Long-range transatlantic dust transport: via hitchhiking to South America

Primary biological aerosols (bioaerosols) represent the predominant fraction of aerosols within the Amazon rainforest, a global biodiversity hotspot. Bioaerosols encompass a wide range of biological material. These can be single molecules such as proteins, carbohydrates, metabolites, toxins and allergens, or as large as whole dispersal units such as pollen, fungal and cryptogamic spores. They also include whole living or dead microbial organisms such as viruses, bacteria, archaea, or fungi, and fragments or secretions from organism. These bioaerosols can serve as nuclei for ice crystals and cloud droplets and thereby influence the properties of clouds and precipitations patterns with implications for hydrological cycles and the climate. Moreover, the aerial transport of microorganisms contributes to global species spread, with the potential to affect animal, plant, and ecosystem health. Aerosolized soil particles (dust) can act as vehicles, enabling microorganisms to traverse extensive distances, such as the Atlantic Ocean. However, the identity and effects of microorganisms associated with long-range transported dust masses on the local bioaerosol community of the Amazon rainforest is still unknown.Here, we investigate the effect of dust, originating from the African continent and transported to the Amazon rainforest on the local microbial and fungal bioaerosol community of the Amazon rainforest. We collected total suspended particles at the Amazon Tall Tower Observatory (ATTO) in Brazil before, during and after a dust event, at 42 m and 320 m height. The prokaryotic and fungal communities were analyzed using amplicon sequencing techniques. Our results revealed a distinct local fungal and procaryotic bioaerosol community under dust free conditions. However, dust occurrence did not majorly effect the fungal community structure, which showed an overall very uniform core microbiome, across time and height. In contrast, the prokaryotic community was strongly altered during the dust event, with members of the Bacillota strongly increasing. Also, the prokaryotic core microbiome was smaller compared to the fungal core microbiome and changed between heights. Our findings suggest that the Amazon rainforest air microbiome can be affected by long-range transported dust and the microbial communities transported within while the fungal air microbiome seems overall more stable. Suggesting the transcontinental exchange of dust between Africa and South America as a plausible pathway for the spread of prokaryotes.