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Deep sea bacteria completely devoured much of the natural gas released in the Gulf of  Mexico oil spill, a scientific team concluded Thursday.

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BP contract worker Chris Wiggins (right) and USA Today

reporter Julie Schmidt (left) walk through tar balls on the

coast of Mississippi in October 2010. Along the Gulf of

Mexico, oil spill tar balls are still washing ashore.
By Sean Gardner, USA TODAY

The findings help build the case that ocean bottom bugs are a natural biofilter that regularly dine on natural seeps of methane, or natural gas, and related chemicals worldwide.

Methane was the most abundant component of the summer oil spill. About 220,000 tons was released from April to July. The finding adds to evidence that deepwater microbes also consumed other "light" crude oil constituents, such as propane and ethanol, released in the spill.

"We expected the methane to persist longer," says study co-author David Valentine of the University of  California, Santa Barbara, based on June estimates. By September, he says, "the complete consumption of methane came as a surprise." Measures suggest only 0.01% of the methane released in the spill still lingered at depth.

Intense water pressure and cold temperatures at the spill site, 5,000 feet deep, kept much of the methane trapped in underwater layers, where the microbes could feast on the gas, instead of allowing it to bubble to the surface.

Study samples found that deep water layers formerly laced with methane were filled with evidence of methane-eating bacteria populations that had grown "exponentially" over the summer. The results suggest "bacterial communities may act as a dynamic biofilter that responds rapidly to large-scale (natural gas) inputs into the deep ocean," the study says.

"The Gulf of Mexico has more (oil and natural gas) seeps than practically anywhere in the world, and the microbes there were likely primed to grow there," says microbiologist Terry Hazen of the Energy Department's Lawrence Berkeley (Calif.) National Laboratory, who was not part of the study. The study results match unpublished microbe measures made by his team this fall, Hazen adds.

The study results come a day after a presidential commission investigating the Deepwater Horizon spill found safety concerns with oil industry deep sea drilling, now contemplated everywhere from the Arctic and off the coast of Brazil.

Source: USA Today

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