Seismic Activity Shakes Up Microbes Deep Under Yellowstone Lake
Spanning Wyoming, Idaho, and Montana, the Yellowstone Plateau Volcanic Field is a hotspot for seismic activity. Between May and November 2021, over 2,000 small earthquakes were detected, peaking at just 3.6 M on the Richter scale.
While these events might not have ripped up the picturesque landscape, their effects below ground are less clear. Previous research has established that seismic activity alters fluids passing through rock underground. A research team, including Montana State University microbiologist Eric Boyd, set out to discover how that underground energy alters the microbes that call these water sources home.
The study, on which Boyd was the first author, was published in PNAS Nexus. Boyd and his team collected fluid samples from a borehole that descended nearly 300 feet into the ground beside the shores of Yellowstone Lake. Over five sampling events throughout 2021, they investigated how subsurface chemical and microbial communities shifted.
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Shifting Microbes Respond To Seismic Shocks
The subsurface is home to up to 30 percent of Earth’s biomass, often found in water flowing through the bedrock. Subsurface microbial communities that live in underground reservoirs are usually stable. But the microbes under Yellowstone Lake changed over time.
After periods of seismic activity, chemicals like hydrogen, sulfide, and dissolved organic carbon increased; at the same time, Boyd and his team detected higher concentrations of specific microbes in their samples. These included the species Dethiobacteraceae and Desulfotomaculum, which generate energy through the oxidation of inorganic molecules. As swarms of earthquakes dissipated, these changes reversed.
These shifts, write the authors, suggest that the “subsurface biosphere dynamically responds to seismic-induced geochemical change.” In other words, as seismic activity alters underground chemicals, microbes will respond to the resulting changes in available nutrients.
Grinding Rocks Replicate Key Findings
The authors attempted to replicate their findings in the lab. To do so, they ground up samples of rhyolite — the primary bedrock found in Yellowstone — in a jaw crusher and then milled it into a fine powder. This process released organic carbon and hydrogen, suggesting that rock breakdown might have fueled the chemical shifts they observed in their borehole samples. The authors suggest that the same process is happening on a massive scale during seismic activity at Yellowstone. The concentrations of hydrogen and dissolved organic carbons measured from the borehole were some of the highest ever recorded at Yellowstone.
The authors say that similar processes are likely to apply to other regions of underground seismic activity, both across Earth and on other planets. On Mars, seismic activity has been detected. The authors suggest that earthquakes could, quite literally, shake up the biome of other planets, potentially making them more habitable for life.
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