Potential and actual rates of nitrogen cycling in salt marsh soils, Terrebonne Bay (LA), 2014

We investigated potential and actual rates of marsh soil nitrogen cycling seasonally (April, July, and October 2014) in 6 Terrebonne Bay marsh sites. In this study, we chose three regions where we could find oiled and unoiled pairs of marshes located within close proximity to each other. Potential rates of N-cycling (15N-labelled NO3 soil incubations) and denitrification enzyme activity (DEA) were measured at 2 locations (1 and 10m from the marsh edge) at all six sites. Actual N cycling rates were conducted using 15N-labelled flooded 4cm diameter sediment cores collected 10m from the marsh edge at each site. 5 replicate cores were collected from each of two sites per date and destructively sampled during the linear portion of DO decline in the overlying water. Additionally, we measured a series of basic site characterizations, soil properties, assessed oil status, and characterized the dissolved inorganic nutrient concentrations in overlying water and adjacent bay water samples.