Watermelon snow caused by algae.
Watermelon snow is not a delicious shaved ice treat. Originally observed by Aristotle, watermelon snow can be found hiking on snowfields, for example, the often snow-covered Sierra Nevada mountains of California.
The pinkish-red color is caused by the algae Chlamydomonas nivalis. Snow is limited in nutrients and obviously very cold, but C. nivalis thrives in these conditions.
Their winter bodies are red, dormant “cysts” that allow them to survive. The red pigment helps protect them from intense UV radiation experienced at high elevations and in ecosystems with no shade protection. In spring and summer, they are mobile, green cells.
Small creatures, like rotifers, nematodes, ice worms and springtails, feed on the algae in watermelon snow.
However, recent research shows that even snow that is pristine, white, or freshly-fallen is full of microbes, particularly the species that are considered snow algae. These same snow algae species can be found in snowfields across the globe, which is surprising since other microbial species in the same environment show patterns in their distribution between snow-covered areas.
Unfortunately, watermelon snow may contribute to faster warming rates because they reduce the reflectivity, or albedo, of white snow, which helps keep the snow cooler. Scientists, mainly from the University of Leeds, published a study that estimates that watermelon snow causes a 13% reduction in albedo and will likely cause faster melting rates.
The impact of watermelon snow and other living organisms should be incorporated into models examining melt rates and albedo.
More information on watermelon snow can be found here.
