1. Estuaries Chapter 12

2. Estuary Semi-enclosed area where freshwater meets and mixes with salt water Chesapeake Bay, Galveston Bay, Hudson River Estuary, Bodega Bay

3. Physical Characteristics: Salinity Varies between 35 ppt and 0 ppt Lower salinity farther upriver, higher salinity closer to ocean Higher salinity deeper Salt wedge Moves with the tide

4. Physical Characteristics: Water Movement Tides create dramatic currents Exposes parts of the estuary regularly Tidal bores (video)

5. Physical Characteristics: Nutrients High nutrient load from runoff Eutrophication: Blooms of algae because of too many nutrients

6. Physical Characteristics: Substrate Rivers carry lots of substrate Fine particulates of sand and mud Sediments mostly anoxic (no oxygen) Bacteria use up oxygen Not a lot of water in sediment to replenish Produce hydrogen sulfide that anaerobic bacteria can live in.

7. Physical Characteristics: Temperature Temperature can fluctuate rapidly Salinity can change drastically because of heat-induced evaporation

8. Adaptations Needed Salinity Temperature Desiccation Currents Sediment instability

9. Tolerating Low Salinities Most are marine organisms that have adapted to low saline environments Euryhaline = organisms that can tolerate wide ranges of salinity Stenohaline = organisms that can only tolerate a narrow range of salinity

10. Changes in Salinity Organisms can: Swim or move away Close their shell Regulate their salinity

11. Regulating Salinity Osmoconformers = organisms that allow their body salinity to change with the water Osmoregulators = organisms that keep the salinity in their body relatively constant Need to use active transport or osmosis depending on water salinity

12. Plants and Salinity Some plants have very high tolerances to salinity Some have special pores to excrete salt Some take up extra water to dilute the salts (pickleweed and other succulents)

13. Changes in Temperature Live in the mud Move Heat shock proteins

14. Dessication Close shells Move Burrow deeper

15. Currents Burrow Locate areas downstream of jetties Byssal threads Glue

16. Mud is sticky Organisms can burrow into it Move very slowly Changes in salinity are less in the substrate Can pump water through burrow to oxygenate or have hemoglobin to store oxygen better Plant roots can stabilize

17. Estuary Communities Open Water Mudflats Salt Marshes Seagrasses Oyster Beds Mangroves