This book tells a story of a large lake affected by agricultural and urban activities that have led to severe eutrophication problems with nuisance blue-green algal blooms. Although it is a case study of Lake Ringsjön (southern Sweden), the background, problems and measures are applicable to many lakes throughout the world. From a limnological point of view, the Lake Ringsjön story began more than 100 years ago, and during the last 20 years the sampling program has been intense, providing a unique data set on how a lake responds to human activities. However, the Lake Ringsjön story is not only a case study, but also a historical record of the development of ecological theory and its application. Hence, the lake has been subject both to an extensive nutrient reduction programme and a biomanipulation by means of fish reduction. Here we aim at combining the unique limnological data set with the eutrophication process, the nutrient reduction programme and the biomanipulation in order to apply our empirical knowledge to future lake management measures.