Red Snow, Green Snow - snow algae

Science News, May 20, 2000 by Susan Milius

To withstand the intense sun burning down on snowfields, the algae display other chemical oddities. A red snow alga, for example, develops 12 carotenoid pigments. Harvey Marchant of the Australian Antarctic Division in Tasmania published electron micrographs of algae from the Snowy Mountains of Australia in 1982. The pictures and chemical analysis revealed carotenoids spread around the outer zone of the cell as if shielding the chlorophyll from sun overload.

The carotenoids protect against ultraviolet light, Thomas and Duval argued in 1995. Red algae in natural sunlight have 75 percent as much photosynthetic capacity as do those protected from the portion of the sun's ultraviolet spectrum known as UV-B. Green snow algae, which lack these protective carotenoids, suffer much more from full sunlight. Those without artificial UV protection show only 15 percent of the photosynthetic power of protected cells. In nature, the green species shield themselves with a layer of snow.

Duval, Thomas, and Kalidas Shetty of the University of Massachusetts in Amherst have just published the first evidence for another potential algal strategy for protection against ultraviolet light. After 5 days of exposure to the radiation called UV-A, the classic watermelon snow alga of California pumped up the amount of its phenolic components by 5 to 12 percent. "These are the compounds that are in red wine," Duval explains. They've attracted interest as antioxidants, cellular police that capture potentially damaging singlet oxygen and free radicals. Likewise, UV-C juiced up the phenolic content, the research team reported in the JOURNAL OF APPLIED PHYCOLOGY late last year.

Geneticist James Leebens-Mack, also at Colgate, has been examining snow algae. This month, he and Tomas Bonome are presenting their comparisons of genetic material from several species. The pattern of similarities, some strong and some weak, that they have described suggests that the snowy lifestyle evolved in algae at least twice, says Hoham.

He and three coeditors are putting finishing touches on a book with an unusually multidisciplinary approach to the topic. Cambridge University Press plans to publish Snow Ecology in August. With a sort of remembering-Woodstock glow, Hoham describes his first discipline-mixing experience at a snow scientists' gathering in 1993. Sessions overran their scheduled times by at least 3 hours each night as snow chemists encountered microbiologists who'd never known what paleoecologists thought of snow physics.

"We didn't want to stop because we'd never heard each others' stories," Hoham reminisces.

Duval laments, "The whole topic of snow ecology has been overlooked." Modern genetics could change that, he notes. He expects its tools to energize the field, untangling the chemistry and giving rise to new ways to use the discoveries.

Maybe then, at last, he'll get through whole meetings where no one smirks about yellow snow.