Hungry microbes

British oil company BP has used dispersants, burns and skimming operations in a bid to clean up the worst oil spill in US history. Now, new research indicates that nature might be lending a hand: According to a study published in the journal Science on Tuesday, microbes are consuming and breaking down the huge underwater plume of crude in the Gulf of Mexico.

A team led by Terry Hazen of the Lawrence Berkeley National Laboratory, monitored the oil plume starting in May – and that meant tracking the microbes eating it. The study involved work at 17 deepwater sites to gather more than 200 samples. Scientists found that microbes were consuming the oil without significantly depleting oxygen levels.

More recently, the team failed to detect the underwater plume, indicating that microbes were gobbling it up.

US scientists say about 4.9 million barrels of oil have leaked into the Gulf since April, more than five times the amount spilled during the Exxon Valdez disaster.

A scientific snapshot

The latest findings seemed to run counter to a study published in the same journal on August 19, which noted no marked signs of microbial biodegradation. Scientists from the Woods Hole Oceanographic Institute examining the plume's chemical composition noted that dissolved oxygen levels within the plume were close to the levels recorded outside it.

Chris Reddy, a Woods Hole scientist, said those oxygen levels indicated that if microbes were consuming the oil, they were doing so very slowly.

"Any self-respecting microbe will want to eat oil – it is like butter," he said. "But microbes are a lot like teenagers. They do what they want, when they want, and so it's difficult often to make predictions about microbial degradation – and in fact, it may vary substantially in the Gulf at any one time."

The Woods Hole scientists confirmed the plume's existence, measuring more than 1,100 meters below the surface, with crude stretching out over a minimum distance of 35 kilometers from the wellhead.

Reddy added that the plume did not appear as a chocolate mousse-like concentration.

"The water samples, when we’re right in the plume, look like spring water – and you certainly didn’t see any oil droplets, and you certainly didn’t smell it," he said.

"But that doesn’t mean that there’s no detectable oil."

More work planned

Scientists from Woods Hole said their study only amounted to a two-week snapshot of the plume in June. They refused to say what effects it may have on the ecosystem – and Reddy said more studies are in the pipeline, including some that focus on whether microbes are consuming the oil.

"Microbes eat compounds like we eat at a buffet," he said. "They like some compounds better than others. They leave behind a fingerprint of what they chose to eat.”

As the new study indicates, the Berkeley scientists succeeded in detecting that fingerprint. Scientists involved in the Woods Hole study did not register markedly lower levels of oxygen that would suggest the presence of bacteria. But Terry Hazen, lead author of the latest report, said he believes the bacteria didn't require large amounts of oxygen to eat the oil in the first place.

"These bugs have been adapted to using oil as a carbon source over millions of years because the Gulf of Mexico receives the equivalent of more than an Exxon Valdez spill every single year – and it's been doing that for millions of years from natural seeps," he said.

The spill's environmental toll

Hazen said it is difficult to predict how this might affect marine life in the Gulf.

Meanwhile, the oil industry has remained mum on the topic: the American Petroleum Institute, which represents oil companies in Washington, D.C., said commenting on the oil spill's possible biological effects would only amount to speculation at this point.

Sylvia Earle, an oceanographer and the former chief scientist for the U.S. National Oceanic and Atospheric Administration, was also reluctant to predict which species might be hurt by the spill. She said that wildlife populations close to the sites of other major spills have suffered in the past, adding that we may never know just what has been lost.

"The deeper you go, the less we know," Earle said. "We do know that there are deep corals, but because all of the Gulf hasn't been surveyed, we have a spotty record – but we know that they're there."

"Where we've looked, we've found them," she added. "Some of these are thousands of years old."

A wake-up call

The oceanographer worries that the oil and the chemicals added to break-up the oil will push a weakened ecosystem to the brink. The Gulf of Mexico already suffers from dead zones – areas where oxygen levels are so low that aquatic life can't survive there. Earle hopes the BP oil spill will serve as a wake-up call, alerting the public to the need to save the seas.

"The ocean is the cornerstone of our life-support system," she said. "It drives the chemistry of the planet. It shapes the way the world works – from the temperature, to oxygen in the atmosphere, to the carbon cycle, the nitrogen cycle."

"Modify the ocean, and you've modified everything," Earle said.

Regardless of whether the BP oil spill majorly modifies marine life, many are calling for continued monitoring. They believe problems, just like the oil plume, could be lurking just under the surface.

Author: Laura Iiyama (arp)
Editor: Cyrus Farivar