Tectonic pump closes the evolutionary loop for long-buried subseafloor microbes

Zhengze Li , Sylvain Barbot, Karen G Lloyd

Deep marine sediments host one of Earth’s largest microbial biospheres, yet most cells in this environment persist in a non-growing state for thousands to millions of years beneath kilometers of sediment. For natural selection to favor such extraordinary long-term survival, a mechanism must exist that is capable of returning buried living populations to near-surface environments, where higher-quality food sources allow reproduction and dispersal. Here we propose and test whether subduction-zone earthquakes provide this missing mechanism. Using poroelastic models constrained by diverse observational benchmarks, we show that slip-driven water circulation in subduction-zone outer wedges generates global fluxes exceeding 10^6 Gt/Myr, sufficient to transport 10^26-10^30 cells per Myr. We further show that advective microbial transport is physically and biologically feasible, and find that cumulative seismic forcing correlates with microbial diversity and the relative abundance of common subsurface-associated clades in communities from surface-expressing seep systems across the Costa Rica forearc. These results suggest that tectonic pumping can return microbial communities buried kilometers deep to the seafloor, where they can resume cell proliferation and disperse, forming a burial–reemergence cycle that closes a natural selection loop favoring extreme longevity and deep-burial adaptation.