The 2010 blowout released an estimated 160 million gallons of crude oil in the largest offshore spill in US history. Some of that oil was burned or skimmed off the surface, while another portion left a ring of oily residue about the size of Rhode Island on the seafloor off Louisiana. The rest is suspected to have been consumed by undersea microbes, but there’s still “considerable uncertainty and disagreement” among scientists about how that happened, according to the new study.
“We had a good sense of the types of organisms that were degrading the oil, but didn’t have insights into the functions of how they were degrading oil,” said Gary Andersen, a microbial ecologist at the federal Lawrence Berkeley National Laboratory in California and one of the authors.
Andersen said the findings, published Monday by the research journal Proceedings of the National Academy of Sciences, could be used to assess the risk posed by drilling in other parts of the ocean.
“It’s possible that before you even start drilling, what would make sense is to identify the capacity of the region where you’re drilling for oil to be degraded,” he said.
RELATED: The Gulf of Mexico’s ‘Dead Zone’ Could Nearly Double in Size This Year
The study used samples of sea water from around the site of the 2010 disaster and attempted to reproduce the contamination present during the disaster. Andersen said the newly discovered bacteria was the first to attack the oil, digesting crude components related to products like motor oil or gasoline, and the fastest to reproduce. Other species followed in waves, working on different parts of the oil.
The new species has been provisionally dubbed Bermanella macondoprimitus – “Macondo” being the undersea prospect that oil company BP was exploring when the blowout occurred.
The blowout led to an explosion and fire that sank the drill rig Deepwater Horizon, killing 11 men, and uncorked an undersea gusher that took three months to cap. It also killed large numbers of dolphins, tens of thousands of birds and turtles, and billions of juvenile fish and oysters — a major commercial species on the Gulf Coast.
To keep all that oil from hitting shore, BP used more than 1.8 million gallons of chemical dispersants deep under water to break up the spill into tiny droplets. Dispersants are toxic, so their extensive use in deep water was highly controversial at the time.
“There had never been before at a mile deep, so this was really unique,” Andersen said. “In this case, by adding dispersants at depth, it retained more oil at a deep depth and created more of a 3-dimensional amount of oil.”
RELATED: Coastal Louisiana Is Sinking Faster Than Expected
Post-disaster studies found dispersants became more toxic to marine life when combined with oil, and a 2015 study that attempted to simulate the spill found they drove off microbes that would otherwise have helped break down the oil. But Andersen said the earlier studies didn’t include insoluble parts of the oil that drew the newly seen bacteria, “so they did not see the first early responders that we did.”
That suggests that the dispersant’s toxicity didn’t prevent the oil from being broken down, he said. However, the heaviest components of the oil — compounds like asphalt, for instance -- saw little degradation at the end of the experiment, Andersen said.
“That’s probably what some of the unaccounted-for oil could be,” he said.
WATCH: The Deepwater Horizon Oil Spill: A Survivor's Story