Watermelon snow

[CHLAMYDOMONAS NIVALIS]

Watermelon snow tints the landscape with a pink blush so subtle that hikers may blink to make sure their eyes aren’t bewitching them. It’s not a high-altitude hallucination but colorful evidence of a microorganism that lives entirely in snow. Distributed by wind as spores, these strange microorganisms hatch in early summer into four mobile “daughter cells” that swim to the melting surface of snowfields. Although the cells have animal-like eyespots, they possess chlorophyll and feed on sunlight energy, as well as nutrients in windblown dust. Each cell also contains a tiny speck of red pigment that absorbs the sun’s heat like a warming oven. By midsummer, the concentrated cells form a color noticeable to passing hikers.

NATURAL HISTORY

These microorganisms are so abundant on snowfields worldwide that they may play an important and beneficial role in the cycle of greenhouse gases. They also anchor the surprisingly diverse food chain found in snow, and are eaten by creatures such as snow worms, protozoans, spiders and insects.

KEY CHARACTERISTICS

More than 100 types of Chlamydomonas come in a variety of yellows, greens and purples, but the pink species is most common.