Temperature influence on bacterial populations in three aquatic systems

Effects of temperature changes on bacterial populations in three aquatic systems were studied in the Thermal Effects Laboratory of the USAEC's Savannah River Laboratory. At monthly intervals for 12 months, total plate counts and diversity of heterotrophic, mesophilic bacteria were determined from a natural stream, two artificial streams, and two outdoor ponds. Water for artificial systems was drawn from the natural stream. Effects of changes in ambient temperature were analyzed in natural and artificial streams and in an unheated pond. A second pond was heated above natural stream temperature. Temperature elevation resulted in increased total plate counts in each system. Bacterial diversity increased in all systems during the initial 3–4°C increase in temperature. However, a reduction in diversity occurred when temperature was maintained 4–10°C above the initial ambient temperature. Changes were observed in both nutritional types and genera.