Spatiotemporal dynamics in airborne fungi and fungal allergens across the United States

Abstract

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, the specific spatiotemporal patterns in airborne fungal assemblages often remain unquantified. This knowledge gap is particularly notable for allergenic fungi, despite the relevance of airborne fungal allergen exposures to public health. To better understand how airborne fungi, including known allergens, vary across broad spatial and temporal scales, we leveraged a pre-existing air sampling network to obtain bioaerosol samples from 7 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 the concentrations of ten known allergenic genera. As expected, the composition of the airborne fungal assemblages, including the amounts and types of known allergens, 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 allergen abundances followed seasonal patterns, we detected pronounced daily and weekly fluctuations in taxon-specific allergen abundances, with higher wind speeds generally associated with higher fungal allergen 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. IMPORTANCEDespite 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 7 national parks across the US. We found that each site had distinct airborne fungal assemblages with unique temporal patterns in fungal abundances and composition. Substantial spatiotemporal variation was also observed for known fungal allergens, 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 associated with fungal allergens.