The Deepwater Horizon oil spill released an unprecedented amount of oil into the Gulf of Mexico deep water system in April 2010, some of which was deposited to the seafloor.  While studies reported that endemic microbial communities were able to breakdown this oil, it is still unclear how microbial communities in the sediments responded to this influx of oil.  In conjunction with in situ experiments in the Gulf of Mexico, here, we carried out laboratory experiments to explore how anaerobic processes such as sulfate reduction, anaerobic methane oxidation, and methanogenesis degrade oil and at what rates.  We hypothesized that the addition of oil will stimulate sulfate reducers due to the influx of a new carbon source.  This, in turn, will shift zones of microbial activity so that methanogens will begin to produce methane at a shallower depth than the controls.  For the experiment, sediment cores (~20 cm long) were collected from a shallow-water estuary where salinity is 13 psu.  The cores were permanently fitted with rhizone samplers to collect pore-waters every 3-5 cm.  For the experiment, there were two treatments, one with just surface sediment and original carbon content, and one treatment where the surface sediment was added to oil in a 5:1 ratio.  Five milliliters of either treatment material was added to the surface sediment, and pore-water time points collected every week over the next 2 months.  Pore-water samples were measured for sulfate and methane concentrations.  Results will elucidate the impact such oil additions have on anaerobic processes in the deep-sea sediments.  If the hypotheses are correct, this has long-term consequences on methane levels that may potentially rise to the surface through physical processes and function as a greenhouse gas.

Understanding the impacts of the Deepwater Horizon oil spill on sedimentary microbial processes

247th National Meeting (2014)

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