BP oil spill left 'bathtub ring' of oil across the Gulf floor

WASHINGTON, Oct. 28 (UPI) —

A study published Monday claimed the 2010 BP oil spill left a "bathtub ring" of oil on the seafloor of the Gulf of Mexico about the size of Rhode Island.

The study, published in the Proceedings of the National Academy of Sciences, said the oil remains in "bathtub ring" formed from an oil-rich layer of water" on the Gulf’s continental slope. A second area known as the "fallout plume’ where suspended oil particles sank to underlying sediment” a mile deep.

The conclusions were formed after the researchers tested more than 3,000 samples of sediment from 534 locations in the Gulf for a constituent of crude oil known as chemical hepane, reports The Times-Picayune.

"We don’t know with certainty how the oil reached the bottom," said lead author of the study David Valentine, a professor of microbial geochemistry at UCSB. "We do provide hypotheses, that a combination of coagulation and bacterial growth drove the oil into a floc form and facilitated particles or droplets sinking to the seafloor. Some of the oil was certainly eaten by bacteria, and other components dissolved to the water."

BP criticized the research, saying the study did not take into account some key factors.

"The authors failed to identify the source of the oil, leading them to grossly overstate the amount of residual Macondo oil on the sea floor and the geographic area in which it is found," BP said in a statement to NBC News. "Instead of using rigorous chemical fingerprinting to identify the oil, the authors used a single compound that is also found in every natural oil seep in the Gulf of Mexico, causing them to find false positives all over the sea floor."

They added the mapping technique used by researchers "dramatically" overestimated the area affected.

Prosecutors in the BP oil spill case said a total of 4 million barrels of oil spilled into the Gulf after the Deepwater Horizon explosion, affecting 16,000 miles of coastline and killing 8,000 animals. BP was found guilty of gross negligence and the court gave indications the company may end up paying billions of dollars in fines.