Transitional Ecosystems - Brackish Water

1. Transitional Ecosystems - Brackish Water

2. I. Brackish water –is a term used for areas where freshwater combines with salty ocean water. A. It is not as salty as the oceans B. Examples-bays, inlets, and ocean-flooded river valleys. C. These partially enclosed ecosystems are commonly known as Estuaries.

3. II. Types of Estuaries A. Four different types B. Classified based on how they were formed.

4. Coastal Plain Estuaries- 1. formed by the sea level rising and filling an existing river valley. • 2. Chesapeake Bay in Maryland-example

5. Coastal Plain Estuaries

6. B. Fjords – 1. U-shaped valleys formed by glacial Action. 2. Developed as sea levels rose slowly over the last 18,000 years, filling river valleys and glacial troughs. 3. Very steep walls are characteristic 4. Northern Europe, Alaska and Canada-examples

8. Fjords

9. C. Bar-built Bays/Lagoons – 1. Formed when a shallow lagoon or bay is protected from the ocean by a sand bar or barrier island. 2. Seawater flowing towards the coast mixes with freshwater runoff diluting water behind the sand bars. 3. The Eastern Seaboard and the Gulf Coast-examples

11. Bar-built Estuaries

12. D. Tectonics –1. Formed by the folding or faulting of land surfaces along major fault lines creating low-lying, coastal areas. 2. San Francisco Bay-example

13. Tectonic Estuaries

14. III. Halocline A. Definition – a salinity gradient where two water masses meet. (freshwater and sea water) B. Denser salt water sinks below the less dense freshwater. C. Levels of salinity concentration increase from 0 at coastline to 35ppt (3.5%) in the open sea.

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16. Salt wedge – Highly stratified with Halocline separating upper layer of low-density freshwater from the bottom layer of high-density saltwater wedge. • Partially Mixed – Halocline usually poorly defined. D. Structure of Halocline

17. IV. Salinity and Species Diversity • The degree of salt in the water determines the types of species • found in that water. • B. The greatest challenge of estuary • organisms is maintaining waterand • salt balance in cells and bodily fluids.

19. C. Estuary organisms generally tolerate a wide range of salinity. • Four Classes of Estuary Organisms • 1. Freshwater Organisms – species tolerating very little salt. • 2. Brackish Water Organisms – species found in mixed salt and freshwater. • 3. Euryhaline Organisms – species that tolerate a wide range of salinity. • 4. Stenohaline Organisms – species • that tolerate only a narrow range of salinity.