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Gulf oil spill: Undersea oil 'clouds' confirmed in spill zone [Updated]

June 8, 2010 | 10:33 am

Scientists on a federal research vessel said Tuesday morning that they have confirmed a sub-sea concentration of hydrocarbons near the Deepwater Horizon leak site. The preliminary findings suggest that the undersea oil appears and disappears in a series of cloud-like concentrations -- instead of as a steady stream of oil, or plume, as early reports from university researchers suggested.

The federal researchers aboard the National Oceanic and Atmospheric Administration vessel Thomas Jefferson stressed that they could not conclusively say the oil is linked to the BP leak until water sample tests are completed. The initial findings were based on tests using sophisticated sound-monitoring and fluorescent scanning equipment that detects the presence of crude oil underwater.

NOAA researchers, joined by a University of New Hampshire expert and other outside scientists, detected the "clouds" of oil about 1,100 meters below the surface, 7 1/2 miles west-southwest of the Horizon leak. The clouds were dynamic -- some appeared on sensors at one point and then, later, did not register in the same location.

Separately, NOAA confirmed the existence of broad areas of sub-surface hydrocarbons as far as 142 nautical miles from the leak source, in depths from 50 meters to 1,400 meters (164 feet to 4,593 feet).

The announcement by the nation's weather and maritime science agency confirmed some of the data reported last month by University of South Florida researchers aboard the Weatherbird II research vessel. 

The three samples analyzed by the agency contained oil and polycyclic aromatic hydrocarbons, or PAH, in very low concentrations -- .5 parts per million of oil and in the parts-per-trillion range for PAH. They came from three areas: 40 and 45 nautical miles northeast of the wellhead, and 142 nautical miles southeast of the wellhead, which has been spewing an estimated 12,000 to 19,000 barrels of oil a day and possibly much more, since an April 20 explosion ripped through the Deepwater Horizon drill rig, claiming 11 lives.

Some forms of PAHs, which vary in chemical structure, can be toxic and carcinogenic. The Environmental Protection Agency has listed seven PAH compounds as possible human carcinogens.

NOAA "fingerprinted" the oil spilling from the BP well and concluded that the nearest samples were consistent with the crude spilling from the site. But the agency did not confirm the more distant sample's origin.

When the University of South Florida findings were reported by media outlets, NOAA cautioned against drawing conclusions until further study."We have always known there is oil under the surface; the questions we are exploring are where is it, in what concentrations, where is it going, and what are the consequences for the health of the marine environment?" NOAA administrator Jane Lubchenco said in a statement.

"This research from the University of South Florida contributes to this larger, three-dimensional puzzle we are trying to solve, in partnership with academic and NOAA scientists."

The drift of undersea hydrocarbons has drawn attention as BP undertakes an unprecedented use of chemical dispersants below and atop the sea surface to break up the oil. Scientists worry that the petroleum suspended in the water column will enter the food chain, affecting sea life as tiny as plankton and as large as whales. At least a third of the federal waters of the gulf have been closed to fishing, and the federal government continues to test seafood samples.

Ed Overton, a chemist who studies toxic spills at the School of the Coast and Environment at Louisiana State University, said he was not surprised that oil concentrations were being discovered. "There's a lot of oil out there," he said. "There is a lot of dispersed oil and these plumes are spreading it."
The unprecedented amount of dispersants that have been applied to the leaking well have broken down the oil and removed it from the surface. But the chemicals also cause oil droplets to fall into the gulf's water column and ultimately spread oil more readily around the region.
What's important to measure, Overton said, is the concentration of oil in the seawater. High concentrations of sub-surface oil have the effect of depleting oxygen, killing fish, microbes and other living things. "If it's parts per million, you are looking at a dead zone," Overton said. "If it's parts per billion then it's not so bad."

Louisiana State University's labs in Baton Rouge are analyzing samples taken from the research vessel Pelican, which discovered the first mass of hydrocarbons a few weeks ago. Since then, at least two academic research cruises encountered the same phenomenon.
Most recently a team from the University of South Florida found a sub-surface layer of what appeared to be hydrocarbons trailing in a 20-mile area.
At first BP and NOAA downplayed the presence of "plumes." But the federal agency has since launched its own research ship to study deep water effects from the leak.

Roger Zimmerman, a marine biologist who directs the Galveston Laboratory, part of NOAA's Fisheries Service, told the Los Angeles Times last month that the spill is a crucial habitat for a wide web of sea life:

"It's a significant ecosystem that goes from the bottom to the top waters," Zimmerman said. "This is a rich area in terms of biological productivity and diversity of animals. There's a lot of reproduction."

For more detailed information on the environmental effects of undersea oil, click here to read the full report by Los Angeles Times reporters Bettina Boxall and Alana Semuels.

-- Jim Tankersley, reporting aboard NOAA vessel Thomas Jefferson, and Julie Cart, reporting from Baton Rouge, La.

[For the record, 1:50 p.m.: An earlier version of this post said that NOAA researchers, joined by a University of New Hampshire expert and other outside scientists, detected "clouds" of oil about 1,100 feet below the surface, 7 1/2 miles west-southwest of the Horizon leak. In fact, the "clouds" were detected 1,100 meters below the surface.]