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CORAL REEFS

CORAL REEFS. MARINE BOTANY FALL 2009. WHERE DO CORAL REEFS OCCUR?. Tropical waters where temperatures remain above 22 0 C. 30 0 N and S of the equator. CORAL REEFS = TROPICAL RAINFORESTS?. RICHNESS COMPLEXITY BEAUTIFUL. CORAL REEFS. Made up of vast amounts of calcium carbonate.

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CORAL REEFS

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  1. CORAL REEFS MARINE BOTANY FALL 2009

  2. WHERE DO CORAL REEFS OCCUR? • Tropical waters where temperatures remain above 220C. • 300N and S of the equator.

  3. CORAL REEFS = TROPICAL RAINFORESTS? • RICHNESS • COMPLEXITY • BEAUTIFUL

  4. CORAL REEFS • Made up of vast amounts of calcium carbonate. • Reef building organisms are corals (Hermatypic). • Corals are Cnidarians. • Colonies of individual polyps.

  5. CORALS • Polyps-sessile sac like-stages with mouth and tentacles on top. • Polyps are connected by a thin sheet of tissue. • Mesenterial filaments-secrete digestive enzymes.

  6. SYMBIOSIS WITH ZOOXANTHELLAE • Algae receive protection and nutrients (carbon dioxide, nitrogen and phosphorus) • Algae supply amino acids, fatty acids, and sugars to the corals.

  7. CORAL BLEACHING • Corals can expel their zooxanthellae losing their normal color. • What causes bleaching? -- high water temp -- exposure to UV radiation -- prolonged shading

  8. TYPES OF CORAL REEFS • FRINGING REEFS • BARRIER REEFS • ATOLLS

  9. FRINGING REEFS • Simplest and most common kind of reef. • Border the land. • Grow in a narrow band or fringe along the shore.

  10. BARRIER REEFS • Separated from the land by a channel of deep water. • Usually 100 km/more from the shore.

  11. ATOLLS • An atoll is a ring of reef surrounding a central lagoon.

  12. REEF TRANSITION

  13. REEF ALGAE • Symbiotic algae • Turf algae – grow on coral skeletons, larger algae and seagrasses. • Sheet type-heterotrichous filaments. • Encrusting forms. • Calcareous erect.

  14. ALGAL ADAPTATIONS TO REDUCE SUSCEPTIBILITY TO HERBIVORES • Avoid the herbivores by growing in size. • Resistant coverings present in many forms. • Chemical defenses – caulerpin (Caulerpa), polyphenols (brown algae), halogenated compounds.

  15. DIVERSITY IN REEFS? • SPECIALIZATION HYPOTHESIS • DISTURBANCE HYPOTHESIS

  16. NATURAL STRESSES NATURAL STRESSES ----SHORT-TERM ---LONG-TERM (DISRUPTIVE) egs: massive sedimentation episodes, population explosions/losses, storms, and typhoons

  17. NATURAL STRESSESHURRICANES • “Head” or “brain” corals (Montastraeaannularis and Diploriastrigosa) are less susceptible to wave damage than branching ones (Acropora palmata and A. cervicornis).

  18. NATURAL STRESSES-GLOBAL WARMING • Global climate change- such as increased concentrations of carbon dioxide and other greenhouse gases, are disrupting the balance of the ocean. Warming trends can elevate seawater temperatures making the conditions unfit for the survival of corals.

  19. NATURAL STRESSES • Increased Sea-Surface temperatures • Coral Bleaching

  20. NATURAL STRESSESLOW TIDE CONDITIONS • Coral heads are exposed • UV radiation---coral bleaching

  21. NATURAL STRESSESDISEASES • Biotic stress factors --bacteria, fungi, protozoa and possibly viruses. • Abiotic stress factors—physical and chemical changes—include increased sea-surface temperatures, ultraviolet radiation, and nutrient input or other pollutants. • White-band disease, Black-band disease, and Aspergillosis.

  22. NATURAL STRESSESPREDATION • Numerous species, including parrotfish, polychaetes, starfish, barnacles, crabs and gastropods, prey on coral polyps, destroying the substrate in the process and preventing other corals from settling.

  23. ANTHROPOGENIC STRESSESWASTES DUE TO HUMAN ACTIVITIES • Discharging wastes--can result from dredging and shoreline modifications, coastal development activities, agricultural and deforestation activities, and sewage treatment plant operations.

  24. ANTHROPOGENIC STRESSESFISHING • Deep water-trawling-involves dragging a fishing net along the sea bottom. • Cyanide fishing--involves spraying or dumping cyanide onto reefs to stun and capture live fish, also kills coral polyps, and degrades the reef habitat.

  25. ANTHROPOGENIC STRESSESMARINE POLLUTION • Leaking fuels • Anti-fouling paints and coatings, and other chemicals can leach into the water-- affecting corals and other species. • Petroleum spills

  26. ANTHROPOGENIC STRESSESCORAL MINING • Coral is collected for coral curios and jewelry. Sand and limestone from coral reefs are made into cement for new buildings. Coral pieces are also removed for use as bricks and road-fill.

  27. RESTORATION OF REEFS • NGOs and government • www.coralreef.org • 691 organizations are listed (450 are NGOs) • 1998-US Coral Reef Task Force was established. $100 million. Objectives: mapping of reefs, establishing marine protected areas, and production of educational materials and training workshops.

  28. WHAT CAN WE DO TO SUSTAIN CORAL REEFS? • Laws need to be enforced • No-take reserves • Building artificial reefs (in-situ/transplanted) • Focus on prevention and not just restoration • Promote responsible human behavior

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