Environment Planet Earth 'Blood Snow' Invades the Antarctic By Starre Vartan Writer Columbia University Syracuse University Starre Vartan has been an environmental and science journalist for 15-plus years. She founded an award-winning eco-website and wrote a book on living green. our editorial process Starre Vartan Updated February 13, 2021 Clamydomonas nivalis, a unicellular alga on snow in Antarctica. (Photo: Rik Oggioni/Shutterstock) Share Twitter Pinterest Email Planet Earth Weather Outdoors Conservation Aristotle called it "watermelon snow," and some scientists call it "raspberry snow" but first impressions give way to something more macabre than these innocent nods to summer treats convey. To be clear, the red color you are seeing in the images above and below isn't caused by melons, raspberries or blood. It's created by large communities of Chlamydomonas nivalis. Like most algae you may be familiar with, it's green, but it makes the red color as a defense against UV radiation, to protect itself from genetic mutations while still absorbing light. The algae lies dormant all winter and when warmer weather comes, typically in the summer, it flourishes, spreading out through the snow in various patterns including stripes and blobs. At that time of year, it also serves as a food source for a variety of life forms, including ice worms and nematodes. Some scientists think the record melting occurring on ice sheets around the world is caused by a 'bio-albedo' effect of a certain kind of algae. (Photo: gary yim/Shutterstock) So the fact that this algae exists isn't the story — it's where and when it's showing up. For most of February, the ice around Vernadsky Research Base, located on an island off the coast of the northernmost peninsula of Antarctica, has been streaked and blobbed with the bright red algae. (You can see more images at the research base's Facebook page.) This is likely due to the very warm temperatures the Antarctic has experienced this winter, which has been making headlines. It's so warm, the algae thinks it's summer — and because the red color of the algae doesn't reflect back light as well as white snow does, scientists in the Arctic have already shown that this extra heating exacerbates warming conditions, creating a feedback loop. As the Ukranian scientists explained on their Facebook page: "Because of the red-crimson color, the snow reflects less sunlight and melts faster. As a consequence, it produces more and more bright algae." The warmer the temperatures, the more algae, which hold more heat into the snow, which creates more melting.