The influence of seafloor topography on subseafloor microbial communities is poorly understood. In this study, we systematically sampled subseafloor sedimentary microbial communities and pore-water geochemistry at bathyal, abyssal, and hadal water depths of the Puerto Rico Trench. The Puerto Rico Trench exhibits vertical relief of over 8 km with seafloor topography shaped by active plate tectonics and characterized by a very steep southern wall and active mass wasting. Sampling across these features, we find that subseafloor microbial communities are influenced by topography in the following two ways. First, subseafloor sediment in the deepest part of the trench is anoxic, enriched in organic matter due to mass transport of sediment from shallower water depths, and contains an anaerobic subseafloor community that is quite distinct from the anaerobic subseafloor community in anoxic sediment at bathyal depths. The difference between these bathyal and hadal subseafloor anaerobic communities is consistent with influence of water-depth-related physical properties on subseafloor community composition. Second, subseafloor sediment remains oxygenated for meters below seafloor on steep slopes within the bathyal zone, an abyssal topographic high within the trench, and the abyssal plain seaward of the trench subseafloor, likely due to limited sediment accumulation, which selects for the presence of aerobic microbial communities. The difference between these bathyal and abyssal aerobic subseafloor communities and the anaerobic communities at bathyal and hadal depths reflects the role of seafloor topography in structuring subseafloor availability of redox reactants, which in turn drives the activities and composition of subseafloor microbial communities. ### Competing Interest Statement The authors have declared no competing interest. U.S. National Science Foundation, https://ror.org/021nxhr62, OCE-2049515, OCE-2048927 Deutsche Forschungsgemeinschaft, OR417-7-1 Canadian Institute for Advanced Research, https://ror.org/01sdtdd95

The land between the Sutlej and Yamuna rivers in western India, near the Punjab–Haryana plains, is largely arid today. But thousands of years ago, these areas had perennial rivers that flowed year-rou...

The events, the most recent of which occurred 10—20 million years ago, saw the geographical poles shift by up to 0.6 degrees per million years — faster than plate tectonics.

Thrust Faulting and the Late-stage Contraction of the Moon, Watters, T. R., Banks, M. E., Nypaver, C. A., Robinson, M. S.

The events, the most recent of which occurred 10—20 million years ago, saw the geographical poles shift by up to 0.6 degrees per million years — faster than plate tectonics.

The events, the most recent of which occurred 10—20 million years ago, saw the geographical poles shift by up to 0.6 degrees per million years — faster than plate tectonics.

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