Coral reefs


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Coral reefs

  1. 1. Chapter 9 Coral Reefs Coral reefs are living structures that provide homes and attachment sites for countless marine organisms in shallow tropical oceans.
  2. 2. Coral Reefs Anatomy and Growth  Coral reefs are created by many species of colonial cnidarians.  These anemone-like polyps produce a CaCO3 skeleton in a great variety of sizes and shapes.
  3. 3. Coral Reefs Anatomy and Growth © Fig. 9.1 Extended polyps of a coral colony. The numerous light-colored spots on the tentacles are batteries of cnidocytes. Fig. 9.2 Cross-section of a coral polyp and a calcareous corallite skeleton. The living coral tissue forms a thin interconnection, the cenosarc, over the surface of the reef.
  4. 4. Coral Reefs Anatomy and Growth Fig. 9.3 Coral exhibit a large variety of growth forms.
  5. 5. Coral Reefs Anatomy and Growth Fig. 9.4 Parrotfishes, major grazers of coral skeletal material, use their powerful jaws to produce large amounts of carbonate sand on the reef. © Wolfgang Amri/ShutterStock, Inc.
  6. 6. Coral Reefs Coral Distribution  Living coral reefs usually are located: • within 30º latitude of the equator • in water that averages at least 20ºC • on the eastern sides of most continents • within the photic zone at depths of 0-50 meters
  7. 7. Coral Reefs Coral Distribution Fig. 9.5 Distribution of reef-forming corals, by number of genera. Heavy black lines indicate continental barrier reefs. Light blue: <20 genera Medium blue: 20-40 genera Dark blue: > 40 genera
  8. 8. Coral Reefs Coral Ecology  Reef-building corals maintain a mutualistic relationship with a dinoflagellate called zooxanthellae  The alga provides photosynthetic products to the coral to aid in its survival and growth  The alga receives unlimited carbon dioxide and nitrogenous wastes from the coral polyp in a competition-free setting
  9. 9. Coral Reefs Coral Ecology Fig. 9.6 Exchange of materials between zooxanthellae and their coral host.
  10. 10. Coral Reefs Coral Reef Formation  Charles Darwin was the first to suggest that coral reefs are sequential developmental stages in the life cycle of a single reef: • fringing reefs • barrier reefs • atolls
  11. 11. Coral Reefs Fig. 9.7 A satellite view of a portion of the hundreds of atolls that make up the nation of Maldives. Courtesy of NASA Earth Observatory
  12. 12. Coral Reefs Fig. 9.8 The developmental sequence of coral reefs, from young fringing reefs (left), to barrier reefs (center), and finally to atolls (right).
  13. 13. Coral Reefs Coral Reef Formation and Hot Spots Fig. 9.9 Chains of volcanoes along the Hawaiian IslandEmperor Seamount are carried, in a conveyer-belt fashion, north into deeper water by the movement of the Pacific Plate. Each volcano was formed over the “hot spot,” a continuous source of new molten material presently under Hawaii, and is carried to its eventual destruction in the Aleutian Trench. Courtesy of NGDC/NESDIS/NOAA
  14. 14. Coral Reefs Reproduction in Corals  Corals reproduce in a great variety of ways, both asexually and sexually  Most sexually reproducing corals are hermaphroditic spawners
  15. 15. Coral Reefs © Gary Bell/ b Fig. 9.10 Spawning corals. (a) Female brain coral releasing eggs; (b) male mushroom coral releasing sperm. a © Marty Snyderman/Visuals Unlimited
  16. 16. Coral Reefs Fig. 9.11 Micrograph of a planula larva of the coral Pocillopora. © Valerie Hodgson/Visuals Unlimited
  17. 17. Coral Reefs Zonation on Coral Reefs  Wave force, water depth, temperature, salinity, and a host of biological factors vary greatly across a reef  Together they result in both horizontal and vertical zonation of the species that form the reef
  18. 18. Coral Reefs Zonation on Coral Reefs Fig. 9.12 Cross-sectional zonation of a barrier reef.
  19. 19. Coral Reefs Fig. 9.13 Echinometra, a common tropical sea urchin. © Ewen Cameron/ShutterStock, Inc.
  20. 20. Coral Reefs Fig. 9.14 A giant clam, Tridacna, amid mixed corals. Note the blue mantle tissue that is brightly colored due to the presence of innumerable mutualistic zooxanthellae. © Andy Lim/ShutterStock, Inc.
  21. 21. Coral Reefs Fig. 9.15 Variations in coral growth forms: (a) table coral, Acropora; (b) brain coral, Diploria; and (c) staghorn coral, Acropora. a © Andy Lim/ShutterStock, Inc. © Andy Lim/ShutterStock, Inc. Zonation on Coral Reefs © Lawrence Cruciana/ShutterStock, Inc. b c
  22. 22. Coral Reefs Coral Diversity and Catastrophic Mortality  Reefs worldwide are threatened by human activities, succumbing to: • pollution • destructive fishing practices • bleaching • a host of diseases
  23. 23. Coral Reefs b a Courtesy of AIMS/NOAA Courtesy of David Burdick/NOAA Fig. 9.16 The predatory sea star, Acanthaster, and (b) its major predator, the Pacific triton, Charonia.
  24. 24. Coral Reefs Coral Diversity and Catastrophic Mortality. Courtesy of Dr. Phillip Dustan, College of Charleston Fig. 9.17 Black band disease overgrowing a coral head. This star coral, Montastrea, which could be as much as 500 years old, will probably be dead within one year. Courtesy of David Burdick/NOAA Fig. 9.18 Wide-spread bleaching on a Pacific coral reef.
  25. 25. Coral Reef Fishes Fig. 9.19 Some common reef fishes on a tropical Caribbean reef: 1. nurse shark (Ginglymostoma), 2. reef shark (Carcharhinus), 3. barracuda (Sphyraena), 4. surgeonfish (Acanthurus), 5. butterflyfish (Chaetodon), 6. angelfish (Pomacanthus), 7. hawkfish (Amblycirrhitus), 8. grouper (Mycteroperca), 9. moray eel (Gymnothorax), 10. stingray (Dasyatis), 11. grunt (Haemulon), 12. soldierfish (Myripristis), 13. porcupinefish (Diodon). Angelfish photo from Joyce and Frank Burek/NOAA; all other photos from John Morrissey
  26. 26. Coral Reef Fishes Coral Reef Sharks and Rays  Reefs worldwide are dominated by: • benthic orectolobid sharks (nurses, wobbegongs, and bamboosharks) • and more typical pelagic carcharhinid sharks (blacktips, whitetips, tigers, and reef sharks)
  27. 27. Coral Reef Fishes Coral Reef Sharks and Rays Fig. 9.20 Dermal flaps around the mouth of a wobbegong, a benthic reef shark.
  28. 28. Coral Reef Fishes Coral Reef Teleosts  About 50% of all living vertebrates are teleost fishes, and many of these fishes inhabit coral reefs. Courtesy of NOAA Fig. 9.21 Numerous species of teleost fishes are associated with coral reefs.
  29. 29. Coral Reef Fishes Coral Reef Teleosts  The great diversity of teleost fishes have evolved numerous symbiotic relationships such as inquilinism and cleaning behaviors.
  30. 30. Coral Reef Fishes Fig. 9.22 Two remoras, Echeneis, with modified dorsal fins accompanying a nurse shark, Ginglymostoma.
  31. 31. Coral Reef Fishes Coral Reef Teleosts © Russell Swain/ShutterStock, Inc. Fig. 9.24 A clownfish, Amphiprion, nestled within the protective tentacles of its host anemone. Fig. 9.23 Shrimpfish, Aeoliscus, seeking shelter amid the spines of a sea urchin.
  32. 32. Coral Reef Fishes Coral Reef Teleosts Courtesy of Dr. Anthony R. Picciolo, NOAA NODC Fig. 9.25 A nearly transparent cleaner shrimp, Periclimenes, on a Caribbean sponge. © Kelpfish/ShutterStock, Inc. Fig. 9.26 Neon gobies, Elacatinus, clean the head of a large green moray, Gymnothorax.
  33. 33. Coral Reef Fishes Coral Reef Teleosts  The brightly colored patterns of coral reef fishes illustrate the advertisement, disguise, and concealment roles of brilliant coloration in a coral reef environment.
  34. 34. Coral Reef Fishes Coral Reef Teleosts © Frank Boellmann/ShutterStock, Inc. © Rene Frederic/age fotostock Fig. 9.27 A well-camouflaged scorpionfish, Scorpaena (left), with magnified chromatophores from a section of skin (right).
  35. 35. Coral Reef Fishes Coral Reef Teleosts © Lawrence Cruciana/ShutterStock, Inc. © cbpix/ShutterStock, Inc. Fig. 9.28 Disruptive coloration patterns of two species of butterflyfishes, Chaetodon.
  36. 36. Coral Reef Fishes Fig. 9.29 A cleaner wrasse, Labroides (above), and its mimic, Aspidontus (below).
  37. 37. Coral Reef Fishes Coral Reef Teleosts  About one fourth of all reef-fish species place sticky benthic eggs in a guarded nest on the reef.
  38. 38. Coral Reef Fishes Coral Reef Teleosts © David Fleetham/Alamy Images Fig. 9.31 A sergeant major (Abudefduf) guards its purple egg mass in the Caribbean Sea. Courtesy of Dr. Michael P. Robinson Fig. 9.30 Two bicolor damselfish mate inside a discarded PVC pipe on a Caribbean reef.
  39. 39. Coral Reef Fishes Coral Reef Teleosts  Most reef teleosts are pelagic spawners.  As many as 30 or more species at any given time will assemble around a coral promontory to broadcast as many as 50,000 eggs apiece into the water column.  After fertilization, these pelagic eggs drift away from the reef and disperse for one day to a year or more.
  40. 40. Coral Reef Fishes Coral Reef Teleosts Fig. 9.32 Dog snappers, Lutjanus jocu, return to the reef after a spawning run in the water column off Belize. © Doug Perrine/
  41. 41. Coral Reef Fishes Fig. 9.33 Locations of U.S. National Marine Sanctuaries and National Estuarine Research Reserves.
  42. 42. Coral Reef Fishes Coral Reef Teleosts  The great diversity of reef fishes results in sexual systems that range from species with separate sexes to simultaneous and sequential hermaphrodites. © WaterFrame/Alamy Images Fig. 9.34 Clasping hamlets above a reef.
  43. 43. Coral Reef Fishes Coral Reef Teleosts Courtesy of Dr. Michael P. Robinson Courtesy of Dr. Michael P. Robinson Fig. 9.35 Male and female “bluehead” wrasses in their initial yellow phase. Fig. 9.36 Terminal-phase bluehead male surveying his territory.
  44. 44. Coral Reef Fishes Fig. 9.37 Relative reproductive success experienced by males and females of protandrous clownfishes (left) and protogynous wrasses (right).