Nutritional quality of seston for the freshwater herbivore Daphnia galeatax hyalina: biochemical versus mineral limitations

The quality of natural seston as food for zooplankters can be highly variab le. Thus far, experimental evidence on the factors affecting food quality u nder natural conditions is scarce. Hence, in this study, we set out to inve stigate how Daphnia galeata x hyalina responded to qualitative variation in natural seston. This was done in laboratory experiments where we supplemen t natural seston from a mesotrophic lake with dissolved phosphorus and emul sions of highly unsaturated "essential" fatty acids. The growth rate of juv eniles increased upon the supply of both phosphorus and fatty acids. These results suggest that these phosphorus and highly unsaturated fatty acids ar e substitutable and thus challenge our existing interpretation/understandin g of how herbivore growth is "limited".