Content and turnover rates of phosphorus in Daphnia pulex: Effect of food quality

The content of phosphorus in individual Daphnia pulex and the rates at which the element turns over are functions of the P contents of algal cells fed to the zooplankton. Chlamydomonas and Ankistrodesmus were grown in semi-continuous cultures containing 2 µM and 10 µM PO₄ to produce differences in cellular P of the algae. Animals reared on the cultures high in P contained 60 percent more P than did animals of equal size that were fed low P cells. Daphnia with high body contents of P turned over that P faster than did the animals fed low P algae. Measured turnover rates imply that large differences exists between rates of gross P assimilation and P excretion for animals fed high and low P sources.