1. Ecosystem #3
The Estuary

2. What is an Estuary?
A semi-enclosed body of water where freshwater and saltwater mix
Other names for estuaries:
Bay
Sound
Lagoon
Inlet

3. Estuary Classification
Origin
Degree of Mixing

4. Types of Estuaries by Origin
Coastal Plain
Tectonic
Bar Built (or Barrier Island Estuary)
Fjord

5. #1: Coastal Plain Estuary
Most common
Sometimes called a Drowned River Valley
Formed at the end of the last ice age when rising water flooded (or drowned) existing river valleys
Examples:
Tampa Bay Chesapeake Bay (MD), Narragansett Bay (RI)

6. Coastal Plain Estuary
Chesapeake Bay (MD)

7. #2: Tectonic Estuary
Caused by earthquakes where folding or faulting may create bays with narrow inlets to the sea
Examples:
San Francisco Bay

8. Tectonic Estuary

9. #3: Bar Built Estuary Also called Barrier Island Estuaries
These are most commonly barrier islands that are separated from land by a shallow lagoon
Usually shallow with reduced tidal action
Examples:
Common along the Texas and Florida Gulf Coasts and the Outer Banks of NC

10. Bar Built Estuary

11. #4: Fjords
Valleys that have been cut deeper by moving glaciers and then invaded by the sea
Usually narrow, straight, long and with steep sides
Examples:
Alaska, Canada, Norway, etc.

12. Fjords

13. Estuary Classification by Stratification
Degree of Mixing

14. Degree of Mixing?
Estuaries can be classified by how the freshwater and saltwater mix
The basic flow pattern
Freshwater flows on the surface toward the ocean while seawater flows into the estuary below the surface

15. Most Common Types of Mixing
Vertically Mixed
Salinity is consistent from top to bottom
Slightly Stratified/Partially Mixed
Lower layers of water typically saltier than upper layers (Ex. Tampa Bay)
Highly Stratified/Salt Wedge
Least mixed
Forms when a rapidly flowing large river enters the ocean in an area where tidal range is low
Example: Mississippi River

16. Salt Wedge
Vertically Mixed
Partially Mixed

17. Use 2 colors to indicate freshwater vs. saltwater and be sure to label
In your notes, draw a sketch of what each type of mixing would look like!
Use 2 colors to indicate freshwater vs. saltwater and be sure to label

19. Why are Estuaries Important?
Video Clip
Record in your notes

20. Why are Estuaries Important?
Habitat for may plants and animals (including land dwellers like humans & birds)
Nursery ground
Protect water quality by filtering out dirt and pollution
Recreation (fish, swim, kayak, bird watch, etc.)
Economy (food, fishing charters and other recreation)

21. Importance Cont’d…
Estuaries trap and accumulate sediment that comes from rivers which makes the estuary rich in nutrients (elements & compounds) and biologically productive (lots of plants & animals)
What problems can you foresee with this process…

22. Eutrophication
An overabundance of nutrients that causes an ecological imbalance
Fertilizer runoff is also trapped in estuaries

25. What limits productivity in an estuary?
White Boards:
What limits productivity in an estuary?
In other words, what may keep living things from spending time in an estuary?

26. What Limits Productivity in an Estuary?
Organisms must be able to tolerate a wide range of salinities
Osmotic stress caused by tides
Decomposition depletes the oxygen in nutrient rich sediment
The rotten egg smell is a result of sulfides released by anaerobic sulfur bacteria

27. Everything is Connected!
How do estuaries contribute to the productivity of adjacent ecosystems?
By increasing the number of individuals that survive to adulthood
Safer than the open ocean
By providing nutrients while reducing eutrophication & other damage that could make its way out to the open ocean