1. Estuaries

2. What is an Estuary?
An estuary is the tidal mouth of a river and is made up of brackish water.
(Mix of fresh and salt water- salinities vary)
Examples: bays (San Antonio Bay), sounds (Puget Sound), or inlets.

3. Characteristics of Estuaries
Freshwater from the river is prevented from flowing directly into the open sea by one or more land formations, such as peninsulas and barrier islands.
An estuary forms a transition zone between freshwater and saltwater.

5. Estuaries are characterized by silt carried in from terrestrial runoff (from rivers) and from offshore (carried in by tides and waves).
The pH, salinity, and water levels of estuaries vary.

6. An estuary retains many nutrients from both land and sea, and it protects water quality. It forms a very productive ecosystem.
Estuaries are a source of food (fish, shrimp, oysters, …) and human settlements are built near them.
Recreational activities include fishing, boating, and tourism.

7. Map of towns near Copano and San Antonio Bays
Shrimp Boat in a Texas Bay
Map of towns near Copano and San Antonio Bays

8. Dolphin Watching Tour Boat
Fishing the Bays on the Texas Coast

9. Human Development in Estuaries
Of the 32 largest cities in the world, 22 are located on estuaries.
Ex. New York is located at the mouth of the Hudson River estuary

10. Threats to Estuaries
Estuaries are under threat from pollution and overfishing.
Estuaries are impacted by events far upstream and concentrate materials such as pollutants and sediments.
Land run-off and wastes enter rivers and are discharged into estuaries.

11. Galveston Bay Pollution
Kayak Fishing in Copano Bay

12. Estuaries tend to be eutrophic because of nutrients from runoff.
fertilizers and waste from livestock and humans.
Excess chemicals in the water can lead to oxygen depletions and the create dead zones.
This can cause poor water quality and lower fish and other animal populations.

13. Gulf Intracoastal Waterway
The Gulf Intracoastal Waterway stretches 1,050 miles along the Gulf of Mexico from Brownsville to St. Marks, FL.
It runs behind barrier islands through estuary and coastal marsh ecosystems.
The majority of this cargo is classified as petroleum- and chemical-related products.
Cargo carried on the waterway reduces congestion on highways and rail lines, decreases maintenance costs and extends the life of these systems
The GIW was built through many very productive and delicate estuaries and damage was done by dredging and disposal of sediment