Sediment Biogeochemistry Across the Patuxent River Estuarine Gradient: Geochronology and Fe-S-P Interactions

Abstract

Although salinity and redox gradients are defining features of estuarine biogeochemistry, compositional changes in sediment characteristics associated with these factors are poorly described in U.S. coastal plain estuaries. Understanding the basics of nutrient sources and sinks, in the context of these defining characteristics, is required to make efficient and effective management decisions regarding estuarine eutrophication. In this study, detailed analysis of long-term nutrient burial has been used as a tool to understand the trajectory of nutrient cycling at 7 stations along an oligohaline to mesohaline transect in the Patuxent River estuary. Sediment mass accumulation rates were determined for 3 of the 7 sites. Cores analyzed for total P, total N, organic C, biogenic silica, δ13C, and δ15N did not provide evidence of historical nutrient reduction actions taken in this watershed. Burial rates of Fe-S mineral phases and inorganic P (IP) indicated pyrite formation limited the availability of Fe-oxides for adsorption and retention of IP.