What is a coral? Healthy corals accumulate CaCO3 at
rate of 3-15 meters in 1000 years
Reef Growth to Erosion
Predation Crown-of-thorns starfish (Acanthaster planci): coral
predator in Indo-Pacific Reefs Time lag = cause/effect (max. # of predators as coral level
falls) Removal of the starfish
3 parts of erosion (1st)
Click video
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
3 parts of erosion (2nd)
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
Impact of Erosion
Click
Prevents erosion of land Anchorage/protection for harbors New habitats Increase fishing areas Tourism – snorkeling/diving
Artificial Reefs
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
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
History: Drilling and Carbon Dating
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
Growth of coral
Access this link:◦ http://oceanservice.noaa.gov/education/tutorial_c
orals/◦ 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!
Homework!
Climate Close-up (paleoclimatology)
Coral Reefs
Additional Helpful Links