Effects of Annual Snowpack Variability on Alpine Snow Algae Communities in the Cascade Mountains

Abstract:

Snow algae are a group of closely related photosynthetic microbial eukaryotes found in the polar and alpine snowpack. These organisms bloom seasonally as their environment becomes habitable in the spring and summer months, and blooms turn snow pink, red, orange and occasionally green as a results of cellular pigments. Blooms are believed to be driven mostly due to the availability of liquid water in the snowpack, though little is known about dispersal mechanisms and how communities are maintained over time. This is especially true for snow algae that bloom in low elevation seasonal snowpack that is ephemeral and only habitable for a short time each year. To assess changes in community structure over seasonal and annual time scales in ephemeral snow, we have characterized the snow algae communities using microscopy and DNA amplicon sequencing across a three year period 2017-2019 in a single basin in the Cascade Mountains in Washington State. The Cascades are a low elevation mountain range with a maritime snowpack that experiences significant annual variability affecting both the depth of peak snowpack and the timing and rate of spring and summer melt. This study creates a framework for defining what we refer to as the snow algae “growing season”: when conditions are favorable for the emergence, growth, and development of snow algae, for a specific geographic location. We used available snow and climate data from SnoTel repositories in addition to model estimated snow depths from satellite imagery to quantify snow depths and melt rates over the 2017-2019 growing season in Bagley Basin. Our results suggest consistency in community structure related to the timing of the growing season.