And scientists from the University of Georgia said the amount of oil that remains in the water could be 70 to 79 percent of the more than 4 million barrels of oil that escaped into the gulf.

Both reports again raise questions about the Obama administration's claim, made two weeks ago, that most of the oil spewed from BP's well is either gone or widely dispersed.

USF marine scientists conducting experiments in an area where they previously found clouds of oil have now discovered what appears to be oil in the sediment of a vital underwater canyon and evidence that the oil has become toxic to critical marine organisms, the college reported Tuesday.

In preliminary results, the scientists aboard the Weatherbird II discovered that oil droplets are scattered on sediment in the DeSoto Canyon, a critical spawning ground for commercially important fish species about 40 miles southeast of Panama City.

The oil isn't spread across the sandy bottom like a blanket, explained David Hollander. Instead, when the scientists shined ultraviolet light on the sediment samples, it picked up lots of dots from tiny oil droplets.

"They sparkled … like a constellation of stars," Hollander said.

USF's scientists also found that the oil droplets were toxic to some phytoplankton, microscopic plants that form the base of the gulf's food chain, as well as some bacteria. The oil doesn't accumulate within the plankton, but rather kills it.

If the droplets wipe out enough phytoplankton, it could alter the food supply for larger creatures such as fish and crabs in the same way a cattle pasture that loses all its grass alters the food supply for steak fans.

The discovery of oil droplets in DeSoto Canyon spells potential bad news for the areas of Florida's Gulf Coast that escaped the tar balls and liquid oil that tainted the Panhandle, said USF oceanographer Robert Weisberg. That's because right now cold water from the deeper part of the gulf is "upwelling" across the continental shelf and headed for coastal areas, Weisberg said.

"As water … makes its way across the shelf, those waters will eventually be at the beach along Florida's west coast, here and at points farther south, along with whatever is in the water," he explained.

BP vice president Ray Dempsey said the latest USF findings "are preliminary conclusions that require some further review. But we want the answers just as much as anyone else. Our aim is to restore the environment to the way it was."

The findings come two weeks after President Barack Obama's top energy adviser, Carol Browner, touted a new government report that she said showed that "more than three-quarters of the oil is gone. The vast majority of the oil is gone."

The team from Georgia analyzed the federal report in its research.

"The idea that 75 percent of the oil is gone and of no concern for the environment is just absolutely incorrect," said Charles Hopkinson, a director of Georgia Sea Grant and marine science professor at the University of Georgia, who co-wrote the report.

Two calculations explain the bulk of the difference. The Georgia report tossed out 800,000-plus barrels BP managed to pipe directly from the well after it had fitted a sealing cap on the gusher — 17 percent of the well's estimated flow — arguing that oil had never actually "spilled" into the gulf.

More significantly, the report also dramatically reduced the amount of oil estimated to have evaporated, to 7 to 12 percent from the federal study's 25 percent.

The federal government's evaporation estimate was based on a standard accepted by industry experts and researchers for light sweet crude in the warm gulf. But Hopkinson argued that the percentage is invalid because much of the oil remains deep beneath the surface, trapped under dense temperature and salinity layers that would dramatically limit evaporation.

One of the institutions that first found those underwater plumes of oil was USF. The area in DeSoto Canyon that the Weatherbird II explored on a 10-day cruise this month was also one of the places where USF found plumes and conclusively linked them with Deepwater Horizon.

However, Hollander and his colleague John Paul, in speaking with reporters Tuesday, stopped short of pointing a finger at Deepwater Horizon as the source of the oil they had found in the canyon. Tests are still being run, they said.

Still, they said, the findings underline the persistent concerns that spraying chemical dispersants deep beneath the water's surface may have created a greater peril for the gulf and its marine life.

Rather than rising to the top of the gulf, where the water is warm and deterioration and evaporation are rapid, the oil spread through colder waters where it has persisted.

At this point, no one knows how long it will take for the oil to deteriorate so it's no longer toxic. However, Hollander said, recent studies have found indications that the rate is "orders of magnitude slower" in the colder, deeper parts of the gulf.

In hindsight, Hollander said, "there's risks that were taken that could have been avoided" by not spraying the dispersants directly at the gushing wellhead.

The amazing thing, he said, is that the disaster has been going on since April "and we're now addressing these first-order questions."

Information from McClatchy Newspapers was used in this report.

www.tampabay.com/news/education/college/article1115706.ece

August 19, 2010