Ski Tourism Shapes the Snow Microbiome on Ski Slopes in the Italian Central Alps

Winter sports exert significant anthropogenic pressures on the snow microbiome, affecting the entire alpine ecosystem. The massive usage of artificial snow, human occupation, and the release of xenobiotics like microplastics or ski wax components on ski tracks can profoundly alter snow microbial ecology. Here, we reconstructed the temporal dynamics of the snow microbiome at three sites in the Italian Alps: inside and outside a ski track at the impacted site of Santa Caterina Valfurva and near Cancano lake as an unimpacted control. Using epifluorescence microscopy, 16S rRNA amplicon sequencing, and inferred metagenomics, we found that the snow microbiome inside the track presented a higher load of prokaryotes and viruses. Notably, N₂-fixing microorganisms from cryospheric environments and host-associated taxa, like Terrisporobacter, Clostridium sensu stricto, Enterococcus, and Muribaculaceae, and the opportunistic pathogen Citrobacter characterised the impacted site. These microorganisms could originate from the river water used to produce artificial snow during winter. Our findings highlight the complexity and multifunctionality of the snow microbiome, where microorganisms with different ecological propensities can coexist, and the detectable impact of ski tourism, which enriches host-associated and xenobiotic-degrading microorganisms. This underscores the need for systematic monitoring and protection of the snow microbiome in the Alpine environment from anthropogenic threats.