Much of the Deepwater Horizon oil spill has disappeared because of bacteria

Researchers from several leading institutions in the United States say they have discovered a new kind of naturally occurring underwater bacteria that has eaten a considerable portion of the oil that spilled out of the Deepwater Horizon drilling platform.

The microbe is one of many species that helped mitigate damage from one of the worst environmental disasters in history. The scientists also say their work gives insights into how future oil spills could be mitigated.

In April 2010, an explosion on the Deepwater Horizon oil platform in the Gulf of Mexico killed 11 people and caused more than 4 million barrels of oil to shoot out of the well one mile below the surface of the ocean.

Recovery teams poured millions of barrels of chemicals into the ocean to disperse the oil.

Previous research has suggested the dispersants actually slowed microbes' ability to degrade the oil. But this new paper, published Monday in the Proceedings of the National Academy of Sciences, suggests that the dispersants broke up the oil into tiny droplets, which made them less buoyant and unable to float to the surface. Thus, the chemicals kept the oil in a kind of three dimensional cloud below the surface, making it more available to the microbes that live in the deeper portions of the ocean.

In particular the fact that the oil formed a cloud of droplets meant more of the oil's surface area was exposed to the microbes, making it easier for the bacteria to degrade it than the portions of the oil that floated to the surface or spread out on the ocean floor.

The exact amount the microbes have degraded is difficult to determine, said the study's senior author, Gary Andersen, a microbial ecologist at the University of California.

The team took water samples from the area around the spill, and recreated the conditions of the spill in a computer simulation to mimic what would have happened in the ocean following the accident.

In their examinations of the water samples and their simulation, they found one particularly dominant bacterium — called Candidatus Bermanella macondoprimitus — that previous research teams had not seen. The team sequenced the bacterium's genome and were even able to identify the genes responsible for degrading various components of oil.

"Laboratory experimental studies by other groups have not replicated the suspension of dispersed oil droplet conditions observed in deep-water plumes," wrote the team in their paper, "which may explain why these studies have been unable to enrich the early responding Bermanella and recreate the succession of bacteria observed in the field."

In fact, Andersen said, researchers can identify which genes in potentially any such microbe can degrade components of oil, and which specific components they can degrade. The simulation he and his colleagues devised shows how those bacteria would behave in a spill.

These fast-growing, rapidly replicating bacteria that previous research had not seen led the team to conclude that the dispersants had not in fact prevented bacteria from degrading the oil.

This does not mean that this bacterium can be dropped into the middle of an oil spill anywhere on the planet, Andersen said. It cannot practically be removed from its native ecosystem. In addition, the bacterium cannot be cultured in a lab.

But scientists can travel to areas around oil rigs and use water sampling and genome sequencing to find bacteria that could degrade oil, should a spill ever occur in those regions. That could tell what the rates of oil degradation are likely to be, and how it would be best to manage or respond to an oil spill in that area, he said.

Scientists debate just how much oil from Deepwater Horizon is still out in the environment, Andersen said, but there are no visible signs of the oil in the deep waters of the Gulf of Mexico right now. The oil that made it to the surface is degrading far more slowly, he said, and it is hard to tell how much oil from that spill is on the floor, because other chemicals leave similar signatures in the environment.

"But the actual marine life has recovered well from that spill, and fishing has resumed, so it has improved," Andersen told CNBC in an interview.

In the future, it would be best to put a system in place to understand the ecology of any area where prospectors drill for oil, Andersen said. Understanding the area would allow drillers to optimize their strategy so that if a spill does occur, naturally occurring bacteria would be able to best respond to it.

"They should be looking everywhere they are drilling for oil, and doing these types of simulations to see what the natural oil-degrading organisms would be and how quickly they would degrade oil," Andersen said.

WATCH: A look back at BP's Deepwater Horizon oil spill

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