approaches in disaster settings.

Toxicity of sediments and pore water from Brunswick Estuary, Georgia

USGS Publications Warehouse

Winger, Parley V.; Lasier, Peter J.; Geitner, Harvey

1993-01-01

A chlor-alkali plant in Brunswick, Georgia, USA, discharged >2 kg mercury/d into a tributary of the Turtle River-Brunswick Estuary from 1966 to 1971. Mercury concentrations in sediments collected in 1989 along the tributary near the chlor-alkali plant ranged from 1 to 27 μg/g (dry weight), with the highest concentrations found in surface (0–8 cm) sediments of subtidal zones in the vicinity of the discharge site. Toxicity screening in 1990 using Microtox® bioassays on pore water extracted on site from sediments collected at six stations distributed along the tributary indicated that pore water was highly toxic near the plant discharge. Ten-day toxicity tests on pore water from subsequent sediment samples collected near the plant discharge confirmed high toxicity to Hyalella azteca, and feeding activity was significantly reduced in whole-sediment tests. In addition to mercury in the sediments, other metals (chromium, lead, and zinc) exceeded 50 μg/g, and polychlorobiphenyl (PCB) concentrations ranged from 67 to 95 μg/g. On a molar basis, acid-volatile sulfide concentrations (20–45 μmol/g) in the sediments exceeded the metal concentrations. Because acid-volatile sulfides bind with cationic metals and form metal sulfides, which are generally not bioavailable, toxicities shown by these sediments were attributed to the high concentrations of PCBs and possibly methylmercury.

Stable isotope hydrology in fractured and detritic aquifers at both sides of the South Atlantic Ocean: Mar del Plata (Argentina) and the Rawsonville and Sandspruit river catchment areas (South Africa)

NASA Astrophysics Data System (ADS)

Glok Galli, Melisa; Damons, Matthew E.; Siwawa, Sitembiso; Bocanegra, Emilia M.; Nel, Jacobus M.; Mazvimavi, Dominic; Martínez, Daniel E.

2017-01-01

The aim of this work is to characterize the isotope composition of water (2H and 18O) in order to establish the relationship between fractured and detritic aquifers in similar hydrological environments located at both sides of the Atlantic Ocean. The Mar del Plata zone, placed in the Argentine Buenos Aires province in South America, and the Rawsonville and Sandspruit river catchment areas, situated in the Western Cape province in South Africa were compared. Rainwater and groundwater samples from fractured and detritic aquifers were analyzed through laser spectroscopy. In both Argentina and South African study sites, stable isotopes data demonstrate an aquifers recharge source from rainfall. For the Mar del Plata region, two different groups of detritic aquifer's samples with distinct recharge processes can be identified due to the close relationship existing between the present hydrogeological environments, the aquifer's grain size sediments and the isotopes contents: one representing rapid infiltration in aquifer sediments of the creeks' palaeobeds and hills zones (sandy or silt sandy sediments) and the other with slow infiltration of evaporated water in plain zones with an aquitard behavior. In the last group, the evaporation process occurs previous infiltration or in the aquifer's non-saturated zone, because of the existence of very low topographic gradients and fine-grained sediments. The evaporation phenomenon is not evident in the Sandspruit river catchment site's detritic aquifer, because its sandy composition allows a faster infiltration rate than in the loess that compounds the Pampeano aquifer in the interfluves zones of the Argentinian study area.

MOBILIZATION AND CHARACTERIZATION OF COLLOIDS GENERATED FROM CEMENT LEACHATES MOVING THROUGH A SRS SANDY SEDIMENT

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

Li, D.; Roberts, K.; Kaplan, D.

Naturally occurring mobile colloids are ubiquitous and are involved in many important processes in the subsurface zone. For example, colloid generation and subsequent mobilization represent a possible mechanism for the transport of contaminants including radionuclides in the subsurface environments. For colloid-facilitated transport to be significant, three criteria must be met: (1) colloids must be generated; (2) contaminants must associate with the colloids preferentially to the immobile solid phase (aquifer); and (3) colloids must be transported through the groundwater or in subsurface environments - once these colloids start moving they become 'mobile colloids'. Although some experimental investigations of particle release inmore » natural porous media have been conducted, the detailed mechanisms of release and re-deposition of colloidal particles within natural porous media are poorly understood. Even though this vector of transport is known, the extent of its importance is not known yet. Colloid-facilitated transport of trace radionuclides has been observed in the field, thus demonstrating a possible radiological risk associated with the colloids. The objective of this study was to determine if cementitious leachate would promote the in situ mobilization of natural colloidal particles from a SRS sandy sediment. The intent was to determine whether cementitious surface or subsurface structure would create plumes that could produce conditions conducive to sediment dispersion and mobile colloid generation. Column studies were conducted and the cation chemistries of influents and effluents were analyzed by ICP-OES, while the mobilized colloids were characterized using XRD, SEM, EDX, PSD and Zeta potential. The mobilization mechanisms of colloids in a SRS sandy sediment by cement leachates were studied.« less

Linking Intertidal and Subtidal Food Webs: Consumer-Mediated Transport of Intertidal Benthic Microalgal Carbon

PubMed Central

Kang, Chang-Keun; Park, Hyun Je; Choy, Eun Jung; Choi, Kwang-Sik; Hwang, Kangseok; Kim, Jong-Bin

2015-01-01

We examined stable carbon and nitrogen isotope ratios for a large variety of consumers in intertidal and subtidal habitats, and their potential primary food sources [i.e., microphytobenthos (MPB), phytoplankton, and Phragmites australis] in a coastal bay system, Yeoja Bay of Korea, to test the hypothesis that the transfer of intertidal MPB-derived organic carbon to the subtidal food web can be mediated by motile consumers. Compared to a narrow δ13C range (−18 to −16‰) of offshore consumers, a broad δ13C range (−18 to −12‰) of both intertidal and subtidal consumers indicated that 13C-enriched sources of organic matter are an important trophic source to coastal consumers. In the intertidal areas, δ13C of most consumers overlapped with or was 13C-enriched relative to MPB. Despite the scarcity of MPB in the subtidal, highly motile consumers in subtidal habitat had nearly identical δ13C range with many intertidal foragers (including crustaceans and fish), overlapping with the range of MPB. In contrast, δ13C values of many sedentary benthic invertebrates in the subtidal areas were similar to those of offshore consumers and more 13C-depleted than motile foragers, indicating high dependence on phytoplankton-derived carbon. The isotopic mixing model calculation confirms that the majority of motile consumers and also some of subtidal sedentary ones depend on intertidal MPB for more than a half of their tissue carbon. Finally, although further quantitative estimates are needed, these results suggest that direct foraging by motile consumers on intertidal areas, and thereby biological transport of MPB-derived organic carbon to the subtidal areas, may provide important trophic connection between intertidal production and the nearshore shallow subtidal food webs. PMID:26448137

River Flow Impacts Bacterial and Archaeal Community Structure in Surface Sediments in the Northern Gulf of Mexico.

PubMed

Ortmann, Alice C; Brannock, Pamela M; Wang, Lei; Halanych, Kenneth M

2018-04-17

Meiobenthic community structure in the northern Gulf of Mexico has been shown to be driven by geographical differences due to inshore-offshore gradients and location relative to river discharge. Samples collected along three transects spanning Mobile Bay, Alabama, showed significant differences in meiobenthic communities east of the bay compared to those sampled from the west. In contrast, analysis of bacterial and archaeal communities from the same sediment samples shows that the inshore-offshore gradient has minimal impact on their community structure. Significant differences in community structure were observed for Bacteria and Archaea between the east and west samples, but there was no difference in richness or diversity. Grouped by sediment type, higher richness was observed in silty samples compared to sandy samples. Significant differences were also observed among sediment types for community structure with bacteria communities in silty samples having more anaerobic sulfate reducers compared to aerobic heterotrophs, which had higher abundances in sandy sediments. This is likely due to increased organic matter in the silty sediments from the overlying river leading to low oxygen habitats. Most archaeal sequences represented poorly characterized high-level taxa, limiting interpretation of their distributions. Overlap between groups based on transect and sediment characteristics made determining which factor is more important in structuring bacterial and archaeal communities difficult. However, both factors are driven by discharge from the Mobile River. Although inshore-offshore gradients do not affect Bacteria or Archaea to the same extent as the meiobenthic communities, all three groups are strongly affected by sediment characteristics.

Flow regulation manipulates contemporary seasonal sedimentary dynamics in the reservoir fluctuation zone of the Three Gorges Reservoir, China.

PubMed

Tang, Qiang; Bao, Yuhai; He, Xiubin; Fu, Bojie; Collins, Adrian L; Zhang, Xinbao

2016-04-01

Since the launch of the Three Gorges Dam on the Yangtze River, a distinctive reservoir fluctuation zone has been created and significantly modified by regular dam operations. Sediment redistribution within this artificial landscape differs substantially from that in natural fluvial riparian zones, due to a specific hydrological regime comprising steps of water impoundment with increasing magnitudes and seasonal water level fluctuation holding a range of sediment fluxes. This study reinterpreted post-dam sedimentary dynamics in the reservoir fluctuation zone by stratigraphy determination of a 345-cm long sediment core, and related it to impact of the hydrological regime. Seasonality in absolute grain-size composition of suspended sediment was applied as a methodological basis for stratigraphic differentiation. Sedimentary laminations with relatively higher proportions of sandy fractions were ascribed to sedimentation during the dry season when proximal subsurface bank erosion dominates source contributions, while stratigraphy with a lower proportion of sandy fractions is possibly contributed by sedimentation during the wet season when distal upstream surface erosion prevails. Chronology determination revealed non-linear and high annual sedimentation rates ranging from 21.7 to 152.1cm/yr. Although channel geomorphology may primarily determine the spatial extent of sedimentation, seasonal sedimentary dynamics was predominantly governed by the frequency, magnitude, and duration of flooding. Summer inundation by natural floods with enhanced sediment loads produced from upstream basins induced higher sedimentation rates than water impoundment during the dry season when distal sediment supply was limited. We thus conclude that flow regulation manipulates contemporary seasonal sedimentary dynamics in the reservoir fluctuation zone, though little impact on total sediment retention rate was detected. Ongoing reductions in flow and sediment supply under human disturbance may have profound implications in affecting sedimentary equilibrium in the reservoir fluctuation zone. The results herein provide insights of how big dams have disrupted the sediment conveyance processes of large scale fluvial systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Preparation of Unconsolidated Sands for Microscopy Laboratory Exercises.

ERIC Educational Resources Information Center

Cameron, Barry; Jones, J. Richard

1988-01-01

Describes a technique of impregnating small amounts of sandy sediment in a quick curing resin for microscopic examination. Details the preparation of materials. Suggests laboratory exercises based on this preparation. (CW)

Regime Shift in Sandy Beach Microbial Communities following Deepwater Horizon Oil Spill Remediation Efforts

PubMed Central

Engel, Annette Summers; Gupta, Axita A.

2014-01-01

Sandy beaches support a wide variety of underappreciated biodiversity that is critical to coastal ecosystems. Prior to the 2010 Deepwater Horizon oil spill, the diversity and function of supratidal beach sediment microbial communities along Gulf of Mexico coastlines were not well understood. As such, it was unclear if microbial community compositional changes would occur following exposure to beached oil, if indigenous communities could biodegrade oil, or how cleanup efforts, such as sand washing and sediment redistribution, would impact microbial ecosystem resiliency. Transects perpendicular to the shoreline were sampled from public beaches on Grand Isle, Louisiana, and Dauphin Island, Alabama, over one year. Prior to oil coming onshore, elevated levels of bacteria associated with fecal contamination were detected (e.g., Enterobacteriales and Campylobacterales). Over time, significant shifts within major phyla were identified (e.g., Proteobacteria, Firmicutes, Actinobacteria) and fecal indicator groups were replaced by taxa affiliated with open-ocean and marine systems (e.g., Oceanospirillales, Rhodospirillales, and Rhodobacterales). These new bacterial groups included putative hydrocarbon degraders, similar to those identified near the oil plume offshore. Shifts in the microbial community composition strongly correlated to more poorly sorted sediment and grain size distributional changes. Natural oceanographic processes could not account for the disrupted sediment, especially from the backshore well above the maximum high-tide levels recorded at these sites. Sand washing and tilling occurred on both open beaches from August through at least December 2010, which were mechanisms that could replace fecal indicator groups with open-ocean groups. Consequently, remediation efforts meant to return beaches to pre-spill compositions caused a regime shift that may have added potential ecosystem function, like hydrocarbon degradation, to the sediment. Future research will need to assess the persistence and impact of the newly formed microbial communities to the overall sandy beach ecosystems. PMID:25036744

Are we sinking Sandy Hook? Possible impacts of groundwater extraction to sea-level change

NASA Astrophysics Data System (ADS)

Johnson, C. S.; Fan, Y.; Miller, K. G.; Browning, J. V.

2017-12-01

The tide gauge at Sandy Hook, NJ, a spit of sand extending 8 km into Raritan Bay of New York and New Jersey, recorded a 20th century rate of relative sea-level (RSL) rise of 4.0±0.5 mm/yr, significantly higher than the 1.4±0.2 mm/yr rate of global mean sea-level rise for the twentieth century. The Battery, NY tide gauge, located atop crystalline bedrock 26 km to the northwest, recorded a 20th century rate of RSL rise of 3.0±0.3 mm/yr and reflects the regional rate of RSL rise. After global and regional effects are removed from the rate of RSL rise at Sandy Hook, the remaining 0.9±0.5 mm/yr is due to local effects, autocompaction and groundwater extraction induced compaction, within the unconsolidated Cretaceous to recent sediments underlying Sandy Hook. Our previous work showed that 0.13 mm/yr (90% CI 0.01-0.34 mm/yr) is due to autocompaction of young (≤13,350 cal yrs BP), highly compressible, Quaternary sediments underlying Sandy Hook. The remaining 0.8 mm/yr (90% CI 0.3-1.2 mm/yr) is hypothesized to be due to regional and local groundwater extraction. Previous studies have shown that Sandy Hook is within the cone of depression for Monmouth County, NJ. Historical records indicate that pumping for Ft. Hancock, a military installation on Sandy Hook, depleted some shallow aquifers as early as 1905. Visual MODFLOW was used to model the northern portion of the New Jersey coastal plain. Well logs from the northern New Jersey coastal plain were compiled and interpreted to refine subsurface geometries and build the model grid. Well permits provided modern locations and rates of groundwater extraction. 1,794 observation wells were used to calibrate the model. We present model results simulating the change in regional and local groundwater flow and hydraulic pressures from pre-development ( 1880) to present. The pressure changes were then used to calculate the potential changes in thickness of each of the stratigraphic units underneath Sandy Hook between 1880 and present. The resulting average rate of groundwater extraction induced compaction is between 0.2 and 4.3 mm/yr. Better constraints on stratigraphy, pumping rates, and improved model boundaries are being used to narrow this range.

The effects of wastewater effluent and river discharge on benthic heterotrophic production, organic biomass and respiration in marine coastal sediments.

PubMed

Burd, B; Macdonald, T; Bertold, S

2013-09-15

We examine effects of high river particulate flux and municipal wastewater effluent on heterotrophic organic carbon cycling in coastal subtidal sediments. Heterotrophic production was a predictable (r(2)=0.95) proportion (56%) of oxidized OC flux and strongly correlated with organic/inorganic flux. Consistent growth efficiencies (36%) occurred at all stations. Organic biomass was correlated with total, OC and buried OC fluxes, but not oxidized OC flux. Near the river, production was modest and biomass high, resulting in low P/B. Outfall deposition resulted in depleted biomass and high bacterial production, resulting in the highest P/B. These patterns explain why this region is production "saturated". The δ(15)N in outfall effluent, sediments and dominant taxa provided insight into where, and which types of organisms feed directly on fresh outfall particulates, on older, refractory material buried in sediments, or utilize chemosynthetic symbiotic bacteria. Results are discussed in the context of declining bottom oxygen conditions along the coast. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Levels of Cd, Cu, Pb and V in marine sediments in the vicinity of the Single Buoy Moorings (SBM3) at Mina Al Fahal in the Sultanate of Oman.

PubMed

Al-Husaini, Issa; Abdul-Wahab, Sabah; Ahamad, Rahmalan; Chan, Keziah

2014-06-15

Recently in the Sultanate of Oman, there has been a rapid surge of coastal developments. These developments cause metal contamination, which may affect the habitats and communities at and near the coastal region. As a result, a study was conducted to assess the level of metal contamination and its impact on the marine sediments in the vicinity of the Single Buoy Moorings 3 (SBM3) at Mina Al Fahal in the Sultanate of Oman. Marine subtidal sediment samples were collected from six different stations of the SBM3 for the period ranging from June 2009 to April 2010. These samples were then analyzed for their level and distribution of the heavy metals of cadmium (Cd), copper (Cu), lead (Pb) and vanadium (V). Overall, low concentrations of all four heavy metals were measured from the marine sediments, indicating that the marine at SBM3 is of good quality. Copyright © 2014 Elsevier Ltd. All rights reserved.

Measuring the role of seagrasses in regulating sediment surface elevation

USGS Publications Warehouse

Potouroglou, Maria; Bull, James C.; Krauss, Ken W.; Kennedy, Hilary A.; Fusi, Marco; Daffonchio, Daniele; Mangora, Mwita M.; Githaiga, Michael N.; Diele, Karen; Huxham, Mark

2017-01-01

Seagrass meadows provide numerous ecosystem services and their rapid global loss may reduce human welfare as well as ecological integrity. In common with the other ‘blue carbon’ habitats (mangroves and tidal marshes) seagrasses are thought to provide coastal defence and encourage sediment stabilisation and surface elevation. A sophisticated understanding of sediment elevation dynamics in mangroves and tidal marshes has been gained by monitoring a wide range of different sites, located in varying hydrogeomorphological conditions over long periods. In contrast, similar evidence for seagrasses is sparse; the present study is a contribution towards filling this gap. Surface elevation change pins were deployed in four locations, Scotland, Kenya, Tanzania and Saudi Arabia, in both seagrass and unvegetated control plots in the low intertidal and shallow subtidal zone. The presence of seagrass had a highly significant, positive impact on surface elevation at all sites. Combined data from the current work and the literature show an average difference of 31 mm per year in elevation rates between vegetated and unvegetated areas, which emphasizes the important contribution of seagrass in facilitating sediment surface elevation and reducing erosion. This paper presents the first multi-site study for sediment surface elevation in seagrasses in different settings and species.

Measuring the role of seagrasses in regulating sediment surface elevation.

PubMed

Potouroglou, Maria; Bull, James C; Krauss, Ken W; Kennedy, Hilary A; Fusi, Marco; Daffonchio, Daniele; Mangora, Mwita M; Githaiga, Michael N; Diele, Karen; Huxham, Mark

2017-09-20

Seagrass meadows provide numerous ecosystem services and their rapid global loss may reduce human welfare as well as ecological integrity. In common with the other 'blue carbon' habitats (mangroves and tidal marshes) seagrasses are thought to provide coastal defence and encourage sediment stabilisation and surface elevation. A sophisticated understanding of sediment elevation dynamics in mangroves and tidal marshes has been gained by monitoring a wide range of different sites, located in varying hydrogeomorphological conditions over long periods. In contrast, similar evidence for seagrasses is sparse; the present study is a contribution towards filling this gap. Surface elevation change pins were deployed in four locations, Scotland, Kenya, Tanzania and Saudi Arabia, in both seagrass and unvegetated control plots in the low intertidal and shallow subtidal zone. The presence of seagrass had a highly significant, positive impact on surface elevation at all sites. Combined data from the current work and the literature show an average difference of 31 mm per year in elevation rates between vegetated and unvegetated areas, which emphasizes the important contribution of seagrass in facilitating sediment surface elevation and reducing erosion. This paper presents the first multi-site study for sediment surface elevation in seagrasses in different settings and species.

Effects of sediment transport on survival of salmonid embryos in a natural stream: A simulation approach

Treesearch

Thomas E. Lisle; Jack Lewis

1992-01-01

A model is presented that simulates the effects of streamflow and sediment transport on survival of salmonid embryos incubating in spawning gravels in a natural channel. Components of the model include a 6-yr streamflow record, an empirical bed load-transport function, a relation between transport and infiltration of sandy bedload into a gravel bed, effects of fine-...

Molar tooth carbonates and benthic methane fluxes in Proterozoic oceans.

PubMed

Shen, Bing; Dong, Lin; Xiao, Shuhai; Lang, Xianguo; Huang, Kangjun; Peng, Yongbo; Zhou, Chuanming; Ke, Shan; Liu, Pengju

2016-01-07

Molar tooth structures are ptygmatically folded and microspar-filled structures common in early- and mid-Proterozoic (∼2,500-750 million years ago, Ma) subtidal successions, but extremely rare in rocks <750 Ma. Here, on the basis of Mg and S isotopes, we show that molar tooth structures may have formed within sediments where microbial sulphate reduction and methanogenesis converged. The convergence was driven by the abundant production of methyl sulphides (dimethyl sulphide and methanethiol) in euxinic or H2S-rich seawaters that were widespread in Proterozoic continental margins. In this convergence zone, methyl sulphides served as a non-competitive substrate supporting methane generation and methanethiol inhibited anaerobic oxidation of methane, resulting in the buildup of CH4, formation of degassing cracks in sediments and an increase in the benthic methane flux from sediments. Precipitation of crack-filling microspar was driven by methanogenesis-related alkalinity accumulation. Deep ocean ventilation and oxygenation around 750 Ma brought molar tooth structures to an end.

Molar tooth carbonates and benthic methane fluxes in Proterozoic oceans

PubMed Central

Shen, Bing; Dong, Lin; Xiao, Shuhai; Lang, Xianguo; Huang, Kangjun; Peng, Yongbo; Zhou, Chuanming; Ke, Shan; Liu, Pengju

2016-01-01

Molar tooth structures are ptygmatically folded and microspar-filled structures common in early- and mid-Proterozoic (∼2,500–750 million years ago, Ma) subtidal successions, but extremely rare in rocks <750 Ma. Here, on the basis of Mg and S isotopes, we show that molar tooth structures may have formed within sediments where microbial sulphate reduction and methanogenesis converged. The convergence was driven by the abundant production of methyl sulphides (dimethyl sulphide and methanethiol) in euxinic or H2S-rich seawaters that were widespread in Proterozoic continental margins. In this convergence zone, methyl sulphides served as a non-competitive substrate supporting methane generation and methanethiol inhibited anaerobic oxidation of methane, resulting in the buildup of CH4, formation of degassing cracks in sediments and an increase in the benthic methane flux from sediments. Precipitation of crack-filling microspar was driven by methanogenesis-related alkalinity accumulation. Deep ocean ventilation and oxygenation around 750 Ma brought molar tooth structures to an end. PMID:26739600

Hydrocarbons in the sediments of the Bermuda region lagoonal to abyssal depths

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

Sletter, T.D.; Butler, J.N.; Barbash, J.E.

1980-01-01

Gas chromatographic analyses of the pentane fraction derived from surface sediments collected from 20 stations (50 cores) around Bermuda from the subtidal zone to 40 m depth and one deep-water sediment sample from 1400 m depth showed that outside the protective boiler reef, the total aliphatic (pentane-extractable) hydrocarbon content was less than inside the reef (3-10 jg/g dry weight outside vs. 10-65 jg/g inside). Samples from the 1400 m depth showed < 1.0 jg/g aliphatic hydrocarbon content. The chromatograms from the shipping channels showed fresh petroleum source concentrations of 8-31 jg/g; harbors yielded chromatograms typical of chronic petroleum contamination, withmore » 30-110 jg/g concentrations. Several biogenic compounds (including C15 and C17 n-alkanes and most probably derived from marine algae) were observed, in addition to the petroleum-derived hydrocarbons. The criteria adopted for distinguishing biogenic and petroleum hydrocarbons are given.« less

Carbon, nutrient and trace metal cycling in sandy sediments: A comparison of high-energy beaches and backbarrier tidal flats

NASA Astrophysics Data System (ADS)

Reckhardt, Anja; Beck, Melanie; Seidel, Michael; Riedel, Thomas; Wehrmann, Achim; Bartholomä, Alexander; Schnetger, Bernhard; Dittmar, Thorsten; Brumsack, Hans-Jürgen

2015-06-01

In order to evaluate the importance of coastal sandy sediments and their contribution to carbon, nutrient and metal cycling we investigated two beach sites on Spiekeroog Island, southern North Sea, Germany, and a tidal flat margin, located in Spiekeroog's backbarrier area. We also analyzed seawater and fresh groundwater on Spiekeroog Island, to better define endmember concentrations, which influence our study sites. Intertidal sandy flats and beaches are characterized by pore water advection. Seawater enters the sediment during flood and pore water drains out during ebb and at low tide. This pore water circulation leads to continuous supply of fresh organic substrate to the sediments. Remineralization products of microbial degradation processes, i.e. nutrients, and dissolved trace metals from the reduction of particulate metal oxides, are enriched in the pore water compared to open seawater concentrations. The spatial distribution of dissolved organic carbon (DOC), nutrients (PO43-, NO3-, NO2-, NH4+, Si(OH)4 and total alkalinity), trace metals (dissolved Fe and Mn) as well as sulfate suggests that the exposed beach sites are subject to relatively fast pore water advection, which leads to organic matter and oxygen replenishment. Frequent pore water exchange further leads to comparatively low nutrient concentrations. Sulfate reduction does not appear to play a major role during organic matter degradation. High nitrate concentrations indicate that redox conditions are oxic within the duneward freshwater influenced section, while ammonification, denitrification, manganese and iron reduction seem to prevail in the ammonium-dominated seawater circulation zone. In contrast, the sheltered tidal flat margin site exhibits a different sedimentology (coarser beach sands versus finer tidal flat sands) and nutrients, dissolved manganese and DOC accumulate in the pore water. Ammonium is the dominant pore water nitrogen species and intense sulfate reduction leads to the formation of sulfide, which precipitates dissolved iron as iron sulfide. These findings are due to slower advective pore water exchange in the tidal flat sediments. This study illustrates how different energy regimes affect biogeochemical cycling in intertidal permeable sediments.

Nature and regional significance of unconformities associated with the Middle Ordovician Hagan K-bentonite complex in the North American midcontinent

USGS Publications Warehouse

Kolata, Dennis R.; Huff, W.D.; Bergstrom, Stig M.

1998-01-01

Stratal patterns of the Middle Ordovician Hagan K-bentonite complex and associated rocks show that the Black River-Trenton unconformity in the North American midcontinent formed through the complex interplay of eustasy, sediment accumulation rates, siliciclastic influx, bathymetry, seawater chemistry, and perhaps local tectonic uplift. The unconformity is diachronous and is an amalgamated surface that resulted from local late Turinian lowstand exposure followed by regional early Chatfieldian transgressive drowning and sediment starvation. The duration of the unconformity is greatest in southern Wisconsin, northern Illinois, and northern Indiana, where the Deicke and Millbrig K-bentonite Beds converge at the unconformity. On the basis of published isotopic ages for the Deicke and Millbrig beds, it is possible that in these regions erosion and non-deposition spanned a period of as much as 3.2 m.y. Two broad coeval depositional settings are recognized within the North American midcontinent during early Chatfieldian time. 1) An inner shelf, subtidal facies of fossiliferous shale (Spechts Ferry Shale Member and Ion Shale Member of the Decorah Formation) and argillaceous lime mudstone and skeletal wackestone (Guttenberg and Kings Lake Limestone Members) extended from the Canadian shield and Transcontinental arch southeastward through Minnesota, Wisconsin, Iowa, and Missouri. 2) A seaward, relatively deep subtidal, sediment-starved, middle shelf extended eastward from the Mississippi Valley region to the Taconian foreland basins in the central and southern Appalachians and southward through the pericratonic Arkoma and Black Warrior basins. In the inner shelf region, the Black River-Trenton unconformity is a composite of at least two prominent hardground omission surfaces, one at the top of the Castlewood and Carimona Limestone Members and the other at the top of the Guttenberg and Kings Lake Limestone Members, both merging to a single surface in the middle shelf region. The inner and middle shelves redeveloped later in approximately the same regions during Devonian and Mississippian time.

Deposition of shallow water sponges in response to seasonal changes

NASA Astrophysics Data System (ADS)

Ávila, Enrique; Carballo, José Luis; Vega, Cristina; Camacho, Leonardo; Barrón-Álvarez, José J.; Padilla-Verdín, Claudia; Yáñez-Chávez, Benjamín

2011-08-01

Removal of organisms from the subtidal zone plays an important role in shaping benthic communities in shallow bays. The main objective of this research was to quantify the biomass of sponges washed up on the beach at Mazatlan Bay (Mexico, eastern Pacific Ocean), and to determine its relationship with local weather and oceanographic conditions. To know whether this process has a significant effect on the sponge populations, changes in abundance of the species washed into the beach were also quantified in adjoining sublittoral areas. The sponges that were washed ashore were mainly branching ( Mycale ramulosa), massive ( Haliclona caerulea) and cushion-shaped ( Callyspongia californica) species. Species with high content of spongin in their structure (e.g. Hyattella intestinalis) were common in the subtidal zone but were rarely found on the beach. Encrusting species were never found. Four-year data of sponge deposition on the beach showed that the total annual sponge biomass ranged from 30 to 60 g DW m - 2 with an inter-annual range from 0.1 to 17.3 g DW m - 2 . The highest deposition of sponges was during the spring-summer transition (from April to July), which was associated with a change in wind direction (from NW to WSW). This change also matched with low tides and a high resuspension of bottom sediments, suggesting a high-energy environment during this transition. The increase in sponge biomass washed on the beach coincided with a decrease in the density of adjacent sponge populations. A multiple regression analysis showed that 68.48% of the variation on sponge biomass on the beach could be statistically explained using a combination of environmental factors (wind speed, sediment resuspension and tides). Thus, seasonal changes in wind direction combined with the effect of low tides and sediment resuspension could serve to predict fragmentation/detachment events of benthic organisms in shallow sublittoral areas worldwide. This study also provides insights to explain the predominance of encrusting sponges in the Mexican Pacific Ocean.

Evaluation of physicochemical and physical habitat associations for Cambarus callainus (Big Sandy crayfish), an imperilled crayfish endemic to the Central Appalachians

USGS Publications Warehouse

Loughman, Zachary J.; Welsh, Stuart A.; Sadecky, Nicole M.; Dillard, Zachary W.; Scott, R. Katie

2017-01-01

1. Crayfish represent one of the most imperilled animal groups on the planet. Habitat degradation, destruction and fragmentation, introduction of invasive crayfishes, and a lack of applied biological information have all been identified as agents thwarting crayfish conservation.2. Cambarus callainus was warranted federal protection by the United States Fish and Wildlife Service (USFWS) in April, 2016. As part of the USFWS listing procedure, a survey for C. callainus in the Big Sandy River catchment was conducted to determine points of occurrence with a secondary objective of determining reach level physical habitat and physicochemical correlates of C. callainus presence and absence.3. At each site, physicochemical and physical habitat data were collected to determine the influence of abiotic covariates on the presence of C. callainus. Cambarus callainus presence or absence and associated site covariates were modelled using logistic regression.4. Survey results recorded C. callainus at 39 sites in the Upper Levisa Fork (ULF) and Tug Fork (TF) drainages of the Big Sandy River; no C. callainus were collected in the Lower Levisa Fork (LLF). An additive effects model of physical habitat quality (Basin + Boulder presence/embeddedness) was the only model selected, supporting an association of C. callainus with slab boulders, open interstitial spaces, and moderate to no sedimentation. All sites lacking C. callainus were experiencing some degree of sedimentation. Physicochemical covariates were not supported by the data.5. Results indicated that good quality habitat was lacking in the LLF, but was present in the ULF and TF catchments, with ULF supporting the most robust populations and most suitable habitat. Effective conservation for C. callainus should focus on efforts that limit sedimentation as well as restore good quality instream habitat in the greater Big Sandy catchment.

Concentration of Natural Gas Hydrate Beneath the Permafrost Zone: Implications for Geochemical and Hydrologic Investigations

NASA Astrophysics Data System (ADS)

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

2004-12-01

Gas hydrates are ice-like solids made of water molecules containing various gas molecules. The geological evaluations have suggested worldwide methane contents of gas hydrate beneath deep sea floors as well as permafrost-related zones to about twice the total reserves of conventional and unconventional hydrocarbon. Scientific and economic interests are increasing in gas hydrate as a new energy resource and a potential greenhouse gas. In 1998 and 2002 Mallik wells were drilled in the Canadian Arctic that clarified the characteristics of gas hydrate-dominant layers at depths from 890 to 1110 m beneath the permafrost zone. Continuous downhole well log data, anomalies of chloride contents in pore waters, core temperature depression as well as visible gas hydrates have confirmed the highly saturated pore-space hydrate as intergranular pore filling within sandy layers, whose saturations are higher than 70% in pore volume. Muddy sediments scarcely contain gas hydrate. The Nankai Trough runs along the Japanese Island, where forearc basins and accretionary prisms developed extensively and BSRs (bottom simulating reflectors) have been recognized widely. The METI Nankai Trough wells in 2000 also revealed the presence of pore-space hydrate filling intergranular pore of sandy layers. It is remarked that there are many similar features in appearance and characteristics between the Mallik and Nankai Trough areas with observations of well-interconnected and highly saturated pore-space hydrate. It is necessary for evaluating subsurface fluid flow behaviors to know both porosity and permeability of gas hydrate-bearing sandy sediments, and measurements of water permeability for them indicate that highly saturated sands may have permeability of a few millidarcies. Subsequent analyses in sedimentology and geochemistry performed on gas hydrate-bearing sands revealed important geologic and sedimentologic controls on the formation and concentration of gas hydrate. It is suggested that the distribution of a porous and coarser-grained sandy sediments is one of the most important factors to control the occurrence of gas hydrates, as well as physicochemical conditions.

Impacts of Near-Future Ocean Acidification and Warming on the Shell Mechanical and Geochemical Properties of Gastropods from Intertidal to Subtidal Zones.

PubMed

Leung, Jonathan Y S; Connell, Sean D; Nagelkerken, Ivan; Russell, Bayden D

2017-11-07

Many marine organisms produce calcareous shells as the key structure for defense, but the functionality of shells may be compromised by ocean acidification and warming. Nevertheless, calcifying organisms may adaptively modify their shell properties in response to these impacts. Here, we examined how reduced pH and elevated temperature affect shell mechanical and geochemical properties of common grazing gastropods from intertidal to subtidal zones. Given the greater environmental fluctuations in the intertidal zone, we hypothesized that intertidal gastropods would exhibit more plastic responses in shell properties than subtidal gastropods. Overall, three out of five subtidal gastropods produced softer shells at elevated temperature, while intertidal gastropods maintained their shell hardness at both elevated pCO 2 (i.e., reduced pH) and temperature. Regardless of pH and temperature, degree of crystallization was maintained (except one subtidal gastropod) and carbonate polymorph remained unchanged in all tested species. One intertidal gastropod produced less soluble shells (e.g., higher calcite/aragonite) in response to reduced pH. In contrast, subtidal gastropods produced only aragonite which has higher solubility than calcite. Overall, subtidal gastropods are expected to be more susceptible than intertidal gastropods to shell dissolution and physical damage under future seawater conditions. The increased vulnerability to shell dissolution and predation could have serious repercussions for their survival and ecological contributions in the future subtidal environment.

Book Review: Interdisciplinary Archaeological Research Programme Maasvlakte 2

NASA Astrophysics Data System (ADS)

Innes, J. B.

2015-10-01

Archaeological investigation in wetland environments has long been recognised as a specialised aspect of the discipline, where the levels of preservation of organic materials and sediments can be so high that cultural horizons and excavated artefacts can be placed into detailed palaeo-environmental, biological and landscape contexts, in contrast to the more limited information of this kind that is available from dryland archaeological sites. Inevitably, the recovery, integration and understanding of these vital additional data require an interdisciplinary approach and an investment in specialist equipment and scientific analyses if their full potential for reconstructing human occupation and site use within their landscape setting is to be fully realised. The mobilisation and integration of such a team of environmental specialists can require major financial resources, meticulous planning and close co-operation between the various disciplines involved. The most extreme example of wetland archaeology is probably integrated excavation and environmental archaeological research in subtidal locations, but modern development of major coastal infrastructure is increasingly making sites available for study from the early to mid-Holocene or even earlier that have been overwhelmed by sea-level rise and which would otherwise be beyond the reach of archaeological investigation. Such very large scale subtidal interdisciplinary research projects are major, expensive and long-term undertakings and are still rare enough to be publication highlights in the discipline of environmental archaeology. Important recent examples of subtidal work in north-west Europe include Pedersen et al. (1997) and elements of Fischer (1995) in south Scandinavia, and investigations off southern England (Allen and Gardiner, 2000; Momber et al., 2011; Sturt et al., 2014). Research on submerged palaeoenvironments and palaeolandscapes has also seen significant advances (Griffiths et al., 2015), with the reconstruction of the Mesolithic palaeogeography of the central North Sea, dubbed 'Doggerland', perhaps the most significant achievement (Gaffney et al., 2009). This new volume, edited by J.M. Moree and M.M. Sier, forms an impressive contribution to the genre of subtidal interdisciplinary environmental archaeology, and is an excellent example of the high quality academic research we have come to expect from Dutch workers, in a well organised and well illustrated monograph.

Tidal River Elbe - a sediment budget for the grain size fraction of medium sand

NASA Astrophysics Data System (ADS)

Winterscheid, Axel

2016-04-01

Human interventions have a historic and ongoing impact on estuarine sediment budgets across many estuaries worldwide. An early inference was the construction of embankments resulting in a constant loss of intertidal flats. Additionally, settlement activities and large scale land use changes in the upstream catchment areas had also an effect on sediment inflow rates. Today, the navigation channels in estuaries have been deepened for larger and more efficient vessels to reach a well-developed infrastructure of harbors and industrial areas often located far inland. In the past few years and just within the North-East Atlantic, the total annual amount of dredged sediments dumped at sea varied from 80 to 130 million tons (OSPAR Commission). In most estuaries across Europe the resulting human impact on the sediment fluxes and morphodynamics is significant. A good understanding of estuarine processes is essential for determining useful and meaningful measures to mitigate negative effects and to improve the current situation. Maintenance dredging and its environmental effects are therefore in the focus of public attention. Against this background, it is the aim of the presentation to identify and therefore to separate the particular effect that maintenance dredging has on sediment fluxes and budgets in the estuarine environment. Case study is the Tidal River Elbe in Germany, and here we set the focus on the grain size fraction of medium sand. In the past, river engineering measures forced the natural dynamics to form a concentrated stream flow along a fixed channel, except at a number of locations where side channels still exist. In addition to that, the main channel was deepened several times. The last deepening was in 1999/2000. The most significant deepening, however, took place from 1957 to 1962. Until then, an erosion-stable layer of marine clay (in German called "Klei") formed a flat bottom along most sections of the main channel. After removal of this layer of marine clay by capital dredging, Weichselion sandy deposits, which formed the geological layer underneath, now became part of the sediment transport regime. Nowadays, most sections of the main channel are morphologically characterized by a medium sandy river bed and subaquatic dunes of several meters height followed by sections of a poorly structured river bed caused by the sedimentation of silty sediments. By setting up the sediment balance for medium sand, the fluxes entering the estuary from the inland Elbe is one source term in the equation. The average annual load for the medium sand is estimated to be 110,000 m³/year (1996 - 2008, measurement station Neu Darchau). Further downstream in the tidal part of the river there are no further measurement stations located, but the analysis of a time series of multibeam sonar data (2000 to 2014) shows that large amounts of medium sand episodically pass the tidal weir at Geesthacht only in the event of extreme flood. This is due to a significant increase in bed volume between Geesthacht and the Port of Hamburg in the aftermath of a singular extreme event. Until the next extreme event the bed volume (functions as temporary storage for medium sand) is eroding again, which is the second source term. By comparing the information on bed load fluxes, the evolution of bed volumes over time and the dredging statistics we can conclude for the longer term that the total amount of medium sand that has been dredged and taken out of the system for constructional purposes is the same order of magnitude compared to the sum of both source terms. Hence, there is no or very limited net transport of medium sand passing the port area and entering the downstream river section. From the subsequent analysis of multibeam sonar data (2008 - 2014) we know for the river section from Hamburg to Brunsbuettel (total distance of 40 km) that there has been a continuous loss of about 1 Mio. m³/a in bed volumes, which means a deficit situation for medium sand. Currently, the Weichselion deposit is the active source for medium sand, but due to the lack of medium sand fluxes from upstream this at the cost of having an ongoing deepening of the main channel. The presumed cause for this deficit situation is the current management of the sandy dredged material. First of all, dredging and subsequent extraction of the dredged material is strongly affecting the longitudinal transport of medium sandy sediments from upstream through the Port of Hamburg in seaward direction. Further downstream in the river section in deficit, all dredged material, which is about 1 Mio m³/a solely for the fraction of medium sand, is transported by hopper dredgers over a long distance up to 40 km in seaward direction and disposed on a single site near Brunsbuettel. This 1 Mio m³/a is a similar volume in comparison to the loss in bed volume. From an analysis of the geometry of the subaquatic dunes we know for sandy sediments a seaward net transport that exists for large parts of this river section. All in one, there is an irretrievable and ongoing loss of medium sandy sediments. Vice versa for the river section next to Brunsbuettel, which is the location of the disposal site, the data show an increase of bed volumes and dredging amounts at the same time. For the Elbe case study we could demonstrate that maintenance dredging (and the subsequent disposal) could have a significant impact on the large scale sediment budget. Appropriate measures to stabilize the sediment budget in the inner part of the Tidal River Elbe for medium sand is (a) to dispose all medium sandy dredged material as close as possible to the location of dredging and (b) to reduce the extraction of medium sand in the Hamburg Port area.

Inducible variation in anaerobic energy metabolism reflects hypoxia tolerance across the intertidal and subtidal distribution of the Pacific oyster (Crassostrea gigas).

PubMed

Meng, Jie; Wang, Ting; Li, Li; Zhang, Guofan

2018-07-01

Pacific oyster (Crassostrea gigas) distribute a steep gradient of environmental stress between intertidal and subtidal habits and provide insight into population-scale patterns and underlying processes of variation in physiological tolerance. In this study, 1-year-old-F 1 oysters, collected from subtidal and intertidal habitats, were obtained after common garden experiment. Genetic differentiation and physiological responses under air exposure were examined to determine whether they had evolved into local adapted subpopulations. Mortality rate, anaerobic glycolysis metabolism, and energy status indicated that oyster had initiated metabolism depression and anaerobic glycolysis metabolism in both intertidal and subtidal oysters under air exposure. However, the subtidal oysters displayed the larger energy metabolism depressions and the earlier anaerobic glycolysis responses. This may indicate that subtidal oysters were more sensitives to hypoxia stress, which may lead the higher mortality rate under long term of air exposure. Based on a common garden experimental design, we propose that this diversification may have a genetic background. Overall, the clear differences between intertidal and subtidal oysters under air exposure have provided an important reference for their aquaculture and transportation used in commercial production. Copyright © 2018. Published by Elsevier Ltd.

Toxicological and chemical assessment of ordnance compounds in marine sediments and porewaters

USGS Publications Warehouse

Nipper, M.; Carr, R.S.; Biedenbach, J.M.; Hooten, R.L.; Miller, K.

2002-01-01

Toxicological and chemical studies were performed with a silty and a sandy marine sediment spiked with 2,6-dinitrotoluene (2,6-DNT), 2,4,6-trinitrophenylmethylnitramine (tetryl), or 2,4,6-trinitrophenol (picric acid). Whole sediment toxicity was analyzed by the 10-day survival test with the amphipod Ampelisca abdita, and porewater toxicity tests assessed macro-algae (Ulva fasciata) zoospore germination and germling growth, sea urchin (Arbacia punctulata) embryological development, and polychaete (Dinophilus gyrociliatus) survival and reproduction. Whole sediments spiked with 2,6-DNT were not toxic to amphipods. The fine-grained sediment spiked with tetryl was also not acutely toxic. The tetryl and picric acid LC50 values in the sandy sediment were 3.24 and 144 mg/kg dry weight, respectively. The fine-grained sediment spiked with picric acid generated a U-shaped concentration-response curve in the amphipod test, with increased survival both in the lowest and highest concentration. Grain-size distribution and organic carbon content strongly influenced the behavior of ordnance compounds in spiked sediments. Very low concentrations were measured in some of the treatments and irreversible binding and biodegradation are suggested as the processes responsible for the low measurements. Porewater toxicity varied with its sedimentary origin and with ordnance compound. The sea urchin embryological development test tended to be the least sensitive. Tetryl was the most toxic chemical in all porewater tests, and picric acid the least toxic. Samples spiked with 2,6-DNT contained a degradation product identified as 2-methyl-3-nitroaniline (also known as 2-amino-6-nitrotoluene), and unidentified peaks, possibly degradation products, were also seen in some of the picric acid- and tetryl-spiked samples. Degradation products may have played a role in observed toxicity. ?? 2002 Elsevier Science Ltd. All rights reserved.

Sedimentary constraints on the development of a narrow deep strait (São Sebastião Channel, SE Brazil)

NASA Astrophysics Data System (ADS)

Alcántara-Carrió, Javier; Sasaki, Dalton Kei; Mahiques, Michel Michaelovitch de; Taborda, Rui; de Souza, Luiz Antonio Pereira

2017-10-01

The São Sebastião Channel (SSC), which separates São Sebastião Island from the continent, is a deep elongated strait on the inner shelf of the São Paulo Bight (SE Brazil). The aim of this study is to explain why it is presently sediment starved, instead of forming a tombolo. Wave data were obtained from both a WW3 model database and buoy records, and wave propagation patterns from the SWAN numerical model. Grain size trend analysis of 579 surficial sediment samples from the strait and the surrounding region served to estimate the residual transport directions. Bedload sediment transport was computed considering in situ currents and bottom sediment grain size. Moreover, six seismic profiles and one gravity core were obtained in the strait in order to evaluate the hickness of the sedimentary deposits. The geometry of the SSC (X/B=0.3, where B is the breakwater or island diameter and X is its cross-shore distance to the mainland) predicts that a tombolo should be formed, and wave patterns confirm that it is a zone sheltered from both S and NE waves. Previous studies have shown that the hydrodynamics of the SSC is controlled by wind-driven currents, which are more intense in the eastern and central sectors of the strait. The western sector is currently covered by sandy mud, whereas very coarse to fine sand prevails in the deeper eastern sector. Sediment patterns show a trend to deposition of fine sediment in the western sector of the SSC and two main depocentres located at the northern limit of the study area and at the southern mouth of the strait. Sandy mud in the western sector forms a 40-m-thick deposit close to the outer limit of Araçá Bay, whereas the remainder of the SSC is covered by a very thin layer of sandy sediments. Dominance of mud in the depositional western sector suggests low availability of sand in the area. Therefore, despite the geometry and wave patterns of the SSC favouring the formation of a tombolo, the dominance of wind-driven currents and the low availability of sand determine that such a sedimentary feature cannot be formed, resulting in a deep strait.

A water balance model to estimate flow through the Old and Middle River corridor

USGS Publications Warehouse

Andrews, Stephen W.; Gross, Edward S.; Hutton, Paul H.

2016-01-01

We applied a water balance model to predict tidally averaged (subtidal) flows through the Old River and Middle River corridor in the Sacramento–San Joaquin Delta. We reviewed the dynamics that govern subtidal flows and water levels and adopted a simplified representation. In this water balance approach, we estimated ungaged flows as linear functions of known (or specified) flows. We assumed that subtidal storage within the control volume varies because of fortnightly variation in subtidal water level, Delta inflow, and barometric pressure. The water balance model effectively predicts subtidal flows and approaches the accuracy of a 1–D Delta hydrodynamic model. We explore the potential to improve the approach by representing more complex dynamics and identify possible future improvements.

Plastic pollution on the Baltic beaches of Kaliningrad region, Russia.

PubMed

Esiukova, Elena

2017-01-30

Contamination of sandy beaches of the Baltic Sea in Kaliningrad region is evaluated on the base of surveys carried out from June 2015 to January 2016. Quantity of macro/meso/microplastic objects in the upper 2cm of the sandy sediments of the wrack zone at 13 sampling sites all along the Russian coast is reported. Occurrence of paraffin and amber pieces at the same sites is pointed out. Special attention is paid to microplastics (range 0.5-5mm): its content ranges between 1.3 and 36.3 items per kg dry sediment. The prevailing found type is foamed plastic. No sound differences in contamination are discovered between beaches with high and low anthropogenic load. Mean level of contamination is of the same order of magnitude as has been reported by other authors for the Baltic Sea beaches. Copyright © 2016 Elsevier Ltd. All rights reserved.

Lower Miocene stratigraphy of the Gebel Shabrawet area, north Eastern desert Egypt

NASA Astrophysics Data System (ADS)

Abdelghany, Osman

2002-05-01

The Lower Miocene carbonate/siliciclastic sequence of the Shabrawet area, comprises a complex alternation of autochthonous and allogenic sediments. The sequence can be subdivided into two lithostratigraphic units. The lower unit (unit I) is equivalent to the Gharra Formation. It is mainly clastic and composed of sandstones, siltstones and shales with minor limestone intercalations. These sediments are rich in Clypeaster spp., Scutella spp., Miogypsina intermedia, Operculina complanata, and smaller foraminifera. The upper unit (unit II) was considered by previous workers as being equivalent to the Marmarica Formation. It consists mainly of non-clastic rocks, dominated by sandy and chalky limestones rich in larger foraminifera (miogypsinids and nummulitids). This unit is topped by a highly fossiliferous ( Heterostegina, Operculina and Planostegina) sandy limestone. The present study places both units in the Gharra Formation and reports for the first time M. intermedia from the Miocene sequence of the Shabrawet area.

Photosynthesis as a Possible Source of Gas Bubbles in Shallow Sandy Coastal Sediments

DTIC Science & Technology

2011-09-30

bubbles can be formed when photosynthesis by benthic microalgae causes pore water to become supersaturated with oxygen. OBJECTIVES The next...reflectivity. We also collected sediment samples from the upper few mm of sand to identify the dominant taxa of benthic microalgae present. After...Graduate School of Oceanography / University of Rhode Island (GSO/URI) to identify the benthic microalgae in the samples. Following the untimely death of

Photosynthesis as a Possible Source of Gas Bubbles in Shallow Sandy Coastal Sediments

DTIC Science & Technology

2012-09-30

clearly demonstrates that gas bubbles can be formed when photosynthesis by benthic microalgae causes pore water to become supersaturated with oxygen...We also collected sediment samples from the upper few mm of sand to identify the dominant taxa of benthic microalgae present. Although benthic...Jan Rines (Graduate School of Oceanography / University of Rhode Island = GSO/URI) to identify the benthic microalgae in the samples. Following the

Analyze of waves dynamic over an intertidal mudflat of a sandy-gravely estuarine beach - Field survey and preliminary modeling approach

NASA Astrophysics Data System (ADS)

Morio, Olivier; Sedrati, Mouncef; Goubert, Evelyne

2014-05-01

As well as marine submersion or erosive phenomena, clay-silted sediment in-filling on estuarial and bay beaches are a main issue in these human-attractive areas. Coupled sandy/gravely and clay/silty intertidal areas can be observed in these particular coastal areas, depending of rivers characteristic (discharge of particle, water flow), ocean dynamics (wave exposure, current) and sediments sources. All around the world, sandy/gravely beaches are exposed to punctual or continuous input clay sediments. Vilaine estuary, Bay of Arcachon and Bay of Seine in France, Plymouth Bay in UK and also Wadden Sea in Deutschland are few examples of muddy/sandy coupled or mixed system. The beach of Bétahon (Ambon town, Brittany - France) is located on the external Vilaine estuary and is an example of this issue. This meso-macrotidal intermediate (low tide terrace) beach presents heterogeneous sediments. The upper intertidal zone is composed by sand and gravel and characterized by a steep slope. A very gentle slope characterized the lower part of the beach and is constituted by silt and clay. Clay/sand limit is characterized by a decimetric erosion cliff of mudflat along the beach. In order to understand bed variations and sediment transport of this complex heterogeneous beach, a well understanding of wave dynamic across the beach is necessary. This study focus on wave dynamics over the beach, using field observations and MIKE 21 3D wave numerical model. This paper is a preliminary approach of an upcoming global understanding of this estuarial beach behavior. Swell from deep-sea to near-shore area is modeled over a 100 km² area and real wind, deep sea wave characteristic, river water flow and tidal level are defined as open boundary conditions for the regional model. This last one is based on multiple bathymetric surveys over the last 50 years. Local model, triangular mesh gridded to 5 meters, covering Bétahon beach , is based on topographic and photographic survey of the mudflat since 2005 (an amplitude above 1.4 meters has been observed over a start reference state). Modeling significant wave height, wave direction and period are compared to a cross-shore wave dynamics survey over the beach, during one week. Surf zone positions over the beach, wave characteristics at local and regional scales, impacts of mudflat altitude on waves are analyzed and discussed.

Historical sediment budget and present-day catchment-shoreline coupling at Twofold Bay, southeastern Australia

NASA Astrophysics Data System (ADS)

Tamura, T.; Oliver, T.; Hudson, J.; Woodroffe, C. D.

2017-12-01

Considering projected impacts of sea-level rise in the 21st century on sandy shorelines, an understanding of long-term sediment budget for individual beaches or coastal compartments supports assessments of shoreline stability. We examined a low-lying coastal beach-ridge barrier in Twofold Bay using optically stimulated luminescence (OSL) dating , airborne LiDAR, sedimentological analysis and seismic data to assess changes in rates of sediment supply to this shoreline through time. Calculations of barrier volume, Twofold Bay bay-floor sediment volume and estimates of sediment delivery from a proximal river system provide a broad-scale assessment of past-sediment budget. Between ca. 7500 years ago and 1500 years ago, sources of sediment for shoreline progradation at Boydtown were bay-floor sediments either inherited or moved into the embayment during late-stage transgression. Progradation rate between ca. 7500-1500 years ago was 0.16 m/yr with subaerial barrier volume accumulating at 0.46 m3/m/yr. Between ca. 1500 years and present day, the Towamba River to the south has delivered additional sediment to the Boydtown shoreline more than doubling shoreline progradation rate to 0.65 m/yr and subaerial barrier accumulation has risen to 1.83 m3/m/yr. The delivery of fluvial sediment from the Towamba River was restricted to the past ca. 1500 years as prior to this, estuary infilling prevented floods delivering sediments to the bay. This recent historical coupling of river sand supply and shoreline progradation rate implies that anthropogenic modifications to the Towamba River catchment such as river damming, or climatic changes reducing rainfall or runoff, would negatively impact the Boydtown Beach shoreline. Conversely increased rainfall or deforestation may increase sediment discharge due to upstream erosion. The Boydtown shoreline within Twofold Bay may be able to maintain its current position in the coming century if fluvial sediment delivery continues. The fact that other shorelines within Twofold Bay are seemingly unaffected by the Towamba River, and most shorelines in southeast Australia receive minimal fluvial sediment input, further emphasises the need to consider nearshore sediment reserves in order to accurately determine sea-level rise impacts on sandy shorelines.

Aeolian Environments of Iceland

NASA Astrophysics Data System (ADS)

Arnalds, Olafur; Olafsson, Haraldur; Dagsson Waldhauserová, Pavla

2017-04-01

Iceland has the largest area of volcaniclastic sandy desert on Earth or 22,000 km2. The sand has been mostly produced by glacio-fluvial processes, leaving behind fine-grained unstable sediments which are later re-distributed by repeated aeolian events. Volcanic eruptions add to this pool of unstable sediments, often from subglacial eruptions. Icelandic desert surfaces are divided into sand fields, sandy lavas and sandy lag gravel, each with separate aeolian surface characteristics such as threshold velocities. Storms are frequent due to Iceland's location on the North Atlantic Storm track. Dry winds occur on the leeward sides of mountains and glaciers, in spite of the high moisture content of the Atlantic cyclones. Surface winds often move hundreds to more than 1000 kg m-1 per annum, and more than 10,000 kg m-1 have been measured in a single storm. Desertification occurs when aeolian processes push sand fronts and have thus destroyed many previously fully vegetated ecosystems since the time of the settlement of Iceland in the late ninth century. There are about 135 dust events per annum, ranging from minor storms to >300,000 t of dust emitted in single storms. Dust can be generated from all the major sandy areas of Iceland; however the amount of finer particles that become dust varies with the surfaces. There are areas that produce more dust by far compared to the general sandy deserts; they have therefore been termed "dust plume areas" or "dust hot-spots". They are characterized by repeated charging of fine sediments with a relatively high proportion of finer (silty) materials which, upon repeated wind erosion become sorted downwind from the sources with loss of silt (dust) and an increasing saltation component (sand). Dust production is on the order of 30-40 million tons annually, some travelling over 1000 km and deposited on land and sea. Dust deposited on deserts tends to be re-suspended during subsequent storms. High PM10 concentrations occur during major dust storms. They are more frequent in the wake of volcanic eruptions, such as after the Eyjafjallajökull 2010 eruption. Airborne dust affects human health, with negative effects enhanced by the tubular morphology of the grains, and the basaltic composition with its high metal content. Dust deposition on snow and glaciers intensifies melting. Moreover, the dust production probably also influences atmospheric conditions and parameters that affect climate change.

Sedimentological and GPR studies of subglacial deposits in the Joux Valley (Vaud, Switzerland): backset accretion in an esker followed by an erosive jokulhlaup

USGS Publications Warehouse

Fiore, J.; Pugin, A.; Beres, N.

2002-01-01

During the Wu??rmian glaciation, the Jura ice sheet covered the Joux Valley (Vaud, Switzerland). A geomorphological study reveals many drumlins in this valley. Some are composed of gravels and sand, others of till. Outcrops show that the surface of the sandy-gravel drumlins is a major and sharp erosion surface. Given the lack of shearing structures in sediments below this erosion level, its origin cannot be linked to ice action of the glacier. Very high-energy subglacial meltwater floods (jo??kulhlaups), probably due to the drainage of subglacial or supraglacial lakes, are the more likely cause of the erosion. Results of a ground penetrating radar (GPR) survey show the internal structure of one of these sandy-gravel drumlins to depth of 15 m. These GPR data, together with sedimentological observations, indicate that prior to erosion, subglacial sedimentation occurred in closed conduits (eskers) with strong and rapid flow variations. The sediments contain large chute-and-pool structures (high flow energy backset accretion) with dimensions comparable to the conduit width. Therefore, we interpret these sandy-gravel drumlins as portions of eskers, their present drumlin shape being the result of erosion by one or many jo??kulhlaups. The good preservation of the subglacial meltwater deposits is the result of the closed-basin geometry of the Joux Valley, which limited movement at the base of the glacier. This new contribution to the interpretation of the Joux Valley glacial features underlines the importance of meltwater in sedimentological processes under the Jura ice sheet.

Sedimentary deposits of the 26 December 2004 tsunami on the northwest coast of Aceh, Indonesia

USGS Publications Warehouse

Moore, A.; Nishimura, Y.; Gelfenbaum, G.; Kamataki, T.; Triyono, R.

2006-01-01

The 2004 Sumatra-Andaman tsunami flooded coastal northern Sumatra to a depth of over 20 m, deposited a discontinuous sheet of sand up to 80 cm thick, and left mud up to 5 km inland. In most places the sand sheet is normally graded, and in some it contains complex internal stratigraphy. Structures within the sand sheet may record the passage of up to 3 individual waves. We studied the 2004 tsunami deposits in detail along a flow-parallel transect about 400 m long, 16 km southwest of Banda Aceh. Near the shore along this transect, the deposit is thin or absent. Between 50 and 400 m inland it ranges in thickness from 5 to 20 cm. The main trend in thickness is a tendency to thicken by filling low spots, most dramatically at pre-existing stream channels. Deposition generally attended inundation - along the transect, the tsunami deposited sand to within about 40 m of the inundation limit. Although the tsunami deposit contains primarily material indistinguishable from material found on the beach one month after the event, it also contains grain sizes and compositions unavailable on the current beach. Along the transect we studied, these grains become increasingly dominant both landward and upward in the deposit; possibly some landward source of sediment was exposed and exploited by the passage of the waves. The deposit also contains the unabraded shells of subtidal marine organisms, suggesting that at least part of the deposit came from offshore. Grain sizes within the deposit tend to fine upward and landward, although individual units within the deposit appear massive, or show reverse grading. Sorting becomes better landward, although the most landward sites generally become poorly sorted from the inclusion of soil clasts. These sites commonly show interlayering of sandy units and soil clast units. Deposits from the 2004 tsunami in Sumatra demonstrate the complex nature of the deposits of large tsunamis. Unlike the deposits of smaller tsunamis, internal stratigraphy is complex, and will require some effort to understand. The Sumatra deposits also show the contribution of multiple sediment sources, each of which has its own composition and grain size. Such complexity may allow more accurate modeling of flow depth and flow velocity for paleotsunamis, if an understanding of how tsunami hydraulics affect sedimentation can be established. Copyright ?? The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB.

Use of geological mapping tools to improve the hydraulic performance of SuDS.

PubMed

Bockhorn, Britta; Klint, Knud Erik Strøyberg; Jensen, Marina Bergen; Møller, Ingelise

2015-01-01

Most cities in Denmark are situated on low permeable clay rich deposits. These sediments are of glacial origin and range among the most heterogeneous, with hydraulic conductivities spanning several orders of magnitude. This heterogeneity has obvious consequences for the sizing of sustainable urban drainage systems (SuDS). We have tested methods to reveal geological heterogeneity at field scale to identify the most suitable sites for the placement of infiltration elements and to minimize their required size. We assessed the geological heterogeneity of a clay till plain in Eastern Jutland, Denmark measuring the shallow subsurface resistivity with a geoelectrical multi-electrode system. To confirm the resistivity data we conducted a spear auger mapping. The exposed sediments ranged from clay tills over sandy clay tills to sandy tills and correspond well to the geoelectrical data. To verify the value of geological information for placement of infiltration elements we carried out a number of infiltration tests on geologically different areas across the field, and we observed infiltration rates two times higher in the sandy till area than in the clay till area, thus demonstrating that the hydraulic performance of SuDS can be increased considerably and oversizing avoided if field geological heterogeneity is revealed before placing SuDS.

Anatomy of a cyclically packaged Mesoproterozoic carbonate ramp in northern Canada

NASA Astrophysics Data System (ADS)

Sherman, A. G.; Narbonne, G. M.; James, N. P.

2001-03-01

Carbonates in the upper member of the Mesoproterozoic Victor Bay Formation are dominated by lime mud and packaged in cycles of 20-50 m. These thicknesses exceed those of classic shallowing-upward cycles by almost a factor of 10. Stratigraphic and sedimentological evidence suggests high-amplitude, high-frequency glacio-eustatic cyclicity, and thus a cool global climate ca. 1.2 Ga. The Victor Bay ramp is one of several late Proterozoic carbonate platforms where the proportions of lime mud, carbonate grains, and microbialites are more typical of younger Phanerozoic successions which followed the global waning of stromatolites. Facies distribution in the study area is compatible with deposition on a low-energy, microtidal, distally steepened ramp. Outer-ramp facies are hemipelagic lime mudstone, shale, carbonaceous rhythmite, and debrites. Mid-ramp facies are molar-tooth limestone tempestite with microspar-intraclast lags. In a marine environment where stromatolitic and oolitic facies were otherwise rare, large stromatolitic reefs developed at the mid-ramp, coeval with inner-ramp facies of microspar grainstone, intertidal dolomitic microbial laminite, and supratidal evaporitic red shale. Deep-subtidal, outer-ramp cycles occur in the southwestern part of the study area. Black dolomitic shale at the base is overlain by ribbon, nodular, and carbonaceous carbonate facies, all of which exhibit signs of synsedimentary disruption. Cycles in the northeast are shallow-subtidal and peritidal in character. Shallow-subtidal cycles consist of basal deep-water facies, and an upper layer of subtidal molar-tooth limestone tempestite interbedded with microspar calcarenite facies. Peritidal cycles are identical to shallow-subtidal cycles except that they contain a cap of dolomitic tidal-flat microbial laminite, and rarely of red shale sabkha facies or of sandy polymictic conglomerate. A transect along the wall of a valley extending 8.5 km perpendicular to depositional strike reveals progradation of inner-ramp tidal flats over outer- and mid-ramp facies during shoaling. The maximum basinward progradation of peritidal facies coincides with a zone of slope failure that may have promoted the development of the stromatolitic reefs. The sea-level history of the Victor Bay Formation is represented by three hectometre-scale sequences. An initial flooding event resulted in deposition of the lower Victor Bay shale member. Upper-member carbonate cycles were then deposited during highstand. Mid-ramp slumping was followed by late-highstand reef development. The second sequence began with development of an inner-ramp lowstand unconformity and a thick mid-ramp lowstand wedge. A second transgression promoted a more modest phase of reef development at the mid-ramp and shallow-water deposition continued inboard. A third and final transgressive episode eventually led to flooding of the backstepping ramp. Overall consistent cycle thickness and absence of truncated cycles, as well as the high rate and amount of creation of accommodation space, suggest that the periodicity and amplitude of sea-level fluctuation were relatively uniform, and point to a eustatic rather than tectonic mechanism of relative sea-level change. High-amplitude, high-frequency eustatic sea-level change is characteristic of icehouse worlds in which short-term, large-scale sea-level fluctuations accompany rapidly changing ice volumes affected by Milankovitch orbital forcing. Packaging of cyclic Upper Victor Bay carbonates therefore supports the hypothesis of a late Mesoproterozoic glacial period, as proposed by previous workers.

Sandy beaches: state of the art of nematode ecology.

PubMed

Maria, Tatiana F; Vanaverbeke, Jan; Vanreusel, Ann; Esteves, André M

2016-01-01

In this review, we summarize existing knowledge of the ecology of sandy-beach nematodes, in relation to spatial distribution, food webs, pollution and climate change. We attempt to discuss spatial scale patterns (macro-, meso- and microscale) according to their degree of importance in structuring sandy-beach nematode assemblages. This review will provide a substantial background on current knowledge of sandy-beach nematodes, and can be used as a starting point to delineate further investigations in this field. Over decades, sandy beaches have been the scene of studies focusing on community and population ecology, both related to morphodynamic models. The combination of physical factors (e.g. grain size, tidal exposure) and biological interactions (e.g. trophic relationships) is responsible for the spatial distribution of nematodes. In other words, the physical factors are more important in structuring nematodes communities over large scale of distribution while biological interactions are largely important in finer-scale distributions. It has been accepted that biological interactions are assumed to be of minor importance because physical factors overshadow the biological interactions in sandy beach sediments; however, the most recent results from in-situ and ex-situ experimental investigations on behavior and biological factors on a microscale have shown promise for understanding the mechanisms underlying larger-scale patterns and processes. Besides nematodes are very promising organisms used to understand the effects of pollution and climate changes although these subjects are less studied in sandy beaches than distribution patterns.

Identification of Sungai Batu Sediment using 2-D Resistivity Imaging and Seismic Refraction Methods for Ancient River Mapping at Kedah, Malaysia

NASA Astrophysics Data System (ADS)

Andika, F.; Saad, R.; Saidin, M. M.; Muztaza, N. M.; Amsir

2018-04-01

Sungai Batu is an earliest civilization in Southeast Asia with evidenced by the discovery of riverside jetty, iron smelting, and ritual monuments. The evidences can lead to prediction of buried river caused by geological and sedimentation process. This study was conducted to study sediment deposit characteristic and to map thickness of the sediments using 2-D resistivity imaging and seismic refraction for ancient river mapping. A total of thirty, 2-D resistivity and nine seismic survey lines were conducted at the study area. Four of the lines R1-R4 and S1-S4 were correlated and validated with existing on site boreholes BH1-BH4 to identify sediment type and thickness. The validated values applied to the remaining survey lines which no borehole record to map the subsurface of the study area. Based on the results, Sungai Batu area consist of clay with resistivity value of 6.6-25.9 Ω.m and velocity value of 716.9-1606.9 m/s; sandy clay with resistivity value of 6-265.1 Ω.m and velocity value of 1003.6-1901.4 m/s; while shale was identified with resistivity value of >668.6 Ω.m and velocity value of >2051.7 m/s. Boundary between clay/sandy clay with shale was identified with resistivity value of 314 Ω.m and velocity value of 1822 m/s. The integration of the 2-D resistivity and seismic refraction identified that the thickness of Sungai Batu sediment is 0-150 m and Sungai Batu ancient river was successfully map based on thickness of sediment which is >45 m.

Applying a two-dimensional morphodynamic model to assess impacts to Chinook salmon spawning habitat from dam removal

NASA Astrophysics Data System (ADS)

Lee, A. A.; Crosato, A.; Omer, A. Y. A.; Bregoli, F.

2017-12-01

The need for accurate and robust predictive methods of assessing fluvial ecosystems is highlighted by the accelerating practice of dam removal. Dam removal can be a restorative measure, but the sudden release of impounded sediment and change in flow regime may negatively impact aquatic biota and their habitat. This study assesses the performance of a quasi-three-dimensional morphodynamic numerical model, coupled with habitat suitability indices, to predict short-term impacts to Chinook salmon (Oncorhynchus tshawytscha) spawning habitat from dam removal. The 2007 removal of Marmot Dam on the Sandy River (Oregon, U.S.A.) is used as a case study. Delft3D-FLOW is employed to simulate changes in river channel topography, sediment composition and hydrodynamic conditions for a 20-kilometer reach of the Sandy River. The transport of non-uniform sediment and three-dimensional flow effects are included in the model. Output parameters such as flow depth, velocity and substrate are processed to evaluate habitat quality in the year following the Marmot Dam removal. Impacts are evaluated across four life-stages of Chinook salmon. As a hindcast analysis, the morphodynamic model sufficiently reproduces the evolution of river morphology at the reach-scale while requiring only a low level of calibration. The model performs well in predicting impacts to fish passage, but carries more uncertainty for developing life stages. By coupling flow-sediment-biota interactions, this method shows strong potential for habitat assessment in unsteady and non-uniform environments. Computation time is a primary constraint, as it limits grid-cell resolution, modelling of suspended sediment and capacity to characterize the sediment grain size distribution. Research on the effects of suspended sediment on habitat quality is ongoing, and further research is recommended for modelling reservoir erosion processes numerically.

MX Siting Investigation Geotechnical Siting Status Report. Volume I.

DTIC Science & Technology

1978-06-21

and have moderate shear strength. GNU. HAl SUNAL, INC ENGINEERING AND GEOPHYSICAL PROPERTIES Int rrniatd.an. ungur . Aluvial Lacustrine /oNan gdotlS t...an unvarnished, active surface of sediment transport gra A53 stream channel and floodplain deposits. A52 - Unconsolidated to poorly consolidated sand...silt, and sandy gravel, with va c.0 A52 surface gravels forming isolated areas of desert pavement. This fan is in vario Cc surface of sediment

Photosynthesis as a Possible Source of Gas Bubbles in Shallow Sandy Coastal Sediments

DTIC Science & Technology

2010-09-30

gas bubbles can be formed when photosynthesis by benthic microalgae causes pore water to become supersaturated with oxygen. OBJECTIVES The...acoustic reflectivity. We also collected sediment samples from the upper few mm of sand to identify the dominant taxa of benthic microalgae present... microalgae in the samples. Following the untimely death of Dr. D.V. Holliday, the remaining team members are sharing the responsibility of analyzing data and

Vegetation Loss Decreases Salt Marsh Denitrification Capacity: Implications for Marsh Erosion.

PubMed

Hinshaw, Sarra E; Tatariw, Corianne; Flournoy, Nikaela; Kleinhuizen, Alice; Taylor, Caitlin; Sobecky, Patricia A; Mortazavi, Behzad

2017-08-01

Salt marshes play a key role in removing excess anthropogenic nitrogen (N) loads to nearshore marine ecosystems through sediment microbial processes such as denitrification. However, in the Gulf of Mexico, the loss of marsh vegetation because of human-driven disturbances such as sea level rise and oil spills can potentially reduce marsh capacity for N removal. To investigate the effect of vegetation loss on ecosystem N removal, we contrasted denitrification capacity in marsh and subtidal sediments impacted by the Deepwater Horizon oil spill using a combination of 29 N 2 and 30 N 2 production (isotope pairing), denitrification potential measurements (acetylene block), and quantitative polymerase chain reaction (qPCR) of functional genes in the denitrification pathway. We found that, on average, denitrification capacity was 4 times higher in vegetated sediments because of a combination of enhanced nitrification and higher organic carbon availability. The abundance of nirS-type denitrifers indicated that marsh vegetation regulates the activity, rather than the abundance, of denitrifier communities. We estimated that marsh sediments remove an average of 3.6 t N km -2 y -1 compared to 0.9 t N km -2 y -1 in unvegetated sediments. Overall, our findings indicate that marsh loss results in a substantial loss of N removal capacity in coastal ecosystems.

Search for Martian fossil communities: Science strategies, sediment sites, and sample handling

NASA Technical Reports Server (NTRS)

Desmarais, David J.

1988-01-01

The strategy for locating and sampling possible fossilized Martian organisms benefits from our experience with fossil microbial ecosystems on Earth. Evidence of early life is typically preserved as stromatolites in carbonates and cherts, and as microfossils in cherts, carbonates and shales. Stromatolites, which are laminated flat or domal structures built by microbial communities, are very likely the oldest and most widespread relics of early life. These communities flourished in supratidal to subtidal coastal benthic environments, wherever sunlight was available and where incoming sediments were insufficient to bury the communities before they became established. A logical site for such communities on Mars might be those areas in an ancient lake bed which were furthest from sediment input, but were still sufficiently shallow to have received sunlight. Therefore, although some sites within Valles Marineris might have contained ponded water, the possibly abundant sediment inputs might have overwhelmed stromatolite-like communities. Localized depressions which acted as catchment basins for ancient branched valley systems might be superior sites. Perhaps such depressions received drainage which, because of the relatively modest water discharges implied for these streams, was relatively low in transported sediment. Multiple streams converging on a single basin might have been able to maintain a shallow water environment for extended periods of time.

Relationship between Enterococcal Levels and Sediment Biofilms at Recreational Beaches in South Florida

PubMed Central

Piggot, Alan M.; Johnson, Sara; Phillips, Matthew C.; Solo-Gabriele, Helena M.

2012-01-01

Enterococci, recommended at the U.S. federal level for monitoring water quality at marine recreational beaches, have been found to reside and grow within beach sands. However, the environmental and ecological factors affecting enterococcal persistence remain poorly understood, making it difficult to determine levels of fecal pollution and assess human health risks. Here we document the presence of enterococci associated with beach sediment biofilms at eight south Florida recreational beaches. Enterococcal levels were highest in supratidal sands, where they displayed a nonlinear, unimodal relationship with extracellular polymeric secretions (EPS), the primary component of biofilms. Enterococcal levels peaked at intermediate levels of EPS, suggesting that biofilms may promote the survival of enterococci but also inhibit enterococci as the biofilm develops within beach sands. Analysis of bacterial community profiles determined by terminal restriction fragment length polymorphisms showed the bacterial communities of supratidal sediments to be significantly different from intertidal and subtidal communities; however, no differences were observed in bacterial community compositions associated with different EPS concentrations. Our results suggest that supratidal sands are a microbiologically unique environment favorable for the incorporation and persistence of enterococci within beach sediment biofilms. PMID:22706061

Earth Observations taken by Expedition 26 crewmember

NASA Image and Video Library

2010-11-27

ISS026-E-005121 (27 Nov. 2010) --- Tidal flats and channels on Long Island, Bahamas are featured in this image photographed by an Expedition 26 crew member on the International Space Station. The islands of the Bahamas in the Caribbean Sea are situated on large depositional platforms (the Great and Little Bahama Banks) composed mainly of carbonate sediments ringed by fringing reefs – the islands themselves are only the parts of the platform currently exposed above sea level. The sediments are formed mostly from the skeletal remains of organisms settling to the sea floor; over geologic time, these sediments will consolidate to form carbonate sedimentary rocks such as limestone. This detailed photograph provides a view of tidal flats and tidal channels near Sandy Cay on the western side of Long Island, located along the eastern margin of the Great Bahama Bank. The continually exposed parts of the island have a brown coloration in the image, a result of soil formation and vegetation growth (left). To the north of Sandy Cay an off-white tidal flat composed of carbonate sediments is visible; light blue-green regions indicate shallow water on the tidal flat. Tidal flow of seawater is concentrated through gaps in the anchored land surface, leading to formation of relatively deep tidal channels that cut into the sediments of the tidal flat. The channels, and areas to the south of the island, have a vivid blue coloration that provides a clear indication of deeper water (center).

Fidelity of life and death molluscan assemblages from carbonate tidal flats in the Persian (Arabian) Gulf

NASA Astrophysics Data System (ADS)

García-Ramos, Diego A.; Albano, Paolo G.; Harzhauser, Mathias; Piller, Werner E.; Zuschin, Martin

2016-04-01

Live-dead (LD) studies aim to help understand how faithfully fossil assemblages can be used to quantitatively infer the structure of the original living communities that generated them. To this purpose, LD comparisons have been conducted in different terrestrial and aquatic environments to assess how environment-specific differences in quality and intensity of taphonomic factors affect LD fidelity. In sub-tropical and tropical settings, most LD studies have focused on hard substrates or seagrass bottoms. Here we present results on molluscan assemblages from soft carbonate sediments in tidal flats of the Persian (Arabian) Gulf (Indo-West Pacific biogeographic province). We analyzed a total of 7193 mollusks collected from six sites comprising time-averaged death assemblages (DAs) and snapshot living assemblages (LAs). All analyses were performed at site and at habitat scales after correcting for sample-size differences. We found a good match in proportional abundance and a notable mismatch in species composition. In fact, species richness in DAs is 6 times larger than in LAs at site scale, and 4 times at habitat scale. Additionally, we found a good fidelity of evenness, and rank abundance of feeding guilds. Other studies have shown that molluscan DAs from subtidal carbonate environments can display lower time-averaging than those from siliciclastic environments due to high rates of shell loss to bioerosion and dissolution. For our case study of tidal flat carbonate settings, we interpret that despite temporal autocorrelation (good fidelity of proportional abundance), substantial differences in species richness and composition can be explained by early cementation, lateral mixing, intense bioturbation and moderate sedimentation rates. Our results suggest that tidal flat carbonate environments can potentially lead to a wider window of time-averaging in comparison with subtidal carbonate settings.

Structuring factors and recent changes in subtidal macrozoobenthic communities of a coastal lagoon, Arcachon Bay (France)

NASA Astrophysics Data System (ADS)

Blanchet, Hugues; de Montaudouin, Xavier; Chardy, Pierre; Bachelet, Guy

2005-09-01

Fourteen years after a previous investigation in Arcachon Bay (SW France), the quantitative distribution of subtidal macrozoobenthic communities was assessed in 2002 through a stratified sampling strategy involving a larger number of stations (89 vs. 18) than in 1988. A total of 226 taxa were recorded. Cluster Analysis and Correspondence Analysis identified nine station groups corresponding to benthic faunal assemblages and their characteristic species. Multiple Discriminant Analysis showed that the main environmental factors influencing the distribution of faunal assemblages were sediment parameters and distance from the ocean. Depth was a minor structuring factor. At the scale of the lagoon, biogenic structures such as Zostera marina beds, Crepidula fornicata-dominated bottoms or dead oyster shell bottoms did not display any particular assemblage of infauna. Comparison with previous quantitative data from the 1988 survey provided more precision on the distribution of benthic assemblages and revealed community changes at a 14-year scale. These modifications reflected a general increase of silt and clay content in the sediment in the internal parts of channels, inducing community change. These changes can be correlated to the recent first signs of a moderate eutrophication process which have appeared, since 1988, through the development of green macroalgae in some parts of the lagoon. This trend was enhanced in transverse channels with reduced hydrodynamics and led to muddy areas where green macroalgae tended to accumulate. Locally, the dredging of sandbanks induced stronger currents and allowed the marine influence to occur, and also induced community change. These observations confirm that surveys of macrobenthic communities are useful tools to assess coastal ecosystem change even in moderately disturbed environments.

Non-cohesive silt turbidity current flow processes; insights from proximal sandy-silt and silty-sand turbidites, Fiordland, New Zealand

NASA Astrophysics Data System (ADS)

Strachan, Lorna J.; Bostock, Helen C.; Barnes, Philip M.; Neil, Helen L.; Gosling, Matthew

2016-08-01

Silt-rich turbidites are commonly interpreted as distal marine deposits. They are associated with interlaminated clay and silt deposition from the upper and rear portions of turbidity currents. Here, multibeam bathymetry and shallow sediment core data from the intra-slope Secretary Basin, Fiordland, New Zealand, located < 10 km from shore, are used to describe a suite of late Holocene proximal sandy-silt and silty-sand turbidites that contain negligible clay and a wide variety of vertical grading patterns. The steep, rugged catchment to the Secretary Basin is dominated by a complex tributary turbidite channel network that feeds the low gradient Secretary Basin floor intra-slope lobe. Sediment core T49 is located within the lobe and positioned between shallow channels that are prone to deposition from decelerating, silty-sand and sandy-silt turbidity currents. The wide variety of sedimentary structures and vertical grading patterns, dominated by inversely graded beds, implies a range of non-cohesive flow processes, with deposition from multiphase, mixed mode (turbulent and laminar) flows that have undergone a variety of up-dip flow transformations. Most flows were initially erosive followed by deposition of partitioned 2- or 3- phase mixed mode flows that include high-density transitional and laminar flows that can be fore- or after-runners to low-density turbulent flow sections. Turbulence is inferred to have been suppressed in high-density flows by increasing flow concentration of both sands and silts. The very fine and fine sand modal grain sizes of sandy-silt and silty-sand turbidites are significantly coarser than classical abyssal plain silt turbidites and are generally coarser than overbank silt turbidites. While the low percentage of clays within Secretary Basin sandy-silt and silty-sand turbidites represents a fundamental difference between these and other silt and mud turbidites, we suggest these beds represent a previously undescribed suite of proximal continental slope deposits.

PAH effects on meio- and microbial benthic communities strongly depend on bioavailability.

PubMed

Lindgren, J Fredrik; Hassellöv, Ida-Maja; Dahllöf, Ingela

2014-01-01

The effects of anthropogenic pollutants in dissimilar habitats can vary depending on differences in bioavailability. The factors determining bioavailability are not yet fully understood. This study was performed to evaluate whether analysis of total PAH concentrations in sediments is a satisfactory measurement to indicate environmental effects or if bioavailability is needed to be taken into account. We have here performed a 60-day experiment, where nominal PAH concentrations of 1,300 μg/kg sediment were added to three different marine sediments. Meiofaunal and microbial communities were analyzed for alterations in community response at 30 and 60 days. Results showed that bioavailability of PAHs varied between the three different sediments. Nonetheless, the petroleum addition gave rise to significant negative effects on all three sediments at both time points. The two direct measurements of toxicity on the microbial community, potential nitrification and denitrification, displayed a lower effect of the PAH addition in the muddy sediment at both time points, compared to the other two sediment types. No effects were seen in the analysis of meiofaunal community structure. Measurements of PAH bioavailability in the three sediment types concurred with the results from the microbial community, revealing a lower bioavailability in the muddy sediment compared to the other two sediment types, 34% compared to sandy and 18% compared to organic at day 0. At day 60 it was 61% lower compared to sandy and 20% lower compared to organic. The negative effects of the PAH addition on the microbial nitrogen cycle were in six out of eight cases best correlated to the amount of alkylated bioavailable PAH in the sediments, and thus microbial nitrogen cycle is a possible good indicator for assessing PAH-induced stress. The results presented here have implications for risk analysis studies of petroleum-contaminated marine sediments; consequently, sediment characteristics and its effects on bioavailability are important to include. In addition, these results add to the understanding that bioavailability measurements of PAHs are a more correct assessment compared to measurements of total PAH concentrations, and need to be included when estimating effects of PAHs in marine benthic communities. Copyright © 2013 Elsevier B.V. All rights reserved.

Geophysical and sampling data from the inner continental shelf: Duxbury to Hull, Massachusetts

USGS Publications Warehouse

Barnhardt, Walter A.; Ackerman, Seth D.; Andrews, Brian D.; Baldwin, Wayne E.

2010-01-01

The U.S. Geological Survey (USGS) and the Massachusetts Office of Coastal Zone Management (CZM) have cooperated to map approximately 200 km² of the Massachusetts inner continental shelf between Duxbury and Hull. This report contains geophysical and geological data collected by the USGS on three cruises between 2006 and 2007. These USGS data are supplemented with a National Oceanic and Atmospheric Administration (NOAA) hydrographic survey conducted in 2003 to update navigation charts. The geophysical data include (1) swath bathymetry from interferometric sonar and multibeam echosounders, (2) acoustic backscatter from sidescan sonar and multibeam echosounders, and (3) subsurface stratigraphy and structure from seismic-reflection profilers. The geological data include sediment samples, seafloor photographs, and bottom videos. These spatial data support research on the influence sea-level change and sediment supply have on coastal evolution, and on efforts to understand the type, distribution, and quality of subtidal marine habitats in the Massachusetts coastal ocean.

What Role do Nor'Easters have on the Jamaica Bay Wetlands Sediment Budget?

NASA Astrophysics Data System (ADS)

Clarke, R. C.; Bentley, S. J.; Wang, H.; Smith, J.

2017-12-01

The wetlands of Jamaica Bay, located on the outskirts of Queens, New York, have lost over half their surface area in the last 50 years due both anthropogenic and natural causes, including channel dredging, urban drainage construction, and greater tidal amplitudes partially due to rising local sea levels. Superstorm Sandy made landfall in 2014 as a powerful coastal geomorphic agent, highlighting the vulnerability of that region to large cyclonic storms that are more commonly encountered along coastal reaches of southeastern North America. After this event, research aimed at quantifying the geomorphic impact of Superstorm Sandy and to evaluate the record of past documented major winter storms on Jamaica Bay's wetlands. 12 sediment cores were collected from the surface of remaining wetlands in August 2014 by the USGS Wetland and Aquatic Research Center; the cores have been analyzed for Pb-210/Cs-137 geochronology, organic content, and water content to establish chronology of mineral sediment supply to the wetlands over the past 120 years. Most cores were found to be organic-rich, marked with periodic cm-scale beds with increased mineral content. Historic storm data, dating as far back as the late 1800's, were used to identify hurricanes and major winter storms determined by the National Weather Service passing within 100 km of the study area. Likely storm-event deposits in each core were identified as layers with mineral content higher than the core mean plus one standard deviation, and were matched to historic events via radioisotope geochronology, incorporating age-model uncertainty. Overall, 22 out of the 35 defined storm layers match the timing of historic strong storms (within uncertainty ranging from 2 to 5 years) from 1894 to Superstorm Sandy in 2014. Our findings show that over multidecadal timescales, nor'easters and winter storms play a role in the vertical accretion of sediment in the Jamaica Bay wetlands, but are substantially less important than sediment delivery under typical tidal conditions. Event deposits from tropical cyclones are also present, but less common than those produced by frontal storms.

Outcrop-scale acoustic facies analysis and latest Quaternary development of Hueneme and Dume submarine fans, offshore California

USGS Publications Warehouse

Piper, D.J.W.; Hiscott, R.N.; Normark, W.R.

1999-01-01

The uppermost Quaternary deposits of the Hueneme and Dume submarine fans in the Santa Monica Basin have been investigated using a closed-spaced grid of boomer seismic-reflection profiles, which give vertical resolution of a few tens of centimetres with acoustic penetration to 50 m. Acoustic facies integrated with geometry define six architectural elements, some with discrete subelements that are of a scale that can be recognized in outcrops of ancient turbidite systems. In the Santa Monica Basin, the relationship of these elements to fan morphology, stratigraphy and sediment source is precisely known. The width of upper Hueneme fan valley has been reduced from 5 km since the last glacial maximum to 1 km at present by construction of laterally confined sandy levees within the main valley. The middle fan comprises three main subelements: thick sand deposits at the termination of the fan valley, low-gradient sandy lobes typically 5 km long and < 10 m thick, and scoured lobes formed of alternating sand and mud beds with many erosional depressions. The site of thickest lobe sediment accumulation shifts through time, with each sand bed deposited in a previous bathymetric low (i.e. compensation cycles). The lower fan and basin plain consists of sheet-like alternations of sand and mud with shallow channels and lenses. Variations in the rate of late Quaternary sea level rise initiated changes in sediment facies distribution. At lowstand, and during the approximately 11 ka stillstand in sea level, the Hueneme Fan was fed largely by hyperpycnal flow from the Santa Clara River delta, depositing high sediment waves on the right hand levee and thick sandy lobes on the middle fan. At highstand of sea level, most turbidity currents were generated by failure of silty prodelta muds. In contrast, the smaller Dume Fan was apparently always fed from littoral drift of sand through a single-canyon point source.

Sedimentary facies and Holocene depositional processes of Laura Island, Majuro Atoll

NASA Astrophysics Data System (ADS)

Yasukochi, Toru; Kayanne, Hajime; Yamaguchi, Toru; Yamano, Hiroya

2014-10-01

The depositional processes that formed Laura Island, Majuro Atoll, Marshall Islands, were reconstructed based on a facies analysis of island sediments and spine ratios, and radiocarbon ages of foraminifera. Sedimentary facies were analyzed from trenches and drill cores excavated on the island and its adjacent reef flat. Depositional ages were obtained using benthic foraminifera (Calcarina) whose spines had not been abraded. The facies were classified into two types: gravelly and sandy. The initial sediments of these sites consisted of gravelly facies in the lower horizon and sandy facies in the upper horizon. Their ages were approximately 2000 cal BP and coincident with the onset of a 1.1-m decline in regional relative sea level, which enabled deposition of the gravelly facies. Half of the sand fraction of the sediment was composed of larger benthic foraminifera. The spine ratio showed that their supply source on the reef flat was located oceanside of the island. The supply source appears to have been caused by the relative sea-level fall. This indicates that the studied island was formed by a relative reduction in wave energy and enhanced foraminiferal supply, both of which were triggered by the late Holocene relative sea-level fall.

The application of microtextural and heavy mineral analysis to discriminate between storm and tsunami deposits

USGS Publications Warehouse

Costa, Pedro J.M.; Gelfenbaum, Guy R.; Dawson, Sue; La selle, Seanpaul; Milne, F; Cascalho, J.; Ponte Lira, C.; Andrade, C.; Freitas, M. C.; Jaffe, Bruce E.

2017-01-01

Recent work has applied microtextural and heavy mineral analyses to sandy storm and tsunami deposits from Portugal, Scotland, Indonesia and the USA. We looked at the interpretation of microtextural imagery (scanning electron microscopy) of quartz grains and heavy mineral compositions. We consider inundation events of different chronologies and sources (the AD 1755 Lisbon and 2004 Indian Ocean tsunamis, the Great Storm of 11 January 2005 in Scotland, and Hurricane Sandy in 2012) that affected contrasting coastal and hinterland settings with different regional oceanographic conditions. Storm and tsunami deposits were examined along with potential source sediments (alluvial, beach, dune and nearshore sediments) to determine provenance.Results suggest that tsunami deposits typically exhibit a significant spatial variation in grain sizes, microtextures and heavy minerals. Storm deposits show less variability, especially in vertical profiles. Tsunami and storm quartz grains had more percussion marks and fresh surfaces compared to potential source material. Moreover, in the studied cases, tsunami samples had fewer fresh surfaces than storm deposits.Heavy mineral assemblages are typically site-specific. The concentration of heavy minerals decreases upwards in tsunamigenic units, whereas storm sediments show cyclic concentrations of heavy minerals, reflected in the laminations observed macroscopically in the deposits.

Geohydrology, water quality, and conceptual model of the hydrologic system Saco Landfill area, Saco, Maine

USGS Publications Warehouse

Nielsen, M.G.; Stone, J.R.; Hansen, B.P.; Nielsen, J.P.

1995-01-01

A geohydrologic study of the Saco Municipal Landfill in Saco, Maine, was done during 1993-94 to provide a preliminary interpretation of the geology and hydrology needed to guide additional studies at the landfill as part of the Superfund Program. The Saco Landfill, which was active from the early 1960's until 1986, includes three disposal areas on a-90-acre parcel. Sandy Brook, a small perennial stream, flows from north to south through the land- fill between the disposal areas. Discharge of leachate from the disposal areas to aquifers and streams has been documented since 1974. The landfill was declared a Superfund site in 1990 by the U.S. Environmental Protection Agency. Multiple lines of evidence are used in this study to indicate areas of ground-water contamination and sources of water flow in Sandy Brook. The geohydrologic system on the east side of Sandy Brook consists of an upper water-table aquifer and a lower aquifer, separated by a thick sequence of glaciomarine silt and clay. Depths to bedrock range from 60 to more than 200 ft (feet), on the basis of data from seismic-refraction studies and drilling. The upper aquifer, which is generally less than 15 ft thick, consists of fine- to medium-grained sand deposited in a shallow postglacial marine environment. The lower aquifer, which was deposited as a series of glaciomarine fans, contains two sediment types: well-sorted sand *and gravel and unsorted sediments called diamict sediments. East of Sandy Brook, the thickness of the lower aquifer ranges from 25 to 100 ft, based on drilling at the landfill. The glaciomarine silts and clays (known as the presumpscot Formation) range from 50 to more than 100 ft thick. West of Sandy Brook, the glaciomarine silt and clay is largely absent, and fractured bedrock is very close to land surface under one of the disposal areas in the northwestern part of the property. The lower aquifer is unconfined in the southwestern side of the study area; bedrock slopes towards the south, and the aquifer thickens to 100 ft at the southwestern end of the study area. Preliminary estimates of mean annual streamflow in Sandy Brook, based on a partial year of continuous record, indicate that runoff increases from approximately 2.1 ft3/s (cubic feet per second) upstream from the landfill to 2.7 ft3/s downstream from the landfill, although the drainage area down- stream is only 11 percent greater than the drainage area upstream. A water-budget estimate based on available streamflow and climatic data indicates that Sandy Brook below the landfill gains about 80 million gallons per year from sources outside the drainage-basin boundary. Possible sources include the lower aquifer north or west of the landfill area and the fractured bedrock northwest of Sandy Brook. Specific conductance of water in Sandy Brook increases downstream from the landfill. In September 1993, specific conductance was 184 liS/cm (microsiemens per centimeter at 25 degrees Celsius) upstream from the landfill and 496 uS/cm downstream from the landfill. Continuous monitoring of specific conductance in Sandy Brook shows that the downstream increase is less during periods of stormflow because of dilution. Electromagnetic terrain-conductivity surveys, results of ground-water chemical analyses, and changes in streamwater quality have been used to identify areas of likely ground-water contamination. The specific conductance of ground water exceeds 2,000 uS/cm in some areas near the landfills. This compares to specific conductances of less than 200 uS/cm in water from most shallow wells that are considered to represent background water quality. Ground water in the upper aquifer east of Sandy Brook and in the lower aquifer west of Sandy Brook has been affected by leachate flowing from the landfill areas. The extent of contamination in bedrock, if any, is unknown. Water levels measured in 16 wells were used to help determine the direction of ground-water flow. The electromagnetic terrain-conduct

Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough

USGS Publications Warehouse

Santamarina, J.C.; Dai, Shifeng; Terzariol, M.; Jang, Jeonghwan; Waite, William F.; Winters, William J.; Nagao, J.; Yoneda, J.; Konno, Y.; Fujii, T.; Suzuki, K.

2015-01-01

Natural hydrate-bearing sediments from the Nankai Trough, offshore Japan, were studied using the Pressure Core Characterization Tools (PCCTs) to obtain geomechanical, hydrological, electrical, and biological properties under in situ pressure, temperature, and restored effective stress conditions. Measurement results, combined with index-property data and analytical physics-based models, provide unique insight into hydrate-bearing sediments in situ. Tested cores contain some silty-sands, but are predominantly sandy- and clayey-silts. Hydrate saturations Sh range from 0.15 to 0.74, with significant concentrations in the silty-sands. Wave velocity and flexible-wall permeameter measurements on never-depressurized pressure-core sediments suggest hydrates in the coarser-grained zones, the silty-sands where Sh exceeds 0.4, contribute to soil-skeletal stability and are load-bearing. In the sandy- and clayey-silts, where Sh < 0.4, the state of effective stress and stress history are significant factors determining sediment stiffness. Controlled depressurization tests show that hydrate dissociation occurs too quickly to maintain thermodynamic equilibrium, and pressure–temperature conditions track the hydrate stability boundary in pure-water, rather than that in seawater, in spite of both the in situ pore water and the water used to maintain specimen pore pressure prior to dissociation being saline. Hydrate dissociation accompanied with fines migration caused up to 2.4% vertical strain contraction. The first-ever direct shear measurements on never-depressurized pressure-core specimens show hydrate-bearing sediments have higher sediment strength and peak friction angle than post-dissociation sediments, but the residual friction angle remains the same in both cases. Permeability measurements made before and after hydrate dissociation demonstrate that water permeability increases after dissociation, but the gain is limited by the transition from hydrate saturation before dissociation to gas saturation after dissociation. In a proof-of-concept study, sediment microbial communities were successfully extracted and stored under high-pressure, anoxic conditions. Depressurized samples of these extractions were incubated in air, where microbes exhibited temperature-dependent growth rates.

Superstorm Sandy-related Morphologic and Sedimentologic Changes in an Estuarine System: Barnegat Bay-Little Egg Harbor Estuary, New Jersey

NASA Astrophysics Data System (ADS)

Miselis, J. L.; Ganju, N. K.; Navoy, A.; Nicholson, R.; Andrews, B.

2013-12-01

Despite the well-recognized ecological importance of back-barrier estuaries, the role of storms in their geomorphic evolution is poorly understood. Moreover, the focus of storm impact assessments is often the ocean shorelines of barrier islands rather than the exchange of sediment from barrier to estuary. In order to better understand and ultimately predict short-term morphologic and sedimentologic changes in coastal systems, a comprehensive research approach is required but is often difficult to achieve given the diversity of data required. An opportunity to use such an approach in assessing the storm-response of a barrier-estuary system occurred when Superstorm Sandy made landfall near Atlantic City, New Jersey on 29 October 2012. Since 2011, the US Geological Survey has been investigating water circulation and water-quality degradation in Barnegat Bay-Little Egg Harbor (BBLEH) Estuary, the southern end of which is approximately 25 kilometers north of the landfall location. This effort includes shallow-water geophysical surveys to map the bathymetry and sediment distribution within BBLEH, airborne topo-bathymetric lidar surveys for mapping the shallow shoals that border the estuary, and sediment sampling, all of which have provided a recent picture of the pre-storm estuarine geomorphology. We combined these pre-storm data with similar post-storm data from the estuary and pre- and post-storm topographic data from the ocean shoreline of the barrier island to begin to understand the response of the barrier-estuary system. Breaches in the barrier island resulted in water exchange between the estuary and the ocean, briefly reducing residence times in the northern part of the estuary until the breaches were closed. Few morphologic changes in water depths greater than 1.5 m were noted. However, morphologic changes observed in shallower depths along the eastern shoreline of the estuary are likely related to overwash processes. In general, surficial estuarine sediments were coarser post-Sandy, but, especially where observed along the western shoreline, it is unclear if the change is related to deposition of new sediment or winnowing of fine sediment. Further analysis will provide insight into whether the geometry of the barrier island and estuary influenced the morphologic and sedimentologic system response in BBLEH.

Quaternary Turbidite Sedimentation in the Moresby Trough, Preliminary Observations from the Papua New Guinea S2S Study Area

NASA Astrophysics Data System (ADS)

Bentley, S. J.; Muhammad, Z.; Dickens, J.; Droxler, A.; Peterson, L.; Opdyke, B.

2004-12-01

Multicores and jumbo piston cores were collected from the Moresby Trough from the R/V Melville in March-April 204 to study patterns of off-shelf sediment flux from the Gulf of Papua to the deep sea over Pleistocene-Holocene timescales. The Moresby Trough represents the primary deep-sea sediment conduit linking the Source to Sink Gulf of Papua study area to the north with the Coral Sea Basin to the south. Core locations were navigated from the surface using dynamic positioning and multibeam bathymetric mosaics collected during the cruise. Selected cores have been analyzed using a multi-sensor core logger, X-radiography, granulometry, and Pb-210 geochronology. Most piston cores collected from the Moresby Trough contain abundant mafic sandy turbidites overlain by fine-grained hemipelagic deposits 1-2 m thick. X-radiographs of multicores reveal mostly bioturbated hemipelagics. However, one core, MV25-0403-24MC, was collected from the axis of a primary channel, and contains at least two fine-grained turbidites within the upper 0.5 m of sediment. The uppermost turbidite contains low but uniform activities of excess Pb-210, and may have been 15-20 cm thick at the time of deposition (i.e., before subsequent disruption by bioturbation), based on fabric and radiochemical evidence. Application of a simple box-model for physical mixing (i.e., during the flow) and subsequent decay suggests that the uppermost turbidite was deposited 70-120 years before present. Bioturbation has since reworked about 60% of the bed, suggesting that such beds will only escape destruction by bioturbation if they are > 10 cm thick, and are deposited more frequently than once per century. Based on these observations, we suggest that gravity flows are presently active in the Moresby trough, and may account for a significant fraction of the hemipelagic drape present in channel systems. However, fabric evidence for these thin, fine-grained beds may be obscured by subsequent bioturbation. Also, at some point in the past, possibly at the onset of the Holocene Transgression, the character of sediment flux to the Moresby Trough shifted from sandy mafic-rich sandy turbidity currents to much finer sediments, delivered downslope by both benthic flows and vertical flux through the water column.

Marine habitat mapping of the Milford Haven Waterway, Wales, UK: Comparison of facies mapping and EUNIS classification for monitoring sediment habitats in an industrialized estuary

NASA Astrophysics Data System (ADS)

Carey, Drew A.; Hayn, Melanie; Germano, Joseph D.; Little, David I.; Bullimore, Blaise

2015-06-01

A detailed map and dataset of sedimentary habitats of the Milford Haven Waterway (MHW) was compiled for the Milford Haven Waterway Environmental Surveillance Group (MHWESG) from seafloor images collected in May, 2012 using sediment-profile and plan-view imaging (SPI/PV) survey techniques. This is the most comprehensive synoptic assessment of sediment distribution and benthic habitat composition available for the MHW, with 559 stations covering over 40 km2 of subtidal habitats. In the context of the MHW, an interpretative framework was developed that classified each station within a 'facies' that included information on the location within the waterway and inferred sedimentary and biological processes. The facies approach provides critical information on landscape-scale habitats including relative location and inferred sediment transport processes and can be used to direct future monitoring activities within the MHW and to predict areas of greatest potential risk from contaminant transport. Intertidal sediment 'facies' maps have been compiled in the past for MHW; this approach was expanded to map the subtidal portions of the waterway. Because sediment facies can be projected over larger areas than individual samples (due to assumptions based on physiography, or landforms) they represent an observational model of the distribution of sediments in an estuary. This model can be tested over time and space through comparison with additional past or future sample results. This approach provides a means to evaluate stability or change in the physical and biological conditions of the estuarine system. Initial comparison with past results for intertidal facies mapping and grain size analysis from grab samples showed remarkable stability over time for the MHW. The results of the SPI/PV mapping effort were cross-walked to the European Nature Information System (EUNIS) classification to provide a comparison of locally derived habitat mapping with European-standard habitat mapping. Cross-walk was conducted by assigning each facies (or group of facies) to a EUNIS habitat (Levels 3 or 5) and compiling maps comparing facies distribution with EUNIS habitat distribution. The facies approach provides critical information on landscape-scale habitats including relative location and inferred sediment transport processes. The SPI/PV approach cannot consistently identify key species contained within the EUNIS Level 5 Habitats. For regional planning and monitoring efforts, a combination of EUNIS classification and facies description provides the greatest flexibility for management of dynamic soft-bottom habitats in coastal estuaries. The combined approach can be used to generate and test hypotheses of linkages between biological characteristics (EUNIS) and physical characteristics (facies). This approach is practical if a robust cross-walk methodology is developed to utilize both classification approaches. SPI/PV technology can be an effective rapid ground truth method for refining marine habitat maps based on predictive models.

Removal Efficiencies and Attachment Coefficients for Cryptosporidium in Sandy Alluvial Riverbank Sediment

EPA Science Inventory

Riverbank filtration has been shown to be effective at removing viable Cryptosporidium parvum oocysts and, therefore, drinking water systems that employ riverbank filtration may receive additional treatment credits beyond that which they can obtain using traditional engineering a...

Biogeochemical Controls on Biodegradation of MC252 Oil:Sand Aggregates on a Rapidly Eroding Coastal Headland Beach

NASA Astrophysics Data System (ADS)

Pardue, J.; Elango, V.; Urbano, M.; Lemelle, K.

2012-12-01

The research described below was conducted on Fourchon Beach, a coastal headland consisting of nine miles of fairly pristine sandy beaches and dunes, backed by wetlands and tidal channels, located between Belle Pass tidal inlet on the west and Elmer's Island on the east in Lafourche Parish, Louisiana. MC252 oil first arrived in large quantities on Fourchon Beach on or around May 20, 2010. A unique oil form created under these conditions was an aggregate of sand and emulsified oil, typically 0.1-10 cm in diameter, termed small surface residue balls (SSRBs). The work from this project made critical measurements on the factors controlling biodegradability of these SSRB aggregates. SSRB aggregates were sampled across transects perpendicular to the beach from the intertidal to the supratidal. Areas in the supratidal that were sampled initially were set aside for research purposes and not altered by any clean-up activities. Chemical composition of SSRBs was measured including concentrations of n-alkanes, PAHs, hopanes, nutrients (nitrate, nitrite, ammonium and orthophosphate measured on water extracts of SSRBs), and electron acceptor concentrations (O2 microprofiles measured on intact SSRBs and sulfate). Physical characterization of the SSRBs including length and area dimensions, mass, density, porosity, moisture content, and salinity using standard methods. Microbial characterization of SSRBs was also conducted using denaturing gradient gel electrophoresis and sequencing of dominant bands. SSRBs were sampled from various locations across the beach profile deposited by 2 significant tropical events in 2010; Hurricane Alex and TS Bonnie, and one event in 2011, TS Lee. Sampling focused on comparing and contrasting impacts of biogeochemistry on weathering of oil stranded in three beach microenvironments; supratidal surface; subtidal subsurface which is permanently inundated and intertidal subsurface samples which are intermittently inundated. The three types of oil are dramatically different in appearance and have a distinctive chemical signature indicative of different rates of weathering. Supratidal surface samples were depleted in n-alkanes and lower-molecular weight PAHs. Geochemically, aggregates located in these environments had low salinities (1.3-1.5 ppt), O2 at near saturation throughout the aggregates and nutrient concentrations (N and P) significantly lower than SSRBs deposited in the intertidal and subtidal. Intertidal and subtidal subsurface oil samples were characterized by elevated nutrient concentrations and salinities consistent with regular seawater inundation. Complete inundation leads to O2 consumption in the aggregates after several days. Despite the presence of elevated nutrients, PAHs and n-alkanes were comparatively unweathered in the subtidal subsurface samples consistent with O2 limitations. Sequences of known PAH degraders were isolated from the supratidal and intertidal aggregates. The results to be presented support the hypothesis that SSRBs deposited at different locations on the beach have different biogeochemical characteristics . These characteristics are due, in part, to their location on the landscape.

Depositional framework and sequence stratigraphic aspects of the Coniacian Santonian mixed siliciclastic/carbonate Matulla sediments in Nezzazat and Ekma blocks, Gulf of Suez, Egypt

NASA Astrophysics Data System (ADS)

El-Azabi, M. H.; El-Araby, A.

2007-04-01

Superb outcrops of mixed siliciclastic/carbonate rocks mark the Coniacian-Santonian Matulla Formation exposed in Nezzazat and Ekma blocks, west central Sinai. They are built up of various lithofacies that reflect minor fluctuations in relative sea-level from lower intertidal to slightly deep subtidal settings. Relying on the facies characteristics and stratal geometries, the siliciclastic rocks are divided into seven depositional facies, including beach foreshore laminated sands, upper shoreface cross-bedded sandstone, lower shoreface massive bioturbated and wave-rippled sandstones, shallow subtidal siltstone and deep subtidal shale/claystone. The carbonate rocks comprise lower intertidal lime-mudstone, floatstone and dolostone, shallow subtidal skeletal shoal of oyster rudstone/bioclastic grainstone, and shoal margin packstone. Oolitic grain-ironstone and ferribands are partially intervened the facies types. Deposition has taken place under varied conditions of restricted, partly open marine circulation, low to high wave energy and normal to raised salinity during alternating periods of abundant and ceased clastic supply. The facies types are arranged into asymmetric upward-shallowing cycles that record multiple small-scale transgressive-regressive events. Lime-mudstone and sandstone normally terminate the regressive events. Four sequence boundaries marking regional relative sea-level falls divide the Matulla Formation into three stratigraphic units. These boundaries are Turonian/Coniacian, intra-Coniacian, Coniacian/Santonian and Santonian/Campanian. They do not fit with those sequence boundaries proposed in Haq et al.'s global eustatic curves (1988) except for the sea-level fall associated with the intra-Coniacian boundary. Other sequence boundaries have resulted from regional tectonic impact of the Syrian Arc Fold System that has been initiated in north Egypt during the Latest Turonian-Coniacian. These boundaries enclose three well-defined 3rd order depositional sequences; their enclosing shallowing-upward cycles (i.e. parasequences) record the 4th order relative sea-level fluctuations. 34 and 20 parasequence sets, in the order of a few meters to tens of meters thick, mark the Matulla sequences in Nezzazat and Ekma blocks respectively. Each sequence shows an initial phase of rapid sea-level rise with retrogradational sets, followed by lowering sea-level and progradation/aggradation of the parasequence sets. The transgressive deposits display predominance of deep subtidal lagoonal facies, while highstand deposits show an increase in siliciclastic and carbonate facies with the progressive decrease of lagoonal facies. The sedimentary patterns and environments suggest that the regional, partly eustatic sea-level (i.e. intra-Coniacian) changes controlled the overall architecture of the sequence distribution, whereas changes in the clastic input controlled the variations in facies associations within each depositional sequence.

Assessing the impact of Hurricanes Irene and Sandy on the morphology and modern sediment thickness on the inner continental shelf offshore of Fire Island, New York

USGS Publications Warehouse

Schwab, William C.; Baldwin, Wayne E.; Denny, Jane F.

2016-01-15

This report documents the changes in seabed morphology and modern sediment thickness detected on the inner continental shelf offshore of Fire Island, New York, before and after Hurricanes Irene and Sandy made landfall. Comparison of acoustic backscatter imagery, seismic-reflection profiles, and bathymetry collected in 2011 and in 2014 show that sedimentary structures and depositional patterns moved alongshore to the southwest in water depths up to 30 meters during the 3-year period. The measured lateral offset distances range between about 1 and 450 meters with a mean of 20 meters. The mean distances computed indicate that change tended to decrease with increasing water depth. Comparison of isopach maps of modern sediment thickness show that a series of shoreface-attached sand ridges, which are the dominant sedimentary structures offshore of Fire Island, migrated toward the southwest because of erosion of the ridge crests and northeast-facing flanks as well as deposition on the southwest-facing flanks and in troughs between individual ridges. Statistics computed suggest that the modern sediment volume across the about 81 square kilometers of common sea floor mapped in both surveys decreased by 2.8 million cubic meters, which is a mean change of –0.03 meters, which is smaller than the resolution limit of the mapping systems used.

Occurrence and behavior of butyltins in intertidal and shallow subtidal surface sediments of an estuarine beach under different sampling conditions

NASA Astrophysics Data System (ADS)

Santos, Dayana Moscardi dos; Sant'Anna, Bruno Sampaio; Sandron, Daniela Corsino; Cardoso de Souza, Sara; Cristale, Joyce; Marchi, Mary Rosa Rodrigues de; Turra, Alexander

2010-07-01

Contamination by butyltin compounds (BTs) has been reported in estuarine environments worldwide, with serious impacts on the biota of these areas. Considering that BTs can be degraded by varying environmental conditions such as incident light and salinity, the short-term variations in such factors may lead to inaccurate estimates of BTs concentrations in nature. Therefore, the present study aimed to evaluate the possibility that measurements of BTs in estuarine sediments are influenced by different sampling conditions, including period of the day (day or night), tidal zone (intertidal or subtidal), and tides (high or low). The study area is located on the Brazilian southeastern coast, São Vicente Estuary, at Pescadores Beach, where BT contamination was previously detected. Three replicate samples of surface sediment were collected randomly in each combination of period of the day, tidal zone, and tide condition, from three subareas along the beach, totaling 72 samples. BTs were analyzed by GC-PFPD using a tin filter and a VF-5 column, by means of a validated method. The concentrations of tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) ranged from undetectable to 161 ng Sn g -1 (d.w.). In most samples (71%), only MBT was quantifiable, whereas TBTs were measured in only 14, suggesting either an old contamination or rapid degradation processes. DBT was found in 27 samples, but could be quantified in only one. MBT concentrations did not differ significantly with time of day, zones, or tide conditions. DBT and TBT could not be compared under all these environmental conditions, because only a few samples were above the quantification limit. Pooled samples of TBT did not reveal any difference between day and night. These results indicated that, in assessing contamination by butyltin compounds, surface-sediment samples can be collected in any environmental conditions. However, the wide variation of BTs concentrations in the study area, i.e., over a very small geographic scale, illustrates the need for representative hierarchical and composite sampling designs that are compatible with the multiscalar temporal and spatial variability common to most marine systems. The use of such sampling designs will be necessary for future attempts to quantitatively evaluate and monitor the occurrence and impact of these compounds in nature.

Facies changes in the Cenomanian (Cretaceous) of the northwestern Elbe Valley near Dresden (Saxony, Germany)

NASA Astrophysics Data System (ADS)

Tröger, Karl-Armin

2017-03-01

The Upper Cretaceous of the Elbe Valley in Saxony and the erosion outliers west of it mark an Upper Cretaceous NW-SE-running strait between the Westsudetic Island in the NE and the Mid-European Island to the west. This street connected the NW-German-Polish Basin in the north and the Bohemian Cretaceous Basin (and adjacent regions of the Tethys) in the south. However, post-Cretaceous erosion north of Meißen removed any Upper Cretaceous deposits but erosion outliers at Siebenlehn and especially north of the Forest of Tharandt proof the presence of a marly through silty belt in this area. Three transgressions (base of uppermost Lower to Middle Cenomanian, base of Upper Cenomanian and base of the geslinianum Zone in the mid-Upper Cenomanian) have taken place. The sedimentation was influenced by the topography of the mentioned islands and by movements at structural lines in the Proterozoic and Palaeozoic basement. During the early Late Cenomanian, a marly-silty sedimentation (Mobschatz Formation) in the north existed besides sandy sedimentation in the south (Oberhäslich Formation). The transgression at the base of the geslinianum Zone caused the final submergence of island chains between Meißen, Dresden and Pirna, and a litho- and biofacies bound to cliffs and submarine swells formed. A silty-marly lithofacies, a mixed sandy-silty lithofacies (Dölzschen Formation) and a sandy lithofacies in the south (Sächsisches Elbsandsteingebirge) co-existed during the latest Cenomanian. The first mentioned biofacies yields a rich fauna mainly consisting of oysters, pectinids, rudists, and near-shore gastropods accompanied by echinids and, in some cliffs, teeth of sharks. The Pennrich fauna (Häntzschel 1933; Uhlig 1941) especially consists of the very common serpulids Pyrgopolon (P.) septemsulcata and Glomerula lombricus (formerly Hepteris septemsulcata and G. gordialis).

Depositional environment, foraminifer content and ESR ages of Quaternary Gediz Delta Sediments (Eastern Aegean Sea, İzmir-Western Turkey)

NASA Astrophysics Data System (ADS)

Gökçe Benli, Ekin; Aydın, Hülya; İşintek, İsmail; Engin, Birol; Şengöçmen, Berna

2016-04-01

Sediments and fossil content of Gediz Delta (Eastern Aegean Sea - İzmir) were examined based on the drilling core samples of the YSK-C and SK-246 drilling. W-SW part of the Delta is represented by continental delta sediments up to 6 meters and shallow marine detritic sediments up to 35 meters in the YSK-C drilling. Continental part consists of an soiled, graveled, muddy and sandy sediment in terms of rich organic substance. As for marine part, it consists of bioclast, muddy, fine graveled sand and by repetition of pebble, sand and bioclast bearing mud layers. Bioclasts comprise of bivalvia, echinoid, ostracod, gastropod, foramifer and bryozoa fragments. Benthic foraminiferal fauna determinated in the marine levels are represented by 55 bethic, 2 planktonic species. These foraminifers and bioclasts reflect that the W-SW part of the delta, has been occured in marine conditions between 8-31m deep. E-NE part of the delta is generally represented by continental sediments up to 43.5m in SK-246 drilling. In addition, it includes marine levels in 18-19 m, 23-24 m and 36-37,5 m intervals. Continental sediments of E-NE part is generally represented by calcareous and sandy mud rocks which mostly includes ash, tuff, and pebble derived from Neogene volcanic rocks. As for marine levels, it is composed of calcareous mud stones and calcareous clay stones including very thin gastropod, bivalvia and ostracod in 18- 19 and 36-37.5 meters whereas it is represented by sandy mud stones including a great deal of bentic foraminifer, bivalvia, bryozoa, echinoid, gastropod in 23-24 metres. Thus show that E-NE part of the delta is usually in continental condition but it is occasionally covered by sea. In aging studies of YSK-C core done by ESR method, age of 8-9 m interval is determined to be 11. 376 ± 0,067 Ka; however ages of 10-11m and 24-25 m intervals are revealed to be 16.466 ± 0,016 Ka and 15.344 ± 0,021 Ka respectively; finally age of 25-26 m interval is found to be 19.995 ± 0,022 Ka. This results reflect while the W-SW part of the delta is in marine condition between 20 and 11 Ka, in the E-NE part of the delta, continental and marine conditions were repeated.

Revision of the genus Parasphaerolaimus (Nematoda: Sphaerolaimidae) with description of new species.

PubMed

Zograf, Julia K; Pavlyuk, Olga N; Trebukhova, Yulia A; Tu, Nguyen Dinh

2017-02-15

The family Sphaerolaimidae Filipjev, 1918 includes nematodes that are characterized by the finely striated cuticle, round amphids, broad buccal cavity with longitudinal ribs, and single anterior ovary in females. Parasphaerolaimus species from this family are found in intertidal and subtidal sediments and have also been reported from mangroves and estuaries. Parasphaerolaimus pilosus sp. n. is characterized by the moderately plump body, presence of lateral alae, long cervical setae, small amphids in males, and relatively short spicules. As a result of a comprehensive evaluation of species descriptions, eight species in the genus Parasphaerolaimus are recognized valid, and an identification key to species level is provided.

Flood risk analysis for flood control and sediment transportation in sandy regions: A case study in the Loess Plateau, China

NASA Astrophysics Data System (ADS)

Guo, Aijun; Chang, Jianxia; Wang, Yimin; Huang, Qiang; Zhou, Shuai

2018-05-01

Traditional flood risk analysis focuses on the probability of flood events exceeding the design flood of downstream hydraulic structures while neglecting the influence of sedimentation in river channels on regional flood control systems. This work advances traditional flood risk analysis by proposing a univariate and copula-based bivariate hydrological risk framework which incorporates both flood control and sediment transport. In developing the framework, the conditional probabilities of different flood events under various extreme precipitation scenarios are estimated by exploiting the copula-based model. Moreover, a Monte Carlo-based algorithm is designed to quantify the sampling uncertainty associated with univariate and bivariate hydrological risk analyses. Two catchments located on the Loess plateau are selected as study regions: the upper catchments of the Xianyang and Huaxian stations (denoted as UCX and UCH, respectively). The univariate and bivariate return periods, risk and reliability in the context of uncertainty for the purposes of flood control and sediment transport are assessed for the study regions. The results indicate that sedimentation triggers higher risks of damaging the safety of local flood control systems compared with the event that AMF exceeds the design flood of downstream hydraulic structures in the UCX and UCH. Moreover, there is considerable sampling uncertainty affecting the univariate and bivariate hydrologic risk evaluation, which greatly challenges measures of future flood mitigation. In addition, results also confirm that the developed framework can estimate conditional probabilities associated with different flood events under various extreme precipitation scenarios aiming for flood control and sediment transport. The proposed hydrological risk framework offers a promising technical reference for flood risk analysis in sandy regions worldwide.

Porosity modification during and following deposition of deep-water sediments

NASA Astrophysics Data System (ADS)

Butler, R. W.; McCaffrey, W. D.; Haughton, P.; del Pino Sanchez, A.; Barker, S.; Hailwood, E.; Hakes, B.

2005-12-01

Deposition and early burial of sediments, especially sandy turbidites, are commonly accompanied by the reorganization of porosity structure through the localized expulsion of interstitial fluid. Fluid escape structures are preserved as thin sheets and pipes. Coeval sediment remobilization may be represented by shear structures, commonly taken to indicate down-slope creep and slumping. The history of shearing vs dewatering may be established from cross-cutting structures preserved in outcrop and/or core. Although these relationships are known for gravity-driven soft-sediment deformation on submarine slopes, they can also develop during deposition itself due to shear from the over-riding flow. Such deformation features, including pseudo s-c fabrics and distributed shear, together may previously have been misinterpreted as indicators of palaeoslope (slumps) or even of tectonic deformation. Progressive aggradation of sandy turbidites can show complex banded facies within which soft-sediment deformation is tiered. Syn-deposition micro-growth strata testify to ongoing seabed deformation occurring beneath active flows, while the bedforms themselves provide direct measurements of the magnitude of shear stresses imparted into the seabed and estimates of the shear strength of this substrate. Such banded facies may be interpreted in terms of cyclic partitioning of shear stress into the flow and the substrate. The modified porosity structures and related heterogeneities in permeability of such materials may persist during deeper burial, influencing the rheology of the sediment. These bed-scale processes are reflected in the quality and flow rates of hydrocarbon reservoirs. The reorganization of sand-body architecture through remobilization, by traction and/or down-slope failure, also has a strong impact on the permeability on the multi-bed scale (10s-100s m). Examples will be presented from hydrocarbon reservoirs in the subsurface and from outcrops of Tertiary turbidites in the Alpine-Apennine orogenic system.

Sedimentological characteristics and depositional processes of sediment gravity flows in rift basins: The Palaeogene Dongying and Shahejie formations, Bohai Bay Basin, China

NASA Astrophysics Data System (ADS)

Liu, Lei; Chen, Hongde; Zhong, Yijiang; Wang, Jun; Xu, Changgui; Chen, Anqing; Du, Xiaofeng

2017-10-01

Sediment gravity flow deposits are common, particularly in sandy formations, but their origin has been a matter of debate and there is no consensus about the classification of such deposits. However, sediment gravity flow sandstones are economically important and have the potential to meet a growing demand in oil and gas exploration, so there is a drive to better understand them. This study focuses on sediment gravity flow deposits identified from well cores in Palaeogene deposits from the Liaodong Bay Depression in Bohai Bay Basin, China. We classify the sediment gravity flow deposits into eight lithofacies using lithological characteristics, grain size, and sedimentary structures, and interpret the associated depositional processes. Based on the scale, spatial distribution, and contact relationships of sediment gravity flow deposits, we defined six types of lithofacies associations (LAs) that reflect transformation processes and depositional morphology: LA1 (unconfined proximal breccia deposits), LA2 (confined channel deposits), LA3 (braided-channel lobe deposits), LA4 (unconfined lobe deposits), LA5 (distal sheet deposits), and LA6 (non-channelized sheet deposits). Finally, we established three depositional models that reflect the sedimentological characteristics and depositional processes of sediment gravity flow deposits: (1) slope-apron gravel-rich depositional model, which involves cohesive debris flows deposited as LA1 and dilute turbidity currents deposited as LA5; (2) non-channelized surge-like turbidity current depositional model, which mainly comprises sandy slumping, suspended load dominated turbidity currents, and dilute turbidity currents deposited as LA5 and LA6; and (3) channelized subaqueous-fan depositional model, which consists of non-cohesive bedload dominated turbidity currents, suspended load dominated turbidity currents, and dilute turbidity currents deposited as LA2-LA5, originating from sustained extrabasinal turbidity currents (hyperpycnal flow). The depositional models may be applicable to oil and gas exploration and production from sediment gravity flow systems in similar lacustrine depositional environments elsewhere.

Bacterial community structure and function shift along a successional series of tidal flats in the Yellow River Delta

PubMed Central

Lv, Xiaofei; Ma, Bin; Yu, Junbao; Chang, Scott X.; Xu, Jianming; Li, Yunzhao; Wang, Guangmei; Han, Guangxuan; Bo, Guan; Chu, Xiaojing

2016-01-01

Coastal ecosystems play significant ecological and economic roles but are threatened and facing decline. Microbes drive various biogeochemical processes in coastal ecosystems. Tidal flats are critical components of coastal ecosystems; however, the structure and function of microbial communities in tidal flats are poorly understood. Here we investigated the seasonal variations of bacterial communities along a tidal flat series (subtidal, intertidal and supratidal flats) and the factors affecting the variations. Bacterial community composition and diversity were analyzed over four seasons by 16S rRNA genes using the Ion Torrent PGM platform. Bacterial community composition differed significantly along the tidal flat series. Bacterial phylogenetic diversity increased while phylogenetic turnover decreased from subtidal to supratidal flats. Moreover, the bacterial community structure differed seasonally. Canonical correspondence analysis identified salinity as a major environmental factor structuring the microbial community in the sediment along the successional series. Meanwhile, temperature and nitrite concentration were major drivers of seasonal microbial changes. Despite major compositional shifts, nitrogen, methane and energy metabolisms predicted by PICRUSt were inhibited in the winter. Taken together, this study indicates that bacterial community structure changed along the successional tidal flat series and provides new insights on the characteristics of bacterial communities in coastal ecosystems. PMID:27824160

Bacterial community structure and function shift along a successional series of tidal flats in the Yellow River Delta.

PubMed

Lv, Xiaofei; Ma, Bin; Yu, Junbao; Chang, Scott X; Xu, Jianming; Li, Yunzhao; Wang, Guangmei; Han, Guangxuan; Bo, Guan; Chu, Xiaojing

2016-11-08

Coastal ecosystems play significant ecological and economic roles but are threatened and facing decline. Microbes drive various biogeochemical processes in coastal ecosystems. Tidal flats are critical components of coastal ecosystems; however, the structure and function of microbial communities in tidal flats are poorly understood. Here we investigated the seasonal variations of bacterial communities along a tidal flat series (subtidal, intertidal and supratidal flats) and the factors affecting the variations. Bacterial community composition and diversity were analyzed over four seasons by 16S rRNA genes using the Ion Torrent PGM platform. Bacterial community composition differed significantly along the tidal flat series. Bacterial phylogenetic diversity increased while phylogenetic turnover decreased from subtidal to supratidal flats. Moreover, the bacterial community structure differed seasonally. Canonical correspondence analysis identified salinity as a major environmental factor structuring the microbial community in the sediment along the successional series. Meanwhile, temperature and nitrite concentration were major drivers of seasonal microbial changes. Despite major compositional shifts, nitrogen, methane and energy metabolisms predicted by PICRUSt were inhibited in the winter. Taken together, this study indicates that bacterial community structure changed along the successional tidal flat series and provides new insights on the characteristics of bacterial communities in coastal ecosystems.

Footwall degradation styles and associated sedimentary facies distribution in SE Crete: Insights into tilt-block extensional basins on continental margins

NASA Astrophysics Data System (ADS)

Alves, Tiago M.; Cupkovic, Tomas

2018-05-01

Depositional facies resulting from footwall degradation in extensional basins of SE Crete are studied based on detailed geological maps, regional transects, lithological columns and outcrop photos. During an extensional episode affecting Crete in the late Miocene-early Pliocene, depocentres trending N20°E and N70°E were filled with fan deltas, submarine mass-wasting deposits, sandy turbidites and fine-grained hemipelagites sourced from both nearby and distal sediment sources. Deposition of proximal continental and shallow-marine units, and relatively deep (marine) turbidites and mass-transport deposits, occurred within a complex mosaic of tectonically controlled depocentres. The new geological maps and transects in this work reveal that depositional facies in SE Crete were controlled by: a) their relative proximity to active faults and uplifting footwall blocks, b) the relative position (depth and relative height above sea level) of hanging-wall basins, and c) the nature of the basement units eroded from adjacent footwall blocks. Distal sediment sources supplied background siliciclastic sediment ('hemipelagites'), which differ markedly from strata sourced from local footwalls. In parallel, mass-transport of sediment was ubiquitous on tectonically active slopes, and so was the presence of coarse-grained sediment with sizes varying from large blocks > 50 m-wide to heterolithic mass-transport deposits and silty-sandy turbidites. We expect similar tectono-sedimentary settings to have predominated in tectonically active Miocene basins of the eastern Mediterranean, in which hydrocarbon exploration is occurring at present, and on rifted continental margins across the world.

Wave-induced coherent turbulence structures and sediment resuspension in the nearshore of a prototype-scale sandy barrier beach

NASA Astrophysics Data System (ADS)

Kassem, Hachem; Thompson, Charlotte E. L.; Amos, Carl L.; Townend, Ian H.

2015-10-01

The suspension of sediments by oscillatory flows is a complex case of fluid-particle interaction. The aim of this study is to provide insight into the spatial (time) and scale (frequency) relationships between wave-generated boundary layer turbulence and event-driven sediment transport beneath irregular shoaling and breaking waves in the nearshore of a prototype sandy barrier beach, using data collected through the Barrier Dynamics Experiment II (BARDEX II). Statistical, quadrant and spectral analyses reveal the anisotropic and intermittent nature of Reynolds' stresses (momentum exchange) in the wave boundary layer, in all three orthogonal planes of motion. The fractional contribution of coherent turbulence structures appears to be dictated by the structural form of eddies beneath plunging and spilling breakers, which in turn define the net sediment mobilisation towards or away from the barrier, and hence ensuing erosion and accretion trends. A standing transverse wave is also observed in the flume, contributing to the substantial skewness of spanwise turbulence. Observed low frequency suspensions are closely linked to the mean flow (wave) properties. Wavelet analysis reveals that the entrainment and maintenance of sediment in suspension through a cluster of bursting sequence is associated with the passage of intermittent slowly-evolving large structures, which can modulate the frequency of smaller motions. Outside the boundary layer, small scale, higher frequency turbulence drives the suspension. The extent to which these spatially varied perturbation clusters persist is associated with suspension events in the high frequency scales, decaying as the turbulent motion ceases to supply momentum, with an observed hysteresis effect.

Uranium Redistribution Due to Water Table Fluctuations in Sandy Wetland Mesocosms

EPA Science Inventory

To understand better the fate and stability of immobilized uranium (U) in wetland sediments, and how intermittent dry periods affect U stability, we dosed saturated wetland mesocosms planted with Scirpus acutus with low levels of uranyl acetate for 4 months before imposing...

Identity and abundance of active sulfate-reducing bacteria in deep tidal flat sediments determined by directed cultivation and CARD-FISH analysis.

PubMed

Gittel, Antje; Mussmann, Marc; Sass, Henrik; Cypionka, Heribert; Könneke, Martin

2008-10-01

The identity and abundance of potentially active sulfate-reducing bacteria (SRB) in several metre deep sediments of a tidal sand flat in the German Wadden Sea were assessed by directed cultivation and cultivation-independent CARD-FISH analysis (catalysed reporter deposition fluorescence in situ hybridization). Presumably abundant SRB from different sediment layers between 0.5 and 4 m depth were selectively enriched in up to million-fold diluted cultures supplemented with lactate, acetate or hydrogen. Partial 16S rRNA gene sequences obtained from highest dilution steps showing sulfide formation indicated growth of deltaproteobacterial SRB belonging to the Desulfobulbaceae and the Desulfobacteraceae as well as of members of the Firmicutes. Subsequent isolation resulted in 10 novel phylotypes of both litho- and organotrophic sulfate-reducing Deltaproteobacteria. Molecular pre-screening identified six isolates as members of the Desulfobulbaceae, sharing highest identities with either candidatus 'Desulfobacterium corrodens' (95-97%) or Desulfobacterium catecholicum (98%), and four isolates as members of Desulfobacteraceae, being related to either Desulfobacter psychrotolerans (98%) or Desulfobacula phenolica (95-97%). Relatives of D. phenolica were exlusively isolated from 50 and 100 cm deep sediments with 10 and 2 mM of pore water sulfate respectively. In contrast, relatives of D. corrodens, D. psychrotolerans and D. catecholicum were also obtained from layers deeper than 100 cm and with less than 2 mM sulfate. The high in situ abundance of members of both families in sediment layers beneath 50 cm could be confirmed via CARD-FISH analysis performed with a set of six SRB-specific oligonucleotide probes. Moreover, SRB represented a numerically significant fraction of the microbial community throughout the sediment (up to 7%) and reached even higher cell numbers in deep, sulfate-poor layers than in the sulfate-rich surface sediment. This relatively large community size of potentially active SRB in deep sandy sediments might on the one hand be a result of their syntrophic association with other anaerobes. Our results furthermore support the hypothesis that enhanced advective pore water transport might supply nutrients to microbial communities in deep sandy sediments and point to their so far unrecognized contribution to biogeochemical processes in Wadden Sea sediments.

Morphological and behavioral differences in the gastropod Trophon geversianus associated to distinct environmental conditions, as revealed by a multidisciplinary approach

NASA Astrophysics Data System (ADS)

Márquez, Federico; Nieto Vilela, Rocío Aimé; Lozada, Mariana; Bigatti, Gregorio

2015-01-01

The gastropod Trophon geversianus exhibits shell polymorphisms along its distribution in subtidal and intertidal habitats. Our hypothesis is that morphological and behavioral patterns of T. geversianus represent habitat-specific constrains; subsequently we expect an association between shell morphology, attachment behavior, and habitat. In order to test this hypothesis we compared individuals from intertidal and subtidal habitats, at three sites in Golfo Nuevo (Argentina). We analyzed shell morphology using classic morphometric variables, 3D geometric morphometrics and computing tomography scan. The results were complemented with field observations of attachment to substrate and turning time behavior, as well as of the number of shell scars produced by crab predation. Our results showed differences in shell size and shape between intertidal and subtidal-collected individuals. Centroid size, total weight and shell weight, as well as shell density and thickness were significantly lower in intertidal individuals than in subtidal ones. Gastropods from intertidal habitats presented a low-spired shell and an expanded aperture which might allow better attachment to the bottom substrate, while subtidal individuals presented a slender and narrower shell shape. The number of crab scars was significantly higher in shells from subtidal individuals. Observations of the behavior of gastropods placed at the intertidal splash zone showed 100% of attachment to the bottom in the intertidal individuals, while subtidal specimens only attached in average in 32% of the cases. These latter took 12 times longer to re-attach to the bottom when faced up. Phylogenetic analysis of COI gene fragments showed no consistent differences among individuals sampled in both habitats. All these results suggest that T. geversianus has developed two ecomorphs with distinct morphological and behavioral responses to physically stressful conditions registered in north Patagonian intertidals, as opposed to lower physical stress but higher predation pressure in the subtidal habitats. The findings of this work constitute a starting point in the study of ecological adaptation processes in gastropods from Patagonian coastal environments.

Effects of shelter and enrichment on the ecology and nutrient cycling of microbial communities of subtidal carbonate sediments.

PubMed

Forehead, Hugh I; Kendrick, Gary A; Thompson, Peter A

2012-04-01

The interactions between physical disturbances and biogeochemical cycling are fundamental to ecology. The benthic microbial community controls the major pathway of nutrient recycling in most shallow-water ecosystems. This community is strongly influenced by physical forcing and nutrient inputs. Our study tests the hypotheses that benthic microbial communities respond to shelter and enrichment with (1) increased biomass, (2) change in community composition and (3) increased uptake of inorganic nutrients from the water column. Replicate in situ plots were sheltered from physical disturbance and enriched with inorganic nutrients or left without additional nutrients. At t(0) and after 10 days, sediment-water fluxes of nutrients, O(2) and N(2) , were measured, the community was characterized with biomarkers. Autochthonous benthic microalgal (BMA) biomass increased 30% with shelter and a natural fivefold increase in nutrient concentration; biomass did not increase with greater enrichment. Diatoms remained the dominant taxon of BMA, suggesting that the sediments were not N or Si limited. Bacteria and other heterotrophic organisms increased with enrichment and shelter. Daily exchanges of inorganic nutrients between sediments and the water column did not change in response to shelter or nutrient enrichment. In these sediments, physical disturbance, perhaps in conjunction with nutrient enrichment, was the primary determinant of microbial biomass. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Predicting stress in benthic communities of southeastern U.S. estuaries in relation to chemical contamination of sediments

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

Hyland, J.L.; Dolah, R.F. van; Snoots, T.R.

1999-11-01

Matching data on sediment contaminants (metals, PAHs, PCBs) and macroinfaunal community structure from 231 subtidal stations in southeastern US estuaries were used to develop a framework for evaluating risks of benthic impacts from multiple-contaminant exposure. Sediment contamination was expressed as the mean ratio of individual contaminant concentrations relative to corresponding sediment quality guidelines, that is, to effects range-median (ERM) values, probable effects level (PEL) values, or an aggregate of the two. The probability of a degraded benthos was relatively low in samples with mean ERM quotients {le}0.020, PEL quotients {le}0.035, or combined ERM/PEL quotients {le}0.024. Only 5% of stations withinmore » these ranges had degraded benthic assemblages, while 95% had healthy assemblages. A higher probability of benthic impacts was observed in samples with mean ERM quotients >0.058, PEL quotients >0.096, or ERM/PEL quotients >0.077. Seventy-three to 78% of stations with values in these upper ranges had degraded benthic assemblages, while 22 to 27% had healthy assemblages. Only four stations (three with degraded, one with healthy assemblages) had mean ERM or PEL quotients >1.0, which is the beginning of the range associated with a high probability of mortality in short-term laboratory toxicity tests using amphipods.« less

Seasonal sediment dynamics shape temperate bedrock reef communities

USGS Publications Warehouse

Figurski, Jared D.; Freiwald, Jan; Lonhart, Steve I.; Storlazzi, Curt

2016-01-01

Mobilized seafloor sediment can impact benthic reef communities through burial, scour, and turbidity. These processes are ubiquitous in coastal oceans and, through their influence on the survival, fitness, and interactions of species, can alter the structure and function of benthic communities. In northern Monterey Bay, California, USA, as much as 30% of the seafloor is buried or exposed seasonally, making this an ideal location to test how subtidal temperate rocky reef communities vary in the presence and absence of chronic sediment-based disturbances. Designated dynamic plots were naturally inundated by sediment in summer (50 to 100% cover) and swept clean in winter, whereas designated stable plots remained free of sediment during our study. Multivariate analyses indicated significant differences in the structure of sessile and mobile communities between dynamic and stable reef habitats. For sessile species, community structure in disturbed plots was less variable in space and time than in stable plots due to the maintenance of an early successional state. In contrast, community structure of mobile species varied more in disturbed plots than in stable plots, reflecting how mobile species distribute in response to sediment dynamics. Some species were found only in these disturbed areas, suggesting that the spatial mosaic of disturbance could increase regional diversity. We discuss how the relative ability of species to tolerate disturbance at different life history stages and their ability to colonize habitat translate into community-level differences among habitats, and how this response varies between mobile and sessile communities.

Decomposition of jellyfish carrion in situ: Short-term impacts on infauna, benthic nutrient fluxes and sediment redox conditions.

PubMed

Chelsky, Ariella; Pitt, Kylie A; Ferguson, Angus J P; Bennett, William W; Teasdale, Peter R; Welsh, David T

2016-10-01

Jellyfish often form blooms that persist for weeks to months before they collapse en masse, resulting in the sudden release of large amounts of organic matter to the environment. This study investigated the biogeochemical and ecological effects of the decomposition of jellyfish in a shallow coastal lagoon in New South Wales, Australia. Catostylus mosaicus carrion was added to the surface of shallow sub-tidal sediments and biogeochemical parameters and macrofaunal abundance immediately below the jellyfish carrion were measured over three days. Sediment plots without jellyfish served as controls. Sediment oxygen demand and carbon and nitrogen efflux increased by up to 60-fold in the jellyfish plots, compared to control plots, and dissolved organic nutrient fluxes were more sustained than in previous studies due to the use of fresh rather than frozen biomass. The decomposing jellyfish progressively altered sediment redox conditions, indicated by an increase in porewater iron (II) and sulfide concentrations measured by high-resolution in situ diffusive samplers. Abundance of some macrofaunal taxa in the jellyfish plots decreased relative to controls, however, the abundance of a carnivorous gastropod, which was presumably feeding on the carrion, increased in the jellyfish plots. While jellyfish carrion may be a food source for some macrofauna, low oxygen conditions coupled with the accumulation of toxic dissolved sulfides in the near-surface sediments may explain the overall change in the macroinfaunal community. Copyright © 2016 Elsevier B.V. All rights reserved.

Assessment of chemical and biological significance of arsenical species in the Maurice River drainage basin (N. J. ). Part I. Distribution in water and river and lake sediments

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

Faust, S.D.; Winka, A.J.; Belton, T.

1987-01-01

Levels of arsenic were determined in the bottom sediments and waters of the Maurice River, Blackwater Branch, and Union Lake, (N.J.) that were contaminated by a local chemical industry. This was the only known source of the arsenic. Levels of total arsenic in the sediments and waters were determined quarterly over the course of one year. Sediments were extracted for water soluble and total extractable arsenic fractions and partitioned into four species: monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA), arsenite (As(III)), and arsenate (As(V)). In Union Lake at a shallow sandy sediment site, As (V) predominates. In organic sediments, As (III)more » or (V) predominate depending upon the dissolved oxygen content of the overlying waters. The oxidations state of the arsenic was affected also by the seasonal lake cycles of stratifying or mixing.« less

A vacuum-operated pore-water extractor for estuarine and freshwater sediments

USGS Publications Warehouse

Winger, Parley V.; Lasier, Peter J.

1991-01-01

A vacuum-operated pore-water extractor for estuarine and freshwater sediments was developed and constructed from a fused-glass air stone attached with aquarium airline tubing to a 30 or 60 cc polypropylene syringe. Pore water is extracted by inserting the air stone into the sediment and creating a vacuum by retracting and bracing the syringe plunger. A hand-operated vacuum pump attached to a filtration flask was also evaluated as an alternative vacuum source. The volume and time to extract pore water varies with the number of devices and the sediment particle size. Extraction time is longer for fine sediments than for sandy sediments. Four liters of sediment generally yield between 500 and 1,500 mL of pore water. The sediment that surrounds and accumulates on the air stone acts as a filter, and, except for the first few milliliters, the collected pore water is clear. Because there is no exposure to air or avenue for escape, volatile compounds andin situ characteristics are retained in the extracted pore water.

Autonomous bed-sediment imaging-systems for revealing temporal variability of grain size

USGS Publications Warehouse

Buscombe, Daniel; Rubin, David M.; Lacy, Jessica R.; Storlazzi, Curt D.; Hatcher, Gerald; Chezar, Henry; Wyland, Robert; Sherwood, Christopher R.

2014-01-01

We describe a remotely operated video microscope system, designed to provide high-resolution images of seabed sediments. Two versions were developed, which differ in how they raise the camera from the seabed. The first used hydraulics and the second used the energy associated with wave orbital motion. Images were analyzed using automated frequency-domain methods, which following a rigorous partially supervised quality control procedure, yielded estimates to within 20% of the true size as determined by on-screen manual measurements of grains. Long-term grain-size variability at a sandy inner shelf site offshore of Santa Cruz, California, USA, was investigated using the hydraulic system. Eighteen months of high frequency (min to h), high-resolution (μm) images were collected, and grain size distributions compiled. The data constitutes the longest known high-frequency record of seabed-grain size at this sample frequency, at any location. Short-term grain-size variability of sand in an energetic surf zone at Praa Sands, Cornwall, UK was investigated using the ‘wave-powered’ system. The data are the first high-frequency record of grain size at a single location of a highly mobile and evolving bed in a natural surf zone. Using this technology, it is now possible to measure bed-sediment-grain size at a time-scale comparable with flow conditions. Results suggest models of sediment transport at sandy, wave-dominated, nearshore locations should allow for substantial changes in grain-size distribution over time-scales as short as a few hours.

Dating the upper Cenozoic sediments in Fisher Valley, southeastern Utah ( USA).

USGS Publications Warehouse

Colman, Steven M.; Choquette, Anne F.; Rosholt, J.M.; Miller, G.H.; Huntley, D.J.

1986-01-01

More than 140 m of upper Cenozoic basin-fill sediments were deposited and then deformed in Fisher Valley between about 2.5 and 0.25 m.y. ago, in response to uplift of the adjacent Onion Creek salt diapir. In addition to these basin-fill sediments, minor amounts of eolian and fluvial sand were depositd in Holocene time. The sediments, whose relative ages are known from the stratigraphy, are predominantly sandy, second-cycle red beds derived from nearby Mesozoic rocks; most were deposited in a vertical sequence, filling a sedimentary basin now exposed by fluvial dissection. We have applied a variety of established and experimental dating methods to the sediments in Fisher Valley to establish their age and to provide time control for the recent history of the Onion Creek salt diapir.-from Authors

Beach recovery capabilities after El Niño 2015–2016 at Ensenada Beach, Northern Baja California

NASA Astrophysics Data System (ADS)

Ruiz de Alegría-Arzaburu, Amaia; Vidal-Ruiz, Jesús Adrián

2018-06-01

This study investigates the recovery capabilities of a single-barred beach in the Pacific Mexican coast before and after the 2015-2016 El Niño winter. Concurrent hydrodynamic and morphological data collected over a 3-year period (August 2014-2017) were analysed to determine the subaerial-subtidal volumetric exchange and cross-shore subtidal sandbar migrations, in relation to the incident wave forcing. The beach presented a seasonal seaward and landward sandbar migration cycle. The sandbar migrated offshore during the energetic waves between November and February, and onshore during the milder wave period in spring, until welding to the subaerial beach around May. The transfer of sediment towards the subaerial section continued over the summer, reaching a complete recovery by September/October. Prior to El Niño, the subaerial beach successfully recovered by the end of summer 2015 through the landward sandbar migration process. The 2015-2016 energetic winter waves caused a subaerial volume loss of 140 m3 m-1 (from October 2015 to March 2016), more than twice the amount eroded in the other winters, and the sandbar moved further offshore and to deeper depths (3-4 m) than the winter before. In addition, the energetic 2015-2016 winter waves lasted for 2 months longer than in other years, making the 2016 spring shorter. Consequently, during the onshore migration, the sandbar was unable of reaching shallow depths, and a large portion of sand remained in the subtidal beach. The subaerial beach recovered 60 and 65% of the loss in the 2016 and 2017 summers, respectively. It is concluded that the landward migration process of the sandbar during the spring is critical to ensure a full subaerial beach recovery over the mild wave period in summer. The recovery capabilities of the subaerial beach will depend on the cross-shore distance and depth where the sandbar is located, and on the duration of mild wave conditions required for the sandbar to migrate onshore.

Beach recovery capabilities after El Niño 2015-2016 at Ensenada Beach, Northern Baja California

NASA Astrophysics Data System (ADS)

Ruiz de Alegría-Arzaburu, Amaia; Vidal-Ruiz, Jesús Adrián

2018-05-01

This study investigates the recovery capabilities of a single-barred beach in the Pacific Mexican coast before and after the 2015-2016 El Niño winter. Concurrent hydrodynamic and morphological data collected over a 3-year period (August 2014-2017) were analysed to determine the subaerial-subtidal volumetric exchange and cross-shore subtidal sandbar migrations, in relation to the incident wave forcing. The beach presented a seasonal seaward and landward sandbar migration cycle. The sandbar migrated offshore during the energetic waves between November and February, and onshore during the milder wave period in spring, until welding to the subaerial beach around May. The transfer of sediment towards the subaerial section continued over the summer, reaching a complete recovery by September/October. Prior to El Niño, the subaerial beach successfully recovered by the end of summer 2015 through the landward sandbar migration process. The 2015-2016 energetic winter waves caused a subaerial volume loss of 140 m3 m-1 (from October 2015 to March 2016), more than twice the amount eroded in the other winters, and the sandbar moved further offshore and to deeper depths (3-4 m) than the winter before. In addition, the energetic 2015-2016 winter waves lasted for 2 months longer than in other years, making the 2016 spring shorter. Consequently, during the onshore migration, the sandbar was unable of reaching shallow depths, and a large portion of sand remained in the subtidal beach. The subaerial beach recovered 60 and 65% of the loss in the 2016 and 2017 summers, respectively. It is concluded that the landward migration process of the sandbar during the spring is critical to ensure a full subaerial beach recovery over the mild wave period in summer. The recovery capabilities of the subaerial beach will depend on the cross-shore distance and depth where the sandbar is located, and on the duration of mild wave conditions required for the sandbar to migrate onshore.

Benthic macrofauna habitat associations in Willapa Bay, Washington, USA

NASA Astrophysics Data System (ADS)

Ferraro, Steven P.; Cole, Faith A.

2007-02-01

Estuary-wide benthic macrofauna-habitat associations in Willapa Bay, Washington, United States, were determined for 4 habitats (eelgrass [ Zostera marina], Atlantic cordgrass [ Spartina alterniflora], mud shrimp [ Upogebia pugettensis], ghost shrimp [ Neotrypaea californiensis]) in 1996 and 7 habitats (eelgrass, Atlantic cordgrass, mud shrimp, ghost shrimp, oyster [ Crassostrea gigas], bare mud/sand, subtidal) in 1998. Most benthic macrofaunal species inhabited multiple habitats; however, 2 dominants, a fanworm, Manayunkia aestuarina, in Spartina, and a sand dollar, Dendraster excentricus, in subtidal, were rare or absent in all other habitats. Benthic macrofaunal Bray-Curtis similarity varied among all habitats except eelgrass and oyster. There were significant differences among habitats within- and between-years on several of the following ecological indicators: mean number of species ( S), abundance ( A), biomass ( B), abundance of deposit (AD), suspension (AS), and facultative (AF) feeders, Swartz's index (SI), Brillouin's index ( H), and jackknife estimates of habitat species richness (HSR). In the 4 habitats sampled in both years, A was about 2.5× greater in 1996 (a La Niña year) than 1998 (a strong El Niño year) yet relative values of S, A, B, AD, AS, SI, and H among the habitats were not significantly different, indicating strong benthic macrofauna-habitat associations despite considerable climatic and environmental variability. In general, the rank order of habitats on indicators associated with high diversity and productivity (high S, A, B, SI, H, HSR) was eelgrass = oyster ≥ Atlantic cordgrass ≥ mud shrimp ≥ bare mud/sand ≥ ghost shrimp = subtidal. Vegetation, burrowing shrimp, and oyster density and sediment %silt + clay and %total organic carbon were generally poor, temporally inconsistent predictors of ecological indicator variability within habitats. The benthic macrofauna-habitat associations in this study can be used to help identify critical habitats, prioritize habitats for environmental protection, index habitat suitability, assess habitat equivalency, and as habitat value criteria in ecological risk assessments in Willapa Bay.

Upper Cretaceous ramp limestones from the Sorrento Peninsula (southern Apennines, Italy): micro- and macrofossil associations and their significance in the depositional sequences

NASA Astrophysics Data System (ADS)

Carannante, G.; Ruberti, D.; Sirna, M.

2000-04-01

The Upper Cretaceous limestones of the Sorrento Peninsula are primarily characterized by wackestone/packstone with benthic foraminifers, thaumatoporellaceans and Aeolisaccus sp. and by rudist floatstones. Rudists in growth position are rare; most of them appear toppled and locally oriented but not reworked. In some cases they form small bouquets no more than 30 cm thick. The successions analyzed in the Sorrento Peninsula encompass a variety of facies representative of inner shelf environments in a ramp-like depositional setting. On the basis of lithologic and sedimentologic characteristics and on a qualitative analysis of the biofacies, three major facies associations have been recognized corresponding to: (a) intertidal silty-sand flats and shallow lagoons; (b) subtidal mobile foraminiferal sand sheets; (c) subtidal rudist dwelt sand plain. In the lower part of the successions periodic (more or less prolonged) emersions (subaqueous with fresh/brackish waters or subaerial exposure) are documented. The upper part of each succession lacks any emersion evidence; submarine exposure surfaces are testified by firmground-related features. The periodic influence of high-energy regimes (some storm-related events) is documented by wave- and cross-laminations, HCS and the lack of fine sediments. Lithofacies are arranged in depositional cycles that may correspond to individual beds. The boundaries of the depositional cycles show evidence of subaerial or submarine exposures. The nature and position of these discontinuity surfaces in the successions provide an important clue to interpretation in terms of both depositional environment and vertical evolution. The increase in thickness of the depositional cycles and the gradual change from peritidal/shallow-subtidal cycles to dominantly subtidal cycles, document an increase in the amount of accommodation space which resulted from a long-term rise in relative sea-level. A detailed study of benthic associations (micro- and macrofauna) has been carried out in order to identify accurately further signs of periodicity contained within the successions as a whole. These Upper Cretaceous limestones are abundantly fossiliferous with only a moderately diverse fauna. There are no significant differences in terms of species, the assemblages simply reflecting differences in abundance of the same species. Taphonomic studies of rudist-rich beds permit seven major shell-bed types to be distinguished. Six main foraminiferal assemblages have been detected, and the distribution and relative abundance of the species have been examined within the environments inferred through facies analysis. The taphonomic data and the foraminiferal assemblage abundance and diversity, have been compared with lithologic and sedimentologic data in order to elucidate their distribution within depositional cycles and throughout the successions. The successions show little up-section changes in lithology and in taxonomic composition of the foraminiferal assemblages. It is therefore difficult to establish a paleoenvironmental trend independent of the rudist shell concentrations, which do change up-section. We noticed an overall increase in thickness and abundance of the shell beds and a shift in types of shell concentration and in taxonomic composition. These characteristics, associated with the upward disappearance of emersion surfaces, the higher frequency of storm and/or wave intercalations, the increase in thickness of the depositional sequences and the gradual change from peritidal/shallow-subtidal cycles to dominantly subtidal cycles, document a general deepening-upward trend. More open water conditions with a depth between fairweather and storm wave-base became established as a result of relative sea-level rise and to a consequent increase in the available accommodation space.

Recent carbonate sedimentation on Balearic platform: model for temperate-climate carbonate shelves

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

Fornos, J.; Rodriguez-Perea, A.; Massuti, C.

Existing models for carbonate sedimentation on continental platforms are derived from the study of modern carbonate platforms in tropical climates. The Balearic platform in the western Mediterranean provides a new model for carbonate sedimentation in a temperature, semiarid climate. On most of the continental shelf around the Balearic Islands, modern sediments are exclusively bioclastic carbonates. Shoreline carbonate sediments are bioclastic sands and muds accumulating in beach-dune systems without significant tidal influence (there are no astronomical tides in the western Mediterranean ). From the upper shoreface to 35 m deep, the sandy bottom is extensively colonized by sea grass (Posidonia oceanica),more » the rhizomes and roots of which form a rigid entrapment that retains the sediment derived from calcareous organisms living within the sea grass and from calcareous epiphytes living on the stems and leaves. Archeological dating establishes a rate of vertical accretion in this zone of 10/sup 3/ Bubnoff units (1 Bubnoff unit = 1 mm/1000 years). Between depths of 40 and 60 m, carbonate sands are composed predominantly or red-algal fragments. Intensely bioturbated wave ripples occur in environments dominated by laminar red algae (Lithothamnium and Phymatolithon). Below depths of 60 m, coarse sediment produced by rhodolitic and ramose red algae is deposited in areas of tens to hundreds of meters in size. Biogenic buildups up to 2 m high occur in sandy areas as well as in deeper muddy areas. At the same depth in open-platform zones, the bottom topography is characterized by large hummocks several hundred meters across. From the horizontal distribution of facies, it is possible to construct the probable vertical sequence of lithofacies which would characterize carbonates accumulating on a temperate-climate carbonate shelf. Many of these lithofacies are recognized in upper Miocene limestones on the Balearic Islands.« less

Methodical Features of the Field Researches of the Anapa Bay-Bar Sediment Composition

NASA Astrophysics Data System (ADS)

Krylenko, Marina; Krylenko, Viacheslav; Gusakova, Anastasiya; Kosyan, Alisa

2014-05-01

Resort Anapa (Black Sea coast, Russia) holds leading positions in the Russian market of sanatorium-resort and children's recreation. The 50-200 m sandy beaches of Anapa bay-bar are the main value of the resort. Anapa bay-bar is an extensive accumulative sandy body having the length about 47 km. Obvious attributes of the beaches degradation demanding immediate measures on their protection and restoration are observed in last years. The main reason of degradation is beach material deficiency. To organize researches of the sediments of this extensive natural object is a difficult challenge. It is necessary to reduce number of tests to minimum. It is important to record differences of separate bay-bar sites and to receive comparable data for different seasons and years. Our researches showed that the grain-size sediment composition significantly depends of position on local relief. Consequently, researching of the alongshore change of the sediment size is effectual to realize at this morphological elements. Shelly detritus makes to 30% of total amount of beach sediments. It is necessary to consider that quantitative shell distribution along the coast significantly depends on a configuration of the coastline and an underwater relief. Quantity of the shells for cross-shore profile is maximal near coastline. For identification of the sediment sources and researching of their fluxes to use minerals markers (heavy minerals) is optimum. The maximum of heavy minerals concentration is characteristic for fraction 0.1-0.05mm at depth more 5 m. The maintenance of this fraction within other morphological zones isn't enough for the analysis or is excessively changeable. Use of the revealed features allowed to conduct the representative field researches of grain-size and mineral sediment composition for all morphological zones of underwater and coast part of the Anapa bay-bar. This methodic recommendations are workable for researches on others coast accumulative body. The work is carried out under financial support of the Russian Foundation of Basic Research.

Beach-ridge sedimentology as an archive of terrestrial climate change: Insights from a geochemical and stratigraphic study of the Tijucas Strandplain, southern Brazil

NASA Astrophysics Data System (ADS)

Krask, J. L.; Hein, C. J.; Galy, V.; FitzGerald, D.; Henrique de Fontoura Klein, A.

2017-12-01

Whereas millennial-scale variations in climate forcing drives changes in terrestrial processes, which are in turn directly linked to fluvial sediment loads (e.g., weathering and erosion), the impact of decadal- to centennial- scale climate fluctuations on downstream coastal sedimentation patterns and landscape evolution remains unclear. Specifically, the connection between long-term (decades or more) precipitation seasonality and sediment export from river systems has not been established. This study examines the manner in which sub-millennial-scale fluctuations in precipitation over river catchments may be recorded in coastal progradational sedimentary archives. The 5-km wide Tijucas Strandplain (southern Brazil) formed over the last 5800 years through the rapid reworking of sediment discharged from the Tijucas River in a regime of falling sea level. In an overall regime shift from sand- to mud- dominance (linked to a long-term reduction in wave energy caused by bay shoaling) are nearly 70 distinct transitions between shore-parallel sand- and mud- dominated facies. Bulk organic carbon and terrestrial plant-wax fatty acid stable hydrogen (δD) and carbon (δ13C) isotopic measurements from sediments from select sandy and muddy ridges across the plain reveal that these two sedimentological regimes are geochemically distinct. Specifically, waxes from sediments deposited during periods of sandy progradation had δD values, on average, >10 ‰ higher than those from mud-dominated periods, indicating that these sedimentary units reflect different hydroclimatic conditions within the river drainage basin at the time of deposition. Comparison of plant wax isotopic signatures of river, bay, and beach sediments during the current period of mud-dominated progradation reveals a close correlation with earlier periods of mud deposition within the Tijucas Strandplain. Thus, decadal- to centennial- scale sedimentologic transitions within the plain are interpreted to reflect climate-driven changes in mud export rates, as product of modifications in river basin vegetation and soil formation and erosional processes.

Geomorphic response of the Sandy River, Oregon, to removal of Marmot Dam

USGS Publications Warehouse

Major, Jon J.; O'Connor, Jim E.; Podolak, Charles J.; Keith, Mackenzie K.; Grant, Gordon E.; Spicer, Kurt R.; Pittman, Smokey; Bragg, Heather M.; Wallick, J. Rose; Tanner, Dwight Q.; Rhode, Abagail; Wilcock, Peter R.

2012-01-01

The October 2007 breaching of a temporary cofferdam constructed during removal of the 15-meter (m)-tall Marmot Dam on the Sandy River, Oregon, triggered a rapid sequence of fluvial responses as ~730,000 cubic meters (m3) of sand and gravel filling the former reservoir became available to a high-gradient river. Using direct measurements of sediment transport, photogrammetry, airborne light detection and ranging (lidar) surveys, and, between transport events, repeat ground surveys of the reservoir reach and channel downstream, we monitored the erosion, transport, and deposition of this sediment in the hours, days, and months following breaching of the cofferdam. Rapid erosion of reservoir sediment led to exceptional suspended-sediment and bedload-sediment transport rates near the dam site, as well as to elevated transport rates at downstream measurement sites in the weeks and months after breaching. Measurements of sediment transport 0.4 kilometers (km) downstream of the dam site during and following breaching show a spike in the transport of fine suspended sediment within minutes after breaching, followed by high rates of suspended-load and bedload transport of sand. Significant transport of gravel bedload past the measurement site did not begin until 18 to 20 hours after breaching. For at least 7 months after breaching, bedload transport rates just below the dam site during high flows remained as much as 10 times above rates measured upstream of the dam site and farther downstream. The elevated sediment load was derived from eroded reservoir sediment, which began eroding when a meters-tall knickpoint migrated about 200 m upstream in the first hour after breaching. Rapid knickpoint migration triggered vertical incision and bank collapse in unconsolidated sand and gravel, leading to rapid channel widening. Over the following days and months, the knickpoint migrated upstream more slowly, simultaneously decreasing in height and becoming less distinct. Within 7 months, the knickpoint had migrated 2 km upstream from the dam site and became a riffle-like feature approximately 1 m high and a few tens of meters long. Knickpoint migration, vertical incision, and lateral erosion evacuated about 15 percent of the initial reservoir volume (125,000 m3) within 60 hours following breaching, and by the end of the high flows in May 2008, about 50 percent of the volume had been evacuated. Large stormflows in November 2008 and January 2009 eroded another 6 percent of the original volume of impounded sediment. Little additional sediment eroded during the remainder of the second year following breaching. The rapid erosion of sediment by the modest flow that accompanied dam breaching was driven mainly by the steep hydraulic gradient associated with the abrupt change of base level and knickpoint formation and was aided by the unconsolidated and cohesionless character of the reservoir sediment. In the ensuing months, transport competence diminished as channel geometry evolved and the river gradient through the reservoir reach diminished. Changes in profile gradient in conjunction with channel coarsening and widening led to a rapid slowing of the rate of reservoir erosion. Sediment transport and deposition were strongly controlled by channel-gradient discontinuities and valley morphology downstream of the dam site. Those influences led to a strong divergence of sand and gravel transport and to deposition of a sediment wedge, as much as 4 m thick, that tapered to the preremoval channel bed 1.3 km downstream of the dam site. After 2 years, that deposit contained about 25 percent of the total volume of sediment eroded from the reservoir. The balance was distributed among pools within the Sandy River gorge, a narrow bedrock canyon extending 2 to 9 km downstream of the dam site, and along the channel farther downstream. A two-fraction sediment budget for the first year following breaching indicates that most of the gravel eroded from the reservoir reach was deposited within the sediment wedge and within the gorge, whereas eroded sand largely passed through the gorge and was broadly dispersed farther downstream. The sequence of transporting flows affected the specific trajectory of reservoir erosion and downstream sediment transport during the 2 years following breaching. However, because the overall erosion was largely a consequence of knickpoint retreat and channel widening, which in the 2 years after removal had affected most of the reservoir reach, it is unlikely that the specific sequence of flows significantly affected the overall outcome. Because the knickpoint had largely passed through the reservoir within 2 years, and the remaining reservoir sediment is mostly isolated high above armored or bedrock banks, it is unlikely that substantial additional sediment from the reservoir site will enter the system unless very large flows occur. Continued channel evolution downstream of the dam site is probable as deposits formed in the first 2 years are episodically mobilized. Below the Sandy River gorge, detection of effects related to release of reservoir sediment is challenging, especially in areas of sand deposition, because of the high background supply of sand in the river and substantial channel dynamism.

NGH: A Dynamic Factor in Deep Water Sediments & the Geological Record

NASA Astrophysics Data System (ADS)

Max, M. D.; Johnson, A. H.

2012-12-01

Prior to identification of natural gas hydrate (NGH) in marine sediments, gravity and tectonic forces were the recognized dynamic forces that could cause disruption in deep marine sediments. NGH introduces a new dynamic factor into continental slope and rise sediments as well as sediments in the deeper parts of some continental shelves. Two critical elements interplay to provide for a slow acting, long-term NGH-dynamic cyclical system. First, NGH forms spontaneously from dissolved natural gas generally in a passive manner without causing any other than very subtle alterations to the megascopic sediment structure. When NGH forms in either dispersed form in muddy sediments or in concentrated form in veins or nodules or in porosity in sandy sediments, it increases overall mechanical strength. Second, when it dissociates, mechanical strength weakens to the point where shear strengths can approach zero. Because the chemical reaction of NGH is highly reversible, changes in sea level that affect pressure, and changes in seafloor temperature can alter rapidly the tendency of NGH to either crystallize or dissociate, with consequent structural and morphological effects. The cyclicity of the Earth's climate introduces a mechanism for periodically injecting overpressured gas into marine sediments as the gas hydrate stability zones (GHSZ) undergoes changes to its thickness and depth. Natural climate change has the potential to produce overpressured natural gas converted from NGH in marine sediments periodically. In-place disruption would consist of disrupted sandy beds, chaotic textures on all scales, intrusion effects, limited mass flow features, dramatic sediment mixing not related to large scale movement and sediment redeposition from fluidized beds. Mobilization would involve larger scale sediment mass flow effects that would be indistinguishable from olistostromic melanges postulated to be initiated by tectonic or gravitational forces. The earliest interpretation of this fluidization type of large scale sediment disruption in the later part of the 1900s identified them as tectonic in origin. Subsequently, in the 1970s, it was recognized that the features were more likely a product of soft sediment deformation whose initiator might be gravity or tectonic forces, of 'tectonosedimentary' origin. The action of the NGH cycle to initiate sedimentary disruption may more readily explain many of these features in the geological record. Drill core taken across seismic reflection sediment redeposition features that otherwise show no tectonic activity related movement in abandoned GHSZ could provide important evidence for the long-term geological action of the NGH cycle.

Facies analysis and depositional environments of upper part of Richmond group (upper Ordovician), Richmond, Indiana, to Xenia, Ohio

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

Betz, C.E.; Martin, W.D.

Rock sections of the Drakes, Elkhorn, and Whitewater Formations were studied along an east-west-trending line in order to distinguish facies changes in a slope direction across the paleodepositional basin. The Richmond limestones, shales, and dolostones formed from fine-grained, terrigenous and carbonate sediments deposited on a shallow marine ramp within the humid, tropical, low latitudes of the Southern Hemisphere. Depositional environments on the ramp are represented by five main facies type. The five Richmond facies form a subtidal to supratidal shallowing-upward sequence. This progressive shallowing during the Late Ordovician resulted from the westward regional progradation of Queenston deltaic facies.

Effects of reclamation on macrobenthic assemblages in the coastline of the Arabian Gulf: a microcosm experimental approach.

PubMed

Naser, Humood A

2011-03-01

Coastal reclamation and modifications are extensively carried out in Bahrain, which may physically smother the coastal and subtidal habitats resulting in changes to abundance and distribution of macrobenthic assemblages. A microcosm laboratory experiment using three common macrobenthic invertebrates from a proposed reclaimed coastal area was preformed to examine their responses to mud burial using marine sediment collected from a designated borrow area. Significant difference in numbers of survived organisms between control and experimental treatments with a survival percentage of 41.8% for all of the selected species was observed. The polychaete Perinereis nuntia showed the highest percentage of survival (57.1%) followed by the bivalve Tellinavaltonis (42.3%) and the gastropod Cerithidea cingulata (24.0%). Quantifying species responses to sediment burial resulted from dredging and reclamation will aid in predicting the expected ecological impacts associated with coastal developments and subsequently minimizing these impacts and maintaining a sustainable use of coastal and marine ecosystems in the Arabian Gulf. Copyright © 2010 Elsevier Ltd. All rights reserved.

Rates of microbial metabolism in deep coastal plain aquifers

USGS Publications Warehouse

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

1990-01-01

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

The U.S. Geological Survey's Sediment-bound Contaminant Resiliency and Response Strategy: A Tiered Multi-metric Approach to Environmental Health and Hazards in the Northeastern USA

NASA Astrophysics Data System (ADS)

Reilly, T. J.; Focazio, M. J.; Murdoch, P. S.; Benzel, W. M.; Fisher, S. C.; Griffin, D. W.; Iwanowicz, L. R.; Jones, D. K.; Loftin, K. A.

2014-12-01

Enhanced dispersion and concentration of contaminants such as trace metals and organic pollutants through storm-induced disturbances and sea level rise (SLR) are major factors that could adversely impact the health and resilience of communities and ecosystems in coming years. As part of the response to Hurricane Sandy, the U.S. Geological Survey collected data on the effects of contaminant source disturbance and dispersion. A major limitation of conducting pre- and post-Sandy comparisons was the lack of baseline data in locations proximal to potential contaminant sources and mitigation activities, sensitive ecosystems, and recreational facilities where human and ecological exposures are probable. To address this limitation, a Sediment-bound Contaminant Resiliency and Response (SCoRR) strategy with two operational modes, Resiliency (baseline) and Response (event-based), has been designed by leveraging existing interagency networks and resources. In Resiliency Mode, sites will be identified and sampled using standardized procedures prioritized to develop baseline data and to define sediment-quality based environmental health metrics. In Response Mode, a subset of sites within the network will be evaluated to ensure that adequate pre-event data exist at priority locations. If deficient, pre-event samples will be collected from priority locations. Crews will be deployed post-event to resample these locations allowing direct evaluation of impacts, as well as redefining baseline conditions for these areas. A tiered analytical and data integration strategy has been developed that will identify vulnerable human and environmental receptors, the sediment-bound contaminants present, and the biological activity and potential effects of exposure to characterized sediments. Communication mechanisms are in development to make resulting data available in a timely fashion and in a suitable format for informing event response and recovery efforts.

Hydraulic Experiments for Determination of In-situ Hydraulic Conductivity of Submerged Sediments

PubMed Central

Lee, Bong-Joo; Lee, Ji-Hoon; Yoon, Heesung; Lee, Eunhee

2015-01-01

A new type of in-situ hydraulic permeameter was developed to determine vertical hydraulic conductivity (VHC) of saturated sediments from hydraulic experiments using Darcy's law. The system allows water to move upward through the porous media filled in the permeameter chamber driven into sediments at water-sediment interface. Darcy flux and hydraulic gradient can be measured using the system, and the VHC can be determined from the relationship between them using Darcy's law. Evaluations in laboratory and in field conditions were performed to see if the proposed permeameter give reliable and valid measures of the VHC even where the vertical flow at water-sediment interface and fluctuation of water stage exist without reducing the accuracy of the derived VHC. Results from the evaluation tests indicate that the permeameter proposed in this study can be used to measure VHC of saturated sandy sediments at water-sediment interface in stream and marine environment with high accuracy. PMID:25604984

Installation Restoration Program. Phase I. Records Search, Hazardous Materials Disposal Sites. Myrtle Beach Air Force Base, South Carolina.

DTIC Science & Technology

1981-10-01

Geography 3-1 Topography 3-. Drainage 3-1 ii Page Surface Geology 3-3 Barrier Sediments 3-3 Myrtle Beach Backbarrier Sediments 3-3 soils 3-5 Subsurface...Beach AFB Surface Drainage and Surface Water Sampling Points 3-2 3.2 Myrtle Beach AFB Surface Soils 3-4 3.3 Myrtle Beach AFB Location of Geologic Cross...has created a potential contamination problem. This situation is compounded by the site’s sandy soil and shallow ground water table. b.) Weathering Pit

Sedimentological and radiochemical characteristics of marsh deposits from Assateague Island and the adjacent vicinity, Maryland and Virginia, following Hurricane Sandy

USGS Publications Warehouse

Smith, Christopher G.; Marot, Marci E.; Ellis, Alisha M.; Wheaton, Cathryn J.; Bernier, Julie C.; Adams, C. Scott

2015-09-15

This report serves as an archive for sedimentological and radiochemical data derived from the surface sediments and marsh cores collected March 26–April 4, 2014. Select surficial data are available for the additional sampling periods October 21–30, 2014. Downloadable data are available as Excel spreadsheets and as JPEG files. Additional files include: Field documentation, x-radiographs, photographs, detailed results of sediment grain size analyses, and formal Federal Geographic Data Committee metadata (data downloads).

Sediment Equilibrium and Diffusive Fluxes in Relation to Phosphorus Dynamics in the Turbid Minnesota River

DTIC Science & Technology

2009-01-01

extractable P and K in a sandy clay loam soil under continuous corn ( Zea mays L .). Can J Soil Sci 75:361-367. Zhang, T. Q., A. F. MacKenzie, B. C...diffusive P flux from deposited sediment stored in river channels may also play a role in soluble P control. Ranges in equilibrium partitioning between...largest plants in the State of Minnesota, discharge (average discharge = 1.8 m3 s-1) at effluent P concentrations of 1.5 mg L -1 or less. A 538-megawatt

Sedimentation of the mud belt along the coast of China from the mouth of the Yangtze (Changjiang) River to northern Taiwan Strait: An Source-to-Sink Perspective

NASA Astrophysics Data System (ADS)

Chien, C. C.; Liu, J. T.; Yang, R.; Huh, C. A.; Su, C. C.

2016-02-01

Sediments in the Taiwan Strait are originated from Mainland China and Taiwan. The China Coastal Current, influenced by the northeast monsoon in winter, becomes enhanced, which caries the sediments exported from the Yangtze River to the southern East China Sea and the Taiwan Strait along the Zhemin-Taiwan Strait mud belt. The sediment transport process is also influenced by tidal current and Kuroshio Branch Current and Taiwan Warm Current, making the seafloor sediment signals complex. This study used R/V Ocean Researcher V (Cruise 0032), to collect six box cores and three gravity cores along the Zhemin mud belt and the mud belt in northern Taiwan Strait in the winter of 2014. From the core samples, grain-size distribution, Multi-Sensor Core Logger, and 7Be activity were measured to investigate the sedimentation process along the mud belts. The box core taken at the mouth of the Changjiang- is composed of homogeneous clay and rich in shell fragments. The core off the mouth of Ou River is composed of homogeneous clay, but showing horizontal laminations. Near the Taishan Island off the coast of Zhejiang the core is consisted of a homogeneous sandy sediments that turned into clay. Off the mouth of the Min River the core consists of clay with shell fragments. Off the coast of the Wu River on the west coast of the Taiwan, the core is mainly composed of muddy sediments, which has the siltstone layers of oblique bedding. Off the mouth of Zhuoshui River in central Taiwan, the core is composed of sandy sediments. From the mouth of the Changhjiang, Zhemin mud belt, the northern Taiwan Strait mud belt, to the central Taiwan Strait, 7Be activity in the seafloor sediment indicates that the freshness of the terrigenous sediments decreased. The Mass Magnetic Susceptiblity (MSI) demonstrates that the terrigenous sediments decreased from north to south. The MSI signals in the core off the mouth of the Minjiang are different from those in the neighboring cores. This is suspected due to the convergence of sediments from the Changjiang and Taiwan. The particle sizes of the cores show that the sediment became coarser from the north to south. In the future the study will make use of 210Pbex, and other environmental and provenance such as water dynamic mechanism variables to explore the sediment source and sink patterns along with the Zhemin-Taiwan Strait mud belts.

Biogenic disturbance determines invasion success in a subtidal soft-sediment system.

PubMed

Lohrer, Andrew M; Chiaroni, Luca D; Hewitt, Judi E; Thrush, Simon F

2008-05-01

Theoretically, disturbance and diversity can influence the success of invasive colonists if (1) resource limitation is a prime determinant of invasion success and (2) disturbance and diversity affect the availability of required resources. However, resource limitation is not of overriding importance in all systems, as exemplified by marine soft sediments, one of Earth's most widespread habitat types. Here, we tested the disturbance-invasion hypothesis in a marine soft-sediment system by altering rates of biogenic disturbance and tracking the natural colonization of plots by invasive species. Levels of sediment disturbance were controlled by manipulating densities of burrowing spatangoid urchins, the dominant biogenic sediment mixers in the system. Colonization success by two invasive species (a gobiid fish and a semelid bivalve) was greatest in plots with sediment disturbance rates < 500 cm(3) x m(-2) x d(-1), at the low end of the experimental disturbance gradient (0 to > 9000 cm(3) x m(-2) x d(-1)). Invasive colonization declined with increasing levels of sediment disturbance, counter to the disturbance-invasion hypothesis. Increased sediment disturbance by the urchins also reduced the richness and diversity of native macrofauna (particularly small, sedentary, surface feeders), though there was no evidence of increased availability of resources with increased disturbance that would have facilitated invasive colonization: sediment food resources (chlorophyll a and organic matter content) did not increase, and space and access to overlying water were not limited (low invertebrate abundance). Thus, our study revealed the importance of biogenic disturbance in promoting invasion resistance in a marine soft-sediment community, providing further evidence of the valuable role of bioturbation in soft-sediment systems (bioturbation also affects carbon processing, nutrient recycling, oxygen dynamics, benthic community structure, and so on.). Bioturbation rates are influenced by the presence and abundance of large burrowing species (like spatangoid urchins). Therefore, mass mortalities of large bioturbators could inflate invasion risk and alter other aspects of ecosystem performance in marine soft-sediment habitats.

Rapid sedimentation of iron oxyhydroxides in an active hydrothermal shallow semi-enclosed bay at Satsuma Iwo-Jima Island, Kagoshima, Japan

NASA Astrophysics Data System (ADS)

Kiyokawa, Shoichi; Ueshiba, Takuya

2015-04-01

Hydrothermal activity is common in the fishing port of Nagahama Bay, a small semi-enclosed bay located on the southwest coast of Satsuma Iwo-Jima Island (38 km south of Kyushu Island, Japan). The bay contains red-brown iron oxyhydroxides and thick deposits of sediment. In this work, the high concentration and sedimentation rates of oxyhydroxide in this bay were studied and the sedimentary history was reconstructed. Since dredging work in 1998, a thickness of 1.0-1.5 m of iron oxyhydroxide-rich sediments has accumulated on the floor of the bay. To estimate the volume of iron oxyhydroxide sediments and the amount discharged from hydrothermal vents, sediment traps were operated for several years and 13 sedimentary core samples were collected to reconstruct the 10-year sedimentary history of Nagahama Bay. To confirm the timing of sedimentary events, the core data were compared with meteorological records obtained on the island, and the ages of characteristic key beds were thus identified. The sedimentation rate of iron oxyhydroxide mud was calculated, after correcting for sediment input from other sources. The sediments in the 13 cores from Nagahama Bay consist mainly of iron oxyhydroxide mud, three thick tephra beds, and a topmost thick sandy mud bed. Heavy rainfall events in 2000, 2001, 2002, and 2004-2005 coincide with tephra beds, which were reworked from Iwo-Dake ash deposits to form tephra-rich sediment. Strong typhoon events with gigantic waves transported outer-ocean-floor sediments and supplied quartz, cristobalite, tridymite, and albite sands to Nagahama Bay. These materials were redeposited together with bay sediments as the sandy mud bed. Based on the results from the sediment traps and cores, it is estimated that the iron oxyhydroxide mud accumulated in the bay at the relatively rapid rate of 33.3 cm/year (from traps) and 2.8-4.9 cm/year (from cores). The pore water contents within the sediment trap and core sediments are 73%-82% and 47%-67%, respectively. The estimated production of iron oxyhydroxide for the whole fishing port from trap cores is 142.7-253.3 t/year/5000 m2. From sediment cores, however, the accumulation of iron oxyhydroxide sediments on the sea floor is 39-95 t/year/5000 m2. This finding indicates that the remaining 63%-73% of iron was transported out to sea from Nagahama Bay. Even with a high rate of iron oxyhydroxide production, the sedimentation rate of iron oxyhydroxides in the bay is considerably higher than that observed in modern deep-ocean sediments. This example of rapid and abundant oxyhydroxide sedimentation might provide a modern analog for the formation of iron deposits in the geological record, such as ironstones and banded iron formations.

Observations of the R reflector and sediment interface reflection at the Shallow Water '06 Central Site.

PubMed

Choi, Jee Woong; Dahl, Peter H; Goff, John A

2008-09-01

Acoustic bottom-interacting measurements from the Shallow Water '06 experiment experiment (frequency range 1-20 kHz) are presented. These are co-located with coring and stratigraphic studies showing a thin (approximately 20 cm) higher sound speed layer overlaying a thicker (approximately 20 m) lower sound speed layer ending at a high-impedance reflector (R reflector). Reflections from the R reflector and analysis of the bottom reflection coefficient magnitude for the upper two sediment layers confirm both these features. Geoacoustic parameters are estimated, dispersion effects addressed, and forward modeling using the parabolic wave equation undertaken. The reflection coefficient measurements suggest a nonlinear attenuation law for the thin layer of sandy sediments.

77 FR 32573 - Takes of Marine Mammals Incidental to Specified Activities; Construction and Race Event...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-01

... operations, support space, media operations, hospitality services, sponsored commercial space, and...). Intertidal habitats in the Central Bay, or those that lie between low and high tides, include sandy beaches... sediment and hard substrate habitat. Soft bottom substrate ranges between soft mud with high silt and clay...

3-D Wave-Structure Interaction with Coastal Sediments - A Multi-Physics/Multi-Solution-Techniques Approach

DTIC Science & Technology

2008-01-01

element method (BEM). Reynolds averaged Navier-Stokes (RANS) and the particle finite element method ( PFEM ) will be used in the water/mine/sand domain...and deformable sandy seabed (median grain diameter: 0.2 mm) 12 SOLID/FEM SAND/SPH GEOMATERIALS FNPF/BEM FNPF/BEMRANS/ PFEM

Sound Speed and Attenuation in Multiphase Media

DTIC Science & Technology

2009-01-01

100 to 300 m/s for sandy sediments with porosities of 40-50%. Hastrup [13:121-127] reports empirical relationships that relative speed ratios 1.0 ≤ cb...Eby, "Acoustic attenuation in a liquid layer over a "slow" viscoelastic solid", J. Acoust. Soc. Amer. 3496), 836-843, 1962 [13] O. F. Hastrup

Mercury toxicity in the aquatic oligochaete Sparganophilus pearsei: I. Variation in resistance among populations.

PubMed

Vidal, D E; Horne, A J

2003-08-01

Mercury contamination has become a problem in many San Francisco Bay Area watersheds due to its elevated presence in sediments and aquatic organisms. The present study used laboratory lethal toxicity (LC50) tests to examine the mercury tolerance of aquatic oligochaete worms, Sparganophilus pearsei, from contaminated and uncontaminated areas. The oligochaetes were collected in the following fresh water reservoirs: Sandy Wool (reference area), San Pablo, Lake Anza, Lake Herman, and Guadalupe. These last four reservoirs were contaminated with levels of mercury that ranged from 1.5 to 2 mg/kg (wet weight). Mercury concentrations in sediment and tissue from Sandy Wool were below detection limits and worms from this site were the least tolerant of mercury in laboratory exposures (LC50 = 0.22 mg/L). Worms from the other, more contaminated, reservoirs contained elevated tissue mercury concentrations and were more tolerant in laboratory tests (LC50 = 1.48-2.19 mg/L). The present study demonstrates that different populations of the aquatic oligochaete S. pearsei have developed different tolerances to mercury depending on their previous history of exposure to mercury contamination.

Directional Analysis of the Storm Surge from Hurricane Sandy 2012, with Applications to Charleston, New Orleans, and the Philippines

PubMed Central

Drews, Carl; Galarneau, Thomas J.

2015-01-01

Hurricane Sandy in late October 2012 drove before it a storm surge that rose to 4.28 meters above mean lower low water at The Battery in lower Manhattan, and flooded the Hugh L. Carey automobile tunnel between Brooklyn and The Battery. This study examines the surge event in New York Harbor using the Weather Research and Forecasting (WRF) atmospheric model and the Coupled-Ocean-Atmosphere-Wave- Sediment Transport / Regional Ocean Modeling System (COAWST/ROMS). We present a new technique using directional analysis to calculate and display maps of a coastline's potential for storm surge; these maps are constructed from wind fields blowing from eight fixed compass directions. This analysis approximates the surge observed during Hurricane Sandy. The directional analysis is then applied to surge events at Charleston, South Carolina, New Orleans, Louisiana, and Tacloban City, the Philippines. Emergency managers could use these directional maps to prepare their cities for an approaching storm, on planning horizons from days to years. PMID:25822480

Directional analysis of the storm surge from Hurricane Sandy 2012, with applications to Charleston, New Orleans, and the Philippines.

PubMed

Drews, Carl; Galarneau, Thomas J

2015-01-01

Hurricane Sandy in late October 2012 drove before it a storm surge that rose to 4.28 meters above mean lower low water at The Battery in lower Manhattan, and flooded the Hugh L. Carey automobile tunnel between Brooklyn and The Battery. This study examines the surge event in New York Harbor using the Weather Research and Forecasting (WRF) atmospheric model and the Coupled-Ocean-Atmosphere-Wave- Sediment Transport/Regional Ocean Modeling System (COAWST/ROMS). We present a new technique using directional analysis to calculate and display maps of a coastline's potential for storm surge; these maps are constructed from wind fields blowing from eight fixed compass directions. This analysis approximates the surge observed during Hurricane Sandy. The directional analysis is then applied to surge events at Charleston, South Carolina, New Orleans, Louisiana, and Tacloban City, the Philippines. Emergency managers could use these directional maps to prepare their cities for an approaching storm, on planning horizons from days to years.

Soil characteristics of sediment-amended baldcypress (Taxodium distichum) swamps of coastal Louisiana

USGS Publications Warehouse

Jiang, Ming; Middleton, Beth A.

2011-01-01

Amendments of sediment from dredging activities have played an important role in raising the elevation of sinking coastal wetlands. This study compared the soil characteristics of sediment- amended coastal swamps in the Barataria Preserve unit of Jean Lafitte National Historical Park and Preserve with natural swamps along Bayou des Familles. The sandy sediment amendments used in the coastal forests had different soil texture and characteristics than the more organic soils of the natural swamps. Three years after the application of these sediments on the sediment-amended swamps, dewatering and compaction of the sediment had occurred but the sediment still had high salinity and bulk density, and low organic matter content. The two sediment-amended swamps differed from each other in that Site 1 had a higher elevation (mean = 25 cm higher) and drier soil than Site 2. The effects of sediment in coastal forested wetlands require separate consideration from studies of salt marshes, e.g., the weight of the sediment might damage tree roots, or the amendments might influence soil stability during storms in a different way. Generally, this study suggests that shallower depths of sediment are more likely to yield environments beneficial to these sinking baldcypress swamps in coastal Louisiana.

Benthic exchange and biogeochemical cycling in permeable sediments.

PubMed

Huettel, Markus; Berg, Peter; Kostka, Joel E

2014-01-01

The sandy sediments that blanket the inner shelf are situated in a zone where nutrient input from land and strong mixing produce maximum primary production and tight coupling between water column and sedimentary processes. The high permeability of the shelf sands renders them susceptible to pressure gradients generated by hydrodynamic and biological forces that modulate spatial and temporal patterns of water circulation through these sediments. The resulting dynamic three-dimensional patterns of particle and solute distribution generate a broad spectrum of biogeochemical reaction zones that facilitate effective decomposition of the pelagic and benthic primary production products. The intricate coupling between the water column and sediment makes it challenging to quantify the production and decomposition processes and the resultant fluxes in permeable shelf sands. Recent technical developments have led to insights into the high biogeochemical and biological activity of these permeable sediments and their role in the global cycles of matter.

Ecological periodic tables for benthic macrofaunal usage of estuarine habitats: Insights from a case study in Tillamook Bay, Oregon, USA

NASA Astrophysics Data System (ADS)

Ferraro, Steven P.; Cole, Faith A.

2012-05-01

This study validates the ecological relevance of estuarine habitat types to the benthic macrofaunal community and, together with previous similar studies, suggests they can serve as elements in ecological periodic tables of benthic macrofaunal usage in the bioregion. We compared benthic macrofaunal Bray-Curtis similarity and the means of eight benthic macrofaunal community measures across seven habitat types in Tillamook Bay, Oregon, USA: intertidal eelgrass (Zostera marina), dwarf eelgrass (Zostera japonica), oyster (Crassostrea gigas) ground culture, burrowing mud shrimp (Upogebia pugettensis), burrowing ghost shrimp (Neotrypaea californiensis), sand and subtidal. Benthic macrofaunal Bray-Curtis similarity differed among all the habitats except ghost shrimp and sand. The habitat rank order on mean benthic macrofaunal species richness, abundance and biomass was dwarf eelgrass ≈ oyster ≥ mud shrimp ≈ eelgrass > sand ≈ ghost shrimp ≈ subtidal. The benthic macrofaunal habitat usage pattern in Tillamook Bay was, with a few exceptions, similar to that in two other US Pacific Northwest estuaries. The exceptions indicate variants of eelgrass and ghost shrimp habitat that differ in benthic macrofaunal usage perhaps due to differences in the coarseness of the sand fraction of the sediments in which they live. The similarities indicate periodic benthic macrofaunal usage patterns across the other habitat types extend over a wider geographic scale and range of environmental conditions than previously known.

Linking macrobenthic communities structure and zonation patterns on sandy shores: Mapping tool toward management and conservation perspectives in Northern France

NASA Astrophysics Data System (ADS)

Rolet, Céline; Spilmont, Nicolas; Dewarumez, Jean-Marie; Luczak, Christophe

2015-05-01

In a context of intensifying anthropogenic pressures on sandy shores, the mapping of benthic habitat appears as an essential first step and a fundamental baseline for marine spatial planning, ecosystem-based management and conservation efforts of soft-sediment intertidal areas. Mapping allows representing intertidal habitats that are basically characterised by abiotic (e.g sediments, exposure to waves…) and biotic factors such as macrobenthic communities. Macrobenthic communities are known to show zonation patterns across sandy beaches and many studies highlighted the existence of three biological zones. We tested this general model of a tripartite biological division of the shore at a geographical scale of policy, conservation and management decisions (i.e. Northern France coastline), using multivariate analyses combined with the Direct Field Observation (DFO) method. From the upper to the lower shores, the majority of the beaches exhibited three macrobenthic communities confirming the existence of the tripartite biological division of the shore. Nevertheless, in some cases, two or four zones were found: (1) two zones when the drying zone located on the upper shore was replaced by littoral rock or engineering constructions and (2) four zones on beaches and estuaries where a muddy-sand community occurred from the drift line to the mid shore. The correspondence between this zonation pattern of macrobenthic communities and the EUNIS habitat classification was investigated and the results were mapped to provide a reference state of intertidal soft-sediment beaches and estuaries. Our results showed evidence of the applicability of this EUNIS typology for the beaches and estuaries at a regional scale (Northern France coastline) with a macroecological approach. In order to fulfil the requirements of the European Directives (WFD and MFSD), this mapping appears as a practical tool for any functional study on these coastal ecosystems, for the monitoring of anthropogenic activities and for the implementation of management plans concerning effective conservation strategies.

Devastating Transboundary Impacts of Sea Star Wasting Disease on Subtidal Asteroids.

PubMed

Montecino-Latorre, Diego; Eisenlord, Morgan E; Turner, Margaret; Yoshioka, Reyn; Harvell, C Drew; Pattengill-Semmens, Christy V; Nichols, Janna D; Gaydos, Joseph K

2016-01-01

Sea star wasting disease devastated intertidal sea star populations from Mexico to Alaska between 2013-15, but little detail is known about its impacts to subtidal species. We assessed the impacts of sea star wasting disease in the Salish Sea, a Canadian / United States transboundary marine ecosystem, and world-wide hotspot for temperate asteroid species diversity with a high degree of endemism. We analyzed roving diver survey data for the three most common subtidal sea star species collected by trained volunteer scuba divers between 2006-15 in 5 basins and on the outer coast of Washington, as well as scientific strip transect data for 11 common subtidal asteroid taxa collected by scientific divers in the San Juan Islands during the spring/summer of 2014 and 2015. Our findings highlight differential susceptibility and impact of sea star wasting disease among asteroid species populations and lack of differences between basins or on Washington's outer coast. Specifically, severe depletion of sunflower sea stars (Pycnopodia helianthoides) in the Salish Sea support reports of major declines in this species from California to Alaska, raising concern for the conservation of this ecologically important subtidal predator.

Devastating Transboundary Impacts of Sea Star Wasting Disease on Subtidal Asteroids

PubMed Central

Montecino-Latorre, Diego; Eisenlord, Morgan E.; Turner, Margaret; Yoshioka, Reyn; Harvell, C. Drew; Pattengill-Semmens, Christy V.; Nichols, Janna D.

2016-01-01

Sea star wasting disease devastated intertidal sea star populations from Mexico to Alaska between 2013–15, but little detail is known about its impacts to subtidal species. We assessed the impacts of sea star wasting disease in the Salish Sea, a Canadian / United States transboundary marine ecosystem, and world-wide hotspot for temperate asteroid species diversity with a high degree of endemism. We analyzed roving diver survey data for the three most common subtidal sea star species collected by trained volunteer scuba divers between 2006–15 in 5 basins and on the outer coast of Washington, as well as scientific strip transect data for 11 common subtidal asteroid taxa collected by scientific divers in the San Juan Islands during the spring/summer of 2014 and 2015. Our findings highlight differential susceptibility and impact of sea star wasting disease among asteroid species populations and lack of differences between basins or on Washington’s outer coast. Specifically, severe depletion of sunflower sea stars (Pycnopodia helianthoides) in the Salish Sea support reports of major declines in this species from California to Alaska, raising concern for the conservation of this ecologically important subtidal predator. PMID:27783620

Potential linkage between sediment oxygen demand and pore water chemistry in weir-impounded rivers.

PubMed

Lee, Mi-Hee; Jung, Heon-Jae; Kim, Sung-Han; An, Sung-Uk; Choi, Jung Hyun; Lee, Hyo-Jin; Huh, In-Ae; Hur, Jin

2018-04-01

Due to recent weir construction on four major rivers in South Korea, sediment has accumulated in the river bottom near the weirs, which has in turn raised concerns over the quality of overlying water. In this study, the seasonal and spatial variations of sediment oxygen demand (SOD) and the influencing factors were explored using pore water chemistry for the weir-impounded rivers. Muddy and sandy sediment samples were taken from 24 different sites along the four major rivers in summer and autumn, 2016. The SOD was measured in a laboratory based on 10-hour incubation at in situ temperature. The measured pore water chemistry included the concentrations of dissolved organic carbon (DOC), total dissolved nitrogen (TDN), inorganic nitrogen (NH 3 -N, NO 3 -N, NO 2 -N), and phosphate phosphorous (PO 4 -P), and the optical properties from UV absorption spectra and fluorescence excitation-emission matrixes coupled with parallel factor analysis (EEM-PARAFAC). Significant differences in SOD values between muddy and sandy sediments were found only in summer (p=0.047). The higher SOD in summer versus autumn (p=0.015) was attributed to seasonal temperature differences. The higher NH 3 -N and the lower NO 3 -N of the pore water samples in summer versus autumn suggested that organic nitrogen decomposition via an ammonification and nitrification process could operate as an important factor for the SOD variations in summer and autumn, respectively. Principal component analysis revealed the mutual contributions of nitrogen-associated processes and the organic composition in pore water to increasing SOD levels. NH 3 -N in sediment pore water alone could be a good predictor for SOD. However, multiple regression analysis using NH 3 -N, fluorescence index and terrestrial humic-like components improved the estimation capability for SOD variations. Copyright © 2017 Elsevier B.V. All rights reserved.

Transport behavior of groundwater protozoa and protozoan-sized microspheres in sandy aquifer sediments

USGS Publications Warehouse

Harvey, R.W.; Kinner, N.E.; Bunn, A.; MacDonald, D.; Metge, D.

1995-01-01

Transport behaviors of unidentified flagellated protozoa (flagellates) and flagellate-sized carboxylated microspheres in sandy, organically contaminated aquifer sediments were investigated in a small-scale (1 to 4-m travel distance) natural-gradient tracer test on Cape Cod and in flow-through columns packed with sieved (0.5-to 1.0-mm grain size) aquifer sediments. The minute (average in situ cell size, 2 to 3 ??m) flagellates, which are relatively abundant in the Cape Cod aquifer, were isolated from core samples, grown in a grass extract medium, labeled with hydroethidine (a vital eukaryotic stain), and coinjected into aquifer sediments along with bromide, a conservative tracer. The 2-??m flagellates appeared to be near the optimal size for transport, judging from flowthrough column experiments involving a polydispersed (0.7 to 6.2 ??m in diameter) suspension of carboxylated microspheres. However, immobilization within the aquifer sediments accounted for a log unit reduction over the first meter of travel compared with a log unit reduction over the first 10 m of travel for indigenous, free-living groundwater bacteria in earlier tests. High rates of flagellate immobilization in the presence of aquifer sediments also was observed in the laboratory. However, immobilization rates for the laboratory-grown flagellates (initially 4 to 5 ??m) injected into the aquifer were not constant and decreased noticeably with increasing time and distance of travel. The decrease in propensity for grain surfaces was accompanied by a decrease in cell size, as the flagellates presumably readapted to aquifer conditions. Retardation and apparent dispersion were generally at least twofold greater than those observed earlier for indigenous groundwater bacteria but were much closer to those observed for highly surface active carboxylated latex microspheres. Field and laboratory results suggest that 2- ??m carboxylated microspheres may be useful as analogs in investigating several abiotic aspects of flagellate transport behavior in groundwater.

Numerical Modeling of Geomorphic Change on Sandy Coasts as a Function of Changing Wave Climate

NASA Astrophysics Data System (ADS)

Adams, P. N.; McNamara, D.; Murray, A. B.; Lovering, J.

2009-12-01

Climate change is expected to affect sandy coast geomorphology through two principal mechanisms: (1) sea level rise, which affects cross-shore sediment transport tending to drive shoreline retreat, and (2) alteration of statistical distributions in ocean storm wave climate (deep water wave height, period, and direction), which affects longshore sediment transport gradients that result in shoreline erosion and accretion. To address potential climate change-driven effects on longshore sediment transport gradients, we are developing techniques to link various numerical models of wave transformation with several different longshore sediment transport formulae in accordance with the Community Surface Dynamics Modeling System (CSDMS) project. Results of the various wave transformation models are compared to field observations of cross-shelf wave transformation along the North Florida Atlantic coast for purposes of model verification and calibration. Initial comparisons between wave-transformation methods (assumption of shore-parallel contours, simple wave ray tracing, and the SWAN spectral wave model) on artificially constructed continental shelves reveal an increasing discrepancy of results for increasing complexity of shelf bathymetry. When the more advanced SWAN spectral wave model is coupled with a simple CERC-type formulation of longshore sediment transport and applied to a real coast with complex offshore shoals (Cape Canaveral region of the North Florida Atlantic Coast), the patterns of erosion and accretion agree with results of the simplest wave-propagation models for some wave conditions, but disagree in others. Model simulations in which wave height and period are held constant show that locations of divergence and convergence of sediment flux shift with deep water wave-approach angle in ways that would not always be predicted using less sophisticated wave propagation models. Thus, predicting long-term local shoreline change on actual coastlines featuring complex bathymetry requires the extra computational effort to run the more advanced model over a wide range of wave conditions.

A simple model for calculating tsunami flow speed from tsunami deposits

USGS Publications Warehouse

Jaffe, B.E.; Gelfenbuam, G.

2007-01-01

This paper presents a simple model for tsunami sedimentation that can be applied to calculate tsunami flow speed from the thickness and grain size of a tsunami deposit (the inverse problem). For sandy tsunami deposits where grain size and thickness vary gradually in the direction of transport, tsunami sediment transport is modeled as a steady, spatially uniform process. The amount of sediment in suspension is assumed to be in equilibrium with the steady portion of the long period, slowing varying uprush portion of the tsunami. Spatial flow deceleration is assumed to be small and not to contribute significantly to the tsunami deposit. Tsunami deposits are formed from sediment settling from the water column when flow speeds on land go to zero everywhere at the time of maximum tsunami inundation. There is little erosion of the deposit by return flow because it is a slow flow and is concentrated in topographic lows. Variations in grain size of the deposit are found to have more effect on calculated tsunami flow speed than deposit thickness. The model is tested using field data collected at Arop, Papua New Guinea soon after the 1998 tsunami. Speed estimates of 14??m/s at 200??m inland from the shoreline compare favorably with those from a 1-D inundation model and from application of Bernoulli's principle to water levels on buildings left standing after the tsunami. As evidence that the model is applicable to some sandy tsunami deposits, the model reproduces the observed normal grading and vertical variation in sorting and skewness of a deposit formed by the 1998 tsunami.

Natural occurrence of microbial sulphur oxidation by long-range electron transport in the seafloor

PubMed Central

Malkin, Sairah Y; Rao, Alexandra MF; Seitaj, Dorina; Vasquez-Cardenas, Diana; Zetsche, Eva-Maria; Hidalgo-Martinez, Silvia; Boschker, Henricus TS; Meysman, Filip JR

2014-01-01

Recently, a novel mode of sulphur oxidation was described in marine sediments, in which sulphide oxidation in deeper anoxic layers was electrically coupled to oxygen reduction at the sediment surface. Subsequent experimental evidence identified that long filamentous bacteria belonging to the family Desulfobulbaceae likely mediated the electron transport across the centimetre-scale distances. Such long-range electron transfer challenges some long-held views in microbial ecology and could have profound implications for sulphur cycling in marine sediments. But, so far, this process of electrogenic sulphur oxidation has been documented only in laboratory experiments and so its imprint on the seafloor remains unknown. Here we show that the geochemical signature of electrogenic sulphur oxidation occurs in a variety of coastal sediment environments, including a salt marsh, a seasonally hypoxic basin, and a subtidal coastal mud plain. In all cases, electrogenic sulphur oxidation was detected together with an abundance of Desulfobulbaceae filaments. Complementary laboratory experiments in intertidal sands demonstrated that mechanical disturbance by bioturbating fauna destroys the electrogenic sulphur oxidation signal. A survey of published geochemical data and 16S rRNA gene sequences identified that electrogenic sulphide oxidation is likely present in a variety of marine sediments with high sulphide generation and restricted bioturbation, such as mangrove swamps, aquaculture areas, seasonally hypoxic basins, cold sulphide seeps and possibly hydrothermal vent environments. This study shows for the first time that electrogenic sulphur oxidation occurs in a wide range of marine sediments and that bioturbation may exert a dominant control on its natural distribution. PMID:24671086

Natural occurrence of microbial sulphur oxidation by long-range electron transport in the seafloor.

PubMed

Malkin, Sairah Y; Rao, Alexandra M F; Seitaj, Dorina; Vasquez-Cardenas, Diana; Zetsche, Eva-Maria; Hidalgo-Martinez, Silvia; Boschker, Henricus T S; Meysman, Filip J R

2014-09-01

Recently, a novel mode of sulphur oxidation was described in marine sediments, in which sulphide oxidation in deeper anoxic layers was electrically coupled to oxygen reduction at the sediment surface. Subsequent experimental evidence identified that long filamentous bacteria belonging to the family Desulfobulbaceae likely mediated the electron transport across the centimetre-scale distances. Such long-range electron transfer challenges some long-held views in microbial ecology and could have profound implications for sulphur cycling in marine sediments. But, so far, this process of electrogenic sulphur oxidation has been documented only in laboratory experiments and so its imprint on the seafloor remains unknown. Here we show that the geochemical signature of electrogenic sulphur oxidation occurs in a variety of coastal sediment environments, including a salt marsh, a seasonally hypoxic basin, and a subtidal coastal mud plain. In all cases, electrogenic sulphur oxidation was detected together with an abundance of Desulfobulbaceae filaments. Complementary laboratory experiments in intertidal sands demonstrated that mechanical disturbance by bioturbating fauna destroys the electrogenic sulphur oxidation signal. A survey of published geochemical data and 16S rRNA gene sequences identified that electrogenic sulphide oxidation is likely present in a variety of marine sediments with high sulphide generation and restricted bioturbation, such as mangrove swamps, aquaculture areas, seasonally hypoxic basins, cold sulphide seeps and possibly hydrothermal vent environments. This study shows for the first time that electrogenic sulphur oxidation occurs in a wide range of marine sediments and that bioturbation may exert a dominant control on its natural distribution.

Sediment resuspension in a shallow lake with muddy substrates: St Lucia, South Africa

NASA Astrophysics Data System (ADS)

Zikhali, Vulindlela; Tirok, Katrin; Stretch, Derek

2015-10-01

Wind-driven sediment resuspension affects the physical and biological environment of the water column in shallow estuarine lakes. This study investigated the relationship between wind-driven waves and suspended sediment concentration (SSC) using the 33 km2 South Lake basin of Lake St Lucia, South Africa as a case study. Five wave poles measuring significant wave height and turbidity were deployed over an aggregate period of twenty days at distributed locations where sediment substrate compositions varied from muddy to sandy and depths ranged from 0.7 m to 2.1 m. The resulting turbidity dynamics were used to test a simple depth-averaged model of suspended sediment concentrations. The model performed best in the muddy regions of the lake and was able to simulate the resuspension dynamics more accurately than the settling dynamics. Peak suspended sediment concentration levels were best captured for the deeper muddy locations. The model provides a means to make spatially explicit predictions of suspended sediment concentrations that can be used to understand the forcing mechanisms for primary producer growth and distribution or to improve sediment budget calculations.

Heterogeneous distribution in sediments and dispersal in waters of Alexandrium minutum in a semi-enclosed coastal ecosystem.

PubMed

Klouch, Z K; Caradec, F; Plus, M; Hernández-Fariñas, T; Pineau-Guillou, L; Chapelle, A; Schmitt, S; Quéré, J; Guillou, L; Siano, R

2016-12-01

Within the framework of research aimed at using genetic methods to evaluate harmful species distribution and their impact on coastal ecosystems, a portion of the ITS1rDNA of Alexandrium minutum was amplified by real-time PCR from DNA extracts of superficial (1-3cm) sediments of 30 subtidal and intertidal stations of the Bay of Brest (Brittany, France), during the winters of 2013 and 2015. Cell germinations and rDNA amplifications of A. minutum were obtained for sediments of all sampled stations, demonstrating that the whole bay is currently contaminated by this toxic species. Coherent estimations of ITS1rDNA copy numbers were obtained for the two sampling cruises, supporting the hypothesis of regular accumulation of A. minutum resting stages in the south-eastern, more confined embayments of the study area, where fine-muddy sediments are also more abundant. Higher ITS1rDNA copy numbers were detected in sediments of areas where blooms have been seasonally detected since 2012. This result suggests that specific genetic material estimations in superficial sediments of the bay may be a proxy of the cyst banks of A. minutum. The simulation of particle trajectory analyses by a Lagrangian physical model showed that blooms occurring in the south-eastern part of the bay are disconnected from those of the north-eastern zone. The heterogeneous distribution of A. minutum inferred from both water and sediment suggests the existence of potential barriers for the dispersal of this species in the Bay of Brest and encourages finer analyses at the population level for this species within semi-enclosed coastal ecosystems. Copyright © 2016 Elsevier B.V. All rights reserved.

Composition and depth distribution of hydrocarbons in Barataria Bay marsh sediments after the Deepwater Horizon oil spill.

PubMed

Dincer Kırman, Zeynep; Sericano, José L; Wade, Terry L; Bianchi, Thomas S; Marcantonio, Franco; Kolker, Alexander S

2016-07-01

In 2010, an estimate 4.1 million barrels of oil were accidentally released into the Gulf of Mexico (GoM) during the Deepwater Horizon (DWH) Oil Spill. One and a half years after this incident, a set of subtidal and intertidal marsh sediment cores were collected from five stations in Barataria Bay, Louisiana, USA, and analyzed to determine the spatial and vertical distributions and source of hydrocarbon residues based on their chemical composition. An archived core, collected before the DWH oil spill from the same area, was also analyzed to assess the pre-spill hydrocarbon distribution in the area. Analyses of aliphatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs) and stable carbon isotope showed that the distribution of petroleum hydrocarbons in Barataria Bay was patchy and limited in areal extent. Significant TPH and ΣPAH concentrations (77,399 μg/g and 219,065 ng/g, respectively) were detected in the surface sediments of one core (i.e., core A) to a depth of 9 cm. Based on a sedimentation rate of 0.39 cm yr(-1), determined using (137)Cs, the presence of anthropogenic hydrocarbons in these sediment core deposited ca. 50 to 60 years ago. The historical background hydrocarbon concentrations increased significantly at the sediment surface and can be attributed to recent inputs. Although the oil present in the bay's sediments has undergone moderate weathering, biomarker analyses performed on core A samples likely indicated the presence of hydrocarbons from the DWH oil spill. The effects of oiling events on Barataria Bay and other marsh ecosystems in this region remain uncertain, as oil undergoes weathering changes over time. Copyright © 2016 Elsevier Ltd. All rights reserved.

Inferring tidal wetland stability from channel sediment fluxes: observations and a conceptual model

USGS Publications Warehouse

Ganju, Neil K.; Nidzieko, Nicholas J.; Kirwan, Matthew L.

2013-01-01

Anthropogenic and climatic forces have modified the geomorphology of tidal wetlands over a range of timescales. Changes in land use, sediment supply, river flow, storminess, and sea level alter the layout of tidal channels, intertidal flats, and marsh plains; these elements define wetland complexes. Diagnostically, measurements of net sediment fluxes through tidal channels are high-temporal resolution, spatially integrated quantities that indicate (1) whether a complex is stable over seasonal timescales and (2) what mechanisms are leading to that state. We estimated sediment fluxes through tidal channels draining wetland complexes on the Blackwater and Transquaking Rivers, Maryland, USA. While the Blackwater complex has experienced decades of degradation and been largely converted to open water, the Transquaking complex has persisted as an expansive, vegetated marsh. The measured net export at the Blackwater complex (1.0 kg/s or 0.56 kg/m2/yr over the landward marsh area) was caused by northwesterly winds, which exported water and sediment on the subtidal timescale; tidally forced net fluxes were weak and precluded landward transport of suspended sediment from potential seaward sources. Though wind forcing also exported sediment at the Transquaking complex, strong tidal forcing and proximity to a turbidity maximum led to an import of sediment (0.031 kg/s or 0.70 kg/m2/yr). This resulted in a spatially averaged accretion of 3.9 mm/yr, equaling the regional relative sea level rise. Our results suggest that in areas where seaward sediment supply is dominant, seaward wetlands may be more capable of withstanding sea level rise over the short term than landward wetlands. We propose a conceptual model to determine a complex's tendency toward stability or instability based on sediment source, wetland channel location, and transport mechanisms. Wetlands with a reliable portfolio of sources and transport mechanisms appear better suited to offset natural and anthropogenic loss.

A comparison of acoustic and observed sediment classifications as predictor variables for modelling biotope distributions in Galway Bay, Ireland

NASA Astrophysics Data System (ADS)

O'Carroll, Jack P. J.; Kennedy, Robert; Ren, Lei; Nash, Stephen; Hartnett, Michael; Brown, Colin

2017-10-01

The INFOMAR (Integrated Mapping For the Sustainable Development of Ireland's Marine Resource) initiative has acoustically mapped and classified a significant proportion of Ireland's Exclusive Economic Zone (EEZ), and is likely to be an important tool in Ireland's efforts to meet the criteria of the MSFD. In this study, open source and relic data were used in combination with new grab survey data to model EUNIS level 4 biotope distributions in Galway Bay, Ireland. The correct prediction rates of two artificial neural networks (ANNs) were compared to assess the effectiveness of acoustic sediment classifications versus sediments that were visually classified by an expert in the field as predictor variables. To test for autocorrelation between predictor variables the RELATE routine with Spearman rank correlation method was used. Optimal models were derived by iteratively removing predictor variables and comparing the correct prediction rates of each model. The models with the highest correct prediction rates were chosen as optimal. The optimal models each used a combination of salinity (binary; 0 = polyhaline and 1 = euhaline), proximity to reef (binary; 0 = within 50 m and 1 = outside 50 m), depth (continuous; metres) and a sediment descriptor (acoustic or observed) as predictor variables. As the status of benthic habitats is required to be assessed under the MSFD the Ecological Status (ES) of the subtidal sediments of Galway Bay was also assessed using the Infaunal Quality Index. The ANN that used observed sediment classes as predictor variables could correctly predict the distribution of biotopes 67% of the time, compared to 63% for the ANN using acoustic sediment classes. Acoustic sediment ANN predictions were affected by local sediment heterogeneity, and the lack of a mixed sediment class. The all-round poor performance of ANNs is likely to be a result of the temporally variable and sparsely distributed data within the study area.

Effects of mud sedimentation on lugworm ecosystem engineering

NASA Astrophysics Data System (ADS)

Montserrat, F.; Suykerbuyk, W.; Al-Busaidi, R.; Bouma, T. J.; van der Wal, D.; Herman, P. M. J.

2011-01-01

Benthic ecosystem engineering organisms attenuate hydrodynamic or biogeochemical stress to ameliorate living conditions. Bioturbating infauna, like the lugworm Arenicola marina, determine intertidal process dynamics by maintaining the sediment oxygenated and sandy. Maintaining the permeability of the surrounding sediment enables them to pump water through the interstitial spaces, greatly increasing the oxygen availability. In a field experiment, both lugworm presence and siltation regime were manipulated to investigate to what extent lugworms are able to cope with sedimentation of increasing mud percentage and how this would affect its ecosystem engineering. Fluorescent tracers were added to experimentally deposited mud to visualise bioturbation effects on fine sediment fractions. Lugworm densities were not affected by an increasing mud percentage in experimentally deposited sediment. Negative effects are expected to occur under deposition with significantly higher mud percentages. Surface chlorophyll a content was a function of experimental mud percentage, with no effect of lugworm bioturbation. Surface roughness and sediment permeability clearly increased by lugworm presence, whereas sediment erosion threshold was not significantly affected by lugworms. The general idea that A. marina removes fine sediment fractions from the bed could not be confirmed. Rather, the main ecosystem engineering effect of A. marina is hydraulic destabilisation of the sediment matrix.

Larval Behaviours and Their Contribution to the Distribution of the Intertidal Coral Reef Sponge Carteriospongia foliascens

PubMed Central

Abdul Wahab, Muhammad Azmi; de Nys, Rocky; Webster, Nicole; Whalan, Steve

2014-01-01

Sponges (Phylum Porifera) are an evolutionary and ecologically significant group; however information on processes influencing sponge population distributions is surprisingly limited. Carteriospongia foliascens is a common Indo-Pacific sponge, which has been reported from the intertidal to the mesophotic. Interestingly, the distribution of C. foliascens at inshore reefs of the Great Barrier Reef is restricted to the intertidal with no individuals evident in adjacent subtidal habitats. The abundance of C. foliascens and substrate availability was first quantified to investigate the influence of substrate limitation on adult distribution. Pre-settlement processes of larval spawning, swimming speeds, phototaxis, vertical migration, and settlement to intertidal and subtidal substrate cues were also quantified. Notably, suitable settlement substrate (coral rubble) was not limiting in subtidal habitats. C. foliascens released up to 765 brooded larvae sponge−1 day−1 during the day, with larvae (80%±5.77) being negatively phototactic and migrating to the bottom within 40 minutes from release. Subsequently, larvae (up to 58.67%±2.91) migrated to the surface after the loss of the daylight cue (nightfall), and after 34 h post-release >98.67% (±0.67) of larvae had adopted a benthic habit regardless of light conditions. Intertidal and subtidal biofilms initiated similar settlement responses, inducing faster (as early 6 h post-release) and more successful metamorphosis (>60%) than unconditioned surfaces. C. foliascens has a high larval supply and larval behaviours that support recruitment to the subtidal. The absence of C. foliascens in subtidal habitats at inshore reefs is therefore proposed to be a potential consequence of post-settlement mortalities. PMID:24853091

Maps showing bathymetry and modern sediment thickness on the inner continental shelf offshore of Fire Island, New York, pre-Hurricane Sandy

USGS Publications Warehouse

Schwab, William C.; Denny, Jane F.; Baldwin, Wayne E.

2014-01-01

The U.S. Geological Survey mapped approximately 336 square kilometers of the lower shoreface and inner continental shelf offshore of Fire Island, New York, in 2011 by using interferometric sonar and high-resolution chirp seismic-reflection systems. This report presents maps of bathymetry, acoustic backscatter, the coastal plain unconformity, the Holocene marine transgressive surface, and modern sediment thickness. These spatial data support research on the Quaternary evolution of the Fire Island coastal system and provide baseline information for research on coastal processes along southern Long Island.

Coastal lake sediments reveal 5500 years of tsunami history in south central Chile

NASA Astrophysics Data System (ADS)

Kempf, Philipp; Moernaut, Jasper; Van Daele, Maarten; Vandoorne, Willem; Pino, Mario; Urrutia, Roberto; De Batist, Marc

2017-04-01

We present an exceptionally long and continuous coastal lacustrine record of ∼5500 years from Lake Huelde on the west coast of Chiloé Island in south central Chile. The study area is located within the rupture zone of the giant 1960 CE Great Chilean Earthquake (MW 9.5). The subsequent earthquake-induced tsunami inundated Lake Huelde and deposited mud rip-up clasts, massive sand and a mud cap in the lake. Long sediment cores from 8 core sites within Lake Huelde reveal 16 additional sandy layers in the 5500 year long record. The sandy layers share sedimentological similarities with the deposit of the 1960 CE tsunami and other coastal lake tsunami deposits elsewhere. On the basis of general and site-specific criteria we interpret the sandy layers as tsunami deposits. Age-control is provided by four different methods, 1) 210Pb-dating, 2) the identification of the 137Cs-peak, 3) an infrared stimulated luminescence (IRSL) date and 4) 22 radiocarbon dates. The ages of each tsunami deposit are modelled using the Bayesian statistic tools of OxCal and Bacon. The record from Lake Huelde matches the 8 regionally known tsunami deposits from documented history and geological evidence from the last ∼2000 years without over- or underrepresentation. We extend the existing tsunami history by 9 tsunami deposits. We discuss the advantages and disadvantages of various sedimentary environments for tsunami deposition and preservation, e.g. we find that Lake Huelde is 2-3 times less sensitive to relative sea-level change in comparison to coastal marshes in the same region.

Dynamic groundwater flows and geochemistry in a sandy nearshore aquifer over a wave event

NASA Astrophysics Data System (ADS)

Malott, Spencer; O'Carroll, Denis M.; Robinson, Clare E.

2016-07-01

Dynamic coastal forcing influences the transport of pollutants in nearshore aquifers and their ultimate flux to coastal waters. In this study, field data are presented that show, for the first time, the influence of a period of intensified wave conditions (wave event) on nearshore groundwater flows and geochemistry in a sandy beach. Field measurements at a freshwater beach allow wave effects to be quantified without other complex forcing that are present along marine shorelines (e.g., tides). Pressure transducer data obtained over an isolated wave event reveal the development of transient groundwater flow recirculations. The groundwater flows were simulated in FEFLOW using a phase-averaged wave setup approach to represent waves acting on the sediment-water interface. Comparison of measured and simulated data indicates that consideration of wave setup alone is able to adequately capture wave-induced perturbations in groundwater flows. While prior studies have shown sharp pH and redox spatial zonations in nearshore aquifers, this study reveals rapid temporal variations in conductivity, pH, and redox (ORP) in shallow sediments (up to 0.5 m depth) in response to varying wave conditions. Comparison of head gradients with calculated conductivity and pH mixing ratios indicates the controlling effect of the wave-induced water exchange and flows in driving the observed geochemical dynamics. While we are not able to conclusively determine the extent to which temporal variations are caused by conservative mixing versus reactive processes, the pH and ORP variations observed will have significant implications for the fate of reactive pollutants discharging through sandy nearshore aquifers.

Characterizing storm response and recovery using the beach change envelope: Fire Island, New York

USGS Publications Warehouse

Brenner, Owen T.; Lentz, Erika; Hapke, Cheryl J.; Henderson, Rachel; Wilson, Kathleen; Nelson, Timothy

2018-01-01

Hurricane Sandy at Fire Island, New York presented unique challenges in the quantification of storm impacts using traditional metrics of coastal change, wherein measured changes (shoreline, dune crest, and volume change) did not fully reflect the substantial changes in sediment redistribution following the storm. We used a time series of beach profile data at Fire Island, New York to define a new contour-based morphologic change metric, the Beach Change Envelope (BCE). The BCE quantifies changes to the upper portion of the beach likely to sustain measurable impacts from storm waves and capture a variety of storm and post-storm beach states. We evaluated the ability of the BCE to characterize cycles of beach change by relating it to a conceptual beach recovery regime, and demonstrated that BCE width and BCE height from the profile time series correlate well with established stages of recovery. We also investigated additional applications of this metric to capture impacts from storms and human modification by applying it to several post-storm historical datasets in which impacts varied considerably; Nor'Ida (2009), Hurricane Irene (2011), Hurricane Sandy (2012), and a 2009 community replenishment. In each case, the BCE captured distinctive upper beach morphologic change characteristic of these different beach building and erosional events. Analysis of the beach state at multiple profile locations showed spatial trends in recovery consistent with recent morphologic island evolution, which other studies have linked with sediment availability and the geologic framework. Ultimately we demonstrate a new way of more effectively characterizing beach response and recovery cycles to evaluate change along sandy coasts.

Revealing accumulation zones of plastic pellets in sandy beaches.

PubMed

Moreira, Fabiana T; Balthazar-Silva, Danilo; Barbosa, Lucas; Turra, Alexander

2016-11-01

Microplastics such as pellets are reported worldwide on sandy beaches, and have possible direct and indirect impacts on the biota and physical characteristics of the habitats where they accumulate. Evaluations of their standing stock at different spatial scales generate data on levels of contamination. This information is needed to identify accumulation zones and the specific beach habitats and communities that are likely to be most affected. Standing stocks of plastic pellets were evaluated in 13 sandy beaches in São Paulo state, Brazil. The sampling strategy incorporated across-shore transects from coastal dunes and backshores, and vertical profiles of the accumulated pellets down to 1 m depth below the sediment surface. Accumulation zones were identified at regional (among beaches) and local (between compartments) scales. At the regional scale pellet density tended to increase at beaches on the central and southwestern coast, near ports and factories that produce and transport the largest amounts of pellets in the country. At the local scale coastal dunes showed larger accumulations of pellets than backshores. For both compartments pellets tended to occur deeper in areas where standing stocks were larger. Most of the pellets were concentrated from the surface down to 0.4 m depth, suggesting that organisms inhabiting this part of the sediment column are more exposed to the risks associated with the presence of pellets. Our findings shed light on the local and regional scales of spatial variability of microplastics and their consequences for assessment and monitoring schemes in coastal compartments. Copyright © 2016. Published by Elsevier Ltd.

Characteristics of Holocene sediments in the Gunsan Basin, central Yellow Sea

NASA Astrophysics Data System (ADS)

Woo, H. J.; Huh, S.; Jeong, K. S.; Lee, J. H.; Ham, A.; Kang, J.

2016-12-01

The Gunsan Basin, in the eastern part of the South Yellow Sea Basin, is filled by terrestrial sedimentary rocks, maximally up to 8 km deep on the basement of metamorphic rocks that constitutes the Yangtze Platform. The uppermost sedimentary layer (generally less than 1 km) appears to have formed experiencing the repeated marine environments since the middle Miocene. This study is to investigate the characteristics of Holocene sediments in the Gunsan Basin, based on interpretation of core sediments and high-resolution shallow (Sparker and Chirp) seismic profiles. The surface sediments in the basin consist of sand (56.6% on the average), silt (18.4%), and clay (25.0%) with a mean grain size of 1.5 to 7.8 Ø. Sand is prevalent (63.8 to 98.3%) in and around the Yellow Sea Trough lying in the eastern part of the basin. The sandy sediments are regarded as relict sediments deposited in the last glacial maximum (LGM). The sedimentary environments are classified, based on the acoustic and morphological characters of high-resolution shallow (Sparker and Chirp) seismic profiles, into mud zone, deformed zone, and sand ridges with sand waves zone from the west to the east in the Gunsan Basin. The deformed zone in the central Yellow Sea is a mixing area of sediments derived from China and Korea, where there are a number of paleochannels and erosional surfaces in the direction of northwest-southeast. The deformed zone represents non-deposition or erosion in the central Yellow Sea during the Holocene. Tidal sand ridges and sand waves are well developed along the coast of Korea. Modern sand ridges are generally moving in the northeast-southwest direction, which coincide with dominant tidal current direction. Fifteen piston cores were collected in the basin to investigate the general geological characters of the marine sedimentary sequence. In comparison with three cores in the southern basin, the sand contents tend to increase in the direction of east. 14C dates from three cores near border of Exclusive Economic Zone (EEZ) of Korea reveal that Holocene sediments have accumulated at the rate 6-18 cm/ka. The mud sediments sequentially change sandy mud to mud after the sea-level rise. In the Gunsan Basin, paleochannels played an important role in sedimentary processes during low sea-level periods of Quaternary.

Sediment transport and mixing depth on a coral reef sand apron

NASA Astrophysics Data System (ADS)

Vila-Concejo, Ana; Harris, Daniel L.; Power, Hannah E.; Shannon, Amelia M.; Webster, Jody M.

2014-10-01

This paper investigates the mechanics of sediment transport on a subtidal sand apron located on a coral reef environment. In this environment 100% of the sediment is carbonate bioclasts generated in situ. The sand apron is located on the back reef and only affected by waves during high tides. It is commonly accepted in the literature that sand aprons are features that prograde lagoonwards and that most of the progradation occurs during high-energy events. Measurements of water depths, waves, currents and near bed suspended sediment concentrations (all at 10 Hz) on the sand apron were undertaken over a nine day intensive field campaign over both spring and neap tides; waves and tides were also measured in the lagoon. The topography and bathymetry of the sand apron were measured and mixing depth was obtained on three transects using depth of disturbance rods. We found that sediment transport on sand aprons is not solely restricted to high-energy events but occurs on a daily basis during spring tides. The main factor controlling the sediment transport was the water depth above the bed, with depths of 2-2.3 m allowing waves to promote the most sediment transport. This corresponds to a depth over the reef crest of 1.6-1.9 m. The second most important control was waves; transport was observed when Hs on the apron was 0.1 m or greater. In contrast, current magnitude was not a controlling mechanism for sediment entrainment but did affect sediment transport. The morphology of the sand apron was shown to affect the direction of currents with the currents also expected to influence the morphology of the sand apron. The currents measured during this field campaign were aligned with a shallow channel in the sand apron. Mixing depths were small (< 2.5 cm) yet they were larger than the values predicted by empirical formulae for gentle siliciclastic ocean beaches.

Origin of Amazon mudbanks along the northeastern coast of South America

USGS Publications Warehouse

Allison, M.A.; Lee, M.T.; Ogston, A.S.; Aller, R.C.

2000-01-01

Seismic profiles, sediment cores, and water column measurements were collected along the northeastern coast of Brazil to examine the origin of mudbanks in the Amazon coastal mud belt. These 10-60-km-long, shore-attached features previously had been observed to migrate along the 1200 km coast of the Guianas in response to wave forcing. CHIRP (3.5 kHz) seismic profiles of the shoreface and inner shelf located two mudbanks updrift of the previous eastern limit in French Guiana. 210Pb geochronology shows that these two banks are migrating to the northwest over a relict mud surface in 5-20 m water depth. The mudbanks are 3-4 m thick and are translating over a modern shoreface mud wedge deposited by previous mudbank passage in < 5 m water depth. Initial mudbank development is taking place on the intertidal and shallow subtidal mudflats at Cabo Cassipore, associated with an alongshore-accreting clinoform feature. Sediment trapping in this area is controlled by the nearshore presence of strong water column stratification produced by the enormous Amazon freshwater discharge on the shelf and by proximity to the Cassipore River estuary. Seasonal and decadal periods of sediment supply and starvation in this area likely are controlled by variations in northwest trade wind intensity. (C) 2000 Elsevier Science B.V.

Ecology of eelgrass meadows of the Atlantic Coast: a community profile

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

Thayer, G.W.; Kenworthy, W.J.; Fonseca, M.S.

1984-07-01

Eelgrass, Zostera marina, dominates the ecologically important but fragile seagrass communities along the east coast of the United States from North Carolina to Nova Scotia. Grasslike leaves and an extensive root and rhizome system enable eelgrass to exist in a shallow aquatic environment subject to waves, tides, and shifting sediments. Eelgrass meadows are highly productive, frequently rivaling agricultural croplands. They provide shelter and a rich variety of primary and secondary food resources, and form a nursery habitat for the life history stages of numerous fishery organisms. The leaves absorb and release nutrients, provide surfaces for attachment, reduce water current velocity,more » turbulence and scour, and promote accumulation of detritus. Rhizomes provide protection for benthic infauna and enhance sediment stability. Roots absorb and release nutrients to interstitial waters. Because of their shallow, subtidal existence, seagrasses are susceptible to perturbations of both the water column and sediments. Eelgrass meadows are impacted by dredging and filling, some commercial fishery harvest techniques, modification of normal temperature and salinity regimes, and addition of chemical wastes. Techniques have been developed to successfully restore eelgrass habitats, but a holistic approach to planning research and environmentally-related decisions is needed to avoid cumulative environmental impacts on these vital nursery areas. 64 figures, 16 tables.« less

Erosion patterns in a sediment layer

NASA Astrophysics Data System (ADS)

Daerr, Adrian; Lee, Peter; Lanuza, José; Clément, Éric

2003-06-01

We report here on a laboratory-scale experiment which reproduces a rich variety of natural patterns with few control parameters. In particular, we focus on intriguing rhomboid structures often found on sandy shores and flats. We show that the standard views based on water surface waves do not explain the phenomenon, and we evidence a different mechanism based on mud avalanche instability.

Phylogenetic tree of 16s rRNA sequences from sulfate-reducing bacteria in a sandy marine sediment

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

Devereux, R.; Mundfrom, G.W.

1994-01-01

Phylogenetic divergence among sulfate-reducing bateria in an estuarine sediment sample was investigated by PCR amplification and comparison of partial 16S rDNA sequences. Twenty unique 16S rDNA sequences were found, 12 from delta subclass bacteria based on overall sequence similarity (82-91%). Two successive PCR amplifications were used to obtain and clone the 16S rDNA. The first reaction used templates derived from phosphate-buffered saline washed sediment with primers designed to amplify nearly full-length bacterial domain 16S rDNA. A produce from a first reaction was used as template in a second reaction with primers designed to selectivity amplify a region of 16S rDNAmore » genes of sulfate-reducing bacteria. A phylogenetic tree incorporating the cloned sequences suggests the presence of yet to be cultivated lines of sulfate-reducing bacteria within the sediment sample.« less

Simulations of dredged sediment spreading on a Posidonia oceanica meadow off the Ligurian coast, Northwestern Mediterranean.

PubMed

Capello, M; Cutroneo, L; Ferranti, M P; Budillon, G; Bertolotto, R M; Ciappa, A; Cotroneo, Y; Castellano, M; Povero, P; Tucci, S

2014-02-15

The sandy deposits from dredging can have negative effects on the environment such as increase in suspended solids in the water column and their consequent transport. An experimental study was conducted to characterize water masses, dynamics, and sedimentation rates on the Ligurian continental shelf (Italy), where both a sand deposit, that could be used for beach nourishment, and a nearby Posidonia oceanica meadow coexist. The environmental plan provides a mathematical simulation of the sediment-dispersion to evaluate the possible impact on the meadow. It has been calculated that the dredging could double the concentration of suspended particles, but its scheduling will preclude a sediment accumulation. All the information obtained from this work will be used to study the environmental feasibility of the sand deposit exploitation and as starting point for drawing up the monitoring plan in case of dredging. Copyright © 2013 Elsevier Ltd. All rights reserved.

Sedimentology and geochemistry of mud volcanoes in the Anaximander Mountain Region from the Eastern Mediterranean Sea.

PubMed

Talas, Ezgi; Duman, Muhammet; Küçüksezgin, Filiz; Brennan, Michael L; Raineault, Nicole A

2015-06-15

Investigations carried out on surface sediments collected from the Anaximander mud volcanoes in the Eastern Mediterranean Sea to determine sedimentary and geochemical properties. The sediment grain size distribution and geochemical contents were determined by grain size analysis, organic carbon, carbonate contents and element analysis. The results of element contents were compared to background levels of Earth's crust. The factors that affect element distribution in sediments were calculated by the nine push core samples taken from the surface of mud volcanoes by the E/V Nautilus. The grain size of the samples varies from sand to sandy silt. Enrichment and Contamination factor analysis showed that these analyses can also be used to evaluate of deep sea environmental and source parameters. It is concluded that the biological and cold seep effects are the main drivers of surface sediment characteristics from the Anaximander mud volcanoes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Comparisons of microplastic pollution between mudflats and sandy beaches in Hong Kong.

PubMed

Lo, Hoi-Shing; Xu, Xiaoyu; Wong, Chun-Yuen; Cheung, Siu-Gin

2018-05-01

Most of the previous studies of microplastic pollution on coastal habitats focused on high energy beaches although low energy areas such as mudflats are supposed to retain more microplastics, not to mention that mudflats are biologically more diverse. We quantified and characterized microplastics from 10 mudflats and 10 sandy beaches in Hong Kong spanning from the eastern to western waters. Sediment samples were collected at 1.0 m and 1.5 m above chart datum (CD) and at the strandline. Abundance of microplastics ranged between 0.58 and 2116 items kg -1 sediment with that on mudflats being ten times more than on beaches. Polyethylene (46.9%) was the most abundant and followed by polypropylene (13.8%) and polyethylene terephthalate (13.5%). Expanded polystyrene was the most abundant in the strandline samples but not at 1.0 m and 1.5 m above CD. Although previous studies have concluded that the input from Pearl River is a major source of microplastics on Hong Kong shores, this study has demonstrated that the contribution of local pollution sources such as discharge from sewage treatment plants to microplastic pollution should not be neglected. Copyright © 2018 Elsevier Ltd. All rights reserved.

Modeling and measuring the relationships between sediment transport processes, alluvial bedforms and channel-scale morphodynamics in sandy braided rivers.

NASA Astrophysics Data System (ADS)

Nicholas, A. P.; Ashworth, P. J.; Best, J.; Lane, S. N.; Parsons, D. R.; Sambrook Smith, G.; Simpson, C.; Strick, R. J. P.; Unsworth, C. A.

2017-12-01

Recent years have seen significant advances in the development and application of morphodynamic models to simulate river evolution. Despite this progress, significant challenges remain to be overcome before such models can provide realistic simulations of river response to environmental change, or be used to determine the controls on alluvial channel patterns and deposits with confidence. This impasse reflects a wide range of factors, not least the fact that many of the processes that control river behaviour operate at spatial scales that cannot be resolved by such models. For example, sand-bed rivers are characterised by multiple scales of topography (e.g., dunes, bars, channels), the finest of which must often by parameterized, rather than represented explicitly in morphodynamic models. We examine these issues using a combination of numerical modeling and field observations. High-resolution aerial imagery and Digital Elevation Models obtained for the sandy braided South Saskatchewan River in Canada are used to quantify dune, bar and channel morphology and their response to changing flow discharge. Numerical simulations are carried out using an existing morphodynamic model based on the 2D shallow water equations, coupled with new parameterisations of the evolution and influence of alluvial bedforms. We quantify the spatial patterns of sediment flux using repeat images of dune migration and bar evolution. These data are used to evaluate model predictions of sediment transport and morphological change, and to assess the degree to which model performance is controlled by the parametrization of roughness and sediment transport phenomena linked to subgrid-scale bedforms (dunes). The capacity of such models to replicate the characteristic multi-scale morphology of bars in sand-bed rivers, and the contrasting morphodynamic signatures of braiding during low and high flow conditions, is also assessed.

Finescale turbulence and seabed scouring around pneumatophores in a wave-exposed mangrove forest

NASA Astrophysics Data System (ADS)

Mullarney, J. C.; Norris, B. K.; Henderson, S. M.; Bryan, K. R.

2015-12-01

Coastal mangroves provide a barrier between the coast and lower energy intertidal environments. The presence of mangrove roots (pneumatophores) alters local hydrodynamics by slowing currents, dissipating waves, enhancing within-canopy turbulence, and introducing significant spatial variability to the flow, particularly on the stem scale. To date, limited measurements exist within pneumatophore regions owing to the difficulties of measuring on sufficiently small scales. Hence, little is known about the turbulence controlling sediment transport within these regions. We report unique field observations near the seaward edge of a mangrove forest in the Mekong Delta, Vietnam. This forest is exposed to moderate wave energy (maximum heights of around 1 m), with waves observed to propagate and break up to 100 m inside the forest. Our measurements focus on a rapidly prograding area with a relatively sandy substrate and a gentle topographic slope. We resolved millimeter-scale turbulent flows within and above the pneumatophore canopy. Precise measurements of vegetation densities as a function of height were obtained using photogrammetry techniques. The dissipation rate of turbulent kinetic energy was enhanced at the canopy edge (ɛ ~ 10-4 W/kg), and decreased with distance into the forest (ɛ ~ 10-5 W/kg), although rates remained elevated above values measured on the tidal flat immediately offshore of the mangroves (ɛ ~ 10-6 W/kg). The dependence of turbulence on vegetation characteristics and on the stage of the tidal cycle is explored. The hydrodynamic measurements are then linked with changes in bathymetric features noted after a large wave event. Finer mud sediments were deposited outside the forest on the intertidal mudflat, whereas sandy sediments in the fringe region were significant scoured around regions of dense pneumatophores, and sediment mounds developed in the gaps between pneumatophores.

Assimilation of terrigenous organic matter via bacterial biomass as a food source for a brackish clam, Corbicula japonica (Mollusca: Bivalva)

NASA Astrophysics Data System (ADS)

Yamanaka, Toshiro; Mizota, Chitoshi; Maki, Yonosuke; Matsumasa, Masatoshi

2013-07-01

Corbicula japonica collected from the Kitakami River estuary, northeastern Japan, showed lower δ34S values in soft-body parts (+1.7 to +11.0‰) than the ambient seawater sulfate sulfur (+21‰), and this value gradually decreased at successive sites up to 15.8 km upstream from the river mouth. Previous study using carbon and nitrogen isotopes suggests that the bivalve nonselectively assimilates particulate organic matter of marine and terrestrial origin by filter feeding. This pattern in δ34S values may indicate a considerable contribution of a food source derived from terrigenous organic matter, which has low δ34S values close to 0‰, and the bivalve has been reported to have cellulase and hemicellulase activities. Unique fatty acids (iso 17:0 and anteiso 17:0 acids), both characteristic of sulfate-reducing bacteria, were observed in the salt-free, soft-body parts of the bivalve. The concentration of monounsaturated fatty acids, possibly derived from bacteria, was also high. Trace amounts of a polyunsaturated fatty acid (20:5ω3) specific to dinoflagellates were detected. In Corbicula habitats, reductive sandy layers with ample sulfides that were sporadically intercalated into the oxidative sandy sediment were often observed. The stable isotopic signatures of sediment sulfides (acid-volatile sulfide) and associated pore-water sulfates were -8.9 to +8.6‰ and +22.4 to +26.3‰, respectively, indicating the existence of bacterial sulfate-reducing activity and thiobios biomass. These isotopic signatures of the sediment, with the fatty acid composition of the bivalve, confirm the importance of a food source derived from bacteria belonging to the thiobios in the substrate sediments via pedal feeding, rather than direct digestion of terrigenous organic matter, in this estuarine ecosystem.

Impact of the Phaeocystis globosa spring bloom on the intertidal benthic compartment in the eastern English Channel: a synthesis.

PubMed

Spilmont, Nicolas; Denis, Lionel; Artigas, Luis Felipe; Caloin, Frédéric; Courcot, Lucie; Créach, Anne; Desroy, Nicolas; Gevaert, François; Hacquebart, Pascal; Hubas, Cédric; Janquin, Marie-Andrée; Lemoine, Yves; Luczak, Christophe; Migné, Aline; Rauch, Mathieu; Davoult, Dominique

2009-01-01

From 1999 to 2005, studies carried out in the frame of regional and national French programs aimed to determine whether the Phaeocystis globosa bloom affected the intertidal benthic communities of the French coast of the eastern English Channel in terms of composition and/or functioning. Study sites were chosen to cover most of the typical shore types encountered on this coast (a rocky shore, an exposed sandy beach and a small estuary). Both the presence of active Phaeocystis cells and their degradation product (foam) did have a significant impact on the studied shores. The primary production and growth rates of the kelp Saccharina latissima decreased during the bloom because of a shortage of light and nutrient for the macroalgae. On sandy sediments, the benthic metabolism (community respiration and community primary production), as well as the nitrification rate, were enhanced during foam deposits, in relation with the presence of bacteria and active pelagic cells within the decaying colonies. In estuarine sediments, the most impressive impact was the formation of a crust at the sediment surface due to drying foam. This led to anoxic conditions in the surface sediment and resulted in a high mortality among the benthic community. Some organisms also tended to migrate upward and were then directly accessible to the higher trophic level represented by birds. Phaeocystis then created a shortcut in the estuarine trophic network. Most of these modifications lasted shortly and all the systems considered came back to their regular properties and activities a few weeks after the end of the bloom, except for the most impacted estuarine area.

RESEARCH: Conceptualizing Environmental Stress: A Stress-Response Model of Coastal Sandy Barriers.

PubMed

Gabriel; Kreutzwiser

2000-01-01

/ The purpose of this paper is to develop and apply a conceptual framework of environmental stress-response for a geomorphic system. Constructs and methods generated from the literature were applied in the development of an integrative stress-response framework using existing environmental assessment techniques: interaction matrices and a systems diagram. Emphasis is on the interaction between environmental stress and the geomorphic environment of a sandy barrier system. The model illustrates a number of stress concepts pertinent to modeling environmental stress-response, including those related to stress-dependency, frequency-recovery relationships, environmental heterogeneity, spatial hierarchies and linkages, and temporal change. Sandy barrier stress-response and recovery are greatly impacted by fluctuating water levels, stress intensity and frequency, as well as environmental gradients such as differences in sediment storage and supply. Aspects of these stress-response variables are articulated in terms of three main challenges to management: dynamic stability, spatial integrity, and temporal variability. These in turn form the framework for evaluative principles that may be applied to assess how policies and management practices reflect key biophysical processes and human stresses identified by the model.

Yaquina Bay Topobathy DEM

EPA Science Inventory

The U.S.EPA contracted with the U.S.ACE to obtain intertidal and subtidal bathymetric soundings of Yaquina Bay between Poole Slough and the South Beach Marina in 2002. These data were compiled with U.S.ACE subtidal soundings from 1999, 1998, 2000 and National Ocean Service soundi...

Subtidal Benthic Invertebrates Shifting Northward Along the U.S. Atlantic Coast

EPA Science Inventory

Numerous marine and terrestrial species have shifted their ranges poleward in response to warming from global climate change. However, few studies have examined range shifts of subtidal benthic communities in estuarine and nearshore waters. This study examined 20 years (1990–2010...

Spatial Patterns of Subtidal Benthic Invertebrates and Environmental Factors in the Nearshore Gulf of Maine

EPA Science Inventory

The spatial patterns of subtidal benthic invertebrates and physical-chemical variables in the nearshore Gulf of Maine (Acadian Biogeographic Province) were studied to provide information needed to calibrate benthic indices of environmental condition, determine physical-chemical f...

Improving a prediction system for oil spills in the Yellow Sea: effect of tides on subtidal flow.

PubMed

Kim, Chang-Sin; Cho, Yang-Ki; Choi, Byoung-Ju; Jung, Kyung Tae; You, Sung Hyup

2013-03-15

A multi-nested prediction system for the Yellow Sea using drifter trajectory simulations was developed to predict the movements of an oil spill after the MV Hebei Spirit accident. The speeds of the oil spill trajectories predicted by the model without tidal forcing were substantially faster than the observations; however, predictions taking into account the tides, including both tidal cycle and subtidal periods, were satisfactorily improved. Subtidal flow in the simulation without tides was stronger than in that with tides because of reduced frictional effects. Friction induced by tidal stress decelerated the southward subtidal flows driven by northwesterly winter winds along the Korean coast of the Yellow Sea. These results strongly suggest that in order to produce accurate predictions of oil spill trajectories, simulations must include tidal effects, such as variations within a tidal cycle and advections over longer time scales in tide-dominated areas. Copyright © 2012 Elsevier Ltd. All rights reserved.

Deltas, freshwater discharge, and waves along the Young Sound, NE Greenland.

PubMed

Kroon, Aart; Abermann, Jakob; Bendixen, Mette; Lund, Magnus; Sigsgaard, Charlotte; Skov, Kirstine; Hansen, Birger Ulf

2017-02-01

A wide range of delta morphologies occurs along the fringes of the Young Sound in Northeast Greenland due to spatial heterogeneity of delta regimes. In general, the delta regime is related to catchment and basin characteristics (geology, topography, drainage pattern, sediment availability, and bathymetry), fluvial discharges and associated sediment load, and processes by waves and currents. Main factors steering the Arctic fluvial discharges into the Young Sound are the snow and ice melt and precipitation in the catchment, and extreme events like glacier lake outburst floods (GLOFs). Waves are subordinate and only rework fringes of the delta plain forming sandy bars if the exposure and fetch are optimal. Spatial gradients and variability in driving forces (snow and precipitation) and catchment characteristics (amount of glacier coverage, sediment characteristics) as well as the strong and local influence of GLOFs in a specific catchment impede a simple upscaling of sediment fluxes from individual catchments toward a total sediment flux into the Young Sound.

A new macrofaunal limit in the deep biosphere revealed by extreme burrow depths in ancient sediments.

PubMed

Cobain, S L; Hodgson, D M; Peakall, J; Wignall, P B; Cobain, M R D

2018-01-10

Macrofauna is known to inhabit the top few 10s cm of marine sediments, with rare burrows up to two metres below the seabed. Here, we provide evidence from deep-water Permian strata for a previously unrecognised habitat up to at least 8 metres below the sediment-water interface. Infaunal organisms exploited networks of forcibly injected sand below the seabed, forming living traces and reworking sediment. This is the first record that shows sediment injections are responsible for hosting macrofaunal life metres below the contemporaneous seabed. In addition, given the widespread occurrence of thick sandy successions that accumulate in deep-water settings, macrofauna living in the deep biosphere are likely much more prevalent than considered previously. These findings should influence future sampling strategies to better constrain the depth range of infaunal animals living in modern deep-sea sands. One Sentence Summary: The living depth of infaunal macrofauna is shown to reach at least 8 metres in new habitats associated with sand injections.

Sedimentologic characteristics of recent washover deposits from Assateague Island, Maryland

USGS Publications Warehouse

Bernier, Julie C.; Zaremba, Nicholas J.; Wheaton, Cathryn J.; Ellis, Alisha M.; Marot, Marci E.; Smith, Christopher G.

2016-06-08

This report describes sediment data collected using sand augers in active overwash zones on Assateague Island in Maryland. Samples were collected by the U.S. Geological Survey (USGS) during two surveys in March/April and October 2014 (USGS Field Activity Numbers [FAN] 2014-301-FA and 2014-322-FA, respectively). The physical characteristics (for example, sediment texture or bedding structure) of and spatial differences among these deposits will provide information about overwash processes and sediment transport from the sandy barrier-island reaches to the back-barrier environments. Metrics derived from these data, such as mean grain size or deposit thicknesses, can be used to ground-truth remote sensing and geophysical data and can also be incorporated into sediment transport models. Data products, including sample location tables, descriptive core logs, core photographs and x-radiographs, the results of sediment grain-size analyses, and Geographic Information System (GIS) data files with accompanying formal Federal Geographic Data Committee (FGDC) metadata can be downloaded from the Data Downloads page.

Integrated sedimentological and ichnological characteristics of a wave-dominated, macrotidal coast: a case study from the intertidal shoreface of the Dongho coast, southwest Korea

NASA Astrophysics Data System (ADS)

Yang, Byong Cheon; Chang, Tae Soo

2018-04-01

Generalized coastal facies models invariably assume that tidal flats and intertidally exposed shorefaces along macrotidal coasts are tide-dominated. Recent advances in coastal sedimentology, however, have revealed that wave-dominated macrotidal flats also occur in a wide range of coastal settings, in particular where tidal modulation forces the lateral translation of the wave-affected zone across the tidally exposed shoreface with the rising tide. Despite tidal modulation, the depositional character in the latter case (abundant storm deposits) exhibits a high degree of similarity with conventional subtidal shorefaces, implying that it is inherently difficult to distinguish between the two coastal systems in the rock record. In the present study, integrated sedimentological and ichnological data from the Dongho coast, which is located along the southwest coast of Korea, provide valuable information for the establishment of facies criteria that can assist in the recognition of such coastal deposits. In fact, the sedimentary character of the study area, which is dominated by an abundance of wave-formed structures, resembles that generally associated with subtidal shorefaces. In addition, the depositional processes responsible for sediment accumulation are, in the present case, also strongly influenced by pronounced seasonal variations in wave energy. In this context, the study has revealed a number of major features that appear to be characteristic of wave-dominated intertidal flats and shorefaces: (1) firmground muds may be encountered on the beach face, where intense swash-backwash motions are dominant; (2) the thickness of storm deposits decreases landward, reflecting the progressive decrease in wave energy; (3) ichnologically, there is an offshore shift in the dominance of trace fossils from the Skolithos ichnofacies, including Ophiomorpha, Thalassinoides and Psilonichnus, to a proximal expression of the Cruziana ichnofacies, which includes Siphonichnus and Asterosoma; (4) compared with subtidal shorefaces, the overall ichnological suite is represented by a substantial reduction in diversity and less uniformly distributed burrows. Although these findings have not yet been applied to the rock record, they should nevertheless assist in the distinction between corresponding coastal deposits.

Seasonal variations in the characteristics of superficial sediments in a macrotidal estuary (the Seine inlet, France)

NASA Astrophysics Data System (ADS)

Lesourd, S.; Lesueur, P.; Brun-Cottan, J. C.; Garnaud, S.; Poupinet, N.

2003-09-01

Seasonal variations in the sedimentary regime in the mouth of the Seine river, a macrotidal estuary, are described for a 3-year period. The aim of this study is to characterize and to understand the main governing mechanisms, using data from more than a thousand of superficial sediment grab samples or box cores gathered throughout the study period. Analyses of lithofacies and rheological properties were carried out. The distribution of sediments is governed by seasonal meteorological variations. The surface covered by mud reaches a maximum (40% of the total mouth area) during winter. After the winter, the soft mud deposits are progressively redistributed throughout the whole estuary area and onto the shelf. During the lowest freshwater flow at the end of summer, the fine-grained sediments cover less than 20% of the river mouth area. These seasonal variations mainly depend on the river discharge intensity, but are also linked to wave activity. In the study area, the amount of fine-grained deposits after high river flow periods depends on (1) volume of mud erodable within the estuary, (2) the duration of the flood tidal influx, and (3) the duration preceding the particular annual high river flow. During the last decades, filling of the estuary upstream from Honfleur has led to a downstream shift of the fine-grained sediment deposition area; following this, the present-day mud deposition area is in the open part of the estuary, in the subtidal shallow area. Subsequently, fresh mud deposits undergo intense hydrodynamical and meteorological effects, and are partly reworked by waves and tidal currents effects. In this study, it is shown that the behaviour of suspended matter and of superficial sediments is strongly influenced by short but intense events including high river flows and gales.

Seasonal changes in infaunal community structure in a hypertrophic brackish canal: Effects of hypoxia, sulfide, and predator-prey interaction.

PubMed

Kanaya, Gen; Nakamura, Yasuo; Koizumi, Tomoyoshi; Yamada, Katsumasa

2015-07-01

We conducted a one-year survey of macrozoobenthic community structure at 5 stations in a eutrophic canal in inner Tokyo Bay, focusing on the impacts of hypoxia, sediment H2S, and species interaction in the littoral soft-bottom habitats. Complete defaunation or decreasing density of less-tolerant taxa occurred under hypoxia during warmer months, especially at subtidal or sulfidic stations; this was followed by rapid recolonization by opportunistic polychaetes in fall-winter. Sedimentary H2S increased the mortality of macroinvertebrates under hypoxia or delayed population recovery during recolonization. The density of several polychaetes (e.g., Pseudopolydora reticulata) declined in winter, coincident with immigration of the predator Armandia lanceolata. This suggests that absence of A. lanceolata under moderate hypoxia enabled the proliferation of prey taxa. We conclude that oxygen concentration, sediment H2S, and hypoxia-induced changes in species interactions are potential drivers for spatiotemporal changes in macrozoobenthic assemblage structure in hypoxia-prone soft-bottom communities. Copyright © 2015 Elsevier Ltd. All rights reserved.

The environmental distribution of late proterozoic organisms

NASA Technical Reports Server (NTRS)

Knoll, A. H.

1991-01-01

Along present day coast lines, the environmental distributions of prokaryotic and protistan populations are often sharply delimited. Realized habitat ranges are generally narrower than those circumscribed by physiological tolerances, suggesting the importance of organism-organism interactions in the determination of population distributions. Microfossil populations preserved in silicified carbonates, dolomites, and shales of the 700-800 Ma old Akademikerbreen Group, Svalbard, and elsewhere indicate that the environmental distributions were defined equally clearly during the Proterozoic Eon. The Draken Conglomerate Formation is a tidal flat/lagoonal complex in which we have distinguished five principle biofacies containing a total of 42 taxa. Supratidal to subtidal gradients include the increasing abundance and diversity of both mat dweller microbenthos and allochthonous (principally planktonic) organisms, as well as a taphonomically important pattern of decreasing sheath thickness among mat builder microorganisms. The seaward barriers of Akademikerbreen lagoons were oolitic shoals, and these contain about a dozen endolithic and epilithic species not observed elsewhere in the group. Subtidal environments below fair weather wave base are represented by mudstones of the Svanbergfjellet Formation. These contain abundant and diverse cyanobacteria-like fossils generally similar to but specifically different from those found in tidal flat sediments, as well as diverse unicellular protists (some of impressive morphological complexity) and at least half a dozen cellularly preserved metaphyte populations. In all, more than 80 species are distributed among Akademikerbreen lithologies. Fossil assemblages from Svalbard and elsewhere illustrate the potential for a much finer paleoecological, biostratigraphic, and, hence, evolutionary resolution of the early fossil record.

A seasonal and spatial comparison of metals, and stable carbon and nitrogen isotopes, in Chincoteague Bay and the marsh deposits of Assateague Island and the adjacent vicinity, Maryland and Virginia

USGS Publications Warehouse

Ellis, Alisha M.; Smith, Christopher G.

2017-11-28

After Hurricane Sandy, scientists from the U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center conducted a seasonal collection of estuarine, marsh, and sandy overwash surface sediments from Chincoteague Bay, Tom’s Cove, and the surrounding Assateague Island and Delmarva Peninsula in March–April and October 2014. Surplus surface sediment was analyzed for metals, percent carbon and nitrogen, δ13C, and δ15N as part of a complementary U.S. Geological Survey Coastal and Marine Geology Program Sea-level and Storm Impacts on Estuarine Environments and Shorelines project study. The geochemical subsample analyzed for metals and stable isotopes at each site may be used for comparison with past data sets, to create a modern baseline of the natural distribution of the area, to understand seasonal variability as it relates to the health of the local environment, and to assess marsh-to-bay interactions. The use of metals, stable carbon, and stable nitrogen isotopes allows for a more cohesive snapshot of factors influencing the environment and could aid in tracking environmental change.This report serves as an archive for chemical data derived from the surface sediment. Data are available for a seasonal comparison between the March–April 2014 and October 2014 sampling trips. Downloadable data are available as Microsoft Excel spreadsheets. These additional files include formal Federal Geographic Data Committee metadata (data downloads).

Permeability of sediment cores from methane hydrate deposit in the Eastern Nankai Trough, Japan

NASA Astrophysics Data System (ADS)

Konno, Y.; Yoneda, J.; Egawa, K.; Ito, T.; Jin, Y.; Kida, M.; Suzuki, K.; Nakatsuka, Y.; Nagao, J.

2013-12-01

Effective and absolute permeability are key parameters for gas production from methane-hydrate-bearing sandy sediments. Effective and/or absolute permeability have been measured using methane-hydrate-bearing sandy cores and clayey and silty cores recovered from Daini Atsumi Knoll in the Eastern Nankai Trough during the 2012 JOGMEC/JAPEX Pressure coring operation. Liquid-nitrogen-immersed cores were prepared by rapid depressurization of pressure cores recovered by a pressure coring system referred to as the Hybrid PCS. Cores were shaped cylindrically on a lathe with spraying of liquid nitrogen to prevent hydrate dissociation. Permeability was measured by a flooding test or a pressure relaxation method under near in-situ pressure and temperature conditions. Measured effective permeability of hydrate-bearing sediments is less than tens of md, which are order of magnitude less than absolute permeability. Absolute permeability of clayey cores is approximately tens of μd, which would perform a sealing function as cap rocks. Permeability reduction due to a swelling effect was observed for a silty core during flooding test of pure water mimicking hydrate-dissociation-water. Swelling effect may cause production formation damage especially at a later stage of gas production from methane hydrate deposits. This study was financially supported by the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) that carries out Japan's Methane Hydrate R&D Program conducted by the Ministry of Economy, Trade and Industry (METI).

Geologic Map of The Volcanoes Quadrangle, Bernalillo and Sandoval Counties, New Mexico

USGS Publications Warehouse

Thompson, Ren A.; Shroba, Ralph R.; Menges, Christopher M.; Schmidt, Dwight L.; Personius, Stephen F.; Brandt, Theodore R.

2009-01-01

This geologic map, in support of the U.S. Geological Survey Middle Rio Grande Basin Geologic Mapping Project, shows the spatial distribution of surficial deposits, lava flows, and related sediments of the Albuquerque volcanoes, upper Santa Fe Group sediments, faults, and fault-related structural features. These deposits are on, along, and beneath the Llano de Albuquerque (West Mesa) west of Albuquerque, New Mexico. Some of these deposits are in the western part of Petroglyph National Monument. Artificial fill deposits are mapped chiefly beneath and near the City of Albuquerque Soil Amendment Facility and the Double Eagle II Airport. Alluvial deposits were mapped in and along stream channels, beneath terrace surfaces, and on the Llano de Albuquerque and its adjacent hill slopes. Deposits composed of alluvium and colluvium are also mapped on hill slopes. Wedge-shaped deposits composed chiefly of sandy sheetwash deposits, eolian sand, and intercalated calcic soils have formed on the downthrown-sides of faults. Deposits of active and inactive eolian sand and sandy sheetwash deposits mantle the Llano de Albuquerque. Lava flows and related sediments of the Albuquerque volcanoes were mapped near the southeast corner of the map area. They include eleven young lava flow units and, where discernable, associated vent and near-vent pyroclastic deposits associated with cinder cones. Upper Santa Fe Group sediments are chiefly fluvial in origin, and are well exposed near the western boundary of the map area. From youngest to oldest they include a gravel unit, pebbly sand unit, tan sand and mud unit, tan sand unit, tan sand and clay unit, and silty sand unit. Undivided upper Santa Fe Group sediments are mapped in the eastern part of the map area. Faults were identified on the basis of surface expression determined from field mapping and interpretation of aeromagnetic data where concealed beneath surficial deposits. Fault-related structural features are exposed and were mapped near the western boundary of the map area.

Stratigraphy and depositional environment of early Mississippian Joana limestone of east-central Nevada

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

Gilmore, T.

1987-08-01

The Early Mississippian Joana Limestone in the southern Schell Creek and Egan Ranges of east-central Nevada is divided into nine rock types: mudstone, fossiliferous mudstone, wackestone, peloidal wackestone, pelmatozoan wackestone, pelmatozoan packstone, pelmatozoan grainstone, and ooid packstone. From the combined rock type and larger scale outcrop information, three depositional facies were identified: (1) unbedded subtidal, (2) bedded subtidal, and (3) restricted subtidal, each containing a unique set of diagnostic microfacies. Facies thicknesses, lithologies, and contacts with adjacent stratigraphic units indicate a highly varied paleotopography of localized highs and basins during Joana deposition. It is suggested that Waulsortian-type buildups occur downslopemore » of some paleohighs in the unbedded subtidal facies. An age of upper Kinderhookian to lowest Osagean within the Mississippian Period was determined for the Joana, based primarily on conodonts and foraminifera. In the middle beds of the Joana, the previously unreported upper Siphonodella crenulata conodont zone occurs and relates the timing of the Joana to regional geologic events. Color alteration indices of these conodonts are 1.5 to 2, and occur in the oil generation window. Additionally, oil staining was noted in numerous samples primarily from the lower half of the formation, represented by the unbedded subtidal facies. Porosities of the formation are varied, ranging from no visible porosity to over 20% interparticle porosity in some pelmatozoan grainstones.« less

Flexibility of Physiological Traits Underlying Inter-Individual Growth Differences in Intertidal and Subtidal Mussels Mytilusgalloprovincialis

PubMed Central

Fernández-Reiriz, María José; Irisarri, Jade; Labarta, Uxio

2016-01-01

Mussel seed (Mytilusgalloprovincialis) gathered from the intertidal and subtidal environments of a Galician embayment (NW, Spain) were maintained in the laboratory during five months to select fast (F) and slow (S) growing mussels. The physiological basis underlying inter-individual growth variations were compared for F and S mussels from both origins. Fast growing seemed to be a consequence of greater energy intake (20% higher clearance and ingestion rate) and higher food absorption rate coupled with low metabolic costs. The enhanced energy absorption (around 65% higher) resulted in 3 times higher Scope for Growth in F mussels (20.5±4.9 J h−1) than S individuals (7.3±1.1 J h−1). The higher clearance rate of F mussels appears to be linked with larger gill filtration surface compared to S mussels. Intertidal mussels showed higher food acquisition and absorption per mg of organic weight (i.e. mass-specific standardization) than subtidal mussels under the optimal feeding conditions of the laboratory. However, the enhanced feeding and digestive rates were not enough to compensate for the initial differences in tissue weight between mussels of similar shell length collected from the intertidal and subtidal environments. At the end of the experiment, subtidal individuals had higher gill efficiency, which probably lead to higher total feeding and absorption rates relative to intertidal individuals. PMID:26849372

Assessment of Available Phosphorus in the Lake Sediments Using an Innovative Composite Membrane

NASA Astrophysics Data System (ADS)

Huang, Qinghui; Wang, Zijian; Wang, Donghong

2010-11-01

An innovative iron oxide embedded cellulose acetate membrane (FeO/CAM) was synthesized and used to study available phosphorus in Chinese lake sediments. The kinetics of available P release was investigated by FeO/CAM for different types of sediments ranging in Olsen-P from 19.1 to 170.6 mg/kg. The results showed that the average kd values (0.094 h-1) of the Taihu sediments were comparable to those of the soils with similar texture estimated by iron oxide impregnated filter paper (FeO paper) though they were generally lower than those of sandy soils. It is indicated that the FeO/CAM can be used as an infinite P sink to estimate available P (FeO-P). The concentrations of FeO-P were significantly correlated with those of extractable P forms, e.g. Olsen-P (R2 = 0.962, p<0.01) in lake sediments. This synthetic membrane excelled FeO paper in the endurance and the stain resistance to soil particles. Therefore, the FeO/CAM is useful to assess phosphorus bioavailability of the sediments.

Effects of conventional and biodegradable microplastics on a marine ecosystem engineer (Arenicola marina) and sediment nutrient cycling.

PubMed

Green, Dannielle Senga; Boots, Bas; Sigwart, Julia; Jiang, Shan; Rocha, Carlos

2016-01-01

Effects of microplastic pollution on benthic organisms and ecosystem services provided by sedimentary habitats are largely unknown. An outdoor mesocosm experiment was done to realistically assess the effects of three different types of microplastic pollution (one biodegradable type; polylactic acid and two conventional types; polyethylene and polyvinylchloride) at increasing concentrations (0.02, 0.2 and 2% of wet sediment weight) on the health and biological activity of lugworms, Arenicola marina (Linnaeus, 1758), and on nitrogen cycling and primary productivity of the sediment they inhabit. After 31 days, A. marina produced less casts in sediments containing microplastics. Metabolic rates of A. marina increased, while microalgal biomass decreased at high concentrations, compared to sediments with low concentrations or without microplastics. Responses were strongest to polyvinylchloride, emphasising that different materials may have differential effects. Each material needs to be carefully evaluated in order to assess their risks as microplastic pollution. Overall, both conventional and biodegradable microplastics in sandy sediments can affect the health and behaviour of lugworms and directly or indirectly reduce primary productivity of these habitats. Copyright © 2015 Elsevier Ltd. All rights reserved.

Spatial and temporal correlation between beach and wave processes: implications for bar-berm sediment transition

NASA Astrophysics Data System (ADS)

Joevivek, V.; Chandrasekar, N.; Saravanan, S.; Anandakumar, H.; Thanushkodi, K.; Suguna, N.; Jaya, J.

2018-06-01

Investigation of a beach and its wave conditions is highly requisite for understanding the physical processes in a coast. This study composes spatial and temporal correlation between beach and nearshore processes along the extensive sandy beach of Nagapattinam coast, southeast peninsular India. The data collection includes beach profile, wave data, and intertidal sediment samples for 2 years from January 2011 to January 2013. The field data revealed significant variability in beach and wave morphology during the northeast (NE) and southwest (SW) monsoon. However, the beach has been stabilized by the reworking of sediment distribution during the calm period. The changes in grain sorting and longshore sediment transport serve as a clear evidence of the sediment migration that persevered between foreshore and nearshore regions. The Empirical Orthogonal Function (EOF) analysis and Canonical Correlation Analysis (CCA) were utilized to investigate the spatial and temporal linkages between beach and nearshore criterions. The outcome of the multivariate analysis unveiled that the seasonal variations in the wave climate tends to influence the bar-berm sediment transition that is discerned in the coast.

Microbial acetogenesis as a source of organic acids in ancient Atlantic Coastal Plain sediments

USGS Publications Warehouse

Chapelle, F.H.; Bradley, P.M.

1996-01-01

Field and laboratory evidence shows that deeply buried (90-888 m) fine-grained sediments of the Atlantic Coastal Plain contain viable acetogenic microorganisms, and that these microorganisms actively produce organic acids. Concentrations of formate, acetate, and propionate in pore waters extracted from fine-grained sediments ranged from 50 ??M to 5 mM and were much higher than in adjacent pore waters associated with sandy sediments (<2 ??M). Laboratory studies showed that asceptically cored fine-grained sediments incubated under a H2 atmosphere produced formate and acetate, and that H14CO-3 was converted to 14C-acetate and 14C-formate over time. An enrichment culture of these acetogenic microorganisms was recovered from one long-term incubation that showed the presence of several morphologically distinct gram-positive, rod-shaped bacteria. These microorganisms were capable of growth under autotrophic (H2 + CO2), heterotrophic (syringate), and mixotrophic (H2 + CO2 + syringate) conditions. These results suggest that microbial acetogenesis, rather than abiotic processes, is the most important organic acid-producing mechanism during low-temperature (???30 ??C) diagenesis of Atlantic Coastal Plain sediments.

Geoacoustic provinces and physical properties of surface sediments in the southern part of the East Sea, Korea

NASA Astrophysics Data System (ADS)

Kim, Sora; Bahk, Jang-Jun; Kim, Daechoul; Lee, Gwang Soo; Kim, Seong-Pil

2017-04-01

A total of 288 piston and box core samples were collected and analyzed to characterize the physical properties and geoacoustic provinces of surficial sediments in the southern part of the East Sea. Based on in-situ condition sound velocity (converted laboratory sound velocity to in-situ condition sound velocity) and sediment properties (sediment textures and physical properties), the study area was divided into eight provinces (Province IA, IB, IC, II, III, IV, VA, and VB) : (1) Province IA : hemi-pelagic mud partially mixed with intermittent sandy sediments originating from the outer shelf due to slide/slump or mass flows (in-situ condition sound velocity: 1439 m/s, mean grain size: 8.5Φ, bulk density: 1.24 g/cm3,and porosity: 84%); (2) Province IB : Holocene muddy sediments are dominant, but in some area that is influenced by the surrounding land and coast (in-situ condition sound velocity: 1448 m/s, mean grain size: 8.3Φ, bulk density: 1.32 g/cm3, and porosity: 79%); (3) Province IC : muddy sediments that were deposited during the Holocene (in-situ condition sound velocity: 1457 m/s, mean grain size: 7.8Φ, bulk density: 1.36 g/cm3, and porosity: 78%); (4) Province II : mixed recent and relict sediments (in-situ condition sound velocity: 1493 m/s, mean grain size: 5.9Φ, bulk density: 1.53 g/cm3, and porosity: 68%); (5) Province III (Pohang) : there is a mixture of muddy sediments and sandy sediments and sediments from Hyeongsan River are mostly deposited (in-situ condition sound velocity: 1586 m/s, mean grain size: 4.1Φ, bulk density: 1.74 g/cm3, and porosity: 57%); (6) Province IV : coarse-grained relict sediments formed during the Pleistocene (in-situ condition sound velocity: 1572 m/s, mean grain size: 4.1Φ, bulk density: 1.76 g/cm3, and porosity: 55%); (7) Province VA : relict sand with some gravel, show marked differences from the area in which muddy sediments are deposited (in-situ condition sound velocity: 1662 m/s, mean grain size: 3.3Φ, bulk density: 1.82 g/cm3, and porosity: 51%), and (8) Province VB : similar to but coarser sediments than Province IV (in-situ condition sound velocity: 1667 m/s, mean grain size: 3.2Φ, bulk density: 1.87 g/cm3, and porosity: 46%). The in-situ condition sound velocity, mean grain size, and bulk density increased from Province IA to Province VB, whereas the porosity and water content decrease. Variability of the physical and acoustic properties tended to follow the general of the mean grain size. The classification of each province using the in-situ condition sound velocity corrected with the temperature and sediment type provides a better reflection of the sediment properties and sedimentary environment.

Biodiversity and density of subtidal benthos of an oceanic tropical island (a comparison within the Pacific Ocean)

NASA Astrophysics Data System (ADS)

Sibaja-Cordero, Jeffrey A.; Troncoso, Jesús S.; Cortés, Jorge; Moreira, Juan; Vargas, José A.; Benavides-Varela, Catalina

2016-09-01

The marine macrofauna of the shallow sandy bottom of Isla del Coco, Costa Rica (5°32‧N-87°04‧W) was assessed in April 2010. Comparisons of richness, density and diversity between levels of exposure to ocean influence were carried out. During this study 15,407 specimens with a mean density of 1826 ind m- 2 were found between 3-75 m depth. The specimens were distributed in 267 taxa (29% new additions) with a mean of 55 ± 14 expected taxa m- 2. The values of density, richness and diversity were higher at the exposed coast, whereas they decreased at inner bays due to the influence of freshwater input. These estimates were compared with 40 studies in the Tropical Pacific Ocean (TPO). Taxa and density previously reported from the TPO were dependent on the area and depth range studied. Additionally, these parameters varied according to the sampling gear used. For example, higher densities were reported by using corers or boxcorers. The Shannon-Wiener index was most effective in identifying sediment and geographical patterns of variation along the TPO. Differences in these diversity parameters were also found between islands and mainland studies. Moreover, richness and density values from Isla del Coco were higher than the same parameters reported in studies using grabs in the TPO. At Isla del Coco annelids were dominant in terms of relative abundance (49.6%), followed by crustaceans (10.1%), mollusks (2.8%), and others faunal groups (37.5%). The faunistic composition at Isla del Coco differed when compared to the rest of localities of TPO due to the higher contribution of miscellaneous groups. In conclusion, the comparison with previous studies in the TPO indicate that islands like Isla del Coco have high numbers of taxa and diversity than those of the mainland, but lower density. However, this value is influenced by the sampling methodology. The taxa accumulation curve at Isla del Coco did not reach the asymptote, suggesting that an intensive sampling, especially at deep waters, would increase the number of taxa.

Habitat loss and gain: Influence on habitat attractiveness for estuarine fish communities

NASA Astrophysics Data System (ADS)

Amorim, Eva; Ramos, Sandra; Elliott, Michael; Franco, Anita; Bordalo, Adriano A.

2017-10-01

Habitat structure and complexity influence the structuring and functioning of fish communities. Habitat changes are one of the main pressures affecting estuarine systems worldwide, yet the degree and rate of change and its impact on fish communities is still poorly understood. In order to quantify historical modifications in habitat structure, an ecohydrological classification system using physiotopes, i.e. units with homogenous abiotic characteristics, was developed for the lower Lima estuary (NW Portugal). Field data, aerial imagery, historical maps and interpolation methods were used to map input variables, including bathymetry, substratum (hard/soft), sediment composition, hydrodynamics (current velocity) and vegetation coverage. Physiotopes were then mapped for the years of 1933 and 2013 and the areas lost and gained over the 80 years were quantified. The implications of changes for the benthic and demersal fish communities using the lower estuary were estimated using the attractiveness to those communities of each physiotope, while considering the main estuarine habitat functions for fish, namely spawning, nursery, feeding and refuge areas and migratory routes. The lower estuary was highly affected due to urbanisation and development and, following a port/harbour expansion, its boundary moved seaward causing an increase in total area. Modifications led to the loss of most of its sandy and saltmarsh intertidal physiotopes, which were replaced by deeper subtidal physiotopes. The most attractive physiotopes for fish (defined as the way in which they supported the fish ecological features) decreased in area while less attractive ones increased, producing an overall lower attractiveness of the studied area in 2013 compared to 1933. The implications of habitat alterations for the fish using the estuary include potential changes in the nursery carrying capacity and the functioning of the fish community. The study also highlighted the poor knowledge of the impacts of habitat changes on fish due to coastal development and urbanisation and emphasises that ecosystem management and conservation will benefit from a wider understanding of habitat functional roles and habitat changes influencing the functioning and structure of the fish communities.

DYNAMICS OF A SUBTIDAL SEAGRASS LANDSCAPE: SEASONAL AND ANNUAL CHANGE IN RELATION TO WATER DEPTH

EPA Science Inventory

The spatial heterogeneity of a subtidal marine landscape and the areal extent of both monospecific and mixed patches of seagrass species were studied in Tampa Bay, FL. Specifically, we examined the temporal dynamics of seagrass distribution and its relationship to water depth an...

High-resolution geophysical data from the Inner Continental Shelf: South of Martha's Vineyard and north of Nantucket, Massachusetts

USGS Publications Warehouse

Ackerman, Seth D.; Brothers, Laura L.; Foster, David S.; Andrews, Brian D.; Baldwin, Wayne E.; Schwab, William C.

2016-10-28

The U.S. Geological Survey and the Massachusetts Office of Coastal Zone Management have cooperated to map approximately 185 square kilometers of the inner continental shelf south of Martha’s Vineyard and north of Nantucket, Massachusetts. This report contains geophysical data collected by the U.S. Geological Survey during a survey in 2013. The geophysical data include (1) swath bathymetry collected by using interferometric sonar, (2) acoustic backscatter from the interferometric sonar, and (3) seismic-reflection profiles from a chirp subbottom profiler. These spatial data support research on the Quaternary evolution of coastal Massachusetts, the influence of sea-level change and sediment supply on coastal evolution, and efforts to understand the type, distribution, and quality of subtidal marine habitats in the coastal ocean of Massachusetts.

Transport of bisphenol-A in sandy aquifer sediment: Column experiment.

PubMed

Zakari, Sissou; Liu, Hui; Tong, Lei; Wang, Yan; Liu, Jianfeng

2016-02-01

The present paper aims to study the transport behavior of bisphenol-A (BPA) in sandy aquifer so as to provide important parameters for the prediction and control of contaminant plume in aquifer. Miscible displacement experiments were conducted and the breakthrough curves (BTCs) were simulated using HYDRUS-1D software. The effects of pore-water velocity (10-52 cm h(-1)) and initial concentration (2.5-40 mg L(-1)) on the sorption were also investigated. The BTCs of BPA fit the linear first-order non-equilibrium two-site model. The parameters such as partition coefficient (K(d)), the fraction of instantaneous adsorption on "Type-1" sites (F), the first order sorption rate coefficient for the kinetic non-equilibrium (type-2) sites (α), the retardation coefficient (R), and sorption capacity (q(column)) were computed. Results showed that BPA transported 0.11-0.83 m with various pore water velocity in sandy sediment column when water flowed 1 m. The sorption of BPA was mainly caused by the instantaneous surface adsorption as F varied from 0.596 to 0.908. The transport velocity of BPA was affected by pore water velocity (v) and followed the linear equation 1/R = 0.0600 + 0.0110v (r(2) = 0.9724). The parameter K(d) were also closely related to v and followed the equation LnK(d) = 1.0023-0.0482v (r(2) = 0.9690). The sorption capacity was more related to the initial BPA concentration (C0) and followed the linear equation q(column) = 0.265 + 0.253C0 (r(2) = 0.9727). The parameter α was affected by both v and C0 whereas F was not dramatically affected by both. Copyright © 2015 Elsevier Ltd. All rights reserved.

Turbidite megabeds in an Oceanic Rift Valley recording jokulhlaups of late Pleistocene glacial lakes of the western United States

USGS Publications Warehouse

Zuffa, G.G.; Normark, W.R.; Serra, F.; Brunner, C.A.

2000-01-01

Escanaba Trough is the southernmost segment of the Gorda Ridge and is filled by sandy turbidites locally exceeding 500 m in thickness. New results from Ocean Drilling Program (ODP) Sites 1037 and 1038 that include accelerator mass spectrometry (AMS) 14C dates and revised petrographic evaluation of the sediment provenance, combined with high-resolution seismic-reflection profiles, provide a lithostratigraphic framework for the turbidite deposits. Three fining-upward units of sandy turbidites from the upper 365 m at ODP Site 1037 can be correlated with sediment recovered at ODP Site 1038 and Deep Sea Drilling Program (DSDP) Site 35. Six AMS 14C ages in the upper 317 m of the sequence at Site 1037 indicate that average deposition rates exceeded 10 m/k.yr. between 32 and 11 ka, with nearly instantaneous deposition of one ~60-m interval of sand. Petrography of the sand beds is consistent with a Columbia River source for the entire sedimentary sequence in Escanaba Trough. High-resolution acoustic stratigraphy shows that the turbidites in the upper 60 m at Site 1037 provide a characteristic sequence of key reflectors that occurs across the floor of the entire Escanaba Trough. Recent mapping of turbidite systems in the northeast Pacific Ocean suggests that the turbidity currents reached the Escanaba Trough along an 1100-km-long pathway from the Columbia River to the west flank of the Gorda Ridge. The age of the upper fining-upward unit of sandy turbidites appears to correspond to the latest Wisconsinan outburst of glacial Lake Missoula. Many of the outbursts, or jokulhlaups, from the glacial lakes probably continued flowing as hyperpycnally generated turbidity currents on entering the sea at the mouth of the Columbia River.

A ravenous river reclaims its true course: the tale of Marmot Dam''s demise

Treesearch

Noreen Parks; Gordon Grant

2009-01-01

Removing dams that are outdated, unsafe, or pose significant economic or environmental costs has emerged in the last 10 years as a major river restoration strategy. The removal of the 45-foot-high Marmot Dam on the Sandy River in 2007 resulted in the biggest sediment release accompanying any dam removal to date. It also provided an unprecedented opportunity...

Community microrespirometry and molecular analyses reveal a diverse energy economy in Great Boiling Spring and Sandy's Spring West in the U.S. Great Basin.

PubMed

Murphy, Caitlin N; Dodsworth, Jeremy A; Babbitt, Aaron B; Hedlund, Brian P

2013-05-01

Microrespirometry showed that several organic and inorganic electron donors stimulated oxygen consumption in two ∼80°C springs. Sediment and planktonic communities were structurally and functionally distinct, and quantitative PCR revealed catabolically distinct subpopulations of Thermocrinis. This study suggests that a variety of chemolithotrophic metabolisms operate simultaneously in these springs.

Surf Zone Sediment Size Variation, Morphodynamics, and Hydrodynamics During Sea/Land Breeze and El-Norte Storm in Sisal, Yucatan, Mexico

NASA Astrophysics Data System (ADS)

Alrushaid, T.; Figlus, J.; Torres-Freyermuth, A.; Puleo, J. A.; Dellapenna, T. M.

2016-02-01

Coastlines around the world are under ever-increasing pressure due to population trends, commerce, and geophysical processes like tropical storms and erosion. This multi-institutional field campaign was conducted to improve our understanding of complex nearshore processes under varying forcing conditions on a microtidal, sandy beach located in Sisal, Yucatan from 3/27 to 4/12/2014. Hydrodynamics, morphodynamics, and textural variability were investigated during: (1) a cold front event (referred to as El-Norte); (2) land breeze (LB); and (3) sea breeze (SB). The instrumentation layout included three surf/swash zone cross-shore transects where water elevation, suspended sediment concentration, bed load, and current velocities were measured, as well as several offshore ADCP for hydrodynamic measurements. TKE, τb, ɛ and were estimated using the data obtained from surf zone ADV. In addition, Hs and Tsin the surf zone were computed using measurements from ADV pressure sensors, while a separate pressure transducer was used to obtain water free-surface elevation within the swash zone. During SB cycles the study area experienced wind velocities reaching up to 12ms-1, and 15ms-1 during El-Norte. Elevated wind stress during El-Norte resulted in Hs of 1.5m and 0.6m in water depths of 10m and 0.4m, respectively. Surface sediment grab samples during SB/LB cycles showed that the swash zone had a moderately well sorted distribution with a mean grain size of 0.5mm, while poor sorting and a mean grain size of 0.7mm were found during El-Norte. Additionally, measured bathymetry data showed evidence for offshore sandbar migration during strong offshore currents (0.4ms-1) during El-Norte, while onshore sandbar migration was evident during SB/LB periods (0.3ms-1 and 0.1ms-1, respectively). This study highlights how different weather forcing conditions affect hydrodynamics, morphodynamics, and textural variability on a sandy beach. Aside from furthering our knowledge on these complex processes, the findings may lead to improved coastal management strategies for sandy coastlines.

Continuum Statistics of the Bed Topography in a Sandy River

NASA Astrophysics Data System (ADS)

McElroy, B.; Jerolmack, D.; Mohrig, D.

2005-12-01

Temporal and spatial variabilities in the bed geometry of sandy rivers contain information about processes of sediment transport that has not been fully appreciated. This is primarily due to a disparity between the dynamic nature of the sediment-fluid interface and the relatively static methods of surveying bed elevation, e.g. single profiles or point measurements. High resolution topographic data is paramount to understanding the dynamic behavior of sandy beds. We present and analyze a data set collected on a 2cm x 2cm grid at 1 minute intervals and with a vertical precision of ~1mm. This was accomplished by using Lambert-Beer's Law for attenuation of light to transform low-altitude aerial photographs into digital elevation models. Forty successive models were generated for a 20 m by 30 m section of channel bottom of the N. Loup River, Nebraska. To calculate the average, whole bed translation rate, or celerity, cross-correlations between a reference bed topography and its proceeding configurations were determined. Time differences between models were related to the shift lengths that produced correlation maxima for each model pair. The result is a celerity of ~3.8cm/s with a correlation coefficient of 0.992. Bed topography also deforms while it translates, and this can be seen as a secular decrease of correlation maxima. The form of this decrease in correlation is exponential, and from it an interface half-life is defined. In this case, the bed had become extensively reorganized within ~40 minutes, the time necessary to translate the bed one wavelength of the dominant roughness element. Although the bed is continuously deforming, its roughness is statistically stationary. Essentially, a mean roughness is maintained as the bed creates new realizations of itself. The dynamic nature of the whole bed and similarly transient behavior of individual elements suggests the utility of a holistic approach to studying the feedback between bed topography, fluid flow, and sediment transport. Furthermore, it raises questions about the usefulness of detailed analysis of flow and transport over individual forms.

Inner-shelf ocean dynamics and seafloor morphologic changes during Hurricane Sandy

USGS Publications Warehouse

Warner, John C.; Schwab, William C.; List, Jeffrey; Safak, Ilgar; Liste, Maria; Baldwin, Wayne E.

2017-01-01

Hurricane Sandy was one of the most destructive hurricanes in US history, making landfall on the New Jersey coast on Oct 30, 2012. Storm impacts included several barrier island breaches, massive coastal erosion, and flooding. While changes to the subaerial landscape are relatively easily observed, storm-induced changes to the adjacent shoreface and inner continental shelf are more difficult to evaluate. These regions provide a framework for the coastal zone, are important for navigation, aggregate resources, marine ecosystems, and coastal evolution. Here we provide unprecedented perspective regarding regional inner continental shelf sediment dynamics based on both observations and numerical modeling over time scales associated with these types of large storm events. Oceanographic conditions and seafloor morphologic changes are evaluated using both a coupled atmospheric-ocean-wave-sediment numerical modeling system and observation analysis from a series of geologic surveys and oceanographic instrument deployments focused on a region offshore of Fire Island, NY. The geologic investigations conducted in 2011 and 2014 revealed lateral movement of sedimentary structures of distances up to 450 m and in water depths up to 30 m, and vertical changes in sediment thickness greater than 1 m in some locations. The modeling investigations utilize a system with grid refinement designed to simulate oceanographic conditions with progressively increasing resolutions for the entire US East Coast (5-km grid), the New York Bight (700-m grid), and offshore of Fire Island, NY (100-m grid), allowing larger scale dynamics to drive smaller scale coastal changes. Model results in the New York Bight identify maximum storm surge of up to 3 m, surface currents on the order of 2 ms-1 along the New Jersey coast, waves up to 8 m in height, and bottom stresses exceeding 10 Pa. Flow down the Hudson Shelf Valley is shown to result in convergent sediment transport and deposition along its axis. Modeled sediment redistribution along Fire Island showed erosion across the crests of inner shelf sand ridges and sedimentation in adjacent troughs, consistent with the geologic observations.

Total assemblages of benthic foraminifera from a mixed siliciclastic/carbonate inner shelf; preliminary results from the bays of Soline and Nin (Adriatic Sea, Croatia)

NASA Astrophysics Data System (ADS)

Vidović, J.; Ćosović, V.; Juračić, M.; Benac, Č.

2012-04-01

Eastern Adriatic shelf is mixed siliciclastic/carbonate area with a great proportion of carbonate biogenous production. This study presents analysis and comparison of total benthic foraminiferal assemblages (their composition, diversity and distribution) in surface sediments from two Eastern Adriatic shallow water bays (Soline and Nin Bay), sampled seasonally from 2006 to 2008. In order to characterize the carbonate sediment production, 62 samples along the bathymetric profiles (from 2 to 20 m) were collected by scuba diving with short PVC corers. Granulometrical analysis was done using method of wet sieving. Statistical analyses (cluster analysis, PCA) were performed using Past program. The most abundant biogenous components in different sediments from Soline Bay (muddy sandy gravel and mud) are foraminifera, followed by fragments of mollusks, gastropods, bryozoans and sea urchins. Foraminiferal assemblages are high diversified as confirmed by Shannon-Wiener index varying from 2.14 to 3.39, Fisher α index from 5.74 to 16.30 and Equitability from 0.32 to 0.72. The shallowest part of the bay is covered with the sand, consisted of high proportion of siliciclastic component and impoverished in biogenous remnants. Foraminiferal assemblages have low diversity (Shannon-Wiener index 1.36, Fisher α index 2.31 and Equitability 0.32). Throughout Nin Bay, sediments (classified as sand, muddy sand and mud) are consisted of various biogenic remnants. Foraminiferal assemblages have high biodiversity, with Shannon-Wiener index varying from 2.51 to 3.20, α-Fisher index from 7.84 to 12.64 and Equitability from 0.37 to 0.77. Statistical analyses (cluster analysis and PCA) grouped foraminifera in two major assemblages, related to sediment type. On sandy and gravely substrates, assemblage is dominated by epifaunal genera and species: Quinqueloculina sp. (6-20%), Elphidium sp. (5-16%), Neoconorbina terquemi (6-10 %) and Asterigerinata mamilla (5-7%). Infaunal species, Ammonia beccarii (5-16%), Ammonia inflata (5-36%), Ammonia tepida (6-38%) and genus Haynesina sp. (6-31%) dominate assemblages in muddy sediments. The only reworked species Aubignyna planidorso is found in the shallowest part of Soline Bay, making 20 to 65% of the assemblage.

Inner-shelf ocean dynamics and seafloor morphologic changes during Hurricane Sandy

NASA Astrophysics Data System (ADS)

Warner, John C.; Schwab, William C.; List, Jeffrey H.; Safak, Ilgar; Liste, Maria; Baldwin, Wayne

2017-04-01

Hurricane Sandy was one of the most destructive hurricanes in US history, making landfall on the New Jersey coast on October 30, 2012. Storm impacts included several barrier island breaches, massive coastal erosion, and flooding. While changes to the subaerial landscape are relatively easily observed, storm-induced changes to the adjacent shoreface and inner continental shelf are more difficult to evaluate. These regions provide a framework for the coastal zone, are important for navigation, aggregate resources, marine ecosystems, and coastal evolution. Here we provide unprecedented perspective regarding regional inner continental shelf sediment dynamics based on both observations and numerical modeling over time scales associated with these types of large storm events. Oceanographic conditions and seafloor morphologic changes are evaluated using both a coupled atmospheric-ocean-wave-sediment numerical modeling system that covered spatial scales ranging from the entire US east coast (1000 s of km) to local domains (10 s of km). Additionally, the modeled response for the region offshore of Fire Island, NY was compared to observational analysis from a series of geologic surveys from that location. The geologic investigations conducted in 2011 and 2014 revealed lateral movement of sedimentary structures of distances up to 450 m and in water depths up to 30 m, and vertical changes in sediment thickness greater than 1 m in some locations. The modeling investigations utilize a system with grid refinement designed to simulate oceanographic conditions with progressively increasing resolutions for the entire US East Coast (5-km grid), the New York Bight (700-m grid), and offshore of Fire Island, NY (100-m grid), allowing larger scale dynamics to drive smaller scale coastal changes. Model results in the New York Bight identify maximum storm surge of up to 3 m, surface currents on the order of 2 ms-1 along the New Jersey coast, waves up to 8 m in height, and bottom stresses exceeding 10 Pa. Flow down the Hudson Shelf Valley is shown to result in convergent sediment transport and deposition along its axis. Modeled sediment redistribution along Fire Island showed erosion across the crests of inner shelf sand ridges and sedimentation in adjacent troughs, consistent with the geologic observations.

Seismic Characterization of the Terrebonne Mini-basin, a Hydrate Rich Depositional System in the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Dafov, L. N.; Eze, P. C.; Haines, S. S.; Graham, S. A.; McHargue, T.; Hosford Scheirer, A.

2017-12-01

Natural gas bearing hydrates are a focus of research as a potential source of energy and carbon storage because they occur globally in permafrost regions and marine sediment along every continent. This study focuses on the structural and stratigraphic architecture of the Terrebonne mini-basin, northwest Walker Ridge, Gulf of Mexico, to characterize the depositional architecture and to describe possible migration pathways for petroleum. Questions addressed include: a) continuity of sand layers b) effects of faulting and c) ponding versus fill and spill. To address these questions, seven of forty-two high resolution USGS 2D seismic lines were interpreted and then verified with WesternGeco 3D seismic data, yielding three qualitative models for the depositional environment of hydrate-bearing sand intervals. Deeper hydrate-bearing sand reservoirs were deposited as sheet-like turbidite lobes. Two shallower hydrate-bearing intervals display two possible depositional systems which form reservoirs- 1) sandy to muddy channel sealed laterally by muddy levees with associated sandy crevasse splays, and 2) ponded sandy lobes cut by channels filled with sand lags and mud. Additional observations in the 2D seismic include mass transport deposits and possible contourites. Salt movement facilitated mini-basin formation which was then ponded by sediment and followed by episodes of fill-and-spill and erosion. These seismic interpretations indicate periodic salt uplift. Overturn of salt along the northwestern edge of the basin resulted in thrust faults. The faults and erosional surfaces act as seals to reservoirs. The greatest volume of sandy reservoir potential occurs in sheet-like turbidite lobes with high lateral continuity, which facilitates updip migration of deep-sourced thermogenic gas along bedding surfaces. Channel levees serve as lateral seals to gas hydrate reservoirs, whereas faults, erosional surfaces, and shales provide vertical seals. Characterization of the Terrebonne Basin depositional system and basin fill dynamics will inform a 3D basin and petroleum system model through time. The Earth model may serve as a platform within which future lab and production test findings can be integrated.

Modelling high Arctic deep permafrost temperature sensitivity in Northeast Greenland based on experimental and field observations

NASA Astrophysics Data System (ADS)

Rasmussen, Laura Helene; Zhang, Wenxin; Hollesen, Jørgen; Cable, Stefanie; Hvidtfeldt Christiansen, Hanne; Jansson, Per-Erik; Elberling, Bo

2017-04-01

Permafrost affected areas in Greenland are expected to experience a marked temperature increase within decades. Most studies have considered near-surface permafrost sensitivity, whereas permafrost temperatures below the depths of zero annual amplitude is less studied despite being closely related to changes in near-surface conditions, such as changes in active layer thermal properties, soil moisture and snow depth. In this study, we measured the sensitivity of thermal conductivity (TC) to gravimetric water content (GWC) in frozen and thawed permafrost sediments from fine-sandy and gravelly deltaic and fine-sandy alluvial deposits in the Zackenberg valley, NE Greenland. We further calibrated a coupled heat and water transfer model, the "CoupModel", for one central delta sediment site with average snow depth and further forced it with meteorology from a nearby delta sediment site with a topographic snow accumulation. With the calibrated model, we simulated deep permafrost thermal dynamics in four 20-year scenarios with changes in surface temperature and active layer (AL) soil moisture: a) 3 °C warming and AL water table at 0.5 m depth; b) 3 °C warming and AL water table at 0.1 m depth; c) 6 °C warming and AL water table at 0.5 m depth and d) 6 °C warming and AL water table at 0.1 m depth. Our results indicate that frozen sediments have higher TC than thawed sediments. All sediments show a positive linear relation between TC and soil moisture when frozen, and a logarithmic one when thawed. Gravelly delta sediments were highly sensitive, but never reached above 12 % GWC, indicating a field effect of water retention capacity. Alluvial sediments are less sensitive to soil moisture than deltaic (fine and coarse) sediments, indicating the importance of unfrozen water in frozen sediment. The deltaic site with snow accumulation had 1 °C higher mean annual ground temperature than the average snow depth site. Permafrost temperature at the depth of 18 m increased with 1.5 °C and 3.5 °C in the scenarios with 3 °C and 6 °C warming, respectively. Increasing the soil moisture had no important additional effect to warming, although an increase in thermal offset was indicated. We conclude that below-ground sediment properties affect the sensitivity of TC to GWC, that surface temperature changes can influence the deep permafrost within a short time scale, and that differences in snow depth affect surface temperatures. Sediment type and the type of precipitation should thus be considered when estimating future High Arctic deep permafrost sensitivity.

Assessment of grass root effects on soil piping in sandy soils using the pinhole test

NASA Astrophysics Data System (ADS)

Bernatek-Jakiel, Anita; Vannoppen, Wouter; Poesen, Jean

2017-04-01

Soil piping is a complex land degradation process, which involves the hydraulic removal of soil particles by subsurface flow. This process is frequently underestimated and omitted in most soil erosion studies. However, during the last decades several studies reported the importance of soil piping in various climatic zones and for a wide range of soil types. Compared to sheet, rill and gully erosion, very few studies focused on the factors controlling piping and, so far, there is no research study dealing with the effects of plant roots on piping susceptibility of soils having a low cohesion. The objective of this study is therefore to assess the impact of grass root density (RD) on soil piping in sandy soils using the pinhole test. The pinhole test involves a water flow passing through a hole of 1 mm diameter in a soil specimen (sampled using a metal ring with a diameter of 5 cm and a length of 8 cm), under varying hydraulic heads (50 mm, 180 mm, 380 mm and 1020 mm; Nadal-Romero et al., 2011). To provide a quantitative assessment piping susceptibility of the soil sample, the pipeflow discharge (cm3 s-1) and the sediment discharge (g s-1) were measured every minute during a five minute test. Bare and root-permeated samples were tested, using a sandy soil with a sand, silt, clay content of respectively, 94%, 4% and 2%. The root-permeated topsoil samples were taken in field plots sown with a mixture of grasses with fibrous roots. All soil samples were placed on a sandbox with a 100 mm head for 24 hours to ensure a similar water content for all samples. In total, 67 pinhole tests (lasting 5 minutes each) were conducted, i.e. 43 root-permeated soil samples with RD ranging from 0.01 to 0.93 kg m-3 and 24 root-free soil samples as a reference. Clear piping erosion could be observed in 65% of the root-free soil samples, whereas only 17% of rooted soil samples revealed clear piping erosion during the tests. Statistical analyses show that there is a negative correlation (-0.41, p < 0.05) between RD and sediment discharge. Mean pipeflow discharge was 1.4 times larger for the root-free samples compared to the root-permeated samples, while mean sediment discharge was 3 times higher for the root-free samples compared to the rooted samples. This indicates that the presence of fibrous roots in topsoils decreases the susceptibility to soil piping significantly. Furthermore, a positive correlation between the hydraulic head (50-1020 mm) and sediment discharge was observed. Overall, our results suggest that root density is a highly relevant factor for decreasing the soil piping erosion rates in the sandy topsoils. The presence of even very low root densities (< 1 kg m3) decrease pipeflow and sediment discharge. A. Bernatek-Jakiel is supported by the ETIUDA doctoral scholarship (UMO-2015/16/T/ST10/00505) financed by the National Science Centre of Poland. Reference: Nadal-Romero, E., Verachtert, E., Maes, R., Poesen, J., 2011. Quantitative assessment of the piping erosion susceptibility of loess-derived soil horizons using the pinhole test. Geomorphology 135, 66-79.

Seasonal sedimentary processes of the macrotidal flat in Gomso Bay, west coast of Korea

NASA Astrophysics Data System (ADS)

Woo, H.; Kang, J.; Choi, J.

2012-12-01

The tidal flats on the west coast of Korea have broad zones with gentle slopes and a macrotidal setting with 4 to 10 meters of tidal ranges. They are directly influenced by monsoons and heavily affected by waves in winter and tidal currents in summer. As a result, most western tidal flats show the seasonal changes of sedimentary features comprising sedimentation and/or erosion of sediments. Gomso bay in the mid-west of Korea is a funnel-shaped embayment with a wide entrance to the west. Tides are semidiurnal and macrotidal, with a mean tidal range of 433.8 cm. Digital elevation model (DEM) showed that the landward inner bay had mainly high elevations and the seaward outer bay had relatively low elevations. In particular, there are considerable gradients in the outer bay from area of high-water line to area of low-water line. The sedimentary analysis and monitoring short-term sedimentation rates were investigated to understand seasonal sedimentary processes of tidal flats in Gomso bay. The surface sediments in the bay were classified into five sedimentary facies in spring 2011. Generally, sandy sediments were dominated in the outer bay, whereas sandy mud sediments were distributed on the inner bay. The middle bay mainly consisted of muddy sand sediments. The percentages of sand decreased from outer to inner bay. The short-term sedimentation rates were obtained from three lines by burying a plate at sub-bottom depth and periodically measuring the changing sediment depth from February 2011 to February 2012. In the tidal flat at inner bay (KB- Line), the annual sedimentation rates were ranged -8.87 to 74.69 mm/year with the net deposition rate of 40.90 mm/year. The deposition occurred on KB-Line in spring, autumn and winter. The erosion was dominated on the tidal flats at middle (KH-Line) and outer bay (KM-Line) during autumn and winter with an annual erosion rate of -29.86 mm/year and -9.92 mm/year, respectively. The seasonal variations of sedimentation on these tidal flats showed that the deposition occurred with an inflow of muddy sediments in summer, whereas the erosion was dominated in autumn and winter. In August 2011, the distribution patterns of rare earth elements (REEs) relative to the upper continental crust (UCC) showed the enrichment of light REEs (LREEs: La-Nd), together with an apparent depletion of Eu in the KH- and KM-Lines. This pattern was more pronounced in the middle bay sediments (KH-Line) due to influence of muddy sediment transport from Jujin Stream during the rainy period (July and August). On the other hand, the outer bay sediments in the KM-Line were reflected more inflow of second sediment source, the Geum River. The major control factors for seasonal variations of sediments on the tidal flat could be heavy rainfall and tidal currents during summer and strong waves during winter. The net sedimentation showed that the deposition occurred in the inner tidal flat and erosion occurred in the middle and outer tidal flat of the bay.

Anthropopression markers in lake bottom sediments

NASA Astrophysics Data System (ADS)

Nadolna, Anna; Nowicka, Barbara

2014-05-01

Lakes are vulnerable to various types of anthropogenic disturbances. Responses of lake ecosystems to environmental stressors are varied and depend not only on the type of a factor but also on the lake natural resistance to degradation. Within the EULAKES project an evaluation of anthropogenic stress extent in a flow-through, postglacial, ribbon lake (Lake Charzykowskie) was carried out. It was assumed, that this impact manifests unevenly, depending on a type and degree of the pressure on the shore zones, water quality of tributaries, lake basin shape and dynamics of a water movement. It was stated, that anthropogenic markers are substances accumulated in bottom sediments as a result of allochthonous substances inflow from the catchment and atmosphere. Along the selected transects 105 samples from the top layer of sediments (about 20 cm) was collected representing the contemporary accumulation (about 15 years). The content of selected chemical elements and compounds was examined, including nutrients (TN and TP), heavy metals (arsenic, cadmium, lead, chromium, nickel, copper, zinc, mercury, iron, and manganese) and pesticides (DDT, DDD, DDE, DMDT , γ-HCH). The research was conducted in the deepest points of each lake basin and along the research transects - while choosing the spots, the increased intensity of anthropogenic impact (ports, roads with heavy traffic, wastewater discharge zones, built-up areas) was taken into consideration. The river outlets to the lake, where there are ecotonal zones between limnic and fluvial environment, were also taken into account. Analysis of the markers distribution was carried out against the diversity of chemical characteristics of limnic sediments. Ribbon shape of the lake basin and the dominant wind direction provide an opportunity of easy water mixing to a considerable depth. Intensive waving processes cause removal of the matter from the littoral zone towards lake hollows (separated by the underwater tresholds), where the top layer of sediments consists of organic sediment ("sapropel" type). The littoral zone is dominated by sandy material from the shores denudation. In river mouths sandy deltas are formed. The most contaminated sediments are deposited in the central pool, which is a natural trap for the substances flowing with the river that is draining wastewaters from urban areas. At its mouth the sediment samples were significantly contaminated with chromium, zinc, cadmium, copper, nickel, lead and mercury. A high content of total phosphorus was also detected. A different role is played by a large river flowing through the lake. While flushing the sediments it reduces their pollution. The lowest content of markers was detected in headwater areas and in littoral zones exposed to waving.

A mega-nourishment creates novel habitat for intertidal macroinvertebrates by enhancing habitat relief of the sandy beach

NASA Astrophysics Data System (ADS)

van Egmond, E. M.; van Bodegom, P. M.; Berg, M. P.; Wijsman, J. W. M.; Leewis, L.; Janssen, G. M.; Aerts, R.

2018-07-01

Globally, sandy beaches are subject to coastal squeeze due to erosion. Soft-sediment strategies, such as sand nourishment, are increasingly applied to mitigate effects of erosion, but have long-term negative impacts on beach flora and fauna. As a more ecologically and sustainable alternative to regular beach nourishments, a mega-nourishment has been constructed along the Dutch coast by depositing 21.5 Mm3 of sand, from which sand is gradually redistributed along the coast by natural physical processes. The 'Sand Motor' mega-nourishment was constructed as a long-term management alternative for coastal protection and is the first large-scale experiment of its kind. We evaluated the development of intertidal macroinvertebrate communities in relation to this mega-nourishment, and compared it to species composition of beaches subject to regular beach or no nourishment. We found that a mega-nourishment resulted initially in a higher macroinvertebrate richness, but a lower macroinvertebrate abundance, compared to regular beach nourishment. As there was no effect of year after nourishment, this finding suggests that colonization and/or local extinction were not limiting macroinvertebrate richness at the mega-nourishment. In addition, a mega-nourishment does not converge to an intertidal macroinvertebrate community similar to those on unnourished beaches within a time scale of four years. Beach areas at the mega-nourishment sheltered from waves harbored a distinct macroinvertebrate community compared to typical wave-exposed sandy beach communities. Thus, a mega-nourishment temporally creates new habitat for intertidal macroinvertebrates by enhancing habitat relief of the sandy beach. We conclude that a mega-nourishment may be a promising coastal defense strategy for sandy shores in terms of the macroinvertebrate community of the intertidal beach.

Mechanics of dual-mode dilative failure in subaqueous sediment deposits

NASA Astrophysics Data System (ADS)

You, Yao; Flemings, Peter; Mohrig, David

2014-07-01

We introduce dual-mode dilative failure with flume experiments. Dual-mode dilative failure combines slow and steady release of sediments by breaching with periodic sliding, which rapidly releases an internally coherent wedge of sediments. It occurs in dilative sandy deposits. This periodic slope failure results from cyclic evolution of the excess pore pressure in the deposit. Sliding generates large, transient, negative excess pore pressure that strengthens the deposit and allows breaching to occur. During breaching, negative excess pore pressure dissipates, the deposit weakens, and ultimately sliding occurs once again. We show that the sliding frequency is proportional to the coefficient of consolidation. We find that thicker deposits are more susceptible to dual-mode dilative failure. Discovery of dual-mode dilative failure provides a new mechanism to consider when interpreting the sedimentary deposits linked to submarine slope failures.

116 years of misplaced management: Portballintrae, Northern Ireland

NASA Astrophysics Data System (ADS)

Jackson, D. W. T.

2012-04-01

Portballintrae has had a protracted history of human interference ranging from small-scale sand removal to hard coastal engineering. A small, horse shoe embayment and a once popular seaside destination on the north coast of Northern Ireland, it has suffered from progressive sediment loss over the last 116 years. From a once sediment abundant system, with a wide sandy beach, it now contains only a limited amount of sand draped over bedrock and/or gravel substrate and a relatively narrow beach. Installation of an obtrusive pier in its western section is thought to have interrupted the natural hydrody-namics and set in motion a progressive longshore transport and re-moval of sand into deeper water. Successive hard engineering 'solutions' prompted through public pressure and engineers keen to do business, have been largely ineffectual, located within a sediment-starved beach system.

Subtidal hydrodynamics in a tropical lagoon: A dimensionless numbers approach

NASA Astrophysics Data System (ADS)

Tenorio-Fernandez, L.; Valle-Levinson, A.; Gomez-Valdes, J.

2018-01-01

Observations in a tropical lagoon of the Yucatan peninsula motivated a non-dimensional number analysis to examine the relative influence of tidal stress, density gradients and wind stress on subtidal hydrodynamics. A two-month observation period in Chelem Lagoon covered the transition from the dry to the wet season. Chelem Lagoon is influenced by groundwater inputs and exhibits a main sub-basin (central sub-basin), a west sub-basin and an east sub-basin. Subtidal hydrodynamics were associated with horizontal density gradients that were modified seasonally by evaporation, precipitation, and groundwater discharge. A tidal Froude number (Fr0), a Wedderburn number (W), and a Stress ratio (S0) were used to diagnose the relative importance of dominant subtidal driving forces. The Froude number (Fr0) compares tidal forcing and baroclinic forcing through the ratio of tidal stress to longitudinal baroclinic pressure gradient. The Wedderburn number (W) relates wind stress to baroclinicity. The stress ratio (S0) sizes tidal stress and wind stress. S0 is a new diagnostic tool for systems influenced by tides and winds, and represents the main contribution of this research. Results show that spring-tide subtidal flows in the tropical lagoon had log(Fr0) ≫ 0 and log(S0) > 0 , i.e., driven mainly by tidal stresses (advective accelerations). Neap tides showed log(Fr0) ≪ 0 and log(S0) < 0) , i.e., flows driven by baroclinicity, especially at the lagoon heads of the east and west sub-basins. However, when the wind stress intensified over the lagoon, the relative importance of baroclinicity decreased and the wind stress controlled the dynamics (log(W) ≫ 0). Each sub-basin exhibited a different subtidal response, according to the dimensionless numbers. The response depended on the fortnightly tidal cycle, the location and magnitude of groundwater input, and the direction and magnitude of the wind stress.

Health assessment for Lake Sandy Jo Landfill, Gary, Indiana, Region 5. CERCLIS No. IND980500524. Final report

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

Not Available

1985-11-21

The 50-acre Lake Sandy Jo Landfill is located in the Black Oak community (predominantly residential) of southwestern Gary in Lake County, Indiana. From about 1971 until about 1980, the lake was filled in with construction and demolition debris, municipal garbage, industrial wastes, hazardous materials, and possibly drummed wastes. These wastes are partly to completely exposed on the landfill surface. Surface soil, subsurface soil, surface water, sediment, and ground water show a variety of metal and organic chemical carcinogens. Toxic noncarcinogen priority pollutants found were chloromethane, copper, cyanide, lead, mercury, and silver. Inorganic soil levels found on the site for leadmore » and cadmium exceed levels of concern that would permit unrestricted use of the site. Remedial measures would be necessary before the site could be granted unrestricted use.« less

Depositional environments and cyclicity of the Early Ordovician carbonate ramp in the western Tarim Basin (NW China)

NASA Astrophysics Data System (ADS)

Guo, Chuan; Chen, Daizhao; Song, Yafang; Zhou, Xiqiang; Ding, Yi; Zhang, Gongjing

2018-06-01

During the Early Ordovician, the Tarim Basin (NW China) was mainly occupied by an extensive shallow-water carbonate platform, on which a carbonate ramp system was developed in the Bachu-Keping area of the western part of the basin. Three well-exposed typical outcrop sections of the Lower Ordovician Penglaiba Formation were investigated in order to identify the depositional facies and to clarify origins of meter-scale cycles and depositional sequences, thereby the platform evolution. Thirteen lithofacies are identified and further grouped into three depositional facies (associations): peritidal, restricted and open-marine subtidal facies. These lithofacies are vertically stacked into meter-scale, shallowing-upward peritidal and subtidal cycles. The peritidal cycles are mainly distributed in the lower and uppermost parts of the Penglaiba Formation deposited in the inner-middle ramp, and commonly start with shallow subtidal to intertidal facies followed by inter- to supratidal facies. In contrast, the subtidal cycles occur throughout the formation mostly in the middle-outer ramp and are dominated by shallow to relatively deep (i.e., intermediate) subtidal facies. The dominance of asymmetrical and incomplete cycles suggests a dominant control of Earth's orbital forcing on the cyclic deposition on the platform. On the basis of vertical facies and cycle stacking patterns, and accommodation changes illustrated by the Fischer plots from all studied sections, five third-order depositional sequences are recognized in the Penglaiba Formation. Individual sequences comprise a lower transgressive part and an upper regressive one. In shallow-water depositional environments, the transgressive packages are dominated by thicker-than-average subtidal cycles, indicating an increase in accommodation space, whereas regressive parts are mainly represented by thinner-than-average peritidal and subtidal cycles, denoting a decrease in accommodation space. In contrast, in intermediate to deep subtidal environments, transgressive and regressive packages display an opposite trend in accommodation space changes. Sequence boundaries (except the basal and top boundaries of the Penglaiba Formation) are usually represented by laterally traceable, transitional boundary zones without apparent subaerial exposure features. Good correlation of the long-term changes in accommodation space (or sea-level) inferred from vertical stacking patterns of facies and cycles suggests an overriding eustatic control on the formation of meter-scale cycles and third-order depositional sequences as well as platform evolution superimposed with local and/or regional tectonic influence during the Early Ordovician. This study would help understand the controls on the tempo-spatial facies distribution, stratal cyclicity and carbonate platform evolution in the western Tarim Basin during the Early Ordovician, facilitating prediction for favorable subsurface carbonate reservoirs and future hydrocarbon exploration and production in the Penglaiba Formation.

Evaluating Tidal Marsh Sustainability in the Face of Sea-Level Rise: A Hybrid Modeling Approach Applied to San Francisco Bay

PubMed Central

Stralberg, Diana; Brennan, Matthew; Callaway, John C.; Wood, Julian K.; Schile, Lisa M.; Jongsomjit, Dennis; Kelly, Maggi; Parker, V. Thomas; Crooks, Stephen

2011-01-01

Background Tidal marshes will be threatened by increasing rates of sea-level rise (SLR) over the next century. Managers seek guidance on whether existing and restored marshes will be resilient under a range of potential future conditions, and on prioritizing marsh restoration and conservation activities. Methodology Building upon established models, we developed a hybrid approach that involves a mechanistic treatment of marsh accretion dynamics and incorporates spatial variation at a scale relevant for conservation and restoration decision-making. We applied this model to San Francisco Bay, using best-available elevation data and estimates of sediment supply and organic matter accumulation developed for 15 Bay subregions. Accretion models were run over 100 years for 70 combinations of starting elevation, mineral sediment, organic matter, and SLR assumptions. Results were applied spatially to evaluate eight Bay-wide climate change scenarios. Principal Findings Model results indicated that under a high rate of SLR (1.65 m/century), short-term restoration of diked subtidal baylands to mid marsh elevations (−0.2 m MHHW) could be achieved over the next century with sediment concentrations greater than 200 mg/L. However, suspended sediment concentrations greater than 300 mg/L would be required for 100-year mid marsh sustainability (i.e., no elevation loss). Organic matter accumulation had minimal impacts on this threshold. Bay-wide projections of marsh habitat area varied substantially, depending primarily on SLR and sediment assumptions. Across all scenarios, however, the model projected a shift in the mix of intertidal habitats, with a loss of high marsh and gains in low marsh and mudflats. Conclusions/Significance Results suggest a bleak prognosis for long-term natural tidal marsh sustainability under a high-SLR scenario. To minimize marsh loss, we recommend conserving adjacent uplands for marsh migration, redistributing dredged sediment to raise elevations, and concentrating restoration efforts in sediment-rich areas. To assist land managers, we developed a web-based decision support tool (www.prbo.org/sfbayslr). PMID:22110638

Effects of ghost shrimp on zinc and cadmium in sediments from Tampa Bay, FL

USGS Publications Warehouse

Klerks, P.L.; Felder, D.L.; Strasser, K.; Swarzenski, P.W.

2007-01-01

This study investigated the effects that ghost shrimp have on the distribution of metals in sediment. We measured levels of HNO3-extractable zinc and cadmium in surface sediment, in ghost shrimp burrow walls and in sediment ejected by the ghost shrimp from their burrows, at five sandy intertidal sites in Tampa Bay. Ghost shrimp densities and their rate of sediment ejection were also quantified, as were sediment organic content and silt + clay content. Densities of ghost shrimp (Sergio trilobata and Lepidophthalmus louisianensis) averaged 33/m2 at our sites, and they ejected sediment at an average rate of 28 g/burrow/day. Levels of both Zn and Cd were significantly higher in burrow walls than in surface sediments. Sediment ejected by the shrimp from their burrows had elevated levels of Zn (relative to surface sediments) at one of the sites. Sediment organic content and silt + clay content were higher in burrow-wall sediments than in ejected sediment, which in turn tended to have values above those of surface sediments. Differences in levels of HNO3-extractable Zn and Cd among sediment types may be a consequence of these sediments differing in other physiochemical characteristics, though the differences in metal levels remained statistically significant for some sites after correcting for differences in organic content and silt + clay content. We conclude that the presence of ghost shrimp burrows contributes to spatial heterogeneity of sedimentary metal levels, while the ghost shrimp bioturbation results in a significant flux of metals to the sediment surface and is expected to decrease heterogeneity of metal levels in sedimentary depth profiles.

Initial fluvial response to the removal of Oregon's Marmot Dam

Treesearch

Jon J. Major; Jim E. O' Connor; Gordon E. Grant; Kurt R. Spicer; Heather M. Bragg; Abagail Rhode; Dwight Q. Tanner; Chauncey W. Anderson; J. Rose Wallick

2008-01-01

A temporary, 14-meter-high earthen cofferdam standing in place of Marmot Dam was breached on 19 October 2007, allowing the 80-kilometer-long Sandy River to flow freely from Mount Hood, Oregon, to the Columbia River for the first time in nearly 100 years. Marmot Dam is one of the largest dams in the Western United States (in terms of height and volume of stored sediment...

Sound Speed and Attenuation in Multiphase Media

DTIC Science & Technology

2008-09-20

Stoll [2] report shear wave speeds between 100 to 300 m/s for sandy sediments with porosities of 40-50%. Hastrup [12:121-127] reports empirical...by a factor of 64. The importance of shear wave conversion in bottom reflection has been treated by Hastrup [12] while the depth dependent...843, 1962 [12] O. F. Hastrup , Acoustic Bottom Reflectivity, Technical Report SR-115 SACLANT Undersea Research Centre, La Spezia, Italy, 1986. [13

On the ecogeomorphological feedbacks that control tidal channel network evolution in a sandy mangrove setting

PubMed Central

van Maanen, B.; Coco, G.; Bryan, K. R.

2015-01-01

An ecomorphodynamic model was developed to study how Avicennia marina mangroves influence channel network evolution in sandy tidal embayments. The model accounts for the effects of mangrove trees on tidal flow patterns and sediment dynamics. Mangrove growth is in turn controlled by hydrodynamic conditions. The presence of mangroves was found to enhance the initiation and branching of tidal channels, partly because the extra flow resistance in mangrove forests favours flow concentration, and thus sediment erosion in between vegetated areas. The enhanced branching of channels is also the result of a vegetation-induced increase in erosion threshold. On the other hand, this reduction in bed erodibility, together with the soil expansion driven by organic matter production, reduces the landward expansion of channels. The ongoing accretion in mangrove forests ultimately drives a reduction in tidal prism and an overall retreat of the channel network. During sea-level rise, mangroves can potentially enhance the ability of the soil surface to maintain an elevation within the upper portion of the intertidal zone, while hindering both the branching and headward erosion of the landward expanding channels. The modelling results presented here indicate the critical control exerted by ecogeomorphological interactions in driving landscape evolution. PMID:26339195

Nest substrate reflects incubation style in extant archosaurs with implications for dinosaur nesting habits.

PubMed

Tanaka, Kohei; Zelenitsky, Darla K; Therrien, François; Kobayashi, Yoshitsugu

2018-03-15

Dinosaurs thrived and reproduced in various regions worldwide, including the Arctic. In order to understand their nesting in diverse or extreme environments, the relationships between nests, nesting environments, and incubation methods in extant archosaurs were investigated. Statistical analyses reveal that species of extant covered nesters (i.e., crocodylians and megapodes) preferentially select specific sediments/substrates as a function of their nesting style and incubation heat sources. Relationships between dinosaur eggs and the sediments in which they occur reveal that hadrosaurs and some sauropods (i.e., megaloolithid eggs) built organic-rich mound nests that relied on microbial decay for incubation, whereas other sauropods (i.e., faveoloolithid eggs) built sandy in-filled hole nests that relied on solar or potentially geothermal heat for incubation. Paleogeographic distribution of mound nests and sandy in-filled hole nests in dinosaurs reveals these nest types produced sufficient incubation heat to be successful up to mid latitudes (≤47°), 10° higher than covered nesters today. However, only mound nesting and likely brooding could have produced sufficient incubation heat for nesting above the polar circle (>66°). As a result, differences in nesting styles may have placed restrictions on the reproduction of dinosaurs and their dispersal at high latitudes.

Sedimentary facies and Holocene progradation rates of the Changjiang (Yangtze) delta, China

NASA Astrophysics Data System (ADS)

Hori, Kazuaki; Saito, Yoshiki; Zhao, Quanhong; Cheng, Xinrong; Wang, Pinxian; Sato, Yoshio; Li, Congxian

2001-11-01

The Changjiang (Yangtze) River, one of the largest rivers in the world, has formed a broad tide-dominated delta at its mouth during the Holocene sea-level highstand. Three boreholes (CM97, JS98, and HQ98) were obtained from the Changjiang delta plain in 1997-1998 to clarify the characteristics of tide-dominated delta sediments and architecture. Based on sediment composition and texture, and faunal content, core sediments were divided into six depositional units. In ascending order, they were interpreted as tidal sand ridge, prodelta, delta-front, subtidal to lower intertidal flat, upper intertidal flat, and surface soil deposits. The deltaic sequence from the prodelta deposits to the delta front deposits showed an upward-coarsening succession, overlain by an upward-fining succession from the uppermost part of the delta front deposits to the surface soil. Thinly interlaminated to thinly interbedded sand and mud (sand-mud couplets), and bidirectional cross laminations in these deposits show that tide is the key factor affecting the formation of Changjiang deltaic facies. Sediment facies and their succession combined with AMS 14C dating revealed that isochron lines cross unit boundaries clearly, and delta progradation has occurred since about 6000 to 7000 years BP, when the rising sea level neared or reached its present position. The average progradation rate of the delta front was approximately 50 km/kyear over the last 5000 years. The progradation rate, however, increased abruptly ca. 2000 years BP, going from 38 to 80 km/kyear. The possible causes for this active progradation could have been an increase in sediment production in the drainage basin due to widespread human interference and/or decrease in deposition in the middle reaches related to the channel stability caused by human activity and climatic cooling after the mid-Holocene.

Removal of Fast Flowing Nitrogen from Marshes Restored in Sandy Soils

PubMed Central

Sparks, Eric L.; Cebrian, Just; Smith, Sara M.

2014-01-01

Groundwater flow rates and nitrate removal capacity from an introduced solution were examined for five marsh restoration designs and unvegetated plots shortly after planting and 1 year post-planting. The restoration site was a sandy beach with a wave-dampening fence 10 m offshore. Simulated groundwater flow into the marsh was introduced at a rate to mimic intense rainfall events. Restoration designs varied in initial planting density and corresponded to 25%, 50%, 75% and 100% of the plot area planted. In general, groundwater flow was slower with increasing planting density and decreased from year 0 to year 1 across all treatments. Nevertheless, removal of nitrate from the introduced solution was similar and low for all restoration designs (3–7%) and similar to the unvegetated plots. We suggest that the low NO3 − removal was due to sandy sediments allowing rapid flow of groundwater through the marsh rhizosphere, thereby decreasing the contact time of the NO3 − with the marsh biota. Our findings demonstrate that knowledge of the groundwater flow regime for restoration projects is essential when nutrient filtration is a target goal of the project. PMID:25353607

Heavy mineral analysis for assessing the provenance of sandy sediment in the San Francisco Bay Coastal System

USGS Publications Warehouse

Wong, Florence L.; Woodrow, Donald L.; McGann, Mary

2013-01-01

Heavy or high-specific gravity minerals make up a small but diagnostic component of sediment that is well suited for determining the provenance and distribution of sediment transported through estuarine and coastal systems worldwide. By this means, we see that surficial sand-sized sediment in the San Francisco Bay Coastal System comes primarily from the Sierra Nevada and associated terranes by way of the Sacramento and San Joaquin Rivers and is transported with little dilution through the San Francisco Bay and out the Golden Gate. Heavy minerals document a slight change from the strictly Sierran-Sacramento mineralogy at the confluence of the two rivers to a composition that includes minor amounts of chert and other Franciscan Complex components west of Carquinez Strait. Between Carquinez Strait and the San Francisco Bar, Sierran sediment is intermingled with Franciscan-modified Sierran sediment. The latter continues out the Gate and turns southward towards beaches of the San Francisco Peninsula. The Sierran sediment also fans out from the San Francisco Bar to merge with a Sierran province on the shelf in the Gulf of the Farallones. Beach-sand sized sediment from the Russian River is transported southward to Point Reyes where it spreads out to define a Franciscan sediment province on the shelf, but does not continue southward to contribute to the sediment in the Golden Gate area.

Spatial-temporal evolution of the eastern Nanhui mudflat in the Changjiang (Yangtze River) Estuary under intensified human activities

NASA Astrophysics Data System (ADS)

Zhang, Xiaodong; Zhang, Yexin; Zhu, Longhai; Chi, Wanqing; Yang, Zuosheng; Wang, Biying; Lv, Kai; Wang, Hongmin; Lu, Zhiyong

2018-05-01

The eastern Nanhui mudflat (ENM), located in the southern flank of the Changjiang (Yangtze River) Estuary, plays a key role in storm protection, defense against sea level rise, and land resource provision for Shanghai, China's largest city. Recently, there has been a great deal of concern for its evolutionary fate, since a drastic reduction in the Changjiang sediment discharge rate and an increased number of estuarine enclosures might negatively impact the environmental protection functions that this mudflat provides. In this paper, a novel method, which employed the envelope lines of instantaneous shoreline positions identified in 436 Landsat satellite images from 1975 to 2016, was used to demonstrate the evolution of the mudflat high and low tide lines in a detailed, quantitative way. Our study reveals the southeast progradation rate of the mudflat doubled from 24 m/yr in 713-1974 CE to 49 m/yr in 1975-1995 CE, probably due to the influence of the estuarine turbidity maximum zone shifting to the ENM. Under the ample sediment input directly from the turbidity maximum zone, the spatial evolution of the ENM was governed predominantly by the changing morphology of the South Passage due to the quick progradation of the ENM, which narrowed the South Passage by pushing the South Passage Trumpet southeastward. Therefore, the ENM experienced rapid accretion during 1975-2016. The accretion rate of the high tide line increased 2-13 times due to vegetation and intertidal enclosures, resulting in the rapid reduction of the intertidal area. The area decreased from 97 km2 in 1976 to 66 km2 in 1995, mainly due to vegetation, and continued decreasing to 12 km2 in 2006 due to the intertidal enclosures. In contrast, the accretion rate of the low tide line increased by 25 times due to subtidal enclosures and caused the intertidal area increased to 78 km2 in 2015. The almost disappeared intertidal zones in 2006 reappeared. However, this reappearance might be a temporary transitional state, and once the subtidal enclosures are completed, most of the intertidal zones will be replaced by enclosure land. Our study reveals that the drastic reduction in the Changjiang sediment flow to the sea has not caused a decline in the ENM. In contrast, the ENM has experienced rapid accretion in the past 40 years, resulting in the strengthening of its functional abilities to protect Shanghai, an unexpected outcome.

Coastal ocean transport patterns in the central Southern California Bight

USGS Publications Warehouse

Noble, M.A.; Rosenberger, K.J.; Hamilton, P.; Xu, J. P.

2009-01-01

In the past decade, several large programs that monitor currents and transport patterns for periods from a few months to a few years were conducted by a consortium of university, federal, state, and municipal agencies in the central Southern California Bight, a heavily urbanized section of the coastal ocean off the west coast of the United States encompassing Santa Monica Bay, San Pedro Bay, and the Palos Verdes shelf. These programs were designed in part to determine how alongshelf and cross-shelf currents move sediments, pollutants, and suspended material through the region. Analysis of the data sets showed that the current patterns in this portion of the Bight have distinct changes in frequency and amplitude with location, in part because the topography of the shelf and upper slope varies rapidly over small spatial scales. However, because the mean, subtidal, and tidal-current patterns in any particular location were reasonably stable with time, one could determine a regional pattern for these current fields in the central Southern California Bight even though measurements at the various locations were obtained at different times. In particular, because the mean near-surface flows over the San Pedro and Palos Verdes shelves are divergent, near-surface waters from the upper slope tend to carry suspended material onto the shelf in the northwestern portion of San Pedro Bay. Water and suspended material are also carried off the shelf by the mean and subtidal flow fields in places where the orientation of the shelf break changes abruptly. The barotropic tidal currents in the central Southern California Bight flow primarily alongshore, but they have pronounced amplitude variations over relatively small changes in alongshelf location that are not totally predicted by numerical tidal models. Nonlinear internal tides and internal bores at tidal frequencies are oriented more across the shelf. They do not have a uniform transport direction, since they move fine sediment from the shelf to the slope in Santa Monica Bay, but carry suspended material from the mid-shelf to the beach in San Pedro Bay. It is clear that there are a large variety of processes that transport sediments and contaminants along and across the shelf in the central Southern California Bight. However, because these processes have a variety of frequencies and relatively small spatial scales, the dominant transport processes tend to be localized and have dissimilar characteristics even in adjacent regions of this small part of the coastal ocean. ?? 2009 The Geological Society of America.

Identifying tectonic and climatic drivers for deep-marine siliciclastic systems: Middle Eocene, Spanish Pyrenees

NASA Astrophysics Data System (ADS)

Pickering, K. T.; Scotchman, J. I.; Robinson, S. A.

2009-12-01

Analysis of the sedimentary record in deep time requires the deconvolution of tectonic and climatic drivers. The deep-marine siliciclastic systems in the Middle Eocene Ainsa-Jaca basin, Spanish Pyrenees, with their excellent outcrops and good temporal resolution, provide an opportunity to identify the relative importance of tectonic and climatic drivers on deposition over ~10 Myr at a time when the Earth’s climate was shifting from a greenhouse to icehouse conditions. The cumulative ~4 km of stratigraphy contains 8 sandy systems with a total of ~25 discrete channelized sandbodies that accumulated in water depths of ~400-800 m, and that were controlled by the ~400-kyr Milkankovitch frequency with modes, at ~100 kyr and ~41 kyr (possibly stacked ~23-kyr) influencing bottom-water conditions, causing periodic stratification in the water column across a submarine sill within the eastern, more proximal depositional systems in the Ainsa basin. We also identify a range of sub-Milankovitch millennial-scale cycles (Scotchman et al. 2009). In the Ainsa basin, the interplay of basin-bounding growth anticlines defined and controlled the position and stacking patterns of the sandy systems and their constituent channelized sandbodies, in a process of seesaw tectonics by: (i) Westward lateral offset-stacking of channelized sandbodies due to growth of the eastern anticline (Mediano), and (ii) Eastward (orogenwards) back-stepping of the depositional axis of each sandy system, due to phases of relative uplift of the opposing Boltaña growth anticline. The first-order control on accommodation, and the flow paths, for deep-marine sedimentation were tectonic, with the pacing of the supply of coarse siliciclastics being driven by global climatic processes, particularly Milankovitch-type frequencies. The dominance of eccentricity and obliquity is similar to results from the continental lacustrine Eocene Green River Formation, and the observations from ODP Site 1258 that the early to middle Eocene climatic record is characterized by eccentricity-modulated precession cycles (Westerhold & Rohl 2009), The age model for the Ainsa basin yields an average sediment accumulation rate of ~40 cm kyr-1, that is consistent with that inferred from the spectral analysis on bioturbation intensity for fine-grained sedimentation (~30 cm kyr-1). References Scotchman, J.I., Pickering, K.T. & Robinson, S.A. 2009. Sub-Milankovitch millennial-scale climate variability in Middle Eocene deep-marine sediments. AGU Fall Meeting San Francisco 2009. Westerhold, T. & Rohl, U. 2009. High resolution cyclostratigraphy of the early Eocene - new insights into the origin of the Cenozoic cooling trend. Climate of the Past, 5, 309-327.

Distribution and relationships of trace metals in the isopod Saduria entomon and adjacent bottom sediments in the southern Baltic.

PubMed

Góral, Marta; Szefer, Piotr; Ciesielski, Tomasz; Warzocha, Jan

2009-10-01

The concentrations of Ag, Cd, Co, Cr, Cu, Fe, Ni, Pb, Mn and Zn in Saduria entomon and adjacent bottom sediments from the southern Baltic were determined by FAAS. In order to estimate the strength of correlations between accumulated elements in these crustaceans and surficial sediment, bioaccumulation factors (BAFs) were calculated. The results of factor analysis (FA) and the Kruskal-Wallis analysis of variance (ANOVA) clearly indicate geographical differences between the concentrations of these elements. Cd, Co, Fe, Ni, Pb and Zn levels were higher in S. entomon from the Gulf of Gdańsk, whereas Cr and Mn levels were higher in the crustaceans inhabiting open Baltic waters. The concentrations of Ag and Cu were comparable in both regions. There was a tendency for metal concentrations to distinguish organisms inhabiting the muddy bottom from those living in sandy sediments. The granulometric composition of the sediment appears to influence trace metal bioavailability. The results show that S. entomon could be a valuable sentinel organism for biomonitoring heavy metal contamination in the southern Baltic.

PCDD/F and dioxin-like PCB bioaccumulation by Manila clam from polluted areas of Venice lagoon (Italy).

PubMed

Sfriso, Adriano; Facca, Chiara; Raccanelli, Stefano

2014-01-01

POP bioaccumulation pathways in the clam Tapes philippinarum were examined for two years from juveniles to adult size. Two polluted sites, one with sandy sediment, the other muddy were compared with a reference site characterized by low contamination levels. Juvenile clams coming from a hatchery were reared both on the sediment and in nets suspended at 30 cm from the bottom. POP changes in clam tissue were related to the concentrations recorded in sediments and in the particulate matter during the entire fattening period. Results provided interesting data on the relationships between environmental contamination and bioaccumulation. Contrary to studies on the decontamination times of the clams collected in polluted areas, this work investigates the preferential clam bioaccumulation pathways during growth under different environmental conditions. In general POP bioaccumulation resulted to be correlated to concentrations in SPM rather than in sediments and was higher in S-clams rather than in B-clams. Copyright © 2013 Elsevier Ltd. All rights reserved.

Puzzling mass movement features in the Navarinsky Canyon head, Bering Sea

USGS Publications Warehouse

Carlson, P.R.; Karl, Herman A.; Edwards, B.D.

1982-01-01

Two types of morphologic features in the head of Navarinsky Canyon are attributed to mass movement of near-surface sediment. A series of pull-aparts is located downslope of large sand waves. These pull-aparts, possibly induced by liquefaction, affect the upper 5 to 10 m of sandy sediment (water depths 350 to 600 m) on a 1o slope. A hummocky elongate mound of muddy sand (water depths 550 to 800 m) contains chaotic internal reflectors to a subbottom depth of 30 to 40 m and possibly is the product of a shallow slide. We speculate that Holocene seismicity is the likely triggering mechanism. ?? 1982 A. M. Dowden, Inc.

Coastal and Estuarine Mangrove Squeeze in the Mekong and Saigon Delta

NASA Astrophysics Data System (ADS)

Stive, M.

2016-02-01

Both in the Mekong and Saigon deltas coastal squeeze is a frequent and pregnant problem, which leads to amazingly alarmous coastal and estuarine erosion rates. From the landside the squeeze is due to encroaching dike relocations and agri- and aquacultures, from the sea side it is due to decreasing sediment sources and relative sea level rise. These multiple pressures at some locations, certainly away from the sediment sources (like Ca Mau) leads to unprecedentent erosion rates. Managed retreat may be a longer term solution, but this will require a new way of thinking. Sandy and silt nourishment strategies may be an innovative alternative, but will require underbuilding scientific and practical research.

Role of macrofauna on benthic oxygen consumption in sandy sediments of a high-energy tidal beach

NASA Astrophysics Data System (ADS)

Charbonnier, Céline; Lavesque, Nicolas; Anschutz, Pierre; Bachelet, Guy; Lecroart, Pascal

2016-06-01

Sandy beaches exposed to tide and waves are characterized by low abundance and diversity of benthic macrofauna, because of high-energy conditions. This is the reason why there are few studies on benthic communities living in such highly dynamic environments. It has been shown recently that tidal sandy beaches may act as biogeochemical reactors. Marine organic matter that is supplied in the sand during each flood tide is efficiently mineralized through aerobic respiration. In order to quantify the role of macrofauna in the whole beach benthic respiration, we studied the macrofauna and the pore water oxygen content of an exposed sandy beach (Truc Vert, SW of France) during four seasons in 2011. The results showed that macrofauna was characterised by a low number of species of specialized organisms such as the crustaceans Eurydice naylori and Gastrosaccus spp. and the polychaetes Ophelia bicornis and Scolelepis squamata. The distribution and abundance of macrofauna were clearly affected by exposure degree and emersion time. The combined monitoring of benthic macrofauna and pore waters chemistry allowed us to estimate (1) the macrofauna oxygen uptake, calculated with a standard allometric relationship using biomass data, and (2) the total benthic oxygen uptake, calculated from the oxygen deficit measured in pore waters. This revealed that benthic macrofauna respiration represented a variable but low (<10%) contribution to the total benthic oxygen consumption. This suggests that oxygen was mainly consumed by microbial respiration.

Stream-sediment geochemistry in mining-impacted streams : sediment mobilized by floods in the Coeur d'Alene-Spokane River system, Idaho and Washington

USGS Publications Warehouse

Box, Stephen E.; Bookstrom, Arthur A.; Ikramuddin, Mohammed

2005-01-01

Environmental problems associated with the dispersion of metal-enriched sediment into the Coeur d'Alene-Spokane River system downstream from the Coeur d'Alene Mining District in northern Idaho have been a cause of litigation since 1903, 18 years after the initiation of mining for lead, zinc, and silver. Although direct dumping of waste materials into the river by active mining operations stopped in 1968, metal-enriched sediment continues to be mobilized during times of high runoff and deposited on valley flood plains and in Coeur d'Alene Lake (Horowitz and others, 1993). To gauge the geographic and temporal variations in the metal contents of flood sediment and to provide constraints on the sources and processes responsible for those variations, we collected samples of suspended sediment and overbank deposits during and after four high-flow events in 1995, 1996, and 1997 in the Coeur d'Alene-Spokane River system with estimated recurrence intervals ranging from 2 to 100 years. Suspended sediment enriched in lead, zinc, silver, antimony, arsenic, cadmium, and copper was detected over a distance of more than 130 mi (the downstream extent of sampling) downstream of the mining district. Strong correlations of all these elements in suspended sediment with each other and with iron and manganese are apparent when samples are grouped by reach (tributaries to the South Fork of the Coeur d'Alene River, the South Fork of the Coeur d'Alene River, the main stem of the Coeur d'Alene River, and the Spokane River). Elemental correlations with iron and manganese, along with observations by scanning electron microscopy, indicate that most of the trace metals are associated with Fe and Mn oxyhydroxide compounds. Changes in elemental correlations by reach suggest that the sources of metal-enriched sediment change along the length of the drainage. Metal contents of suspended sediment generally increase through the mining district along the South Fork of the Coeur d'Alene River, decrease below the confluence of the North and South Forks, and then increase again downstream of the gradient flattening below Cataldo. Metal contents of suspended sediment in the Spokane River below Coeur d'Alene Lake were comparable to those of suspended sediment in the main stem of the Coeur d'Alene River above the lake during the 1997 spring runoff, but with somewhat higher Zn contents. Daily suspended-sediment loads were about 100 times larger in the 1996 flood (50-100-year recurrence interval) than in the smaller 1997 floods (2-5-year recurrence intervals). Significant differences in metal ratios and contents are also apparent between the two flood types. The predominant source of suspended sediment in the larger 1996 flood was previously deposited, metal-enriched flood-plain sediment, identified by its Zn/Pb ratio less than 1. Suspended sediment in the smaller 1997 floods had metal ratios distinct from those of the flood-plain deposits and was primarily derived from metal-enriched sediment stored within the stream channel, identified by a Zn/Pb ratio greater than 1. Sediment deposited during overbank flooding on the immediate streambank or natural levee of the river typically consists of sandy material with metal ratios and contents similar to those of the sandy streambed sediment in the adjacent river reach. Samples of overbank deposits in backlevee marshes collected after the 1996 flood have metal ratios similar to those of peak-flow suspended sediment in the same river reach, but generally lower metal contents.

High-resolution geophysical data from the inner continental shelf—Buzzards Bay, Massachusetts

USGS Publications Warehouse

Ackerman, Seth D.; Andrews, Brian D.; Foster, David S.; Baldwin, Wayne E.; Schwab, William C.

2012-01-01

The U.S. Geological Survey (USGS) and the Massachusetts Office of Coastal Zone Management (CZM) have cooperated to map approximately 410 square kilometers (km²) of the inner continental shelf in Buzzards Bay, Massachusetts. This report contains geophysical data collected by the USGS on three cruises conducted in 2009, 2010, and 2011, and additional bathymetry data collected by the National Oceanic and Atmospheric Administration in 2004. The geophysical data include (1) swath bathymetry using interferometric sonar and multibeam echosounder systems, (2) acoustic backscatter from sidescan sonar, and (3) seismic-reflection profiles from a chirp subbottom profiler. These spatial data support research on the Quaternary evolution of Buzzards Bay, the influence of sea-level change and sediment supply on coastal evolution, and efforts to understand the type, distribution, and quality of subtidal marine habitats in the coastal ocean of Massachusetts.

Upper temperature limits of tropical marine ectotherms: global warming implications.

PubMed

Nguyen, Khanh Dung T; Morley, Simon A; Lai, Chien-Houng; Clark, Melody S; Tan, Koh Siang; Bates, Amanda E; Peck, Lloyd S

2011-01-01

Animal physiology, ecology and evolution are affected by temperature and it is expected that community structure will be strongly influenced by global warming. This is particularly relevant in the tropics, where organisms are already living close to their upper temperature limits and hence are highly vulnerable to rising temperature. Here we present data on upper temperature limits of 34 tropical marine ectotherm species from seven phyla living in intertidal and subtidal habitats. Short term thermal tolerances and vertical distributions were correlated, i.e., upper shore animals have higher thermal tolerance than lower shore and subtidal animals; however, animals, despite their respective tidal height, were susceptible to the same temperature in the long term. When temperatures were raised by 1°C hour(-1), the upper lethal temperature range of intertidal ectotherms was 41-52°C, but this range was narrower and reduced to 37-41°C in subtidal animals. The rate of temperature change, however, affected intertidal and subtidal animals differently. In chronic heating experiments when temperature was raised weekly or monthly instead of every hour, upper temperature limits of subtidal species decreased from 40°C to 35.4°C, while the decrease was more than 10°C in high shore organisms. Hence in the long term, activity and survival of tropical marine organisms could be compromised just 2-3°C above present seawater temperatures. Differences between animals from environments that experience different levels of temperature variability suggest that the physiological mechanisms underlying thermal sensitivity may vary at different rates of warming.

Propagation of Tidal and Subtidal Free Surface Oscillations into River Channels from the South Atlantic Bight

NASA Astrophysics Data System (ADS)

Iyer, S. K.; Cloarec, M.; Yankovsky, A. E.

2014-12-01

Tidal sea level oscillations propagate from continental shelves into river channels in the form of long gravity waves well beyond the limits of salt intrusion. These dynamics were a focus of numerous recent studies, which led to the development of the "tidal river" concept. Subtidal oscillations in the "weather" frequency band (periods from a few days to a few weeks) can exhibit similar propagation upstream the river channel, but have so far attracted less attention from researchers. In this work, we analyze data obtained from USGS stream gauge stations at several rivers flowing into the South Atlantic Bight along with NOAA tide gauge stations located on the adjacent coastline. Subtidal free surface oscillations in river channels decay at a slower rate than tidal oscillations (referenced to their amplitude on the coast), while their propagation speed is lower than at tidal frequencies. Potential to kinetic energy ratio sufficiently far upstream in the river channel becomes comparable for tidal and subtidal oscillations, as effects of earth's rotation become negligible. The results suggest that a coastal storm surge can cause more severe flooding inland along the river channel than tides with comparable coastal amplitude.

Stratigraphy and sedimentation of Mississippian Ste. Genevieve-Cedar Bluff interval, Southwestern Indiana

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

Breedon, D.; Droste, J.B.; Murray, H.H.

1983-09-01

The Ste. Genevieve Limestone and Cedar Bluff Group of Mississippian age, both important sources of hydrocarbons in the Illinois basin, were traced from a subsurface stratigraphic section in White County, Illinois (described by Swan in 1963, across Gibson and Daviess Counties, Indiana, using electric logs and sample descriptions from 84 wells. The Ste. Genevieve Limestone is subdivided into four members and the Cedar Bluff Group into three formations. Six cross sections and nine isopach maps based on 300 wells show that these units comprise a succession of alternating fine- and coarse-grained carbonate rocks with only minor interruptions of sandstone andmore » shale. Two complete coarsening-upward cycles are apparent, and a third cycle is incomplete. Each cycle consists of a lower sequence of lime mudstones and wackestones, and an upper sequence of oolitic and skeletal grainstones. These cycles are the record of successive shoaling-upward cycles of sedimentation on a shallow marine platform. The lower mudstone-wackestone sequence represents deposition in a shallow subtidal environment, and the upper oolitic-skeletal grainstone unit represents development of oolite shoals and tidal channels in very shallow waters. Terrigenous clastic sediments brought into the basin by the Michigan river periodically encroached into the marine environment. Dolomitization of the fine-grained carbonate sediments is largely restricted to areas which are overlain by oolitic grainstones. In eastern Daviess County, indentification of the individual stratigraphic units in this interval is somewhat tenuous, but tracing the units from eastern Illinois into Indiana made correlation and identification of the individual stratigraphic units possible by using electric logs and sample descriptions.« less

Dispersal of post-larval macrobenthos in subtidal sedimentary habitats: Roles of vertical diel migration, water column, bedload transport and biological traits' expression

NASA Astrophysics Data System (ADS)

Pacheco, Aldo S.; Uribe, Roberto A.; Thiel, Martin; Oliva, Marcelo E.; Riascos, Jose M.

2013-03-01

Post-larval dispersal along the sediment-water interface is an important process in the dynamics of macrobenthic populations and communities in marine sublittoral sediments. However, the modes of post-larval dispersal in low energy sublittoral habitats have been poorly documented. Herein we examined the specific dispersal mechanisms (diel vertical migration, water column, and bedload transport) and corresponding biological traits of the dispersing assemblage. At two sublittoral sites (sheltered and exposed) along the northern coast of Chile, we installed different trap types that capture benthic organisms with specific modes of dispersal (active emergence and passive water column drifting) and also by a combination of mechanisms (bedload transport, passive suspension and settlement from the water column). Our results show that even though there were common species in all types of traps, the post-larval macrobenthic assemblage depended on specific mechanisms of dispersal. At the sheltered site, abundant emerging taxa colonized sediments that were placed 0.5 m above the bottom and bedload-transported invertebrates appeared to be associated to the passive drifting of macroalgae. At the exposed site, assemblage dispersal was driven by specific mechanisms e.g. bedload transport and active emergence. At both sites the biological traits "small size, swimming, hard exoskeleton, free living and surface position" were associated to water column and bedload dispersal. This study highlights the importance of (i) the water-sediment interface for dispersal of post-larvae in sublittoral soft-bottom habitat, and (ii) a specific set of biological traits when dispersing either along the bottom or through the water column.

Small-scale seismogenic soft sediment deformation (Hirlatzhöhle, Upper Austria)

NASA Astrophysics Data System (ADS)

Salomon, Martina Lan; Grasemann, Bernhard; Plan, Lukas; Gier, Susanne

2014-05-01

The Hirlatz Cave lies in the Dachstein Massif about 2 km SW of Hallstatt, in the Upper Austrian Salzkammergut. With a length of 101 km, this karst cave, located in the Dachstein nappe (Northern Calcareous Alps), is the second largest known cave system in Austria. Within the cave, in the so-called Lehmklamm, located 2.8 km southeast of the cave entrance, laminated (mm-scale) Quaternary clay-sized sediments with interbedded fine-grained sandy layers are preserved. In these layers, numerous soft sediment deformation structures are preserved in many layers. The unconsolidated sediments show rhythmic layering of brighter, carbonate and quartz rich, and darker, more clay mineral rich horizontal varve-like layers, that are assumed to be fluvio-lacustrine deposits. The present study focuses on a very detailed documentation of an approximately 6.8 x 3 m vertical outcrop that was cut by a small brook. Centimeter to millimeter sized water escape structures (intruded cusps and flame structures), folds (detachment folds, fault bend folds) and faults (normal faults, fault propagation folds, bookshelf faults) are described. Because of the geometric analogy to seismogenic structures which have been described at two orders of magnitude larger scales from areas close to the Dead Sea Fault, we suggest that the formation of the investigated soft-sediment structures was also triggered by seismic events. The structures were mainly formed by three different mechanism: (i) North directed gravitational gliding near the sediment surface; (ii) Liquefaction resulting in a density discontinuity and decreasing in shear strength within in the stratified layers; (iii) Extensional faulting that cut through the stratified layers. Observations of coarsening upwards into sandy layers on the top of the outcrop and current ripple indicate a north-directed flow under phreatic conditions, which is opposite to the present flow direction of the vadose water in the cave. The fact that deformation and erosion mostly occur in the uppermost meter of the outcrop wall suggests a higher seismic activity and at least periodically higher flow rates during sedimentation of the younger deposits. Since several extremely deformed layers occur between undeformed ones, we suggest that deformation of the layers occurred only in the uppermost highly water saturated sediments and that several seismic events lead to the formation of the observed structures. A possible source responsible for the seismic event is the Salzach-Ennstal-Mariazeller-Puchberger (SEMP) strike-slip fault, which accommodates the active extrusion of the Eastern Alps towards the Pannonian Basin.

The Tsitsikamma coastal shelf, Agulhas Bank, South Africa: example of an isolated Holocene sediment trap

NASA Astrophysics Data System (ADS)

Flemming, Burg W.; Keith Martin, A.

2018-02-01

Under certain geomorphological conditions, sandy sediments supplied to a coast may become trapped in nearshore sedimentary compartments because these are laterally confined by bedload boundaries or convergences. Where sediment supply is small or the shoreface very steep, and accommodation space as a consequence large, the trapping mechanism may be very efficient. The Tsitsikamma coast along the South African south coast is a case in point, the sediment supplied by local rivers over the past 12 ka having been trapped in a nearshore sediment wedge extending at least 5 km offshore. On the basis of high-resolution seismic surveys, the volume of the sediment wedge has been estimated at 1,354×106 m3. As 5% of this volume is considered to have been contributed by bioclastic material of marine origin, the terrestrial input would be 1,286×106 m3. This amounts to an average annual terrestrial sediment input of 0.1072×106 m3. Using a detailed sediment yield map, the modern mean annual sediment supply to the Tsitsikamma coast by local rivers has been estimated at 0.1028×106 m3. Unless coincidental, the remarkable similarity of the two values suggests that the current climatic conditions along the Tsitsikamma coast correspond to the Holocene mean. This conclusion is supported by the currently available climate data for the South African south coast.

Holocene sedimentation and coastal wetlands response to rising sea level at the Aucilla river mouth, a low energy coast in the Big Bend area of Florida

USGS Publications Warehouse

Garrett, Connie; Hertler, Heidi; Hoenstine, Ronald; Highley, Brad

1993-01-01

The shallow dip of the Florida carbonate platform results in low wave energy on Florida ???Big Bend??? coasts. Therefore sedimentation is dominated by river-and tidal-hydrodynamics near the Aucilla River mouth. Where present, Holocene sediments are thin and unconformably overlie Oligocene-aged Suwannee Limestone. The oldest unlithified sediments include reworked carbonate rubble with clay and wood fragments (seven thousand years old or less, based on wood radio-carbon dating). Although this basal sequence is observed in most areas, the sediments that overlie it vary. Sediment sequences from the outer littoral to submarine environments include organic-rich sands, oyster biotherm remains, and cleaner sands with organic-filled burrows. Inner littoral (salt-marsh) sequences generally consist of sandy, fining-upwards sequences in which dry weights of fine-grained clastics and organic components increase up-sequence at similar rates. Offshore sediments preserve greatly attenuated fluvial and salt-marsh facies, if these facies are preserved at all. With sea-level rise, erosion can result from insufficient sediment supply and down-cutting by tidal currents (Dolotov, 1992; and Dalrymple et al., 1992). Dolotov (1992) attributes displacement of original coastal stratigraphy to insufficient sediments for beach profile maintenance, while Dalrymple et al. (1992) attribute erosional truncation (ravinement) or complete removal of portions of typical estuarine sequences to headward migration of tidal channels.

Seabed ripple morphology and surficial sediment size at the SAX04 experiments near Fort Walton Beach, Florida, fall 2004

USGS Publications Warehouse

Hanes, Daniel M.; Erikson, Li H.; Lescinski, Jamie M.R.; Harney, Jodi N.; Carter, Carissa L.; Hatcher, Gerry A.; Lacy, Jessica R.; Rubin, David M.

2007-01-01

Data presented in this report originates from measurements obtained off the Florida coast (fig. 1) as part of the Sediment Acoustics Experiment (SAX04) and Ripples Department Research Initiative (DRI) (Office of Naval Research (ONR), Critical Benthic Environmental Processes and Modeling, Long Range BAA 04-001, Sept. 10, 2003). The aim of this document is to present methods employed to extract data and the resulting measured ripple characteristics (ripple height, wavelength, and orientation) and seabed grain sizes. Application and analysis of the data with respect to hydro- and morphodynamics will be addressed in subsequent reports. Sediment transport in the coastal region is a complex process involving interactions between flow dynamics, sediments, and bedforms. Sediment type and bed geometry directly influence entrainment of sediments into suspension, and at sites where ripples occur (sand formations on the order of several cm high and less than two meter long wavelengths), the understanding of ripple dynamics is an essential component in improving sediment transport models. To gain a better understanding and ability to predict sediment transport, a field study was undertaken to investigate morphology, orientation, and dynamics of ripples on the seafloor. The data obtained from the field campaign also supports an on-going effort to study the effects of ripples on low grazing acoustic penetration into sandy marine sediments for the detection of objects, such as mines (Jackson and others, 2002).

Burial Duration and Frequency Influences Resilience of Differing Propagule Types in a Subtidal Seagrass, Posidonia australis

PubMed Central

2016-01-01

Sedimentation that leads to periodic, and often prolonged, burial events is becoming more common on the world’s coastlines as human populations expand and create urbanised marine environments. Different seagrass species react differently to sediment burial but many species in the southern hemisphere are yet to be examined. How seagrasses react to burial has restoration implications. There is a need to critically assess seagrass transplant propagule responses to periodic (pulse) and prolonged (press) burial events before selecting the most appropriate species, transplant propagule, and transplant site. In my study, mesocosm experiments, coupled with field measurements were used to assess how sexual (seedlings) and vegetative (sprigs) propagules of Posidonia australis responded to pulse and press burial events. Seedlings were highly susceptible to burial (both pulse and press), with no survival at the end of the experimental period. In contrast, rhizome growth in vegetative propagules was stimulated by pulse burial, although press burial events resulted in mortality. The implication for Posidonia australis restoration efforts in areas where burial is periodic, was that vegetative propagules are optimal transplant units, in comparison to seedlings. Press burial however, renders a transplant site sub-optimal for both seedling and sprig transplants. PMID:27526020

Secular change in chert distribution: a reflection of evolving biological participation in the silica cycle

NASA Technical Reports Server (NTRS)

Maliva, R. G.; Knoll, A. H.; Siever, R.

1989-01-01

In the modern oceans, the removal of dissolved silica from sea water is principally a biological process carried out by diatoms, with lesser contributions from radiolaria, silicoflagellates, and sponges. Because such silica in sediments is often redistributed locally during diagenesis to from nodular or bedded chert, stratigraphic changes in the facies distribution of early diagenetic chert provide important insights into the development of biological participation in the silica cycle. The abundance of chert in upper Proterozoic peritidal carbonates suggests that at this time silica was removed from seawater principally by abiological processes operating in part of the margins of the oceans. With the evolution of demosponges near the beginning of the Cambrian Period, subtidal biogenetic cherts became increasingly common, and with the Ordovician rise of radiolaria to ecological and biogeochemical prominence, sedimented skeletons became a principal sink for oceanic silica. Cherts of Silurian to Cretaceous age share many features of facies distribution and petrography but they differ from Cenozoic siliceous deposits. These differences are interpreted to reflect the mid-Cretaceous radiation of diatoms and their subsequent rise to domination of the silica cycle. Biogeochemical cycles provide an important framework for the paleobiological interpretation of the organisms that participate in them.

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

NASA Astrophysics Data System (ADS)

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

2012-04-01

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

Nearshore sediment thickness, Fire Island, New York

USGS Publications Warehouse

Locker, Stanley D.; Miselis, Jennifer L.; Buster, Noreen A.; Hapke, Cheryl J.; Wadman, Heidi M.; McNinch, Jesse E.; Forde, Arnell S.; Stalk, Chelsea A.

2017-04-03

Investigations of coastal change at Fire Island, New York (N.Y.), sought to characterize sediment budgets and determine geologic framework controls on coastal processes. Nearshore sediment thickness is critical for assessing coastal system sediment availability, but it is largely unquantified due to the difficulty of conducting geological or geophysical surveys across the nearshore. This study used an amphibious vessel to acquire chirp subbottom profiles. These profiles were used to characterize nearshore geology and provide an assessment of nearshore sediment volume. Two resulting sediment-thickness maps are provided: total Holocene sediment thickness and the thickness of the active shoreface. The Holocene sediment section represents deposition above the maximum flooding surface that is related to the most recent marine transgression. The active shoreface section is the uppermost Holocene sediment, which is interpreted to represent the portion of the shoreface thought to contribute to present and future coastal behavior. The sediment distribution patterns correspond to previously defined zones of erosion, accretion, and stability along the island, demonstrating the importance of sediment availability in the coastal response to storms and seasonal variability. The eastern zone has a thin nearshore sediment thickness, except for an ebb-tidal deposit at the wilderness breach caused by Hurricane Sandy. Thicker sediment is found along a central zone that includes shoreface-attached sand ridges, which is consistent with a stable or accretional coastline in this area. The thickest overall Holocene section is found in the western zone of the study, where a thicker lower section of Holocene sediment appears related to the westward migration of Fire Island Inlet over several hundred years.

The influence of wave energy and sediment transport on seagrass distribution

USGS Publications Warehouse

Stevens, Andrew W.; Lacy, Jessica R.

2012-01-01

A coupled hydrodynamic and sediment transport model (Delft3D) was used to simulate the water levels, waves, and currents associated with a seagrass (Zostera marina) landscape along a 4-km stretch of coast in Puget Sound, WA, USA. A hydroacoustic survey of seagrass percent cover and nearshore bathymetry was conducted, and sediment grain size was sampled at 53 locations. Wave energy is a primary factor controlling seagrass distribution at the site, accounting for 73% of the variability in seagrass minimum depth and 86% of the variability in percent cover along the shallow, sandy portions of the coast. A combination of numerical simulations and a conceptual model of the effect of sea-level rise on the cross-shore distribution of seagrass indicates that the area of seagrass habitat may initially increase and that wave dynamics are an important factor to consider in predicting the effect of sea-level rise on seagrass distributions in wave-exposed areas.

Mechanisms controlling the complete accretionary beach state sequence

NASA Astrophysics Data System (ADS)

Dubarbier, Benjamin; Castelle, Bruno; Ruessink, Gerben; Marieu, Vincent

2017-06-01

Accretionary downstate beach sequence is a key element of observed nearshore morphological variability along sandy coasts. We present and analyze the first numerical simulation of such a sequence using a process-based morphodynamic model that solves the coupling between waves, depth-integrated currents, and sediment transport. The simulation evolves from an alongshore uniform barred beach (storm profile) to an almost featureless shore-welded terrace (summer profile) through the highly alongshore variable detached crescentic bar and transverse bar/rip system states. A global analysis of the full sequence allows determining the varying contributions of the different hydro-sedimentary processes. Sediment transport driven by orbital velocity skewness is critical to the overall onshore sandbar migration, while gravitational downslope sediment transport acts as a damping term inhibiting further channel growth enforced by rip flow circulation. Accurate morphological diffusivity and inclusion of orbital velocity skewness opens new perspectives in terms of morphodynamic modeling of real beaches.

Comparison of Physical Properties of Marine and Arctic Gas-Hydrate-Bearing Deposits

NASA Astrophysics Data System (ADS)

Winters, W. J.; Walker, M.; Collett, T. S.; Bryant, S. L.; Novosel, I.; Wilcox-Cline, R.; Bing, J.; Gomes, M. L.

2009-12-01

Gas hydrate (GH) occurs in both marine settings and in arctic environments within a wide variety of sediment types. Grain-size analyses from both environments indicate that intrinsic host-sediment properties have a strong influence on gas-hydrate distribution and morphologic characteristics. Depending on the amount formed or dissociated, gas hydrate can significantly change in situ sediment acoustic, mechanical, and hydraulic properties. The U.S. Geological Survey, in cooperation with the U.S. Dept. of Energy, BP Expl.-Alaska, Nat. GH Prog. of India, Canadian Geological Survey, Int. Ocean Drilling Program, Japan Oil Gas and Metals Nat. Corp., Japan Pet. Expl. Co., Int. Marine Past Global Changes Study (IMAGES) program, and Paleoceanography of the Atlantic and Geochemistry (PAGE) program, determined physical properties from marine and arctic sediments and their relation to the presence of GH. At two arctic sites, the Mount Elbert well on the Alaskan North Slope and the Mallik wells on the Mackenzie Delta, NWT, >10-m thick gas-hydrate-bearing (GHB) sandy deposits are capped by finer-grained sediments that may reduce gas migration. In the Mount Elbert well, average median grain sizes (MGS) for the two thickest GHB deposits are 65 and 60 µm. Finer-grained (average MGS of 9 and 28 µm) sediments have plug permeabilities that are 300 and 14 times smaller than underlying GHB sediment. Average MGS of GHB sediment from the Mallik 2L well is ~ 111 µm, compared to overlying sediment with an average MGS of ~ 32 µm. Gas hydrate morphology in the Gulf of Mexico (GOM) and offshore India is substantially more complex than in the arctic, and is related to pervasive, although not exclusive, finer-grained deposits. Massive, several-cm thick, GH layers were recovered in piston cores in the northern GOM, in sediment with little visible lithologic variability (average MGS ~ 0.8 µm). In wells off the east coast of India, GH was present in sand-rich, fractured clay, and reservoirs with both characteristics. Maximum MGS measured on more than 1200 samples was 46 µm, but the average MGS for 14 wells varied from 5 to 10 µm. At Site 10, in the Krishna-Godavari Basin, GH was observed in several morphologic configurations, including complex high-angle planar and rotational veins, solid nodules, and disseminated, in sediment with average MGS of 5 µm, liquid limits between 70 and 98, and plastic limits between 33 and 49. Sediment in a 692-m deep well drilled off the Andaman Islands sporadically hosted disseminated GH in thin coarser-grained ash beds and ash-rich zones. Average and maximum MGS in this well is 6 and 17 µm, respectively. To date, sandy GH reservoirs (with some exceptions, e.g., Nankai Trough) are typically associated with the arctic. However, the presence of thick offshore sand-rich GHB reservoirs is the subject of current investigations, such as by the Gulf of Mexico Joint Industry Project (JIP).

Transport of microspheres and indigenous bacteria through a sandy aquifer: Results of natural- and forced-gradient tracer experiments

USGS Publications Warehouse

Harvey, R.W.; George, L.H.; Smith, R.L.; LeBlanc, D.R.

1989-01-01

Transport of indigenous bacteria through sandy aquifer sediments was investigated in forced- and natural-gradient tracer teste. A diverse population of bacteria was collected and concentrated from groundwater at the site, stained with a DNA-specific fluorochrome, and injected back into the aquifer. Included with the injectate were a conservative tracer (Br- or Cl-) and bacteria-sized (0.2-1.3-??m) microspheres having carboxylated, carbonyl, or neutral surfaces. Transport of stained bacteria and all types and size classes of microspheres was evident. In the natural-gradient test, both surface characteristics and size of microspheres affected attenuation. Surface characteristics had the greatest effect upon retardation. Peak break-through of DAPI-stained bacteria (forced-gradient experiment) occurred well in advance of bromide at the more distal sampler. Transport behavior of bacteria was substantially different from that of carboxylated microspheres of comparable size. ?? 1988 American Chemical Society.

Mercury methylation in sediments of a Brazilian mangrove under different vegetation covers and salinities.

PubMed

de Oliveira, Diana Ciannella Martins; Correia, Raquel Rose Silva; Marinho, Claudio Cardoso; Guimarães, Jean Remy Davée

2015-05-01

The presence and formation of methylmercury (MMHg), a highly toxic form of Hg, in mangrove ecosystems is poorly studied. Therefore the aim of this study was to evaluate mercury methylation potentials in sediment, litter and root samples (Avicennia shaueriana and Spartina alterniflora) from different regions of a mangrove ecosystem, as well as the influence of salinity on methylation. Sediment was sampled under different depths and in mangrove regions with different plant covers and salinities. All samples were incubated with (203)Hg and MM(203)Hg was extracted and measured by liquid scintillation. MMHg was formed in all samples and sites tested including plant roots and litter. Higher Hg methylation was found in the superficial fraction of sediments (0.47-7.82%). Infralittoral sandy sediment had low MMHg formation (0.44-1.61%). Sediment under Rhizophora mangle had lower MMHg formation (0.018-2.23%) than under A. shaueriana (0.2-4.63%) and Laguncularia racemosa (0.08-7.82). MMHg formation in sediment tended to increase with salinity but the differences were not significant. Therefore, MMHg formation occurs in different sites of mangrove ecosystems and may be an important threat that requires further study. Copyright © 2015 Elsevier Ltd. All rights reserved.

Sedimentary architecture of a sub-lacustrine debris fan: Eocene Dongying Depression, Bohai Bay Basin, east China

NASA Astrophysics Data System (ADS)

Liu, Jianping; Xian, Benzhong; Wang, Junhui; Ji, Youliang; Lu, Zhiyong; Liu, Saijun

2017-12-01

The sedimentary architectures of submarine/sublacustrine fans are controlled by sedimentary processes, geomorphology and sediment composition in sediment gravity flows. To advance understanding of sedimentary architecture of debris fans formed predominantly by debris flows in deep-water environments, a sub-lacustrine fan (Y11 fan) within a lacustrine succession has been identified and studied through the integration of core data, well logging data and 3D seismic data in the Eocene Dongying Depression, Bohai Bay Basin, east China. Six types of resedimented lithofacies can be recognized, which are further grouped into five broad lithofacies associations. Quantification of gravity flow processes on the Y11 fan is suggested by quantitative lithofacies analysis, which demonstrates that the fan is dominated by debris flows, while turbidity currents and sandy slumps are less important. The distribution, geometry and sedimentary architecture are documented using well data and 3D seismic data. A well-developed depositional lobe with a high aspect ratio is identified based on a sandstone isopach map. Canyons and/or channels are absent, which is probably due to the unsteady sediment supply from delta-front collapse. Distributary tongue-shaped debris flow deposits can be observed at different stages of fan growth, suggesting a lobe constructed by debrite tongue complexes. Within each stage of the tongue complexes, architectural elements are interpreted by wireline log motifs showing amalgamated debrite tongues, which constitute the primary fan elements. Based on lateral lithofacies distribution and vertical sequence analysis, it is proposed that lakefloor erosion, entrainment and dilution in the flow direction lead to an organized distribution of sandy debrites, muddy debrites and turbidites on individual debrite tongues. Plastic rheology of debris flows combined with fault-related topography are considered the major factors that control sediment distribution and fan architecture. An important implication of this study is that a deep-water depositional model for debrite-dominated systems was proposed, which may be applicable to other similar deep-water environments.

Regressive and transgressive barrier islands on the North-Central Gulf Coast — Contrasts in evolution, sediment delivery, and island vulnerability

NASA Astrophysics Data System (ADS)

Otvos, Ervin G.; Carter, Gregory A.

2013-09-01

Basic differences between non-deltaic regressive and deltaic transgressive barrier islands reflect major contrasts in geological settings and sediment sources. Two island groups on the N. Gulf of Mexico provide unique perspectives of genetic and geomorphic contrasts applicable in a worldwide context. The near-extinction of the deltaic transgressive Chandeleur barriers and reduction of the sturdier prograded Mississippi-Alabama (MS-AL) chain are related to differences in sediment sources, storm, and anthropogenic impact. 160 years of documentary evidence points to contrasting geological settings, development history, sediment sources, and island morphology as responsible for different island erodibility and life spans. The non-deltaic chain received larger volumes of coarser, less erodible medium sand from the NE Gulf coast. Onshore sand flux from reworked delta deposits received from the retreating delta shoreface initiated the fragile, thin, and isolated transgressive Chandeleur islands. Fine-grained sand from unconsolidated muds of abandoned Mississippi-St. Bernard delta lobes maintained two distinct transgressive barrier island categories. In the absence of quantitative data on cross-shore transport, discrepancies between estimated littoral drift volumes and sand reserves for nourishment remain unexplained. Medium-sandy MS-AL barriers have resisted storm events far better than delta barriers. However, even the former chain did undergo 26 to 53% area reduction since 1848. Anthropogenic intervention stymied island growth. Emerging intertidal berm-basins formed on sandy shoal platforms in storm-eliminated sectors have contributed to partial island recovery. Delta attrition by wave erosion, tectonic, and compactional subsidence had accelerated delta lobe and barrier island decay. Intensive storm erosion culminating in and following Hurricane Katrina came close to eradicate the highly vulnerable Chandeleur barrier chain. Lacking adequate nourishment, after devastating cyclones only small islands reemerge and persist temporarily from the shoal belt. A four-stage barrier evolution model, globally applicable to transgressive deltaic barriers, is based on documented changes in late Holocene Mississippi sub-deltas.

Sedimentary organic matter distributions, burrowing activity, and biogeochemical cycling: Natural patterns and experimental artifacts

NASA Astrophysics Data System (ADS)

Michaud, Emma; Aller, Robert, C.; Stora, Georges

2010-11-01

The coupling between biogenic reworking activity and reactive organic matter patterns within deposits is poorly understood and often ignored. In this study, we examined how common experimental treatments of sediment affect the burrowing behavior of the polychaete Nephtys incisa and how these effects may interact with reactive organic matter distributions to alter diagenetic transport - reaction balances. Sediment and animals were recovered from a subtidal site in central Long Island Sound, USA. The upper 15 cm of the sediment was sectioned into sub-intervals, and each interval separately sieved and homogenized. Three initial distributions of sediment and organic substrate reactivity were setup in a series of microcosms: (1) a reconstituted natural pattern with surface-derived sediment overlying sediment obtained from progressively deeper material to a depth of 15 cm (Natural); (2) a 15 cm thick sediment layer composed only of surface-derived sediment (Rich); and (3) a 15 cm thick layer composed of uniformally mixed sediment from the original 15 cm sediment profile (Averaged). The two last treatments are comparable to that used in microcosms in many previous studies of bioturbation and interspecific functional interaction experiments. Sediment grain size distributions were 97.5% silt-clay and showed no depth dependent patterns. Sediment porosity gradients were slightly altered by the treatments. Nepthys were reintroduced and aquariums were X-rayed regularly over 5 months to visualize and quantify spatial and temporal dynamics of burrows. The burrowing behaviour of adult populations having similar total biovolume, biomass, abundance, and individual sizes differed substantially as a function of treatment. Burrows in sediment with natural property gradients were much shallower and less dense than those in microcosms with altered gradients. The burrow volume/biovolume ratio was also lower in the substrate with natural organic reactivity gradients. Variation in food resources or in sediment mechanical properties associated with treatments, the latter in part coupled to remineralization processes such as exopolymer production, may explain the burrowing responses. In addition to demonstrating how species may respond to physical sedimentation events (substrate homogenization) and patterns of reactive organic matter redistribution, these experiments suggest that infaunal species interactions in microcosms, including the absolute and relative fluxes of remineralized solutes, may be subject to artifacts depending on exactly how sediments are introduced experimentally. Nonlocal transport and cylinder microenvironment transport - reaction models readily demonstrate how the multiple interactions between burrowing patterns and remineralization rate distributions can alter relative flux balances, decomposition pathways, and time to steady state.

Flashy Water and Sediment Delivery to Fluvial Megafan andFan Delta Systems on Opposing Shorelines of an Early Eocene Lake

NASA Astrophysics Data System (ADS)

Jones, E. R.; Plink-Bjorklund, P.

2015-12-01

Flashy delivery of water and sediment had distinct effects on the process of deposition in coeval fluvial megafan and fan delta deposits on opposing shorelines of a paleolake that occupied the Uinta Basin throughout the Eocene. The Tertiary Uinta Basin was an asymmetric continental interior basin with a steep northern margin, adjacent to the block uplift controlling basin subsidence, and a low gradient southern margin. A ~140 km wide fluvial megafan with catchments as far as ~750 km away occupied the southern margin of the lacustrine basin. Within this megafan system, fluvial deposits contain within-channel continental bioturbation and paleosol development on bar accretion surfaces that are evidence of prolonged periods of groundwater flow or channel abandonment. These are punctuated by channel fills exhibiting a suite of both high-deposition rate and upper flow regime sedimentary structures that were deposited by very rapid suspension-fallout during seasonal to episodic river flooding events. A series of small (~8 km wide) and proximally sourced fan deltas fed sediment into the steeper northern margin of the lacustrine basin. 35-50% of the deposits in the delta plain environment of these fan deltas are very sandy debris flows with as low as 5% clay and silt sized material. Detrital zircon geochronology shows that these fan deltas were tapping catchments where mostly unconsolidated Cretaceous sedimentary cover and thick Jurassic eolianites were being eroded. A combination of flashy precipitation, arid climate, catchments mantled by abundant loose sand-sized colluvium, and steep depositional gradients promoted generation of abundant very sandy (5-10% clay and silt sized material) debris flows. In this way, the Wasatch and Green River Formations in the Uinta Basin, Utah, U.S.A. gives us two very different examples of how routing flashy water and sediment delivery (associated with pulses of hyperthermal climate change during the Early Eocene) through different depositional systems produced unique processes of deposition, and also gives us an opportunity to isolate the effects of other variables (e.g. sediment caliber, system gradient, catchment size) that can modulate the flashy precipitation signal in stratigraphy.

The Link between Microbial Diversity and Nitrogen Cycling in Marine Sediments Is Modulated by Macrofaunal Bioturbation.

PubMed

Yazdani Foshtomi, Maryam; Braeckman, Ulrike; Derycke, Sofie; Sapp, Melanie; Van Gansbeke, Dirk; Sabbe, Koen; Willems, Anne; Vincx, Magda; Vanaverbeke, Jan

2015-01-01

The marine benthic nitrogen cycle is affected by both the presence and activity of macrofauna and the diversity of N-cycling microbes. However, integrated research simultaneously investigating macrofauna, microbes and N-cycling is lacking. We investigated spatio-temporal patterns in microbial community composition and diversity, macrofaunal abundance and their sediment reworking activity, and N-cycling in seven subtidal stations in the Southern North Sea. Our results indicated that bacteria (total and β-AOB) showed more spatio-temporal variation than archaea (total and AOA) as sedimentation of organic matter and the subsequent changes in the environment had a stronger impact on their community composition and diversity indices in our study area. However, spatio-temporal patterns of total bacterial and β-AOB communities were different and related to the availability of ammonium for the autotrophic β-AOB. Highest bacterial richness and diversity were observed in June at the timing of the phytoplankton bloom deposition, while richness of β-AOB as well as AOA peaked in September. Total archaeal community showed no temporal variation in diversity indices. Distance based linear models revealed that, independent from the effect of grain size and the quality and quantity of sediment organic matter, nitrification and N-mineralization were affected by respectively the diversity of metabolically active β-AOB and AOA, and the total bacteria, near the sediment-water interface. Separate models demonstrated a significant and independent effect of macrofaunal activities on community composition and richness of total bacteria, and diversity indices of metabolically active AOA. Diversity of β-AOB was significantly affected by macrofaunal abundance. Our results support the link between microbial biodiversity and ecosystem functioning in marine sediments, and provided broad correlative support for the hypothesis that this relationship is modulated by macrofaunal activity. We hypothesized that the latter effect can be explained by their bioturbating and bio-irrigating activities, increasing the spatial complexity of the biogeochemical environment.

Residual circulation and suspended sediment transport in the Dutch Wadden Sea

NASA Astrophysics Data System (ADS)

Duran-Matute, Matias; Sassi, Maximiliano; de Boer, Gerben; Grawë, Ulf; Gerkema, Theo; van Kessel, Thijs; Cronin, Katherine

2014-05-01

The Dutch Wadden Sea (DWS), situated between continental Europe and the Dutch Wadden Islands, is a semi enclosed basin connected to the North Sea by a series of tidal inlets and composed mainly of tidal flats and sea gullies. The DWS is of high ecological importance due to its biodiversity and has been declared a World Heritage site by UNESCO. It is a dynamic area subject to regional relative sea level rise due to global sea level rise, postglacial rebound and gas exploitation. For intertidal areas to continue to serve as feeding ground for migratory birds, a net import of sediment is required. Observations are crucial but provide only scarce information in space and time. Hence, to estimate the net influx of suspended sediment into the DWS, realistic high resolution three-dimensional numerical simulations have been carried out using the General Estuarine Transport Model (GETM). The hydrodynamics are mainly governed by the tides, the fresh water discharge from several sluices into the DWS and wind variability. It is expected that the transport of suspended particulate matter (SPM) is governed by the same factors, too, in combination with sediment sink and source terms. For validation, the results are compared against different observational data sets, such as tidal gauges, temperature and salinity at a fixed station, and the volumetric flux rate through one of the inlets obtained from an acoustic Doppler current profiler (ADCP) attached to a ferry. SPM transport is modeled for four different sediment classes each of which is defined by the critical shear stress and the settling velocity. Results show a clear net import of SPM through one of the inlets, which is in agreement with the observations. First estimates of the total sediment fluxes through the different inlets are presented together with an analysis on their variability and sensibility to the external forcing. Of particular importance is the net export of SPM during storms as well as the role of storms on sub-tidal variability.

Anthropogenic influences on shoreline and nearshore evolution in the San Francisco Bay coastal system

USGS Publications Warehouse

Dallas, K.L.; Barnard, P.L.

2011-01-01

Analysis of four historical bathymetric surveys over a 132-year period has revealed significant changes to the morphology of the San Francisco Bar, an ebb-tidal delta at the mouth of San Francisco Bay estuary. From 1873 to 2005 the San Francisco Bar vertically-eroded an average of 80 cm over a 125 km2 area, which equates to a total volume loss of 100 ± 52 million m3 of fine- to coarse-grained sand. Comparison of the surveys indicates the entire ebb-tidal delta contracted radially, with the crest moving landward an average of 1 km. Long-term erosion of the ebb-tidal delta is hypothesized to be due to a reduction in the tidal prism of San Francisco Bay and a decrease in coastal sediment supply, both as a result of anthropogenic activities. Prior research indicates that the tidal prism of the estuary was reduced by 9% from filling, diking, and sedimentation. Compilation of historical records dating back to 1900 reveals that a minimum of 200 million m3 of sediment has been permanently removed from the San Francisco Bay coastal system through dredging, aggregate mining, and borrow pit mining. Of this total, ~54 million m3 of sand-sized or coarser sediment was removed from central San Francisco Bay. With grain sizes comparable to the ebb-tidal delta, and its direct connection to the bay mouth, removal of sediments from central San Francisco Bay may limit the sand supply to the delta and open coast beaches. SWAN wave modeling illustrates that changes to the morphology of the San Francisco Bar have altered the alongshore wave energy distribution at adjacent Ocean Beach, and thus may be a significant factor in a persistent beach erosion ‘hot spot’ occurring in the area. Shoreline change analyses show that the sandy shoreline in the shadow of the ebb-tidal delta experienced long-term (1850s/1890s to 2002) and short-term (1960s/1980s to 2002) accretion while the adjacent sandy shoreline exposed to open-ocean waves experienced long-term and short-term erosion. Therefore, the recently observed accelerating rates of bay sediment removal, ebb-tidal delta erosion, and open coast beach erosion are all correlated temporally.

Removing Wave Artifacts from Eddy Correlation Data

NASA Astrophysics Data System (ADS)

Neumann, Andreas; Brand, Andreas

2017-04-01

The German Wadden Sea is an extensive system of back-barrier tidal basins along the margin of the southern North Sea. Due to their high productivity and the strong retention potential of labile organic carbon high mineralization rates are expected in this system. Since the sediment bed is sandy, the oxygen fluxes across the sediment-water interface (SWI) may be enhanced by strong tidal currents as well as by wind-induced surface waves. In order to measure oxygen fluxes in-situ without disturbance of the sediment, the Eddy Correlation method (ECM) was introduced to aquatic geoscience by Berg et al. (2003). The method is based on correlating turbulent fluctuations of oxygen concentration and vertical velocity measured at high frequency above the SWI. The method integrates over spatial heterogeneities and allows the observation of total benthic oxygen fluxes in complex systems where other methods like flux chamber deployments and oxygen profile measurements in the sediment fail. Therefore, the method should also reflect effects like the enhancement of oxygen fluxes by porewater advection driven by waves and currents over sandy sediments. Unfortunately the ECM suffers from wave contamination due to stirring sensitivity of the electrodes, spatial separation between the oxygen electrode and the location of velocity measurement as well as by a tilt of the measurement setup at the deployment side. In order to correct for this wave contamination we tested the method of spectral reconstruction initially introduced by Bricker and Monismith (2007) for the determination of Reynolds-stresses in wave-affected environments. In short, this method attempts to remove the wave signal from the Power spectral densities of oxygen concentration and vertical velocity fluctuations by cutting off the wave peak in these spectra. The wave contribution to the co-spectrum between both quantities is then reconstructed by assuming that the phasing in the wave band is dominated by the waves. Based on the example of the North-Frisian Wadden Sea we will discuss the potentials and limits of this method. References: Berg, P., H. Roy, F. Janssen, V. Meyer, B. Jorgensen, M. Huettel, and D. de Beer (2003), Oxygen uptake by aquatic sediments measured with a novel non-invasive eddy-correlation technique, Marine Ecology-Progress Series, 261, 75-83, doi:10.3354/meps261075. Bricker, J. D., and S. G. Monismith (2007), Spectral wave turbulence decomposition, J. Atmos. Oceanic Technol., 24(8), 1479-1487, doi:10.1175/JTECH2066.1.

Environment and Climate Changes during the Holocene: Inferred from Sedimentary Record/Proxies of a Paleodelta Region, Southwest Coast of India

NASA Astrophysics Data System (ADS)

Allu, N. C.; Prakash, V.; Gautam, P. K.; Bera, S. K.

2014-12-01

This work explains the sedimentation history and environment and climate changes during the Holocene along the southwest coast of India. The area is characterized by various landforms such as lagoons, barrier islands, beach ridges, paleostrandlines, alluvial plains, marshy lands and flood plains. Paleodelta, located at the mouth of the modern Periyar River is an important geomorphic marker. A borehole of 40 m depth was drilled in the paleodelta and sediment samples were recovered at different depth intervals. Paleoclimate and paleo-environment were inferred based on geochronology, textural and geotechnical parameters, clay minerals, and pollen analysis results. The bottom of the borehole represents an age of ~ 12 ka BP. Sediments exhibit coarsening texture upwards of the borehole, with fine mud and peat intercalations at the bottom. Six litho facies - muddy sand, sand, sandy mud, silty sand, sandy silt, and mud - were recorded. Geotechnical properties comprising moisture content, organic carbon, plasticity index record high values, whereas low bulk density associated with a low critical shear stress, are recorded. An increase in illite and to a lesser degree smectite with concomitant decrease in kaolinite is observed. Sediment texture represents a major change of depositional environment from marine to fluvial sedimentary facies during the major sea level fall i.e., after 7 ka B.P. The present sea level attained during 4-5 ka B.P; major rise of sea level has taken place from 7-11 ka BP and regression during 7 - 5 ka B.P. These transgression and regression phases introduced the changes in the environment of deposition. The monsoon was dynamic and more intense after the major fall of sea level causing the fluctuations in the fluvial facies. Upward coarsening of grain size in the borehole indicates change in sediment deposition due to increased hydrodynamic conditions and strong fluvial action, which can be linked to marine regression. Geotechnical properties suggest textural changes and sedimentary facies. An upward increase in smectite and kaolinite and decreasing illite supports major fall in sea level and also the aridity. Pollen record of sediment strata supports the paleo-environment dominated by the presence of semi-evergreen type of mangrove plants during mid- to early-Holocene times.

Comparison of the evolution of the sediment dynamics of a bay and an estuary in the East coast of the English Channel: the case of the Bay of Somme and the Seine estuary (France)

NASA Astrophysics Data System (ADS)

Cuvilliez, A.; Le Bot, S.; Michel, C.; Cuvilliez, C.

2017-12-01

The economical roles and the ecological importance of the intertidal zones of mouth the Seine estuary (25 Km²) and of the Bay of Somme (70 Km²), both located on the East coast of the English Channel (Fig. 1A and Fig. 1B), have led to numerous studies on sediment dynamics since the beginning of the 19th century. Since 1995, the high resolution remote sensing (8 cm per side of pixel) allowed an exhaustive study of these intertidal surfaces. Altimetric surveys using radials, notably with ALTUS altimeters, then with LiDAR, were carried out in order to estimate more accurately the volumes and the nature of the sediments that infill these areas. The study of sedimentary facies further improved our understanding of the roles of the environmental forcing which controls sedimentation dynamics. Indeed, it allows foreseeing hydraulic circulation issues which damage these coastal ecosystems, and which can thus be prevented. Subsequently, for more than a decade, these two macrotidal zones, which have a tidal range equal to or greater than 8.5 m, show a decrease in their settling surface size which fosters mud deposition, and an acceleration of their sand infilling. Since 2005, year that marks the completion of the work of the so-called "Port 2000" harbour, the Seine estuary has increased its intertidal areas by almost 45% (<+7.5 m) (Fig.1C), of which 69% are occupied by sandy or silty sediments brought by the flood tides. In the Bay of Somme, only the low-lying intertidal areas (<+ 3.5m) are infilled with sandy sediments, representing 88% of the total deposits (Fig. 1D). In this case, the study of the sedimentary facies reveals that the littoral drift and the action of the waves linked to the tide are mainly responsible of the infill. If sedimentary infilling is a widespread characteristic of estuaries and bays which started with the Holocene transgression, this phenomenon is accentuated with the sea level rise and is greatly amplified with port developments that tend to limit the action of the river flow.

Modern foraminiferal facies in a subtropical estuarine channel, Bertioga, São Paulo, Brazil

USGS Publications Warehouse

Eichler, P.P.B.; Eichler, B.B.; De Miranda, L. B.; Rodrigues, A.R.

2007-01-01

Numerical analyses of modern foraminiferal abundance and environmental data from the Bertioga Channel (Sa??o Paulo, Brazil) reveal multiple biofacies within an overall paralic setting. Despite its fisheries, mariculture and attraction to tourists, the environmental state of Bertioga Channel remains poorly studied. The present investigation is an attempt to partly fill this gap; the parameters examined include depth, salinity, temperature, organic carbon, sulfur content and bottom sediment type. Muddy sediments with high organic carbon content derived from land drainage are found in the inner parts of the channel, whereas sandy sediment dominates the areas adjacent to the Atlantic Ocean. In the eastern entrance to the channel, sandy sediment contain species of Rotaliida from Facies 1 (including Elphidium discoidale, Elphidium poeyanum, Hanzawaia boueana, Pararotalia cananeiaensis and Nonionella atlantica), reflecting normal marine salinity. Sediments with high percentages of silt and clay in polyhaline and eurybaline environments of the eastern part and Itapanhau?? River contain Facies 2, which includes Ammonia beccarii and Pararotalia cananeiaensis. In the western entrance and central, western and eastern parts, where salinities vary from 18 to 30 psu and the sediments contain both low and high organic carbon, the foraminifera from Facies 3 are dominated by Quinqueloculina milletti, Arenoparrella mexicana, Pararotalia cananeiaensis, Ammonia beccarii, Buliminella elegantissima, Elphidium sp., Elphidium excavatum, Elphidium gunteri and Elphidium poeyanum. In mesohaline and polyhaline waters of the central part, the organic-carbon-rich silt and clay contain Facies 4, which includes Ammonia beccarii, Pararotalia cananeiaensis, Elphidium excavatum and Elphidium sp. Most of organic-carbon-enriched, silty-clay substrates that are subject to the highest fresh-water discharge and high bottom temperatures support two different assemblages: one of mostly Rotaliina and the other mostly of Textulariida (Facies 5 and 6). Facies 5 includes Ammonia beecarii, Elphidium excavatum, Arenoparrella mexicana, Haplophragmoides wilberti, Siphotrochammina lobata, Trochammina inflata and Trochammina sp., all of which are typical of mesohaline sites (mainly Crumau?? and Trindade rivers), and Facies 6 includes Bolivina sp., Ammoastuta salsa, Arenoparrella mexicana, Haplophragmoides wilberti and Trochammina sp., all of which are typical of oligohaline and mesohaline mangrove fringes. The foraminiferal species from the present study are frequently found in paralic environments in Brazil, western Africa and other estuaries around the world.

Early Diagenetic Changes of Sediment Pore Properties Beneath the Seafloor and Their Contributions to Gas Hydrate Concentration in the Eastern Margin of Japan Sea

NASA Astrophysics Data System (ADS)

Uchida, T.; Horiuchi, S.; Kato, Y.; Matsumoto, R.

2014-12-01

Recently many of the chimney-shape gas hydrate concentrated beneath the seafloor have been confirmed off Shimane and off Akita as well as off Joetsu in the eastern margin of Japan Sea, which are quite different from the occurrences of pore space hydrate filling the intergranular pore system of sands recognized in Nankai Trough, Mallik and other sites. Sediment samples below the seafloor were retrieved in 2010 up to 40 m long at the Umitaka Spur, Joetsu Channel, Toyama Trough, Japan Basin, Nishi Tsugaru and Okushiri Ridge areas. Small amounts of sandy sediment have been retrieved as thin intercalations in Pleistocene and Holocene muddy layers transported approximately around 3 to 30 ka according to the tephra ages, where supplying sediments might have not been abundant due to sea level fluctuation during the Pleistocene ice age. It is important to clarify the relationship between burial depths and absolute porosities of the argillaceous sediments in relation to early diagenesis. Macroscopic observations and descriptions, measurements of porosity and permeability, SEM (scanning electron microscope) observations, and X-ray diffraction analyses have been performed. They consist of silt- to clay-grained particles, and they sometimes contain very fine- to medium-grained thin sandy layers. Average porosities of these fine-grained sediments are 50 % in all study areas, which quickly reduce from 60% to less than 50% within 10 meters and gradually decrease to the depth. However, mean pore sizes in the Nishi Tsugaru are around 1000 nm while 100 nm in the other areas, which tend to decrease with depth. It is suggested that repacking of the muddy particles gradually advances by mechanical compaction, which may crucially influence permeability. They usually contain much opal-A, quartz, feldspar, illite and smectite that do not change definitely with depth. By optical and microscopic observations, diatom tests, foraminifers and framboidal pyrites are commonly observed, and, in particular, the shapes of diatom are usually various, dominantly fragmental and infrequently preserved. It is remarked that physical diagenesis proceeds first due to mechanical compaction, whereas chemical diagenesis advances very slowly in early diagenesis. This study was performed as a part of the MH21 Research Consortium on methane hydrate in Japan.

Behaviour of subtidal sandbars in response to nourishments

NASA Astrophysics Data System (ADS)

Radermacher, M.; de Schipper, M. A.; Price, T. D.; Huisman, B. J. A.; Aarninkhof, S. G. J.; Reniers, A. J. H. M.

2018-07-01

The behaviour of subtidal sandbars can be strongly influenced by the introduction of sand nourishments in the coastal system. This study focuses on the impact of nourishments on subtidal bar behaviour at spatio-temporal scales beyond a single nourishment project. It aims to determine the long-term behaviour of subtidal sandbars along an entire coastal cell, taking into account both the unnourished and nourished regime, and covering various types of nourishments. The analysis is based on over 50 years of sandbar evolution along the Delfland coast, a 17-km long coastal cell at the Dutch North Sea coastline protected by groynes and maintained with frequent sand nourishments. Observations reveal clearly different sandbar behaviour during the unnourished (first 20 years) and nourished periods of the dataset. Introduction of the first beach nourishments (nourished sand primarily placed at the subaerial beach) was found to stimulate sandbar development along previously unbarred sections of the coast. Shoreface nourishments (nourished sand placed at the seaward face of the pre-existing subtidal sandbar) tended to migrate shoreward rapidly at a rate of 20 to 60 m/year at this coast, thereby forcing the pre-existing sandbar to weld to the dry beach. An abrupt transition of sandbar dynamics was observed following a major nourishment operation (∼ 37.5 Mm3 of nourished sand) that covered the entire coastal cell. A new, shallow sandbar formed with a degree of alongshore variability that was unprecedented at the Delfland coast over the full study period. These results imply that individual nourishments can influence the formation and migration of individual sandbars, while continued nourishments can fundamentally change long-term sandbar dynamics along an entire coastal cell.

Modelling Wind Effects on Subtidal Salinity in Apalachicola Bay, Florida

NASA Astrophysics Data System (ADS)

Huang, W.; Jones, W. K.; Wu, T. S.

2002-07-01

Salinity is an important factor for oyster and estuarine productivity in Apalachicola Bay. Observations of salinity at oyster reefs have indicated a high correlation between subtidal salinity variations and the surface winds along the bay axis in an approximately east-west direction. In this paper, we applied a calibrated hydrodynamic model to examine the surface wind effects on the volume fluxes in the tidal inlets and the subtidal salinity variations in the bay. Model simulations show that, due to the large size of inlets located at the east and west ends of this long estuary, surface winds have significant effects on the volume fluxes in the estuary inlets for the water exchanges between the estuary and ocean. In general, eastward winds cause the inflow from the inlets at the western end and the outflow from inlets at the eastern end of the bay. Winds at 15 mph speed in the east-west direction can induce a 2000 m3 s-1 inflow of saline seawater into the bay from the inlets, a rate which is about 2·6 times that of the annual average freshwater inflow from the river. Due to the varied wind-induced volume fluxes in the inlets and the circulation in the bay, the time series of subtidal salinity at oyster reefs considerably increases during strong east-west wind conditions in comparison to salinity during windless conditions. In order to have a better understanding of the characteristics of the wind-induced subtidal circulation and salinity variations, the researchers also connected model simulations under constant east-west wind conditions. Results show that the volume fluxes are linearly proportional to the east-west wind stresses. Spatial distributions of daily average salinity and currents clearly show the significant effects of winds on the bay.

Up, Down, and All Around: Scale-Dependent Spatial Variation in Rocky-Shore Communities of Fildes Peninsula, King George Island, Antarctica

PubMed Central

Valdivia, Nelson; Díaz, María J.; Holtheuer, Jorge; Garrido, Ignacio; Huovinen, Pirjo; Gómez, Iván

2014-01-01

Understanding the variation of biodiversity along environmental gradients and multiple spatial scales is relevant for theoretical and management purposes. Hereby, we analysed the spatial variability in diversity and structure of intertidal and subtidal macrobenthic Antarctic communities along vertical environmental stress gradients and across multiple horizontal spatial scales. Since biotic interactions and local topographic features are likely major factors for coastal assemblages, we tested the hypothesis that fine-scale processes influence the effects of the vertical environmental stress gradients on the macrobenthic diversity and structure. We used nested sampling designs in the intertidal and subtidal habitats, including horizontal spatial scales ranging from few centimetres to 1000s of metres along the rocky shore of Fildes Peninsula, King George Island. In both intertidal and subtidal habitats, univariate and multivariate analyses showed a marked vertical zonation in taxon richness and community structure. These patterns depended on the horizontal spatial scale of observation, as all analyses showed a significant interaction between height (or depth) and the finer spatial scale analysed. Variance and pseudo-variance components supported our prediction for taxon richness, community structure, and the abundance of dominant species such as the filamentous green alga Urospora penicilliformis (intertidal), the herbivore Nacella concinna (intertidal), the large kelp-like Himantothallus grandifolius (subtidal), and the red crustose red alga Lithothamnion spp. (subtidal). We suggest that in coastal ecosystems strongly governed by physical factors, fine-scale processes (e.g. biotic interactions and refugia availability) are still relevant for the structuring and maintenance of the local communities. The spatial patterns found in this study serve as a necessary benchmark to understand the dynamics and adaptation of natural assemblages in response to observed and predicted environmental changes in Antarctica. PMID:24956114

Palaeoecological implications of the preservation potential of soft-bodied organisms in sediment-density flows: testing turbulent waters

NASA Astrophysics Data System (ADS)

Bath Enright, Orla G.; Minter, Nicholas J.; Sumner, Esther J.

2017-06-01

Interpreting how far organisms within fossil assemblages may have been transported and if they all originated from the same location is fundamental to understanding whether they represent true palaeocommunities. In a three-factorial experimental design, we used an annular flume to generate actualistic sandy sediment-density flows that were fast (2 ms-1) and fully turbulent in order to test the effects of flow duration, sediment concentration, and grain angularity on the states of bodily damage experienced by the freshly euthanized polychaete Alitta virens. Results identified statistically significant effects of flow duration and grain angularity. Increasing sediment concentration had a statistically significant effect with angular sediment but not with rounded sediment. Our experiments demonstrate that if soft-bodied organisms such as polychaetes were alive and then killed by a flow then they would have been capable of enduring prolonged transport in fast and turbulent flows with little damage. Dependent upon sediment concentration and grain angularity, specimens were capable of remaining intact over flow durations of between 5 and 180 min, equating to transport distances up to 21.6 km. This result has significant palaeoecological implications for fossil lagerstätten preserved in deposits of sediment-density flows because the organisms present may have been transported over substantial distances and therefore may not represent true palaeocommunities.

Coastline evolution of Portuguese low-lying sandy coast in the last 50 years: an integrated approach

NASA Astrophysics Data System (ADS)

Ponte Lira, Cristina; Nobre Silva, Ana; Taborda, Rui; Freire de Andrade, Cesar

2016-06-01

Regional/national-scale information on coastline rates of change and trends is extremely valuable, but these studies are scarce. A widely accepted standardized methodology for analysing long-term coastline change has been difficult to achieve, but it is essential to conduct an integrated and holistic approach to coastline evolution and hence support coastal management actions. Additionally, databases providing knowledge on coastline evolution are of key importance to support both coastal management experts and users.The main objective of this work is to present the first systematic, national-scale and consistent long-term coastline evolution data of Portuguese mainland low-lying sandy coasts.The methodology used quantifies coastline evolution using a unique and robust coastline indicator (the foredune toe), which is independent of short-term changes.The dataset presented comprises (1) two polyline sets, mapping the 1958 and 2010 sandy beach-dune system coastline, both optimized for working at 1 : 50 000 scale or smaller; (2) one polyline set representing long-term change rates between 1958 and 2010, each estimated at 250 m; and (3) a table with minimum, maximum and mean of evolution rates for sandy beach-dune system coastline. All science data produced here are openly accessible at https://doi.pangaea.de/10.1594/PANGAEA.859136 and can be used in other studies.Results show beach erosion as the dominant trend, with a mean change rate of -0.24 ± 0.01 m year-1 for all mainland Portuguese beach-dune systems. Although erosion is dominant, this evolution is variable in signal and magnitude in different coastal sediment cells and also within each cell. The most relevant beach erosion issues were found in the coastal stretches of Espinho-Torreira and Costa Nova-Praia de Mira, Cova da Gala-Leirosa, and Cova do Vapor-Costa da Caparica. The coastal segments Minho River-Nazaré and Costa da Caparica adjacent to the coast exhibit a history of major human interventions interfering with the coastal system, many of which originated and maintained a sediment deficit. In contrast, the coastal segments Troia-Sines and Sines-Cape S. Vicente have experienced less intervention and show stable or moderate accretion behaviour.

Chenier Development within a Prograding Strandplain Complex

NASA Astrophysics Data System (ADS)

FitzGerald, D.; Hein, C. J.; Georgiou, I. Y.

2017-12-01

Strandplains dominate the southern coast of Brazil due to abundant shelf and local sediment and falling sea-level (2-4 m) during the past 6 ka. These plains are composed chiefly of swash-aligned sandy beach and dune ridges deposited in bedrock-framed embayments 2-5 km wide and 3-10 km long. The Tijucas Strandplain developed in a more sheltered and deeply embayed setting fronted by long peninsulas and bedrock islands, which reduce ocean wave energy. The Tijucas River bisects the plain and has provided the primary source of sediment to produce a Holocene basinal fill composed of a seaward-thickening bay mud sequence (10-16 m thick). Long-term gradual shoaling of the basin and attendant lessening wave energy produced upper strandplain foreshore and beach units that transition from landward 8-m thick sand sections to a 3-4-m thick mud unit along the present-day shoreline. The gradual lateral change of the morpho-sedimentary character of the plain is likely a product of climate-induced changes in sediment composition and supply and/or wave regime. For example, the mid-plain is defined by a series of abrupt alterations between sand-dominated beach ridges and mixed sand-and-mud cheniers. This area contains at least four chenier complexes consisting of closely spaced (25-40 m apart) 50-75 m wide ridges composed of 3-4 m thick shelly sand underlain and separated by a cohesive basin-fill clay. The seaward portion of the plain has two sandy chenier ridges each 1 m high and <3 m thick, separated by 100 m of consolidated mud with rare sand beds. Ground-penetrating radar sections show ridges contain numerous seaward-sloping beds having variable dips and multiple truncations, resulting from repeated erosional and depositional events. Expansive, thin (<50 cm) sand sheets composed of flat-lying to shallowly landward-dipping internal radar reflections extend landward from most chenier ridges that overtop inter-ridge mud. The present beach comprises the most current developing chenier. Recent storm-induced landward transport of a thin, sandy overwash fan mimics the proposed mechanism for earlier ridge-swale development. Finally, a future chenier is forming 1 km offshore where breaking waves concentrate sand. Between these two sand deposits is a shallow (< 3 m) muddy region where cores and surface samples indicate an absence of sand.

Geochemistry of Mercury and other trace elements in fluvial tailings upstream of Daguerre Point Dam, Yuba River, California, August 2001

USGS Publications Warehouse

Hunerlach, Michael P.; Alpers, Charles N.; Marvin-DiPasquale, Mark; Taylor, Howard E.; DeWild, John F.

2004-01-01

This study was designed to characterize the particle-size distribution and the concentrations of total mercury (HgT), methylmercury (MeHg), and other constituents in sediments trapped behind Daguerre Point Dam, a 28-foot-high structure on the lower Yuba River in California. The results of the study will assist other agencies in evaluating potential environmental impacts from mobilization of sediments if Daguerre Point Dam is modified or removed to improve the passage of anadromous fish. Methylmercury is of particular concern owing to its toxicity and propensity to bioaccumulate. A limited amount of recent work on hydraulic and dredge tailings in other watersheds has indicated that mercury and MeHg concentrations may be elevated in the fine-grained fractions of placer mining debris, particularly clay and silt. Mercury associated with tailings from placer gold mines is a source of continued contamination in Sierra Nevada watersheds and downstream water bodies, including the Sacramento?San Joaquin Delta and the San Francisco Bay of northern California. Churn drilling was used to recover sediments and heavy minerals at 5-foot intervals from six locations upstream of Daguerre Point Dam. Maximum depth of penetration ranged from 17.5 to 35 feet below land surface, resulting in 31 discreet drilled intervals. Drilling in permeable, unconsolidated sediments below the streambed of the Yuba River released a significant volume of water along with the sediment, which complicated the sampling and characterization effort. Overflow of a silty fraction sampled at the drill site contained suspended sediment consisting predominantly of silt and clay, with HgT concentration ranging from 33 to 1,100 ng/g (nanogram per gram) dry weight. A sandy fraction, collected after sieving sediment through a 2-millimeter vibratory screen, contained from 14 to 82 percent sand and 1 to 29 percent silt plus clay, and had HgT concentrations ranging from 6.8 to 81 ng/g dry weight. A clay-silt fraction, sampled from material remaining in suspension after the sandy fraction settled for 15-20 minutes, contained mercury concentrations from 23 to 370 ng/g dry weight. Concentrations of MeHg were less than the detection limit (<0.001 ng/g dry weight) in 30 of 31 samples of the sandy fraction. In the suspended clay-silt fraction, MeHg was detected in 16 of 31 samples, in which it ranged in concentration from 0.04 (estimated) to 0.61 ng/g wet weight. Potential rates of mercury methylation and demethylation were evaluated in seven samples using radiotracer methods. Mercury methylation (MeHg production) potentials were generally low, ranging from less than 0.15 to about 1.6 ng/g/d (nanogram per gram of dry sediment per day). Mercury demethylation (MeHg degradation) potentials were moderately high, ranging from 1.0 to 2.2 ng/g/d. The ratio of methylation potential (MP) to demethylation potential (DP) ranged from less than 0.14 to about 1.4 (median = 0.24, mean = 0.44, number of samples = 7), suggesting that the potential for net production of MeHg in deep sediments is generally low. The MeHg production rates and MP/DP ratios were higher in the shallower interval in two of the three holes where two depth intervals were assessed, whereas the MeHg concentrations were higher in the shallower interval for all three holes. A similar spatial distribution was found for concentrations of solid-phase sulfide (measured as total reduced sulfur and likely representing iron-sulfide and iron-disulfide compounds), which were much higher in shallower samples (about 700 to about 2,100 nanomoles per gram, dry sediment) than in deeper samples (32 to 55 nanomoles per gram, dry sediment) in these three holes. If reduced sulfur compounds are oxidized to sulfate as a consequence of sediment disturbance, the activity of sulfate-reducing bacteria might be stimulated, causing a short-term increase in methylation of inorganic Hg(II) (divalent mercury). The extent of increased Hg(II)-methylation w

Enrichment of Geobacter species in response to stimulation of Fe(III) reduction in sandy aquifer sediments

USGS Publications Warehouse

Snoeyenbos-West, O.L.; Nevin, K.P.; Anderson, R.T.; Lovely, D.R.

2000-01-01

Engineered stimulation of Fe(III) has been proposed as a strategy to enhance the immobilization of radioactive and toxic metals in metal-contaminated subsurface environments. Therefore, laboratory and field studies were conducted to determine which microbial populations would respond to stimulation of Fe(III) reduction in the sediments of sandy aquifers. In laboratory studies, the addition of either various organic electron donors or electron shuttle compounds stimulated Fe(III) reduction and resulted in Geobacter sequences becoming important constituents of the Bacterial 16S rDNA sequences that could be detected with PCR amplification and denaturing gradient gel electrophoresis (DGGE). Quantification of Geobacteraceae sequences with a PCR most-probable-number technique indicated that the extent to which numbers of Geobacter increased was related to the degree of stimulation of Fe(III) reduction. Geothrix species were also enriched in some instances, but were orders of magnitude less numerous than Geobacter species. Shewanella species were not detected, even when organic compounds known to be electron donors for Shewanella species were used to stimulate Fe(III) reduction in the sediments. Geobacter species were also enriched in two field experiments in which Fe(III) reduction was stimulated with the addition of benzoate or aromatic hydrocarbons. The apparent growth of Geobacter species concurrent with increased Fe(III) reduction suggests that Geobacter species were responsible for much of the Fe(III) reduction in all of the stimulation approaches evaluated in three geographically distinct aquifers. Therefore, strategies for subsurface remediation that involve enhancing the activity of indigenous Fe(III)-reducing populations in aquifers should consider the physiological properties of Geobacter species in their treatment design.

Wind-driven particle mobility on Mars: Insights from Mars Exploration Rover observations at "El Dorado" and surroundings at Gusev Crater

USGS Publications Warehouse

Sullivan, R.; Arvidson, R.; Bell, J.F.; Gellert, Ralf; Golombek, M.; Greeley, R.; Herkenhoff, K.; Johnson, J.; Thompson, S.; Whelley, P.; Wray, J.

2008-01-01

The ripple field known as 'El Dorado' was a unique stop on Spirit's traverse where dust-raising, active mafic sand ripples and larger inactive coarse-grained ripples interact, illuminating several long-standing issues of Martian dust mobility, sand mobility, and the origin of transverse aeolian ridges. Strong regional wind events endured by Spirit caused perceptible migration of ripple crests in deposits SSE of El Dorado, erasure of tracks in sandy areas, and changes to dust mantling the site. Localized thermal vortices swept across El Dorado, leaving paths of reduced dust but without perceptibly damaging nearly cohesionless sandy ripple crests. From orbit, winds responsible for frequently raising clay-sized dust into the atmosphere do not seem to significantly affect dunes composed of (more easily entrained) sand-sized particles, a long-standing paradox. This disparity between dust mobilization and sand mobilization on Mars is due largely to two factors: (1) dust occurs on the surface as fragile, low-density, sand-sized aggregates that are easily entrained and disrupted, compared with clay-sized air fall particles; and (2) induration of regolith is pervasive. Light-toned bed forms investigated at Gusev are coarse-grained ripples, an interpretation we propose for many of the smallest linear, light-toned bed forms of uncertain origin seen in high-resolution orbital images across Mars. On Earth, wind can organize bimodal or poorly sorted loose sediment into coarse-grained ripples. Coarse-grained ripples could be relatively common on Mars because development of durable, well-sorted sediments analogous to terrestrial aeolian quartz sand deposits is restricted by the lack of free quartz and limited hydraulic sediment processing. Copyright 2008 by the American Geophysical Union.

Sediment dynamics in restored riparian forest with agricultural surroundings

NASA Astrophysics Data System (ADS)

Stucchi Boschi, Raquel; Cooper, Miguel; Alencar de Matos, Vitor; Ortega Gomes, Matheus; Ribeiro Rodrigues, Ricardo

2017-04-01

The riparian forests are considered Permanent Preservation Areas due to the ecological services provided by these forests. One of these services is the interception of the sediments before they reach the water bodies, which is essential to preserve water quality. The maintenance and restoration of riparian forests are mandatory, and the extent of these areas is defined based on water body width, following the Brazilian Forest Code. The method used to define the size of riparian forest areas elucidates the lack of accurate scientific data of the influence of the riparian forest in maintaining their ecological functions, particularly regarding the retention of sediments. In this study, we investigate the dynamics of erosion and sedimentation in restored riparian forests of a Semideciduous Tropical Forest situated in agricultural areas inserted in sugarcane landscapes in the state of São Paulo, Brazil. We defined two sites with soils of contrasting texture to monitor the dynamics and amount of deposited sediments. Site A is in the municipality of Araras and the soil is mainly clay. Site B is in the municipality of São Manuel and is dominated by sandy soils. In both areas, we defined plots to install graded metal stakes that were partially buried to monitor the dynamics of sediments. In site A, we defined eight plots and installed 27 metal stakes in each one. Three of the plots presented 30 m of riparian forest, two presented 15 m of riparian forest and three, 15 m of pasture followed by 15 m of forest. The design of the metal stakes was similar for all plots and was defined based on the type of erosion observed in site A. In site B, we defined seven points to monitor the sediments inside the reforested areas. Here, we observed erosive processes of great magnitude inside the forests, which results in a different design for the metal stakes. A total of nearly 150 metal stakes were installed to monitor these processes and also to verify the deposition in areas not yet affected by erosive processes of great magnitude. The monitoring of the metal stakes started in January of 2016. The data of intensity and frequency of rainfall were collected from rain gauges installed in the areas. The results show great deposition in site B, dominated by sandy soil whereas in site A, a sheet erosion process is dominant. Site A is dominated by clay soils that are not susceptible to erosion processes. In site B, a small amount of deposition was observed inside a gully, which means that the sediments may be being carried to the water bodies. A large amount of sediment was observed in areas which present a spontaneous vegetation followed by a small track of forest. Strong events were responsible for generating most of the sediments. The results will be important to support the discussion about an ideal width of riparian vegetation to ensure the retention of sediments and quality of water bodies.

The shape parameter and its modification for defining coastal profiles

NASA Astrophysics Data System (ADS)

Türker, Umut; Kabdaşli, M. Sedat

2009-03-01

The shape parameter is important for the theoretical description of the sandy coastal profiles. This parameter has previously been defined as a function of the sediment-settling velocity. However, the settling velocity cannot be characterized over a wide range of sediment grains. This, in turn, limits the calculation of the shape parameter over a wide range. This paper provides a simpler and faster analytical equation to describe the shape parameter. The validity of the equation has been tested and compared with the previously estimated values given in both graphical and tabular forms. The results of this study indicate that the analytical solutions of the shape parameter improved the usability of profile better than graphical solutions, predicting better results both at the surf zone and offshore.

Influence of a dam on fine-sediment storage in a canyon river

USGS Publications Warehouse

Hazel, J.E.; Topping, D.J.; Schmidt, J.C.; Kaplinski, M.

2006-01-01

Glen Canyon Dam has caused a fundamental change in the distribution of fine sediment storage in the 99-km reach of the Colorado River in Marble Canyon, Grand Canyon National Park, Arizona. The two major storage sites for fine sediment (i.e., sand and finer material) in this canyon river are lateral recirculation eddies and the main-channel bed. We use a combination of methods, including direct measurement of sediment storage change, measurements of sediment flux, and comparison of the grain size of sediment found in different storage sites relative to the supply and that in transport, in order to evaluate the change in both the volume and location of sediment storage. The analysis shows that the bed of the main channel was an important storage environment for fine sediment in the predam era. In years of large seasonal accumulation, approximately 50% of the fine sediment supplied to the reach from upstream sources was stored on the main-channel bed. In contrast, sediment budgets constructed for two short-duration, high experimental releases from Glen Canyon Dam indicate that approximately 90% of the sediment discharge from the reach during each release was derived from eddy storage, rather than from sandy deposits on the main-channel bed. These results indicate that the majority of the fine sediment in Marble Canyon is now stored in eddies, even though they occupy a small percentage (???17%) of the total river area. Because of a 95% reduction in the supply of fine sediment to Marble Canyon, future high releases without significant input of tributary sediment will potentially erode sediment from long-term eddy storage, resulting in continued degradation in Marble Canyon. Copyright 2006 by the American Geophysical Union.

Magnetic signature of the 22 June 1932 tsunami deposits (Jalisco, Mexican Pacific coast)

NASA Astrophysics Data System (ADS)

Bógalo, M. F.; Ramírez-Herrera, M.-T.; Goguitchaichvili, A.; Rey, D.; Mohamed, K. J.; Calvo-Rathert, M.; Corona, N.

2017-06-01

Recent studies have demonstrated that rock-magnetic analysis may provide additional information to distinguish and characterize extreme marine inundation events such as tsunamis. Rock-magnetic proxies reinforce and improve the environmental evidences supplied by other methods, adding some decisive clues for the interpretation of the origin and genesis of the sedimentary deposits. Here we report rock-magnetic, XRD, and SEM microscopy results obtained in the Palo Verde estuary (Colima Pacific coast, Mexico) in order to enhance the tools for identification and reconstruction of two tsunami-induced deposits. The sedimentary sequence includes two sand units, a tsunami deposit (PV1) associated with the 22 June 1932 tsunami and a deeper sandy layer (PV2) related to a possible paleotsunami that occurred around 1300 C.E. Both sandy units are topped by finer grained units. Magnetic properties exhibit a significant correlation with the stratigraphy. High susceptibility (χ) and high saturation isothermal remanence (SIRM) values typical of high concentrations of (titano)magnetite are a distinctive feature of the most recent sandy tsunamigenic unit PV1 and the overlaying soil. The lower sandy tsunamigenic unit PV2 shows significantly lower χ and SIRM values, indicating lower concentration of (titano)magnetite in this unit and the overlaying clayey-silt unit. The latter also shows a higher coercivity component associated with (titano)hematite. Magnetic grain-size differences are also observed between PV1 and PV2 suggesting differences in hydraulic conditions at the time of deposition. The bulk mineralogical composition and sediment texture of these units also support the hypothesis of different provenances for each tsunamigenic unit as inferred from magnetic properties.

Sandy Soil Microaggregates: Rethinking Our Understanding of Hydraulic Function

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

Paradiś, Ashley; Brueck, Christopher; Meisenheimer, Douglas

2017-01-01

This study investigated the peculiar structure of microaggregates in coarse sandy soils that exhibit only external porosity and investigated their control on soil hydrology. The microstructure underpins a hydrologic existence that differs from finer textured soils where aggregates have internal porosity. Understanding the impact of these microaggregates on soil hydrology will permit improved agricultural irrigation management and estimates associated with ecosystem capacity and resiliency. Microstructure was investigated using a digital microscope, and aspects of the structure were quantified by sedimentation and computed microtomography. Sandy soil microaggregates were observed to be comprised of a solid sand-grain core that is coated withmore » fines, presumably cemented by organic media. This microstructure leads to three distinct water pools during drainage: capillary water, followed by thick films (1–20 μm) enveloping the outer surfaces of the crusted microaggregates, followed by adsorbed thin films (<1 μm). The characteristics of the thick films were investigated using an analytical model. These films may provide as much as 10 to 40% saturation in the range of plant-available water. Using lubrication theory, it was predicted that thick film drainage follows a power law function with an exponent of 2. Thick films may also have a role in the geochemical evolution of soils and in ecosystem function because they provide contiguous water and gas phases at relatively high moisture contents. And, because the rough outer crust of these microaggregates can provide good niches for microbial activity, biofilm physics will dominate thick film processes, and consequently hydrologic, biologic, and geochemical functions for coarse sandy soils.« less

Constraining Depositional Slope From Sedimentary Structures in Sandy Braided Streams

NASA Astrophysics Data System (ADS)

Lynds, R. M.; Mohrig, D.; Heller, P. L.

2003-12-01

Determination of paleoslopes in ancient fluvial systems has potentially broad application to quantitatively constraining the history of tectonics and paleoclimate in continental sequences. Our method for calculating paleoslopes for sandy braided streams is based upon a simple physical model that establishes depositional skin-frictional shear stresses from assemblages of sedimentary structures and their associated grain size distributions. The addition of a skin-frictional shear stress, with a geometrically determined form-drag shear stress results in a total boundary shear stress which is directly related to water-surface slope averaged over an appropriate spatial scale. In order to apply this model to ancient fluvial systems, it is necessary to measure the following: coarsest suspended sediment size, finest grain size carried in bed load, flow depth, dune height, and dune length. In the rock record, suspended load and bed load can be accurately assessed by well-preserved suspended load deposits ("low-energy" ripples) and bed load deposits (dune foresets). This model predicts an average slope for the North Loup River near Taylor, Nebraska (modern case study) of 2.7 x 10-3. The measured reach-averaged water surface slope for the same reach of the river is 1.37 x 10-3. We suggest that it is possible to calculate the depositional slope of a sandy fluvial system by a factor of approximately two. Additionally, preliminary application of this model to the Lower Jurassic Kayenta Formation throughout the Colorado Plateau provides a promising and consistent evaluation of paleoslope in an ancient and well-preserved, sandy braided stream deposit.

Impact of Hurricane Sandy on the Shoreface and Inner Shelf, Offshore Long Island: Evidence for Ravinement?

NASA Astrophysics Data System (ADS)

Goff, J. A.; Austin, J. A.; Flood, R. D.; Schwab, W. C.; Denny, J. F.; Christensen, B. A.; Browne, C. M.; Saustrup, S.

2013-12-01

In January 2013, approximately two months after Hurricane Sandy made landfall in the Mid-Atlantic Bight, a scientific team from the University of Texas Institute for Geophysics, partnering with colleagues at Adelphi and Stony Brook universities and the USGS, conducted marine geophysical and surficial sampling surveys both offshore and in the inshore bays of Long Island, NY. The primary scientific goal was to assess the impact of the storm on the shoreface and inner shelf. Sandy made landfall as a post-tropical cyclone near Brigantine, NJ, with 70-kt maximum sustained winds. However, its unusual trajectory and massive size created record storm surges along the heavily-populated NJ and NY coastlines. As a result, infrastructure in the NY metropolitan area was damaged, and the Long Island barrier island system was both breached in places and elsewhere seriously eroded. The surveys included ten days of operations aboard Stony Brook's R/V Seawolf, offshore of Long Beach and Fire Island, barrier islands south of Long Island, complementing ongoing land-based studies of Sandy's impact on the NY-NJ barrier island system. Data collection involved multibeam bathymetric swath mapping, CHIRP very high resolution acoustic subbottom profiling, and surface sediment (grab) sampling to provide ground truth for the geophysical data. We surveyed regions that had been previously surveyed, both by Stony Brook in 2001 and 2005 to support reef management, and by the USGS for coastal sedimentary research, most recently in 2011 offshore Fire Island. These areas include shoreface-attached sand ridges that may be exchanging sand with the barrier island shoreface. We focus on before-and-after data comparisons on the shoreface and inner shelf, searching in particular for evidence that the storm contributed significantly to ravinement, either by wave- or current-forced erosion along the shoreface or via migration of shoreface-attached or detached sand ridges on the inner shelf. The interpreted (Holocene) transgressive ravinement surface, which may have been modified in part by Sandy, is frequently well-imaged in CHIRP data on the inner- to outer shelf; it represents the physical contrast between Holocene sands above and either Holocene estuarine (often residing in buried river channels) or older (Pleistocene) material below, typically with coarser-grained lag material at the interface. However, the process of ravinement in response to shelf-wide base-level changes is not well understood, and is also difficult to observe because it presumably happens during the most inclement of conditions. Our study provides an opportunity to investigate the ravinement process directly in response to a specific event, to link that process to the stratigraphic record, and therefore to gauge one large storm's contribution to this important part of the sediment budget for inner shelf/beach barrier systems.

GC estimation of organic hydrocarbons that threaten shallow Quaternary sandy aquifer Northwestern Gulf of Suez, Egypt.

PubMed

Zawrah, M F; Ebiad, M A; Rashad, A M; El-Sayed, E; Snousy, Moustafa Gamal; Tantawy, M A

2014-11-01

Soil and groundwater contamination is one of the important environmental problems at petroleum-related sites, which causes critical environmental and health defects. Severe petroleum hydrocarbon contamination from coastal refinery plant was detected in a shallow Quaternary sandy aquifer is bordered by Gulf in the Northwestern Gulf of Suez, Egypt. The overall objective of this investigation is to estimate the organic hydrocarbons in shallow sandy aquifers, released from continuous major point-source of pollution over a long period of time (91 years ago). This oil refinery contamination resulted mainly in the improper disposal of hydrocarbons and produced water releases caused by equipment failures, vandalism, and accidents that caused direct groundwater pollution or discharge into the gulf. In order to determine the fate of hydrocarbons, detailed field investigations were made to provide intensive deep profile information. Eight composite randomly sediment samples from a test plot were selected for demonstration. The tested plot was 50 m long × 50 m wide × 70 cm deep. Sediment samples were collected using an American auger around the point 29° 57' 33″ N and 32° 30' 40″ E in 2012 and covered an area of 2,500 m(2) which represents nearly 1/15 of total plant area (the total area of the plant is approximately 3.250 km(2)). The detected total petroleum hydrocarbons (TPHs) were 2.44, 2.62, 4.54, 4.78, 2.83, 3.22, 2.56, and 3.13 wt%, respectively. TPH was calculated by differences in weight and subjected to gas chromatography (GC). Hydrocarbons were analyzed on Hewlett-Packard (HP-7890 plus) gas chromatograph equipped with a flame ionization detector (FID). The percentage of paraffine of the investigated TPH samples was 7.33, 7.24, 7.58, 8.25, 10.25, 9.89, 14.77, and 17.53 wt%, respectively.

Characterizing a complex aquifer system using geophysics, hydrodynamics and geochemistry: A new distribution of Miocene aquifers in the Zéramdine and Mahdia-Jébéniana blocks (east-central Tunisia)

NASA Astrophysics Data System (ADS)

Lachaal, Fethi; Bédir, Mourad; Tarhouni, Jamila; Gacha, Ayadi Ben; Leduc, Christian

2011-06-01

The Zéramdine and Mahdia-Jébéniana blocks are located in the Sahel region in east-central Tunisia. Active tectonics have divided the region into numerous sub-units, as result of multiple phases of distension and compression. The Miocene fluvio-deltaic sediment sandy layers have aquiferous capacities but their hydraulic properties are still unknown, due to the lack of investigation wells. This study proposes a new description of the regional hydrogeology of Miocene deposits. Seismic-reflection and wireline logging of petroleum and water wells were used to understand the structure and the geometry of the Miocene reservoirs. The groundwater flow and its relationship to the sedimentary and tectonic context were then identified by studying piezometry and hydrochemistry. Two Miocene deep aquifer systems were identified: (1) Zéramdine-Béni Hassen to the north and (2) Jébéniana-Ksour Essef to the south. These aquifers are separated by the Mahdia graben. Other major tectonic structures, such as the Zéramdine fault corridor, the Moknine graben, and the El-Jem half-graben represent lateral boundaries for these aquifers. Other deeper sandy and clayey-sandy reservoirs were also identified in the area. Their repartition, thickness and depth vary from one block to other. Hydrodynamics of the deep aquifers seems to be controlled by geological structures. Two independent compartments were identified: in the northern block groundwater flows from West to East and from Northwest to Southeast, while in the southern block it flows from Northwest to Southeast. Geochemical facies are of two types: Na-Ca-Cl-SO 4 for the Zéramdine-Béni Hassen deep aquifer and Na-Cl for the Jébéniana-Ksour Essef deep aquifer. The hydrodynamic and geochemical results confirm the sharing of the Miocene sediments into two aquifers.

Biodiversity of shallow subtidal, under-rock invertebrates in Europe's first marine reserve: Effects of physical factors and scientific sampling

NASA Astrophysics Data System (ADS)

Trowbridge, Cynthia D.; Kachmarik, Katy; Plowman, Caitlin Q.; Little, Colin; Stirling, Penny; McAllen, Rob

2017-03-01

At Lough Hyne Marine Reserve in SW Ireland, shallow subtidal, under-rock biodiversity was investigated to assess (i) any deleterious effects of scientific sampling and (ii) quantitative baseline community patterns. Comparisons were made between 10 sites with annual rock-turning disturbance and 10 with multi-decadal (historical) disturbance. At each site, shallow subtidal rocks (N = 1289 total) were lifted, organisms recorded, and rocks replaced in their original position. Biodiversity indices were calculated to evaluate how diversity varied with location within the lough, frequency of sampling disturbance, degree of hypoxia/anoxia, dissolved oxygen (DO) concentration, and number of rocks turned. The richness of solitary invertebrates surveyed in situ averaged 21 taxa per site with significantly more in the South Basin (near the lough's connection to the ocean) than in the North Basin. The Shannon-Wiener Index did not differ significantly with variables investigated. However, evenness was higher at annually disturbed sites than at historical ones where anemones with algal symbionts often dominated. Several sites were hypoxic to anoxic under the shallow subtidal rocks. Cup corals were most abundant in the South Basin; DO was a crucial explanatory variable of these sensitive species. Solitary ascidians were most abundant at South-Basin annual sites with DO levels being a highly significant explanatory variable.

Composition, structure and properties of sediment thermal springs of Kamchatka

NASA Astrophysics Data System (ADS)

Shanina, Violetta; Smolyakov, Pavel; Parfenov, Oleg

2016-04-01

The paper deals with the physical and mechanical properties sediment thermal fields Mutnovsky, Lower Koshelevo and Bannyh (Kamchatka). This multi-component soils, mineral and chemical composition of which depends on the formation factors (pH, temperature, salinity of water, composition and structure of the host volcanic rocks). Samples Lower Koshelevo sediment thermal sources differ in the following composition: smectite, kaolinite, kaolinite-smectite mixed-mineral. Samples of sediment thermal springs Mutnovsky volcano in accordance with the X-ray analysis has the following composition: volcanic glass, crystalline sulfur, plagioclase, smectite, illite-smectite mixed, illite, chlorite, quartz, cristobalite, pyrite, melanterite, kaolinite. Natural moisture content samples of sediment thermal springs from 45 to 121%, hygroscopic moisture content of 1.3 to 3.7%. A large amount of native sulfur (up to 92%) and the presence of amorphous material gives low values of density of solid particles (up to 2.1 g/cm3) samples Mutnovskii thermal field. The values of the density of solids sediment Koshelevo and Bannyh hot springs close to those of the main components of mineral densities (up to 2.6-3.0 g/cm3). The results of the particle size distribution and microaggregate analysis of sediment thermal springs Lower Koshelevo field shows that the predominance observed of particles with a diameter from 0.05 mm to 0.25 mm, the coefficient of soil heterogeneity heterogeneous. In the bottom sediments of the thermal springs of the volcano Mutnovsky poorly traced predominance of one faction. Most prevalent fraction with particle size 0.01 - 0.05 mm. When analyzing the content in the soil microaggregates their content is shifted towards particles with a diameter of 0.25 mm. The contents of a large number of large (1-10 mm), porous rock fragments, due to the deposition of pyroclastic material from the eruptions of the last century. Present in large amounts rounded crystals of native sulfur associated with the rise of mixed solutions, formed at the boundary of secondary boil through faults to the surface thermal boiler (Bortnikova et al., 2009). Calculated flow index and plasticity, shows the classification in accordance with GOST 25100-2011. From these figures it is clear that all the sediments are sandy loam and are in a fluid state. A clear relationship between temperature, pH and particle size distribution of sediment thermal springs can not be traced, great importance is the geological evolution of the volcanic activity, hydrogeological conditions and the time factor. Therefore, samples with a currently active Mutnovsky volcano - sandy loam, sediments of the thermal springs Koshelevo fields are often to loams. The bottom sediments of thermal springs from the territory of the Lower Koshelevo thermal field in a natural occurrence in a state of higher yield strength, so they are an unstable surface, which may cause landslides. The bottom sediments of thermal springs are low explored subject of engineering geology, it is important to examine their properties to simulate the conditions of formation and the development of dangerous processes.

Distribution and bioaccumulation of selenium in aquatic microcosms

USGS Publications Warehouse

Besser, John M.; Huckins, James N.; Little, Edward E.; La Point, Thomas W.

1989-01-01

Closed-system microcosms were used to study factors affecting the fate of selenium (Se) in aquatic systems. Distribution and bioaccumulation of Se varied among sediment types and Se species. A mixture of dissolved 75Se species (selenate, selenite and selenomethionine) was sorbed more rapidly to fine-textured, highly organic pond sediments than to sandy riverine sediments. Sulfate did not affect the distribution and bioaccumulation of 75Se over the range 80–180 mg SO4 liter−1. When each Se species was labeled separately, selenomethionine was lost from the water column more rapidly than selenate or selenite. Selenium lost from the water column accumulated primarily in sediments, but volatilization was also an important pathway for loss of Se added as selenomethionine. Loss rates of dissolved Se residues were more rapid than rates reported from mesocosm and field studies, suggesting that sediment: water interactions are more important in microcosms than in larger test systems. Daphnids accumulated highest concentrations of Se, followed by periphyton and macrophytes. Selenium added as selenomethionine was bioaccumulated preferentially compared to that added as selenite or selenate. Organoselenium compounds such as selenomethione may thus contribute disproportionately to Se bioaccumulation and toxicity in aquatic organisms.

Surficial sediments on the western Canadian continental shelf

NASA Astrophysics Data System (ADS)

Bornhold, Brian D.; Barrie, J. Vaughn

1991-08-01

The active continental margin off western Canada is characterized in the south by convergence between the Explorer and Juan de Fuca Plates and the America Plate, and in the north by transform fault motion between the Pacific and America Plates along the Queen Charlotte Fault. Except in some of the deepest troughs and basins shelf sediments are dominated by immature lithic arenites reflecting this tectonic setting. The Vancouver Island shelf is from 5 to 75 km wide and displays complex topography on the inner shelf and a relatively featureless mid- and outer shelf. An exception is the area off southwestern Vancouver Island where large basins bounded by morainal deposits extend more than two-thirds of the distance across the shelf. The shelf edge varies from 180 to 225 m depth and is indented by numerous canyons. Nearshore sediments consist mainly of gravels and boulders and become finer offshore such that muds are slowly accumulating in depths greater than 100 m. Off northwestern Vancouver Island calcareous sediments are abundant with carbonate values often exceeding 75%. High wave and current energies and efficient sediment trapping in coastal fiords have resulted in low rates of accumulation. Olive, glauconitic, Holocene muds and muddy sands are generally less than 0.3 m thick and accumulate only on the outer shelf over an extensive stiff, gray, glaciomarine sandy mud. Queen Charlotte Sound exhibits three broad, shallow, glacially scoured troughs, filled mainly with clayey silts and fine sands and separated by sand and gravel covered banks. Hecate Strait, between the Queen Charlotte Islands and the mainland, consists of a prominent southward-opening trough along the east side of the Strait bounded by Dogfish and Laskeek Banks on the west adjacent to Graham and Moresby Islands, respectively. The trough below 200 m is filled by silts. The banks are covered by discontinuous sands and gravels of variable calcareous content. The bank edges often display megaripples and sand waves. Shore-parallel and oblique sand and gravel ridges occur along northernmost Dogfish Bank. Except for the inshore area (less than 100 m) off northern Graham Island little is known of the sediment distribution in Dixon Entrance. Off northwestern Graham Island the near shore zone is dominated by bedrock and discontinuous sands and gravels made up of up to 90% skeletal carbonate. Off northeastern Graham Island sandy sediments predominate in the nearshore. No studies have been undertaken on the narrow shelf off the western Queen Charlotte Islands.

High-resolution geophysical data from the sea floor surrounding the Western Elizabeth Islands, Massachusetts

USGS Publications Warehouse

Pendleton, Elizabeth A.; Twichell, David C.; Foster, David S.; Worley, Charles R.; Irwin, Barry J.; Danforth, William W.

2011-01-01

Geophysical and geospatial data were collected in the nearshore area surrounding the western Elizabeth Islands, Massachusetts on the U.S. Geological Survey research vessel Rafael during September 2010 in a collaborative effort between the U.S. Geological Survey and the Massachusetts, Office of Coastal Zone Management. This report describes the results of the short-term goals of this collaborative effort, which were to map the geology of the inner shelf zone of the western Elizabeth Islands and study the geologic processes that have contributed to its evolution. Data collected during the survey include: Bathymetric and sidescan-sonar data, chirp seismic-reflection data , sound velocity profiles, and navigation data. The long-term goals of this project are to provide high-resolution geophysical data that will support research on the influence of sea-level change and sediment supply on coastal evolution and inventory subtidal marine habitat type and distribution within the coastal zone of Massachusetts.

Suggested nomenclature change and new reference locality for Dequeen Formation, Pike County, Arkansas

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

Ham, T.L.; Landry, R.J.

1983-09-01

The DeQueen Formation of the Trinity Group, Comanchean Cretaceous, crops out in southwestern Arkansas and southeastern Oklahoma. The outcrop, located in the Highland gypsum quarry of Pike County, southwestern Arkansas, is described in detail in this paper and presented as a reference locality. Data from the locality provide the basis for a nomenclature change from the DeQueen Limestone Member to the DeQueen Formation. The formation consists of 64.23% clastic sediments, 24.72% gypsum, and 11.05% limestone. Hopper salt casts, ripple marks, scattered pyrite and marcasite nodules, celestite, and chickenwire gypsum can also be found. The DeQueen Formation is underlain by claysmore » and the Ultima Thule Gravel lentil, while the top is unconformably overlain by Upper Cretaceous Tokio gravels. The general paleoenvironment represents a normally low-energy subtidal environment ranging from brackish to normal to hypersaline waters in a lagoonal setting that shallows upward.« less

Evidence of tidal processes from the lower part of the Witwatersrand Supergroup, South Africa

NASA Astrophysics Data System (ADS)

Eriksson, Kenneth A.; Turner, Brian R.; Vos, Richard G.

1981-08-01

A 1600-m succession of quartz arenites and associated shaley deposits comprising the Hospital Hill Subgroup at the base of the Witwatersrand Supergroup is considered to have been deposited largely under the influence of tidal processes. Facies analysis indicates that deposition occurred in the following environments: (1) marine shalf; (2) shallow subtidal to intertidal; (3) intertidal flat; and (4) tidal inlet. The presence of strong tidal currents implies that the Witwatersrand Basin was open to an ocean basin, at least during the early stages of its evolution. Palaeocurrent trends and isopach data suggest that this probably lay to the southwest, an area now occupied by the high grade Natal—Namaqua metamorphic belt. The contrast between the supermature quartz arenites of the Hospital Hill Subgroup and the overlying gold-bearing immature subgreywackes, feldspathic quartzites and conglomerates of fluvial origin is believed to be a function of tidal reworking of sediments.

Quaternary geology and geologic hazards of the West Desert Hazardous Industry Area, Tooele County, Utah

USGS Publications Warehouse

Solomon, Barry J.; Black, Bill D.; ,

1990-01-01

The study of Quaternary geology provides information to evaluate geologic conditions and identify geologic constraints on construction in the West Desert Hazardous Industry Area (WDHIA). The WDHIA includes portions of the Great Salt Lake Desert to the west, underlain by several thousand feet of sediments capped by saline mudflats, and Ripple Valley to the east, separated from the Desert by the Grayback Hills and underlain by several hundred feet of sediments in the Cedar Mountains piedmont zone. Quaternary surficial units include marginal, shore-zone, and deep-water lacustrine sediments deposited in Pleistocene Lake Bonneville; eolian deposits; and alluvial sediments. The level of Lake Bonneville underwent major oscillations resulting in the creation of four basin-wide shorelines, three of which are recognized in the WDHIA. Geologic hazards in the WDHIA include the possible contamination of ground water in basin-fill aquifers, debris flows and flash floods in the piedmont zone, and earthquakes and related hazards. Numerous factors contribute to unsafe foundation conditions. Silty and sandy sediments may be subject to liquefaction or hydrocompaction, clayey sediments and mud flats of the Great Salt Lake Desert may be subject to shrinking or swelling, and gypsiferous dunes and salt flats are subject to subsidence due to dissolution.

Sedimentology, geochemistry, pollution status and ecological risk assessment of some heavy metals in surficial sediments of an Egyptian lagoon connecting to the Mediterranean Sea.

PubMed

El-Said, Ghada F; Draz, Suzanne E O; El-Sadaawy, Manal M; Moneer, Abeer A

2014-01-01

Spatial distribution of heavy metals (Co, Cu, Ni, Cr, Mn, Zn and Fe) was studied on Lake Edku's surface sediments in relation to sedimentology and geochemistry characteristics and their contamination status on the ecological system. Lake Edku's sediments were dominated by sandy silt and silty sand textures and were enriched with carbonate content (9.83-58.46%). Iron and manganese were the most abundant heavy metals with ranges of 1.69 to 8.06 mg g(-1) and 0.88 to 3.27 mg g(-1), respectively. Cobalt and nickel showed a harmonic distribution along the studied sediments. The results were interpreted by the statistical means. The heavy metal pollution status and their ecological risk in Lake Edku was evaluated using the sediment quality guidelines and the contamination assessment methods (geoaccumulation, pollution load and potential ecological risk indices, enrichment factor, contamination degree as well as effect range median (ERM) and probable effect level (PEL) quotients). Amongst the determined heavy metals, zinc had the most ecological risk. Overall, the heavy metals in surface sediments showed ecological effect range from moderate to considerable risk, specially, in the stations in front of the seawater and in drain sources that had the highest toxic priority.

Warming intensify CO2 flux and nutrient release from algal wrack subsidies on sandy beaches.

PubMed

Lastra, Mariano; López, Jesús; Rodil, Iván F

2018-04-18

Algal wrack subsidies underpin most of the food web structure of exposed sandy beaches and are responsible of important biogeochemical processes that link marine and terrestrial ecosystems. The response in decomposition of algal wrack deposits to global warming has not been studied in ocean-exposed sandy beaches to date. With this aim, passive open top chambers (OTCs) were used to increase soil temperature within the range predicted by the IPCC for western Europe (between 0.5 and 1.5°C), following the hypothesis that the biogeochemical processing of macroalgal wrack subsidies would accelerate in response to temperature increase. The effect of temperature manipulation on three target substrates: fresh and aged macroalgae, and bare sand, was tested. Results indicated that a small warming (<0.5°C) affected the wrack decomposition process through traceable increases in soil respiration through CO 2 flux, inorganic nutrients within the interstitial environment (N and P), sediment organic contents measured through the amount of proteins and microbial pool through the total soil DNA. The different responses of soil variables in the studied substrates indicated that the decomposition stage of stranded macroalgae influences the biogeochemical processing of organic matter in sandy beaches. Thus, CO 2 fluxes, releases of organic and inorganic nutrients and microbial activity intensify in aged wrack deposits. Our results predict that expected global warming will increase the release of inorganic nutrients to the coastal ocean by 30% for the N (21 Gg/year) and 5.9% for P (14 Gg/year); that increase for the flow of C to the atmosphere as CO 2 was estimated in 8.2% (523 Gg/year). This study confirms the key role of sandy beaches in recycling ocean-derived organic matter, highlighting their sensitivity to a changing scenario of global warming that predicts significant increases in temperature over the next few decades. © 2018 John Wiley & Sons Ltd.

The impact of Hurricane Sandy on the shoreface and inner shelf of Fire Island, New York: large bedform migration but limited erosion

USGS Publications Warehouse

Goff, John A.; Flood, Roger D.; Austin, James A.; Schwab, William C.; Christensen, Beth A.; Browne, Cassandra M.; Denny, Jane F.; Baldwin, Wayne E.

2015-01-01

We investigate the impact of superstorm Sandy on the lower shoreface and inner shelf offshore the barrier island system of Fire Island, NY using before-and-after surveys involving swath bathymetry, backscatter and CHIRP acoustic reflection data. As sea level rises over the long term, the shoreface and inner shelf are eroded as barrier islands migrate landward; large storms like Sandy are thought to be a primary driver of this largely evolutionary process. The “before” data were collected in 2011 by the U.S. Geological Survey as part of a long-term investigation of the Fire Island barrier system. The “after” data were collected in January, 2013, ~two months after the storm. Surprisingly, no widespread erosional event was observed. Rather, the primary impact of Sandy on the shoreface and inner shelf was to force migration of major bedforms (sand ridges and sorted bedforms) 10’s of meters WSW alongshore, decreasing in migration distance with increasing water depth. Although greater in rate, this migratory behavior is no different than observations made over the 15-year span prior to the 2011 survey. Stratigraphic observations of buried, offshore-thinning fluvial channels indicate that long-term erosion of older sediments is focused in water depths ranging from the base of the shoreface (~13–16 m) to ~21 m on the inner shelf, which is coincident with the range of depth over which sand ridges and sorted bedforms migrated in response to Sandy. We hypothesize that bedform migration regulates erosion over these water depths and controls the formation of a widely observed transgressive ravinement; focusing erosion of older material occurs at the base of the stoss (upcurrent) flank of the bedforms. Secondary storm impacts include the formation of ephemeral hummocky bedforms and the deposition of a mud event layer.

Granulometric analysis at Lampulo Fishing Port (LFP) substrate, Banda Aceh, Indonesia

NASA Astrophysics Data System (ADS)

Purnawan, S.; Setiawan, I.; Haridhi, H. A.; Irham, M.

2018-01-01

The study of sediment granulometry was completed at Lampulo fishing port (LFP). The LFP is a main fishing port in Aceh Province, Indonesia, located at 5°34’35” N; 95°19’23” E. The purpose of the research is to study and construct the environment condition of the bottom substrate. The data was taken by incorporating coring method at 10 stations using purposive random sampling. The wet sieve method was used to analyze the grain size for geostatistical analysis. The geostatistical parameters analysis in this study is classified as mean, sorting, skewness and kurtosis. The result informs that the types of sediments are sand, sandy clay and clayey sand for all stations. Station 1, however, is found as the coarsest compares to the other stations. All of the sediment collected at each station displays moderately sorted to poor sorted, while kurtosis values may be categorized as very leptokurtic. The results of the sediment parameters indicate that the environment of harbor pool was in a stable state, related to a sheltered condition.

Early Triassic environmental dynamics and microbial development during the Smithian-Spathian transition (Lower Weber Canyon, Utah, USA)

NASA Astrophysics Data System (ADS)

Grosjean, Anne-Sabine; Vennin, Emmanuelle; Olivier, Nicolas; Caravaca, Gwénaël; Thomazo, Christophe; Fara, Emmanuel; Escarguel, Gilles; Bylund, Kevin G.; Jenks, James F.; Stephen, Daniel A.; Brayard, Arnaud

2018-01-01

The Early Triassic biotic recovery following the end-Permian mass extinction is well documented in the Smithian-Spathian Thaynes Group of the western USA basin. This sedimentary succession is commonly interpreted as recording harsh conditions of various shallow marine environments where microbial structures flourished. However, recent studies questioned the relevance of the classical view of long-lasting deleterious post-crisis conditions and suggested a rapid diversification of some marine ecosystems during the Early Triassic. Using field and microfacies analyses, we investigate a well-preserved Early Triassic marine sedimentary succession in Lower Weber Canyon (Utah, USA). The identification of microbial structures and their depositional settings provide insights on factors controlling their morphologies and distribution. The Lower Weber Canyon sediments record the vertical evolution of depositional environments from a middle Smithian microbial and dolosiliciclastic peritidal system to a late Smithian-early Spathian bioclastic, muddy mid ramp. The microbial deposits are interpreted as Microbially Induced Sedimentary Structures (MISS) that developed either (1) in a subtidal mid ramp where microbial wrinkles and chips are associated with megaripples characterizing hydrodynamic conditions of lower flow regime, or (2) in protected areas of inter- to subtidal inner ramp where they formed laminae and domal structures. Integrated with other published data, our investigations highlight that the distribution of these microbial structures was influenced by the combined effects of bathymetry, hydrodynamic conditions, lithology of the substrat physico-chemical characteristics of the depositional environment and by the regional relative sea-level fluctuations. Thus, we suggest that local environmental factors and basin dynamics primarily controlled the modalities of microbial development and preservation during the Early Triassic in the western USA basin.

Relationships Between Sand and Water Quality at Recreational Beaches

PubMed Central

Phillips, Matthew C.; Solo-Gabriele, Helena M.; Piggot, Alan M.; Klaus, James S.; Zhang, Yifan

2011-01-01

Enterococci are used to assess the risk of negative human health impacts from recreational waters. Studies have shown sustained populations of enterococci within sediments of beaches but comprehensive surveys of multiple tidal zones on beaches in a regional area and their relationship to beach management decisions are limited. We sampled three tidal zones on eight South Florida beaches in Miami-Dade and Broward counties and found that enterococci were ubiquitous within South Florida beach sands although their levels varied greatly both among the beaches and between the supratidal, intertidal and subtidal zones. The supratidal sands consistently had significantly higher (p<0.003) levels of enterococci (average 40 CFU/g dry sand) than the other two zones. Levels of enterococci within the subtidal sand correlated with the average level of enterococci in the water (CFU/100mL) for the season during which samples were collected (rs= 0.73). The average sand enterococci content over all the zones on each beach correlated with the average water enterococci levels of the year prior to sand samplings (rs=0.64) as well as the average water enterococci levels for the month after sand samplings (rs=0.54). Results indicate a connection between levels of enterococci in beach water and sands throughout South Florida’s beaches and suggest that the sands are one of the predominant reservoirs of enterococci impacting beach water quality. As a result, beaches with lower levels of enterococci in the sand had fewer exceedences relative to beaches with higher levels of sand enterococci. More research should focus on evaluating beach sand quality as a means to predict and regulate marine recreational water quality. PMID:22071324

Relationships between sand and water quality at recreational beaches.

PubMed

Phillips, Matthew C; Solo-Gabriele, Helena M; Piggot, Alan M; Klaus, James S; Zhang, Yifan

2011-12-15

Enterococci are used to assess the risk of negative human health impacts from recreational waters. Studies have shown sustained populations of enterococci within sediments of beaches but comprehensive surveys of multiple tidal zones on beaches in a regional area and their relationship to beach management decisions are limited. We sampled three tidal zones on eight South Florida beaches in Miami-Dade and Broward counties and found that enterococci were ubiquitous within South Florida beach sands although their levels varied greatly both among the beaches and between the supratidal, intertidal and subtidal zones. The supratidal sands consistently had significantly higher (p < 0.003) levels of enterococci (average 40 CFU/g dry sand) than the other two zones. Levels of enterococci within the subtidal sand correlated with the average level of enterococci in the water (CFU/100mL) for the season during which samples were collected (r(s) = 0.73). The average sand enterococci content over all the zones on each beach correlated with the average water enterococci levels of the year prior to sand samplings (r(s) = 0.64) as well as the average water enterococci levels for the month after sand samplings (r(s) = 0.54). Results indicate a connection between levels of enterococci in beach water and sands throughout South Florida's beaches and suggest that the sands are one of the predominant reservoirs of enterococci impacting beach water quality. As a result, beaches with lower levels of enterococci in the sand had fewer exceedences relative to beaches with higher levels of sand enterococci. More research should focus on evaluating beach sand quality as a means to predict and regulate marine recreational water quality. Copyright © 2011 Elsevier Ltd. All rights reserved.

Modifications to the bottomless lift net for sampling nekton in tidal mangrove forests

USGS Publications Warehouse

McIvor, C.C.; Silverman, N.L.

2010-01-01

Sampling fishes in vegetated intertidal wetlands is logistically challenging. We modified the 2 ?? 3-m2 bottomless lift net developed for sampling nekton (fish and decapod crustaceans) on the surface of salt marshes for use in tidal mangrove forests with a woody (as opposed to herbaceous) underground root system. As originally designed (Rozas, Mar Ecol Prog Ser 89:287-292, 1992), the lift net was buried directly in the marsh substrate. The net was raised at slack high tide thereby encircling nekton within the enclosed area. A chain-line on the net bottom prevented escape under the net once deployed. However, when we used this same design in tidal mangrove forests, the extensive woody roots and occasional slumping sediments resulted in uneven trenches that could not be cleared effectively during sample recovery. We made 3 modifications to the original net design: (i) lined the peat trenches with aluminum channels of uniform width and depth; (ii) replaced the previous chain-line with Velcro closures that directly attached the net to the inner face of the outer wall of the aluminum channel; and (iii) removed the subtidal pan previously used for concentrating the enclosed nekton at low tide, and filled in those depressions with on-site peat. In the modified version, the aluminum trench became the only subtidal refuge available to nekton, and it was from here that we collected the sample after the forest drained. These modifications permitted high clearing efficiency (93-100%) of fin-clipped individuals of two common species of estuarine resident fishes, Kryptolebias marmoratus (mangrove rivulus) and Bathygobius soporator (frillfin goby). Additionally, the density estimates of grass shrimp (Palaemonetes spp.) increased 10-fold post-modification. ?? 2010 US Government.

Infiltration in layered loessial deposits: Revised numerical simulations and recharge assessment

NASA Astrophysics Data System (ADS)

Dafny, Elad; Šimůnek, Jirka

2016-07-01

The objective of this study is to assess recharge rates and their timing under layered loessial deposits at the edge of arid zones. Particularly, this study is focused on the case of the coastal plain of Israel and Gaza. First, results of a large-scale field infiltration test were used to calibrate the van Genuchten parameters of hydraulic properties of the loessial sediments using HYDRUS (2D/3D). Second, optimized soil hydraulic parameters were used by HYDRUS-1D to simulate the water balance of the sandy-loess sediments during a 25-year period (1990-2015) for three environmental conditions: bare soil, and soil with both sparse and dense natural vegetation. The best inverse parameter optimization run fitted the infiltration test data with the RMSE of 0.27 d (with respect to a moisture front arrival) and R2 of 96%. The calibrated model indicates that hydraulic conductivities of the two soil horizons, namely sandy loam and sandy clay loam, are 81 cm/d and 17.5 cm/d, respectively. These values are significantly lower than those previously reported, based on numerical simulations, for the same site. HYDRUS-1D simulation of natural recharge under bare soil resulted in recharge estimates (to the aquifer) in the range of 21-93 mm/yr, with an average recharge of 63 mm/yr. Annual precipitation in the same period varied between 100 and 300 mm/yr, with an average of 185 mm/yr. For semi-stabilized dunes, with 26% of the soil surface covered by local shrub (Artemisia monosperma), the mean annual recharge was 28 mm. For the stabilized landscape, with as much as 50% vegetation coverage, it was only 2-3 mm/yr. In other words, loessial sediments can either be a source of significant recharge, or of no recharge at all, depending on the degree of vegetative cover. Additionally, the time lag between specific rainy seasons and corresponding recharge events at a depth of 22 m, increased from 2.5 to 5 years, and to about 20 years, respectively, with an increasing vegetative cover. For this reason, and also likely due to a great depth of loessial sediments, no correlation was found between annual recharge and annual precipitations of the same year or subsequent years. Similarly, no differences were found between summer and winter recharge fluxes. Instead, numerical simulations indicated continuous year-round recharge of the aquifer. We conclude that the layered subsurface acts as a short-term (annual) and long-term (multi-annual) buffer to smooth sudden precipitation/infiltration events. Vegetation conditions can help in predicting long-term recharge rates (as percentage of annual precipitation), which in turn need to be considered when assigning recharge characteristics in regional assessments and models.

Frequent but hidden eruptions of Adatara and Bandai volcanoes during the last 50,000 years unraveled by volcanic damlake sediments, northeast Japan

NASA Astrophysics Data System (ADS)

Kataoka, Kyoko; Nagahashi, Yoshitaka

2017-04-01

Adatara and Bandai volcanoes in the northeast Japan are very close to each other ( 18 km). Bandai volcano is well known for a large-scale debris avalanche following the phreatic eruption in AD1888 that took more than 400 fatalities. Eruptive history consists of at least 6 more debris avalanche events, 3 more phreatic eruptions, 6 lava flows, and 4 Vulcanian/sub-Plinian eruptions during the last 50,000 years revealed by subaerial proximal deposits. Whereas, the eruptive history of Adatara volcano comprises 6 Vulcanian and 5 phreatic eruptions during the last 10,000 years. The most recent eruption occurred in AD1899-1900. The studied sedimentary core (INW2012) was drilled out from Lake Inawashiro-ko, the largest dammed lake in Japan, that was formed by the 50 ka Okinajima debris avalanche event at Bandai volcano. The lake is 94 m deep, and drilling site is located at the central part of the lake ( 90 m deep). In the 28 m long core sequence, in contrast to background lake sediments deposited under a deep offshore environment, very frequent (70) intercalations of event layers are recognized. Eight types of event layers can be recognized: 1) gray muddy layer (Gm), 2) gray sandy layer (Gs), 3) brown muddy layer (Bm), 4) brown sandy layer (Bs), 5) olive-gray muddy layer, 6) pale-brown sandy layer, and 7) yellow sandy layer, and 8) 2011 earthquake-induced turbidite, based on the characteristics of sedimentary facies, petrography, grainsize, mineral assemblages (XRD) and vertical variation of chemistry (micro-XRF). There are many tephra-fall layers but most of them are extra-basinal origin, i.e., of other volcanoes than Adatara and Bandai. Gm is usually a few millimeters to centimeters thick, blue-gray color, homogenized, and finer than background sediments. Gs is accompanied with coarser subunits and thicker than Gm. Especially, Gm/Gs contain pyrite, sulfate minerals and smectite, and are characterized by high sulfur contents. Bm and Bs are 1 to 6 cm thick and are normally graded with a sharp erosive base. Fresh glass shards and organic material are commonly present. The gray units (Gm/Gs) can be correlated with muddy lahars (cohesive debris flows/mudflows) in the Sukawa River catchment of Adatara volcano. High-sulfur contents indicate syn- or post-eruptive lahars in relation with phreatic eruptions or degradation of hydrothermally altered source rocks nearby the crater. The brown units (Bm/Bs) are thicker than those of gray units that suggest more proximal origin. The fresh glass shards and chemistry of those shards in brown units are unlikely to be reworking of pre-existing old tephra deposits, and therefore the events are attributed to magmatic eruption-fed density currents from Bandai. Since depositional rates of background lake sediments are stable, the frequent eruption-related events both from Adatara and Bandai volcanoes can be well dated. These event deposits reveal unknown eruptive history of Adatara and Bandai as they were more active during the last 50,000 years than previously known. Appropriate evaluation for small-scale but high frequent eruptions and their risk assessments are necessary for Inawashiro Town (15,000 population) located at the foot/downstream of the volcanoes.

Relict gas hydrates as possible reason of gas emission from shallow permafrost at the northern part of West Siberia

NASA Astrophysics Data System (ADS)

Chuvilin, Evgeny; Bukhanov, Boris; Tumskoy, Vladimir; Istomin, Vladimir; Tipenko, Gennady

2017-04-01

Intra-permafrost gas (mostly methane) is represent a serious geological hazards during exploration and development of oil and gas fields. Special danger is posed by large methane accumulations which usually confined to sandy and silty sand horizons and overlying in the frozen strata on the depth up to 200 meters. Such methane accumulations are widely spread in a number of gas fields in the northern part of Western Siberia. According to indirect indicators this accumulations can be relic gas hydrates, that formed earlier during favorable conditions for hydrate accumulation (1, 2). Until now, they could be preserved in the frozen sediments due to geological manifestation of the self-preservation effect of gas hydrates at temperatures below zero. These gas hydrate formations, which are lying above the gas hydrate stability zone today, are in a metastable state and are very sensitive to various anthropogenic impacts. During drilling and operation of production wells in the areas where the relic of gas hydrates can occur, there are active gas emission and gas explosion, that can lead to various technical complications up to the accident. Mathematical and experimental simulations were were conducted to evaluate the possibility of existence of relic gas hydrates in the northern part of West Siberia. The results of math simulations revealed stages of geological history when the gas hydrate stability zone began virtually from the ground surface and saturated in shallow permafrost horizons. Later permafrost is not completely thaw. Experimental simulations of porous gas hydrate dissociation in frozen soils and evaluation of self-preservation manifestation of gas hydrates at negative temperatures were carried out for identification conditions for relic gas hydrates existence in permafrost of northern part of West Siberia. Sandy and silty sand sediments were used in experimental investigations. These sediments are typical of most gas-seeping (above the gas hydrate stability zone) permafrost horizons. The results show that all investigated frozen hydrate-bearing sandy and silty sand samples in the temperature range from -16 °C to -2 °C are characterized by not complete decomposition of pore hydrate at relieving pressure below the equilibrium. It was observed that at typical north Western Siberian permafrost temperature of -6 ° C the safety of pore hydrate in frozen samples can reach 60% at the pressure reducing below the equilibrium. In was found that with increasing temperature and particle size (dispersity) the efficiency of pore hydrate self-preservation is decreased, but even at the temperature of -2 °C there is residual pore methane hydrate content in non-saline sandy samples. All this suggests about high preservation of methane hydrates in frozen sediments at non-equilibrium thermobaric conditions, close to reservoir conditions. Based on the results of mathematical and experimental simulations about the possibility of relic gas hydrates existence on permafrost depth up to 200 m in the northern part of Western Siberia on the less than 200 m due to geological manifestation of the self-preservation effect of gas hydrates. References. 1.Chuvilin EM, Yakushev VS, Perlova EV. Gas and gas hydrates in the permafrost of Bovanenkovo gas field, Yamal Peninsula, West Siberia. // Polarforschung 68: 215-219, 1998. (erschienen 2000). 2.Yakushev V.S., Chuvilin E.M. 2000. Natural gas and hydrate accumulation within permafrost in Russia. Cold Regions Science and Technology. 31: 189-197. These researches are supported by grant RSF №16-17-00051.

Influence of bioturbation on sediment respiration in advection- and diffusion-dominated systems

NASA Astrophysics Data System (ADS)

Baranov, Viktor; Krause, Stefan; Lewandowski, Jörg

2017-04-01

Ecosystem engineers are organisms, whose impact on ecosystem functioning is large compared to their abundance and biomass. Classic examples of ecosystem engineers are burrowing organisms whose activity is affecting the sediment matrix and pore solutes in aquatic sediments; this is called bioturbation. Constant reworking of the sediment matrix and transport of solutes caused by activities of sediment-dwelling organisms are modifying habitats and resource availability. Despite that progress of studies on the interactions between the animal bioturbation and the sediment respiration was rather slow, mostly due to the existing methodological limitations. Conceptual framework, formulated by Mermelloid-Blondin and Rosenberg (2006) is suggesting that impact of bioturbation on the sediment biogeochemistry will be much larger in sediments with low hydraulic conductivities (diffusion-dominated) than in sediments with high hydraulic conductivities (advection-dominated). In order to test this hypothesis in application to the sediment respiration, we have used the resazurin-resorufin bioreactive tracer system, which allowed us to decouple respiration of the sediment of microbiota. Our work has shown that in diffusion-dominated sediments (organic rich lake sediments) bioturbator's (bloodworms, larvae of Diptera, Chironomidae) activity could increase sediment aerobic respiration by 300%. In addition to that, impact of the bioturbators on the diffusion-dominated sediments respiration is growing with increasing temperature. Total oxygen consumption (TOU) in such sediments is also increasing by about 50% in bioturbated sediments in comparison with uninhabited sediments. On the other hand, in advection-dominated sediments (sandy sediments from marine tidal flats, bioturbated by brittlestars) we have observed no increase in TOU, and only slight (25%) increase in aerobic respiration in the presence of bioturbators. It became evident that due to the high hydraulic conductivity of advection-dominated sediments, alteration in solutes and nutrient distribution are minimal, hence no increase in TOU occurs. Still, presence of bioturbators has increased aerobic respiration of the system (probably due to animals' own respiration and the burrow-associated microbiota), thus not increasing but re-structuring TOU.

Experimental Oxidation of Iron Sulphides from Intertidal Surface Sediments: Stable Isotope Effects (S, O, C)

NASA Astrophysics Data System (ADS)

Ebersbach, F.; Böttcher, M. E.; Al-Raei, A. M.; Segl, M.

2009-04-01

Top intertidal sediments show a pronounced zone of activities of sulphate-reducing bacteria. Iron sulfides may be formed, but a substantial part is reoxidized to sulfate. Microbial or chemical reoxidation can be further enhanced by a resuspension of surface sediments by tidal currents or storms. The rates of the different processes depend on the site-secific sedimentological properties (e.g., grain size, iron and sulphur contents etc.). In the present study 3 different areas of the German Wadden Sea were studied: a mud flat in the Jade Bay, and sandy sediments in the intertidals of Spiekeroog and Sylt islands. The latter site is part of an in-situ lugworm-exclusion experiment. The goal was the experimental and field investigation of the fate of iron sulfides and the formation of sulphate upon resuspension of intertidal surface sediments in oxygenated seawater. All sites were geochemically analyzed for dissolved and solid phase iron, manganese, sulphur and carbon phases/species, and sulphate reduction rates were measured using radiotracers. Dissolved chloride and grain sizes analysis where additionally carried out. TOC, S and metal phase contents were higher in mud compared to sandy sediments. Field results demonstrate gross but only minor net sulphide production and a downcore increases in FeS contents, due to intense sulphide oxidation at the surface. Pyrite, on the other hand, was abundant through the sediments due to continuous sediment reworking. The fate of iron-sulphides and accumulation of sulphate as a function of time was followed in batch experiments using dark suspensions of surface sediments in site-bottom waters at room temperature. During the experiments, each sample was shaken continuously under exposition to oxygen, and sub-samples were taken at the beginning and after discrete time intervalls. A very fast oxidation rate of AVS led to a complete exhaustion within a day, whereas Cr(II)-reducible sulfur was inititially built up and then decreased. This observation can be explained by a formation of S° and FeOOH, followed by the oxidation of pyrite. The dissolved species (SO4/Cl ratios) reflected the continuous accumulation of sulphate as an oxidation product. Dissolved inorganic carbonate (DIC) concentrations decreased upon reaction progress, due to the liberation of protons upon iron sulphide oxidation and degassing of carbon dioxide. The 13C/12C ratio of the residual DIC increased due to the preferential desorption of 12CO2. 34S and 18O contents of dissolved sulphate further show process specific isotope discrimination. The experiments demonstrate the importance of oxidation on the fate of FeS , but less pyrite and the formation of sulphate from resuspended intertidal surface sediments. Acknowledgements: The authors gratefully acknowledge discussions and field advice by N. Volkenborn, and financial support from Deutsche Forschungsgemeinschaft during DFG-SPP ‚BioGeoChemistry of the Wadden Sea' (JO 307/4, BO 1584/4), Max Planck Society, and Leibniz-IO Warnemünde.

The Importance of Actualistic Source-to-Sink Sand Provenance Studies in Illuminating the Nature of Ancient Fluvial Systems From the Deep-Marine Clastic Successions They Sourced

NASA Astrophysics Data System (ADS)

Marsaglia, K. M.; Parra, J. G.; Dawson, S.

2006-12-01

Successions of gravity-flow deposits in deep-marine fan systems have the potential to record the evolution of their fluvial source region as well as specific tectonic, climatic, eustatic and anthropogenic events. Deciphering these signals involves the description and quantification of key sediment attributes such as fan volume, the rate of sediment accumulation, the frequency of depositional events, sediment texture, and sediment composition. Sediment composition/provenance provides insight into the nature of the fluvial source, including drainage basin geology and drainage development. For example, Marsaglia et al. (1995) demonstrated a connection between source river lengthening owing to eustatic change and sand composition in Quaternary turbidite successions of the Santa Barbara Basin at Ocean Drilling Program (ODP) Site 893. In contrast, longer-term compositional trends recognized in the Mesozoic to Cenozoic rift-to-drift successions cored by various ODP legs on the North Atlantic margins are more likely associated with continental margin drainage development and fluvial system evolution (Marsaglia et al., in press). These two connections between sink and source were made possible by well-documented petrologic data sets for both modern onshore fluvial systems and older offshore deep-marine successions, but in each case different workers collected the onshore and offshore data sets. In the Waipaoa River Sedimentary System of North Island, New Zealand we have taken a different, more holistic approach, with a limited and linked group of researchers and sample data base covering the complete system. The study area is an active forearc margin characterized by uplifted and deformed sedimentary successions and periodic input of arc-derived ash. Recently, the modern onshore system has been thoroughly documented via studies of the petrology of outcropping Mesozoic to Cenozoic units, fluvial terrace deposits, and modern fluvial sediments (e.g., James et al., in press). Now we are building on that data set and moving from source-to-sink to trace sandy sediment through the system out onto the shelf and slope where it has been encountered in shallow cores. Lessons learned onshore, such as a distinct compositional dependence on grain size and the relationships of bedrock geology to certain sand grain types, also apply to these offshore core samples. Many of the sandy intervals are largely composed of reworked tephra from Taupo eruptions, whereas quartz and feldspar dominate finer sand samples. Lithic-dominated sands are less common and coarser grained. Isolated greywacke gravel clasts indicate that at some point coarse sediment "leaked" into the basin from the south. The volumetric importance of this extrabasinal input can be assessed by looking at the types and proportions of lithic fragments within the finer sand fraction.

The morphodynamic significance of rapid shoreline progradation followed by vertical foredune building at Pedro Beach, southeastern Australia

NASA Astrophysics Data System (ADS)

Oliver, Thomas; Tamura, Toru; Short, Andrew; Woodroffe, Colin

2017-04-01

Prograded coastal barriers are accumulations of marine and aeolian sands configured into shore-parallel ridges. A variety of ridge morphologies described around the world reflect differences in origin as a consequence of differing prevailing coastal morphodynamics. The 'morphodynamic approach' described by Wright and Thom (1977) expounds the coastal environmental conditions, hydrodynamic and morphodynamic processes and inheritance of evolutionary sequences over varying temporal scales which interdependently operate to produce an assemblage of coastal landforms adjusted, or adjusting to, a dynamic equilibrium. At Pedro Beach on the southeastern coast of Australia a large sandy deposit of foredune ridges provides an opportunity to explore the morphodynamic paradigm as it applies to coastal barrier systems using optically stimulated luminescence (OSL) dating, ground penetrating radar (GPR) and airborne LiDAR topography. The prograded barrier at Pedro Beach has formed following the stabilisation of the sea level at its present height on the southeast Australian coastline. A series of dune-capped ridges, increasing in height seawards, formed from 6000 years ago to 4000 years ago. During this time the shoreline straightened as bedrock accommodation space for Holocene sediments diminished. Calculation of Holocene sediment volumes utilising airborne LiDAR topography shows a decline in sediment volume over this time period coupled with a decrease in shoreline progradation rate from 0.75 m/yr to 0.49 m/yr. The average ridge 'lifetime' during this period increases resulting in higher ridges as dune-forming processes have longer to operate. Greater exposure to wave and wind energy also appears to have resulted in higher ridges as the sheltering effect of marginal headlands has diminished. A high outer foredune has formed through vertical accretion in the past 700 years, evidenced by GPR subsurface structures and upward younging of OSL ages, with a sample from 1 m deep within the crest of this dune returning an age of 90 ± 10. An inherited disequilibrium shoreface profile will drive onshore accumulation of sandy sediments forming a prograded barrier; however, if there is no longer 'accommodation space' for sediment, this will be an overriding factor causing the cessation of progradation as occurred 4000 years ago at Pedro Beach. Following progradation cessation, excess sediment in the disequilibrium shoreface profile will be moved alongshore as barrier progradation (embayment filling) has diminished the potential of headlands to act as impediments to sediment bypassing in the nearshore. It is hypothesised that the chronology and geomorphology of the Pedro Beach barrier system typifies the changing 'strength of influence' in the interaction between geologically inherited accommodation space, sediment delivery and beach/dune/shoreface dynamics over the mid-late Holocene. Wright, L. D., & Thom, B. G. (1977). Coastal depositional landforms: a morphodynamic approach. Progress in Physical Geography, 1(3), 412-459.

Laboratory Investigations and Numerical Modeling of Loss Mechanisms in Sound Propagation in Sandy Sediments

DTIC Science & Technology

2009-09-30

poroelastic medium,” Submitted for publication in J. Acoust . Soc. Am., (2009). 9. B.T. Hefner, D.R. Jackson, and J. Calantoni, “The effects of...B.T. Hefner and D.R. Jackson, “Dispersion and attenuation due to scattering from heterogeneities the frame bulk modulus of a poroelastic medium,” Submitted for publication in J. Acoust . Soc. Am., (2009). ...DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Laboratory Investigations and Numerical Modeling of Loss

Major, trace and REE geochemistry of recent sediments from lower Catumbela River (Angola)

NASA Astrophysics Data System (ADS)

Vinha, Manuela; Silva, M. G.; Cabral Pinto, Marina M. S.; Carvalho, Paula Cristina S.

2016-03-01

The mineralogy, texture, major, trace and rare earth elements, from recent sediment samples collected in the lower Catumbela River, were analysed in this study to characterize and discuss the factors controlling its geochemistry and provide data that can be used as tracers of Catumbela River inputs to the Angolan continental shelf. The sediments are mainly sands and silty-sands, but sandy-silt also occurs and the mineralogy is composed of quartz, feldspar, phyllosilicates, magnetite, ilmenite and also carbonates when the river crosses limestones and marls in the downstream sector. The hydraulic sorting originates magnetite-ilmenite and REE-enriched minerals placers. The mineralogy of the sediments is controlled by the source rocks and the degree of chemical weathering is lower than erosion. The texture is mainly controlled by location. There is enrichment in all the analysed trace elements in the fine grained, clay minerals and Fe-oxy-hydroxides rich sediments, compared to the coarse grained and quartz plus feldspar rich ones. The coarse grained sediments (without the placers) are impoverished in ΣREE when compared with UCC and NASC compositions, while the fine grained sediments have ΣREE contents similar to UCC and NASC. The placers have ΣREE contents up to 959.59 mg/kg. The source composition is the dominant factor controlling the REE geochemistry of the analysed sediments as there is no difference in the (La/Yb)N, (La/Sm)N and (Gd/Yb)N ratios in coarse and fine grained sediments. The sorting of magnetite, ilmenite, zircon, throrite, thorianite, rutile and titanite explain the HREE/LREE enriched patterns of the coarse grained sediments.

Character and provenance of aeolian sediments in northeast Thailand

NASA Astrophysics Data System (ADS)

Nichol, Janet E.; Nichol, Douglas W.

2015-12-01

Aeolian activity is not generally associated with the humid tropics, and although reports of loess-like soils in various locations in southeast Asia exist, these mainly lack the detailed analysis to set them in meaningful spatial or historical context. This paper examines the red and yellow sandy sediments of the Khorat Plateau in northeast Thailand which have been variously referred to as 'cover sands', 'loessial soils' or 'loess'. The sediments are referred to as having alluvial, biological as well as aeolian origin, and a date of 9-35 ka is reported. The study compares the Khorat sediments physically and geochemically with loess and aeolian sediments from other regions, as well as with other sites in southeast Asia which are reported here. The moderate degree of particle sorting and unimodal sizes of the sediments along with a sub-spherical sub-rounded form, supports previous diagnoses of an aeolian origin. Geochemical analysis of the Khorat sediments indicates severe depletion in both mobile and immobile elements, which are even more depleted than other southeast Asian loessic soils examined. This depletion, along with the only moderate particle sorting, suggests the source of the sediments to be the local weathered sandstones outcropping around the edge of the Khorat Plateau. The dissimilarity of the Khorat sediments from Upper Continental Crust (UCC) elemental values supports this, as homogenisation would occur if diverse source areas were involved. The study suggests that aeolian sediments of humid tropical regions warrant more attention as climate proxy markers, due to the dissimilarity between the present climate and conditions required for their formation.

Response of coliform populations in streambed sediment and water column to changes in nutrient concentrations in water.

PubMed

Shelton, D R; Pachepsky, Y A; Kiefer, L A; Blaustein, R A; McCarty, G W; Dao, T H

2014-08-01

As sediments increasingly become recognized as reservoirs of indicator and pathogen microorganisms, an understanding of the persistence of indicator organisms becomes important for assessment and predictions of microbial water quality. The objective of this work was to observe the response of water column and sediment coliform populations to the change in nutrient concentrations in the water column. Survival experiments were conducted in flow-through chambers containing sandy sediments. Bovine feces were collected fresh and introduced into sediment. Sixteen days later, the same fecal material was autoclaved and diluted to provide three levels - 1×, 0.5×, and 0.1× of nutrient concentrations - spike in water column. Total coliforms, Escherichia coli, and total aerobic heterotrophic bacterial concentrations were monitored in water and sediment. Bacteria responded to the nutrient spike with initial growth both in the water column and in sediment. The response of bacterial concentrations in water column was nonlinear, with no significant changes at 0.1 and .5× spikes, but a substantial change at 1× spike. Bacteria in sediment responded to the spikes at all added nutrient levels. Coliform inactivation rates both in sediment and in water after the initial growth occurred, were not significantly different from the inactivation rates before spike. These results indicate that introduction of nutrients into the water column results in nonlinear response of E. coli concentrations both in water and in sediments, followed by the inactivation with the same rate as before introduction of nutrients. Published by Elsevier Ltd.

Efficiency and mechanism of the phytoremediation of decabromodiphenyl ether-contaminated sediments by aquatic macrophyte Scirpus validus.

PubMed

Zhao, Liangyuan; Jiang, Jinhui; Chen, Chuanhong; Zhan, Shuie; Yang, Jiaoyan; Yang, Shao

2017-05-01

Phytoremediation is an economic and promising technique for removing toxic pollutants from the environment. Freshwater sediments are regarded as the ultimate sink of the widely used PBDE congener decabromodiphenyl ether (BDE-209) in the environment. In the study, the aquatic macrophyte Scirpus validus was selected to remove BDE-209 from three types of sediments (silt, clay, and sand) at an environmentally relevant concentration. After 18 months of phytoremediation experiment, S. validus significantly enhanced the dissipation rates of BDE-209 in all the sediments compared to the controls. Average removal rates of BDE-209 in the three treatments of silt, clay, and sandy sediments with S. validus were respectively 92.84, 84.04, and 72.22%, which were 148, 197, and 233% higher than that in the control sediments without S. validus. In the phytoremediation process, the macrophyte-rhizosphere microbe combined degradation was the main pathway of BDE-209 removal. Sixteen lower brominated PBDE congeners (di- to nona-) were detected in the sediments and plant tissues, confirming metabolic debromination of BDE-209 in S. validus. A relatively higher proportion of penta- and di-BDE congeners among the metabolites in plant tissues than that in the sediments indicated further debromination of PBDEs within plants. The populations and activities of microorganisms in the sediments were greatly promoted by S. validus. Bacterial community structure in BDE-209-contaminated rhizosphere sediments was different from that in the control rhizosphere sediment, as indicated by the dominant proportions of β-proteobacteria, δ-proteobacteria, α-proteobacteria, Acidobacteria, and Chloroflexi in the microbial flora. All these results suggested that S. validus was effective in phytoremediation of BDE-209 by the macrophyte-rhizosphere microbe combined degradation in aquatic sediments.

Interactions of Cd and Cu in anaerobic estuarine sediments. 1: Partitioning in geochemical fractions of sediments

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

Rule, J.H.; Alden, R.W. III

1996-04-01

Partitioning of Cd and Cu between geochemical fractions of an anaerobic estuarine sediment was determined after equilibrating fine-sandy sediment with different combinations of added Cd (0, 2.5, 5 mg/kg) and Cu(0, 12.5, 25 mg/kg). Sediments were placed in aquaria with 20 ppt seawater where bioassay test organisms were exposed for 14 d. At the start and conclusion of the experimental period, sediments were sequentially extracted to determine the elemental content of the exchangeable (EP), easily reducible (ERP), organic- sulfide (OSP), moderately reducible (MRP), and acid extractable (AEP) phases. Partitioning of the metals in both the native and treated sediments was,more » for Cd: OSP {much_gt} ERP > AEP > EP (MRP was below detection) and for Cu: OSP {much_gt} AEP > ERP > MRP > EP. Cadmium extracted in all phases and Cu in the EP, RP, and OSP were proportional to the respective treatments. The EP-Cd, ERP-Cd, and OSP-Cd were affected by the Cu treatment and significant interactions occurred between Cd and Cu for the EP-Cd, ERP-Cd, OSP-Cd, EP-Cu, and ERP-Cu. Increasing levels of applied Cd and Cu resulted in greater amounts of EP-Cd and ERP-Cd, fractions that are the most bioavailable and the most readily available for desorption into the water column. A significant conclusion is that the input of nontoxic metals may affect the geochemical phase distribution, potential bioavailability, and toxicity of native sediment metals.« less

Characterization of Gas-Hydrate Sediment: In Situ Evaluation of Hydrate Saturation in Pores of Pressured Sedimental Samples

NASA Astrophysics Data System (ADS)

Jin, Y.; Konno, Y.; Kida, M.; Nagao, J.

2014-12-01

Hydrate saturation of gas-hydrate bearing sediment is a key of gas production from natural gas-hydrate reservoir. Developable natural gas-hydrates by conventional gas/oil production apparatus almost exist in unconsolidated sedimental layer. Generally, hydrate saturations of sedimental samples are directly estimated by volume of gas generated from dissociation of gas hydrates in pore spaces, porosity data and volume of the sediments. Furthermore, hydrate saturation can be also assessed using velocity of P-wave through sedimental samples. Nevertheless, hydrate saturation would be changed by morphological variations (grain-coating, cementing and pore-filling model) of gas hydrates in pore spaces. Jin et al.[1,2] recently observed the O-H stretching bands of H2O molecules of methane hydrate in porous media using an attenuated total reflection IR (ATR-IR) spectra. They observed in situ hydrate formation/dissociation process in sandy samples (Tohoku Keisya number 8, grain size of ca. 110 μm). In this presentation, we present IR spectroscopy approach to in situ evaluation of hydrate saturation of pressured gas-hydrate sediments. This work was supported by funding from the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) planned by the Ministry of Economy, Trade and Industry (METI), Japan. [1] Jin, Y.; Konno, Y.; Nagao, J. Energy Fules, 2012, 26, 2242-2247. [2] Jin, Y.; Oyama, H.; Nagao, J. Jpn. J. Appl. Phys. 2009, 48, No. 108001.

Distribution of selenium, molybdenum and uranium in sediment cores from the Colorado River delta, Baja California, Mexico.

PubMed

Orozco-Durán, A; Daesslé, L W; Gutiérrez-Galindo, E A; Muñoz-Barbosa, A

2012-01-01

The distribution of selenium, molybdenum and uranium was studied in ~1.5 m sediment cores from the Colorado River delta, at the Colorado (CR) and Hardy (HR) riverbeds. Core HR2 showed highest Se, Mo and U concentrations at its bottom (2.3, 0.95 and 1.8 μg g(-1)) within a sandy-silt layer deposited prior to dam construction. In CR5 the highest concentrations of these elements (0.9, 1.4 and 1.7 μg g(-1) respectively) were located at the top of the core within a surface layer enriched in organic carbon. A few samples from HR2 had Se above the probable toxic effect level guidelines.

Coastal landscape evolution on the western margin of the Bahía Blanca Estuary (Argentina) mirrors a non-uniform sea-level fall after the mid-Holocene highstand

NASA Astrophysics Data System (ADS)

Pratolongo, Paula; Piovan, María Julia; Cuadrado, Diana G.; Gómez, Eduardo A.

2017-08-01

Sedimentary descriptions and radiocarbon ages from two cores obtained from coastal plains along the western margin of the Bahía Blanca Estuary (Argentina) were integrated with previous information on landscape patterns and plant associations to infer landscape evolution during the mid-to-late Holocene. The study area comprises at least two marine terraces of different elevations. The old marine plain (OMP), at an average elevation of 5 m above mean tidal level (MTL), is a nearly continuous flat surface. The Recent marine plain (RMP), 2 to 3 m above MTL, is a mosaic of topographic highs and elongated depressions that may correspond to former tidal channels. Mollusks at the base of the OMP core (site elevation 5.09 m above MTL), with ages between 5,660 ± 30 and 5,470 ± 30 years BP, indicate a subtidal setting near the inland limits of the marine ingression. The sandy bottom of the core is interpreted as the last stage of the transgressive phase, followed by a tight sequence of dark laminated muds topped by a thick layer of massive gray muds. The RMP core (site elevation 1.80 m above MTL) has a similar sedimentary sequence, but unconformities appear at lower elevations and the massive mud deposits are less developed. The thickness of the grayish mud layer is a major difference between the OMP and RMP cores, but deeper layers have similar ages, suggesting a common origin at the end of the transgressive phase. The overlying massive muds would correspond to rapid sedimentation during a high sea-level stillstand or slow regression. It is proposed that, after a rapid sea-level drop to about 3 m above MTL, a flat and continuous surface corresponding to the OMP emerged, and more recent coastal dynamics shaped the dissected landscape of the RMP. For the Bahía Blanca Estuary, smooth regressive trends have been proposed after the mid-Holocene highstand, but also stepped curves. A stillstand or slowly dropping sea level was described around 3,850 ± 100 years BP, as well as negative relative sea-level oscillations. In this study, the differentiation between the OMP and the RMP supports the occurrence of a stepped regressive trend that, at least locally, presented two different stages.

Data on nearshore wave process and surficial beach deposits, central Tamil Nadu coast, India.

PubMed

Joevivek, V; Chandrasekar, N

2017-08-01

The chronicles of nearshore morphology and surficial beach deposits provide valuable information about the nature of the beach condition and the depositional environment. It imparts an understanding about the spatial and temporal relationship of nearshore waves and its influence over the distribution of beach sediments. This article contains data about wave and sediment dynamics of the ten sandy beaches along the central Tamil Nadu coast, India. This present dataset comprises nearshore wave parameters, breaker wave type, beach morphodynamic state, grain size distribution and weight percentage of heavy and light mineral distribution. The dataset will figure out the beach morphology and hydrodynamic condition with respect to the different monsoonal season. This will act as a field reference to realize the coastal dynamics in an open sea condition. The nearshore entities were obtained from the intensive field survey between January 2011 and December 2011, while characteristics of beach sediments are examined by the chemical process in the laboratory environment.

Comment on “On AGU's Position Statement, ‘Human Impacts on Climate’”

NASA Astrophysics Data System (ADS)

Evans, Rob

2009-08-01

Regarding the Forum by Cyril Galvin (Eos, 89(46), 459, 2008), while I understand AGU's willingness to present both sides of the coin, as it were, I am disappointed that this Forum appeared in Eos. One major point in question is the assertion by Galvin that “nowhere on the sandy ocean shores of the world is there a beach whose erosion has been documented to be caused by sea level rise.” This point disregards the fact that coastal barrier systems have been moving landward for the last several thousand years, driven by rising sea level. Yes, the picture is complex, and yes, wave action and storms, in addition to constraints on sediment supply—many of them heavily influenced in the present day by societal actions—are also important: Some beaches will erode without rising sea level if they are starved of new sediment to replace that removed by wave-driven, alongshore currents, and it is of course the waves that move the sediment around.

Integrated assessment of mangrove sediments in the Camamu Bay (Bahia, Brazil).

PubMed

Paixão, Joana F; de Oliveira, Olívia M C; Dominguez, José M L; Almeida, Edna dos Santos; Carvalho, Gilson Correia; Magalhães, Wagner F

2011-03-01

Camamu Bay, an Environmentally Protected Area, may be affected by the pressures of tourism and oil exploration in the adjacent continental platform. The current quality of the mangrove sediments was evaluated by porewater bioassays using embryos of Crassostrea rhizophorae and by an analysis of benthic macrofauna and its relationships with organic compounds, trace metals and bioavailability. Porewater toxicity varied from low to moderate in the majority of the samples, and polychaetes dominated the benthos. The Grande Island sampling station (Station 1) presented more sandy sediments, differentiated macrobenthic assemblages and the highest metal concentrations in relation to other stations and guideline values, and it was the only station that indicated a possible bioavailability of metals. The origin of the metals (mainly barium) is most likely associated with the barite ore deposits located in the Grande and Pequena islands. These results may be useful for future assessment of the impact of oil exploration in the coastal region. Copyright © 2010 Elsevier Inc. All rights reserved.

Contribution of inorganic and organic components to sorption of neutral and ionizable pharmaceuticals by sediment/soil.

PubMed

Yamamoto, Hiroshi; Takemoto, Kohei; Tamura, Ikumi; Shin-Oka, Norihiro; Nakano, Takahiro; Nishida, Masayo; Honda, Yuta; Moriguchi, Shigemi; Nakamura, Yudai

2018-03-01

Our previous study showed that the sorption coefficient of certain polar pharmaceuticals to river sediment, especially particular amines, was unexpectedly high. Thus, we conducted sorption experiments of selected polar pharmaceuticals and pyrene derivatives, including amines, carboxylic acids, and neutral compounds, to model clay minerals, i.e., montmorillonite and kaolin, in addition to silica sands and humic substances. The contribution of each component was roughly estimated by simple fractionation of the individual sorption coefficients. Relatively high sorption coefficients (K d values) were found, especially for amines on clay minerals, which suggest that electrochemical affinity may play an important role. The estimated contribution percentage suggests a relatively large contribution from inorganic constituents, such as clay minerals, for silt loam soil; in contrast, organic components predominantly contribute for sandy river sediments. These findings could be the key to understanding not only the fate and transport but also bioavailability and environmental risks of pharmaceuticals, which are mostly polar and/or ionizable.

Application of ecological, geological and oceanographic ERTS-1 imagery to Delaware's coastal resources management

NASA Technical Reports Server (NTRS)

Klemas, V. (Principal Investigator); Bartlett, D. S.; Philpot, W. D.; Davis, G. R.; Rogers, R. H.; Reed, L.

1974-01-01

The author has identified the following significant results. Data from twelve successful ERTS-1 passes over Delaware Bay have been analyzed with special emphasis on coastal vegetation, land use, current circulation, water turbidity and pollution dispersion. Secchi depth, suspended sediment concentration and transmissivity as measured from helicopters and boats were correlated with ERTS-1 image radiance. Multispectral signatures of acid disposal plumes, sediment plumes and slick were investigated. Ten vegetative cover and water discrimination classes were selected for mapping: (1) forest-land; (2) Phragmites communis; (3) Spartina patens and Distichlis spicata; (4) Spartina alterniflora; (5) cropland; (6) plowed cropland; (7) sand and bare sandy soil; (8) bare mud; (9) deep water; and (10) sediment-laden and shallow water. Canonical analysis predicted good classification accuracies for most categories. The actual classification accuracies were very close to the predicted values with 8 of 10 categories classified with greater than 90% accuracy indicating that representative training sets had been selected.

Shoreline ecology program for Prince William Sound, Alaska, following the Exxon Valdez oil spill. Part 3: Biology

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

Gilfillan, E.S.; Page, D.S.; Harner, E.J.

1995-12-31

This study describes the biological results of a comprehensive shoreline ecology program designed to assess ecological recovery in Prince William Sound following the Exxon Valdez oil spill on march 24, 1989. The program is an application of the ``Sediment Quality Triad`` approach, combining chemical, toxicological, and biological measurements. The study was designed so that results could be extrapolated to the entire spill zone in Prince William Sound. The spill affected four major shoreline habitat types in Prince William Sound: pebble/gravel, boulder/cobble, sheltered bedrock, and exposed bedrock. The study design had two components: (1) one-time stratified random sampling at 64 sitesmore » representing four habitats and four oiling levels (including unoiled reference sites) and (2) periodic sampling at 12 nonrandomly chosen sites that included some of the most heavily oiled locations in the sound. Biological communities on rock surfaces and in intertidal and shallow subtidal sediments were analyzed for differences resulting from to oiling in each of 16 habitat/tide zone combinations. Statistical methods included univariate analyses of individual species abundances and community parameter variables (total abundance, species richness, and Shannon diversity), and multivariate correspondence analysis of community structure. 58 refs., 13 figs., 9 tabs.« less

Microbial communities in sediment from Zostera marina patches, but not the Z. marina leaf or root microbiomes, vary in relation to distance from patch edge

PubMed Central

Ettinger, Cassandra L.; Voerman, Sofie E.; Lang, Jenna M.; Stachowicz, John J.

2017-01-01

Background Zostera marina (also known as eelgrass) is a foundation species in coastal and marine ecosystems worldwide and is a model for studies of seagrasses (a paraphyletic group in the order Alismatales) that include all the known fully submerged marine angiosperms. In recent years, there has been a growing appreciation of the potential importance of the microbial communities (i.e., microbiomes) associated with various plant species. Here we report a study of variation in Z. marina microbiomes from a field site in Bodega Bay, CA. Methods We characterized and then compared the microbial communities of root, leaf and sediment samples (using 16S ribosomal RNA gene PCR and sequencing) and associated environmental parameters from the inside, edge and outside of a single subtidal Z. marina patch. Multiple comparative approaches were used to examine associations between microbiome features (e.g., diversity, taxonomic composition) and environmental parameters and to compare sample types and sites. Results Microbial communities differed significantly between sample types (root, leaf and sediment) and in sediments from different sites (inside, edge, outside). Carbon:Nitrogen ratio and eelgrass density were both significantly correlated to sediment community composition. Enrichment of certain taxonomic groups in each sample type was detected and analyzed in regard to possible functional implications (especially regarding sulfur metabolism). Discussion Our results are mostly consistent with prior work on seagrass associated microbiomes with a few differences and additional findings. From a functional point of view, the most significant finding is that many of the taxa that differ significantly between sample types and sites are closely related to ones commonly associated with various aspects of sulfur and nitrogen metabolism. Though not a traditional model organism, we believe that Z. marina can become a model for studies of marine plant-microbiome interactions. PMID:28462046

Complex, Dynamic Combination of Physical, Chemical and Nutritional Variables Controls Spatio-Temporal Variation of Sandy Beach Community Structure

PubMed Central

Ortega Cisneros, Kelly; Smit, Albertus J.; Laudien, Jürgen; Schoeman, David S.

2011-01-01

Sandy beach ecological theory states that physical features of the beach control macrobenthic community structure on all but the most dissipative beaches. However, few studies have simultaneously evaluated the relative importance of physical, chemical and biological factors as potential explanatory variables for meso-scale spatio-temporal patterns of intertidal community structure in these systems. Here, we investigate macroinfaunal community structure of a micro-tidal sandy beach that is located on an oligotrophic subtropical coast and is influenced by seasonal estuarine input. We repeatedly sampled biological and environmental variables at a series of beach transects arranged at increasing distances from the estuary mouth. Sampling took place over a period of five months, corresponding with the transition between the dry and wet season. This allowed assessment of biological-physical relationships across chemical and nutritional gradients associated with a range of estuarine inputs. Physical, chemical, and biological response variables, as well as measures of community structure, showed significant spatio-temporal patterns. In general, bivariate relationships between biological and environmental variables were rare and weak. However, multivariate correlation approaches identified a variety of environmental variables (i.e., sampling session, the C∶N ratio of particulate organic matter, dissolved inorganic nutrient concentrations, various size fractions of photopigment concentrations, salinity and, to a lesser extent, beach width and sediment kurtosis) that either alone or combined provided significant explanatory power for spatio-temporal patterns of macroinfaunal community structure. Overall, these results showed that the macrobenthic community on Mtunzini Beach was not structured primarily by physical factors, but instead by a complex and dynamic blend of nutritional, chemical and physical drivers. This emphasises the need to recognise ocean-exposed sandy beaches as functional ecosystems in their own right. PMID:21858213