The sedimentary flux of nutrients at a Delaware salt marsh site: A geochemical perspective

Abstract

A basic geochemical approach has been used to study the diagenetic cycling and sediment-water exchange rates of essential nutrients at a site in a Delaware salt marsh. The pore water nutrients Si (OH)4, NH4+, PO4−3, and NO3− were analyzed and compared seasonally, and potential diffusive fluxes were calculated from the corresponding pore water concentration gradients. Concurrent direct flux measurements were also made using closed chambers deployed on the salt marsh surface under ambient and controlled conditions. The differences in these two approaches allows for estimation of nutrient production and consumption in the root zone and at the salt marsh surface. Silicate and phosphate appear to be primarily geochemically controlled, while the nitrogen species undergo dynamic seasonal redox fluctuations resulting from microbial mediation (e.g., nitrification and denitrification).