Fungi Are Capturing More Carbon Than We Thought

This article appeared in the January/February 2022 issue of Discover magazine as “More Than Meets the Fungi.” Become a subscriber for unlimited access to our archive.

If you’ve encountered a dead tree in the woods or green algae on a lake, you’ve witnessed fungi at work. Yet scientists are just beginning to grasp the vital role that these worldwide organisms play in carbon sequestration, thanks in part to a couple of breakthrough studies in 2021.

Researchers already knew that 300 million years ago, white-rot fungi evolved the unique ability to digest lignin. That’s the natural, tough polymer in the cell walls of trees, making them rigid and woody. This fungal super-skill of digestion ended the Carboniferous Period by decomposing woody debris that would’ve fossilized into coal. But no one really knew what happened to the carbon inside the lignin.

Scientists had long thought it simply evaporated into the atmosphere. But that didn’t sit right with Davinia Salvachúa Rodríguez, a microbiologist at the National Renewable Energy Laboratory in Golden, Colorado. After 10 years of studying white-rot fungi, she demonstrated that it eats the carbon in lignin to fuel its growth, according to a March study in Proceedings of the National Academy of Sciences (PNAS). Rodríguez’s discovery flags white-rot fungi as a key player in sequestering lignin-derived carbon in soil.

Similarly, Stanford University microbiologist Anne Dekas published a study in June in PNAS showing that parasitic fungi that live on tiny algae in oceans and lakes remove some of the carbon inside the algae, which might otherwise reenter the atmosphere.

Conventional wisdom had maintained that all of the carbon inside the algae remained in a microbial feedback loop near the water’s surface, where microbes consumed the green plants and then released the C02. But Dekas and colleagues showed instead that the fungi siphon off up to 20 percent of the algae’s carbon. Then — because the fungi outsize the microbes in the feedback loop — the fungi become a more likely meal for larger species, which remove them from the loop. As the carbon makes its way up the food chain, it may eventually sink to the ocean floor, which also sequesters carbon, when the top species dies.

“A lot of aquatic microbiologists don’t have fungus on their minds at all,” says Dekas. “If you really want to understand the whole system, you’ve got to include fungi.”

Source : Discovermagazine