Study finds massive amounts of oil from Deepwater Horizon disaster buried in Gulf of Mexico sediments

Oil spreading across the Gulf of Mexico in July, 2009. PHOTO COURTESY NOAA.
A NASA satellite image shows oil spreading across the Gulf of Mexico.

‘It’s a conduit for contamination into the food web …’

Staff Report

FRISCO — Five years after BP’s failed Deepwater Horizon drill rig spewed 200 million gallons of oil into the Gulf of Mexico, a significant amount of that oil remains buried in seafloor sediments.

A new study by a Florida State University researcher estimates that about 6 to 10 million gallons of oil are still there, perhaps decomposing slowly, but probably affecting Gulf ecosystems.

“This is going to affect the Gulf for years to come,” said researcher Jeff Chanton. “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,” he said.

Chanton’s research is outlined in the journal Environmental Science & Technology, detailing 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.

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

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 is supported by the Florida State University-headquartered Deep-C Consortium as well as the Ecogig consortium, centered at the University of Mississippi. The work was funded by the Gulf of Mexico Research Institute created to allocate the money made available to support scientific research by BP.

 

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