An ESTUARY is a partially enclosed, coastal body of water where a river meets the ocean.    Estuaries are transition zones between fresh river environments and saline ocean environments.  Estuaries are subject to the tides, waves, and changes in salinity based on precipitation and river flow.

The Great Bay Estuary forms at the end of the Piscataqua River and the Gulf of Maine.

Estuaries are also rich and important habitats for many species of marine life and support high productivity.  Estuaries are fragile ecosystems as they are influenced by both what happens upstream in the river and what happens in the coastal environment.

The mouth of an estuary.