Temporal effect of plant diversity and oiling on nitrogen cycling in marsh sediments

The effect of plant diversity on ecosystem recovery from oil spills and temporal effects on biogeochemical cycles needs to be investigated to identify key ecosystem processes as well as the various challenges associated with coastal ecosystem recovery. Oil spill effects on nitrogen cycling caused by either changes in species composition of primary producers or microbial community composition have also been documented. Although low to moderate oiling of coastal wetlands has been shown to impact ecosystem functions, studies focused on determining long term impacts of oil spills on marsh vegetation, microbial community composition and associated effects on nitrogen cycling are relatively limited. This project investigated temporal effects of plant diversity on denitrification and microbial community dynamics through mesocosm experiments. The mesocosms consisted of the black mangrove, Avicennia germinans, along with either a monoculture or polyculture of the smooth cord grass, Spartina alterniflora. The results presented were obtained using DNA extracted from replicate sediment cores sampled in April 2016, 6 months after the mesocosms were treated with oil to achieve a final concentration of 4000 ppm.