TEMPORAL SALT MARSH SEDIMENT RESPONSE TO THE DEEP WATER HORIZON BP OIL SPILL AT MARSH POINT, MS

Salt marshes may experience adverse effects due to long-term exposure to oil contamination which causes accumulation of oil in marsh sediments. As a result of increased carbon loading from spilled hydrocarbons, porewater oxygen is rapidly depleted, resulting in an increase in porewater sulfide (H₂S) concentrations. Elevated H₂S concentrations, due to increased microbial activity, make sediments more toxic and inhospitable to marsh vegetation often causing salt marsh browning and dieback. Careful monitoring of porewater sulfide allows for an assessment of oil spill impact on salt marshes over time. Sediment cores collected from Marsh Point in Ocean Springs, MS during the Fall of 2010 indicated that sulfate reducing bacteria were significantly more active in contaminated sediments, producing sulfide concentrations 20x higher than in non-contaminated sediments. The difference in the sediment biogeochemistry between the contaminated site and non-contaminated site at Marsh Point indicated that the effect of hydrocarbon contamination on salt marsh sea grasses should be monitored. As such, sediment electrode profiles (H₂S, O₂, pH, and Eh), degree of hydrocarbon contamination (GC), microbial community substrate level carbon utilization profiles, and total organic carbon amounts were collected at Marsh Point from 2010- 2012 in order to assess the temporal change in sedimentary geochemical processes since the Deep Water Horizon BP Oil Spill. Results of these sedimentary biogeochemical measures over the three year study period at Marsh Point, MS will be presented. Die back from 2010-2012 at Marsh Point, MS was monitored using remote sensing and these data will be presented in conjunction with the aforementioned biogeochemical measures.