When the blowout of the Deepwater Horizon oil well sent some 400,000 tonnes of methane into the Gulf of Mexico in April 2010, many scientists and others feared it would linger. So researchers were pleasantly surprised when studies suggested that methane-eating bacteria had consumed nearly all of it by August.
But new evidence suggests an alternate scenario. Research published today in Nature Geoscience finds that although these bacteria consumed much of the gas, they slowed down considerably after a few months. In fact, bacteria only consumed roughly half of the methane, according to co-author author Samantha Joye, a microbial biogeochemist and oceanographer at the University of Georgia in Athens.
The team analyzed more than 1,000 water samples collected over more than 105,000 square kilometres during 10 expeditions to the gulf between March and December 2010.
The analysis finds that about two weeks after the blowout, methane oxidation rates – an indication of how much methane the bacteria were consuming – began rising, and increased steadily until early June. But later that month, the feeding frenzy had subsided, with rates tumbling from their peak by one or two orders of magnitude.
“We saw a boom and bust,” says Joye. That decline came, she says, despite ample remaining methane for the bacteria to nosh on.