Not Just the Slick: Oil Plume Found Below Gulf's Surface

(May 14) -- Since the Gulf of Mexico oil spill began three weeks ago, most eyes and cameras have been focused on the widening, orange slick. But now, as experts argue that the flow rate could far exceed the government's estimate of 210,000 gallons a day, a team of independent scientists studying the water in and around the disaster zone have found another problem: stores of leaked oil lingering beneath the surface in long, stringy filaments and snowflake-like collections.

"It doesn't float right up on top as you would think," Raymond Highsmith of the National Institute for Undersea Science and Technology tells AOL News. "Some of it floats right under the surface, and some of it now looks like it's quite a ways down."

Highsmith and his team, formed by a joint venture between the University of Mississippi and the University of Southern Mississippi, had been planning a seafloor mapping expedition when news of the spill began to get worse and worse. Their focused turned immediately to what might be happening to the oil as it rushed out. Given the depth of the source, they figured the leaked hydrocarbons wouldn't take a direct path to the surface.

"What we wanted to try to find out more about was the fate of the oil," Highsmith says.

So they changed their plans at the dock, clearing their research vessel of instruments they no longer needed, and loaded it with ones that would let them study and sample the conditions below the surface. Highsmith says the team added an acoustic Doppler profiler to learn more about the sub-surface currents that might be moving the oil around and a sensor package that would analyze the salinity, temperature and oxygen levels at various depths, plus devices that would enable them to collect samples of sediment, oil and water.

After a brief delay -- the Coast Guard insisted that anyone heading to the accident undergo hazmat training -- the crew motored straight to the site. "We thought it might be restricted but it wasn't," Highsmith says. "We thought they probably wouldn't let us in, but we weren't able to make contact with anyone who knew, so we just went. By the next morning we were right up next to the relief ships."

The scientists studied the area for several days before racing to shore to grab more instruments, including a fluoroscope that would enable them to detect the presence of oil at various depths in the water, and then hurried back.

The analysis of all the data they've collected thus far -- numerous samples have already been dispatched to labs -- will take time, but the group has already noted a few worrisome developments. Highsmith says the presence of all that oil could lead to bacterial blooms. These bacteria can eat up the oil, which is good for the clean-up, but they also produce a byproduct, hydrogen sulfide, that draws oxygen out of the water. Oxygen depletion would, in turn, endanger animals in the area. Sure enough, the group has already found that some of the oil-soaked spots beneath the surface registered lower levels of oxygen.

The team's larger suspicion about excess oil lingering in the deep has also been confirmed. The surface slick is not telling the whole story. "We've gotten some signals that sometimes the oil is near the surface, sometimes it's 40 meters down, and sometimes we don't see it at all," Highsmith says. "The oil is not evenly distributed, either horizontally or vertically. It's very patchy."

On the way to the surface, the oil is emulsified, or mixed with water, under pressure. It also passes through several different density layers and experiences shifting currents. Plankton and other organisms probably stick to it, Highsmith suggests. Plus, he says, there might be other influences the scientists haven't seen.

The team's mission ends Sunday, but Highsmith hopes they'll be able to get back out there again soon. A number of questions remain, including the volume of oil trapped beneath the surface, and its precise distribution. Highsmith says the group needs to continue studying the area to get answers: "That's the only way we're really going to learn what's happening is to follow it over time."