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Estuaries

Estuaries. Chapter 12. Estuary. Semi-enclosed area where freshwater meets and mixes with salt water Chesapeake Bay, Galveston Bay, Hudson River Estuary, Bodega Bay. Physical Characteristics: Salinity. Varies between 35 ppt and 0 ppt

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Estuaries

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  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

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