A new report published Monday in the Proceedings of the National Academy of Sciences shows that a massive layer of coagulated oil remains on the Gulf of Mexico’s seafloor nearly five years after the Deepwater Horizon sank and spilled some 5 million barrels of oil in the area.
The “bathtub ring,” a layer of water containing high levels of oil, covers 1,200 square miles about a half mile below the surface. The researchers also say that a “fallout plume” of oil particles sank into sediment as much as a mile below the surface. They measured the highest concentration of oil remains near BP’s Macondo well, from which the 2010 spill originated.
“I think people have been curious about what happened to the oil in the deep Gulf of Mexico,” lead author David Valentine told the Times-Picayune. “Now we have some handle on this question.”
BP released a statement Monday criticizing the report over the chemical fingerprinting used to identify the oil on the seafloor. “The authors used a single compound that is also found in every natural oil seep in the Gulf of Mexico,” the statement said, claiming that the scientists were presenting false positives.
Valentine refuted those claims, citing the sheer volume of the BP oil spill, which is considered the largest in the history of the petroleum history. “The discharge from the Macondo well simply swamped the signal from other sources in a clear and distinctive way that points right to the Macondo well as source,” he told the Times-Picayune. He also said that the oil was concentrated differently than a deposit of natural seepage would, and that it was such an anomalous amount in the area right near the Macondo well that there is a clear association.