Methane Returned to Near-Normal Levels in Gulf
Findings from the research study, led by oceanographers John Kessler of Texas A&M and David Valentine of UCSB, were published in Science Xpress, in advance of their publication in the journal Science. The findings show that Mother Nature quickly saw to the removal of more than 200,000 metric tons of dissolved methane through the action of bacterial blooms that completely consumed the immense gas plumes that the team had identified in mid-June.
At that time, the team reported finding methane gas in amounts nearly 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."
Based on measurements from earlier in the summer and previous other measurements of methane respiration rates around the world, it appeared that (Deepwater Horizon) methane would be present in the Gulf for years to come. Instead, the methane respiration rates increased to levels higher than have ever been recorded, ultimately consuming it and prohibiting its release to the atmosphere." While the scientists' research documents the changing conditions of the Gulf waters, it also sheds some light into how the planet functions naturally. This tragedy enabled an impossible experiment, allowing the researchers to track the fate of massive methane release in the deep ocean, as has occurred naturally throughout Earth's history.
Kessler noted, "The seafloor stores large quantities of methane, a potent greenhouse gas, which has been suspected to be released naturally, modulating global climate. What the Deepwater Horizon incident has taught us is that releases of methane with similar characteristics will not have the capacity to influence climate."
The research team collected thousands of water samples at 207 locations covering an area of about 36,000 square miles. The researchers based their conclusions on measurements of dissolved methane concentrations, dissolved oxygen concentrations, methane oxidation rates and microbial community structure.
