What is an Estuary?

An Eider seeks respite from the winter ice on a Cape beach.

 An estuary is a partially enclosed body of water formed where freshwater from rivers and streams flows into the ocean and mixes with seawater. Estuaries are places of transition from land to sea, and from fresh to saltwater. Simply put, estuaries are "where the river meets the sea." Although influenced by the tides, estuaries are protected from the full force of ocean waves, winds and storms by the reefs, barrier islands, or fingers of land, mud, or sand that define an estuary's coastal boundary. Estuaries come in all shapes and sizes, and are called many different names -- bays, lagoons, harbors, inlets, or sounds.

Why are estuaries important?

Estuaries are important to both human and marine life. The tidal, sheltered waters of estuaries support unique communities of plants and animals that live at the margin of the sea. Examples in Massachusetts include horseshoe crabs, blue herons, striped bass, and eelgrass. Hundreds of marine organisms, including herring, shrimp and Atlantic salmon, depend on estuaries at some point during their development. Wetland and aquatic vegetation in and around estuaries provide habitat for marine life and protect water quality by filtering out dirt and pollution.

hermit crab 200x131
Estuaries also have economic, recreational and aesthetic value. Boating, fishing, swimming and bird watching are just a few of the numerous recreational activities people enjoy in estuaries. Estuaries are often the cultural centers of coastal communities, serving as focal points for local commerce, recreation, celebrations and traditions. For instance, Boston Harbor is a center for countless activities including shipping, marine research, whale watching, and the Harbor Island Park system. Less urban parts of the Massachusetts coast attract visitors from all over New England looking to sunbathe, kayak, sail, hike, and simply enjoy being outdoors. Overall, tourists in coastal Massachusetts spend about $1.5 billion per year, and support over 80,000 jobs. Water based economies such as tourism,commercial fisheries and marinas directly depend on the wealth provided by estuarine natural resources. But estuaries face many challenges.
boats at dock

Because of our love for and dependence on the water, more than half of the nation's population lives within 50 miles off the coast, including the shores of estuaries. Coastal counties are growing three times faster than counties elsewhere in the country. For instance, the number of housing units on Cape Cod more than doubled between 1970 and 2000 (from 65,676 to 147,083); that's adding almost 8 new housing units a day for 30 years. Unfortunately, this increasing concentration of people is upsetting the natural balance of estuaries and threatening their health. Stresses caused by pollution, excessive demands on limited resources, and expansive development have resulted in contaminated drinking water, beach and shellfish closings, harmful algal blooms, declines in fisheries, loss of habitat, fish kills and a host of other human health and natural resource problems.

How does MassBays help?

boy on the beach
MassBays works through our five regional coordinators in our five planning regions to facilitate partnerships to prompt local, state, and federal action and stewardship, convening stakeholders on the local and regional level, providing scientific basis for management decisions, and educating decision makers about problems and solutions.