Bacteria ate nearly all the potentially climate-warming methane that spewed from BP's broken wellhead in the Gulf of Mexico last year, scientists reported on January 06.
-- Nearly 200,000 tons of methane consumed naturally
-- Bacteria kept climate-warming chemical out of air
Nearly 200,000 tons of methane - more than any other single hydrocarbon emitted in the accident - were released from the wellhead, and nearly all of it went into the deep water of the Gulf, researcher David Valentine of the University of California-Santa Barbara said in a telephone interview.
Bacteria managed to take in the methane before it could rise from the sea bottom and be released into the atmosphere, but the process contributed to a loss of about 1 million tons of dissolved oxygen in areas south-west of the well.
That sounds like a lot of oxygen loss, but it was widely spread out, so that the bacterial munching did not contribute to a life-sapping low-oxygen condition known as hypoxia, said Valentine, whose study was published in the journal Science.
What happens to methane has been a key question for climate scientists, because methane is over 20 times more effective at trapping heat in the atmosphere than carbon dioxide. Like carbon dioxide, methane comes from natural and human-made sources, including the petroleum industry.
For two months after the BP blowout on April 20, 2010, methane was not being consumed in and around the wellhead, leading some scientists to suspect it might linger in the water and eventually make its way into the air, where it could potentially trap heat and contribute to climate change.
"If you have a very large release of methane like this, and it did make it into the atmosphere, that would be a problem," Valentine said.
"There have been a number of large-scale methane releases in the past that have come from the ocean that have warmed the climate," he added.
Those methane releases came from natural sources, and researchers like Valentine and his co-authors wondered what role bacteria might have had in those cases.
The BP spill offered an "accidental experiment" that showed particular bacteria with an all-methane diet multiplied quickly as the methane spread with the underwater plume from the broken well. Peak consumption of methane probably came in late July and early August, Valentine said.
Other organisms dealt with other hydrocarbons, including ethane and propane emitted in the worst offshore oil spill in U.S. history. The methane-eating bacteria were the last to the hydrocarbon banquet, and based on past observation, the scientists questioned whether they could do the job.