Study shows deepwater oil plume in Gulf degraded by microbes

In the aftermath of the explosion of BP's Deepwater Horizon drilling rig in the Gulf of Mexico, a dispersed oil plume was formed at a depth between 3,600 and 4,000 feet and extending some 10 miles out from the wellhead. An intensive study by scientists with the Lawrence Berkeley National Laboratory (Berkeley Lab) found that microbial activity, spearheaded by a new and unclassified species, degrades oil much faster than anticipated. This degradation appears to take place without a significant level of oxygen depletion.

Microbes have degraded to undetectable levels virtually all of the oil in the deepwater plume that resulted from the BP oil spill in the Gulf of Mexico, a study by Berkeley Lab researchers has shown. (Image from Hoi-Ying Holman group)

Microbes are degrading oil in the deepwater plume from the BP oil spill in the Gulf, a study by Berkeley Lab researchers has shown. (Image from Hoi-Ying Holman group)

''Our findings show that the influx of oil profoundly altered the microbial community by significantly stimulating deep-sea psychrophilic (cold temperature) gamma-proteobacteria that are closely related to known petroleum-degrading microbes,'' says Terry Hazen, a microbial ecologist with Berkeley Lab's Earth Sciences Division and principal investigator with the Energy Biosciences Institute, who led this study. ''This enrichment of psychrophilic petroleum degraders with their rapid oil biodegradation rates appears to be one of the major mechanisms behind the rapid decline of the deepwater dispersed oil plume that has been observed.''

The uncontrolled oil blowout in the Gulf of Mexico from BP's deepwater well was the deepest and one of the largest oil leaks in history. The extreme depths in the water column and the magnitude of this event posed a great many questions. In addition, to prevent large amounts of the highly flammable Gulf light crude from reaching the surface, BP deployed an unprecedented quantity of the commercial oil dispersant COREXIT 9500 at the wellhead, creating a plume of micron-sized petroleum particles. Although the environmental effects of COREXIT have been studied in surface water applications for more than a decade, its potential impact and effectiveness in the deep waters of the Gulf marine ecosystem were unknown.

Analysis with Berkeley Lab's phyloChip, a DNA-based microarray, revealed the dominant microbe in the dispersed Gulf of Mexico oil plume was a new species, closely related to members of Oceanospirillales family. (Image from Terry Hazen group)
Analysis with Berkeley Lab's phyloChip revealed the dominant microbe in the dispersed Gulf of Mexico oil plume was a new species, closely related to members of Oceanospirillales family. (Image from Terry Hazen group)