The sensitivity of life-table parameters of two cladoceran zooplankton to slight, natural variations in temperature was determined during the onset of a midsummer blue-green algal bloom in a large turbid reservoir (Lake Texoma, Oklahoma, Texas). Prior to the onset of blue-green algae, cohorts of Ceriodaphnia lacustris incubated at ambient epilimnion temperatures (27–30 °C) had higher individual somatic and population growth rates, an earlier age at first reproduction, and shorter life-spans than cohorts incubated at a constant 25 °C. As blue-green algae became abundant, Ceriodaphnia growth rates were reduced more dramatically at ambient temperatures than at 25 °C, suggesting that a temperature–resource interaction was important to determination of somatic growth rate, age of first reproduction, and population growth rate. Ceriodaphnia populations declined in Lake Texoma as blue-green algae became abundant. Diaphanosoma leuchtenbergianum, which was abundant throughout the period of blue-green algal dominance, did not show the temperature–resource interaction found for Ceriodaphnia. Temperature–resource interactions have been hypothesized to determine seasonal change in zooplankton community structure; this study provides experimental evidence of demographic consequences in natural populations of one kind of common temperature–resource interaction.
The influence of daylength, light intensity and temperature on the growth rates of planktonic blue-green algae
