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Coral reefs Chapter 9

Coral reefs Chapter 9. What are coral?. Phylum Cnidaria Class Anthozoa Order Scleractinia coral are colonial polyps each polyp is an individual polyps share gastrovascular cavities polyps within a colony are clones. What are coral?.

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Coral reefs Chapter 9

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  1. Coral reefsChapter 9

  2. What are coral? • Phylum Cnidaria • Class Anthozoa • Order Scleractinia • coral are colonial polyps • each polyp is an individual • polyps share gastrovascular cavities • polyps within a colony are clones

  3. What are coral? • Coral build calcium carbonate (CaCO3) external skeletons • Coral grow by adding layers to the skeleton Coral polyp with tissue (left), with mouth at center, and without tissue showing just the skeleton (right)

  4. Where do you find coral reefs? • Between 30° N and 30° S • (but most are even more equatorial)

  5. Where do you find coral reefs? • shallow water (WHY??) • coastal areas (WHY??) • more in the Indo-Pacific, especially atolls (WHY?)

  6. discharged cnidae Cnidae • stinging cells: nematocysts • used in prey capture, may have toxins • set off mechanically (cnidocil) • only used once • stolen by others: “kleptocnidae” • - nudibranchs, flatworms, ctenophores

  7. coral with zooxanthellae (left) and bleached (right) Symbiotic relationships in coral • zooxanthellae – symbiotic dinoflagellates • “bleaching” occurs when zooxanthellae leave the coral tissue • without zooxanthellae, the CaCO3 skeleton shows through the clear coral tissue & coral appear white • many factors cause bleaching, including augmented temperature

  8. Brain coral polyps extended polyps retracted corals are colonial flower coral Examples of corals (close-up)

  9. Types of reefs

  10. Atoll formation • mostly in the Pacific • Darwin described atoll formation NOAA animation of atoll formation

  11. The Society Islands (French Polynesia) Atolls

  12. Coral reef structure

  13. Coral growth and aging patterns • Because of their growth pattern, coral have annual layers analogous to tree rings • These layers can be used to age a coral and to learn about interannual variation in growth • This provides information on past climatic conditions

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