Annual material processing by a salt marsh-estuarine basin in South Carolina, USA

Abstract

A synthesis of a comprehensive annual study of material processing in the Bly Creek marsh-estuarine basln is described. The project design provides statistical estimates of material fluxes for the water column, salt marsh, and oyster reef subsystems. Fluxes from a freshwater stream, groundwater, and rain are also presented Material processing by the Bly Creek marsh-estuarine basin is constituent-and subsystem-specific Inflows of material via rain, streamwater. and groundwater are small and relatively unin~portant compared to tidal fluxes. The salt marsh dominates the basin in aerial extent and in terms of net material fluxes. Most constituents exhibit significant net annual import to the salt marsh. Only DON is exported from the marsh and from the basin at significant levels. The salt marsh appears to recycle most of the nitrogen and phosphorus needed for marsh grass primary production. Sufficient inorganic particulate material is imported to allow the salt marsh to maintain its elevation with respect to ongoing sea-level rise. As a result of metabolic processes, the oyster reef imports particulate materials and releases dissolved nutrients. The reef is a significant consumer of chl a and produces enough dissolved inorganic nitrogen and phosphorus to support water column primary production The N:P ratio of Bly Creek dissolved inorganic nutrients is lower than that of North Inlet or ocean waters and implies nitrogen conservation or mobilization of particulate phosphorus into orthophosphate. In contrast to human-impacted coastal systems, this prist~ne basin reduces the N : P rat10 as water passes through it Differences in the N:P ratio are probably the result of DON export, denitnfication, and phosphorus import by the basin