Nutrient enrichment (eutrophication) is a major theme in freshwater ecology. Some themes come and go, but the inevitable release of phosphorus and nitrogen that ac- companies human presence seems to ensure that eutrophication will not soon become an outmoded subject of study. Eutrophication raises issues that range from the pressingly practical problems of phosphorus removal to the very fundamental ecological questions surrounding biological community regulation by resource supply. Although it is possible to take a reductionist approach to some aspects of eutrophication, the study of eutro-...