Effects of Temperature and Salinity on the Survival and Egg Production of Gladioferens pectinatus Brady (Copepodas: Calanoida)

The calanoid copepod Gladioferens pectinatus Brady occurs in Lake Waihola, New Zealand, a shallow, tidally-influenced lake. This lake experiences daily and seasonal fluctuations in salinity, and seasonal changes in temperature. To determine the potential contributions of salinity and temperature to observed seasonal population fluctuations, we tested the survival and egg production of G. pectinatus at two temperatures (10 C and 20 C) and in a range of ‘ salinities ’ (20 to 2700 mg l 1 Cl). Adult survival was highest in 1000 mg l 1 Cl at 10 C, when 50% still remained alive after 23 d. Increases in salinity and temperature decreased the survival time to less than 10 d. The salinities tolerated were well below the maximum of 2500 mg l 1 Cl recorded in the lake. There was no difference in adult survival between males and females. Eggs were produced in salinities of up to 600 mg l 1 Cl. Only in 20 mg l 1 Cl did an increase in temperature reduce clutch retention time, and increase the rate of egg production. The rate of increase in salinity did not affect copepod survival, but acclimation at an intermediate salinity increased survival at 10 C. Our results suggest that high temperatures and salinities in summer may lower the fitness of this population of G. pectinatus.