Effects of Thermal Additions from the Yellowstone Geyser Basins on the Bacteriology of the Firehole River

Abstract

A series of stations was established on the Firehole River where it flows through the main geyser basins of Yellowstone Park, and temperature, pH, alkalinity, conductivity, and phosphate were measured. The temperature of the water gradually increased as it flowed through the thermal area, at its warmest averaging about 16°C higher than in the cool area (10° to 26°C). Alkalinity, conductivity, pH, and phosphate also increased markedly. The growth rates of periphtic bacteria measured in situ on glass slides were virtually identical at different stations despite the wide differences in temperature. The effect of temperature on the incorporation of 14C—glucose by benthic bacteria populations at the different stations demonstrated that the temperature optimum for this process increased in parallel with the temperature of the habitat. It is thus concluded that the bacteria are near—optimally adapted to the temperature of their habitat and that despite wide differences in temperature the rate of bacterial activity is the same. In another study, samples of water were placed on agar media and incubated at temperatures of 25°, 55°, and 70°C to obtain estimates of the number of bacteria able to grow at these temperatures. The thermophilic organisms developing at 55°C were primarily Bacillus stearothermophilus at those at 70°C primarily Thermus aquaticus. Thermophiles were not present in water which had not received thermal additions, but both kinds of thermophiles were found in the warm water, and numbers increased progressively as more thermal water entered. In the recovery zone downstream from the thermally region, the numbers of thermophilic bacteria decreased markedly. The possible value of these thermophilic bacteria as indicators of thermal pollutions is discussed. It is suggested that the Firehole River is an excellent model for long—term studies on the ecological consequences of thermal pollution.