A series of recent scientific discoveries have overturned the preconceptions of many biologists about the so-called “white mold fungus” and shed light on the mechanism of carbon sequestration in nature.
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If you’ve come across a dead tree in the forest or green algae in a lake, you’ve seen mushrooms in action. However, scientists are only just beginning to understand the vital role these organisms play around the world in sequestering carbon, thanks in particular to two studies conducted in 2021 that revealed more about them.
Researchers already knew that 300 million years ago, this fungus known for its white mold acquired a unique ability to digest lignin. It’s the hard natural polymer found in tree cell walls, making them hard and woody. This superior digestive capacity ended the Carboniferous period by destroying woody debris that would otherwise turn into charcoal. But until now, no one really knew what happened to the carbon in the lignin.
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Scientists have long believed that it simply evaporated into the atmosphere. But that didn’t sit well with Davinia Salvachoa Rodriguez, a microbiologist at the National Renewable Energy Laboratory in Golden, Colorado. After studying white mold fungi for ten years, they showed that they eat lignin carbon to fuel their growth, according to a study published in March in the Proceedings of the National Academy of Sciences (PNAS). Davinia Salvachúa Rodríguez’s discovery indicates that this fungus plays an important role in sequestering lignin-derived carbon in the soil.
Similarly, Stanford University microbiologist Ann Deccas published a study in June in PNAS showing that parasitic fungi that live on tiny algae in oceans and lakes remove some carbon from the algae, which can then return to the atmosphere.
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Mushrooms to absorb carbon
Conventional wisdom held that all the carbon in algae remains in the microbial feedback loop near the water’s surface, where microbes gobble up green plants and then release carbon dioxide. But the work of Ann Dekas and her colleagues has shown that mushrooms extract up to 20% of the carbon from the algae. Hence, as they outnumber microbes in the feedback loop, they become a more likely meal for larger species by removing them from the loop.
As the carbon moves up the food chain, it can eventually sink to the ocean floor, which also traps the carbon, when higher species die. “Many aquatic microbiologists don’t think about mushrooms at all. But if you really want to understand the whole system, you have to include mushrooms,” explains Ann Deccas.
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