Based on a fifty-year study conducted by the Leibniz Institute for Baltic Sea Research, this book brings together a comprehensive summary of their observations and findings. Written by well-known experts, this revealing book concentrates on long-term changes in the Baltic Sea which can be extrapolated to shed light on the environmental problems of other shelf seas, brackish seas, and large estuaries thereby contributing to our understanding of water exchange processes, eutrophication, and climatic impacts at the forefront of international concern.