(Dow Jones Newswires), Jan. 7, 2011
Bacteria made quick work of the tons of methane that billowed into the Gulf of Mexico along with oil from April's Deepwater Horizon blowout, clearing the natural gas from the waterway within months of its release, researchers reported Friday.
The federally funded field study, published online in the journal Science, offers peer-reviewed evidence that naturally occurring microbes in the Gulf devoured significant amounts of toxic chemicals in oil and natural gas spewing from the seafloor, which researchers had thought would persist in the region's water chemistry for years.
"Within a matter of months, the bacteria completely removed that methane,"said microbiologist David Valentine at the University of California at Santa Barbara. "The bacteria kicked in more effectively than we expected," he said.
Dr. Valentine was part of a research team that tested samples from more than 200 locations across 38,000 square miles of the Gulf during three research cruises between August and October, after the well was shut down last year.
The fate of the methane is only one aspect of the environmental impact on the Gulf of the massive spill. All told, scientists estimate that 200,000 tons or more of methane bubbled from the damaged BP well -- about 20% of the hydrocarbons released during the spill -- along with about 4.4 million barrels of petroleum.
The crude oil settled on the seafloor as sludge within a mile or so of the damaged drill head, floated to the surface, washed ashore or was diluted by chemical dispersants dissolved into the seawater.
In a report last month, federal officials managing the cleanup effort said there was no longer any significant oil from the spill left offshore and no evidence of chemical dispersants in the water that exceeded federal safety standards. Most state and federal fisheries in the Gulf have reopened.
David Rainey, a vice president of science, technology, environment and regulatory affairs for BP's Gulf Coast Restoration Organization, which had no role in the new study, called the methane findings "very good news for the Gulf of Mexico."
The report stirred disbelief among several microbiologists studying the aftermath of the 87-day oil and gas leak. "I think they are jumping to a conclusion," said University of Georgia microbiologist Samantha Joye, who has been analyzing methane from the damaged wellhead independently. "It would take a superhuman microbe to do what they are claiming."
But Robert Haddad, head of the damage-assessment effort at the National Oceanic and Atmospheric Administration, said, "The data they've collected on the methane plume is consistent with what we've seen."
Early tests by researchers at Texas A&M University around the damaged wellhead showed that little of the methane gas ever reached the surface.
The scientists determined almost all of it had been trapped in a plume of microscopic oil droplets in a layer of water between 2,600 feet and 3,900 feet deep. The measurements the scientists made in June showed that methane levels in the water were tens of thousands of times higher than normal. Now it is nowhere to be found.
"We were shocked," said chemical oceanographer John Kessler at Texas A&M, who was the lead author of the Science study. "We thought the methane would be around for years."
By comparing the water samples from their Gulf cruises, Dr. Kessler and his colleagues found a telltale drop in the amount of oxygen left in the water that appeared to precisely equal the amount needed for microbes to metabolize so much methane.
The bacteria appeared to remove 100 million tons of oxygen from the water, not enough to cause an oxygen-starved dead zone that would be fatal to other marine life, the researchers said.
In addition, genetic tests revealed relatively high levels of microbes known to consume methane.
"This is very compelling evidence that the methane had been consumed," said geo-microbiologist Antje Boetius at the Max Planck Institute for Marine Biology in Bremen, Germany, an expert on methane microbes who wasn't involved in the study.
If borne out by additional research, the ability of ocean microbes to absorb such large releases of methane so rapidly also has implications for the study of global warming and the potential for catastrophic climate changes, the researchers said.
Methane is a greenhouse gas 24 times more potent than carbon dioxide. Under some climate-change scenarios, scientists worry that large natural leaks of methane, which is cached in vast reservoirs beneath the seafloor, could reach the surface where the gas could affect temperatures. These microbes could block that.
"They showed that, even when there is a massive release of methane, the ocean can compensate," said microbiologist Terry Hazen at the Lawrence Livermore National Laboratory.
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