Oil dispersant upshot — bacteria feasted after BP spill

By John Upton

During its Deepwater Horizon oil spill, BP wickedly used 1.8 million gallons of oil dispersants to hide the slick. The chemical cocktail known as COREXIT 9500 caused the crude oil to dissolve in water instead of float on its surface. Among other things, the move destroyed plankton communities and threw the Gulf of Mexico’s food chain into chaos.

But one of life’s most primitive forms benefited greatly from this poisonous approach.

Hydrocarbon-eating bacteria feasted on the oil and methane as it swirled around in the gulf’s water column. New research published in Environmental Science and Technology reveals that the bacteria consumed at least 200,000 tons of the stuff, converting some of it into biomass that passed up the food-chain while also releasing the greenhouse gas carbon dioxide. The feeding frenzy reached its peak nearly three months after the oil rig explosion killed 11 workers, the scientists found.

“Certainly, some of the hydrocarbons were respired to CO2,” John Kessler, a Rochester University professor who co-authored the paper, told me in an email. “But some of that oily food had to go into supporting an increase in the microbial population.”

TV news report on the impacts of oil dispersants on gulf plankton communities: