What is an estuary?

Estuaries are semi-enclosed coastal waterbodies where freshwater and seawater meet and mix. The freshwater enters these basins via several routes, including rivers and streams, groundwater upwelling and surface runoff. Due to the seasonal fluctuations of salinity, temperature and turbidity, estuaries are dynamic in nature and therefore extremely complex ecosystems. Estuaries provide important spawning and nursery grounds for many species of finfish and shellfish. Critical habitats such as beaches and dunes, tidal marshes, mud flats and seagrass beds found in estuaries provide food and cover for numerous birds, mammals and marine organisms. Estuaries are recognized as some of the most productive ecosystems on the face of the earth.