Snow algae are a group of green algae (Chlorophyta) that turn red because they make pigments that are bright colors. Don’t be fooled by Wikipedia and other sources that say all pink snow is the species Chlamydomonas nivalis. There are many different snow algae species described by researchers around the world, and many algae once called Chlamydomonas nivalis have been renamed into other groups. If you see pink, red, orange, or green snow, it’s likely algae growing there and likely its a thriving community of microbes including lots of bacteria, fungi, single-cell predators that eat algae and bacteria.
The algae are complex cells (eukaryotes, cells with a nucleus), have complex life cycles, and live in diverse ecosystems.
See this short talk by LSP founder Dr. Robin Kodner for the Northwest Avalance Center annual snow science meeting 2017 for the basics of snow algae and why we study it: