EFFECTS OF FOOD AND WATER-QUALITY ON CULTURING OF CERIODAPHNIA-DUBIA

The U.S. Environmental Protection Agency (EPA) has developed a 7-d test to evaluate effluent effects on Ceriodaphnia dubia survival and reproduction. Several foods have been used to culture and test Ceriodaphnia dubia in both laboratory waters and surface waters with variable results. This study's objective was to evaluate effects of eight diets on survival and reproduction of Ceriodaphnia dubia in hard reconstituted water (HRW); HRW was used alone or supplemented with bacteria or selenium to determine whether their addition would improve survival and reproduction. Diets consisted of yeast, trout food (TF), yeast/trout food/Cerophyl(R) (YTC), Selenastrum capricornutum, Ankistrodesmus convolutus, Chlamydomonas reinhardii, Selenastrum capricornutum plus TF, and Selenastrum capricornutum plus YTC. Screening tests in HRW with each diet (at several levels) were first used to rank diets; diets with high survival (greater-than-or-equal-to 80% at 14 d) and reproduction (greater-than-or-equal-to 3 young per female per reproductive day) were further evaluated in multigeneration feeding tests. Finally, diets yielding high survival and reproduction in HRW were evaluated in surface and well water to verify adequacy in waters of differing composition and quality. Yeast, trout food, YTC, Selenastrum capricornutum, Ankistrodesmus convolutus, or Chlamydomonas reinhardii used alone were unacceptable for long-term culturing in HRW under test conditions used in this project. Success of the EPA's recommended food, YTC, was dependent on water, with worst results in HRW. The addition of selenium and bacteria to the HRW did not consistently improve either survival or reproduction of Ceriodaphnia dubia in the diet tests. Some of the diet test results were confounded by the use of batches of HRW that periodically contained some unidentified components that were toxic to Ceriodaphnia dubia. Both Selenastrum capricornutum plus TF and Selenastrum capricornutum plus YTC were acceptable for culturing with high survival and reproduction.