Microbes kept the oil and gas spewing from the Macondo well from becoming even more of a disaster, preventing the Deepwater Horizon blowout from deeply befouling the Gulf coast. But these hydrocarbon-chompers got an assist from the Gulf of Mexico—the prevailing tides and currents helped keep hydrocarbon-eating microbes on the job, according to the results of a new model published in Proceedings of the National Academy of Sciences on January 9.

Simply put, the study sought to answer the question: how did five families of bacteria keep 4.1 million barrels of oil (and billions of cubic feet of natural gas) from becoming a bigger disaster? And, additionally, why didn't they suck all the oxygen out of the water while they were at it?

The answer appears to be ocean currents, according to a computer model:

Water mixing ensured that the 200 billion grams of hydrocarbons injected into the Gulf of Mexico became, ultimately, some 100 sextillion microbial cells of propane- and ethane-consuming Colwellia, aromatic-eating Cycloclasticus, methane-munching Methylococcaceaa, alkane -eating Oceanospirillales. They also ensured that hydrocarbons were introduced into waters already hosting microbe blooms spurred by earlier oil and gas releases. The team of researchers suggest that this "autoinoculation"—early blooms drifting back to the spill site and chowing down anew—allowed the microbes to work fast over the course of the months-long disaster as well as keeping oxygen depletion from growing too severe in any one place.

The model isn't perfect—it failed to precisely match observations of where the oil (and microbial) plume traveled—but it does explain why oil and gas consumption can proceed so fast, even when it's microbes (and not humans) doing the hydrocarbon consuming.