Identification and characterization of microbial communities in high elevation snow packs

Microbial communities play a key role in food web dynamics of marine, freshwater and soil ecosystems.  Often, microbial communities are the only source of primary production in oligotrophic environments such as alpine soils or snow packs where they can affect nutrient availability to lower elevation ecosystems.  With over 1 billion people relying on high elevation snow packs for freshwater, the need to understand microbial processes in snow is important.  Unfortunately, the diversity of microbial communities found within the snow packs of high elevation ecosystems has been poorly described and based mostly on morphological descriptions.  Melting snow packs provide a good environment for snow algae that migrate through the pack to the snow’s surface.  However, algae may not be the only organisms capable of exploiting this environment.  Microscopic examination of snow has revealed the presence of fungi and bacteria in addition to algae but modern phylogenetic and ecological analyses are lacking for these communities.  Additionally, information about the global geographic distributions of these organisms is lacking.  In this study we use phylogenetic and community analyses to describe eukaryotic snow organisms from the high elevation snow packs of the Colorado Rocky Mountains and compare them to snow communities from other similar environments around the world.  A deeply divergent and previously undescribed clade of zoonotic fungi (chytrids) was discovered in snow samples from Colorado, Switzerland and France.  This clade is particularly unique in that it only contains environmental sequences from high elevation sites.  Experimental manipulations and microscopic analyses of the snow environment indicate that these novel fungi are probably utilizing aeolian deposited pollen and dust for nutrients and may be preying upon snow algae and pollen for a source of carbon and energy.  Ongoing studies of the unique nival communities should help us to understand their contribution to snow foodweb dynamics and possible effects on downstream water quality.