Tectonic cycling may return buried seafloor microbes to life

by Clarence Oxford
Los Angeles CA (SPX) Apr 17, 2026
Tectonic activity in subduction zones may act as a pump that carries long-buried subseafloor microbes back toward the seafloor, according to research presented at the 2026 SSA Annual Meeting.

These microbes can remain dormant for thousands or even millions of years beneath about a kilometer of ocean sediment. They survive with specialized adaptations, but they must eventually return to the shallow seafloor to feed, grow and spread those traits to new generations.

Zhengze Li, a Ph.D. student at the University of Southern California, said fault slip in subduction zones may drive the fluid flow needed to move those buried microbes upward. Models developed by Li and colleagues suggest the tectonic pump could circulate more than 1 million gigatons of fluid per million years and potentially transport up to 1030 microbial cells.

Li described the process as a kind of microbial elevator. In subduction zones, one tectonic plate descends beneath another, and sediment layers on the downgoing plate are scraped off and build up in a wedge against the overriding plate.

Some deep dormant microbes stay on the downgoing plate and continue descending beneath the overriding plate toward the mantle, a journey Li and his colleagues call "the trip to hell."

Other microbes may escape that path by moving upward through fractures and faults in the sediment wedge, or more diffusely through the sediments, as subduction-related slip drives transport.

Once returned to the shallow seafloor, the microbes "can now be reactivated and can reproduce," Li said. "The full cycle-from burial and transport with the subducting plate to eventual return-can take tens of millions of years or longer."

Cold seeps on the seafloor, where subsurface fluids are discharged, provide direct evidence of active fluid transport and support the idea of ongoing tectonic pumping. These seep sites also give researchers accessible places to sample microbial communities and test links between tectonic processes and subseafloor life.

"We can also examine how seismic activity relates to the relative abundance of different microbial groups, and we find a positive correlation between seismic energy and the abundance of subsurface-associated microbes," Li said.

The researchers examined the concept in the Costa Rica subduction zone and found that higher seismic energy indices were associated with greater relative abundance of microbial taxa usually linked to subsurface environments.

Li said tectonic pumping does not require only large earthquakes. Slow slip events, tremor and aseismic creep can also create stress changes that mobilize fluids and transport microbes.

Related work by Li's coauthor Karen Lloyd, a microbial biogeochemist at USC, and others has identified adaptations that help deep-buried microbes survive long dormancy. These include DNA repair mechanisms and enzymes that allow the degradation of organic matter at depth.

Genomic studies also suggest that mutations in these microbes often preserve useful traits over thousands to millions of years. To pass those traits on and undergo further genetic innovation, the microbes may have to wait for tectonic transport to return them to a more hospitable environment.