Persistent Desert Microbiota in the Southern European Sky

Long-range atmospheric processes facilitate global microbial dispersal, with a pivotal role in Earth's ecosystem functioning and global health. Aerobiological studies have traditionally focused on low troposphere aerosols, leading to the assumption that airborne communities are primarily controlled by neighbouring ecosystems. We show a temporal sampling of aerosols from the free troposphere extending a period of almost three decades, coupled with the study of both high troposphere air masses provenances and genetic data of topsoils from North Africa and from a global public bacterial database. The results unveil a long-lasting influence of airborne North African desert microorganisms in Southern Europe. Although sea spray dominates global aerosol emissions, the predominance of desert microorganisms was widespread even in rain traced back to the Atlantic Ocean. The frequency of dust outbreaks, altitude reached, and long residence times are postulated as critical factors that significantly shape the long-range and persistence of aerial assemblages, with air mass provenance playing a secondary role. This study advances the current understanding of atmospheric microorganisms, underscoring their close and long-lasting relationship with terrestrial ecosystems. Further research is needed to fully understand intercontinental aerial connections with deserts and drylands elsewhere, and the influence of desert immigrants on worldwide ecosystems.