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Coral Reefs and Lagoons
Part ISection 5
Invertebrate marine animal A polyp that begins to form an exoskeleton
◦ CO2 & Ca in the water to make calcium carbonate (CaCO3) aka limestone
Sessile – immobile Form colonies
What are corals?
Coral atolls 1st proposed by
Charles Darwin◦ HMS Beagle (Nov
1835 – Apr 1836) Supported and
modified by 2 geologists◦ James Daly◦ Reginald Dana
Darwin-Dana-Daly Theory
1. Oceanic volcano emerges from sea surface and forms an island◦ Colonized by reef-building corals
Darwin-Dana-Daly theory of coral atoll formation
2. Growth of corals forms a fringing reef around the island◦ Fringing reef – coral structure attached to the
mainland or continental islands Island begins to sink slowly Coral growth continues
Darwin-Dana-Daly theory of coral atoll formation
Fringing Reef
3. Island continues to sink Barrier reef forms with lagoon around reef
and island◦ Barrier reef - reef separated from a mainland or
island shore by a deep channel or lagoon
Darwin-Dana-Daly theory of coral atoll formation
4. Island eventually disappears below sea surface
Atoll - consists of a ring of small islands Shallow lagoon in center
Darwin-Dana-Daly theory of coral atoll formation
Maldives Atoll
Atoll Formation Fringing reef can take 10,000 years to form
Atolls up to 30 my
Coral – tan and purple
Data from deep drilling on coral atolls◦ Bikini Atoll (Pacific Ocean)◦ As depth of corals increased, age of corals also
increased◦ Fossil corals dated 50 myo and found 1200 m
deep Grown on underlying volcanic rock
◦ Shallow corals found at deep depths!
Evidence
Darwin (1842) produced 1st map of distribution of corals
3 main types:◦ Fringing barrier reefs, barrier reefs, atolls
Physiology of Coral
Conditions required:◦ Temperature range =16⁰C – 35 ⁰C
Optimum range = 23 ⁰C - 25 ⁰C◦ Water clarity
Clear water (less turbid) without silt Silt reduces light penetration which inhibits photosynthesis of
symbiotic zooxanthellae in coral tissues (90% nutrients provided) Depth – rapid growth occurs within 20 m from surface
◦ Salinity◦ Substrate – surface on which plant/animals live
Basaltic rocks of seamounts
Distribution of Corals
http://m.youtube.com/#/watch?feature=youtu.be&v=35ilnGM9EnU&desktop_uri=%2Fwatch%3Fv%3D35ilnGM9EnU%26feature%3Dyoutu.be
Coral, Zooxanthellae and Fish
Boundary for 20⁰C Isotherms
What’s going on here?
Shoreline protection from erosion - ◦ Dissipates/absorbs energy of waves
Benefits include protection of◦ Coastal properties◦ Ecosystems◦ Costs to provide breakwaters – constructed
structures for protection from erosion◦ Anchorage of boats
Coral Benefits
Coral Gardens Fiji (Pacific Ocean) Egypt (Red Sea) Baja
Coral Beauty
Due Friday! Read Marine Biology book pages 10-1
◦ Answer question 1 AND write bolded words with definitions!
◦ Dropbox it in complete sentence(s) Your NEW Oceanography textbooks are
in!!!!!
Homework!