Estuaries

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Estuaries

• October 23, 2007

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What is an Estuary?

• A partially enclosed body of water in which salty
  ocean water is significantly diluted by fresh
  water from land runoff
• Transition between freshwater and saltwater
  ecosystems

The East Alligator River Northwest Territories,
Canada
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Types of Estuaries
Fjord - Geiranger Fjord, Norway
Tectonic - San Francisco Bay
Bar-built - Laguna Madre, TX
Coastal Plain - Chesapeake Bay
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Classifying Estuaries by Mixing

• Salt Wedge Caused by a strong, high volume
  river
• Partially Mixed Salinity increases from the
  head to the mouth of the estuary at any depth
• Well Mixed A shallow, low volume estuary where
  there is no vertical salinity gradient

http//www.icsu-scope.org/downloadpubs/scope50/cha
pter05.html
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Estuarine Organisms

• What effects organisms that live in estuaries?
• Salinity
• Flow
• Organisms originate from 2 possible sources
  freshwater or saltwater
• Harsh environment, low productivity, low diversity

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Coping with Salinity Changes

• Euryhaline vs. Stenohaline species
• Where would each type of species live in an
  esturary?
• Osmoregulators vs. Osmoconformers

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Tidal Flow

• Direct effects on Organisms
• Tidal Bores
• Retention/Dispersal (especially for larvae)
• How does tidal flow affect salinity gradients in
  an estuary?
• Behavioral adaptations

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• What are the odds of planktonic larvae
  successfully settling on the sea floor?

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Open Ocean Estuarine Communities

• Anadromous
• Catadromous

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Mudflats

• Salinity has less of an effect
• Lack of Oxygen
• Infauna dominate
• Deposit and suspension feeders dominate
• especially feeding on detritus

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Human Impact on Estuaries

• Urban Development
• Reduction of Freshwater Input
• Nutrient Input

Mission Bay, 1935
Mission Bay, Now