Bacteria made quick work of the methane released by the Deepwater Horizon blowout, digesting most of the gas within the four months after its release, according to a new study published online at ScienceExpress.
One positive outcome of this violent and tragic blowout was that, in some ways, it paralleled natural events that are rare but potentially dangerous, and highly intriguing to scientists. For example, large volumes of methane have at times been released naturally along the sea floor through hydrocarbon seeps, hydrothermal vents, or the decomposition of solid, “clathrate” methane deposits. While large methane-release events would have had major effects on ocean chemistry and possibly climate, scientists can’t exactly set them off in order to see what happens.
The Deepwater Horizon blowout discharged massive amounts of oil and gas into the deep Gulf of Mexico, including methane. John Kessler of Texas A&M University and colleagues surveyed the Gulf waters during the leak as well as after the wellhead was sealed, and their results indicate that a vigorous bloom of bacteria degraded virtually all of the methane released form the well within 120 days of the initial blowout.
The authors base these conclusions on measurements of methane and oxygen distributions at over 200 stations (oxygen drops when bacteria respire methane), as well as genetic sequence data from water samples indicating a growing presence of methane-digesting bacteria.
The findings suggest that large-scale releases of methane in the deep ocean are likely to be met by a similarly rapid bacterial response, the researchers say. In a study published earlier in the fall, this group reported measurements taken earlier than the ones in this paper, which indicated bacteria were also quickly consuming ethane and propane, even before the major response to the methane got underway. The study did not explore what effect microbes may have had on the oil from the spill.
Read an abstract of “A Persistent Oxygen Anomaly Reveals the Fate of Spilled Methane in the Deep Gulf of Mexico” by John Kessler et al.