Washington: A 22-mile-long invisible mist of oil is meandering far below the surface of the Gulf of Mexico, where it will probably loiter for months or more, scientists reported Thursday in the first conclusive evidence of an underwater plume from the BP spill.
The most worrisome part is the slow pace at which the oil is breaking down in the cold, 40-degree water, making it a long-lasting but unseen threat to vulnerable marine life, experts said.
Earlier this month, top federal officials declared the oil in the spill was mostly "gone," and it is gone in the sense you can`t see it. But the chemical ingredients of the oil persist more than a half-mile beneath the surface, researchers found.
And the oil is degrading at one-tenth the pace at which it breaks down at the surface. That means "the plumes could stick around for quite a while," said study co-author Ben Van Mooy of the Woods Hole Oceanographic Institution in Massachusetts, which led the research published online in the journal Science.
Monty Graham, a scientist at the Dauphin Island Sea Lab in Alabama who was not involved in the study, said: "We absolutely should be concerned that this material is drifting around for who knows how long. They say months in the (research) paper, but more likely we`ll be able to track this stuff for years."
Late Thursday, federal officials acknowledged the deepwater oil was not degrading as fast as they initially thought, but still was breaking down "relatively rapidly." Jane Lubchenco, chief of the National Oceanic and Atmospheric Administration, said agency scientists and others were "working furiously" to come up with actual rates of biodegradation.
She noted a bright spot from the slow breakdown of the oil: Faster would mean a big influx of oil-eating microbes. Though they are useful, they also use up oxygen, creating "dead zones" that already plague the Gulf in the summer. Dead zones are not forming because of the oil plume, Lubchenco said.
The underwater oil was measured close to BP`s blown-out well, which is about 40 miles off the Louisiana coast. The plume started three miles from the well and extended more than 20 miles to the southwest. The oil droplets are odorless and too small to be seen by the human eye. If you swam through the plume, you wouldn`t notice it.
"The water samples when we were right in the plume look like spring water," study chief author Richard Camilli said. "You certainly didn`t see any oil droplets and you certainly didn`t smell it."
The scientists used complex instruments — including a special underwater mass spectrometer — to detect the chemical signature of the oil that spewed from the BP well after it ruptured April 20. The equipment was carried into the deep by submersible devices.
With more than 57,000 of these measurements, the scientists mapped a huge plume in late June when the well was still leaking. The components of oil were detected in a flow that measured more than a mile wide and more than 650 feet from top to bottom.
Federal officials said there are signs that the plume has started to break into smaller ones since the Woods Hole research cruise ended. But scientists said that wouldn`t lessen the overall harm from the oil.
The oil is at depths of 3,000 to 4,000 feet, far below the environment of the most popular Gulf fish like red snapper, tuna and mackerel. But it is not harmless. These depths are where small fish and crustaceans live. And one of the biggest migrations on Earth involves small fish that go from deep water to more shallow areas, taking nutrients from the ocean depths up to the large fish and mammals.
Those smaller creatures could be harmed by going through the oil, said Larry McKinney, director of Texas A&M University`s Gulf of Mexico research center in Corpus Christi.