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News Extra: US researchers discover role of microbes in remediating 2010 Gulf of Mexico oil spill

01 August 2017

For the first time, a research team at the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has identified all of the principal oil-degrading bacteria active in the massive Macondo well leak in the Gulf of Mexico in 2010, as well as their mechanisms for chewing up the many different components of the released crude oil.

ROV image of Macondo leak - Image: US Department of Energy
ROV image of Macondo leak - Image: US Department of Energy

The team, led by Berkeley Lab microbial ecologist Gary Andersen, is the first to simulate the conditions that occurred in the aftermath of the spill. Their study, “Simulation of Deepwater Horizon oil plume reveals substrate specialization within a complex community of hydrocarbon-degraders,” was published in The Proceedings of the National Academy of Sciences in June 2017.

This oil spill was the largest in history, with the release of 4.1 million barrels of crude oil as well as large amounts of natural gas from a mile below the surface of the ocean. After the initial explosion and uncontained release of oil, researchers observed a phenomenon that had not been seen before: More than 40% of the oil, combined with an introduced chemical dispersant, was retained in a plume nearly 100 miles long at this great depth.

Andersen and his team returned to the spill location four years later to collect water at depth. A suspension of insoluble oil droplets along with the more soluble oil fractions and chemical dispersant were recreated to mimic the conditions of the oil plume. Over the next 64 days the composition of the microbes and the crude oil were intensively studied.

The researchers witnessed an initial rapid growth of a microbe that had been previously observed to be the dominant bacterium in the early stages of the oil release but which had eluded subsequent attempts by others to recreate the conditions of the Gulf of Mexico oil plume.

Through DNA sequencing of its genome they were able to identify its mechanism for degrading oil. They gave this newly discovered bacterium the tentative name of Bermanella macondoprimitus.

“Our study demonstrated the importance of using dispersants in producing neutrally buoyant, tiny oil droplets, which kept much of the oil from reaching the ocean surface,” Andersen said. “Naturally occurring microbes at this depth are highly specialized in growing by using specific components of the oil for their food source. So the oil droplets provided a large surface area for the microbes to chew up the oil.”

The importance of this study is that it identified the mechanisms the bacteria used to degrade oil and the relationship of these organisms involved in the spill to previously characterised hydrocarbon-degrading organisms.

Andersen noted that it is not clear if the degradation of oil at these depths would have occurred in other offshore oil-producing regions. “The Gulf of Mexico is home to one of the largest concentrations of underwater hydrocarbon seeps, and it has been speculated that this helped in the selection of oil-degrading microbes that were observed in the underwater plumes,” he said.

New oil exploration offshore of Brazil, Uruguay, and India have now exceeded 2 miles below the ocean surface. By capturing water from these areas and subjecting them to the same test, it may be possible in the future to understand the consequences of an uncontrolled release of oil in these areas in greater detail.

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