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Abstract

A model is proposed which consists of 24 sequential statements which describe step by step the seasonal events which occur in the phytoplankton and zooplankton of an idealized 'standard' lake, which is based upon the well-studied Lake Constance. These statements have been confronted with the real situations which exist in 24 different lakes, reservoirs and ponds which have been studied by the listed members of PEG. The confrontation of the model with empirical data reveals a major dichotomy in the successional pathways which occur in lakes with and without elevated levels of summer algal biomass. This dichotomy together with other significant features such as the extent of grazing pressure are compared with the traditional distinction of water bodies into trophic types (eutrophic, oligotrophic). Succession in plankton is understood to be predictable and directional although it may be disturbed by irregular physical events.