Microbial dispersal from a hyperactive sandsheet in the Icelandic Highland.

Atmospheric transport is an important mechanism for microbial dispersal around the world. Consequently, the coupling of atmospheric and soil ecosystems plays an important role in the global biosphere and biogeochemical cycles. We use the hyperactive Dyngjusandur sandsheet in the Icelandic highlands, a significant contributor to the global dust cycle, as a case study to link bioaerosol communities to local surface sources and show how meteorological conditions shape the dynamics of airborne microorganisms. Our findings reveal that the atmosphere over this sandsheet contains a unique community, whose structure responds dynamically to wind speed and atmospheric pressure, specifically major storm systems that alter both prokaryotic and eukaryotic populations. Source tracking revealed that storm events increased the contribution of sand-associated microorganisms to the atmosphere (up to 76%), blurring the distinction between airborne communities and their terrestrial sources-including sand, diurnal floodplains, and fluvial environments. Microorganisms were preferentially attached to morphologically complex dust particles emitted from the sandsheet, potentially increasing survivability in the atmosphere. Culturing confirmed the presence of viable, cold-adapted and stress-tolerant taxa, suggesting potential for atmospheric persistence. Forward trajectory modelling suggests that bioaerosols emitted from the sandsheet could reach major population centers in Europe. Those microorganisms could have impacts on human health, agriculture, biogeochemical cycles, and ecosystems.