Calling the results "extremely surprising," researchers from the University of California, Santa Barbara and Texas A&M University report that methane gas concentrations in the Gulf of Mexico have returned to near normal levels only months after a massive release occurred following the Deepwater Horizon oil rig explosion.

Findings from the recent research study, led by oceanographers John Kessler of Texas A&M and David Valentine of UC Santa Barbara, were published today in Science Xpress in advance of their publication in the journal Science. The findings show the removal of more than 200,000 tons of dissolved methane through the action of bacteria blooms that completely consumed the immense gas plumes the team had identified in mid-June 2010. At that time, the team reported finding methane gas in amounts 100,000 times above normal levels. But, about 120 days after the initial spill, they could find only normal concentrations of methane and clear evidence of complete methane respiration.

"What we observed in June was a horizon of deep water laden with methane and other hydrocarbon gases," Valentine said. "When we returned in September and October and tracked these waters, we found the gases were gone. In their place were residual methane-eating bacteria, and a 1 million ton deficit in dissolved oxygen that we attribute to respiration of methane by these bacteria."