Life at High Temperatures

by Thomas D. Brock

The Firehole River

© 1994 Yellowstone Association for Natural Science, History & Education, Inc. Yellowstone National Park, Wyoming 82190.

The Firehole River has been a main attraction of the Yellowstone area since its first discovery by explorers. It is famous world-wide as an outstanding trout stream, but it is a trout stream of unusual character, since it is also a river subject to great thermal "pollution". Above the Upper Geyser Basin the Firehole is a cold mountain stream, but by the time it reaches Firehole Falls below the Lower Geyser Basin its temperature has been raised almost 15 degrees C (27 degrees F) as a result of the massive thermal inputs it receives. The single effluent from Excelsior Geyser Crater in the Midway Basin (shown above) increases the temperature of the whole river by 3-4 degrees C (5-7 degrees F).

Addition of thermal water results in marked biological effects. Algae, bacteria, and invertebrates all grow faster and to higher numbers in the heated portions of the river. Although it is commonly assumed that trout cannot live and reproduce in warm waters, they are in fact well established in the Firehole, even in the warmest parts.
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