This is a map of estuaries in the Mid-Atlantic region of the U.S. eastern coast including the well-known Chesapeake Bay Estuary. Notice how the rivers get very wide as they get closer to the ocean? This is where the salt water of the ocean is mixing with the fresh water of the rivers.
Click on image for full size
Courtesy of the EPA.
An estuary is an unique environment where fresh water and salt water come together. Estuaries are found on the coast where a river or bay or other source of fresh water has access to the open sea. A good example of an estuary is a salt marsh that can be found close to the coast. Another example is when a river
feeds directly into the ocean.
The largest estuary in the United States is the Chesapeake Bay
estuary on the east coast of the U.S.
Estuaries are affected by the tides. So, there can be changes of salinity, temperature and other physical properties in an estuarial system which means the organisms there must be very tolerant to change. Even with that consideration, estuaries are among the most fertile places in the world. All kinds of plants and animals live there! When looking at estuaries, scientists quickly realized that these areas were extremely nutrient-rich because of sediment deposit of rivers, creeks or streams feeding into the salt water environment.
Unfortunately, estuaries haven't always been seen as valuable. In the past, they were seen as worthless and were used as dumps, or places for new land development (by filling in the marshy area!). In 1972, Congress created the National Estuarine Research Reserve System (NERRS) to establish, manage, and maintain estuary reserves, and to provide for their long-term stewardship.
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