Methane is one of the most common greenhouse gasses responsible for climate change. With the recent discovery of an active methane seep in Antarctica, scientists can learn more about the methane cycle in the region and its effect on the entire atmosphere.
Methane seeps, or cold seeps, are areas along the margins of continents where methane emerges from an underground reservoir and into oceans. Since 1984, more than 400 methane seeps have been discovered. A team from Oregon State University recently had its paper added to the Proceedings of the Royal Society journal.
"Methane is the second-most effective gas at warming our atmosphere, and the Antarctic has vast reservoirs that are likely to open up as ice sheets retreat due to climate change," said marine ecologist Andrew Thurber. "This is a significant discovery that can help fill a large hole in our understanding of the methane cycle."
Although carbon dioxide is the most produced greenhouse gas worldwide, methane traps heat 25 times more powerful than carbon emissions. When the gas is in ocean sediment and water, it is consumed by microbes.
Active Methane Seep
The active methane seep in the Ross Sea is the first one discovered in Antarctica. The team observed that the microbes surrounding the methane seep in the Antarctic waters were unique from those found in other oceans. Methane cycles can be better understood and help determine factors that cause gas to become a part of climate change.
Although the Ross Sea seep had been monitored for over 60 years, it was only active since 2011. Across the seafloor at about 32 feet below sea level, the team found an enormous microbial mat about 330 feet long. The mat was produced by bacteria in a symbiotic relationship with microbes that consume methane.
"The microbial mat is the road sign that there's a methane seep here," Thurber said. "We don't know what caused these seeps to turn on. We needed some dumb luck to find an active one, and we got it."
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Methane-Consuming Microbe
Thurber explained that Antarctica contains about 25 percent of the world's marine methane. The most common methane-consuming microbe, or methanotrophs, took five years to appear at the site. However, the microbes were not consuming all the methane, meaning that somehow, some of the gas was being released into the atmosphere.
For five years, the team observed how the microbes responded to the formation of the active seep. Sarah Seabrook, from the National Institute of Water and Atmospheric Research in Wellington, New Zealand, said, "What was really interesting and exciting was that the microbial community did not develop as we would have predicted based on other methane seeps we have studied around the globe."
The microbes were not responding to the rapid changes caused by global warming. "To add to the mystery of the Antarctic seeps, the microbes we found were the ones we least expected to see at this location," said Thurber.
A succession pattern was also observed with the methane consumers arriving later than initial groups. "We've never had the opportunity to study a seep as its forming or one in Antarctica," said Thurber.
"Because of this discovery, we can now uncover whether seeps just function differently in Antarctica or whether it may take years for the microbial communities to become adapted," he continued. The evolution of methane seeps can help advance environmental research and add unique factors to climate change models.
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