RAPID: The Microbial Response to the Deepwater Horizon Oil Spill

Intellectual merit: This RAPID project will conduct a time series of microbiological and geochemical assessments of the consequences of the Deepwater Horizon oil spill offshore the Louisiana coast. The PIs are building on a large database of pre-spill baseline microbiology and biogeochemistry at a microbial observatory (Mississippi Canyon 118) near the Deepwater Horizon site they have occupied since 2005. They are applying molecular, gene-based analyses of the microbial community structure and function in surface water and underlying sediments; in situ water column dissolved oxygen and light hydrocarbon measurements using advanced sensor technologies (Seaguard system) for deep water plume tracking; and a biogeochemical survey of the sediments and water in the immediate vicinity of and at increasing distance from the oil spill, and on different time scales during follow-up cruises. 16S rRNA and functional gene sequencing of total microbial DNA and RNA from contaminated and clean water and sediments will monitor how the oil-affected microbial community changes in composition and activity. High-throughput pyrosequencing of PCR-amplified rRNA fragments will increase the coverage by approx. three orders of magnitude, and allow for the detection of minority microbial populations that go unnoticed in conventional clone libraries. Special attention will be paid to the enrichment of oil-degrading bacteria in natural samples and in time-series experiments conducted in the lab, to monitor their growth with group-specific PCR, to monitor geochemical changes concomitant with the establishment and enrichment of a hydrocarbon-degrading microbial community, and to identify potential carbon incorporation pathways with stable isotope probing of nucleic acids. Summarizing, this RAPID project focuses on molecular and microbiological assessments of hydrocarbon impact, across the spatial and time scales of the Deepwater Horizon oil spill as determined by diagnostic water column oxygen and light hydrocarbon measurements. The water column microbiological and dissolved gas data will be linked to potential impacts on the bacterial activity in bottom sediments through measurements of geochemical indicators of sedimentary anaerobic microbial activity, and porewater analyses of DIC, CH4 and low-molecular weight organic acids, the principal products of hydrocarbon degradation. The PIs are coordinating their research with Mandy Joye at the University of Georgia.

Broader Impacts: The results of this RAPID project will identify which bacterial and archaeal populations, and in which sequence, respond to oil spill events in marine sediments and the water column, and the attendant - often beneficial - biogeochemical consequences of this massive restructuring of the microbial community and their activities. Most importantly, this project provides comprehensive microbial and geochemical coverage of different marine habitats (deep and shallow marine sediments, water column, surface) on the geographical and time scale of the oil spill as it is unfolding. This independent analysis will contribute to an observation-based and results-oriented reference database that, at present, the various interested players in the Deepwater Horizon saga cannot provide. The PIs are working on national publicity for our cruises and on-site work, by taking a National Geographic writer (Joel Bourne) on the current RV Walton Smith cruise, and interviews with Scientific American and National Geographic. The PIs have developed an extensive student-oriented outreach component that entrains - with a combination of teaching, lab internships, conference visits and virtual as well as real cruise exposure - undergraduates from different backgrounds into grant-driven research and gives them an early start on substantial, publishable research projects. The Martens lab has been active since 2005 in partnering NSF-funded research projects with science education and outreach programs that can influence and attract the next generation of oceanographers.