How Microbes Teamed to Clean Gulf

(by Gautum Naik, The Wall Street Journal, WSJ.com) – A … combination of ravenous bacteria, ocean currents and local topography helped to rapidly purge the Gulf of Mexico of much of the oil and gas released in the Deepwater Horizon disaster of 2010, researchers reported [last month].

After spewing oil and gas for nearly three months, the BP PLC well was finally capped in mid-July 2010. Some 200,000 tons of methane gas and about 4.4 million barrels of petroleum spilled into the ocean. Given the enormity of the spill, many scientists predicted that a significant amount of the resulting chemical pollutants would likely persist in the region’s waterways for years.

According to a new federally funded study published Monday by the National Academy of Sciences, those scientists were wrong. By the end of September 2010, the vast underwater plume of methane, plus other gases, had all but disappeared. By the end of October, a significant amount of the underwater offshore oil—a complex substance made from thousands of compounds—had vanished as well.

“There was a lot of doomsday talk,” said microbiologist David Valentine of the University of California, Santa Barbara, and co-author of the study, published in Proceedings of the National Academy of Sciences. But it turns out “the ocean harbors organisms that can handle a certain amount of input” in the form of oil and gas pollutants, he said.

A year ago, Dr. Valentine and other scientists published a paper describing how bacteria that feed on naturally occurring oil and gas leaks underwater had apparently devoured much of the toxic chemicals released in the BP spill. That federally funded study, published in the journal Science, triggered disbelief among other researchers who questioned whether microbes could gobble up that much gas and oil so quickly.

Dr. Valentine and colleagues have now used a computer model to explain just how that scenario might have played out, though some scientists remain skeptical.

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The model showed that the topography in the Gulf had played a vital role. Because the Gulf is bounded on three sides by land–north, east and west–the water currents don’t flow in a single direction as in a river. Instead, the water sloshes around, back and forth, as if it were trapped in a washing machine.

An initial population of bacteria encountered the spill near the BP well, its population grew, and then it was swept away by the ocean currents. But when the water circled back–that washing-machine effect–it was already loaded with these hungry bacteria, which immediately went on the attack again, mopping up another round of hydrocarbons. These repeated forays over the BP well, by the ever-growing bacterial populations, sped up the rate at which the methane and offshore oil got [eaten by the bacteria].

Dr. Valentine suggested that oil companies ought to ascertain the currents, water motion and native microbial community in the water before embarking on any major offshore drilling project. “Then, if there is an event, we’d be many steps ahead of understanding where the oil may go and what the environment’s response may be,” he said.

Ira Leifer, a petroleum geochemist also at UC Santa Barbara who co-wrote a rebuttal to the 2011 paper published in Science, said the latest study was limited because it was based on a computer model “which is only as good as the input or assumptions” on which it is based. He noted, for example, that the authors had neglected to include a discussion of whether the bacteria would run out of critical nutrients necessary for them to consume the oil and gas and reproduce.

The research was funded by the National Science Foundation, the Department of Energy and the Office of Naval Research.

Write to Gautam Naik at gautam.naik@wsj.com.

(NOTE: This article was first published in The Wall Street Journal on Jan. 10th.)

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