Thad Knight, age 12, of Winston Salem, North Carolina, for his question:
What exactly is pink snow?
Summer visitors to the western mountains often see pink snow on the lofty peaks, usually above the timberline. Its color is pale, watermelon pink and some say it even has a faint watermelon flavor. However, try to resist the temptation to taste it. Pink snow is a mighty strong laxative and facilities up there on the high slopes are hard to find. There are other reasons why this sort of snow sampling is inadvisable, even though most well boiled snow is fit to drink.
The color of snow, of course, is supposed to be white. And so it is. Its delicate flakes are embroidered from crystals of frozen water vapor and pockets of air. We see it as white because it reflects all the colored rays of light. However, sometimes it borrows a rosy blush from the setting sun. And snow banks are not alone in the world. All sorts of microscopic objects are tangled in its lacy network. The tinted snow seen on mountain slopes teems with single celled alga plants pink or yellow, orange or green. Some 15 to 20 species are classified in the genus Chlamydomondas. This term means having a shell, for their colors are spore cases.
Nowadays, of course, it is proper to view even the smallest organisms in their own system of ecology. The various colored snow algae share their miniature world with a multitude of living and non living things. These microscopic plants are amazingly com¬plex and what they lack in size they make up in numbers.
A thimbleful of delicately tinted snow may contain more than half a million colored algae and another half million bacteria, plus 100 or so protozoa and a quota of fungi. Some of these microbes may be unfriendly to humans, which explains why snow tasting is never advisable. Also trapped among the crowded snowflakes are molecules of nitrates, phosphates and other chemicals including dissolved oxygen and carbon dioxide. All these and other items participate in the microscopic ecology of the snowbank.
As usual, the life system begins with photosynthesis. The algae use solar radiation to manufacture oxygen and carbohydrates. They provide the basic food chain for the pro¬tozoa, the fungi and bacteria. All these various life activities break down chemicals and help to re cycle them through the system. Most of the unwanted wastes are returned to the environment by the fungi and decay bacteria. Actually, the pink snow algae are not very active in the busy system. In the spore stage, they are more or less dormant.
The hungry protozoa prefer more tender algae, in their active, green stages. In colored snowbanks, they may have to settle for a diet of bacteria.
Members of the Chlamydomondas genus are cryophiles, cold loving algae that live in snowbanks at 32 degrees Fahrenheit. Some can withstand more ultraviolet radiation than others. The pink type can survive full sunshine all day long. This is why most pink snow is high on exposed slopes. The orange and yellow types require the partial shade along the timberline. Green algae thrive farther down the slopes, well shaded by trees and shrubs.