"Even if net uptake rates are low, the amount of total global land area involved could result a significant impact," biophysical ecologist William Smith of Wake Forest University in Winston-Salem, N.C., told United Press International.
Anywhere snow lingers past winter, pink snow can be found. The snow even has a fresh watermelon scent.
"In the U.S., it's known as 'watermelon snow,' while Scandinavians call it 'blood snow,'" said Tom Vogelmann, a physiologist with the University of Vermont.
The red tint finds its root in an unusual kind of microscopic spherical freshwater algae -- each up to four times as wide as a human blood cell -- that blooms with the coming of summer. "They really are bizarre," Vogelmann said. "It's very hostile where they live. It's near the freezing point most of the time, and most of the time they're bathed in very high ultraviolet radiation, and somehow this creature not only grows but thrives."
Like plants, the algae photosynthesize -- they manufacturing sugars from carbon dioxide and water in the presence of sunlight. Carbon dioxide is a greenhouse gas that traps solar heat and plants help prevent global warming by absorbing it. The investigators wondered if the snow algae also had a part in guzzling CO2.
Over the course of four summers, researchers measured how much carbon dioxide the algae soaked up in response to variable sunlight levels by placing a transparent plastic box fitted with gas sensors over patches of algae in the Snowy Range of the U.S. Rocky Mountains.
"The routine was we'd head out 4 o'clock in the morning. It'd be an hour up to the field site, and then you go up a mile carrying 80 pounds of instruments in the bag at 11,000 feet up," Vogelmann said. "There was one year we remembered as 'the summer of the rain,' where there was a thunderstorm every afternoon, and when you looked everywhere else, there's nothing, it was only over our field site ... you're covering up the instruments, which are sensitive, and the wind is blowing, lightning flashing, and you're hoping you won't have a boulder on your hat."
As reported in the online Jan. 6 Proceedings of the National Academy of Sciences, the investigators found the snow microbes absorbed relatively high levels of CO2 from both the soil and air in bright light.
"These snow fields were surprisingly productive," Vogelmann said.
However, Smith said he had "serious concerns" about the accuracy of the carbon dioxide level changes measured. Given the limited resolution of the instruments used, the numbers and statistical analysis "deserves more discussion and attention," he said.
Ecologist Chris Field of the Carnegie Institution in Palo Alto, Calif., also doubted whether the snow algae served as significant carbon dioxide sponges on a global level.
"I think the paper doesn't really address how common or widespread the process is," Field said. "They talk about the locations of pink snow in a lot of locations, and corroborating it with satellite data, and that's a good idea. But at this point we know there's some locations where there's a lot of it, and some locations where there's not that much."
Phycologist Ron Hoham of Colgate University in Hamilton, N.Y., said snow algae might very well serve as an important carbon dioxide "sink," but added he found it disappointing the researchers "do not even mention the extensive green snow ecosystems that are so prevalent in the high elevation and high latitude forests across North America, Europe and Asia -- most snow algae is green, not red."
Much remains unknown about snow algae. For instance, scientists do not know where they come from -- whether they wriggle up from the soil underneath the snow, or if they blow in on the strong alpine winds.
Vogelmann said understanding the mechanisms underlying how these microbes thrive such cold and radiation could help genetically improve crops to help them grow in hostile conditions.
Also, regarding life on other planets, NASA scientists and others have noted "it's really quite of a bit of value to look at lifeforms that grow and thrive in some of the more hostile conditions on Earth," Vogelmann said.
(Reported by Charles Choi, UPI Science News, in New York)