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157-21(5-20-00) Red Snow, Green Snow: It's Truly Spring When Those May 20, 2000 BROWSE BROWSE TABLE OF BY YEAR 2000 ISSUES CONTENTS 2000 Vol. 157 No. 21 p. 328 Red Snow, Green Snow It’s truly spring when those last white drifts go technicolor By SUSAN MILIUS 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 dis- cover 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 trea- sures 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. Duval Algal life cycles combine the drama of salmon runs and No, it’s not a murder scene. A the nightmare of icebound explorers. Snow-algae chemistry bloom of the alga Chlamydomonas captivates biologists musing about life on other planets or nivalis reddens the snow beside a hip-high evergreen in the Sierra prospecting for novelties on our own. These flashy algae are Nevadas of California. 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 sur- prised 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 Copyright ©2000 by Science Service May 20, 2000 BROWSE BROWSE TABLE OF BY YEAR 2000 ISSUES CONTENTS 2000 Vol. 157 No. 21 p. 328 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 north- ward. Massachusetts’ Berkshire Hills and Wachusett Mountain, New Hampshire’s White Mountains, Vermont’s Green Mountains, and Maine’s Mount Katahdin all harbor colonies of Duval snow algae, Hoham and Duval report in a paper to It takes an expert to tell, but this yellow stain be published in RHODORA. revealed by digging in the snow comes from a These species never develop the extensive red bloom of a Chloromonas alga in Yosemite pigments that protect watermelon snow algae from National Park. More delicate than its red brilliant sunlight. The green snow algae, mostly in relatives, it has not risen all the way to the sun- blasted surface of the snow. the genus Chloromonas, typically stick to high-ele- vation, 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-col- ored 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 mis- erable 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 mem- bers of the green algae division. Zingy pigments mask the underlying green. The greatest sense of the worldwide scope of snow algae came from a Hungarian botanist, Erzsébet Kol, who started publishing scientific articles on the subject in the mid 1920s. For the next 50 years, she described snow algae sent to her from Antarctica, New Guinea, and other far-flung snow fields and accumulated during her own wide-ranging travels. She collected spec- imens from Transylvania to Alaska and even managed to get into isolationist Albania to describe its algae in 1958. Copyright ©2000 by Science Service May 20, 2000 BROWSE BROWSE TABLE OF BY YEAR 2000 ISSUES CONTENTS 2000 Vol. 157 No. 21 p. 328 With all these records, Duval wondered a few years ago why Africa remained the only continent where no one had reported snow algae. In 1998, he and Edilma Duval set off on an algae-prospecting jaunt on Mount Neltner in Morocco. They brought an ice chest of Moroccan snow back to a laboratory in Spain. The next year, they and Hoham, their taxonomic collaborator, published the first report of snow algae in Africa. Scientifically surveying for algae looks a bit like poking around in the snow. “People will come up to me and ask, ‘Did you drop something?’” Brian Duval says. The colors blossoming on snowbank surfaces in springtime are just the tip of the life cycle for snow Duval algae. The red of watermelon snow comes from pig- What seems to be an as yet unnamed species ments in algal cysts, resting cells protected by sturdy of Chloromonas gives an orange tint to the coats. Hoham has received healthy cyst samples last snow patches on Mount Washington in shipped at –70°C, a temperature that destroyed active July. algal cells. Using radioactive carbon, Thomas and Duval have shown that cysts photosynthesize, but otherwise they just wait for the next sea- son’s action. As snow vanishes in summer, the cysts settle onto the ground. “The red ones look like a crust of dried blood,” Duval says. Summer passes. Snow falls again. The cysts essentially just lie there as snow piles up on top of them week after week. When the snow starts melting in the high-altitude spring, the cysts burst, releasing single cells, each with two whiplike tails. They swim upward, bucking the current of draining meltwater. “It’s a race against time,” explains Hoham. Like salmon on their final swim, the algal cells have to gain the upper reaches of their water world to reproduce. The cells, only 10 to 15 micrometers across, fight their way through several feet of snow in meltwater that hasn’t reached even 1°C. Because their snowy world is disappearing, the swimmers can’t afford to dally. Although the pH of most springtime snow hovers around 5, during the first flush of melt- ing, it can sink to 3.5, about the same acidity as peat bogs, Hoham reports. The bogs’ well- known ability to preserve corpses stems from the death of most microbes in such an environ- ment, yet snow algae swim through similar punishment. When some of the swimmers near the surface, they mate and form the protective cysts. Others don’t mate when they reach the top, but they still form cysts. Hoham is trying to sort out why some algae he studies seem not to have sex at all, but others even in the same popu- lation reproduce sexually. This month at the Eastern Snow Conference in Syracuse, N.Y., he and his students are scheduled to present results from their ongoing study of factors influencing algal mating. The researchers have established, for instance, that in the lab, New York Chloromonas mates most readily in a mild, blue glow, which resembles sunlight filtering through an evergreen forest and a layer of snow.
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