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Scientists still learning from Deepwater Horizon disaster

A sea turtle in the Gulf of Mexico surfaces to feed in 2010, swimming through oil mingling with chemical dispersants used to break up the spill. Although a great deal has been learned, some key questions are still unanswered.
Published Dec. 4, 2012

The Deepwater Horizon disaster happened in one of the worst places in the world for an oil spill — 5,000 feet below the surface in a body of water that scientists admitted they knew little about, where it could potentially ruin both the seafood and tourism industries that depended on it.

On Monday, more than two years later, some of the nation's top scientists — including the heads of three government agencies — published a comprehensive review of the scientific response to the disaster. One thing they found is that they still don't know nearly enough about the Gulf of Mexico to say how the spill affected it or how to be prepared for another.

Another is that they still don't know what the impacts dispersants such as Corexit — used during the 2010 disaster in ways it had never been used before — have had on a wide range of species in the gulf.

"The jury is still out on the environmental impacts," said Steve Murawski, formerly the chief federal fisheries scientist and now a University of South Florida marine science professor, who co-wrote one of the papers. "Much more work needs to be done."

One new study, released on Friday, found that the dispersant may have made the oil more toxic to wildlife than the oil alone would have been.

The Environmental Protection Agency had tested Corexit on fish and shrimp before clearing it for use in dealing with Deepwater Horizon. BP then sprayed the dispersant directly at the wellhead spewing oil from the bottom of the gulf, even though no one had ever tried spraying it below the water's surface before. It also used more of the dispersant than had been used in any previous oil spill, 1.8 million gallons, to try to break up the oil before it reached shore.

The new study by the Georgia Institute of Technology and the Autonomous University of Aguascalientes in Mexico looked at the impact the dispersant had on rotifers, a sensitive microscopic creature that's eaten by crabs, shrimp and small fish in the gulf. It found that combining the dispersant with the oil boosted the toxicity to rotifers by a factor of 52. Testing continues.

Despite that scientific uncertainty, Murawski said, the oil industry is so sold on Corexit that the companies that conduct similar deep-sea drilling projects have all stocked up on it to use at the next such disaster.

Among the other suspected impacts of the dispersant were the underwater plumes of oil droplets that USF scientists were instrumental in discovering. Future oil spill response plans should include a search for similar plumes, something that's not there now, Murawski said.

Monday's newly published papers also called for developing ways to capture oil from the ocean's surface that are more efficient than skimming and putting out booms — two techniques that failed to collect much oil when the waves got rough in the gulf.

They also called for setting up in advance a way to pay for rapid scientific assessments of future spills. The millions of dollars spent on assessing Deepwater Horizon's impact came in "a shotgun approach," Murawski said.

They urged a concerted effort to fill in continuing information gaps about the marine environment where deepwater drilling occurs.

"We need an adequate baseline," Murawski said, noting that the last publication on the diseases of fish in the gulf was from 1996. That has made it difficult to connect a spike in the occurrence of diseased fish near the Deepwater Horizon site with the oil spill itself. "It's very frustrating," he said.

Murawski said he met with oil industry scientists recently to ask for their help in getting corporate funding for a gulfwide environmental monitoring system — and met with sympathy but little else.

He said they asked how they could make a business case for backing such a system. "They kept saying, 'If the regulators don't require it, then why should we spend money on it?' "

Monday's studies did find that a lot of the scientific work done in haste during the spill turned out to be right, including a controversial pie chart showing where the oil had gone. According to the chart, "a quarter of the oil is still unaccounted for," Murawski said. "But we know where it is."

Some of it remains on the bottom of the gulf, buried under a few centimeters of debris and likely to be stirred up again by the creatures that like to burrow in the ocean bottom, he said. Some remains in the marshes of Barataria Bay, La., where research has shown the oil may be causing sickness and death among dolphins. And along parts of the gulf beaches, there's a strip of "tar pavement" just beneath the sand, Murawski said.

"When the hurricane (Debby) came, it washed the sand away and made it look like a paved highway out there," he said. That weathered tar "will be with us for a long time."

The papers published Monday were co-written by National Oceanic and Atmospheric Administration chief Jane Lubchenco, Department of Energy Secretary Stephen Chu and U.S. Geological Survey head Marcia McNutt, among other scientists, and were put out as part of a special issue of the Proceedings of the National Academy of Science.

Craig Pittman can be reached at


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