1. Estuaries

2. Estuaries
Semi-enclosed, transition areas where freshwater mixes with salt water (called brackish water)
There are nearly 900 estuaries in the United States. Most of them were formed at the end of the last glacial period by rising sea level.
Seawater flooded the land and was trapped by barrier island bays, river deltas and earthquakes
Seawater flooded the land and was trapped by barrier island bays, river deltas and earthquakes

3. Characteristics
Lower salinity with more euryhaline organisms that stenohaline organisms.
Good light and a low amount of suspended solids (silt) that allows the primary producers (sea grasses) to grow.
Nutrients that come from river runoff and provide for a detritus-based chain; the inverted energy pyramid increases productivity.
Euryhaline organims- organisms that are adapted to a wide range of salinity.
Detritus-based chain- the primary consumers are detretivores that survive off of the waste material that has flown down the river. Such as bacteria, fungi, protozoans
Stenohaline Organisms- organism, usually fish, that cannot tolerate a wide fluctuation in the salinity of water

4. Productivity and biomass are extremely high.
Diversity of species is directly related to fluctuations in salinity, temperature, Oxygen, nutrients, and light

5. Salt Wedges
Form under river runoff when the tide comes in. This creates layers of salinity where the river and sea meet.

6. The shallow waters of estuaries restricts large predators
Tidal ebb with river runoff causes a net flushing of estuaries that transport larvae and nutrients into the ocean.

7. 3 Most common types of estuarine environments:
Salt Marshes
Mud-Flats
Sea Grass Communities

8. Salt Marshes Also called wetlands, swamps or mangrove communities.
Producers like Spartina (marsh hay and cord grass) are found mostly in intertidal water.
During the summer, grasses die and provide nutrients for crabs, isopods, snails, and worms.
However as warm weather increases productivity, oxygen depletion can occur.
Examples: The Mississippi Delta

9. Mudflats
Also known as oyster reefs found in lower intertidal and subtidal zones
Primarily composed of bacteria and fungi that carry out anaerobic metabolism.
Infauna have a more stable environment than the epifauna because mud traps the salt.
Example:
Cape Cod, Massachusetts

10. Sea Grass Communities
primarily subtidal zones where animals find food and hiding places.
Sea grasses stabilize the substrate and air tubes from the leaves to the roots help oxygenate plants living in anaerobic mud.
Salt excreting leaves of grass, slow currents and provides a place of attachment to prevent animals from smothering in the sediments.

11. Estuaries are usually the first dumping site for pollution and industrial discharges.
Dredge and fill operations that improve navigation and drainage, but it harms wildlife and stirs up pollution that is trapped in the sediments.

12. People thought estuaries (swamps) could be “improved by filling them in for housing developments.
Retention ponds and detention lakes do not replace estuaries if there is no outlet to the sea.

13. Final Thoughts
Estuaries are important because they support a large commercial seafood industry, prevent coastal erosion, trap sediments from entering the sea, provide recreation, wildlife habitat and …