Yellowstone quakes ignite a surge of hidden microbial life underground

Car headlights illuminate the steam plume from Excelsior Geyser at Yellowstone. Image by Neal Herbert, National Park Service, CC3.0.

For those who have a connection with the pharmaceutical or healthcare sector, Yellowstone Park has a special connection. Within the hot springs, or geysers, the microorganism used to verify the success of moist heat sterilisation (as achieved using an autoclave) was harvested. This is a heat-resistant organism with the long name of Geobacillus stearothermophilus.

Geysers are hot springs that intermittently spout a column of hot water and steam into air.

The same level of interest can be applied to the work recently reported by researchers studying Yellowstone’s depths. The scientists have discovered that small earthquakes can recharge underground microbial life.

The quakes exposed new rock and fluids, creating bursts of chemical energy that microbes can use. Both the water chemistry and the microbial communities shifted dramatically in response. This dynamic may help explain how life survives in such deep, hot, and dark environments.

Specifically, the researchers investigated how a burst of small earthquakes during 2021 affected the communities of microorganisms living deep beneath the Yellowstone Plateau Volcanic Field. These microbes inhabit rock and water systems far below the surface, where sunlight never reaches. Instead of relying on photosynthesis, they depend on chemical reactions that occur when water moves through fractured rock. This chemistry provides the energy that supports many forms of underground life.

What’s special about earthquakes and life?

Earthquakes have the potential to reshape this environment in several ways. Shaking can break open new rock surfaces, force out fluids that were previously sealed away, and redirect the flow of water through the subsurface. Each of these effects can create fresh chemical reactions, which in turn alter the types of energy available to microbial communities. The researchers refer to this shift in available resources as a change in the chemical “menu” that microbes can draw from.

Quake storms and sampling

To understand how seismic activity influenced this hidden ecosystem, the researchers collected water samples from a nearly 100-meter deep borehole located along the western edge of Yellowstone Lake. The scientists sampled the site five times throughout 2021, giving them a rare look at how conditions changed both immediately and over the following months.

The analyses of these samples showed notable increases in hydrogen, sulphide, and dissolved organic carbon after the earthquakes. These compounds serve as important energy sources for many subsurface organisms.

Even small seismic events can drive meaningful ecological shifts underground.

It was noted that as the chemistry of the water shifted, a rise in planktonic cells took place, suggesting that more microbes were present in the water column than before. This combination of chemical and biological changes indicates that the quake swarm temporarily boosted the resources available to deep microbial life.

There was an increased abundance of chemolithotrophic, putative hydrogen-oxidising Dethiobacteraceae and Desulfotomaculum bacteria. These are anaerobic, spore-forming bacteria in the class Clostridia.

In motion

As well as detecting an increase in cell numbers, the microbiologists observed that the types of microbes present changed over time. This stands out since subsurface microbial communities in continental bedrock aquifers are often considered relatively stable. In contrast, the Yellowstone system appeared to respond quickly and noticeably to the pulse of seismic energy.

Changes in the geochemical composition of fluids were coordinated with changes in the taxonomic composition of communities and their functions.

According to the researchers, the kinetic energy associated with earthquakes can influence both the chemistry and the biological makeup of aquifer fluids. These findings imply that even small seismic events can drive meaningful ecological shifts underground.

Looking to the stars

The processes observed in the Yellowstone borehole may not be unique. Many regions around the world experience regular seismic activity that could similarly reshape subsurface energy supplies. If this mechanism is widespread, it could help explain how microbial life persists in deep and isolated environments.

Hence,  the same basic dynamics might occur on other rocky planets that contain water. If earthquakes or similar geological motions can refresh chemical resources below the surface, this could expand the possible habitats for microbes on worlds such as Mars.

The research is featured in the science journal PNAS Nexus, titled “Seismic shifts in the geochemical and microbial composition of a Yellowstone aquifer.”