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Coral Reefs and Lagoons

Coral Reefs and Lagoons. Part II Section 5. Reef Growth to Erosion. What is a coral? Healthy corals accumulate CaCO 3 at rate of 3-15 meters in 1000 years. 3 parts of erosion (1 st ). Predation Crown-of-thorns starfish ( Acanthaster planci ): coral predator in Indo-Pacific Reefs

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Coral Reefs and Lagoons

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  1. Coral Reefs and Lagoons Part II Section 5

  2. Reef Growth to Erosion • What is a coral? • Healthy corals accumulate CaCO3 at rate of 3-15 meters in 1000 years

  3. 3 parts of erosion (1st) • Predation • Crown-of-thorns starfish (Acanthasterplanci): coral predator in Indo-Pacific Reefs • Time lag = cause/effect (max. # of predators as coral level falls) • Removal of the starfish Click video

  4. 3 parts of erosion (2nd) • Storm Damage • Hurricanes or tropical storms • Physical breakage of corals • Abrasive sediments • Hurricane Hattie (1961 – Cat 5) destroyed 43 km of the British Honduras barrier reef • Recovery – 25 to 100 years

  5. 3 parts of erosion (3rd) • Exposure to air • Corals dry out • Overheat

  6. Impact of Erosion • Reef erosion = shores/coastal properties are exposed to damages from waves • Artificial reefs: human-made structures = concrete/stone blocks, sacks filled with sand or shipwrecks (sunken ships) • Colonized by algae, corals and fish • Used as submerged breakwater • Dissipate wave energy Click

  7. Artificial Reefs • Prevents erosion of land • Anchorage/protection for harbors • New habitats • Increase fishing areas • Tourism – snorkeling/diving

  8. Shipwrecks (Artificial Reef) • USS Oriskany (2006)

  9. History of Reefs • Geomorphology – study of landforms and processes involved in shaping them

  10. History: Drilling and Carbon Dating • Shows growth and geological history of reef • Carbon Dating – age of coral sample • As corals grow, carbon (from carbon dioxide) is deposited in their skeleton as CaCO3 • 14C carbon slowly decays to 12C • Proportion of 14C to 12C estimates age of coral • Can estimate age up to 50,000 years old

  11. History: Drilling and Carbon Dating • Deep drilling – cores of material to identify corals and estimate growth rate • Have ‘bands’ just like tree rings (give age) • Evidence of growth rate due to environmental conditions like temperature or nutrient availability

  12. Growth of coral • Growth up to 20m deep • Fossil corals found at 1200 m is evidence of subsidence (caving in and sinking of land area) • New coral grow on top of old as reef gradually sinks • Fossil corals found above sea level • Evidence of changes in sea level • Mexico – sea level changes between ice ages

  13. Homework! • Access this link: • http://oceanservice.noaa.gov/education/tutorial_corals/ • Answer Questions passed out to you. • Due Monday, April 8th • Read Marine Biology book pages 10-11 • Answer question 1 AND write bolded words with definitions!

  14. Additional Helpful Links • Climate Close-up (paleoclimatology) • Coral Reefs

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