Last week the debate about the fate of oil in the gulf took, according to major media reports, an optimistic turn. Now Representative Ed Markey (D–MA) is raising questions about federal oversight of dispersant use in the gulf, and a Senate committee is holding a hearing on the issue on Wednesday.
But while scientists acknowledge that dispersants can have negative effects, they are generally more worried about the oil than the dispersants, as the oil is far more toxic and more than 100 times more of it has been released. At a briefing last week in Washington, D.C., scientists were cautiously supportive of the government's gutsy decision on 15 May to allow BP to squirt tens of thousands of gallons of dispersants a day a mile deep. More than a million gallons of Corexit have been released on the sea floor since, with another 800,000 gallons sprayed by plane on the surface—in what amounts to a major, unprecedented experiment. Overall, the researchers said the move saved vast areas of coastal ecosystems and greatly reduced the amount of oil that would need to be collected or burned. Dispersants break the oil into tiny molecules that present tens of thousands of times more surface area than normal crude to microbes to be eaten; the molecules also rise to the surface much more slowly than raw crude. Some 50 scientists at a workshop at Louisiana State University predicted these benefits from the dispersants in May, signaling their support for the decision the government had made; some dissenters led by Sylvia Earle have said it was too soon to declare it a success.
But scientists at last week's congressional briefing said say some important risks to the undersea environment remain:
- Oil drops could wreak havoc on tuna eggs and larvae. Atlantic bluefin tuna are now spawning in their warm gulf waters. How might the oil drops affect their food supply? Biologist Robert Diaz of the College of William and Mary in Williamsburg, Virginia, said scientists don't know. "Is the dispersed oil better or worse for the tuna—that's hard to judge," Diaz said.
By virtue of their size, small oil drops could be deadly. Dispersing the oil means breaking it into smaller drops, which can do
unexpected things—like get wedged into the layers of armor of baby crabs, a Tulane University scientist found, as ScienceInsider reported earlier this month. Although the oil has
yet to be detected in the bodies of the larvae, researchers don't know what effect it may have on the crabs and whether natural molting of their shells
could rid them of the pollutant. Had the decision been made not to disperse the oil under water, the oil would have largely remained on the surface
where "perhaps the larvae wouldn't see it," said Diaz.
By making the oil drops tiny—biologist Kenneth Lee of the Bedford Institute of Oceanography in Nova Scotia, Canada, estimated the dispersed oil drops are several hundred micrometers in size—they are far smaller than shrimp eggs or larvae, and that provides a new way for the pollutant to get into their cells. "Hopefully, [the oil] is diluted enough" that it's not affecting them much, said Diaz, although he has no data either way.