Responses of fluorescent bioaerosol and microbial community composition to local meteorology

Primary biological aerosol particles (PBAP) are major contributors to supermicron atmospheric aerosol loading, carriers of pathogens, and enablers of plant and fungi propagation. As potential cloud condensation nuclei and ice-nucleating particles, PBAP can impact precipitation and the hydrological cycle. However, bioaerosols are poorly studied over natural ecosystems. We measured fluorescent bioaerosol at the Northern Colorado Plains in Fall 2022, determined the major bioaerosol types, and quantified the meteorological drivers of bioaerosol concentration using ultraviolet light induced fluorescence. We observed nighttime enrichment of 2–9 µm ABC-, AB-, and BC-type particles, which we attribute to fungal spores and fragments, as well as A- and B-type particles < 2 µm, which we attribute to bacteria and fungal fragments. The major identifiable fungal and bacterial phyla were Ascomycota and Actinobacteria, respectively. In the absence of rain, particles were moderately correlated with solar radiation (−0.41 < rs < −0.45), temperature (−0.41 < rs < −0.54), and surface wetness (0.40 < rs < 0.43). Most precipitation and extreme humidity events were accompanied by enriched fluorescent particle concentrations and increased relative abundance of Basidiomycota spp. However, the relationships between fluorescent particles and environmental factors are not well described by any regression model, suggesting complex and mixed links between PBAP and meteorological factors that may be complicated by long-range particle transport. These measurements suggest that bioaerosol enrichment occurs over grasslands under combinations of conditions associated with precipitation and extreme humidity, rather than systematically following cycling of environmental variables.