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Estuaries

Estuaries. Semi-enclosed areas where fresh water from rivers mixes with salt water from the ocean. Figure 10.22. Figure 12.01. Bar built Estuary off Of Cape Hatteras. Estuaries. Dramatic fluctuations in salinity Salinity increases with depth Salinity decreases upstream

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Estuaries

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  1. Estuaries • Semi-enclosed areas where fresh water from rivers mixes with salt water from the ocean

  2. Figure 10.22

  3. Figure 12.01 Bar built Estuary off Of Cape Hatteras

  4. Estuaries • Dramatic fluctuations in salinity • Salinity increases with depth • Salinity decreases upstream • Salinity varies with tides

  5. Fnft

  6. Organisms Must Cope with Salinity Changes • Most are euryhaline • Can tolerate a wide range of salinity • Or have restricted ranges

  7. Organisms Must Cope with Salinity Changes • Osmoconformers • Salt concentration varies with salinity • Osmoregulators • Maintain constant salt concentration in their bodies

  8. estuarine “communities” • Open Water • Mud (or Salt) Flats • Salt Marsh • Mangroves

  9. Open Water Community • Marine plankton comes in and out with tides • Many fish use estuaries as nurseries

  10. Figure 12.09

  11. Mud Flats • Where the bottom of estuary becomes exposed at low tide • Many infaunal deposit feeders

  12. Shoal/Mud Flat

  13. Snails, clams, shrimp, & worms

  14. Figure 12.12

  15. Figure 12.13b

  16. What lives In the Bottom? • Benthic Community! • Infaunal Organisms • Sediment Matters! • Can be “muddy” (like the mud flat) or “sandy” (like the sand flat)

  17. (Bottom) “Intertidal” • “Intertidal” zones, between high and low tide, are predominantly related to ROCKY bottoms on the NORTH SHORE (LIS)…but are made of either SAND or MUD (i.e. “soft bottom” habitats) in bays/ponds etc.

  18. Figure 11.34

  19. Soft Bottom Intertidal Communities • Soft=organisms can burrow • Sandy beaches, mud flats

  20. Soft Bottom Intertidal Communities • Unstable, sediments move due to currents, waves and tides • Can’t hold on • Not many seaweeds • Animals must burrow = infauna • Clams use foot • Crustaceans dig • Sea cucumbers eat

  21. A “foot” in action

  22. Figure 11.31a

  23. Figure 11.31b

  24. Figure 11.31c

  25. Figure 11.31d

  26. Figure 11.32

  27. Soft Bottom Intertidal Communities • Grain size of sediment is important

  28. Sand = coarse; Clay = fine; BOTH = MUD

  29. Diff. grain size = diff. organismal sizes! Fig. 13-23, p.321

  30. What else lives there? • SMALL invertebrates • Clams • Sand Crabs • Meiofauna: Tardigrades

  31. Donax, fnft

  32. Fig. nft

  33. Fig. nft

  34. “Water Bear” (fnft)

  35. Grain Size of sediment • indicates water movement • Calm areas = muddy bottoms • Wave and currents = coarser sediment

  36. Grain Size of sediment • Determines ability to stay wet • Coarse sediments drain fast • Fine sediments drain slower • Mixture – blocks water drainage

  37. Figure 11.28a

  38. Figure 11.28b

  39. Figure 11.28c

  40. Problems of living in sediment • Dessication is NOT as much of a problem • But it is in coarse sediments

  41. Problems of living in sediment • Food availability • Most infauna are deposit feeders or suspension feeders • More organic matter (detritus) in fine sediments

  42. Problems of living in sediment • Oxygen availability • Used up by animals and bacteria • Replenished by water flowing though sediment • Problem in muddy bottoms

  43. Problems of living in sediment • Oxygen availability • Anoxic = no oxygen • Animals may pump water from the sediment surface or adapt to low oxygen

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