Spatiotemporal dynamics in airborne fungi and allergenic fungal taxa across the United States

A broad diversity of fungi can be found in the near-surface atmosphere, with both the amounts and types of airborne fungi varying across space and time. However, specific spatiotemporal patterns in airborne fungal assemblages often remain unquantified. This knowledge gap is particularly notable for allergenic fungi, despite the relevance of airborne exposures to allergenic fungi to public health. To better understand how airborne fungi, including allergenic fungal genera, vary across broad spatial and temporal scales, we leveraged a pre-existing air sampling network to obtain bioaerosol samples from seven national parks representing diverse biome types across the United States, with samples collected from each site every three days over an entire calendar year. We used marker gene DNA sequencing and quantitative PCR to characterize fungal assemblage composition and concentrations, including concentrations of ten genera known to include allergenic species. As expected, the composition of the airborne fungal assemblages, including the amounts and types of allergenic fungi, varied across biomes. We also observed substantial temporal variation in the total amounts and types of fungi detected, particularly at higher latitude sites. While some of the temporal variation in allergenic fungal concentrations followed seasonal patterns, we detected pronounced daily and weekly fluctuations in taxon-specific concentrations, with higher wind speeds generally associated with higher allergenic fungal concentrations. Together, these results expand our understanding of fungal aerobiology across natural ecosystems and demonstrate how combining extensive air sampling efforts with DNA-based analyses can improve assessments of public health risks associated with exposure to allergenic fungi in outdoor air. IMPORTANCE: Despite major advances in sampling methodologies, sequencing technologies, and access to air quality monitoring networks, comprehensive assessments of the spatial and temporal variation in airborne fungi remain limited, even though fungi constitute a substantial proportion of the aerobiome. This is true even for allergenic fungal taxa, despite their importance to human health. Using DNA-based approaches, we characterized fungal assemblages in the near-surface atmosphere over a single calendar year at seven national parks across the US. We found that each site had distinct airborne fungal assemblages with unique temporal patterns in fungal concentrations and composition. Substantial spatiotemporal variation was also observed for known allergenic fungi, driven by both seasonal trends and environmental factors. This study advances our understanding of the ecological patterns that structure airborne fungal communities and the factors influencing outdoor exposures to allergenic fungi, improving our ability to assess and predict health risks.