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Snow News is Good News

Photo: Red snow in morning, skier take warning. Skiing on Reynolds Peak in mid-June.

Watermelon Snow (Chlamydomonas nivalis)

Shelly Forster

What the heck?
Red snow. If you’ve wandered the alpine zone during late spring or summer, chances are you’ve seen it. Does this mean you’ve stumbled across evidence of a homicide? Maybe. More likely, though, you’ve discovered a patch of Chlamydomonas nivalis, which is also known as watermelon snow or red snow.

Why is it red?
Alpine environments receive a lot of UV radiation that can fry DNA, so the algae in watermelon snow produce red carotenoid pigments as internal sunscreen. These are different from the red anthocyanin pigments that cause red colors in autumn leaves.

Where can I find it?
C. nivalis is easy to find in mid to late summer in the Northwestern alpine zone. This year, we found a sizable patch on Rock Mountain in late September. Red, green, and orange snow algae also grow in the Northeastern United States in areas that have a hefty annual snowpack.

What happens in the off-season?
Over the summer, red snow algae eat, grow, and multiply. When they’ve depleted the nutrients in the snow, they reproduce and go dormant for the year. When snow hits in the fall, the algae remain covered until snow begins to melt again in the spring. When the snow algae reappear in spring they may be spread to new areas by hitchhiking on the bottom of hiking boots, skis, or animal feet.

Who cares?
Because snow is such an extreme environment (cold, acidic, and nutrient poor), NASA researchers study snow and ice microbes like red snow algae as they hunt for extraterrestrial life on frigid worlds like Mars and Jupiter’s moon Europa.

Can I eat it?
We wouldn’t. Starving hikers may wonder if snow algae can be used as a survival food, but one desperate hiker in Colorado was hospitalized with acute diarrhea and dehydration after swallowing too much red snow. Generally, if the snow is colored, let it be.


Editor's Note: Thanks to Dr. Ron Hoham (Professor Emeritus, Colgate University) for the information and for years of dedicated snow algae research in the Cascades. For more background and to see snow algae under a microscope, check out his 2004 article in Wildflower