New evidence has cast fresh doubt on the Obama administration’s claim that most of the oil in the Gulf of Mexico has disappeared. On Thursday, a team of researchers confirmed the existence of a vast underwater oil plume stretching twenty-one miles from BP’s blown-out well. Christopher Reddy of the Woods Hole Oceanographic Institution said the amount of oil in the plume is unknown.

Christopher Reddy: “All I can tell you is that we found a plume. And I can’t tell you how much oil is in it, because we don’t have the values yet. We know there is a plume. We know its length. We know its shape. We know that we collected water samples in it. And when we have analyzed those samples, we’ll be able to constrain how much — what the inventory of those compounds are in there.”

The White House has claimed more than three-quarters of the oil has vanished from the Gulf. But speaking before the House Energy and Commerce subcommittee on Thursday, National Oceanic and Atmospheric Administration senior scientist Bill Lehr acknowledged that only ten percent of the oil has been cleaned up and that large quantities that evaporated or dispersed remain in the Gulf ecosystem. Florida State University oceanographer Ian MacDonald also said the actual amount of oil removed from the Gulf is around ten percent and predicted the spill will likely remain harmful for decades.

Ian MacDonald: “We really can only account for ten percent of the oil that was discharged, that 4.1 million barrels that was discharged, through burning and skimming. The balance of the oil remained in the environment. There may have been some ten percent that evaporated into the atmosphere, that is gone from the ocean, but the balance is still in the ocean. This oil has already degraded, has already evaporated and emulsified. It is going to be very resistant to further biodegradation. This oil is going to be in the environment for a long time. I think that the imprint of the BP release, the discharge, will be detectable in the Gulf of Mexico environment for the rest of my life. And for the record, I’m fifty-eight years old. So there’s a lot of oil, it’s not gone, and it’s not going away quickly.”