Effects of thermal effluents on the population dynamics of Physa gyrina Say (Mollusca: Gastropoda) at Lake Wabamun, Alberta

Abstract

Effects of thermal effluents on the population dynamics of Physa gyrina Say (Gastropoda: Pulmonata) were studied at Lake Wabamun, Alberta, from May 1971 to August 1973. Thermal effluent increased the rate of development of eggs and the growth of P. gyrina, and allowed continuous reproductive activity throughout the year. These changes, and the increased period of growth of aquatic macrophytes, resulted in increased population densities of P. gyrina in the heated area during summer. Temperatures below 10 °C or small amounts of vegetation appear to limit the population of P. gyrina in winter.