Snow Algal Community Diversity and Pigment Expression in Response to Light Intensity

Abstract

Snow algal microbial communities have become a topic of scientific interest due to their link with accelerated snow melt in the changing climate. In addition to reducing the surface albedo of snow, algal metabolic processes and photoprotective pigments play a role in producing and trapping heat, causing further melt and subsequent flooding and erosion. Given the role of light in both photosynthesis and photoprotection, it begs the question of how light affects snow algal communities particularly at high elevations. This study aimed to determine how different light intensities affected the algal species composition and pigment expression of snow algal communities cultured from field samples collected in the Beartooth Mountains. Sample DNA extraction and 18S rRNA amplicon sequencing allowed comparison of the eukaryotic diversity before and after two weeks of treatment with high and low light intensities, using two different media (soil extract and snow algae media). An acetone pigment extraction was also performed before and after treatment to determine the concentration of major pigments in each sample. The diversity and absorbance data from before and after treatment were compared to determine how the snow algal communities changed, with the expectation that higher light intensity would increase production of photoprotective pigments such as astaxanthin. It was also hypothesized that the cultures treated with different light intensities would have significantly different algal community composition due to the competitive advantage of some species in high-light environments. Sequencing data showed no statistically significant differences for soil extract medium cultures, while snow algae medium cultures showed significant differences in community composition with respect to medium, light intensity, and time period, as well as when compared to the soil extract medium cohort. Pigment composition lacked any significant differences between groups. Results from this study will help scientists better understand how snow algal communities can affect future snow melt in different light conditions, allowing for more effective biocontrol measures and preparedness in the event of downstream flooding. Future directions for this study could involve culturing these algal communities for longer periods of time in response to temperature or humidity.