A sea turtle swims through a muck of oxidizing oil mingling with chemical dispersants used by BP to break up oil in the Gulf of Mexico in this May 2010 photo — just a few weeks after the spill began. NICOLE BENGIVENO / NEW YORK TIMES
By Kate Spinner
BP succeeded in sinking the oil from its blown well out of sight — and keeping much of it away from beaches and marshes last year — by dousing the crude with nearly 2 million gallons of toxic chemicals. But the impact on the ecosystem as a whole may have been more damaging than the oil alone.
The combination of oil and Corexit, the chemical BP used to dissolve the slick, is more toxic to tiny plants and animals than the oil in most cases, according to preliminary research by several Florida scientists. And the chemicals may not have broken down the oil as well as expected.
Scientists reported some of their early findings last week at a Florida Institute of Oceanography conference at the University of Central Florida. The researchers were funded a year ago through a $10 million BP grant.
The initial findings require more research for scientists to reach definitive conclusions. But scientists said they were struck by the studies so far.
They added BP oil to a jar of sea water and saw all the oil float to the top. After adding a little Corexit to the mix, the entire bottle of water turned the color of dark coffee.
In theory, the chemically dissolved oil should be a feast for bacteria that would break down some of the most harmful products in the oil.
But the Corexit may not have done its job properly, said Wade Jeffrey, a biologist with the University of West Florida’s Center for Environmental Diagnostics and Bioremediation.
“So far — and this is very preliminary — we’re not seeing a big difference,” Jeffrey said. “The way we’re doing the experiment, the Corexit does not seem to facilitate the degradation of the oil.”
Additionally, the Corexit and oil mixture tends to be more toxic to phytoplankton — tiny microscopic plants — than the oil itself.
Jeffrey subjected water samples, mostly from the Pensacola region, to heavily diluted concentrations of oily water and oily water mixed with Corexit. Most of the time the mix of Corexit and oil was more toxic to the phytoplankton in the sample than oil alone. Additionally, the Corexit did not prompt the oil-eating bacteria in the samples to gobble the oil any faster.
Jeffrey worked with a concentration of 1 part per million of oil and a tenth of that concentration for Corexit. Higher doses of oil killed the phytoplankton immediately, leaving Jeffrey with nothing to observe.
To see whether Corexit is more effective at breaking down larger concentrations of oil, Jeffrey plans more experimentation without the phytoplankton.
A similar study showed toxic effects of oil and Corexit on larger species, including conch, oysters and shrimp.
Susan Laramore, assistant research professor at Florida Atlantic University’s Harbor Branch Oceanographic Institute, used somewhat degraded oil from tar mats collected by the Florida Fish and Wildlife Research Institute to conduct her research.
Not all of the results are in, but early evidence shows the oil and dispersant mixture to be more toxic than the oil alone.
“These results are backwards of what the oil companies are reporting,” Laramore said.
The findings raise questions about whether the federal government should have let BP use so much dispersant on the oil. The Environmental Protection Agency tried to force BP to use a less damaging product, but no other product was available in sufficient quantities.
The dispersant effectively kept a great deal of the oil at sea, where it was not easily visible to the public. Although as much as half the oil that spewed from the well — 186 million to 227 million gallons — is unaccounted for, plenty of it still washed ashore, from the border of Texas to the Florida Panhandle.
Reports and videos taken last week by scientist Dana Wetzel of Sarasota’s Mote Marine Laboratory also show that the marshes of Louisiana’s Barataria Bay remain heavily choked in oil.
Evidence also is growing that the Corexit did not degrade as promised. A study in January by scientists at Woods Hole Oceanographic Institute in Massachusetts indicated that Corexit applied at the well-head — some 800,000 gallons — did nothing to break up the oil and simply drifted into the ecosystem.
FIO researcher Wilson Mendoza similarly has found potential evidence that Corexit remains in the environment much longer than expected. Wilson, a doctoral candidate at the University of Miami’s Rosenstiel School for Marine and Atmospheric Science, is developing a fingerprint for the BP oil and the Corexit.
In testing 75 different water samples taken from around the Gulf of Mexico, some contained signatures identified for both the oil and the Corexit a year after the spill.
Mendoza is running another test, using equipment that can analyze substances at a molecular level to verify the findings.
“If some of the other teams found out that Corexit is actually toxic and if it’s still there after a year, then I suppose it could cause environmental problems to a lot of organisms in the Gulf of Mexico,” Mendoza said.