ENVIRONMENTAL FORCING OF SIMPLE PLANKTON MODELS

This paper examines the phenomenon of algal blooms in phytoplankton po pulations in the context of a simple spatially homogeneous model. The effects of a changing environment are represented by time dependence i n the model's parameters. It is argued that the interaction of grazing pressure and nutrient limitation gives rise to excitability in the dy namics of the model. This property allows the use of asymptotic analys is to derive a connection between the nature of the environmental forc ing and the production of a bloom. Numerical experiments demonstrate t he accuracy of this analysis and also show hew, and under what conditi ons, its effectiveness starts to break down. Some of the biological im plications of these results are discussed.