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7.5 - Coral Reefs
7.5 - Coral Reefs
7.5 - Coral Reefs
7.5 - Coral Reefs
7.5 - Coral Reefs
7.5 - Coral Reefs
7.5 - Coral Reefs
7.5 - Coral Reefs
7.5 - Coral Reefs
7.5 - Coral Reefs
7.5 - Coral Reefs
7.5 - Coral Reefs
7.5 - Coral Reefs
7.5 - Coral Reefs
7.5 - Coral Reefs
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7.5 - Coral Reefs


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  • 1. Coral Reefs
  • 2. You should be able to…
    • Describe the conditions required for the development of coral reefs
    • Understand the global distribution of coral reefs that results from this
    • Describe fringing and barrier reefs and atolls
    • Appreciate that coral reefs are under threat from human activity
  • 3. Coral Reef Formation
    • The polyp forms the basis of life on the coral reef.
    • It builds reefs through the production of a calcium carbonate skeleton which it constructs as it grows.
    • Polyp growth is the result of a symbiotic relationship between the polyp and zooxanthellae (algae) which rely on photosynthesis for their growth.
    • The zooxanthellae provide essential nutrients to the polyp to enable growth.
  • 4. Conditions required
    • Temperature: 23-25°C;
    • Water Depth: less than 25m but not exposed to air;
    • Light: for photosynthesis;
    • Salinity required;
    • Clean, clear water, sediment free,
    • Well oxygenated water produced by strong wave action;
  • 5. Global Distribution Global distribution: Tropical seas between Tropics of Cancer and Capricorn. Offshore, on eastern and western continental and island margins. 92% of total found in Indo-Pacific region.
  • 6. Type of Reef
    • Fringing reef – reef that is directly attached to a shore or borders it with an intervening shallow channel or lagoon.
    • Barrier reef – reef separated from a mainland or island shore by a deep lagoon ; see Great Barrier Reef .
    • Atoll reef – a more or less circular or continuous barrier reef extending all the way around a lagoon without a central island; see atoll .
    • From Wikipedia
  • 7. Reef Theories
    • Charles Darwin postulated that fringing reef, barrier reef and atoll development happened through geological time as a result of continued reef growth and volcanic subsidence.
    • James Dwight Dana (a geologist) provided evidence top support Darwin's theory of uplift and subsidence.
  • 8. After Darwin
  • 9. Dana’s Evidence
  • 10. Reginald Daly (20 th Century)
    • An island emerges from the surface of the sea.
    • Sea levels drop significantly during an Ice Age.
    • Horizontal terraces and ledges are cut by erosion during the period of low sea level.
    • As the Ice Age ends the sea level rises.
    • Coral reef growth subsequently takes place on the newly created submerged platforms.
  • 11. Daly in Diagrams
  • 12. The 3D Theory of Coral Development The modern explanation of coral reef development should correctly be called the Darwin/Dana/Daly Theory (The 3D Theory!) of Coral Reef Formation since only the works of these three men taken together can fully explain the characteristics observed on atolls today.
  • 13. Threats to Coral Reefs
  • 14. The Impacts Coral Bleaching Damaged Coral
  • 15. Coral Reef Management
    • What can be done to protect the worlds coral reefs?
    • Why is protecting coral reefs important?
    • Case Study
    • Great Barrier Reef (Australia)
    • Marine Park Website