Effect of Wide Temperature Fluctuation on the Blue-Green Algae of Bead Geyser, Yellowstone National Park

Optimal temperatures for photosynthesis and growth were determined for thermal blue-green algae inhabiting the drainway of a small geyser in Yellowstone National Park. The sparse algal mat was exposed to high temperatures only during the brief, highly periodic eruptions of the geyser. Optimal temperatures for the algae were higher than the mean environmental temperatures; as a consequence the algae experienced temperatures optimal for photosynthesis and growth only during a small fraction of the time. A heat-treatment experiment indicated that the algae of this mat were resistant to the high temperatures that occurred during eruption, whereas organisms having the same optimal temperatures but inhabiting a thermally constant environment were more heat sensitive. The thermally fluctuating environment appears to limit the extent of algal growth.