FROM ALGAL COMPETITION TO ANIMAL PRODUCTION - ENHANCED ECOLOGICAL EFFICIENCY OF BRACHIONUS-PLICATILIS WITH A MIXED DIET

The food-chain transmission of mineral nutrient effects to zooplankton production via phytoplankton competition was studied by two-stage exp eriments with a mixed phytoplankton assemblage from the Indian Ocean a nd the rotifer species Brachionus plicatilis. Phytoplankton species co mposition was steered by nutrient competition in the first stage of th e cultures. High atomic Si:N ratios (>1:1) in the medium resulted in d iatom dominance, and low ones resulted in flagellate dominance. Medium Si:N ratios (0.3-0.6:1) resulted in even mixtures of both types of al gae. The phytoplankton assemblage resulting from competition was used as food for Brachionus. An even mixture between diatoms and flagellate s in the food resulted in higher Brachionus production than one-sided food mixtures.