The microbial diversity of watermelon snow

During summer months in alpine systems around the world patches of green, orange and red snow appear. The phenomenon is sometimes called watermelon snow and is caused by a bloom of microalgae. The resulting microbiome is teeming with life, including algae, fungi, metazoans, other protists and bacteria. Here, I present data documenting the biological diversity in the ephemeral snow algae microbiome, which grows on snows threatened by global warming. I began by asking: what microbes are found in snow algae blooms? I focussed my work in the southwestern Coastal Mountain Range in B.C., Canada. The data I present detail the algal, bacterial, fungal, metazoan and other protist diversity in blooms and their distribution across the region. These data included sequences from undescribed algal species, with some potentially belonging to species names with no DNA data available. I therefore did an analysis, including five novel algal isolates, to clarify the taxonomy of Raphidonema and its sister genera, using genetic data. I was able to identify my five isolates as R. sempervirens, and in the process name two novel species: R. catena and R. monicae. As bacteria are commonly important mutualistic symbionts of microalgae, I next described their communities living alongside snow algae. I found that, unlike algae, the bacterial community composition does not change with elevation, and instead there are regionally widespread bacteria. I therefore wanted to learn more about the metabolic capabilities of these bacteria common to snow algae blooms. Using a shotgun metagenomics approach, I analyzed the bacterial metagenome, and metagenomically assembled genomes. These data included representative from the widespread bacterial families found during metabarcoding, and I furthered that analysis by describing their metabolic genes related to: nitrogen and sulfur cycling as well as biosynthesis of osmolytes/cryoprotectants, B-vitamins, phytohormones, and xanthophyll pigments. These data act as observations to form hypotheses on the biogeochemistry and microbial ecology of snow algae microbiomes.