Image of “Watermelon Snow” or “Pink Snow” organism found in the Sierra Nevada mountains of California. The source of the pink color is a single-celled algae formerly called Chlamydomonas nivaloides, now renamed to Sanguina nivaloides. This genus contains two species: S. nivaloides which makes pink snow, and S. aurantia which makes orange snow. These algae produce a carotenoid (astaxanthin) that protects its photosynthetic pigments from UV damage. The algae are dormant during the summer and snow-covered winter months. During the Spring however, the snow melts creating liquid water. This stimulates germination producing green flagellated cells that swim to the surface. Here the cells shed the flagella to form these photosynthetic cells, or cysts. Each Sanguina cyst contains a single chloroplast surrounding a nucleus, with the remaining cytoplasm filled with red astaxanthin. No culturable strains exist, thus the vegetative and reproductive stages are unknown. Sanguina nivaloides is referred to as a cryophillic/extremophillic algae as it is found only in alpine snowfields. This sample was collected above 9000′ near Mammoth Mountain, CA. Scalebar = 20µm.
Steve Ruzin, curator of the Golub Antique Microscope Collection, UCB