RESOURCE COMPETITION AND SELECTIVE GRAZING OF PLANKTON IN A MULTISPECIES PELAGIC FOOD-WEB MODEL

An idealized mathematical, multispecies model of the pelagic foodweb w as used to explore the impact of resource competition, selective grazi ng, and species composition within each trophic level on the structure and functioning of a foodweb at a variety of light irradiance and nut rient levels. This concept is based on the general assumption that poo rly edible species are poor competitors. The concept demonstrates that with increasing eutrophication, specialists in competition will be re placed by generalists and subsequently by poorly edible primary produc ers. Controlling factors not only determine the growth rate of primary producers but also select predators according to their ability to uti lize the energy fixation of the system. Plankton community structure s eems to adapt in such a way that the energy fixation rate of the syste m is optimized at a given set of nutrients and light. Red tides, dense algal blooms in shallow lakes and the varying results of biomanipulat ion in shallow lakes, can be explained by the concept of selective gra zing. If this assumption is correct, the same ecosystem concept may be applicable for terrestrial ecosystems.