Micropressure Enhances Microbially Mediated Green Hydrogen Production Capacity of a Deep-Water Reservoir

Reservoir sediments contain organic matter that can be converted to hydrogen (H2) via anaerobic fermentation. To determine whether micropressure enhances sedimentary green hydrogen production, we conducted 30 day anoxic microcosms using sediments from a deep-water reservoir in northwest China and imposed hydrostatic pressures of 0.1, 0.2, 0.5, and 0.7 megapascal (MPa). Microbial community structures, functional genes, and metabolic pathways were characterized by metagenomics and metabolomics. The overall abundance of putative hydrogen (H2)-producing taxa rose from 0.1 MPa to 0.2–0.5 MPa and declined at 0.7 MPa, indicating peak reproductive potential at 0.2–0.5 MPa. Relative to 0.1 MPa, elevated pressures reduced the proportions of bacteria and fungi by mean values of 0.17% and 0.02%, respectively, while that of archaea increased by 0.19%. Higher pressure strengthened microbial co-occurrence networks and increased inferred community stability; keystone taxa were mainly Proteobacteria. Increased pressure upregulated glycolysis and butanoate-metabolism genes (glk, ppgK, fadJ, atoA) and enzymes linked to butanoate metabolism, accelerating turnover of glucose and intermediates (glycerol-3-phosphate, acetoacetate). These pressure-driven shifts suggest enhanced fermentative flux and a greater capacity for H2 release, providing a basis for strengthening in situ reservoir-sediment hydrogen production and hydrogen-rich irrigation water.