Coral Reefs and Lagoons Part I Section 5
What are corals? • 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
Darwin-Dana-Daly Theory 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 of coral atoll formation 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 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
Atoll Formation Fringing reef can take 10,000 years to form Atolls up to 30 my Coral – tan and purple
Evidence • 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!
Physiology of Coral • Darwin (1842) produced 1st map of distribution of corals • 3 main types: • Fringing barrier reefs, barrier reefs, atolls
Distribution of Corals • 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
Coral, Zooxanthellae and Fish • http://m.youtube.com/#/watch?feature=youtu.be&v=35ilnGM9EnU&desktop_uri=%2Fwatch%3Fv%3D35ilnGM9EnU%26feature%3Dyoutu.be
Boundary for 20⁰C Isotherms What’s going on here?
Coral Benefits • 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 Beauty • Coral Gardens Fiji (Pacific Ocean) • Egypt (Red Sea) • Baja
Homework! • 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!!!!!