Up to 30% of life, by weight, is underground. Seismic activity may renew the energy supply for subterranean ecosystems.
Eric Boyd and colleagues chronicled the ecological changes in subsurface microbial communities that took place after a swarm of small earthquakes rattled the Yellowstone Plateau Volcanic Field in 2021. Subsurface microbial communities are powered by chemical energy gleaned from the interactions between rocks and water. Earthquakes can expose new rocks, release trapped fluids, and alter the flow path of water, together kicking off new reactions and changing the chemical "menu" for subsurface microbes. The authors collected fluid samples from a nearly 100-meter deep borehole on the western shore of Yellowstone Lake five times in 2021 chronicling increased concentrations of hydrogen, sulfide, and dissolved organic carbon after seismic activity. Shifts in the geochemical composition of waters were accompanied by increases in the concentration of planktonic cells. Further, the microbial populations changed over time, unlike the relatively stable subsurface communities known to inhabit aquifers hosted in continental bedrock. According to the authors, kinetic energy from earthquakes can change the geochemical and microbial compositions of aquifer fluids. The general mechanics implicated in the Yellowstone borehole could play out in a range of seismically active subterranean ecosystems—and could even be a dynamic that expands microbial habitability on rocky planets such as Mars.
