Finding Spilled Gulf Oil

Tuesday, February 3, 2015 @ 03:02 PM gHale

After 200 million gallons of crude oil spilled into the Gulf of Mexico after the Deepwater Horizon disaster, the government and BP cleanup crews had a hard time locating where remnants of the spill went.

It now appears at least 6 million to 10 million gallons are in the sediment on the Gulf floor, about 62 miles southeast of the Mississippi Delta, said Florida State University Professor of Oceanography Jeff Chanton in a new study.

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“This is going to affect the Gulf for years to come,” Chanton said. “Fish will likely ingest contaminants because worms ingest the sediment, and fish eat the worms. It’s a conduit for contamination into the food web.”

The study details how oil caused particles in the Gulf to clump together and sink to the ocean floor.

The researchers used carbon 14, a radioactive isotope as an inverse tracer to determine where oil might have settled on the floor. Oil does not have carbon 14, so sediment that contained oil would immediately stand out.

Chanton then collaborated with Tingting Zhao, associate professor of geography at Florida State, to use geographic information system mapping to create a map of the oiled sediment distribution on the sea floor.

In the short term, the oil sinking to the sea floor might have seemed like a good thing because the water clarified, and the oil ended u removed from the water, Chanton said. But, in the long term, it’s a problem.

Less oxygen exists on the sea floor relative to the water column, so the oiled particles are more likely to become hypoxic, meaning they experience less oxygen. Once that happens, it becomes much more difficult for bacteria to attack the oil and cause it to decompose, Chanton said.

Chanton’s research ended up supported by the Florida State University-headquartered Deep-C Consortium as well as the Ecogig consortium, centered at the University of Mississippi. The work received funding from the Gulf of Mexico Research Institute created to allocate the money made available to support scientific research by BP.

His previous research examined how methane-derived carbon from the oil spill entered the food web.

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