Discovery of first active seep in Antarctica provides new understanding
of methane cycle

Date:
July 22, 2020
Source:
Oregon State University
Summary:
The discovery of the first active methane seep in Antarctica is
providing scientists new understanding of the methane cycle and the
role methane found in this region may play in warming the planet.



FULL STORY ==========================================================================
The discovery of the first active methane seep in Antarctica is providing scientists new understanding of the methane cycle and the role methane
found in this region may play in warming the planet.


==========================================================================
A methane seep is a location where methane gas escapes from an underground reservoir and into the ocean. Methane seeps have been found throughout
the world's oceans, but the one discovered in the Ross Sea was the first
active seep found in Antarctica, said Andrew Thurber, a marine ecologist
at Oregon State University.

"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," Thurber said. "This is a significant
discovery that can help fill a large hole in our understanding of the
methane cycle." The researchers' findings were published today in
the journal Proceedings of the Royal Society B. Co-authors are Sarah
Seabrook and Rory Welsh, who were graduate students at OSU during
the expeditions. The research was supported by the National Science
Foundation.

Methane is a greenhouse gas that is 25 times more powerful than carbon
dioxide at warming the planet. Most methane in the ocean water and
sediment is kept out of the atmosphere by microbes that consume it.

Thurber and his colleagues discovered that the microbes around the
Antarctic seep are fundamentally different that those found elsewhere
in the world's oceans. This helps researchers better understand methane
cycles and the factors that determine whether methane will reach the
atmosphere and contribute to further warming, Thurber said.



==========================================================================
The Ross Sea seep was discovered in an area that scientists have studied
for more than 60 years, but the seep was not active until 2011, said
Thurber, an assistant professor in Oregon State's College of Earth,
Ocean, and Atmospheric Sciences and the College of Science's Department
of Microbiology.

An expansive microbial mat, about 70 meters long by a meter across,
formed on the sea floor about 10 meters below the frozen ocean
surface. These mats, which are produced by bacteria that exist in a
symbiotic relationship with methane consumers, are a telltale indication
of the presence of a seep, said Thurber.

"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." Thurber happened
to be in Antarctica in 2012 when another researcher told him about a
"microbial waterfall" and thought it was something he should look at.

Thurber was able to confirm the seep's presence, collect samples and
analyze the seep and its environment. When he returned to the site in
2016 to conduct further study, he also discovered a second seep nearby.

Antarctica is believed to contain as much as 25 percent of Earth's
marine methane. Having an active seep to study gives researchers new understanding of the methane cycle and how that process might differ in Antarctica compared to other places on the planet, Thurber said.



==========================================================================
For example, researchers have found that the most common type of microbe
that consumes methane took five years to show up at the seep site and
even then those microbes were not consuming all of the methane, Thurber
said. That means some methane is being released and is likely working
its way into the atmosphere.

Studying the site over a five-year time span allowed researchers to see
how microbes respond to the formation of a seep, said Seabrook, who earned
her doctorate at OSU and is now a post-doctoral scholar at the National Institute of Water and Atmospheric Research in Wellington, New Zealand.

"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," she said.

Researchers had assumed that microbes should respond really quickly to
changes in the environment, but that wasn't reflected in what OSU's team
saw in Antarctica, Thurber said.

"To add to the mystery of the Antarctic seeps, the microbes we found were
the ones we least expected to see at this location," he said. There may
be a succession pattern for microbes, with certain groups arriving first
and those that are most effective at eating methane arriving later.

"We've never had the opportunity to study a seep as its forming or one
in Antarctica, 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," Thurber said.

"Animals in Antarctica are very different than elsewhere in the world
as the continent has been separated from the rest of the globe for
more than 30 million years -- a long time for evolution to act," he
said. "That has resulted in a remarkable diversity of fauna that we
only find there. That may also contribute to the differences in microbes there." It is important to understand how methane seeps behave in this environment so researchers can begin factoring those differences into
climate change models, Thurber said. He hopes to return to the site to
monitor its evolution and conduct further research.


========================================================================== Story Source: Materials provided by Oregon_State_University. Original
written by Michelle Klampe. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Andrew R. Thurber, Sarah Seabrook, Rory M. Welsh. Riddles in
the cold:
Antarctic endemism and microbial succession impact methane
cycling in the Southern Ocean. Proceedings of the Royal
Society B: Biological Sciences, 2020; 287 (1931): 20201134 DOI:
10.1098/rspb.2020.1134 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200722163246.htm

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