WASHINGTON — As the magnitude of BP's oil spill becomes clearer, scientists fear that the volume of oil, the depth of the leak and the chemical dispersants the company is using will combine to threaten a vast array of undersea life for years.
At risk are such endangered species as Kemp's ridley sea turtles and the Atlantic bluefin tuna, as well as the Gulf of Mexico's 8,300 other creatures from plankton to birds. The contamination, some say, is likely to undo years of work that brought some wildlife, such as the brown pelican, back from the brink of extinction.
"It's probably going to be one of the worst disasters we've ever seen," said Paul Montagna, a professor of ecology at the Harte Research Institute for Gulf of Mexico Studies at Texas A&M University in Corpus Christi.
"Instead of creating a typical spill, where the oil goes to the surface and you can scoop it up, this stuff has been distributed throughout the water column, and that means everything, absolutely everything, is being affected," he said.
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Further complicating the toxic effects of the oil, the chemical dispersants — used as never before a mile below the surface — have changed the crude in ways that will keep it from breaking down.
The dispersants have modified the oil, keeping it in a form that's "much gooier and much oilier, and that has a lot of us worried, because it means the stuff is not going to degrade very easily," said James H. Cowan Jr., a professor of biological oceanography at Louisiana State University in Baton Rouge. Because of the high pressure deep underwater, it's harder for dispersants to break up the oil, he said.
"A lot of us suspect that we may be dealing with this for decades," Cowan said.
BP's use of the dispersants also is likely to keep the damage hidden.
Larry Crowder, a professor of marine biology at Duke University, said the dispersant, Corexit, had kept much of the oil off the beaches, making it "harder to get 'Film at 11' about the effects." Many species that are killed by the oil in the water will die and sink out of sight.
"That may be the preference of the oil companies: to keep the damage out of sight, out of mind," Crowder said.
Scientists said that at the seabed, where the gusher has spewed as much as 37 million gallons of crude since April, the world is like a refrigerator with the door shut: about 40 degrees and dark. Bacteria that degrade oil don't work well in those conditions.
"A lot of the technology that worked pretty well in shallow water we're finding — oops — there are some things we didn't know or think about," said Texas A&M's Montagna. "Obviously, there were no contingency plans."
BP's response plan for a spill in the Gulf didn't anticipate oil staying underwater. It said that measurements would be made on the surface to calculate the size of the spill.
Layers of oil reach out in all directions under water, LSU's Cowan said, some deep, where they degrade slowly, and others moving toward the surface. One layer is a few hundred feet down in the water and 300 feet thick, he said.
He and his research team have been out checking the reefs with remotely operated vehicles. Most of the oil they've seen is near the shore, he said, "but we now think we're beginning to see some oil on the reef environment in a little deeper water."
The rock reefs are home to creatures such as whip corals, anemones and sea lilies, as well as colorful fish that are also found in the Caribbean. "Reefs are very, very vulnerable to any type of toxicity," Cowan said.
The habitat of colorful tropical fish here is very specific and limited, "and it just so happens some of these habitats are in harm's way," he said. The spill could eliminate some of these fish from the northern Gulf.
Crowder of Duke said that one of the most serious threats was to the Atlantic bluefin tuna. The fish are down to about 1 percent of their former population, and some experts want to add them to the endangered species list, but there's been strong resistance because individual fish are so valuable.
Bluefin tuna spawn only in the Mediterranean Sea and in the vicinity of the spill in the Gulf of Mexico. The effects on eggs, larvae and adult fish might not be known until they show up in the population years later.
Kemp's ridley turtles nest mainly at Rancho Nuevo, Mexico. A smaller number nest on Padre Island National Seashore in south Texas.
The oil is still far from Rancho Nuevo, but when nesting season ends in late May or early June, the turtles will swim along the coastline from Mexico to Florida, right through the oil, Crowder said.
Protection of their nests and the turtle exclusion devices that fishermen use have helped to increase the number of nests from about 800 at a low point in the late 1980s to 7,000 to 8,000 a year now.
"I'd say they're a real success story, but the success could be blunted or reversed pretty seriously by an oil spill of this scale," Crowder he said. The real toll won't be known until reduced nesting is discovered, he added.
The National Oceanic and Atmospheric Administration reported that as of Wednesday, 228 sea turtles were seen in the spill area, including two small Kemp's ridley turtles that were covered with oil and were sent to the Audubon Aquarium of the Americas in New Orleans for care. One other oiled Kemp's ridley was found dead.
John Hewitt, the aquarium's director of animal husbandry, said his staff could care for large numbers of oiled sea turtles, but they might not be able to release the ones that recover right away.
"We'll have to wait until the Gulf is ready to support life again," he said. "It could be a long while."
Brown pelicans were removed from the endangered species list last year after a slow recovery since the 1970s, when their populations plummeted from the use of the pesticide DDT.
"The spill is going to be responsible for a big hit that puts them in jeopardy again, I think," said Stan Senner, the director of conservation science at the advocacy group Ocean Conservancy. Senner worked for seven years as the chief restoration planner for Alaska after the 1989 Exxon Valdez oil spill.
The Gulf oil spill could "prove to be a sort of tipping point in the life of a population like the Gulf of Mexico sperm whales. We just don't really know yet if that's how it plays out," Senner said.
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