Estuary: Definition, Facts, Characteristics & Examples

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: What is the Biogeochemical Cycle? - Definition & Explanation

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:00 What Is an Estuary?
  • 0:42 The Estaurine Environment
  • 2:25 Lake Estuaries
  • 2:59 Examples of Estuaries
  • 3:45 Estuaries at Risk
  • 4:42 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Mary Ellen Ellis
Have you ever gone swimming, kayaking, or exploring in a marshy coastal area? If so, you were enjoying the natural beauty of an estuary, a place where rivers meet large bodies of water. These unique ecosystems are important, but also under threat.

What Is an Estuary?

An estuary is a body of water along a coast or beach that is partially enclosed by land and open to the ocean or a large lake. Estuaries occur where rivers and streams meet each other, lakes, and/or the ocean. The freshwater of rivers and streams mix with the salt water of the ocean to create brackish water; it's like a transitional ecosystem from river to sea! Like the ocean beyond, a coastal estuary is influenced by tides and weather, but it's also largely protected from the waves, storms, and strong winds that the rest of the coast experiences.

The Estuarine Environment

Estuaries are unique ecosystems unlike any other on Earth. Because the rivers forming estuaries deposit eroded materials and estuaries can host a mix of freshwater and salt water flowing in from the ocean, these ecosystems are among the most productive on Earth. This means they create more organic material than most other types of environments. All of this organic matter creates a nutrient-rich ecosystem that animals rely on for food.

The uniquely sheltered environment of an estuary is also important to the diversity of the ecosystem. Estuaries provide a safe place to live, a breeding ground, and a safe rest stop for migrating animals, along with the food needed to survive. The result is a rich, diverse, and important place for a variety of animals and plants.

For us humans, estuaries are valuable natural resources. Besides the abundance of natural beauty and the opportunity to spot wildlife, estuaries provide other, more tangible resources. Estuaries are important as recreational and scientific study sites. They also often serve as ports and harbors for cities and are the sites of abundant fisheries.

From an environmental perspective, estuaries are important to humans, animals, and plants because they provide a filtering service. As water comes down toward an estuary from uplands, it moves through wetlands, marshes, and swamps, where pollutants and sediments are removed. This results in cleaner water, which is important to the animals and plants living in estuaries and to us humans making use of the resources they provide. Estuaries also protect us from storms by providing a barrier between storm surges and infrastructure.

Lake Estuaries

Not all estuaries are along ocean coastlines, and not all involve brackish water. Rivers that empty into large freshwater bodies, like the Great Lakes, produce a special kind of estuary. These don't get the mix of salt water and freshwater that make ocean estuaries so unique, but there are chemical and physical differences between rivers and lakes that make up freshwater estuaries. These types of estuaries play ecological roles similar to that of salt water estuaries, like filtering water and playing host to fish and bird nurseries.

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account