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Snow; Ice; Light


During several months of each year, soil and bodies of water in high latitudes are separated from the enveloping atmosphere by a layer of snow and ice of varying thickness. The effects of this insulating layer are not well understood, having received relatively a rather surprisingly small amount of attention by ecologists. It is known that snow cover influences the heat exchange between the surface of the earth and the air. Ice is thought to interfere with gas exchange between water and air and with aeration by wave action to the extent that epidemic losses of fish life occur through suffocation. It has been suggested recently that the problem may be, at least in part, a light relation. Some algae are known to carry on photosynthetic activity at low temperatures. By excluding light, the snow and ice cover may prevent the evolution of an oxygen supply essential to fishes. The penetration of light through snow and ice cover is also of possible importance to grass crops and other low-growing plants that remain wintergreen. It is known that only a very small amount of light (in some cases less than one per cent of the amount available in the open) is needed for the formation and retention of chlorophyll, although the problem is a complex one in which temperature is an important factor. The study here reported is limited to an attempt to find out how much total measurable light penetrates ice and snow cover, only incidental observations of its ecological effects having been made.

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