Dispersants used in BP disaster hampered growth of oil-eating bacteria


The chemicals used to clean up oil spills may actually weaken nature’s ability to do the cleaning itself. 

New research reveals that the oil dispersants sprayed across the Gulf of Mexico during the 2010 BP Deepwater Horizon disaster can kill or inhibit the growth of oil-eating microbes, including naturally-occurring bacteria that rapidly consume oil that dispersants only break apart. 

“When you use dispersants, you knock out the best and the brightest of the oil degraders,” said Samantha Joye, a marine scientist with the University of Georgia.

Joye and other scientists presented research detailing dispersants’ effects on marine microbes at the Gulf of Mexico Oil Spill and Ecosystem Science Conference in New Orleans last week.

The Deepwater Horizon drilling platform off the Louisiana coast spewed oil into the Gulf of Mexico for nearly three months. Releasing 200 million gallons, it’s considered the world’s largest oil disaster.

To combat the oil’s spread, BP used two types of dispersant, Corexit 9500 and Corexit 9527, both manufactured by Nalco Environmental Solutions. Nearly 1 million gallons was dropped by air, and another 770,000 gallons was injected into the damaged wellhead about a mile under the water’s surface. It was the first time dispersants had been used on a large scale and in proximity to people. 

BP’s assertions that dispersants posed no health or safety risks are contradicted by a spate of new research. In September, the National Institutes of Health published a study that validated long-held concerns that dispersants caused a host of illnesses. The study said disaster-response workers exposed to dispersants suffered shortness of breath, coughing and lung, eye and skin irritation. 

Other studies indicate that dispersants harmed fish, crab and other marine life. Deep-sea coral, which provide important habitat for many Gulf species, suffer more from dispersants than oil alone, new research found. 

Also becoming clear is how fast and effective naturally-occurring bacteria was in eating up the oil. In 2013, scientists learned that the disaster spurred a 10-fold increase in several types of bacteria that devour oil molecules. The bacteria boom may explain why so much of the oil disappeared within weeks of capping the Deepwater Horizon well. 

“The bacteria degraded oil in a very fast way,” said Steffen Hackbusch, a biochemist at the Hamburg University of Technology in Germany.

But add dispersants, and the feasting stops. 

“The research clearly shows that whenever dispersants are involved, (the bacteria) die,” said Hackbusch, who also presented research at the oil spill conference. “It is toxic to the organism.”

Joye and Hackbusch conducted lab experiments that exposed microorganisms to various combinations of crude oil and dispersants. 

“I call them my torture experiments,” Joye said. “We see where they start to suffer.”

The microscopic oil-eaters don’t just suffer when exposed to Corexit dispersants, they…



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