In the absence of horizontal migration, salt marshes must build vertical elevation to persist under sea level rise by building soil through primary production and inorganic sediment deposition. Here we examine a phenomenon observed in a high salinity salt marsh estuary whereby leaf-surface coatings form on Spartina alterniflora (aka Sporobolus alterniflorus) leaves and we investigate whether these coatings can inhibit photosynthesis. Using eddy covariance observations of carbon dioxide fluxes, chamber measurements of leaf level photosynthesis, and measurements of leaf and canopy phenology, we found that: during rain-free periods, leaf and canopy greenness declined as coatings developed, and rainfall rapidly rinsed leaves in proportion to rain amount; daily canopy light-use efficiency (LUE) was jointly controlled by clearness index, canopy greenness, and creek salinity, with the best-supported model including an interaction between clearness index and seasonal greenness, indicating that the positive greenness-LUE relationship was strongest under cloudier, more diffuse conditions; removing coatings increased leaf-level initial quantum yield by about 20

Blackwater rivers are named due to their exceptionally high concentrations of chromophoric dissolved organic matter (CDOM). They are the predominant lotic ecosystem in the United States Southeastern Coastal Plain, a region experiencing some of the nation's highest rates of development. This study assessed variability in DOM concentration and composition across forested to urbanized blackwater systems in coastal South Carolina, U.S. Dissolved organic carbon and nutrient concentrations as well as absorbance and fluorescence optical properties reveal that urban sites have lower concentrations, elemental ratios, and less complex DOM. In contrast, forested blackwater sites have concentrations an order of magnitude higher, elevated elemental ratios, and molecular size dominated by refractory terrestrial-like DOM. Urban blackwater rivers were observed to have DOM concentrations and composition more similar to brown water systems than rural blackwater systems. These findings suggest that the urbanization of blackwater ecosystems results in lower concentrations and the export of simpler, more labile DOM, potentially lowering dissolved oxygen concentrations, increasing atmospheric carbon emissions and other negative impacts. To protect blackwater systems, baseline DOM concentrations and composition must be established to decipher impacts on water quality due to naturally occurring versus anthropogenic activities and to properly assign classifications to these diverse systems across the U.S.

Turbidity, quantified in turbidity units (nephelometric or formazin), is a common and valid measure of water quality related to transparency. A transparency tube (TT) is an economical tool developed to estimate water clarity as an alternative to the Secchi disk, but it is also frequently used to estimate turbidity. Although the relationship between TT measures and turbidity is well characterized for freshwater river and lake systems, this relationship has not been tested for estuarine waters. The objective of the current study was to empirically determine the TT–turbidity relationship for estuarine waters in coastal South Carolina (SC) and compare these results with the traditional freshwater system conversions. We obtained 107 measurements of TT depth, turbidity, total suspended solids, colored dissolved organic matter absorbance, Secchi depth, and chlorophyll a at 22 estuarine locations in SC over a 1‐year period. Linear regressions provide conversion equations that can be applied to SC estuarine waters. The TT–turbidity relationship for estuaries was compared with freshwater systems. Our results suggest that the slope of the relationship differs between systems (−1.11 vs. −1.41), resulting in different turbidity estimates for TT measurements for estuarine vs. inland waters. We propose a combined conversion table incorporating estuarine and freshwater (riverine and lacustrine) systems. A TT–turbidity conversion for coastal SC and similar estuarine waters significantly benefits current water quality programs and citizen science groups by producing more accurate turbidity estimates for screening and routine monitoring efforts.

Stormwater practices are mainly built to reduce flooding, but recent studies showed they could also be an amenity to residential developments. The literature shows conflicting results on the property value effects of stormwater practices. When not properly maintained and deemed less desirable, they could serve as a disamenity to surrounding property owners. To understand how residential wet detention ponds affect the property values of single-family homes, we used a hedonic price method to analyze the real estate data of coastal districts of Horry County in South Carolina. Results showed that adjacency to a stormwater pond generates a premium for single-family homes, although homeowners pay a lower premium when the pond is constructed. Also, newly built homes, particularly presold or less than 2 years old and bought by first owners, command higher prices when near a residential pond. The findings of this study highlight the importance of optimizing stormwater pond designs that deliver the highest benefit to the community.

The Caribbean region is experiencing seasonal inundation of the shoreline by large mats of pelagic Sargassum spp. (Sargassum) leading to novel impacts to ecological communities. Where Sargassum becomes trapped along the shoreline, leachates turn the water a brown color, coined Sargassum Brown Tide (Sbt). We conducted monthly sampling at six sites along the offshore mangrove keys of Jobos Bay, PR between April 2022 to July 2023 to collect temperature, pH, salinity, dissolved oxygen, total nitrogen (TN), total phosphorus (TP), chlorophyll a (chl a), total suspended solids (TSS), and volatile suspended solids (VSS) at nearshore, midshore, and offshore zones along transects running perpendicular to the shoreline. We also collected data on submerged aquatic vegetation (SAV) community dynamics along transects at each site. We found significantly higher chl a and lower dissolved oxygen concentrations within the nearshore zone during Sbt events but the differences did not extend out to the midshore and offshore zones. Total suspended solids were also higher at nearshore zones compared to offshore zones when a Sbt event occurred. In addition, sites that experienced Sbt had higher turbidity and lower pH. Total percent cover of SAV was different between sites impacted by Sbt and control sites depending on transect zone, with higher SAV percent cover for control sites within the 5 m zone and often within the 15 m zone. Our data suggest that Sbt has significant impacts to nearshore water quality, chl a, and SAV percent cover; however, most impacts are not seen beyond 45 m in well flushed systems.

Accompanying climate change and sea level rise, tidal marsh mortality in coastal wetlands has been globally observed that urges the documentation of high-resolution, 3D marsh inventory to assist resilience planning. Drone Lidar has proven useful in extracting the fine-scale bare earth terrain and canopy height. Beyond that, this study performed marsh biomass mapping from drone Lidar point cloud in a S. alterniflora-dominated estuary on the Southeast U.S. coast. Three point classes (ground, low-veg, and high-veg) were classified via point cloud deep learning. Considering only vegetation points in the vertical profile, a profile area-weighted height (HPA) was extracted at a grid size of 50 cm × 50 cm. Vegetation point densities were also extracted at each grid. Adopting the plant-level allometric equations of stem biomass from long-term S. alterniflora surveys, a Lidar biomass index (Lidar_BI) was built to represent the relative quantity of marsh biomass in a range of [0, 1] across the estuary. Compared with the clipped dry biomass samples, it achieved a comparable and slightly better performance (R2 = 0.5) than the commonly applied spectral index approaches (R2 = 0.4) in the same marsh field. This study indicates the feasibility of the drone Lidar point cloud for marsh biomass mapping. More advantageously, the drone Lidar approach yields information on plant community architecture, such as canopy height and plant density distributions, which are key factors in evaluating marsh habitat and its ecological services.

Identifying drivers of the spatial distribution of organisms is a key aim of ecology. Salt marsh ecosystems can exhibit extreme gradients in abiotic conditions, including orders of magnitude differences in physical conditions across the marsh platform, which may contribute to the spatial distributions of organisms found in marshes. Small-bodied consumers, such as crabs, have been identified as key residents of salt marshes, with strong impacts on salt marsh persistence and stability at local scales. However, due to a lack of consensus regarding crab impacts across larger biogeographic scales, continued investigation into the factors driving crab community spatiotemporal dynamics is needed. We used an observational approach to investigate the small-scale spatial patterns and environmental correlates of marsh crab abundance, burrowing activity, and community composition in a representative southeastern US salt marsh. We documented contrasting trends in crab abundance and burrowing activity across the marsh platform elevation gradient, with abundance increasing and burrow density decreasing from the creek bank to forest edge. Crab diversity generally increased with distance from tidal creeks, though the effect of marsh zone on crab diversity was site-specific. Finally, we demonstrated elevation as the key environmental predictor of marsh crab abundance, burrowing activity, and community diversity and identified specific elevations that serve as breakpoints in those metrics. Our results contribute to reconciling differences between small-scale manipulative experiments and large-scale biogeographic sampling of these ecosystem engineering salt marsh residents.

Dissolved oxygen (DO) impairment within coastal waters is widespread and rising temperatures may exacerbate low DO levels by enhancing organic matter (OM) degradation. Here, the temperature sensitivity of OM degradation was investigated as DO decay rates determined during standard five-day biochemical oxygen demand (BOD) measurements conducted under different incubation temperatures. Sampling was conducted in the Waccamaw River watershed, South Carolina, a blackwater river with extensive forested wetland that also receives drainage from stormwater detention ponds associated with coastal development, thus providing different sources of contrasting OM composition. Temperature sensitivities were measured as Q10 temperature coefficients, which define how DO decay rates change with 10 degrees of warming. The average Q10 value for the wetland sites (2.14 ± 0.41) was significantly greater (p < 0.05) than those measured in either the River (1.49 ± 0.36) or stormwater ponds (1.41 ± 0.21). Furthermore, using Intergovernmental Panel on Climate Change intermediate-to-very high temperature estimates for 2100 of +2.7 – 4.4°C, average predicted increases in DO decay rates for wetlands (~22-39%) are more than double the River (~11-18%) and stormwater pond rates (~9-16%). Our findings for inland, coastal waters agree with previous results for soils, suggesting that temperature sensitivities are variable across sites and increase with more complex, lower quality OM. Future modeling scenarios of DO utilization must therefore consider the influence of OM heterogeneity and the temperature sensitivity response of OM degradation across sources and region to better predict how climate change may impact oxygen impairment in aquatic ecosystems.

This dataset contains SUTRA input file and training image that used in our research paper "Randomly Distributed Crab Burrows Enhance Groundwater Flow and Salt Transport in Creek-Marsh Systems".

Degradation of estuarine water quality during the Anthropocene has largely resulted from discharges of nutrients leading to eutrophication. Recently, upstream management practices have led to comparatively reduced nutrient input into estuaries. Concurrently, climate cycles and impacts associated with anthropogenic climate warming can affect the long-term conditions observed within estuaries. Using long-term monitoring data from adjacent southeastern U.S. estuaries, we show that decadal-scale trends in nutrient concentrations and phytoplankton standing stock differ between the two connected systems. These contrasting trends appear to result from differences in oceanic influence, the extent of adjacent vegetated marsh, watershed size, and upstream degradation. In the minimally impacted, ocean-dominated North Inlet estuary, we document increasing ammonium and chlorophyll a (Chl a), while in the adjacent, river-dominated Winyah Bay, ammonium, and Chl a concentrations are more variable but do not appear to have increased over the same time period. Surprisingly, total nitrogen exhibits the opposite pattern: temporal stability in North Inlet but increasing in Winyah Bay. We hypothesize that sea level rise associated with climate change has driven a complex set of interactions between salt marsh porewaters and tidal pumping, leading to the spillover of nutrients from salt marshes into tidal creeks in North Inlet. In Winyah Bay, this mechanism is less evident as a driver of ammonium concentrations, likely due to the outsized effect of watershed nutrient input and the narrow fringing marsh platform. The degree to which this mechanism operates in other estuaries, which vary in tidal range, the extent of vegetated marsh, watershed size, and degree of anthropogenic degradation warrants further study.

Salt marshes are ecologically and economically important features of coastal environments that are vulnerable to sea level rise, the rate of which has accelerated in recent decades along the southeastern US Atlantic coast. Increased flooding frequency and duration across the marsh platform is predicted to impact vegetation community structure and overall marsh persistence, but the effect of changing inundation patterns on biogeochemical processes in marsh sediments remains largely unexplored. As part of a long-term monitoring effort to assess how marshes are responding to sea level rise in North Inlet estuary (South Carolina, USA), we collected data on porewater nutrient concentrations from a series of permanent monitoring plots across multiple transects spanning the marsh elevation gradient during the growing season from 2009 to 2019. Additionally, we calculated time inundated for each plot using local water level data and high-resolution elevation measurements to assess the change in time flooded at each plot. Our results indicate that both NH4 and PO4 nutrient concentrations have increased in most permanent plots over the 11-year study period and that nutrient concentrations are higher with increasing proximity to the creek. Spatial patterns in nutrient increases through time are coincident with considerable increases in tidal inundation observed over the marsh platform. Across plots located in the low marsh, porewater NH4 and PO4 concentrations have risen at average rates of 8.96 μM/year and 0.86 μM/year, respectively, and have reached rates as high as 27.25 μM/year and 3.13 μM/year. We suggest that increased inundation time due to rising sea level has altered biogeochemical conditions influencing nutrient availability in marsh porewater, resulting in increases that likely have relevance for larger scale nutrient cycles as well as marsh ecosystem stability and function.

Coastal wetlands of the Southeastern United States host a high abundance and diversity of critical species and provide essential ecosystem services. A rise in threats to these vulnerable habitats has led to an increased focus on research and monitoring in these areas, which is traditionally performed using manual measurements of vegetative characteristics. As these methods require substantial time and effort, they are often limited in scale and infeasible in areas of dense or impassable habitat. Unoccupied Aircraft Systems (UAS) provide an advantage over traditional ground-based methods by serving as a non-invasive alternative that expands the scale at which we can understand these ecosystems. While recent interest in UAS-based monitoring of coastal wetland habitats has grown, methods and parameters for UAS-based mapping lack standardization. This study addresses variability introduced by common UAS study techniques and forms recommendations for optimal survey designs in vegetated coastal habitats. Applying these parameters, we assess alignment of computed estimations with manually collected measurements by comparing UAS-SfM mapping products to ground-based data. This study demonstrates that, with careful consideration in study design and analysis, there exists great potential for UAS to provide accurate, large-scale estimates of common vegetative characteristics in coastal salt marshes.

Abundant crab burrows in carbon-rich, muddy salt marsh soils act as preferential water flow conduits, potentially enhancing carbon transport across the soil-water interface. With increasing recognition of blue carbon systems (salt marshes, mangroves, and seagrass) as hotspots of soil carbon sequestration, it is important to understand drivers of soil carbon cycling and fluxes. We conducted field observations and flow modeling to assess how crab burrows drive carbon exchange over time scales of minutes to weeks in an intertidal marsh in South Carolina. Results showed that continuous advective porewater exchange between the crab burrows and the surrounding soil matrix occurs because of tidally driven hydraulic gradients. The concentrations of dissolved inorganic (DIC) and organic (DOC) carbon in crab burrow porewater differ with that in the surrounding soil matrix, implying a diffusive C flux in the low-permeability marsh soil. Gas-phase concentrations of CO(2)in similar to 300 crab burrows were approximately six times greater than ambient air. The estimated total C export rate via porewater exchange (1.0 +/- 0.7 g C m(-2)d(-1)) was much greater than via passive diffusion transport (6.7 +/- 2 mg C m(-2)d(-1)) and gas-phase CO(2)release (1.8 mg C m(-2)d(-1)). The burrow-related carbon export was comparable to the regional salt marsh DIC export, groundwater-derived DIC export, and the net primary production previously estimated using ecosystem-scale approaches. These insights reveal how crab burrows modify blue carbon sequestration in salt marshes and contribute to coastal carbon budgets.

Increasing inputs of organic matter (OM) are driving declining dissolved oxygen (DO) concentrations in coastal ecosystems worldwide. The quantity, source, and composition of OM transported to coastal ecosystems via stormwater runoff have been altered by land use changes associated with urbanization and subsequent hydrologic flows that accompany urban stormwater management. To elucidate the role of stormwater in the decline of coastal DO, rain event sampling of biochemical oxygen demand (BOD) in samples collected from the outfall of stormwater ponds and wetlands, as well as samples of largely untreated runoff carried by stormwater ditches, was conducted across a range of urban and suburban development densities. Sampling also included measurements of particulate and dissolved carbon and nitrogen, carbon and nitrogen stable isotopes, and chlorophyll-a. Results suggest stormwater may be a significant source of labile OM to receiving waters, especially during the first flush of runoff, even though BOD concentrations vary both among and within sites in response to rain events. BOD variability was best predicted by particulate OM (POM) and chlorophyll-a, rather than the larger pool of dissolved OM. These findings demonstrate the importance of managing episodic stormwater discharge, especially POM, from urbanized areas to mitigate DO impairment in larger downstream systems.

Salt marshes serve as zones of intense groundwater mixing and reaction between freshwater uplands and estuaries. This raises the question of whether the impacts of upland development on nutrient and carbon species can be transmitted through salt marshes via groundwater, or whether salt marshes can buffer estuarine waters from coastal development. We sampled groundwater from fifteen tidal creek basins in South Carolina to test for compositional differences associated with development and marsh width. Groundwater samples from near creekbanks and below freshwater uplands were analyzed for salinity, total dissolved nitrogen and phosphorus, and dissolved organic carbon. Analyses revealed significantly higher TDN and TDP concentrations in creekbank samples from developed watersheds, independent of the season. Analyses of upland samples revealed significantly lower DOC concentrations in developed uplands, again independent of season. These results support the hypothesis that development can affect groundwater compositions in coastal groundwater and therefore may affect coastal nutrient and carbon fluxes. However, results also revealed significant linear correlations between marsh width, salinity, and nutrient concentrations in some marshes. These results suggest that salt marshes can act as buffers for development, and specifically suggests that the buffering capacity of salt marshes increases with width. Narrow or trenched salt marshes are far less likely to be effective buffers.

Earth and Space Science Open Archive PosterOpen AccessYou are viewing the latest version by default [v1]Greater than averages: how metrics of extreme weather are trending differently than averages would suggestAuthorsCameronLeeiDOmonObareiniDScottSheridaniDErikSmithiDRyanAdamsSee all authors Cameron LeeiDCorresponding Author• Submitting AuthorKent State University Kent CampusiDhttps://orcid.org/0000-0002-5380-6601view email addressThe email was not providedcopy email addressOmon ObareiniDKent State University Kent CampusiDhttps://orcid.org/0000-0002-6702-1143view email addressThe email was not providedcopy email addressScott SheridaniDKent State University Kent CampusiDhttps://orcid.org/0000-0002-6928-6524view email addressThe email was not providedcopy email addressErik SmithiDKent State University Kent CampusiDhttps://orcid.org/0000-0002-8133-0348view email addressThe email was not providedcopy email addressRyan AdamsKent State University Kent Campusview email addressThe email was not providedcopy email address

Nutrient breakpoints are the concentration at which there is a fundamental change in phytoplankton responses to further increases in nutrient loading. The ecological implication is that nutrient breakpoints signal a community transition from a relatively stable state to an alternate or transition state with marked changes in structure and, by extension, function. Nutrient breakpoints for the total phytoplankton community and individual phytoplankton groups in response to increases in dissolved inorganic nitrogen (DIN) concentrations were determined for two contrasting estuarine systems. Phytoplankton were exposed to increasing N addition scenarios (0-100 mu mol DIN L-1) under high and low irradiance conditions. Responses of total algal biomass, group diversity, and individual algal groups were determined after 72-h incubations in experimental bioassays. Phytoplankton from the low-salinity estuary exhibited higher DIN breakpoints (>double) than the high-salinity estuary while irradiance (20% vs. 40% of ambient) did not affect breakpoints. DIN additions changed algal group diversity, but community similarities were > 80%. Our results suggest that ambient DIN concentrations should not exceed breakpoint concentrations to prevent possible shifts from a stable to a transitional or alternate state. DIN thresholds should be 25 and 50 mu mol L(-1)for the high- and low-salinity estuaries, respectively. These levels should mitigate the risk of major alterations in phytoplankton community structure and function in these two estuarine systems.

The generality of ecological patterns depends inextricably on the scale at which they are examined. We investigated patterns of crab distribution and the relationship between crabs and vegetation in salt marshes at multiple scales. By using consistent monitoring protocols across 15 U.S. National Estuarine Research Reserves, we were able to synthesize patterns from the scale of quadrats to the entire marsh landscape to regional and national scales. Some generalities emerged across marshes from our overall models, and these are useful for informing broad coastal management policy. We found that crab burrow distribution within a marsh could be predicted by marsh elevation, distance to creek and soil compressibility. While these physical factors also affected marsh vegetation cover, we did not find a strong or consistent overall effect of crabs at a broad scale in our multivariate model, though regressions conducted separately for each site revealed that crab burrows were negatively correlated with vegetation cover at 4 out of 15 sites. This contrasts with recent smaller-scale studies and meta-analyses synthesizing such studies that detected strong negative effects of crabs on marshes, likely because we sampled across the entire marsh landscape, while targeted studies are typically limited to low-lying areas near creeks, where crab burrow densities are highest. Our results suggest that sea-level rise generally poses a bigger threat to marshes than crabs, but there will likely be interactions between these physical and biological factors. Beyond these generalities across marshes, we detected some regional differences in crab community composition, richness, and abundance. However, we found striking differences among sites within regions, and within sites, in terms of crab abundance and relationships to marsh integrity. Although generalities are broadly useful, our findings indicate that local managers cannot rely on data from other nearby systems, but rather need local information for developing salt marsh management strategies.