Ask a Scientist!

What is an estuary?
If the Chesapeake Bay is the largest estuary in the United States, where is the largest estuary in the world located?

Estuaries are found on the coast where fresh water from a river or a bay mixes with the ocean. The largest estuary in the United States is the Chesapeake Bay. The Chesapeake Bay is fed freshwater from the thousands of miles of tributaries and rivers, while the saltwater is provided by the Atlantic Ocean. The mixing of fresh and salt water creates a unique environment, providing for a diverse ecosystem that creates habitat for countless numbers of plants and animals.

Photo of Chesapeake Bay Estuary courtesy of Lisa GuiterrezAs the levels of salt in the Bay increase or decrease it allows for visits from animals that you would not think enter the Bay. Sandbar sharks, dolphins and stingrays make there way all the way up to the middle Bay in periods of high salinity which can result from low rain or drought conditions. The salt can also retreat down the Bay when hurricanes or tropical storms move through the Bay watershed.

The largest estuary in the world is the Saint Lawrence River which connects the Great Lakes with the Atlantic Ocean. It is the primary drainage of the Great Lakes Basin. The majority of the estuary is located in Canada but portions of the river do touch the borders of New York. The estuary is over 1,900 miles long and the watershed occupies 390,000 square miles, while the Chesapeake Bay is 200 miles long (Harve De Grace, MD to Norfolk, VA) and encompasses 64,000 square miles.

- Ron Klauda
Manta Director
Maryland Department of Natural Resources

Photo of Chesapeake Bay Estuary
courtesy of Lisa Guiterrez

For more information:

Bay Link

Ask an Expert Archives