S62: Coastal Alabama Bacterial Community Responses to the Deepwater Horizon Oil Spill

The microbial community responses of an Alabama coastal marsh ecosystem to the Deepwater Horizon oil spill were studied by microarray-based phylogenetic and functional gene analysis.  Visible oil, tar balls, and mousse associated with the spill were detected at our study site in July 2010.  Marsh and inlet samples collected in June 2010 (pre-oil) and July 2010 from a marsh ecosystem at Point Aux Pines Alabama were analyzed to determine if bacterial community structure changed after oil perturbation. Distinctive changes in the number of detectable OTUs were observed between June and July.  Surficial inlet sediments indicated a >2-fold increase in the total number of OTUs in July compared to June.  Significant increases in bacterial abundances were observed for Actinobacteria, Firmicutes, Gemmatimonadetes, Proteobacteria- Desulfovibrionales, and Verrucomicrobia populations.  Marsh sediments extracted from 8-10 cm depth also demonstrated ~2-fold increase in OTUs in July.  The OTUs primarily belonged to Acidobacteria, Actinobacteria, Firmicutes, Fusobacteria, Nitrospirae, and Proteobacteria-Desulfovibrionales.  GeoChip microarray analysis detected 5000 to 8300 functional genes in marsh and inlet samples.  Surficial inlet sediments demonstrated distinctive increases in the number of detectable genes and gene signal intensities in July samples compared to June.  Signal intensities increased (>1.5-fold) for genes associated with petroleum degradation.  Genes related to metal resistance, stress, and carbon cycling also exhibited increases in oiled sediment samples.  This study demonstrates the value of applying phylogenetic and functional gene microarray technology to characterizing the extensive microbial diversity of marsh environments. Moreover, this technology provides significant insight into bacterial community responses to anthropogenic oil events.