Earthquake-induced redistribution and reburial of microbes in the hadal trenches

The hadal trenches located on the subduction zone harbor unique deep-sea microbes, yet the mechanisms regulating the characteristics of the deep-sea microbial communities remain largely unknown. The frequent and unpredictable tectonic processes such as earthquakes triggered by plate subduction act as a lateral transport pathway for sediments, and may lead to redistribution and reburial of allochthonous microbes. However, such tectonically-triggered processes in the hadal trenches are not yet investigated. Here we demonstrate that distinctive allochthonous microbial communities are introduced into the Japan Trench by three historical earthquakes, with community structure transitions observed across the turbidite boundaries. The variations of the microbial community structures are linked to earthquake-driven organic carbon deposition and its characteristics, suggesting the potential impact of mass transport events on the microbial-mediated deep carbon cycles. Our calculations indicate that the Pacific trenches receive at least 5.1 Pg of earthquake-induced microbial biomass carbon during the past century, with spatial and temporal variations at different scales. These results suggest that pulsed tectonic events play a crucial role in introducing allochthonous microbes to the deep biosphere, potentially leading to substantial microbial biomass carbon export into the subduction zone.