Amazonian rainforest bioaerosol influenced by African dust intrusion

Biological particles are an important but poorly understood component of Amazonian aerosols, having impacts on ecosystems, climate and human health. Here, we show that African dust plumes transport microbial communities across the Atlantic into the Amazon rainforest. We characterize the bacterial, fungal, and archaeal communities at 42 and 323 m above ground at the Amazon Tall Tower Observatory, both during background conditions and a five-day North African dust intrusion. Under background conditions, bacterial communities vary with height and time, reflecting diverse local and transported sources, whereas fungal communities remain stable and are dominated by locally produced fungi. During the dust intrusion, bacterial communities shift strongly towards microorganisms associated with dryland soils, biological soil crusts, and marine environments, while fungal communities remain unchanged. Additionally, airborne endotoxin concentrations increase threefold, without enriching obligate pathogens. Our findings demonstrate that African dust is not only a mineral nutrient source but also a vector of intercontinental microbial transport, with potential consequences for ecosystem functioning, atmospheric processes and human health.