“This time of year in the mountains . . . there are still patches of snow that haven’t completely melted off. On some of these patches . . .you sometimes see a red (or pink) algae (or mold) growing. Everyone I’ve talked to says you should never eat it, but no one seems to know exactly what it is.”
There are fungi, mold and some insects that have adapted the extreme cold on mountain tops. But what you saw was probably algae. There are more than 350 different kinds of algae that live in snow. The best known is chlamydomonas nivalis which appears to turn snow red.
These are actually green algae. That is, when new cells form they’re green, but they quickly turn red to protect themselves from bright light in a snowy environment. During the dark and cold of winter, these algae are dormant. In spring and early summer, they reproduce very quickly — and can make large patches of snow appear pink or red.
And you’d be right to leave them alone. Many blue-green algae can also be snow algae — and some are highly toxic.
The conditions become right for the growth of these algae when the snow begins to melt. This is because the thin layer of water carries nutrients to the algae and permits them to swim and reproduce. Often this happens only two or three days out of the year. Too much water, for some reason, is not ideal.
Dr. Mitman says that one organization he is in discourages people from eating the blue-green algae sold in health food stores. They claim it is possible for unwanted (toxic) strains to mix in with the desired ones.
A passage in the 1997 encyclopedia Britanica talked of red, brown, green, yellow and black snow, all caused by different types of algae. Dr. Mitman hadn’t heard of many of them, but commented that algae have accessory pigments which can make them turn just about any color. He noted that other plants do too. Carrots, for example, would be green if you grew them in the light. Red maple leaves are actually green underneath.