Growth of dominant zooplankton species feeding on plankton microflora in Lake Shira

Batch cultures and continuous flow cultures were used to study the growth rates of zooplankton species from Shira lake, the rotifer Brachionus plicatilis Muller and calanoid copepod Arctodiaptomus salinus Daday, which were fed on phytoplankton and bacterioplankton from the lake. Analyses of the birth and survival rates were used to demonstrate that the lake phytoplankton, consisting mostly of cyanobacteria and diatomaceous algae, is inadequotes for optimal realisation of the reproductive potential of B. plicatilis when compared with the bacterial diet. The study revealed that the kinetic growth characteristics of the two zooplankters were similar: B. plicatilis r _max, 0.120 d^–1; S ₀, 0.253; and K _s, 0.114 mg dry mass l^–1; and for A. salinus r _max, 0.129 d^–1; S ₀, 0.240; and K _s, 0.171 mg dry mass l^–1. Fluctuations in natural food concentration reduced the growth rate of both species. Even though the threshold concentration of food for B. plicatilis and A. salinus were quite similar, the copepods were less sensitive to food limitation.