Abstract

Microbial communities in Antarctica's snow and atmosphere are critical for nutrient cycling and are highly sensitive to environmental change. We characterised the bacterial composition, diversity, and co-occurrence network structure of surface snow and airborne microbiomes from two contrasting bays along the Western Antarctic Peninsula (WAP): Arturo Prat Base (APB; Chile Bay, Greenwich Island) and Yelcho Base (YB; South Bay, Doumer Island), sampled during consecutive austral summers (2022–2023). Surface snow and air samples were analysed using 16S rRNA gene sequencing, diversity indices, and network analyses to evaluate spatial and interannual dynamics. Proteobacteria and Bacteroidota dominated both environments, but community structures differed between sites: APB showed stronger local and anthropogenic signals near logistic stations, whereas YB reflected more stable deposition regimes and distant atmospheric inputs. Airborne communities displayed limited interannual variation and high compositional similarity between sites, consistent with atmospheric seeding by polar air masses. Co-occurrence networks revealed denser, more structured interactions within snow communities, with keystone taxa linking snow and air, sustaining deposition–resuspension dynamics. These findings highlight that long-range atmospheric transport and local conditions shape Antarctic microbial dynamics, providing insights for forecasting microbiome responses and assessing airborne health risks amid human activity and climate change in polar regions.