An earlier study published in the Jan. 21 edition of the journal Science concluded that “nearly all” of the methane discharged from the well was consumed in the water column within approximately 120 days of the release. But in a new study, published May 27 in Science, authors argue that several factors challenge the original attribution of low oxygen zones to the oxidation of methane gas, including:
- Uncertainties in the hydrocarbon discharge from the blowout;
- Oxygen depletion fueled by processes other than methane consumption; and
- A problematic interpretation of genetic data and shortcomings of the model used by the authors of the January study.
“Our goal is to understand what happened to the methane released from the Macondo discharge and, in the larger framework, to better understand the factors that regulate microbial methane consumption following large-scale gas releases,” said marine scientist and lead author Samantha Joye, a professor in the University of Georgia Franklin College of Arts and Sciences.
Methane is a potent greenhouse gas. Understanding the fate of the methane released from the Deepwater Horizon well has larger implications, the authors said, since global warming is likely to accelerate the release of methane that is currently trapped in hydrates on the seafloor. Based on the conclusion that bacteria had rapidly consumed the methane released from the Deepwater Horizon well, the original study published in Science suggested that methane released from the oceans may not be likely to amplify an already warming climate.
Joye and her colleagues noted that several other studies have found that considerable amounts of methane released from natural deep-sea vents are not consumed by microbes. The most vulnerable store of methane hydrates is not in the Gulf of Mexico, they pointed out, but in the deposits that underlie the shallow waters of the Arctic.
“I believe there is still a lot to learn about the environmental factors that regulate methane consumption in the Gulf’s waters and elsewhere,” Joye said.