Snowfall is a global phenomenon highly integrated with hydrology and ecology. Forays into studying bioaerosols and their dependence on aeolian movement are largely constrained to either precipitation-independent analyses or in silico models. Though snowpack and glacial microbiological studies have been conducted, little is known about the biological component of meteoric snow. Through culture-independent phylogenetic and geochemical analyses, we show that the geographical location at which snow precipitates determines snowfall’s geochemical and microbiological composition. Storm-tracking, furthermore, can be used as a valuable environmental indicator to trace down what factors are influencing bioaerosols. We estimate annual aeolian snowfall deposits of up to ∼10 kg of bacterial/archaeal biomass per hectare along our study area of the eastern Front Range in Colorado. The dominant kinds of microbiota captured in an analysis of seven snow events at two different locations, one urban, one rural, across the winter of 2016/2017 included phyla Proteobacteria, Bacteroidetes, Firmicutes, and Acidobacteria, though a multitude of different kinds of organisms were found in both. Taxonomically, Bacteroidetes were more abundant in Golden (urban plain) snow while Proteobacteria were more common in Sunshine (rural mountain) samples. Chemically, Golden snowfall was positively correlated with some metals and anions. The work also hints at better informing the “everything is everywhere” hypotheses of the microbial world and that atmospheric transport of microbiota is not only common, but is capable of disseminating vast amounts of microbiota of different physiologies and genetics that then affect ecosystems globally. Snowfall, we conclude, is a significant repository of microbiological material with strong implications for both ecosystem genetic flux and general bio-aerosol theory.

24Snowfall is a global phenomenon highly integrated with hydrology and ecology. Forays 25 into studying bioaerosols and their dependence on aeolian movement are largely constrained to 26 either precipitation-independent analyses or in-silico models. Though snowpack and glacial 27 microbiological studies have been conducted, little is known about the biological component of 28 meteoric snow. Through culture-independent phylogenetic and geochemical analyses, we show 29 that the geographical location at which snow precipitates determines snowfall's geochemical and 30 microbiological composition. Storm-tracking, furthermore, can be used as a valuable 31 environmental indicator to trace down what factors are influencing bioaerosols. We estimate 32 annual deposits of up to ~10 kg of bacterial / archaeal biomass per hectare along our study area 33 of the eastern Front Range in Colorado. The dominant kinds of microbiota captured in an 34 analysis of seven snow events at two different locations, one urban, one rural, across the winter 35 of 2016/2017 included phyla Proteobacteria, Bacteroidetes, Firmicutes and Acidobacteria, 36 though a multitude of different kinds of organisms were found in both. Taxonomically, 37Bacteroidetes were more abundant in Golden (urban plain) snow while Proteobacteria were 38 more common in Sunshine (rural mountain) samples. Chemically, Golden snowfall was 39 positively correlated with some metals and anions. The work also hints at better informing the 40