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Estuaries represent the primary linkage between the terrestrial and marine carbon cycles, and estuarine processing of riverine and coastal carbon plays a disproportionately large role in the global carbon cycle relative to the small areal extent of the estuarine environments. However, knowledge of the rate of organic carbon deposition and burial in estuarine sediments is lacking at regional scales. Data on surficial total organic carbon, linear sedimentation, and bulk density of estuarine sediments were compiled and categorized via a cluster analysis in order to estimate carbon deposition within the contiguous United States (CONUS). The cluster analysis broadly grouped estuaries by geography, but exceptions to geographic clustering highlighted differences within regions. A transfer function from deposition to burial based on linear sedimentation rate was used to estimate burial efficiency, and thus the rate of carbon burial within each cluster. We estimate organic carbon deposition rates within CONUS estuarine sediments to be 161 [121–217, 95% confidence] g C/m2/yr with a burial efficiency estimated at 38 [34–42, 95% confidence] %, which yields a long‐term burial rate of 64 [44–97, 95% confidence] g C/m2/yr. Spatially integrated organic deposition and burial rates are 11.3 [8.5–15.2, 95% confidence] and 4.5 [3.1–6.8, 95% confidence] Tg C/yr, respectively. Our findings allow a more thorough understanding of coastal carbon cycling, which is critical for both management purposes as well as for the assessment of the role of estuaries in past and future climate change. Plain Language Summary: Estuaries are diverse ecosystems located at the coastal mouth of rivers or within embayments, where terrestrial and marine environments meet. Estuaries tend to be highly productive and provide many critical ecosystem services for their communities. Carbon‐based material delivered primarily by rivers or produced by aquatic organisms is deposited within the sediments of estuaries. Organisms in sediments consume some of the deposited material and respire it principally as carbon dioxide. However, a portion is buried within deeper sediments and is removed from the contemporary carbon cycle. The rate of material deposited and ultimately buried can influence the function of the estuary as well as its relation to communities and the adjacent coastal ecosystems. On longer time scales (many thousands of years), this removal can also influence the global carbon cycle. We grouped estuaries based on their physical and chemical characteristics and estimated sediment deposition and burial rates for the contiguous United States, where we found that approximately 40% of deposited material was buried within sediments. Key Points: Sedimentation processes in estuaries within the contiguous United States are estimated to deposit 11.3 [8.5–15.2, 95% confidence] Tg of carbon per yearRemineralization liberates a significant portion of deposited carbon, yielding centennial‐scale burial of 4.5 [3.1–6.8, 95% confidence] Tg carbon per yearEstuaries of the contiguous United States are classified into six clusters based on geospatial and biogeochemical characteristics using k‐means analysis [ABSTRACT FROM AUTHOR]

Abstract: For the first time, electron spin resonance optical dating (ESROD) has been conducted on littorally transported and aeolian siliciclastic sediments in Florida. ESROD utilizes light-sensitive radiation-sensitive defects at silicon sites that have been replaced by aluminum and titanium atoms to give rise to a time-dependant signal. These defects saturate at higher levels of radiation dose, compared to optically stimulated luminescence, and therefore extend the optical dating range back into the millions of years. Our results show that the Trail Ridge Sequence is a multi-depositional unit that began deposition around 2.2Ma and continued until 6ka. The Osceola Cape, of the Effingham Sequence, was deposited around 1.5Ma, and the Chatham Sequence was a multi-depositional terrace with at least three events preserved. [Copyright &y& Elsevier]

The Coastal Inlets Research Program (CIRP) of the U.S. Army Engineer Research and Development Center (ERDC), Coastal and Hydraulics Laboratory (CHL) has developed a nearshore spectral wave transformation numerical model to address needs of the U.S. Army Corps of Engineers (USACE) navigation projects. The model is called CMS-Wave and is part of Coastal Modeling System (CMS) for wave estimates in the vicinity of coastal and estuarine navigation channels. It can simulate important wave processes at coastal inlets including wave diffraction, refraction, reflection, wave breaking and dissipation mechanisms, wave-current interaction, and wave generation and growth. This paper describes recent improvements in CMS-Wave that include semi-empirical estimates of wave run-up and overtopping, nonlinear wave-wave interactions, and wave dissipation over muddy bottoms. CMS-Wave may be used with nested grids and variable rectangular cells in a rapid mode to assimilate full-plane wave generation for circulation and sediment transport models. A brief description of these recent capabilities is provided. [ABSTRACT FROM AUTHOR]

pplications of process-based morphodynamic models are often constrained by limited availability of data on bed composition, which may have a considerable impact on the modeled morphodynamic development. One may even distinguish a period of 'morphodynamic spin-up' in which the model generates the bed level according to some ill-defined initial bed composition rather than describing the realistic behavior of the system. The present paper proposes a methodology to generate bed composition of multiple sand and/or mud fractions that can act as the initial condition for the process-based numerical model Delft3D. The bed composition generation (BCG) run does not include bed level changes, but does permit the redistribution of multiple sediment fractions over the modeled domain. The model applies the concept of an active layer that may differ in sediment composition above an underlayer with fixed composition. In the case of a BCG run, the bed level is kept constant, whereas the bed composition can change. The approach is applied to San Pablo Bay in California, USA. Model results show that the BCG run reallocates sand and mud fractions over the model domain. Initially, a major sediment reallocation takes place, but development rates decrease in the longer term. Runs that take the outcome of a BCG run as a starting point lead to more gradual morphodynamic development. Sensitivity analysis shows the impact of variations in the morphological factor, the active layer thickness, and wind waves. An important but difficult to characterize criterion for a successful application of a BCG run is that it should not lead to a bed composition that fixes the bed so that it dominates the 'natural' morphodynamic development of the system. Future research will focus on a decadal morphodynamic hindcast and comparison with measured bathymetries in San Pablo Bay so that the proposed methodology can be tested and optimized. [ABSTRACT FROM AUTHOR]

Abstract: The Upper Pennsylvanian Indian Cave Sandstone (ICS) in southeastern Nebraska is herein reinterpreted as three multistory incised valley fills and one single-storey channel fill, altogether representing at least two different intervals of time. ICS lithosomes are linear bodies, as much as 2000 m wide and 30 m thick, incised into pre-existing cyclothems, and have relatively steep sides and flat bases. They include crudely fining-upwards successions of trough cross-bedded sandstones, interpreted as tidally-influenced fluvial deposits, overlain by upper estuarine heterolithic facies, with local coals, and a restricted trace fossil assemblage. The vertical facies succession suggests sediment accumulation in a regime of gradually increasing accommodation, i.e., during rising relative sea level. The basal erosion surfaces of ICS bodies can be traced out onto the adjacent interfluves where they correspond to well-developed paleosols, indicating sequence boundaries. Furthermore, the sequences defined herein can be correlated closely with recently published sequence stratigraphic frameworks from the region, suggesting that the ICS bodies record repeated, fifth-order (Milankovitch band), relative sea-level fluctuations of a minimum of 30 m during latest Pennsylvanian time Significantly, this estimate is half or less of those made by many other studies. Such a local quantification of relative sea-level change provides a critical constraint on eustatic sea-level fluctuation during the late Paleozoic Gondwanan Ice Age. [Copyright &y& Elsevier]

To use bioassessments to help diagnose or identify the specific environmental stressors affecting estuaries, we need a better understanding of the relation- ships among sediment chemistry guidelines, ambient toxicity tests, and community metrics. However, this relationship is not simple because metrics generally assess the responses at the community level of biological organization whereas sediment guidelines and ambient toxicity tests generally assess or are based on the responses at the organism level. The relationship may be further complicated by the influence of other chemical and physical variables that affect the bioavailability and toxicity of chemical contaminants in the environment. Between 1990 and 1993, the U.S. Environmental Protection Agency (USEPA) conducted an Environmental Monitoring and Assessment Program (EMAP) survey of estuarine sites in the Virginian Province of the eastern United States. The surveys collected data on benthic assemblages, physical and chemical habitat characteristics, and sediment chemistry and toxicity. We characterized these estuarine sites as affected by sediment contamination based on the exceedence of sediment guidelines or on ambient sediment toxicity tests (i.e., 10-day Anipelisca abdita survival). Then, benthic invertebrate metrics were compared among affected and unaffected sites to identify metrics sensitive to the contamination. A number of benthic invertebrate metrics differed between groups of sites segregated using the organism-level measures whereas other metrics did not. The difference among metrics appears to depend on the sensitivity of the individual metrics to the stressor gradient represented by metals or persistent organic toxics in sediments because the insensitive metrics do not effectively quantify the changes in the benthic invertebrate assemblage associated with these stressors. The significant relationships suggest that a relationship exists between the organism-level effects assessed by chemistry or ambient toxicity tests and the community-level effects assessed by community metrics and that the organism-level effects are predictive, to some extent, of community-level effects. [ABSTRACT FROM AUTHOR]

Prior studies exploring the quantitative relationship between landscape structure metrics and the ecological condition of receiving waters have used a variety of sampling units (e.g., a watershed, or a buffer around a sampling station) at a variety of spatial scales to generate landscape metrics resulting in little consensus on which scales best describe land-water relationships. Additionally, the majority of these studies have focused on freshwater systems and it is not clear whether results are transferable to estuarine and marine systems. We examined how sampling unit scale controls the relationship between landscape structure and sediment metal concentrations in small estuarine systems in the Mid-Atlantic region of the United States. We varied the spatial extent of the contributing watersheds used to calculate landscape structure and assessed linear relationships between estuarine sediment metal concentrations and the total area of developed and agricultural lands at each scale. Area of developed lands was consistently related to sediment metals while total agricultural land was not. Developed land had strongest associations with lead and copper; weakest with arsenic and chromium; and moderate associations with cadmium, mercury, and zinc. Local (i.e., less than 15-20 km from a sampling station) land uses have a greater impact than more distant land uses on the amount of toxic metals reaching estuarine sediments. [ABSTRACT FROM AUTHOR]

Abstract: Contaminated surficial sediments in major ports and harbors remain a significant economic liability during routine dredging operations. Numerous beneficial uses have been suggested in recent years that promise reduced sediment management costs concomitant with a productive material use. This manuscript describes the leaching of metals and metalloids from surficial sediments and from controlled low strength material (flowable fill) produced using the estuarine sediments as replacement for sand. Sediments from two locations within the New York/New Jersey Harbor area (Gowanus Canal and Newtown Creek) (USA), were subjected to pH-dependent leaching tests and liquid-to-solid ratio dependent leaching tests. Results indicate that, in general, maximum contaminant levels for drinking water, used here as a benchmark for metals concentrations in leachate, were exceeded only at pH values less than 5 or greater than 9. Leaching as a function of increasing liquid-to-solid ratio demonstrated that pH controlled the observed behavior: unamended sediment leached lower concentrations of all elements except for the oxyanion arsenate. The flowable fill material, despite dilution of the sediment and incorporation into a cementitious matrix, leached higher element concentrations except for arsenic due to the high pH of the material. It was also shown that a much more grossly contaminated material (Newtown Creek) had a very similar leaching behavior to the less contaminated Gowanus Canal material. Speciation calculations demonstrated that dissolved organic carbon plays a significant role in the leaching observed from these estuarine sediments and the flowable fill made with the high organic matter content sediments. [Copyright &y& Elsevier]

Availability of test species for estuarine benthic assessment is limited; therefore, a method was developed by the U.S. Environmental Protection Agency for using the dwarf surf clam (Mulinia lateralis) to identify adverse biological effects of bulk estuarine sediments. A multilaboratory evaluation of the draft method resulted in favorable responses from the participants with respect to general testing and handling of the clam. However, availability of good-quality test organisms was limited. An investigation of culture techniques determined that culture vessel topography dramatically influenced survival, because larvae accumulated in bottom depressions. Conditioning of brood stock was enhanced by algae naturally containing both 20:5n-3 and 22:6n-3 fatty acids. Survival of larvae to metamorphosis at 14 d postspawn was greatly increased by maintenance at a lighting of 734 lux with addition of gradually increasing amounts of Isochyris galbana and Chaetoceros calcitrans. Greater than 50% survival of 600 juveniles to testing size by 14 d postmetamorphosis was accomplished by intermittent delivery of algae 12 times per day in a total of 13 L of seawater. By 21 d postmetamorphosis, an additional 27% achieved testable size. As a result of identification of these culture parameters, test bivalves can be readily available to improve predictions of adverse biological effects on benthic communities beyond those presently determined through amphipod exposures. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) contaminates thousands of kilometers of stream in the western United States. At the same time, nitrogen loading to many mountain watersheds is increasing because of atmospheric deposition of nitrate and increased human use. Relatively little is known about nitrogen cycling in acidic, heavy-metal-laden streams; however, it has been reported that one key process, denitrification, is inhibited under low pH conditions. The objective of this research was to investigate the capacity for denitrification in acidified streams. Denitrification potential was assessed in sediments from several Colorado AMD-impacted streams, ranging from pH 2.60 to 4.54, using microcosm incubations with fresh sediment. Added nitrate was immediately reduced to nitrogen gas without a lag period, indicating that denitrification enzymes were expressed and functional in these systems. First-order denitrification potential rate constants varied from 0.046 to 2.964 day−1. The pH of the microcosm water increased between 0.23 and 1.49 pH units during denitrification. Additional microcosm studies were conducted to examine the effects of initial pH, various electron donors, and iron (added as ferrous and ferric iron). Decreasing initial pH decreased denitrification; however, increasing pH had little effect on denitrification rates. The addition of ferric and ferrous iron decreased observed denitrification potential rate constants. The addition of glucose and natural organic matter stimulated denitrification potential. The addition of hydrogen had little effect, however, and denitrification activity in the microcosms decreased after acetate addition. These results suggest that denitrification can occur in AMD streams, and if stimulated within the environment, denitrification might reduce acidity. [ABSTRACT FROM AUTHOR]

Arsenic, a toxic metalloid, is commonly associated with sulfide minerals in anoxic sediments. Here we characterize arsenic(III) retention on sediments from a sulfidic estuarine marsh using a series of sorption experiments, and probe the structure of retained arsenite with X-ray absorption spectroscopy. Although the extent of sorption varied with sampling locations, several adsorption characteristics were apparent. A fraction of arsenite adsorbed over the entire pH range examined, although it was most extensive at pH greater than 7, and conformed to a Langmuir isotherm. Iron sulfide phases were responsible for As partitioning in these sediments. Initially, an FeAsS-like precipitate formed with a structure similar to those reported for As(III) sorbed on iron sulfides, a complex that is highly reactive. Following reaction for 21 d, much of the FeAsS-like precipitate was converted to As2S3. A drop in the redox potential accompanied this conversion, suggesting that the evolution of sulfide and other reduced species stabilizes bound arsenic. Processes discerned in this study reveal the importance of sulfide minerals in As sequestration within anoxic environments. [ABSTRACT FROM AUTHOR]

A transient estuarine turbidity maximum (ETM) was observed in Winyah Bay during field sampling in 1996. The core of this turbidity maximum migrated 8 km seaward of its traditional location at the salt–freshwater interface in response to very high river discharge events in 1996. In response to the semidiurnal tidal cycle, there was a well-defined variation in the suspended sediment concentration within the turbidity maximum zone between ebb and flood tides as a result of differences in tidal velocities. The suspended sediment inventory in the water column during the flood tide was greater than suspended sediment inventory during the ebb tide. During slack water, the water column was characterized by 0.03 kg m−3 sediment concentrations whereas at times of maximum boundary shear stress near the bottom, the water column was highly turbid, indicating that bottom sediments were resuspended by the strong tidal currents typical of the bay. Throughout a tidal cycle, the vertical extension of high suspended sediment concentration in the water column within the ETM was well developed during the flood tide and inhibited during the ebb tide. Internal tidal asymmetry, with well-mixed conditions during the flood tide near the bottom, and with stratification in the water column during the ebb tide, was probably the process responsible for the enhancement of turbulence during the flood tide and inhibition of turbulence during the ebb tide with implications for the ETM. [Copyright &y& Elsevier]

Estuarine sediments from a USEPA Superfund site in coastal Georgia were extensively contaminated with Aroclor 1268, a mixture of highly chlorinated polychlorinated biphenyls used by a former chlor-alkali plant. Batch slurries of contaminated sediment were incubated for 1 yr with amendments of 2,6-dibromobiphenyl (26-BB) and 2,3,4,5,6-pentachlorobiphenyl (23456-CB) under anaerobic, sulfate-reducing conditions and different pH (5.5–7.5). Organic extracts of slurry sub-samples in a time series were analyzed by congener-specific GC–MS. Dechlorination of 23456-CB was pH dependent and occurred via two routes with the sequential loss of (1) meta and para chlorines and (2) para, ortho, and meta chlorines. Quantitative dehalogenation of 26-BB was observed at all pH. Supplementation of nonachlorobiphenyls (as primers) did not induce dechlorination of native Aroclor 1268 nor of the primers themselves. While contaminated estuarine sediments possess microbial consortia with diverse dehalogenating activities, lack of dechlorination of Aroclor 1268 and spiked nonachlorobiphenyl congeners suggests a bioavailability limitation or enzyme–substrate incompatibilies. [Copyright &y& Elsevier]

Investigates spatial distribution of the pesticide, DDT, in sediments from the estuarine rivers of Central Florida. Influence of sediment grain size or texture on DDT contamination; Hazard posed by the contamination on the area's aquatic life.

Integrated ichnologic, sedimentologic, and stratigraphic studies of cores and well logs from Lower Pennsylvanian oil and gas reservoirs (lower Morrow Sandstone, southwest Kansas) allow distinction between fluvio-estuarine and open marine deposits in the Gentzler and Arroyo fields. The fluvio-estuarine facies assemblage is composed of both interfluve and valley-fill deposits, encompassing a variety of depositional environments such as fluvial channel, interfluve paleosol, bay head delta, estuary bay, restricted tidal flat, intertidal channel, and estuary mouth. Deposition in a brackish-water estuarine valley is supported by the presence of a low diversity, opportunistic, impoverished marine ichnofaunal assemblage dominated by infaunal structures, representing an example of a mixed, depauperate Cruziana and Skolithos ichnofacies. Overall distribution of ichnofossils along the estuarine valley was mainly controlled by the salinity gradient, with other parameters, such as oxygenation, substrate and energy, acting at a more local scale. The lower Morrow estuarine system displays the classical tripartite division of wave-dominated estuaries (i.e. seaward-marine sand plug, fine-grained central bay, and sandy landward zone), but tidal action is also recorded. The estuarine valley displays a northwest–southeast trend, draining to the open sea in the southeast. Recognition of valley-fill sandstones in the lower Morrow has implications for reservoir characterization. While the open marine model predicts a “layer-cake” style of facies distribution as a consequence of strandline shoreline progradation, identification of valley-fill sequences points to more compartmentalized reservoirs, due to the heterogeneity created by valley incision and subsequent infill.The open-marine facies assemblage comprises upper, middle, and lower shoreface; offshore transition; offshore; and shelf deposits. In contrast to the estuarine assemblage, open marine ichnofaunas are characterized by a high diversity of biogenic structures representing the activity of a benthic fauna developed under normal salinity conditions. Trace fossil and facies analyses allow environmental subdivision of the shoreface-offshore successions and suggest deposition in a weakly storm-affected nearshore area. An onshore–offshore replacement of the Skolithos ichnofacies by the Cruziana ichnofacies is clearly displayed.The lower Morrow fluvio-estuarine valley was incised during a drop of sea level coincident with the Mississippian–Pennsylvanian transition, but was mostly filled during a subsequent transgression. The transgressive nature of the estuarine infill is further indicated by the upward replacement of depauperate brackish-water trace fossil assemblages by the open-marine Cruziana ichnofacies. Additional stratal surfaces of allostratigraphic significance identified within the estuary include the bayline surface, the tidal ravinement surface, the wave ravinement surface, and a basinwide flooding surface recording inundation of the valley interfluves. A younger sequence boundary within the lower Morrow is also recorded in the Gentzler field at the base of a forced regression shoreface, demarcated by the firmground Glossifungites ichnofacies, indicating a rapid basinward facies migration during a sea-level drop.Trace fossil models derived from the analysis of Mesozoic and Cenozoic reservoirs are generally applicable to the study of these late Paleozoic reservoirs. Pennsylvanian brackish-water facies differ ichnologically from their post-Paleozoic counterparts, however, in that they have: (1) lower trace fossil diversity, (2) lower degree of bioturbation, (3) scarcity of crustacean burrows, (4) absence of firmground suites, and (5) absence of ichnotaxa displaying specific architectures designed to protect the tracemaker from salinity fluctuations. Morrow open-marine ichnofaunas closely resemble their post-Paleozoic equivalents. [Copyright &y& Elsevier]

Evaluates the geochemical and Sr isotope analysis of the fine fraction of estuarine detrital sediments in San Francisco Bay in California. Characteristics of the sediments suspended in drainage basins; Reduction of sediment inflows with reservoir building; Variation of the fraction of suspended sediment.

Examines the decadal trends of silver and lead contamination in San Francisco Bay, California. Decline of lead concentration in estuarine system; Factors controlling concentrations of silver and lead surface waters; Internal recycling of lead between the surface sediments and water column in the Bay.

Examines coastal wetland sediments at the Sixes River estuary in Oregon. Record of gradual and abrupt relative sea-level changes; Tectonic subsidence causing soil burial; Coincidence of coseismic subsidence and tsunami inundation.

Presents a 23-year time series of environmental change from a San Francisco Bay mudflat located one kilometer from the discharge of a suburban domestic sewage treatment plant. Use of surface sediment and bioindicator Macoma balthica and metals loading data to establish links between discharge, bioaccumulation, and effects.

The article discusses a study on degraded sediment quality in U.S. estuaries and their ecological implications. It states that toxic substances concentrating in sediments of estuaries can be harmful for the living organisms of estuaries, and mentions review of data from toxicity tests and analysis of benthic community in the study. It notes findings of acute amphipod bioassays.

Investigates the static-die away of the nonylphenol ethoxylate (NPE) surfactant using estuarine water samples collected at four stations in Tampa Bay, Florida. Observation of the concentration of five NPE intermediate degradation products and total surfactant; Intermediates detected; Sequence of degradation and intermediate accumulation and decay.

Investigates the speciation and cycling of mercury in Lavaca Bay, Texas estuarine sediments. Collection of depth profiles of total mercury and monomethylmercury at 15 sites; Illustration of the dynamic nature of mercury cycle in the upper few centimeters of the estuarine sediment; Variation in mercury speciation of the upper one centimeter of sediment.

Examines evidence of pedogenic processes in subaqueous soils under a submersed environment from Sinepuxent Bay, Maryland. Constituents of pedogenic processes including addition of biogenic calcium carbonate; Application of mapping protocol based on soil-landscape paradigm; Function of subaqueous soil resource inventories to estuarine areas.

Presents a study on the Sixes River estuary, located along south coastal Oregon, specifically on Cascadian subduction zone earthquakes. Details on study conducted; methodology used during study; Findings of study; Discussion on findings.

Examines the sorption of four chlorinated guaiacols, or o-methoxyphenols, using four estuarine sediments from the York River, Virginia. Effects of humic acids and total organic carbon contents; PH effects; Derivation of sorption coefficients.