Watermelon snow, also called snow algae, red snow, or blood snow, is Chlamydomonas nivalis, a species of green algae containing a secondary red carotenoid pigment in addition to chlorophyll. This phenomenon is especially common during the summer months in the Sierra Nevada of California where snow has lingered from winter storms, mainly at altitudes of 10,000 to 12,000 feet. Compressing the snow with your boot leaves a distinct footprint the color of watermelon pulp. The snow even has a fresh watermelon scent.
Photo credit: © Michal Renee