A significant fraction of the vast amounts of natural gas injected into the water column during the 2010 Deepwater Horizon disaster in the Gulf of Mexico was not consumed by bacteria by the end of August, as had been thought, concludes an article published online in Nature Geoscience. Instead, the activity of methane oxidizing bacteria declined rapidly before the discharge from the wellhead was finally shut down, suggesting that factors other than methane availability regulate the ecosystem response to a spill.
Samantha Joye and coauthors measured methane concentrations in the water column along with the activity of methane-oxidizing bacteria in the nine months following the initial spill. They found that rates of methane consumption rose rapidly in May and early June, but collapsed in late June - although methane was still being released from the wellhead. As a result, elevated methane levels lingered until at least the end of the year.
In an accompanying News and Views article, Evan Solomon writes, “Microbial respiration of methane in the water column is the last filter before the greenhouse gas is emitted to the atmosphere, and could lead to local hypoxia and ocean acidification”.