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Snow in alpine and polar regions takes on a pinkish hue during the summertime. This “watermelon snow” or “red snow" is caused by blooms of microscopic algae and their associated microbiome, including fungi, ciliates, bacteria, archaea and viruses. While white snow reflects solar radiation, red snow absorbs more energy from the sun, speeding snowmelt and increasing algal growth. In British Columbia, this could affect watersheds where high elevation snowpacks produce the flow of water into salmon streams and drinking water reservoirs. We know that red snow accelerates warming and melting, but need more information about the distribution, seasonal progression and biology of snow algae microbiomes.  

      The research team discovered a surprising amount of snow algae diversity in distinct but overlapping communities from the southwestern mountains of the Coast Range in BC. Some species were present in all blooms, while others were found only at low elevations or in the high alpine.  In contrast to the distribution of algae, there were no clear altitudinal distributions of bacteria and other associated organisms. Genomic and microscopic studies revealed that the blooms comprised many unknown algae species and resulted in the proposal of two new species: Raphidonema catena and Raphidonema monicae.  

To understand the role of bacteria in snow algae blooms, the team constructed metagenomically assembled bacterial genomes (MAGs) which fell into five classes: Actinomycetia, Alphaproteobacteria, Bacteroida, Betaproteobacteria and Gammaproteobacteria. Several MAGs contained metabolic genes that could facilitate interactions between bacteria and algae and support growth in low-oxygen conditions, which may occur in the biofilms commonly observed in snow algae blooms. 

In addition to the above, the team created a BC Snow Algae Biobank and established a framework for a complex food web with predation on snow algae. From these foundational data, we can begin to understand the complex cooperative relationships underlying the existence of this remarkable microscopic ecosystem.