Sunlight and the right microbes convert Arctic carbon into carbon dioxide

October 4, 2017
There is little shade in the Arctic, so when the permafrost melts, carbon is released into streams and lakes where a combination of sunlight and microbes converts it to carbon dioxide. Credit: Rose Cory, University of Michigan

Nearly half of the organic carbon stored in soil around the world is contained in Arctic permafrost, which has experienced rapid melting, and that organic material could be converted to greenhouse gases that would exacerbate global warming.

When thaws, microbial consumption of those carbon reserves produces carbon dioxide – much of which eventually winds up in the atmosphere, but scientists have been unsure of just how the system works.

A new study published this week in Nature Communications outlines the mechanisms and points to the importance of both and the right microbial community as keys to converting permafrost carbon to CO2. The research was supported by the U.S. National Science Foundation and the Department of Energy.

"We've long known that convert the carbon into CO2, but previous attempts to replicate the Arctic system in laboratory settings have failed," noted Byron Crump, an Oregon State University biogeochemist and co-author on the study. "As it turns out, that is because the laboratory experiments did not include a very important element – sunlight.

"When the permafrost melts and stored carbon is released into streams and lakes in the Arctic, it gets exposed to sunlight, which enhances decay by some microbial communities, and destroys the activity for other communities. Different microbes react differently, but there are hundreds, even thousands of different microbes out there and it turns out that the microbes in soils are well-equipped to eat sunlight-exposed permafrost carbon."

The research team from Oregon State and the University of Michigan was able to identify compounds that the microbes prefer using high-resolution chemistry and genetic approaches. They found that sunlight makes tastier for microbes because it converts it to the same kinds of carbon they already like to eat – the carbon they are adapted to metabolize.

Sunlight and the right microbes convert Arctic carbon into carbon dioxide
When Arctic permafrost melts, it seeps into streams and lakes where it is exposed to sunlight, starting the process of converting it to carbon dioxide. Credit: Rose Cory, University of Michigan

"The carbon we're talking about moves from the soil into rivers and lakes, where it is completely exposed to sunlight," Crump said. "There are no trees and no shade, and in the summer, there are 24 hours a day of sunlight. That makes sunlight potentially more important in converting carbon into CO2 in the Arctic than in a tropical forest, for example."

As the climate continues to warm, there are interesting ramifications for the Arctic, said Crump, who is a faculty member in OSU's College of Earth, Ocean, and Atmospheric Sciences.

"The long-term forecast for the Arctic tundra ecosystem is for the warming to lead to shrubs and bigger plants replacing the tundra, which will provide shade from the sunlight," Crump said. "That is considered a negative feedback. But there also is a positive feedback, in that seasons are projected to expand. Spring will arrive earlier, and fall will be later, and more water and carbon will enter lakes and streams with more rapid degradation of carbon.

"Which feedback will be stronger? No one can say for sure."

The stakes are high, Crump said. There is more stored in the frozen permafrost than in the atmosphere. It has accumulated over millions of years by plants growing and dying, with a very slow decaying process because of the freezing weather.

"Some of the organic matter is less tasty to microbes than others," Crump said, "but bacterial communities are diverse, so there will be something out there that wants that energy and will use it."

Explore further: Sunlight, not microbes, key to CO2 in Arctic

Related Stories

Sunlight, not microbes, key to CO2 in Arctic

August 21, 2014

The vast reservoir of carbon stored in Arctic permafrost is gradually being converted to carbon dioxide (CO2) after entering the freshwater system in a process thought to be controlled largely by microbial activity.

Tundra loses carbon with rapid permafrost thaw

September 7, 2017

Frozen in permafrost soil, northern latitudes store almost twice as much carbon as is currently in the atmosphere. Rapid Arctic warming is expected to expose previously frozen soil carbon to microbial decomposition and increase ...

Scientists investigate what breaks down permafrost carbon

February 14, 2017

A Florida State University researcher is delving into the complexities of exactly how permafrost thawing in the Earth's most northern regions is cycling back into the atmosphere as carbon dioxide and further fueling climate ...

Study measures methane release from Arctic permafrost

August 22, 2016

A University of Alaska Fairbanks-led research project has provided the first modern evidence of a landscape-level permafrost carbon feedback, in which thawing permafrost releases ancient carbon as climate-warming greenhouse ...

Carbon dioxide biggest player in thawing permafrost

June 13, 2016

Carbon dioxide emissions from dry and oxygen-rich environments are likely to play a much greater role in controlling future rates of climate change caused by permafrost thaw than rates of methane release from oxygen-poor ...

Biomass offsets little or none of permafrost carbon release

March 30, 2016

Scientists who study climate and ecosystems in the Arctic have weighed in on future changes in the region affecting soils, streams and wildfire, which will be releasing greater amounts of carbon dioxide and other greenhouse ...

Recommended for you

Climate change made Harvey rainfall 15 percent more intense

December 14, 2017

A team of scientists from World Weather Attribution, including researchers from Rice University and other institutions in the United States and Europe, have found that human-caused climate change made the record rainfall ...

East Antarctic Ice Sheet has history of instability

December 13, 2017

The East Antarctic Ice Sheet locks away enough water to raise sea level an estimated 53 meters (174 feet), more than any other ice sheet on the planet. It's also thought to be among the most stable, not gaining or losing ...

Hydraulic fracturing negatively impacts infant health

December 13, 2017

From North Dakota to Ohio to Pennsylvania, hydraulic fracturing, also known as fracking, has transformed small towns into energy powerhouses. While some see the new energy boom as benefiting the local economy and decreasing ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.