Back in May, I blogged about a proposal to monitor dissolved methane levels in the Gulf of Mexico as a surrogate marker for oil. The idea was that the Deepwater Horizon blowout was spewing a mixture of oil and methane into the water, and while measuring oil levels is relatively complicated, dissolved methane is pretty easy to track. Measuring methane would have provided a good estimate of the actual volume of the oil spill.
I don’t know how far that effort got, but if researchers didn’t measure the gas promptly, it’s too late now. As John Kessler and his colleagues report in the latest online issue of Science, a massive bacterial bloom quickly ate the excess methane.
According to data from the NOAA research vessel Pisces, dissolved methane levels dropped rapidly in the Gulf once BP capped the Macondo well. Just four months after the initial blowout, methane levels were nearly normal again.
That’s good, because methane in the water column alters the water chemistry in potentially harmful ways, and methane released into the atmosphere is a potent greenhouse gas. Instead, the methane from the well seems to have fed a bacterial bloom, which will presumably enter the food web and the normal oceanic carbon cycle. It could still have downstream impacts on the ecosystem, but they should be less severe than researchers had initially feared.
It also illuminates an interesting aspect of normal ocean microbiology. Deep methane releases are a regular phenomenon on the seabed, stemming from hydrothermal vent eruptions and the breakdown of solid methane hydrates. Based on the rapid bacterial response to the Deepwater Horizon blowout, the researchers propose that methanotrophic bacteria react similarly to these natural methane releases, quickly recycling the gas back into the marine ecosystem.
Too bad we can’t get them to eat the oil off the beaches that fast.