1. Coral Reefs
Marine Biology Unit #9

2. Introduction Most complex & diverse ecosystem in our oceans
Not only biological, but geological
Spectacular!

3. Coral Polyps Member of Phylum: cnidaria, Class: anthozoa
Related to sea anemones
Most corals are colonial
Few are solitary

4. Soft Corals (ahermatypic)
Non-reef building corals
No hard skeleton
Sea fans

5. Stony Corals (hermatypic)
Reef-building corals
Calcium carbonate skeleton (secreted by polyps)

6. Stony Corals (hermatypic)

7. Colonial Polyps Polyps housed in cups called corallite cups
Polyps connected by mesentery (tissue)
Polyps are clones

8. Zooxanthellae Symbiotic algae residing in polyp tissue
Hermatypic corals
Help deposit calcium carbonate
Provide nourishment for polyps (via photosynthesis)
Give coral coloration

9. Zooxanthellae

10. Coral Reefs Conditions for optimal growth:
Shallow water with plenty of light
Started on hard substrate
Islands, shores
Clean, clear water
Warm water

11. Coral Reefs

12. Reef Formation Three main types of coral reefs: Fringing Barrier
Atolls

13. Fringing Reefs Close to shore (newly formed island; coast of mainland)
Vulnerable to sediments, runoff, human disturbance

14. Fringing Reefs
Rarotonga, Cook Islands
Moorea, Tahiti

15. Barrier Reefs
Reef further from shore
Lagoon between shore and reef

16. Barrier Reefs Back - reef slope (inner slope) is protected
Reef flat may begin to form sand cays
Outer reef crest/slope is where most growth occurs

17. Barrier Reefs Back - reef slope (inner slope) is protected
Reef flat may begin to form sand cays
Outer reef crest/slope is where most growth occurs
Spurs and grooves allow lagoon circulation

18. Barrier Reefs
Great Barrier Reef

19. Atolls Island has receded, leaving only coral “ring”
Often contains islands or sand cays

20. Atolls Majority of atolls occur in the Indo-West Pacific
Many atolls are inhabited

21. Bikini Atoll

22. Bikini Atoll

23. Reef Ecology Nutrients recycled very effeciently
Space is major limiting factor
Competiton
overgrowing
attacking

24. Reef Ecology
Predation on coral
Fish
Butterfly fish
Parrot fish

25. Reef Ecology
Predation on coral
Parrot fish make coral sand

26. Reef Ecology
Predation on coral
Crown-of-thorns (seastar)

27. Reef Ecology
Coral bleaching
Temperature increasing
Acidification

28. Reef Ecology
Symbiotic relationships
Mutualism

29. Reef Ecology
Symbiotic relationships
Commensalism

30. Reef Ecology
Symbiotic relationships
Parasitism