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What is an estuary?

The Estuary—where fresh and saltwater mix.

Estuaries: Where the River Meets the Sea Here's an overview in under two minutes. Transcript

Estuaries and their surrounding wetlands are bodies of water usually found where rivers meet the sea. Estuaries are home to unique plant and animal communities that have adapted to brackish water—a mixture of fresh water draining from the land and salty seawater.

However, there are also several types of entirely freshwater ecosystems that have many similar characteristics to the traditional brackish estuaries. For example, along the Great Lakes, river water with very different chemical and physical characteristics mixes with lake water in coastal wetlands that are affected by tides and storms just like estuaries along the oceanic coasts. These freshwater estuaries also provide many of the ecosystem services and functions that brackish estuaries do, such as serving as natural filters for runoff and providing nursery grounds for many species of birds, fish, and other animals.

Estuaries are among the most productive ecosystems in the world. Many animals rely on estuaries for food, places to breed, and migration stopovers.

Estuaries are delicate ecosystems. Congress created the National Estuarine Research Reserve System to protect more than one million acres of estuarine land and water. These estuarine reserves provide essential habitat for wildlife, offer educational opportunities for students, and serve as living laboratories for scientists.

Video Transcript

Estuaries: Where the River Meets the Sea. Estuaries. Where freshwater rivers meet the salty open sea. There is a lot to love in an estuary. A popular destination for fishing, boating, birding and hiking, estuaries are a beautiful place to be. Miles of beaches, flowing grasses, marshes, creeks, and streams. This salty freshwater mix is where life begins and is the nursing grounds for 75% of the fish we catch. Estuaries are lined with marshes and sea grasses that filter water flowing to the ocean and act as a buffer protecting us from coastal storms. NOAA works closely with coastal states to manage the National Estuarine Research Reserve System of 28 protected areas along the nation’s coasts. These valuable reserves are living laboratories for scientists and exciting, hands-on classrooms for students and teachers. At the reserves, scientists study sea level rise, water pollution, erosion, and impacts of human development. These studies provide strong scientific knowledge to help us create healthy, productive estuaries. The Chesapeake Bay, the ACE Basin in South Carolina, and San Francisco Bay in California, are just a few of the 28 reserves that can be found near you . So visit an estuary and experience firsthand the beauty and wildlife where the river meets the sea.

Did you know?

Humans also rely on estuaries for food, recreation, jobs, and coastal protection. Of the 32 largest cities in the world, 22 are located on estuaries!

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Last updated:
02/26/21

Author: NOAA

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