Snow Algae: Adaptation Strategies to Survive on Snow and Ice

Abstract

Snow algae are a group of freshwater microalgae that have encountered the extreme habitats of persistent snow and glacier fields in the polar and high-alpine regions of our earth. In suitable locations they can build up massive blooms resulting in a macroscopically visible pigmentation of the snow (Fig. 1). The dominating species belong to the green algae (Chlorophyta), and depending on the life cycle stages and dominating pigments observed, this results in green and different shades of orange, pink, or red snow – for the latter three hereafter I will use the term “red snow” only. Green snow is caused by the trophic, actively dividing sexual or asexual cells stages, whereas red snow is the result of their carotenoid-rich resting stages, such as hypnospores or hypnozygotes. Other snow tints have been described referring to other taxonomic groups, e.g., purple-grey ice caused by the Zygnematophyceae Mesotaenium berggrenii or Ancylonema nordenskiöldii.