Functional niche partitioning influences species turnover across supraglacial microbial communities on the Longxiazai glacier, Tibetan Plateau

Glaciers represent unique ecosystems harboring diverse microbial communities that dominate biomass and drive biogeochemical cycling across supraglacial habitats. These microbes transform deposited modern and ancient carbon/nitrogen, and these elements are subsequently transferred to downstream ecosystems via glacier melting, further affecting downstream ecological succession, functions, and stability. Despite such ecological significance, our understanding of the mechanisms underlying microbial functional adaptation to different supraglacial habitats remains limited. We integrated 16S rRNA amplicon and metagenomic sequencing to systematically compare taxonomic composition and functional potential across snow, ice, and cryoconite in the ablation zones of Longxiazai glacier on the Tibetan Plateau. Our analyses revealed pervasive functional redundancy, with 94% of genes shared across habitats and 6% of genes were habitat-enriched and exhibited strong niche-specific patterns. Cryoconite microbiomes were distinguished by enhanced genetic potential for ribosome biogenesis, antiviral defense, and antioxidant mechanisms, consistent with adaptation to biotic interactions and anoxic conditions. In contrast, snow and ice communities were enriched in cold-resistant and radiation-tolerant functions, including genes mediating cell morphology, biofilm formation, and DNA repair. Habitat-enriched genes displayed lower redundancy indices than other genes, indicating strong environmental selection, and taxa carrying these genes were more abundant in their respective habitats, highlighting functional trait selection as a driver for microbial species turnover. These findings elucidate how divergent selective pressures shape functional diversification in supraglacial microbiomes, with implications for predicting microbial-mediated processes under accelerating glacier retreat. This study emphasizes the importance of preserving functional biodiversity in glaciers to sustain ecosystem stability and downstream biogeochemical fluxes. Video Abstract