This volume provides the first comprehensive overview of the enormous ecological diversity of Baltic coastal ecosystems. A short introduction into the Baltic Sea as a reference ecosystem is followed by detailed descriptions of the characteristics of coastal ecosystems. Ecological case studies from the following four regions illustrate the different reactions of these ecosystems to natural and anthropogenic influences: Southern Baltic coast: Fjörden, Boddens, Lagoons and nearshore zones, Eastern Baltic coast: Gulf of Gdansk, Gulf of Riga, Northeastern Baltic coast: Neva Estuary and Gulf of Finland, Western Baltic coast: Stockholm Archipelago, Askö area and Himmerfjärden, Odense Fjord and Kerteminde Fjord/Kertinge Nor. This volume also presents a synthesis of the common and distinguishing characteristics and processes of the coastal waters compared with the Baltic Proper, as well as highlighting research deficits. An outlook on further developments in coastal research rounds off the volume.