EFFECTS OF ALGAL FOOD QUALITY ON FECUNDITY AND POPULATION-GROWTH RATES OF DAPHNIA

1. Food quality was at least as important as food quantity for both fe cundity and population growth responses of the cladoceran Daphnia puli caria fed the green alga Ankistrodesmus falcatus grown under N limitat ion, P limitation or non-limited condition. 2. The fecundity of D. pul icaria was reduced under conditions of low food quality (low N or low P) compared with that for animals fed control non-limited algae regard less of ration size. The reduced fecundity of D. pulicaria fed P-limit ed food could be partially alleviated by increasing the ration (hence, compensation), but such was not the case for animals fed N-limited fo od. 3. Population growth rates of D. pulicaria (r(max)) were significa ntly reduced under conditions of low-quality food for both N-limited a nd P-limited algae. Population growth rates were unaffected by ration size, indicating no compensation.