Red Snow, Green Snow - snow algae

Science News, May 20, 2000 by Susan Milius

It's truly spring when those last white drifts go technicolor

Microbiologist Brian Duval hates this part, so let's just deal with the snickering up front. Yes, he studies yellow snow.

He also studies red, green, and orange snow and would love to examine other colors if he were lucky enough to discover them. His palette comes from springtime blooms of algae that live only in deep, persistent snowfields.

And yes, even a professional sometimes gets fooled.

"I was outside a penguin rookery in Antarctica, and I thought I was collecting this greenish-yellow algae," recalls the microbiologist now at the Massachusetts Department of Environmental Protection in Worcester. "I was saying, 'Yeah, yeah, this looks like the stuff.'" When he checked his treasures under a microscope, however, he diagnosed the obvious nonalgal origin. "It gets embarrassing," he admits.

Despite the yellow-snow raillery, Duval and his colleagues stay with their studies of snow algae because of the marvels of the chilly lifestyle.

Somehow the 350 species of snow algae thrive in the near-freezing, nutrient-poor, acidic, sun-blasted slush of melting snowfields around the world. The algae support a food web in the snow--a world of tiny, wormy, crawly beings as odd as Spielberg-movie creatures.

Algal life cycles combine the drama of salmon runs and the nightmare of icebound explorers. Snow-algae chemistry captivates biologists musing about life on other planets or prospecting for novelties on our own. These flashy algae are on their way to becoming glamour species in what Duval and like-minded specialists see as the dawning of a great era of snow ecology.

Plus, snow algae can be gorgeous. In high Western snowfields, they blush red in footstep-size patches and meters-long streaks that hikers call watermelon snow. In northern New England, they give salmon-orange sunset streaks to the last mounds of snow at the season's end.

Fie on snickering. Such wonders deserve awe.

"They're amazing," Duval sums up. He doesn't say that they're cool. That's another one that he's heard too often.

Snow algae aren't ice algae. Many of the ice species tolerate salt water and survive in solid ice packs at the poles. "They're completely different species," Duval says, sounding a little surprised that anyone would want to lump the groups together.

To find snow algae, look for serious snow, long lasting and several feet deep. William H. Thomas of Scripps Institution of Oceanography in La Jolla, Calif., goes to the high spots in Yosemite National Park and other snowfields at least 10,000 feet up in the Sierra Nevadas, the Cascades, and the Rocky Mountains. There, Thomas' particular passion, watermelon snow, tinted mostly by Chlamydomonas nivalis, ripens around July in the same places year after year.

"The red snow gets all the publicity," remarks Ronald W. Hoham of Colgate University in Hamilton, N.Y. "I find the green and orange more interesting."

The nonred species thrive where snow lingers longest in upstate New York and regions northward. Massachusetts' Berkshire Hills and Wachusett Mountain, New Hampshire's White Mountains, Vermont's Green Mountains, and Maine's Mount Katahdin all harbor colonies of snow algae, Hoham and Duval report in a paper to be published in RHODORA.

These species never develop the extensive red pigments that protect watermelon snow algae from brilliant sunlight. The green snow algae, mostly in the genus Chloromonas, typically stick to high-elevation, shady forests of fir and spruce. These algae generally bloom several inches below the snow surface.

Orange species tolerate a bit more light, and Duval and Hoham spotted their salmon-colored alga in the open snow of several New England ski resorts. They haven't found the species in wilderness areas yet, and they speculate that it spreads in part by hitchhiking on skis.

As Duval and Hoham pored over their map of Northeastern algae sightings, they decided that Chloromonas algae were more likely to bloom where 80 inches of snow falls in a winter than in spots with less-extreme weather. This insight sent Duval algae prospecting in West Virginia, but so far, no luck.

If New Englanders have never noticed the colorful local snow algae high in their woodlands, Hoham is understanding, if a bit narrowly focused. "Nobody wants to go hiking when it's miserable outside," he says. "They miss everything."

Snow algae are hardly an exclusively North American phenomenon--or a new one. Greek philosopher Aristotle reported red snow more than 2,000 years ago.

An 1818 British expedition exploring off the northwest coast of Greenland spotted crimson streaks on snowy cliffs and brought home red meltwater for analysis. "Our credulity is put to an extreme test upon this occasion, but we cannot learn that there is any reason to doubt the fact as stated," remarked the London Times.

Experts of that time decided that an iron deposit from a meteorite must have stained the explorers' snow. Only a year later, however, biologist F. Bauer described living cells in colored snow. The snow dwellers turned out to be bona fide single-celled, chloroplast-carrying members of the green algae division. Zingy pigments mask the underlying green.