BP Oil Spill: Undersea Plumes Nowhere to Be Found as Tests Show Seafood to Be Safe

KENNER, La., July 30, 2010— -- On day 102 of the BP oil spill in the Gulf of Mexico, the oil is getting harder and harder to find, both on the ocean's surface and in the depths below.

For months, scientists monitored huge plumes of oil and dispersant deep beneath the waves. But now, they say, the plumes are nowhere to be found.

Watch "World News" for the latest on the Gulf oil spill tonight on ABC.

In the two weeks since the leaking well was capped, government and independent scientists have done extensive testing in the deep sea, and the results were not what they expected.

"We're finding hydrocarbons around the well, but as we move away from the well, they move to almost background traces in the water column," National Incident Cmdr. Adm. Thad Allen told ABC News.

Where could the undersea oil have gone? Today, many scientists across the Gulf Coast pointed to the same explanation -- deep sea bacteria called psychrophiles that have consumed the oil faster than anyone expected. The bacteria occur naturally in the waters of the Gulf, and when there's more oil present, they multiply to eat it.

"When a large amount of oil comes into the environment, then they quickly muster, if you will, and they can sometimes grow to 1,000-fold," said Jay Grimes, a professor of microbiology at the University of Southern Mississippi.

"They've been there for millions of years because of the fact that, for millions of years, we've had a large amount of natural oil seeping into the floor of the ocean," Grimes added.

Bacteria decompose the oil with a half-life of seven to 30 days, meaning that in that time period half of a plume could be consumed. In the following seven to 30 days, half of the leftover oil is eaten, and so on until all that's left is asphaltines, which form the basis of tar balls.

One of Grimes' students has been searching for oil on a research vessel for the last three days, finding no evidence of deep sea plumes.