Scientists Track Down the 'Missing' Oil from the Deepwater Horizon Spill in the Gulf of Mexico

After 200 million gallons of crude oil spilled into the Gulf of Mexico during the disastrous Deepwater Horizon oil spill, not all of the oil was accounted for. Now, a new study has found out exactly where all of the oil went--and how it might impact the ocean in the future.

Researchers have long known that a lot of oil sank to the ocean floor. To track down its whereabouts, the researchers used geographic information system mapping to create a map of the oiled sediment distribution on the sea floor. More specifically, they used carbon 14, a radioactive isotope, as an inverse tracer to determine where the oil settled on the floor; oil does not have carbon 14, so sediment that contained oil would immediately stand out.

So what did they find? It turns out that six to 10 million gallons of oil are buried in the sediment of the Gulf floor, about 62 miles southeast of the Mississippi Delta.

"This is going to affect the Gulf for years to come," said Jeff Chanton, one of the researchers, in a news release. "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."

Less oxygen also exists on the sea floor relative to the water column. This means that oiled particles are more likely to become hypoxic, which means they experience less oxygen. When that happens, it becomes more difficult for bacteria to attack the oil and cause it to decompose.

The findings reveal that the oil spill will likely impact the Gulf of Mexico for some time to come. It also reveals the importance of monitoring ocean organisms and testing them for contaminants.

The findings are published in the journal Environmental Science & Technology.

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