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Estuaries

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Estuaries - PowerPoint PPT Presentation


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Estuaries. Form where river meets the sea Regions of constant environmental change Importance to marine ecosystems Organic material enriches ocean waters Protection from predators (ex: juvenile fish) Support many commercially important animals that humans rely on for food Fish nurseries

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Presentation Transcript
slide2

Form where river meets the sea

  • Regions of constant environmental change
  • Importance to marine ecosystems
    • Organic material enriches ocean waters
    • Protection from predators (ex: juvenile fish)
    • Support many commercially important animals that humans rely on for food
    • Fish nurseries
  • Fragile habitats
    • Pollution
    • Damage by dams Block freshwater supply
types of estuaries
Types of Estuaries
  • Coastal plain (drowned river valley)
    • Form between glacial periods
    • Form when rising water levels from melting glaciers flood coastal plains and low-lying rivers
types of estuaries1
Types of Estuaries
  • Tectonic
    • Earthquakes caused land to sink, allowing seawater to cover it
types of estuaries2
Types of Estuaries
  • Fjord
    • Form when glaciers carve large valleys in coastal areas
      • Filled with water after glaciers retreated
types of estuaries3
Types of Estuaries
  • Bar-built
    • Form when geographic barriers form a wall between freshwater and saltwater
salinity and mixing patterns
Salinity and Mixing Patterns
  • Salinity varies vertically and horizontally
    • Least salty near the mouth of the river
  • Freshwater flows over the seawater
  • Surface water is less dense and flows out to sea
  • Denser saltwater from ocean moves into estuary along the bottom
    • Called positive estuary
  • Negative estuary  lose more water through evaporation than the river is able to replace
    • Low in productivity (nutrient poor)
slide9

Salt-wedge estuary

    • In mouths of rivers flowing into saltwater
  • Well-mixed estuary
    • River flow is low and tidal currents play major role in water circulation
slide10

Partially mixed estuary

    • Have strong surface flow of freshwater and strong influx of seawater
  • Temperature
    • Changes rapidly with air temperature changes
    • Estuaries are heated by the sun
estuarine productivity
Estuarine Productivity
  • High because of freshwater and saltwater mixing
  • Silt and clay deposits absorb any excess nutrients from surrounding water
    • Release back into water when nutrients are in short supply
  • Filter feeders remove more phytoplankton
    • Excess phytoplankton eliminated as pseudofeces
      • Large, semisolid particles
life in an estuary
Life in an Estuary
  • Fewer species
    • Less competition for food and space
  • Feed on a variety of foods
slide13

Maintaining osmotic balance

    • Have body fluids with same concentration of salts as seawater
      • Isosmotic to surrounding water
      • Have tissues and cells that tolerate dilution (osmoconformers) or maintain optimal salt concentration in their tissues (osmoregulators)
estuarine communities
Estuarine Communities
  • Many are euryhaline species
    • Can tolerate a broad salinity range
  • Oyster reefs  oysters growing on the shells of previous generations
  • Mud flats  contain rich deposits of organic material with small inorganic sediment grains
slide15

Seagrass meadows  extract nutrients from sediments

  • Salt marsh community
    • Temperate and subarctic regions
    • Low and high marsh regions
  • Mangrove communities
    • Tropical regions
    • Little wave action
      • Sediments accumulate that lack oxygen
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