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UBC Theses and Dissertations

Culture of the freshwater cladoceran, Daphnia Pulex F. utilizing Scenedesmus obliquus grown in dairy waste medium Castillo, Nelson M.


Scenedesmus obliquus was grown in batch cultures at varying concentrations of digested dairy medium ranging from 200 to 2,000 ug-at N ⁻¹. Higher growth rates were observed at low N-concentrations while higher cell yields were observed at high N-concentrations. Aeration enhanced both algal growth rates and biomass yields. Results show an advantage in adjusting the nitrogen to phosphorus atomic ratio of the medium. More biomass was produced in cultures with higher N:P ratios. The algal biomass produced was used as food for the freshwater cladoceran, Daphnia pulex F. Three feeding levels were used: 50,000, 100,000 and 150,000 cells-ml⁻¹ . However, no significant differences were observed in both Daphnia biomass yields and biomass conversion efficiencies. The tendency of Scenedesmus cells to settle down in the bottom and cling to the sides of the tank presented a major problem in the study. Intensive feeding did not increase the biomass production of Daphnia, although larger-sized adults with larger brood sizes were produced. Animals in culture reached a density of 1.24 animals-ml⁻¹Aand obtained conversion efficiencies as high as 40-50%.

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