By Janet Raloff
Throughout the months-long 2010 BP oil spill in the Gulf of Mexico, scientists expressed surprise at the development and relatively speedy disappearance of giant plumes of subsea oil and gas that jetted from the wellhead and refused to surface. A new study explains how bacteria degraded the plumes so efficiently: A succession of hydrocarbon-noshing species mushroomed because their movable feasts were repeatedly replenished.
Only about 15 percent of the BP gusher floated up to form giant surface slicks, a second new study finds. Natural gas constituents and dissolvable chemicals amounting to twice that mass remained near the seafloor, creating the roving cloudlike hydrocarbon plumes on which the bacteria fed.
Besides natural gases, the plumes contained all of several highly volatile crude oil constituents released in the spill, including benzene and toluene. So cleanup workers who say they were sickened by benzene in the surface slick, as evidenced by elevated blood levels of the carcinogen, may have been exposed from other sources, concludes the leader of the second study, Thomas Ryerson of the National Oceanic and Atmospheric Administration in Boulder, Colo.
Both studies are being published online the week of January 9 in the Proceedings of the National Academy of Sciences.