1. AICE Marine Science Unit 5
Coral Reefs & Lagoons
AICE Marine Science
Unit 5

2. 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

3. Habitat Usually between 30O N & S latitudes Usually in Photic Zone
Clear, warm, tropical, shallow

4. Coral Reef Growth Needs
Lots of light (low to no turbidity)
Depth between 0-20M (to deep = not enough light)
Temperatures averaging 23°-25°C (70°-85°F)
Most coral cannot survive below 16° C
Must have Salinity between 34-37ppt
Substrate is a limiting factor

5. Reef-building Corals (shallow):

6. Reef-building Corals:
Hermatypic Corals = reef-building/shallow
Kingdom Animalia
Phylum Cnidaria
Class Anthozoa
Subclass Zoantharia
Order Scleractinia
Primarily made up of small individual coral polyps
Skeleton made up of calcium carbonate

7. Reef-building Corals:
Have a mutualistic symbiotic relationship with zooxanthellae
Dinoflagellate that lives within their tissues
Corals get energy & O2 & wastes removed
Zooxanthellae gets products for photosynthesis& a “safe” home
Fun Fact: Zooxanthellae is what gives coral its color!

8. Coral Polyps http://youtu.be/wbNeIn3vVKM

9. 3 Coral Reef formations:1
Fringing = Usually closest to shoreline (sometimes called finger reef); most common (like a skirt)
Barrier = Separated from mainland by a lagoon
Atoll = Ring of sand, coral, & land w/ central lagoon; oldest reef formation (sinking volcanic island) 2 3

10. Fringing

11. Barrier

12. Atolls
Bikini Atoll
Belize

13. Darwin-Dana-Daly Theory of Atoll Formation
Oceanic volcano emerges from sea & forms an island
Reef-building corals build & surround island (fringing)
Island sinks & lagoon forms between island & reef (barrier)
Island disappears below sea, leaving ring of small islands w/ lagoon in center (atoll)

14. Darwin-Dana-Daly Theory
Coral atolls
1st proposed by Charles Darwin
HMS Beagle (Nov – Apr 1836)
Supported and modified by 2 geologists
James Daly
Reginald Dana

15. Darwin-Dana-Daly theory of coral atoll formation
1. Oceanic volcano emerges from sea surface and forms an island
Colonized by reef-building corals

16. 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

17. 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

18. 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

19. Atoll Formation Fringing reef can take 10,000 years to form
Atolls up to 30 my
Coral – tan and purple

20. 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!

21. Atoll Formation, an animation:
Thanks for animation NOAA

22. Stop Day 1