Coastal lagoons are particularly complex environments in which the transition between marine and continental waters is gradual, due to the continuity of the aquatic habitat. They are characterised by major fluctuations in chemical and physical parameters, which reflect multiple interactions between the distance to the sea, water depth, the nature of the sediment, organic matter quality, hydrodynamic turnover time, tidal currents, wind forced currents, volume lost by evaporation, and gravitational circulation. This book presents current research from across the globe in the study of lagoons, their biology, management and environmental impact.