Diane Davis, age 14, of Niles, Ohio, for her question:
What causes red snow?
This topic takes us down to the microscopic world of miniature single celled plants. The particular alga that tinges a snowy slope with petal pink has a varied and interesting life story. But its most outstanding talent enables it to thrive on glacial icefields of perpetual frost.
Sometimes a rosy blush is seen on an alpine peak at dawn and sunset. It may be caused by the sloping red rays of sunlight. But if the delicate red glow continues through¬out the day, the explanation is found on the surface of the icy snow. The snowy moisture is populated with tiny teeming algae. We need a .strong microscope to study the fascinating phases of their busy lives. .
Some 18,000 assorted algae have been named and classified and thousands more are waiting to be identified. Each species has its own way of life, but basic similarities enable us to sort them into groups. The differences between the groups are so great that modern biologists have sorted them into eight or nine phyla. A less precise grouping arran¬ges them in four or five groups based on color. There is a blue green and a grass green group, a red and a brown group and possibly a golden alga group.
When seen in swarming billions, the various algae add their own tinges to the sea and soil, to ponds and even ice caps. The trouble with this simplified color classification is that many species change their colors with different phases of their life cycles. You would expect our rosy tinted snow dweller to belong in the red algae group. But it does not. It belongs with the grass green algae. The single celled organism has a quota of the chlorophyll pigments that add greens to the higher plants. The tiny cell also has a quota of another pigment that may mask the basic green with yellow or red.
The scientific name of our microscopic artist is chlamydomonas, a word coined from an older word for cloak. At various phases cf its life it takes the shape of a ball, an egg, and a peanut. We may find it resting quietly on the snow or busily moving from place to place. It travels around by waving two tiny tails called flagella. During its travel¬ing phase it is egg shaped with the flagella at the narrow, forward end of the egg. At this period, the red snow alga may be red. But as it gets ready to multiply it changes to green.
Soon the flagella are withdrawn and the chlamydomonas rests as a round, yellowish ball. The brood of offspring forming inside the parent cell may pull it into a peanut or an oval shape. The newly hatched cells may be green and each young alga moves off waving a pair of flagella. Later, they may lose their waving arms and rest as round red balls.
Swarming multitudes of the red snow alga thrive on the ice surfaces of the Arctic and Alpine snow fields. The factors that trigger the changing phases of their existence are not fully understood. Light rays may play a part, so may the acid or alkaline chemical content of the snows. When the triggering factors occur, zillions of tiny snow algae go through their paces like a well drilled army. As they do so, they tinge the glistening white snow with green or yellow or blushing red.