1. What is an Estuary?
By Ms. Aldridge

2. An estuary is the thin zone along a coastline (such as bays, lagoons, sounds or sloughs) where freshwater systems and rivers meet, and mix with a salty ocean, becoming brackish. 

3. Freshwater estuary
Sometimes, freshwater from rivers mixes with large freshwater bodies creating a "freshwater estuary”, such as the Great Lakes in the northern United States

4. Types
The 5 major types of estuaries are coastal plain, bar-built, delta system, tectonic, and fjords. 
Estuaries are unique places that are valuable to the environment and to society.

5. Estuaries are typically classified by their existing geology or their geologic origins (in other words, how they were formed).

6. Millions of years ago, as ancient glaciers melted, some coastal streams and rivers became covered with water as sea levels rose. The Chesapeake Bay in Maryland and Narragansett Bay in Rhode Island are examples of coastal plain estuaries that were once river valleys.
Coastal Plain

7. Bar-built
Sandbars or barrier islands built up by ocean currents and waves in coastal areas created a protected area fed by small streams or rivers. The barrier islands off the Atlantic coastline of North Carolina are enclosed bar-built estuaries.

8. Delta system
Deltas are formed at the mouths of large rivers from sediment and silt depositing instead of being washed away by currents and waves. When the river flow is restricted by the delta, an estuary may form. The Mississippi River in Louisiana are examples of delta systems.

9. Tectonic
Tectonic estuaries were created when a major crack or a large land sink in the Earth, often caused by earthquakes, produced a basin below sea level that fills with water. These types of estuaries usually occur along fault lines. San Francisco Bay in California is an example of an estuary created by tectonics.

10. Fjords
Advancing glaciers ground out long, narrow valleys with steep sides. Then when glaciers melted, seawater flooded in. Glacier Bay in Alaska is an example of a fjord.

11. Each estuary can make up an individual ecosystem, estuaries are also interconnected with other surrounding environments (oceans, lakes, forests, grassy plains) and nearby human communities. 

12. Estuaries are constantly changing
Estuaries are constantly changing. Some animals and plants specialize in, or adapt to, living in the unique conditions of estuaries. 

13. Estuaries vary widely around the world
Estuaries vary widely around the world. Earth’s changing geology, flowing water and different weather patterns help create many diverse types of habitats.

14. Rivers provide nutrients, organic matter, and sediments to estuaries
Rivers provide nutrients, organic matter, and sediments to estuaries. Rivers flow downstream delivering fresh water from streams, small rocks and silt, and leaves and other vegetation debris. Nutrients support life in the estuary. 

15. Estuaries can filter small amounts of pollutants and runoff
Estuaries can filter small amounts of pollutants and runoff. Vegetation helps filter and trap silt. However, too much nutrient or sediment input will create an unbalanced situation causing the health of the ecosystem to decline.

16. Estuaries act like huge sponges, buffering and protecting upland areas from crashing waves and storms and preventing soil erosion. They soak up excess water from floods and stormy tidal surges driven into shore from strong winds. 

17. Estuaries provide a safe haven and protective nursery for small fish, shellfish, migrating birds, and coastal shore animals. In the U.S., estuaries are nurseries to over 75% of all fish and shellfish harvested.

18. People enjoy living near estuaries and the surrounding coastline
People enjoy living near estuaries and the surrounding coastline. They sail, fish, hike, swim, and enjoy bird watching. An estuary is often the center of a coastal community.

19. Effects of humans
Anthropogenic(resulting from the influence of humans on the natural world) disturbances to estuaries include coastal development, introduction of invasive species, pollution via runoff, over fishing, dredging and filling, dams and global climate change.

20. Coastal Development
Hard surface can no longer absorb water or provide shelter or food for the animals and plants that exist in coastal regions.

21. Invasive Species
Purple loosestrife, nutria, hydrilla, snakehead fish, green crabs, and zebra mussels are just a few invasive species
introduced by humans through dumping of aquaria containing non-native fish. Many exotic species compete for food and shelter, prey on na tive species or push native species out of their natural habitat.

22. Pollution Via Runoff
Water is always moving! Water runs downstream or through the ground from cities, farms and factories, this can carry many things harmful to estuaries such as excess nutrients, raw sewage and manure and chemical waste.

23. Over Fishing
Over fishing reduces the number of organisms in that population and, can have a negative effect the local food web, in turn effecting other species.

24. Dredging and Filling
Filling and draining of wetlands, and dredging deep navigation channels through estuaries and wetlands ultimately destroys and damages habitat. They also change water and sediment flow.

25. Dams
Changing river water flow can restrict sediment deposits and nutrient availability downstream, fish migration, and can increase saltwater into underground water tables.

26. Global Climate Change
Scientists are confident that the Earth’s climate has had change over the past 1,000 years. Changes in temperature of the air and water, increases in sea level, more frequent and intense tropical storms, and changes in coastal currents, all of these changes can cause change!

27. Enjoy
your
trip to
the
Marine
Science
Station!