August 20, 2010 in Nation/World

Invisible oil plume could be dangerous to marine life

Huge strand may linger 3,000 feet below surface of Gulf for months
Seth Borenstein Associated Press
 

WASHINGTON – The oil is there, at least 22 miles of it. You just can’t see it.

A lot of the crude that spewed from BP’s ruptured well is still in the Gulf of Mexico, but it’s far below the surface and invisible. And it’s likely to linger for months on end, scientists said Thursday in the first conclusive evidence of an underwater plume of oil from the disaster.

The plume consists of droplets too small for the eye to see, more than a half-mile down, said researchers who mapped it with high-tech sensors.

Scientists fear it could be a threat to certain small fish and crustaceans deep in the ocean. They will have plenty of time to study it for answers.

In the cold, 40-degree water, 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 Ben Van Mooy of the Woods Hole Oceanographic Institution in Massachusetts, a co-author of the research, published online in the journal Science.

Earlier this month, top federal officials declared the oil in the spill was mostly “gone,” and it is gone in the sense that you can’t see it. But the chemical ingredients of the oil persist, researchers found.

Monty Graham, a scientist at the Dauphin Island Sea Lab in Alabama who was not involved in the new research, 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 degradation 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.

“This is a highly sensitive ecosystem,” said Steve Murawski, chief fisheries scientist for the federal agency NOAA. “The animals down at 3,300 to 3,400 feet grow slowly.” The oil not only has toxic components but could cause genetic problems even at low concentrations, he said.

Lubchenco said NOAA is “very concerned about the impact” of the oil below the surface and federal officials last week started more aggressive monitoring of it.

For much of the summer, the mere existence of underwater plumes of oil was the subject of a debate that at times pitted outside scientists against federal officials who downplayed the idea of plumes of trapped oil. Now federal officials say as much as 42 million gallons of oil may be lurking below the surface in amounts that are much smaller than the width of a human hair.

While federal officials prefer to describe the lurking oil as “an ephemeral cloud,” the Woods Hole scientists use the word “plume” repeatedly.

The study conclusively shows that a plume exists, that it came from the BP well and that it probably never got close to the surface of the Gulf of Mexico, Camilli said. It is probably even larger than 22 miles long, but scientists had to stop measuring because of Hurricane Alex.

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