Exploring local and regional contribution to airborne bacterial communities in the Antarctic Peninsula

Understanding microbial dispersion in the atmosphere is essential for studying microbial biogeography and ecosystem dynamics under global change. Airborne bacterial communities, shaped by exchanges between atmosphere and Earth's surface, can originate from diverse sources and vary with meteorological conditions and air mass trajectories. In this study, we assessed airborne microbial communities in Antarctica at regional and local scales. Air samples were collected during the austral summer at two Antarctic Specially Protected Areas (ASPAs): Byers Peninsula (Livingston Island, South Shetland Islands) and Avian Island (Marguerite Bay). Bacterial composition was analysed through 16S rRNA gene sequencing using amplicon sequence variants (ASVs). Additionally, back-trajectories of the sampled air parcels were simulated with HYSPLIT. A core community was identified in 80% of Byers Peninsula samples, representing 57.91% of total ASVs. Notably, 79.4% of ASVs matched soil bacteria from the same location, suggesting a strong influence of local sources. Communities from Byers Peninsula and Avian Island showed low overall similarity. However, one sample from Byers resembled the Avian sample, likely due to similar air mass back-trajectories. These findings suggest that airborne bacterial communities are shaped by both local ecosystems, and broader regional or continental processes, such as long-range trajectories carrying microorganisms from distant locations.