Limnologists have addressed themselves for more than fifty years to the distribution of phytoplankton and their biomass in relation to environmental factors in lakes of different trophy. Although this activity has resulted in an enormous and still rapidly growing literature, progress in understanding and prediction has been very slow. Only in recent years has it become possible to predict, albeit it very roughly, that the summer algal biomass to be expected in most temperate zone lakes is a function of the concentration or supply of primarily one nutrient-phosphorus. Few if any other predictions can be made about the composition and pattern of succession of the species or groups making up this biomass. Limnologists have by and large responded to this intractability in three ways. Many have continued to hope that pattern would emerge through continued attempts to couple changes in biomass, community composition, or production to physical-chemical lake parameters. Others have attempted to reduce the complexity of natural systems to manageable proportions by focusing on population changes of single species or specific classes of algae. Yet a third group has been trying to gain insight about algal dynamics by reducing the number of environmental interactions to manageable proportions in the laboratory. It is our thesis that these approaches or their combinations will be no more fruitful in the future than they have been in the past. What is needed is a much more holistic view of lake ecosystem functioning-one that better recognizes the limits to which