These proceedings of a workshop of the International Association for Phytoplankton Taxonomy and Ecology are directed specifically at the relationship between phytoplankton ecology and the trophic status of water bodies. Contributions address the fact that distinctive assemblages of phytoplankton species are closely associated with particular categories of water bodies. Particular attention is paid to how communities are assembled and to the ways in which environmental constraints filter the successful species. Overview articles are included. The book will be a valuable source of information to limnologists, algologists, and the technical staff of all water suppliers.