Spatial heterogeneity of nitrogen cycling in Deepwater Horizon-impacted salt marshes from May 2016-February 2017

Humans have more than doubled the amount of reactive nitrogen (N) in the environment, contributing to marine eutrophication. Salt marshes provide important areas of N removal through microbial mediated N-cyling. However, oil spills may alter or reduce their functional capacity by reducing plant biomass or altering sediment microbial communities. The objective of our study is to determine the effects of the Deepwater Horizon oil spill on nitrogen (N) cycling in salt marsh sediments. A study was conducted in the Chandeleur Islands, a chain of barrier islands off the coast of Louisiana which were subjected to a gradient of oil deposition following the spill. Starting in June 2016, we collected sediments from three sites subjected to a range of oiling to determine the legacy effect of the oil spill on sediment denitrification and nitrogen fixation (N2-fixation). Denitrification capacity, which was determined using the isotope-pairing technique, was highest in September (63.9±30.2) µmol N m-2 h-1).