Sandy Shoreline Swashes as Loci of Land-ocean Interactions at an Urbanized Coastline.

Water quality impairment in densely inhabited and altered coastlines is a global phenomenon mediated by the transport of pollutants from land to ocean via surface and groundwater runoff. In the case of the increasingly urbanized coastline of Long Bay, South Carolina, numerous "swashes", sandy shoreline fields reworked by estuarine tidal creeks, constitute an important land-to-ocean exchange feature and mechanism. The focus of our investigations into swashes is their role as both conduits and modifiers/bioprocessors of land-derived nutrients. In this presentation, we review our current knowledge on swash biogeochemical function and propose next steps in our research. We use data on physicochemical properties (temperature, salinity, oxygen, nutrients and chlorophyll) to characterize seasonal cycling, the impact of coastal works (e.g., channel realignment), and the role of discrete surface point-sources on primary channel biogeochemistry. We speculate on the role of non-point source (e.g., groundwater) nutrient fluxes, and benthic photosynthesizers (e.g., microphytobenthos and submerged aquatic macroalgae), in exacerbating and ameliorating nutrient loading to the coastal ocean, respectively. Through this research that down-scales approaches developed for large rivers and estuaries, we hope to better understand how numerous small swashes can modify land impacts on coastal-ocean water quality.