The nutritional quality of P-limited algae for Daphnia

This paper details results of experiments intended to clarify the relative effects of mineral versus biochemical limitations of algae on the food quality for herbivorous zooplankton. Phosphorus limited algae (Scenedesmus) were fed to Daphnia magna and the somatic growth rates of the animals were measured. The animals showed an increase in growth rate when phosphorus (P) was added to P-limited algae, especially when the animals were older. The addition of highly unsaturated fatty acids only resulted in an increase in growth rates when the algae had a C:P ratio of less then 300. The main conclusion of this work is that both mineral and biochemical limitations of their food play a role in the growth and population dynamics of zooplankters, but that mineral requirements need to be met first.