VENICE, La. — Disputing scientists' claims of large oil plumes suspended underwater in the Gulf of Mexico, BP PLC's chief executive on Sunday said the company has largely narrowed the focus of its cleanup to surface slicks rolling into Louisiana's coastal marshes.
During a tour of a BP PLC staging area for cleanup workers, CEO Tony Hayward said the company's sampling showed "no evidence" that oil was suspended in large masses beneath the surface. He didn't elaborate on how the testing was done.
Hayward said that oil's natural tendency is to rise to the surface, and any oil found underwater was in the process of working its way up.
"The oil is on the surface," Hayward said. "There aren't any plumes."
Scientists from several universities have reported plumes of what appears to be oil far from the site of BP's leaking wellhead, which is more than 5,000 beneath the surface.
Those findings – from the University of South Florida, the University of Georgia, Southern Mississippi University and other institutions – were based on video images and initial observations of water samples taken in the Gulf over the last several weeks. They continue to be analyzed.
One researcher said Sunday that their findings are bolstered by the fact that scientists from different institutions have come to similar conclusions after doing separate testing.
"There's been enough evidence from enough different sources," said marine scientist James Cowan of Louisiana State University, who reported finding a plume last of oil last week about 50 miles from the spill site. Cowan said oil reached to depths of at least 400 feet.
An even larger plume – 22 miles long, six miles wide and more than a thousand feet deep – was reported by the University of South Florida.
"We stand behind it," said William Hogarth, dean of the school's College of Marine Science. Hogarth, the former head of the National Marine Fisheries Service, said laboratory results are due this week.
A third scientist, LSU chemist Ed Overton, said simple physics sides with BP's Hayward. Since oil is lighter than water, Overton said it is unlikely to stay below the surface for long.
But Hogarth and Cowan said BP's use of chemical dispersants to break up the oil before it reaches the surface could reduce its buoyancy, keeping it in deeper water.
An estimated 18 to 40 million gallons of oil have been unleashed since BP's Deepwater Horizon platform exploded and sank last month, killing 11. With the undersea leak now expected to continue spewing oil until August, Hayward said the cleanup effort could last for months or even years.
The embattled CEO spent only a few minutes on the subject of plumes on Sunday, concentrating instead on outlining his company's cleanup efforts.
"The fight on this battlefield today is in Louisiana," he said.
Calls to BP seeking more information on how they tested for the underwater plumes weren't immediately returned.