What are estuaries?

Estuaries are partly enclosed bodies of water where fresh water coming down the rivers mixes with salt water from the sea. A range of coastal landforms fits this description, including bays, harbors, inlets, lagoons, and some wetlands.

There are many types of estuaries in California including:

Why are they important?

Estuaries provide us with a suite of resources, benefits, and services. Some of these can be measured in dollars and cents, others cannot. Estuaries provide natural resouces with commercial value, places for recreational activities, scientific study, and aesthetic enjoyment. They are an irreplaceable natural resource that must be managed carefully for the mutual benefit of all who enjoy and depend on them.

Environmental Benefits

Thousands of species of birds, mammals, fish, and other wildlife depend on estuarine habitats as places to live, feed, and reproduce. And many marine organisms, including most commercially-important species of fish, depend on estuaries at some point during their development. Because they are biologically productive, estuaries provide ideal areas for migratory birds to rest and re-fuel during their long journeys. Because many species of fish and wildlife rely on the sheltered waters of estuaries as protected spawning places, estuaries are often called the "nurseries of the sea."

Economic Benefits

Estuaries have important commercial value and their resources provide economic benefits for tourism, fisheries, and recreational activities. The protected coastal waters of estuaries also support important public infrastructure, serving as harbors and ports vital for shipping and transportation.

Ecosystem Services

Estuaries also perform other valuable services. Water draining from uplands carries sediments, nutrients, and other pollutants to estuaries. As the water flows through wetlands such as swamps and salt marshes, much of the sediments and pollutants are filtered out. This filtration process creates cleaner and clearer water, which benefits both people and marine life. Wetland plants and soils also act as natural buffers between the land and ocean, absorbing flood waters and dissipating storm surges. This protects upland habitat as well as valuable real estate from storm and flood damage. Salt marsh grasses and other estuarine plants also help prevent erosion and stabilize shorelines.

Learn more about estuaries

EPA - Basic Information about Estuaries