Dynamics of coupled populations in an open, three-trophic-level system

The investigated stream system, which consists of three-coupled populations (benthic algae, grazers, and predators), is modeled as a fixed region of space(e.g., stream reach) and over a limited period of time.  The time scale allows for growth of primary producers (algae), but not for reproduction of grazers and predators.  The system is open, allowing immigrations and emmigrations.  Immigration at all trophic levels is assumed to be governed by external factors and to be independent of population densities within the system. In contrast, emigration rates of consumers may depend on the densities of their resources and/or predators, and feeding rates of consumers depend on the densities of their resources. Growth of primary producers depends on their own density.