S23: Response of petroleum-degrading microbial communities to the Deepwater Horizon oil spill at the surface and in the deep

The Deepwater Horizon oil spill in the Gulf of Mexico is the largest spill in U.S. history and is having far-reaching impacts on natural resources and human livelihoods across the Gulf region. Unprecedented management actions are being used to reduce the amount of oil at the surface, including injection of chemical dispersant directly into the well head and widespread aerial spaying.  There appears to be large plumes of oil extending tens of kilometers away from the leak at depths of over 1100 m.  The indigenous bacteria and archaea in the Gulf of Mexico will ultimately degrade much of the oil over time.  However, little is know about the composition and oil-degrading capacity of marine microbial communities at great depths in the Gulf.  In addition, the direct and indirect effects of chemical dispersant on oil-degrading microorganisms are uncertain.  We surveyed microbial communities in both the surface and deepwater plumes and outside the plumes on several oceanographic cruises in May and June 2010. We used phylogenetic microarray analysis (PhyloChip), functional gene analysis (GeoChip) and quantitative PCR detection of petroleum-degrading bacteria to characterize the composition, structure and activity of microbial communities in oil- and dispersant-affected waters.  These data were compared to physical and chemical measurements of the oil and its degradation products.  The results will help predict the fate of dispersed oil at depth and inform decisions that consider the longer-term consequences of dispersant application on bioremediation.