Hadal topography incubates hidden microbial hotspots in the deepest ocean.

Plate subduction creates unique topographic features in hadal trenches, yet their influence on microbial ecosystems and the global ocean remains unclear. Here, we conducted a topography-targeted investigation across 6-11 km of water depth within the Mariana Trench, integrating metagenomic, metaproteomic, and geochemical analyses. Coupled with high-resolution topographic mapping, our analyses reveal topography as an overlooked determinant of hadal geochemical and microbial heterogeneity. Convex areas exhibit classical sediment-depth-decay patterns with sparse, cooperative microbial communities. Conversely, concave features maintain higher biomass and activity as well as dense microbial interactions. Critically, slope concave sites incubate previously unrecognized microbial hotspots and may serve as interchange hubs, potentially facilitating genetic exchange and upward dispersal of microorganisms from Earth's deepest regions to the broader ocean. Our findings demonstrate that topographic features, rather than water depth, significantly correlate with organic carbon influx and its microbial turnover rates, enabling predictive modeling of hadal carbon cycling with global implications.