“This is really mucky,” says Tringe, an environmental microbiologist at the U.S. Department of Energy’s Joint Genome Institute. “You sink in at every step.” She bends down to take a murky water sample, then holds the cup up to the light.
“That looks disgusting,” laughs Susie Theroux, a postdoc in Tringe’s lab who still wrinkles her nose at the sight of the viscous gunk.
The wetland sludge Tringe and Theroux are sampling isn’t just any muck. It holds carbon dioxide-processing microbes that play a key role in climate change dynamics. Wetlands are widely valued as natural pollution filters and as habitat for endangered species such as the Yuma clapper rail, whooping crane and least tern. But they’re also a key part of the carbon cycle: Although wetlands cover only about 3 percent of Earth’s surface, they account for as much as 30 percent of soil carbon storage. Yet some wetland microbes secrete another potent greenhouse gas, methane, which may cancel out some of the benefits of pulling carbon dioxide from the atmosphere. Tringe is trying to determine just how much wetlands actually help offset climate change.
Those answers will come none too soon. Because of development and sea-level rise, the U.S. loses more than 80,000 acres of wetlands each year, according to a study by the U.S. Fish and Wildlife Service. To offset those losses, as required under the Clean Water Act, the government invests at least $3.9 billion each year to restore degraded wetlands or construct new ones to reach an annual net increase of 100,000 acres of wetlands.
By documenting the biological functions of wetland microbes, Tringe will learn how these tiny organisms affect the greenhouse gas equation, and eventually she’ll be able to help restoration experts design projects in a way that enhances climate benefits.
“A better understanding of the wetland microbial community will likely improve our ability to maximize carbon storage in these habitats,” says John Bourgeois, who manages California’s South Bay Salt Pond Restoration Project.
A Tall Order
To figure out just how microbial processes in wetlands work, Tringe and her team are building a catalog of wetland microorganisms and the biological tasks they carry out. “We’ve been collecting samples in a lot of places to analyze DNA and RNA,” Tringe says. “We’re generating the wetlands metagenome.”