Spatial and temporal variability in marsh-water column interactions in a southeastern USA salt marsh estuary

The exchange of inorganic nutrients and particulate matter between the Spartina alterniflora marshes and the adjacent estuary of Cumberland Island, Georgia, USA was measured. Temporal variability in total and organic suspended sediment fluxes, which was largely related to quickly changing wind and wave conditions, was greater than spatial variability measured during the same time. Dissolved constituent fluxes were generally more variable across space, suggesting that day-to-day variability in dissolved nutrient exchanges was not a major contribution to spatial variability. Dissolved inorganic nutrient fluxes (as ammonium, nitrate+nitrite, and soluble reactive phosphorus) followed a spatial pattern of highest nutrient uptake at the geologically young marsh site. This marsh also consistently imported dissolved organic carbon. This site has the lowest absolute elevation of the three sites and a ramp-like topographic profile, and its young geologic age suggests that it is also ecologically immature. Fluxes of dissolved constituents at this site were negatively related to the area of marsh inundated, switching to export when large areas of the young marsh were inundated for long periods of time. -from Authors