Microbial drivers of chemical weathering and CO2 cycle in small island orogen

Chemical weathering modulates carbon transfers between the crust, the hydrosphere, and the atmosphere, exerting a profound impact on landscape evolution, ecosystem sustainability, and climate change. The extent to which microbial processes are involved in and potentially accelerate mineral dissolution remains elusive. Here we performed geochemical and molecular analyses on river water and other materials collected from a rapidly uplifting catchment in eastern Taiwan. In addition to solute generation driven primarily by pyrite-induced carbonate weathering, highly skewed microbial community compositions with abundant Sulfuricurvum and Thiobacillus members were detected for high-water periods after typhoons or storms. The data pattern, combined with high sediment yields, indicates that carbonate weathering is catalyzed by sulfur-respiring microorganisms that inhabit bank sediments, talus deposits, or bedrocks, which are subsequently remobilized by channel incision and transport, and mass wasting. The net CO2 export from mineral weathering greatly surpasses the global average and those observed in other mountainous catchments, highlighting active orogens in high-standing islands as a significant CO2 contributor rendered by tandem biotic and abiotic processes.