Differences in population growth of rotifers and cladocerans raised on algal diets supplemented with yeast

We studied the population growth of two rotifer (Brachionus calyciflorus and Brachionus rubens) and two cladoceran (Ceriodaphnia dubia and Moina macrocopa) species fed three diets (Chlorella vulgaris (Ch), Scenedesmus acutus (Sc) and yeast (Saccharomyces cerevisiae) (Y) in seven combinations (alone or mixed in equal proportions (on dry weight basis): Ch+Sc, Ch+Y, Sc+Y and Ch+Sc+Y). In general, the cladocerans were more adversely affected than the rotifers on the diet of yeast alone. The population growth curves of B. calyciflorus and B. rubens revealed that algal diets were superior to yeast. Regardless of diet, B. rubens had a longer lag phase and delayed peak density compared to B. calyciflorus. Both M. macrocopa and C. dubia had higher peak abundances when fed mixed algae than on either alga offered separately. B. rubens, C. dubia and M. macrocopa reached significantly lower maximal densities on diets containing yeast, S. acutus or both. When the data on the eggs/female (egg ratio) were plotted as function of population density, we found an inverse relation, which was curvilinear for B. calyciflorus and linear for B. rubens. In general, we found that yeast could effectively supplement algal diets in all the test species, thereby reducing costs in large scale production of zooplankton.