Sediment Resuspension Research Articles

Machine Learning Assessment of Dredging Impacts on the Phytoplankton Community on the Brazilian Equatorial Margin: A Multivariate Analysis.

Dredging in estuarine systems significantly impacts phytoplankton communities, with suspended particulate matter (SPM) and dissolved aluminum (Al) serving as indicators of disturbance intensity. This study assessed the effects of dredging in the São Marcos Estuarine Complex (SMEC), Brazil, over three distinct events (2015, 2017, 2020), involving varying sediment volumes and climatic influences. Prolonged dredging operations and increased sediment volumes led to a pronounced 43.81% reduction in species diversity, with diatoms and dinoflagellates being the most affected. Climatic variability, particularly El Niño events, exacerbated environmental dispersion, amplifying the complexity of ecosystem responses. Despite these losses, certain centric diatoms persisted, reflecting resilience mechanisms within this tropical macrotidal estuary. Machine learning approaches, specifically Random Forest (RF) models, revealed SPM and dissolved Al as critical stressors influencing species diversity. Additionally, river discharge and salinity were identified as key predictors of phytoplankton biomass. Generalized Additive Models (GAMs) confirmed that chlorophyll-a concentrations responded negatively to elevated SPM and Al levels but were less sensitive to dredging than diversity metrics. This study provides novel insights into the compounded effects of dredging and climatic variability, emphasizing the utility of RF and GAM models for predicting ecosystem responses and guiding management strategies. Recommendations include optimizing operations to reduce biodiversity impacts, minimizing sediment resuspension, and integrating predictive tools to mitigate long-term disturbances. These findings offer a data-driven framework for sustainable dredging in sensitive estuarine ecosystems.

Intensification of sediment flux by wind-induced residual currents in a heavily contaminated, micro-tidal bay.

Wind-induced currents are the major forces responsible for sediment resuspension and transport in micro-tidal bays. To reveal the impact of wind-induced residual currents on the sediment flux, in-situ measurements using acoustic Doppler current profilers (ADCPs) were conducted at two mooring stations in a heavily contaminated, micro-tidal Onsan Bay. During the mooring period, the suspended sediments at both stations were transported seaward (landward) at the surface (bottom) layer mainly through the residual currents (mean-flow flux Fmean: > 70% of the total flux). Under northerly winds, the landward bottom residual currents at both stations strengthened, resulting in the "intensification" of landward Fmean. This suggests that the northerly winds might be a primary factor intensifying the landward sediment fluxes, potentially resulting in the increased sediment deposition into the bay. The findings provide insights into managing sedimentation in contaminated coastal bays and highlight the importance of wind effects on sediment transport in micro-tidal bays.

Synchronous control of nitrogen and phosphorus release from sediments in shallow lakes under wind disturbance by modified zeolite and Ca/Al-based sludge combination

To inhibit eutrophication caused by endogenous pollutants release, the experiment explored the efficiency and mechanism of the synchronous control of nitrogen (N) and phosphorus (P) release from sediments in shallow lakes under wind disturbance by modified Ca/Al-based sludge (MS) and modified zeolite (MZ). High-temperature calcination and NaCl impregnation increased the pore volume of MS and Na+ content of MZ, and the adsorption capacity of MS for PO43−-P and MZ for NH4+-N was as high as 42.01 and 20.28 mg g−1. The results of a 90-day incubation experiment showed that the addition of MS and MZ increased the abundance of Thauera, Nitrospira, Denitratisoma, and Clostridium, while decreasing the proportion of Proteus Hauser and Saccharimonadales, thereby reducing the active N and P contents in sediments through microbial transformation. At the same time, the efficient adsorption performance of the MS and MZ resulted in a significant decrease in pollutants in the interstitial water and sediments. In addition, sediment resuspension caused by wind disturbance increased the contact between sediments and remediation agents, resulting in the action depth of covering materials exceeding 100 mm. Compared to adding MS or MZ alone, the combination of the two (MSZG) could synchronously, efficiently, and stably inhibit N and P release. Under the coupling effects of physical interception, physicochemical adsorption, and biotransformation, the average TN, NH4+-N, TP, and PO43−-P in the overlying water of the MSZG decreased by 72.13%, 88.92%, 69.28%, and 81.26%, respectively, compared to Control, which satisfying the Class III standard for surface water. Therefore, this study could provide reference for controlling endogenous release, improving eutrophication in shallow lakes under wind disturbance, and recycling residual sludge from sewage plants.

Dredging and sediment discharge in a river with floodplain. Physicochemical and microbiological effects in Paraná river.

Alterations caused by human activities in the environment, such as dredging, modify the physicochemical conditions and affect the habitat. Maintenance dredging that allows large vessels access to inland ports is a recurring disruptive action. The study aimed to evaluate, during a maintenance dredging operation in a port area of the Paraná River, the modifications in the structure of the river, the presence of contaminants and bacterial organisms. The effects caused during the operation of a suction dredge in a South America river under two temporal conditions were analyzed: i) the short and medium-term effects on the physicochemical variables, and ii) the immediate effects on the physicochemical variables and the abundance of bacterioplankton. The variables measured in sediment and water samples were limnological parameters (e.g. conductivity, pH, dissolved oxygen, among others), heavy metal concentration, presence of biocides, hydrocarbon molecules, nutrients, sediment granulometry, Escherichia coli, Enterococcus, total coliforms, and heterotrophic bacteria. Some physicochemical variables increased in the water column immediately after the water mass passed through the operating dredge, including sediment resuspension. The parameter changes were transient, as there were no significant increases in the variables downstream of the dredge during dredging and discharge operations or after dredging work. Some metal concentrations increased in the sediment and water column. Bacteria increased during dredging and more after rainfall events. Then, at the end of the dredging, the bacteria concentrations decreased to previous values. The possible effects of dredging disturbance were of the same order or less than those of natural ones, i.e. rainfall. Sixty days after the dredging work was completed, the system was back to normal both in the dredged and discharge areas.

Recovery and expansion of rhodoliths beds and Laminaria rodriguezii forests after bottom trawl ban

AbstractRhodolith beds and Laminaria rodriguezii forests constitute marine habitats of high conservation value. In the Menorca Channel (Balearic Islands, Western Mediterranean) rhodolith beds predominate in the sedimentary bottoms of the continental shelf and in some areas, these bottoms present an erect stratum with L. rodriguezii. Bottom trawling has negative impacts on rhodolith beds and, specially, on L. rodriguezii forests due to the direct effects of extraction and mechanical destruction and indirect effects related to sediment resuspension and posterior settlement that promotes burial. In this work we compare the distribution of rhodolith beds and L. rodriguezii forests in the Site of Community Importance (SCI) of the Menorca Channel before and after 2016, when a Fishing Protection Zone (FPZ) banning trawling was established. Since the implementation of the FPZ the extension of both rhodolith beds and L. rodriguezii forests have shown an increase of 6% and 54% respectively, and biomass of rhodolith-forming species and L. rodriguezii showed higher values than before the FPZ. The improvement of these habitats in the SCI Menorca Channel evidences that the bottom trawl ban is an effective measure for the conservation and restoration of benthic communities and habitats. This is particularly relevant in the case of rhodolith beds and L. rodriguezii forests due to their ecological importance and their role as essential fish habitats that improve the sustainability of marine living resources.

Immobilization of phosphorus (P) migrated from sediment increasing algal-available P pool in P-inactivating material.

Use of phosphorus (P)-inactivating material to immobilize P released from sediment, typically under anoxic condition, is a method often considered to reduce lake internal P loading for eutrophication control. This study found that immobilizing the released P from sediment induced accumulation of algal-available P (NaHCO3 and Fe oxide paper strip extractable P) in P-inactivating material which was even higher than those in raw sediment at initial stage (by 29.7% and 85.7%), although algal-available P substantially decreased in sediment after addition of the material and in the separated sediment from the mixtures. Given the possibility of exposing P-inactivating material to phytoplankton systems in overlying water typically during sediment resuspension, the accumulation suggested the potential of the resuspended material changing as P source for phytoplankton growth, increasing the uncertainties of sediment P immobilization method. Future work should focus more on the resuspension characteristics of P-inactivating material and on enhancing the capability of immobilizing algal-available P by the materials during internal P pollution control, especially in shallow lake.

Sediment Ballet: Unveiling the Dynamics of Metal Bioavailability in Sediments Following Resuspension and Reequilibration.

Assessing the risk of metal-contaminated sediments under disturbed conditions is challenging due to the lack of methods that capture instant changes in metal bioavailability. Existing approaches provide inadequate understandings of the processes regulating metal bioavailability under nonequilibrium conditions. Experiments were conducted to improve our understanding of the metal bioavailability dynamics induced by sediment resuspension and subsequent redeposition (reequilibration). An isotopically modified bioassay, a novel stable isotope tracing technique, was used to measure metal bioavailability (assimilation rates) to clams within short time windows. Changes in metal partitioning were characterized by porewater analysis using in situ extraction and the diffusive gradients in thin-films technique. Results showed that sediment resuspension released metals into porewater, while reequilibration scavenged metals from the porewater. The assimilation rates of Ni, Cu, and Pb increased with the resuspension time, aligning with increasing porewater concentrations. Unexpectedly, during reequilibration, the metal assimilation rates did not decrease. The discrepancies between bioavailability to the clam and porewater extrapolations may be due to differing sustained conditions of metals in sediments. Overall, this study unveils the metal bioavailability dynamics in nonequilibrium sediments, which could not be accurately predicted relying solely on porewater analysis. Incorporating rapid bioassays to determine bioavailability offers a valuable tool for robust ecological risk assessment.

A high-resolution 3D sediment-dynamics model of a morphologically complex mesotidal estuarine river system (New Zealand): insights from model calibration and validation

Land use change and the associated change in sediment runoff to the receiving environment is a topic of concern for estuarine and coastal governing agencies around the world. Fine sediments can enter the receiving environment and have a plethora of potential negative impacts (e.g., ecological, and recreational) and present no real opportunities or positive impacts. In the present study, a Delft3D numerical model is presented. The model has been calibrated considering water levels, currents, temperature, salinity, and Suspended Sediment Concentrations (SSC). Delft3D-Wave was also coupled to the hydrodynamic model to investigate the role of wave related fine sediment resuspension due to wave bed shear stresses. The extent of this model covered the Wairoa River and estuary, just south of Auckland, New Zealand. The motivation for this study was to produce a method that could link the upstream SSC contribution to the subsequent distribution in the receiving environment. From there it can readily be used as input to a regional scale model to investigate and understand the fate of sediments in the Hauraki Strait. As part of an ongoing research programme, the present study formed part of an extensive measurement campaign. Measurement instruments and results are presented alongside numerical model sensitivity analyses. The model performance is discussed, and the physical dynamics are described via extensive tables and summarising plots.

Fractionation and tidal characteristics of per- and polyfluoroalkyl substances in the estuarine maximum turbidity zone.

Complex tidal processes and suspended particulate matter (SPM) behavior influence the land-sea transport of terrestrial contaminants in estuaries. Contaminants are generally trapped within the estuarine maximum turbidity zone (MTZ), where SPM concentrations peak, misleading flux estimation. Here, we conducted high-resolution continuous sampling over two tidal cycles within the MTZ of a semidiurnal estuary. Tidal variations of per- and polyfluoroalkyl substances (PFAS), a class of persistent organic pollutants, were analyzed in dissolved water and size-fractionated SPM. Results showed that variations in dissolved PFAS may related to the mixing of upstream and downstream. The predominant size range for SPM was found in 1-31μm (75%, mainly 10-31μm), but the PFAS tended to be sorbed by 0.22-1μm (60%) and>31μm (37%) fractions. Except during periods of sediment resuspension when particulate PFAS concentration decreased, the PFAS concentration in the 1-31μm increased during flood tides and decreased during ebb tides, which may not be related to organic carbon/elemental carbon levels. The hourly dynamic flux of dissolved-phase and particulate-phase PFAS transport to the sea in the MTZ was calculated by combining it with a hydrodynamic model. This study first highlights the size-fractionated PFAS transport under tidal influences and provides hourly flux estimation with a hydrodynamic model.

Depth drive shifts in the fish and benthic assemblages of the South American Reef System

The low-latitude habitats of the South American reef system have a high endemism and represent important stepping-stones due to the connectivity with Amazon and Caribbean reefs. We provide the first seabed mapping, and analyze the benthic cover and fish assemblages of these extreme reefs. Fleshy macroalgae (2—66% of cover), algal turfs (0—47%), and sponges (3—25%) are the dominant benthic groups. The main reef builders are crustose coralline algae (2—23%) and only four coral species (0 to 18%), mainly the weedy Siderastrea stellata. Cluster analysis distinguished two groups. The first group includes the shallowest reefs (~ 17 m deep) where fleshy macroalgae are abundant together with higher siltation on the reefs (~ 31% covered by sediments). The second group, by contrast, includes the deeper reefs (22.5—27 m), which have much higher algal turf cover, and the lowest sediment cover (4%). The deeper reefs also have the highest cover of corals (18%) and sponges (25%). We recorded a total of 63 fish species, with the deep reefs being the richest. Analysis indicated that the composition of the benthos was considerably more homogeneous across the study area than the composition of fish assemblages, which had a higher turnover of species among reefs. Moreover, we identified the depth of the reef as a variable structuring the benthic assemblages. The fish assemblage is influenced, in turn, by the benthos. Overall, the seabed mapping revealed the existence of a single reef system with high spatial heterogeneity. Our results provide new insights into the structure of these extreme reefs that have evolved under the influence of sediment resuspension, moderate turbidity, and are warmer than other West Atlantic reefs located at middle- and high-latitudes.

Tide-Induced Bottom Current and Sediment Resuspension in Halifax Harbour

Tide-Induced Bottom Current and Sediment Resuspension in Halifax Harbour

Direct in situ evidence of tidal roles in the formation of contourite depositional systems

Tidal currents are ubiquitous in the oceans, but the role of these currents in contributing to form contourite depositional systems is poorly understood. Here we evaluated the significance of these currents in the formation and shaping of the contourite depositional systems. We examined in situ current data, spanning three months to one year, from four contourite sites at the exit of the Strait of Gibraltar, the northern North Atlantic Ocean, the Pacific margin of the Antarctic Peninsula, and the Lake Champlain. These current data indicate that tidal currents contribute to varying degrees to the formation of contourite erosional and depositional features, depending on the relative strengths of local tidal currents and background water mass circulation. Tidal currents enhance sediment resuspension in moats and channels, and encourage deposition on drifts, thereby promoting the development of contourite depositional systems. Baroclinic (internal) tidal currents are likely the dominant agent. Our findings indicate that tidal influences, especially those of internal tides, need to be considered in studies of the generation and evolution of contourite depositional systems.

Simulating potential impacts of bottom trawling on the biological carbon pump: a case study in the Benguela Upwelling System

Bottom-trawl fishery is known to cause major disturbances to marine sediments as the dragging of trawl gears across the seabed fosters sediment resuspension, which can lead to organic particle remineralization and release of benthic CO2 and nutrients into bottom waters. However, its effects on carbon cycling and biological productivity, especially in highly productive regions like the Benguela Upwelling System (BUS), are less well studied. Here, we simulated carbon (C) and nutrient pathways from the trawled coastal seabed to overlying water masses that are being upwelled into the sunlit surface within the BUS, using shipboard data on sea surface and water column characteristics and published benthic CO2 emission estimates from bottom-trawled sediments. The latter reports 4.35 and 0.64 Tg C year-1 to be released from the seabed into upwelling source waters after bottom trawling in the northern (NBUS) and southern (SBUS) subsystems, respectively. Based on these values, we estimated a corresponding nitrate (N) input of 1.39 and 0.47 µmol kg-1 year-1, enhancing source water nitrate concentrations by ~5% and ~2%. Trawl-induced nitrate input into the sunlit surface could support a new production of 3.14 and 0.47 Tg C year-1 in the NBUS and SBUS, respectively, recapturing only 2/3 of CO2 released after bottom trawling into biomass, mainly due to differences in stoichiometric C:N ratios between the sediment (~9) and surface biomass (Redfield, 6.6). The remaining benthic CO2 can thereby lead to an increase in surface CO2 concentration and its partial pressure (pCO2), impeding CO2 uptake of the biological carbon pump in the BUS by 1.3 Tg C year-1, of which 1 Tg C year-1 is emitted to the atmosphere across the northern subsystem. Our results demonstrate the extent to which bottom trawling may affect the CO2 storage potential of coastal sediments on a basin-wide level, highlighting the need to better resolve small-scale sediment characteristics and C:N ratios to refine trawl-induced benthic carbon and nutrient effluxes within the BUS.

The dual role of coastal mangroves: Sinks and sources of microplastics in rapidly urbanizing areas

Mangrove ecosystems are vital for coastal protection, biodiversity, and pollution interception, yet their interactions with microplastics in rapidly urbanizing regions remain underexplored. This study investigated the microplastic dynamics in the Maozhou River and Dasha River, along with the coastal Xiwan Mangrove Park in the Pearl River Estuary, the second largest estuary in China. Samples were collected from mangrove and surrounding areas, identifying microplastics using Fourier-transform infrared spectroscopy (FTIR) and Laser Direct Infrared (LDIR) techniques. Microplastic concentrations ranged from 245.8 to 1562.4 n/m³ in water and 374.3 to 7475.3 n/kg in sediments. The Maozhou River exhibited consistent microplastic levels across varying hydrological conditions, while the Dasha River and Xiwan Mangrove showed greater sensitivity to water flow changes influenced by urban land use. During high-flow periods, urban river microplastic concentrations decreased due to dilution, whereas mangrove areas experienced elevated levels in water from urban runoff, upstream retention, and sediment resuspension, suggesting a potential for outward release. Weaker water dynamics led to increased microplastic accumulation in mangrove sediments. The distribution of microplastic types was influenced by multiple urban pollution sources, with synthetic rubbers linked to urban transportation comprising over 50 % of some samples, peaking at 79 %. These findings underscore the dual role of mangroves as microplastic sinks and potential sources, highlighting the significant impact of hydrological conditions on their function. This study offers new insights into microplastic pollution in urban mangrove ecosystems and emphasizes the urgent need for improved management strategies in coastal areas facing rapid urbanization.

Along-Slope Bottom Current and Sediment Resuspension and Transport Induced by Internal Tides on a Continental Slope

Abstract Moored observations on a critical continental slope in the northeastern South China Sea (SCS) are presented to reveal along-slope bottom current and sediment resuspension and transport caused by internal tides. During spring tides, the bottom-intensified diurnal internal tides were observed, and their breaking generated an along-slope bottom current toward the southwest direction, with a clear ∼14-day spring–neap cycle and a maximum low-frequency velocity exceeding 0.25 m s−1. The diurnal internal tides and along-slope bottom currents showed the same seasonal variations. There were larger near-bottom along-slope velocities in winter (∼9.0 cm s−1) and summer (∼8.9 cm s−1) than in spring (6.3 cm s−1) and autumn (7.4 cm s−1). The previous theory based on radiation stress caused by wave breaking is used to reproduce the observed along-slope bottom current velocity. Strong bottom flows caused by internal tides on the critical slope inhibit deposition of fine-grained sediments and may erode bottom coarse-grained sediments, leading to the generation of near-bottom nepheloid layer with a thickness H > 130 m, as demonstrated by the fact that seafloor sediments on the critical slope are dominated by coarse-grained sediments (sands). The suspended sediments can be southwest transported by the persistent along-slope bottom current generated by internal tide breaking. It was estimated that approximately three million tons of sediments during the observation were carried along the slope to the south of the SCS. Our observations suggest that internal tide-induced sediment resuspension/deposition and along-slope transport could be important for seafloor sediment distribution of the SCS.

Internal tidal dynamics and associated processes at highly supercritical slopes in Banda Sea: Lessons from the oceanic island of Ambon, eastern Indonesia

Interactions between the deep sea and steep-sloping oceanic islands generate physical processes with potential impacts on sediment resuspension and ocean productivity. While studies have been conducted in the open oceans, those focusing on oceanic islands of the deep Banda Sea in eastern Indonesia are lacking. Here, we present the first observational evidence of vertical mechanisms (i.e. internal tidal reflection, internal hydraulic jumps) at the highly supercritical slope in outer Ambon Bay (OAB) in Ambon Island – an oceanic island in the Banda Sea. A 23-h CTD yoyo experiment combined with ADCP measurements conducted during spring flood and ebb tides demonstrated tidally-varying vertical temperature, salinity and density profiles. During spring flood tide, incoming internal tides were reflected by OAB's highly supercritical slope back to the deep sea with isopycnals and isotherms showing sharp downward plunges (downward vertical velocity = 6.5–8.3 × 10−3 m/s), and the internal tidal amplitude reaching 90–110 m. The reflection during flood tide caused seaward overturning flow at deeper depths despite the prevailing landward flow at the upper layers. During spring ebb tide, internal hydraulic jumps (upward vertical velocity = 6.1–6.48 × 10−3 m/s) occurred to rebound the downward plunges of isopycnals and isotherms as flood tide relaxed with the observed amplitude of internal tides of 90 m. We also observed weakened seaward ebb flow during the isothermal uplifting (when hydraulic jumps occurred), and subsequent intensified landward flow at the end of spring ebb tide indicating strong upslope flow when isotherms reached the maximum shoaling depths. Taken together, the observed vertical mechanisms indicate the conservation of energy at the highly supercritical slope of OAB evident by the comparable vertical velocities. An embedded turbidity-chlorophyll profiler in the CTD reveals that internal tidal activities at the highly supercritical slopes OAB may induce bottom nepheloid layers, and influence ocean productivity by regulating the vertical distribution of phytoplankton biomass.

Measurement of Thalassia testudinum mediation of sediment resuspension and settling using traps and plates in a subtropical estuary, Estero Bay, Florida, USA

Measurement of <i>Thalassia testudinum</i> mediation of sediment resuspension and settling using traps and plates in a subtropical estuary, Estero Bay, Florida, USA

Modeling the transport and mixing of suspended sediment in ecological flows with submerged vegetation: A random displacement model-based analysis

Aquatic vegetation in rivers influences the flow structure, impacting the sediment transport in the river and further changing the ecosystem and geomorphologic evolution of the river. In this paper, an improved random displacement model (RDM) is proposed to investigate the concentration of suspended sediment (CSS) in flows with flexible submerged vegetation. Considering the effect of sediment resuspension on sediment transport, a probability model of sediment resuspension is embedded into the RDM so that the simulation process is more consistent with the natural cases. For the streamwise development of flow with flexible submerged vegetation, the flow is divided into a flow adjustment region and a fully developed region in the longitudinal direction. The vertical distributions of the flow velocity and turbulence diffusion coefficient were analyzed in these two regions, and they were incorporated into the RDM to simulate the along-flow development of the CSS. The simulated concentrations were compared with the experimental data. The mean relative errors (MREs) were below 15%, the root mean square errors (RMSEs) were below 0.20, and the Nash–Sutcliffe efficiencies (NSEs) ranged from 0.71 to 0.99, indicating that the improved RDM is plausible and reliable. In addition, the along-flow distribution of the sediment transport rate (STR) was analyzed. The rate exhibited a decreasing trend during the flow adjustment region and tended to stabilize during the fully developed region. This study provides a new way of thinking for research on sediment transport in rivers with aquatic vegetation, which is of great significance for achieving the sustainable development of river ecosystems and the optimal design of river channels.

Application of time series and multivariate statistical models for water quality assessment and pollution source apportionment in an Urban River, New Jersey, USA

Water quality monitoring reveals changing trends in the environmental condition of aquatic systems, elucidates the prevailing factors impacting a water body, and facilitates science-backed policymaking. A 2020 hiatus in water quality data tracking in the Lower Passaic River (LPR), New Jersey, has created a 5-year information gap. To gain insight into the LPR water quality status during this lag period and ahead, water quality indices computed with 16-year historical data available for 12 physical, chemical, nutrient, and microbiological parameters were used to predict water quality between 2020 and 2025 using seasonal autoregressive moving average (ARIMA) models. Average water quality ranged from good to very poor (34 ≤ µWQI ≤ 95), with noticeable spatial and seasonal variations detected in the historical and predicted data. Pollution source tracking with the positive matrix factorization (PMF) model yielded significant R2 values (0.9 < R2 ≤ 1) for the input parameters and revealed four major LPR pollution factors, i.e., combined sewer systems, surface runoff, tide-influenced sediment resuspension, and industrial wastewater with pollution contribution rates of 23–30.2% in the upstream and downstream study areas. Significant correlation of toxic metals, nutrients, and sewage indicators suggest similarities in their sources.Graphical

Proximity to inlet channel drives spatial variation in sediment carbon across a lagoonal seagrass meadow

Seagrass meadows can be sinks for organic carbon, but estimates of global organic carbon stocks are complicated by substantial spatial variability in organic carbon burial observed within meadows. To improve estimates of organic carbon burial in seagrass meadows, it is necessary to understand the causes of the spatial heterogeneity. This study investigated relationships between spatial patterns in sediment organic carbon storage and accretion rates, hydrodynamics, and proximity to sources of organic carbon in a current-dominated Zostera marina Linnaeus meadow in Menemsha Pond, Massachusetts, USA. Sediment and velocity measurements were conducted at six stations along a 150-m transect across the meadow oriented perpendicular to the pond's unvegetated inlet channel. The meadow's edge near the channel had higher organic carbon than the channel as well as the highest organic carbon within the meadow. With increasing distance from the meadow's edge, all of the following decreased: sediment organic and total carbon, sediment accretion rates, peak tidal velocity, sediment trap mass deposition rate, and the relative contribution of non-seagrass sources to sediment organic carbon. Lower tidal velocities farther from the inlet channel reduced sediment resuspension, consistent with lower sediment trap mass deposition, which should enhance organic carbon content and organic carbon accretion rates. However, the opposite trend of decreasing organic carbon content (>50 % across the transect) and decreasing accretion rates with distance from channel was observed. This suggested that the local hydrodynamic intensity was not controlling organic carbon accretion, which was instead constrained by supply limitation and controlled by the lagoon-scale flow circulation.