Simply put, an estuary is an inlet of the sea; a place where salt water from the ocean mixes with freshwater from a river or a stream. Influenced by the tides and sheltered by the land, estuaries are among Earth’s most productive and diverse ecosystems.
These places of transition are home to an array of habitat types, including saltwater marshes, mud flats, oyster reefs, mangrove forests, tidal pools, and sea grass meadows.
The unique habitats found in estuaries support plants and animals adapted to life at the edge of the sea. Species like blue crab and mangroves have evolved to respond quickly to changes in salinity, temperature, and water level. Migratory birds rely on estuaries as refueling stations. And many commercially-important fish, crustaceans, and shellfish use their sheltered waters for spawning.
But estuaries are about more than wildlife and beauty. They also perform valuable services. When water from the land is washed into estuaries, they filter out sediments and pollutants, such as fertilizer and pesticides, resulting in cleaner water for all. By buffering storm surges, estuaries minimize flood damage. And when estuarine plants are allowed to flourish, they minimize erosion and stabilize shorelines
To date, more than half of the U.S. population lives in coastal areas—and these numbers are steadily increasing. Many estuaries have already been heavily degraded by harbors, ports, and other forms of development.
Understanding these estuaries, and the services they provide, is a first step in protecting them, now and for future generations.
Photo, taken on November 14, 2008, courtesy of Laura Longenecker via Flickr.