• Alga;
  • Bioassay organism;
  • Population growth;
  • Waste;
  • Water quality


The population growth of the freshwater chlorophyte, Scenedesmus acutus and the cladoceran Moina macrocopa cultured in the laboratory and in microcosms of a wastewater treatment plant was studied. S. acutus was cultured in a defined algal medium and mixed with wastewater. On diets of S. acutus cultured using Bold medium or a mixture with wastewater, the peak densities of M. macrocopa were 6–7 ind. mL−1, while on a diet of algae cultured on wastewater alone the cladoceran density fluctuated around 2 ind. mL−1. Population growth rates of M. macrocopa, which ranged from 0.3 to 0.4 d−1, were significantly lower on alga cultured in wastewater alone. The body size structure of M. macrocopa was larger on algae cultured in Bold medium than in wastewater. Peak densities of M. macrocopa were around 700 ind. L−1 when the organic matter in the containers was supplemented with algae but it reached lower densities (400 ind. L−1) when cultured on the organic matter in wastewater alone. Our study indicates that the nutrients in the final stages of wastewater treatment can support the growth of both phytoplankton and zooplankton.