The 2010 Gulf oil spill coated the seafloor of the Gulf of Mexico in a “bathtub ring” of oil nearly three times the size of New York City, according to a report released last week in the Proceedings of the National Academy of Sciences.

The spill, continuing unabated for three months of 2010, was the worst environmental catastrophe in US history. Eleven crewmembers aboard the Deepwater Horizon rig were killed in the initial explosion, and an estimated 5 million barrels of crude oil leaked into the gulf, producing an oil slick clearly visible from space. At every step, British Petroleum, backed to the hilt by the Obama administration, sought to cover up the extent of the spill and minimize its own financial liabilities.

An estimated 2 million barrels of oil released during the spill remained trapped in a miles-long deep-water plume. However, it is still not fully understood where the oil from this plume ultimately ended up.

Researchers analyzed the concentrations of hopane, a degradation-resistant compound present in the crude oil released from the Macondo well, in sediments from several hundred locations around the area of the spill. They found the highest levels of concentration within 25 miles of the spill, in a southwesterly direction, consistent with the direction of the plume during the spill. Based on their analysis, they concluded that between 4 and 31 percent of all oil trapped in the underwater plume fell within an area of 1,250 square miles, which the study describes as a “bathtub ring.”

Christopher Reddy, a co-author of the study and director of the Coastal Ocean Institute at Woods Hole Oceanographic Institution, told the World Socialist Web Site that the plume oil in the seafloor sediment had been caught by geographic features. “The oil is moving near the bottom of the ocean, which is not absolutely flat. In some places there were enough features on the bottom of the ocean floor that the oil hit a side and stuck, similar to a bathtub.”

The degradation of the oil itself prevented researchers from chemically matching it to the Macondo oil. However, the high concentration of hopane in the uppermost levels of sediment, thousands of times higher than levels consistent with natural buildup, indicates that it had been deposited recently.

The researchers stressed that their count of the amount of oil that fell to the sea floor is a minimum estimate, given the heterogeneous distribution of the oil deposits, as well as the fact that many oily and suspected oily areas were not sampled as part of the study.

Researchers also discovered that deep sea coral lay inside the contaminated region, meaning that they were very likely damaged. This substantiates earlier studies, which found that the oil spill seriously damaged coral in the Gulf of Mexico.

Although the study has shed new light on the fate of the sub-surface oil released by the spill, there is still a considerable amount of oil that remains unaccounted for. Complicating matters, according to the study, is uncertainty as to the effects of chemical dispersants, widely used during the cleanup effort. Corexit 9500, a dispersant known to be toxic and banned in Britain, was used in unprecedented quantities in order to break up and submerge the surface oil, away from the prying eyes of the public.

“Unfortunately, they didn’t set up any parallel experiment that could shed some light on the role of dispersants,” Reddy told the WSWS . “There isn’t a lot of published work on dispersants, there really isn’t. And I don’t know why. There isn’t a lot of true blue field data that could give you a lot a data.”

BP denounced the study in statements to the media. Spokesman Jason Ryan, director of media affairs for the Gulf Coast, told the Associated Press, “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.” This is a sleight of hand, as a chemical analysis of the oil is now impossible, four and a half years after the initial spill.

The study cuts across ongoing attempts by BP to portray itself as a victim of ax-grinding special interest groups. Last week BP spokesman (and former press secretary for the US Department of Defense) Geoff Morrell penned an editorial in Politico titled “No, BP Didn’t Ruin the Gulf,” arguing that the Gulf of Mexico had already largely recovered from the oil spill. Citing the supposed “inherent resilience” of the Gulf’s ecosystem, he declared that most of the oil had already been broken down by microbes. He went on to blame “advocacy groups” for attempting to “cherry-pick evidence and promote studies that paint an incomplete and inaccurate picture.”

In fact, it is BP that has attempted to paint an “incomplete and inaccurate picture” of the oil spill since day one. With the help of the Obama administration, it deliberately concealed the true extent of the spill for weeks, prevented cleanup workers from speaking with the press, and harassed reporters attempting to cover the story.

BP is also attempting to extricate itself from its remaining liabilities from the spill. The company submitted evidence in federal court Wednesday as part of its effort to remove the claims a court-appointed settlement administrator had reached with individuals and businesses hurt financially by the oil spill.

The company is arguing that Patrick Juneau, the administrator, failed to disclose a conflict of interest before accepting the position, claiming that he had previously been involved in litigation against BP on behalf of oil spill claimants. Juneau denies the accusations, and insists that he was merely a liaison for the state of Louisiana.

The company has thus far met with limited success in the case, and the evidence submitted in court Wednesday is highly circumstantial. More fundamentally, the alleged conflict of interest of Juneau is merely the latest in a series of pretexts concocted by BP in order to back out of a settlement that it had fully agreed to in 2012. The company’s clear strategy is to use the complexity of the case to draw out the process as long as possible, in the hopes of eventually forcing a lesser settlement.