Modeling the Lake Mendota ecosystem: Synthesisand evaluation of progress

The models presented in the three preceding chapters were planned as elements of an integrated ecosystem approach from phosphorus to fishes. The modeling problem was broken into three parts in order to maximize our rate of progress and make best use of the people involved. The modules—piscivory, planktivory, and herbivory-algae-nutrients—have fundamentally different time scales yet strong vertical interactions (Figure 22.1). Within a given nutrient and weather regime, differences in return time cause the upper modules to act as constraints on lower ones (O’Neill et al. 1986). Piscivore dynamics have return times of years (Post and Rudstam, Ch. 19). Stock and harvest policies as well as resource levels must be considered in modeling piscivory. Planktivory by fishes has return times of years, while that by the zooplankter Leptodora has return times of weeks (Luecke el at., Ch. 20). Herbivory, algal growth, and nutrient fluxes have rapid dynamics and short return times of a few days (Vanni et al., Ch. 21).