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!