U.S. experts confirm undersea oil from BP well

HOUSTON (Reuters) - U.S. experts investigating reports of undersea oil plumes emanating from BP Plc's stricken well in the Gulf of Mexico on Tuesday confirmed the presence of low levels of oil below the surface.

"NOAA is confirming the presence of very low concentrations of subsurface oil," Jane Lubchenco, administrator of the National Oceanic and Atmospheric Administration, told a briefing in Washington.

It was the first government confirmation of undersea oil near BP's blown-out well a mile beneath the ocean. Previously, both NOAA and BP have played down the possibility of undersea plumes.

When university researchers aboard the Pelican research ship last month reported finding an underwater plume roughly 20 miles long, NOAA issued a statement criticizing the findings as "misleading, premature and, in some cases, inaccurate."

BP officials have said that oil from the well rises to the surface because it is lighter than water. "There aren't any plumes," BP Chief Executive Tony Hayward said on May 30.

But after analyzing underwater samples gathered by researchers aboard the University of South Florida's research vessel, the Weatherbird II, a different conclusion emerged.

"The bottom line is yes, there is oil in the water column," Lubchenco said.

"NOAA is confirming the presence of very low concentrations of subsurface oil at sampling depths ranging from the surface to 3,300 feet at locations 40 and 42 nautical miles northeast of the well site and another sampling station at 142 nautical miles southeast of the wellhead," Lubchenco said.

The oil is "in very low concentrations" around 0.5 parts per million," and other NOAA research ships are in the Gulf to gather additional samples, she said.

Undersea oil depletes the water's oxygen content and threatens marine life like mussels, clams, crabs, eels, jellyfish and shrimp.

One researcher who recently studied the undersea oil aboard the NOAA research ship Thomas Jefferson said the oil detected south of the spill site appeared to be in small concentrations.

"These are not like rivers of oil flowing down deep," said Daniel Torres, a scientist with Woods Hole Oceanographic Institution in Massachusetts. "We're detecting pretty low levels."

NOAA has been trying to "fingerprint" the oil to confirm that it came from the BP well. Surface samples taken 40 miles northeast of the well were "consistent with the BP oil spill," but hydrocarbons from samples taken 42 miles and 162 miles from the well "were in concentrations too low to do the actual fingerprinting," Lubchenco said.

The U.S. government and BP have concentrated their efforts on corralling the oil that floats to the surface and washes ashore in what is the worst oil spill in U.S. history.

But the government has little experience in dealing with subsea oil, said Coast Guard Admiral Thad Allen, the top U.S. official overseeing the cleanup effort.

"We have not generally done subsurface responses," Allen told the news conference. "In my own personal experience I have not dealt with it."

BP has sprayed about 1 million gallons (3.8 million liters) of chemical dispersant on oil at the ocean surface and wellhead, which causes the oil to either dissipate or sink to the ocean floor.

Scientists involved in the studies will testify on Wednesday before a House of Representatives Energy and Commerce Committee panel that is probing the spill.

Among those testifying will be Samantha Joye, a University of Georgia marine sciences professor who last month reported finding a plume roughly 20 miles long, six miles wide, and 100 feet thick.

It could take years to assess the impact of the spill on underwater life, Joye said.

"When you interfere with the natural processes in a system, when you alter the carbon cycle and the oxygen cycle, it's very likely that impacts will cascade up the food web to the top predators," she said.

(Additional reporting by Jeffrey Jones in Calgary and Tom Brown in Miami; editing by Mohammad Zargham and Alan Elsner)