GALVESTON — Microbes that were expected to consume thousands of tons of methane gas released into the Gulf of Mexico after the Deepwater Horizon oil spill instead slowed down and left much of the deadly gas in the water, according to researchers, including one from Texas A&M University at Galveston.
The findings pose questions about whether the methane gas — a greenhouse gas that can contribute to climate change — could find its way from the water into the air.
“Most of the gas injected into the Gulf was methane, a potent greenhouse gas that contributes to global climate change, so we were naturally concerned that this potent greenhouse gas could escape into the atmosphere,” said Samantha Joye, the senior author of the paper and a marine science professor at the University of Georgia.
Researchers compared the levels of methane gas in the water in samples before and after the oil spill, which spewed an estimated 4.9 million barrels of oil into the Gulf of Mexico 41 miles off the Louisiana coast in July 2010.
Scientists believed that microbes, called methatrophs, in the Gulf waters essentially would eat the massive amounts of methane gas that leaked into the water from the Deepwater Horizon’s wellhead. The microbes break down methane — a chemical compound composed of carbon and hydrogen — and use the carbon as an energy source.
The tests showed that the number of microbes grew dramatically in the two months after the spill, consuming large amounts of the methane. But then the bacteria levels plummeted, leaving about half the methane gas in the water.
Researchers believe that the large of amount of gas and a lack of essential nutrients in the water kept the bacteria from gobbling up all the methane.
“It shows the sudden drop in bacteria consuming the gas was not due to an absence of methane, but a host of biological, environmental and physical constraints that made it difficult for bacteria to consume the methane rapidly,” said Rainer Amon, an associate professor of marine sciences and oceanography at Texas A&M University at Galveston.
“There were still considerable amounts of methane in the water column.”
Methane is the second most common greenhouse gas emitted in the United States behind carbon dioxide, according to the U.S. Environmental Protection Agency.
Methane accounts for 9 percent of all man-made greenhouse gas emissions, but also comes from natural processes in wetlands and livestock.
Scientists now need more information about what factors keep the microbes from consuming all the natural gas in the water, according to the research team.
Doing so will give a better understanding of where such gas will end up during future oil spills, they said.