Estuaries

Estuaries

What are Estuaries?

Estuaries are the places where freshwater from rivers mixes with salt water from the oceans. The Chesapeake Bay is the largest estuary in the United States.

Multiple Choice

An estuary is best defined as a place where--

• fresh and salt water meet

• a river meets the Chesapeake Bay

• a group of animals are gathered

• the water from the land flows into a river

Salt Level of Estuaries

Each day as the tide rises, saltwater is brought into the estuary. Freshwater comes down the rivers and creeks and mixes with this saltwater. During the dry season there may not be much freshwater flowing down the rivers. This can make the estuary very salty. When the river brings in extra water after heavy rainfall, the salinity, or the amount of salt, in the water of the bay will be reduced and the water is less salty. The plants and animals that live in an estuary must be able to adapt to the changes in salinity.

Multiple Choice

When there is not as much fresh water entering an estuary, the amount of salt will

• decrease

• increase

Multiple Choice

More salt water entering an estuary will cause there to be a higher or lower salt content

• higher

• lower

What live in Estuaries?

The sheltered waters of estuaries are home to countless plants and animals that like to live in water that is part fresh and part salty. Examples include horseshoe crabs, ospreys, manatees, mangroves, and sea grasses. Hundreds of fish and shellfish, such as scallops, shrimp, and salmon, live in estuaries at some point in their life.

Estuaries and Water Quality

Estuaries protect water quality by filtering out dirt and pollution. These habitats also filter out pollution from the water and protect the surrounding region from flooding.   As we build more homes and businesses around estuaries and pave new roads, we are destroying precious habitats and threatening the water quality of the estuary. 

Multiple Choice

Estuaries protect water quality by

• causing floods

• filtering out dirt and pollution

• causing more pollution

Estuaries and Nutrients

Plants and animals need nutrients, or “food,” such as nitrogen and phosphorus, in order to grow. However, if an estuary has too many nutrients, too much algae will grow, creating algae blooms. These algae blooms block sunlight and can suffocate fish and plant life by using up valuable oxygen from the water. Nutrients can enter estuaries from sewage treatment plants, septic systems, and fertilizers used in farming and on lawns, and polluted air from power plants and cars.

Multiple Choice

Algae blooms can block _____ and use up _____.

• water, sunlight

• sunlight, oxygen

• food, saltwater

Multiple Choice

How can too many nutrients get in the water?

• overusing fertilizers

• trash

• oil spills