Oil-Leak Methane Consumed By Bacteria

It took a little while for methanotrophic bacteria to gear up to consume methane spilled along with the oil after BP’s Deepwater Horizon rig exploded in the Gulf of Mexico last year. But once the bacteria got started, they made quick work of the job, reports a group led by John D. Kessler of Texas A&M University and David L. Valentine of the University of California, Santa Barbara (Science, DOI: 10.1126/science.1199697). Methane was the single most abundant hydrocarbon released in the oil spill. Based on CH₄ concentrations and oxidation rates measured around the wellhead last June, the researchers expected that the CH₄ would remain in the water for years. When the group returned to the Gulf at the end of August, however, CH₄ concentrations had dropped to ambient levels. The researchers found a microbial community that included 5–36% methanotrophic bacteria, which were not detected in earlier microbial assays. They also found low concentrations of dissolved O₂, which would have been used up as the microbes oxidized CH₄ to CO₂. Large, natural CH₄ releases in the geologic past may have been at least partially consumed by a similar bacterial response, the researchers suggest.