bioRxiv preprint doi: https://doi.org/10.1101/300772; this version posted April 13, 2018. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 1 Fresh Snowfall Microbiology and Chemistry are Driven by Geography in Storm- 2 Tracked Events 3 4 Honeyman, A. S.1, Day, M.L.1, Spear, J.R.1# 5 6 Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, CO, 7 USA1 8 9 Running Head: The Microbiology and Chemistry of Snowfall 10 11 #Address correspondence to John R. Spear, [email protected]. 12 13 Keywords: Snow, microbial ecology, aerosols, aerosol chemistry, remote sensing 14 15 16 17 18 19 20 21 22 23 1 bioRxiv preprint doi: https://doi.org/10.1101/300772; this version posted April 13, 2018. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 24 Abstract 25 Snowfall is a global phenomenon highly integrated with hydrology and ecology. Forays 26 into studying bioaerosols and their dependence on aeolian movement are largely constrained to 27 either precipitation-independent analyses or in-silico models. Though snowpack and glacial 28 microbiological studies have been conducted, little is known about the biological component of 29 meteoric snow. Through culture-independent phylogenetic and geochemical analyses, we show 30 that the geographical location at which snow precipitates determines snowfall’s geochemical and 31 microbiological composition. Storm-tracking, furthermore, can be used as a valuable 32 environmental indicator to trace down what factors are influencing bioaerosols. We estimate 33 annual deposits of up to ~10 kg of bacterial / archaeal biomass per hectare along our study area 34 of the eastern Front Range in Colorado. The dominant kinds of microbiota captured in an 35 analysis of seven snow events at two different locations, one urban, one rural, across the winter 36 of 2016/2017 included phyla Proteobacteria, Bacteroidetes, Firmicutes and Acidobacteria, 37 though a multitude of different kinds of organisms were found in both. Taxonomically, 38 Bacteroidetes were more abundant in Golden (urban plain) snow while Proteobacteria were 39 more common in Sunshine (rural mountain) samples. Chemically, Golden snowfall was 40 positively correlated with some metals and anions. The work also hints at better informing the 41 ‘everything is everywhere’ hypotheses of the microbial world and that atmospheric transport of 42 microbiota is not only common, but is capable of disseminating vast amounts of microbiota of 43 different physiologies and genetics that then affect ecosystems globally. Snowfall, we conclude, 44 is a significant repository of microbiological material with strong implications for both 45 ecosystem genetic flux and general bio-aerosol theory. 46 2 bioRxiv preprint doi: https://doi.org/10.1101/300772; this version posted April 13, 2018. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 47 Importance 48 Snowfall is commonplace to the temperate and polar regions of the world. As an interface 49 between the atmosphere, hydrosphere and earth, snow is responsible for high annual deposits of 50 moisture globally, and, can serve as a ‘water bank’ in the form of both permanent snow fields 51 and glaciers. Essential to general ecosystem function, snow can also be considered a transporter 52 of aerosolized material. Given the magnitude of microbiota deposited by snowfall, which we 53 report, it is likely that biological material within snowfall, with its geochemical underpinning— 54 and the associated genetic banks—have significant downstream ecological effects. 55 Understanding what is contained in snowfall becomes especially urgent in a warming climate 56 where high-impact meteorological and ecological changes are imminent and likely. With 57 climate-induced changes to snowfall patterns, surface ecosystems are likely to be impacted by 58 ensuing changes in microbiota deposition. Thus, the ecosystem function of soils, rock and 59 surface waters are also likely to be impacted; these changes, in turn, greatly influence 60 agriculture, weathering and infrastructure. 61 62 Introduction 63 Throughout temperate and polar regions of the world, snowfall is ubiquitous. 64 Specifically, along the Front Range of eastern Colorado, the mean annual snowfall from 2010- 65 2016 is reported as 97.7 inches in Boulder, Colorado (1). Despite snow’s prevalence, little is 66 known about the biological composition of this massive annual hydrological deposit; meteoric 67 snow is an essential part of yearly moisture input in Boulder, Colorado given that it represents 68 43% of the total precipitation (by liquid water volume) from 2010-2016 (1). Both snow and rain 69 require an initiation surface for atmospheric water to condense into a droplet of water or ice 3 bioRxiv preprint doi: https://doi.org/10.1101/300772; this version posted April 13, 2018. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 70 particle, respectively. Typically, these are thought to be airborne particles of particulate matter, 71 both organic and inorganic of various colloidal sizes (e.g., 0.5 to 8 m) (2, 3). Bioaerosols, 72 defined as particles of a biological nature released from both terrestrial and marine ecosystems 73 into the receiving atmosphere, are considered to be capable of acting as initiation surfaces (4). 74 Recently, bioaerosols have also been suggested as an understudied component of both 75 atmospheric processes and biogeographical fate (5). 76 Bioaerosols are most famous for their potential detrimental effects upon human health 77 from contaminated indoor or other built-environments (e.g., mold and fungal spores) (6). 78 However, even in a benign, typical, outdoor / atmospheric environment, bioaerosols are common 79 and the literature reports source environments (7), seasonal effects (8, 9), and diurnal shifts (10) 80 as factors in atmospheric bioaerosol composition. Furthermore, bioaerosols are known to be 81 components of the estimated 3 Pg annual dust traffic around the globe (11-13). Work has 82 approached the theory that bioaersols are important to climate as a whole (14) by examining in- 83 silico models of microbiological dispersion in the atmosphere (15). With respect to precipitation, 84 the effects of rainfall additions to soil communities has already been shown to be of 85 microbiological community significance at the soil / atmosphere interface (16). Additionally, 86 these works suggest that snowfall, in particular, is even more important in the deposition of some 87 strains of ice-nucleating bacteria Pseudomonas syringae (also a plant pathogen) (17)—from 88 which the man-made snow-making additive Snomax derives (18). In-vivo studies of both 89 atmospheric and hail microorganisms have shown them to be metabolically active (19-23), 90 suggesting that the biomass in the environment from which snowfall derives is not of 91 inconsequence. In addition, microbiota can remain metabolically active throughout the rain / ice / 92 snow nucleation process. What microbiota within rain / ice / snow precipitation look like when 4 bioRxiv preprint doi: https://doi.org/10.1101/300772; this version posted April 13, 2018. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 93 they contact soil and surface receiving waters, however, remains unknown. Beyond the 94 community structure of precipitation microbiota, it is especially unknown how these structures 95 changes as a result of geography and atmospheric events. 96 Bioaerosol literature, in general, is best represented by reports of in-silico bioaerosol 97 movement, aerosol microbial composition and studies of canonical surface constituents such as 98 glaciers and snowpack (24-28). There exists little specific information, however, on the 99 microbiology of snowfall precipitation. The biological composition of snowfall—a massively 100 spatial meteorological event—should be well understood vis-à-vis magnitude and community 101 structure, especially given that precipitation is key to linking atmospheric and surface theory. An 102 aid to such study is the preponderance of weather information available that tracks storm events 103 in multiple-spectral analyses; these data further inform storm trajectories as well as hydrologic 104 source-water locations. 105 To this end, we sampled fresh snowfall throughout the entirety of the 2016-2017 snow 106 season along the Front Range of eastern Colorado. Our investigations include disparate sampling 107 sites (one rural mountain, and one urban plain) to help in the characterization of snowfall with 108 respect to both sampling location—within the same storm—and direction of origin of the storm. 109 We hypothesized