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NatureSpeak Articles

Red snow algae

First blush of spring in the high alpine.

If there is an unoccupied niche anywhere on this fecund planet of ours something is certain to move in. No matter how hostile, how tiny, or how unsavoury the space may seem, if it can support life some form of life will claim it, adapt, and call it home. But in the search for a room of one’s own the creatures that inhabit the perpetual cold of glacier ice are among the most resourceful. And of these the red snow algae that appears each spring, as if by magic, is one of the strangest.

In 1818 Captain John Ross sent a landing party ashore to collect samples of crimson snow off the coast of Greenland. The results of analysis were reported in the London Times of that year: The liquor, or dissolved snow, is of so dark a red as to resemble red port wine. It is stated that the liquor deposits a sediment; and that the question is not answered, whether that sediment is of an animal or vegetable nature. It was finally concluded, wrongly, that the colouration was caused by meteoric iron deposits. The true cause of the phenomenon was not discovered until the end of the nineteenth century.

The pigment of red snow is now known to be algal cells, but it still elicits questions from curious spring visitors to Whistler. As a Mountain Host I have often explained to squeamish tourists that, no it is not blood from ski accidents, nor is it something Intrawest spreads on the snow to prolong the ski season.

Red snow algae is a unicellular, photosynthetic plant which, in the spring, accumulates on the surface and within the upper 20 to 25 cm of old snow. It is concentrated in shallow depressions where its dark colour absorbs solar heat and further deepens the growing sun cups. Under a microscope each spherical cell is seen to be about 4 times the size of a human red blood cell. Their thick walls and bright red carotenoid pigment help protect delicate cells from intense ultraviolet radiation.

If we pick up the life cycle of Chlamydomonas nivalis in mid-winter we would find the dormant red cells (aplanospores) of the preceding summers bloom buried under the new snowpack. In the spring, meltwater and dissolved nutrients reach the resting aplanospores and stimulate germination. At that point the resting cells release smaller green swimming cells. Each of these is equipped with two whip-like flagella which propel them, like twin-engined sperm, up through the snowpack to the surface. Once exposed to sunlight the swimming cells lose their flagella and form the thick-walled red cells which, in their trillions, give the spring snow its rosy blush. And the cycle begins anew.

Red snow algae are the primary producers at the beginning of a unique food chain. In making a niche for themselves they have created a niche for tiny herbivores that feed on their spores and for glacier-dwelling carnivores that feed on the herbivores. But that is a subject for another column.

Written by: Jack Souther

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