Fate Of Gulf Oil Spill Methane Reexamined

Methane released into the Gulf of Mexico after the Deepwater Horizon oil rig exploded and sank in April 2010 may not have been as quickly consumed by oceangoing microbes as previously thought. Methane was the single most abundant compound by mole in the mix of oil and gas released into the Gulf. One initial study of water samples collected after the spill indicated that the methane was largely confined to a deep plume 1 km below the surface and consumed by microbes within a month after the well was capped (C&EN, Jan. 10, 2011, page 31). In the new work, analysis of a different set of samples suggests instead that the colony of methane-consuming microbes that bloomed after the spill consumed perhaps half of the methane, then crashed as the gas dispersed throughout the water (Nat. Geosci. 2014, DOI: 10.1038/ngeo2156). Researchers led by Samantha B. Joye of the University of Georgia continued to detect elevated methane levels north of the wellhead for several additional weeks. What caused the microbial crash is unclear. Possibilities include a lack of nutrients, such as iron, or methane concentrations dropping to a level that could not sustain the microbe population.