Aug. 17, 2010 -- While BP's well in the Gulf of Mexico remains plugged, new information suggests that plenty of oil remains in the waters and could be headed toward shore.
Two new studies from the University of Georgia and the University of South Florida found that almost 80 percent of the oil that leaked from BP's well is still out in the waters of the Gulf. Much of the oil has broken down into tiny particles, but researchers say those bits of crude are still toxic.
Watch "World News" for the latest on the oil spill tonight on ABC.
"My suspicion would be that a large fraction of this oil is still in the system," said Samantha Joye, a marine sciences professor at the University of Georgia.
The researchers' findings present a stark contrast to the White House's assessment of the situation earlier this month.
According to an estimate from the National Oceanic and Atmospheric Administration released by the White House on Aug. 4, 74 percent of the oil was gone.
"A report out today by our scientists shows that the vast majority of the spilled oil has been dispersed or removed from the water," President Obama said.
Carol Browner, the director of the White House Office of Energy and Climate Change Policy, told ABC's "Good Morning America" that day that the remaining oil would "continue to weather" and break down with the help of Mother Nature.
NOAA Defends BP Oil Spill Estimates
The government's top ocean scientist, NOAA Administrator Jane Lubchenco, defended her agency's estimates tonight on "World News with Diane Sawyer."
"We remain confident that the numbers we released earlier are very reasonable estimates," Lubchenco said. "We think 50 percent of the oil has disappeared from the system. Another quarter has been dispersed either chemically or naturally."
While Lubchenco acknowledged concerns over the effects of dissolved oil, she said that chemical dispersants had largely done their job.
"The whole idea of dispersants is to break up the oil into very small microscopic droplets so it can in fact biodgrade naturally," she said.
Scientists Concerned About Effects of Remaining Oil
Still, some scientists sid they are concerned about what they say are nearly invisible toxic clouds of oil, thousands of feet down.
"The concentrations that are currently out there in various locations are high enough to have a toxic effect on marine life," said Dr. Charles Hopkinson, with the University of Georgia's marine sciences program.
Researchers from the University of South Florida discovered oil littered on the sea floor of an underwater canyon just 40 miles from the Florida panhandle, a phenomenon that they attribute to the unprecedented use of large quantities of chemical dispersant.
Anecdotal reports seem to support the notion that the Gulf Coast is still far from clean.
Earlier today, the New Orleans Times-Picayune reported sightings of oil patches in the marshes of St. Bernard Parish. Off the coast of Plaquemines Parish, tar balls and oil sheen apparently turned up when the bottom of the bay was disturbed.