oil-eating bacteria are consuming the oxygen
Interviewed on Saturday by satellite phone, one researcher aboard the Pelican, Vernon Asper of the University of Southern Mississippi, said the shallowest oil plume the group had detected was at about 2,300 feet, while the deepest was near the seafloor at about 4,200 feet.
“We’re trying to map them, but it’s a tedious process,” Dr. Asper said. “Right now it looks like the oil is moving southwest, not all that rapidly.”
He said they had taken water samples from areas that oil had not yet reached, and would compare those with later samples to judge the impact on the chemistry and biology of the ocean.
While they have detected the plumes and their effects with several types of instruments, the researchers are still not sure about their density, nor do they have a very good fix on the dimensions.
Given their size, the plumes cannot possibly be made of pure oil, but more likely consist of fine droplets of oil suspended in a far greater quantity of water, Dr. Joye said. She added that in places, at least, the plumes might be the consistency of a thin salad dressing.
Dr. Joye is serving as a coordinator of the mission from her laboratory in Athens, Ga. Researchers from the University of Mississippi and the University of Southern Mississippi are aboard the boat taking samples and running instruments.
Dr. Joye said the findings about declining oxygen levels were especially worrisome, since oxygen is so slow to move from the surface of the ocean to the bottom. She suspects that oil-eating bacteria are consuming the oxygen at a feverish clip as they work to break down the plumes.
While the oxygen depletion so far is not enough to kill off sea life, the possibility looms that oxygen levels could fall so low as to create large dead zones, especially at the seafloor. “That’s the big worry,” said Ray Highsmith, head of the Mississippi center that sponsored the mission, known as the National Institute for Undersea Science and Technology.
The Pelican mission is due to end Sunday, but the scientists are seeking federal support to resume it soon.
“This is a new type of event, and it’s critically important that we really understand it, because of the incredible number of oil platforms not only in the Gulf of Mexico but all over the world now,” Dr. Highsmith said. “We need to know what these events are like, and what their outcomes can be, and
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