Nutrient- and density-dependent effects in a producer-consumer model

A class of models of a nutrient-producer-consumer community is studied analytically and numerically. The analytical study focuses upon the role of total system nutrient and consumer density dependence in governing system behavior and especially, on the persistence and extinction of the population. The numerical study demonstrates that the relationship between consumer density dependence, total system nutrient, and dynamic system behavior can be complicated. Features of the model system include behavior determined solely by total system nutrient, behavior where the relationship between total system nutrient and density dependence governs system dynamics, and behavior where nutrient enrichment or deplation cannot modify ultimate system structure. A conclusion, robust for the model consumer density dependent formulation, indicates that, in the case of ample total nutrient, persistence of the community is independent of consumer density dependence.