Estuaries

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Estuaries
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Origins

• Drowned river valleys
• Fjord types
• Bar-built
• Vegetated sand bars
• Tectonic Processes
• Ex subsidence

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Variable salinity and the Salt wedge

• The most characteristic feature variable
  salinity ? the salt wedge

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• organisms
• low diversity
• high biomass and productivity
• sedimentation and fertility at salt/fresh
  interphase

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Eutrophic Estuaries

• Reasons for unusually high productivity
• Tidal action ? constant source of nutrients and
  food
• Flocculation ? provides food particles for
  smaller animals
• Increased nutrient recycling and benthic animal
  growth during low tide
• Large allochthonous inputs from wetlands

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The Biota

• Marsh Plants Spartina, Carex, Salicornia,
  Juncus, Scirpus
• Seaweeds Ulva, Gigartina
• Microalgae diatoms, dinoflagellates (red tides,
  PSP)
• Zooplankton Acartia, Coraphium, Neomysis
• Benthic animals
• Fisheries

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Tropical Estuaries

• mangrove swamps