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Estuaries are bodies of water and their surrounding coastal habitats are typically found where rivers meet the sea. Estuaries harbor unique plant and animal communities because their waters are brackish — a mixture of fresh water draining from the land and salty seawater.

Estuaries are some of the most productive ecosystems in the world. Many animal species rely on estuaries for food and as places to nest and breed. Human communities also rely on estuaries for food, recreation, and jobs.

Of the 32 largest cities in the world, 22 are located on estuaries. Not surprisingly, human activities have led to a decline in the health of estuaries, making them one of the most threatened ecosystems on Earth. NOAA's National Estuarine Research Reserve System (NERRS), in partnership with coastal states, monitors the health of estuaries, educates the public about these ecosystems, and helps communities manage their coastal resources.

map of estuaries

Estuaries are both beautiful and ecologically bountiful. Their natural expanses provide habitats for a wide range of animal and plant species. This is an image of the Old Woman Creek National Estuarine Research Reserve. It is located on the south-central shore of Lake Erie in Erie County, Ohio, three miles east of Huron. It is one of the "Great Lakes-type" freshwater estuaries in the National Estuarine Research Reserve System, and features freshwater marshes, swamp forests, a barrier beach, an upland forest, and a portion of nearshore Lake Erie. (Photo Credit: Jennifer Buchiet, Old Woman Creek Reserve)

Hudson river estuary

New York City, with a population of over eight million people, is located at the mouth of the Hudson River Estuary which stretches 153 miles inland from the Atlantic Ocean and includes a wide range of wetland habitats. Home to more than 200 species of fish, the Hudson River Estuary serves as a nursery ground for sturgeon, striped bass, and American shad. It also supports an abundance of other river-dependent wildlife, especially birds.

map of estuaries

Estuarine habitats are typically found where rivers meet the sea. This image shows the eastern half of North America as viewed from space. Mouse over the image to see some of the estuarine areas highlighted in this tutorial. And you can see that most of the land area drains into the Great Lakes, the Atlantic Ocean, and the Gulf of Mexico. Wherever freshwater rivers drain into these larger bodies of water, estuarine habitats are found.

The yellow squares in the image indicate some of the North American estuaries that contain NOAA's national estuarine research reserves.

These estuaries lessons are an overview of estuarine habitats, the threats facing them, and efforts to monitor and protect estuaries nationwide.

The Roadmap to Resources complements the information in the tutorial by directing you to specific online estuary-related materials from NOAA and other reliable resources.

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Roadmap to Resources Subject Review
NSTA - National Science Teachers Association

The National Science Teaching Association (NSTA) includes this resource in its database. NSTA provides educators and students access to Web-based, educationally appropriate science content that has been formally evaluated by master teachers.

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Author: NOAA

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