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Reef Builders

Chapter 14 Part 2 Coral Reefs Other Reef Builders Conditions for Reef Growth Coral Reproduction Kinds of Reefs. Reef Builders. Hermatypic corals Coralline algae ( Porolithon sp., Lithothamnion sp.) Halimeda sp. Sponges Foraminifera Stromatolites. Coralline Algae.

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Reef Builders

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  1. Chapter 14Part 2Coral ReefsOther Reef BuildersConditions for Reef GrowthCoral ReproductionKinds of Reefs

  2. Reef Builders • Hermatypic corals • Coralline algae (Porolithon sp., Lithothamnion sp.) • Halimeda sp. • Sponges • Foraminifera • Stromatolites

  3. Coralline Algae • Porolithon sp., Lithothamnion sp. • Red algae that deposit CaCO3 • Hold reef together – keep it from washing away • Algal ridge on outer edge of many reefs – protects reef from wave action • Grow over and cement sediment that settle on corals

  4. Halimeda sp. • Calcareous green alga • Deposits CaCO3 in tissues for support and to deter predators • Remnants of Halimeda accumulate on reefs and can be bound by encrusting organisms • Microcosm of diversity www.nceas.ucsb.edu www.turtles.org

  5. More Halimeda

  6. Sponges • Bind sediments into place www.johneasley.com

  7. Foraminifera • Eukaryotic protists • CaCO3 shells • Benthic, but a few are planktonic • Some have endosymbiotic algae • Bioindicator www.proprofs.com www.wikipedia.com

  8. Stromatolites • Cycling of microbial communities (cyanobacteria) and sediment • 3.5 billion years old (Earth is 4.5 billion yrs old!) • Not common today – Exuma, Bahamas • Rich source of fossil information www.flickriver.com www.stromatolite.info

  9. Highbourne CayExumas, Bahamas

  10. Conditions for Reef Growth • Hard bottom • Shallow water (< 50 m) with bright sunlight • Clear water • Warm water (> 20°C)

  11. Coral Reproduction • Sexually • Egg + Sperm = Planula • Mostly hermaphroditic • Self fertilization (egg fertilized before released) • Broadcast spawners • What are advantages to mass spawning? G.Spencer Coral Planula

  12. Coral Spawning NOAA video BBC video

  13. Coral Reproduction • Asexually • Fragmentation • Budding • Fission (esp. Fungiidae) Budding www.wikipedia.com

  14. The distribution of coral reef communities p. 304

  15. Bioerosion • Erosion caused by living organisms • Who causes bioerosion? www.coral.org fw.dpnr.gov.vi

  16. Bioerosion

  17. Bioerosion • Epilithic organisms • Remain at surface of the calcareous substrate, where they rasp, scrape, and/or etch the surface. • The majority of damage occurs during algal grazing. • Browsers consume plant material above the substrate • Grazers consume plant material down to, and sometimes below, the surface of the substrate. • Grazers often consume quantities of coral skeleton as well as the invertebrates associated with it and inflict much more damage than browsers. Neither grazers nor browsers usually have a great influence on strength of the greater coral structure (Kleemann 2001)

  18. Bioerosion • Endolithic organisms • Beneath the surface of the coral skeleton. • Bore for food or shelter. • Majority are suspension feeders • Large borers, in particular polychaetes, are important in oxygenating the interior of coral structures to support smaller organisms. • Internal bioeroding species degrade calcareous materials to fine textures • External bioeroders generally erode to much coarser textures (Kleemann 2001)

  19. Reef GrazersGrey angelfish and Blue tangs

  20. Coral Reefs and Zonation3 main categories of reefs 1. Fringing – close to shore, high nutrients, high turbidity 2. Barrier – farther from shore, usually a lagoon between the reef and the shore 3. Atoll - Circular reef with central lagoon and possibly small islands formed on the reef.

  21. Types of Coral Reefs: Fringing Reefs • Simplest and most common • Rocky shorelines provide the best conditions for fringing reefs

  22. Upward growth of reef flats is limited by the tides. Figure 14.16

  23. Barrier Reefs • Distinction between barrier and fringing reefs sometimes unclear • Occur farther offshore • Presence of lagoons

  24. Lady Musgrave Island Great Barrier Reef Australia-trips.info

  25. Spur and Groove formations • Debate about what causes it • Wind, waves, or both involved • Develop primarily on reef slopes that are exposed to strong winds

  26. Atolls • Occur mostly in the Indo-West Pacific region • Practically no land around (no silt, little FW runoff) • Spectacular coral growth and great water clarity Atoll in Fiji

  27. Atoll Formation

  28. Typical Atoll Structure

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