Globs of thick, gooey petroleum have washed ashore along the south Louisiana coast over the past week, landing on beaches and washing into marsh reeds. Oiled birds have been collected and dolphins and sea turtles have been found dead, though officials cautioned they were still conducting tests to determine whether the deaths resulted from the spill.
But the environmental impact that most worries experts along the coast is the kind they can't see. Some birds and sea mammals affected by the spill are likely to die far offshore and never be detected, scientists say. Oil from the mile-deep well may be collecting in underwater clouds, potentially endangering a cornucopia of life from the sea floor to the surface, preliminary sampling by university researchers suggests.
And more than 800,000 gallons of chemical "dispersants" sprayed onto the oil in a frantic attempt to keep the bulk of it offshore pose little-understood risks to organisms in the Gulf's depths, scientists and government officials say.
The dispersant that has been used in the largest amounts on this spill, Corexit 9500, is among the most toxic to certain organisms of all those approved by the Environmental Protection Agency for use in oil spills, according to EPA tests.
The big question is which poses a greater environmental risk: oil washing ashore, or a mixture of oil and dispersant at sea. "This is a Hobson's choice," said Steve Murawski, chief science adviser for NOAA's fisheries unit and one of the officials working to assess the spill's environmental damage. "We're in uncharted territory."
A research ship from the University of South Florida this week found what researchers believe is a plume of oil concentrated about 1,300 feet below the surface, said David Naar, an oceanographer at the university. Researchers are awaiting lab tests to confirm that what they saw in the water is oil, he said, but "indirect evidence suggests that that's the case." The suspected oil particles are invisible to the naked eye, which is worrisome, Mr. Naar said. "In other words, they have become dissolved in the water."
Comment: I won't be eating seafood for a long long time!