There’s a whole world of rock-eating fungi just underneath our feet in northern Michigan, with a potential connection to the gases that contribute to climate change.
In a new study published last month, University of Michigan researchers have unearthed just how diverse life can be within the Antrim Shale, a massive underground rock formation that’s also one of the state’s largest sources of natural gas.
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Scientists have long believed that these ancient, 350-million-year-old carbon deposits can’t support fungal life because there’s little sunlight or oxygen, until now.
“People have always assumed that fungi are either not there or not abundant,” said Quinn Moon, a Ph.D candidate in fungal biology at the University of Michigan who led the study.
He and a team of researchers took water samples from the Antrim Shale, about one-third of a mile beneath the surface. The rock formation stretches in an arc from Manistee, up to Petoskey, then toward Thunder Bay on Lake Huron.
What they analyzed from the samples showed biodiversity that researchers hadn't seen before – evidence of 689 likely species of fungi. The team also isolated and grew 205 species. And, they discovered 13 potentially new fungal species.
“It’s pretty mind-blowing,” Moon said. “The amount of microbes, the activity of it in the subsurface, could be a lot higher everywhere on the planet because it’s possible here.”
The finding suggests that the deep subsurface of the Earth is just as diverse as another known source of fungal life — ocean water.
Researchers in this field have only discovered about 5% of the world’s fungal diversity, which doesn’t include Earth’s subsurface. Moon said this study could open up new lines of study that haven’t been considered before.
“Questions about the total amount of diversity and where it is, those are still very pressing and even more pressing given we have this whole new ecosystem to investigate,” Moon said.
The study has potentially wider implications about how climate-warming pollution moves from below the Earth to the surface.
When it comes to the Antrim Shale, Moon said microbes eating the rock produce methane because of organic processes. Methane is a key component of natural gas, and could be contributing to the deposits extracted by power companies.
“That’s how much microbial life is happening in the subsurface,” he said.
Researchers not involved with the study say the findings raise questions about how microbes could impact the long-term storage of carbon beneath the surface.
About 90% of the Earth’s organic carbon is sequestered underground, and thought to be safely stored there. But carbon that makes its way to the surface could contribute to climate change, in the form of heat-trapping greenhouse gases.
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“It's impressive to think that microbes just have huge implications on all these processes that we kind of depend on, or that have shaped and continue to shape our planet,” said Greg Bonito, a professor at Michigan State University who studies fungi and was not involved in the study.
Bonito said the study was a “pretty compelling dataset with many lines of evidence.” The study used not only observational data to log the types of fungi found in the water samples, but also grew more than 200 species in petri dishes to show what life might be actively growing underground.
Growing cells in culture could help researchers address questions like what the fungi are actually eating, how quickly they’re eating, or how they interact with other organisms, said Anne Pringle, biology professor at the University of Wisconsin-Madison who was not involved in the study.
She said research like this helps people see the world differently.
“It helps you understand what’s living beneath the surface of the Earth. Should you think about it as a place where nothing happens, or should you think about it as a place of actively interacting organisms that are eating, breathing and dying?” she said. “It changes our perception of Earth.”
