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Coral/algal Reefs II

Coral/algal Reefs II. What forces maintain reef diversity?. Planet Earth video. Ecological functional groups. A larger scale view: reef building process. Atoll structure. Habitat diversity within an atoll. Niche dimensions enhancing reef fish diversity. Defensive tactics Feeding

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Coral/algal Reefs II

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  1. Coral/algal Reefs II What forces maintain reef diversity?

  2. Planet Earth video

  3. Ecological functional groups

  4. A larger scale view: reef building process

  5. Atoll structure

  6. Habitat diversity within an atoll

  7. Niche dimensions enhancing reef fish diversity • Defensive tactics • Feeding • Food type • Food location • Timing of foraging • Life-history and social structure

  8. Physical defenses: Spines of Porcupine fish

  9. Physical defenses: misdirection, Butterfly fish

  10. Territoriality: Pomacentrus

  11. Poisons: Purple trunk fish, lionfish

  12. Feeding: >50% feed on other fish • Variation by size, location, timing

  13. Feeding: coral (Triggerfish)

  14. Feeding: “inverts” by probing (file fish)

  15. Feeding: marine worms (butterfly fish)

  16. Feeding: plankton (purple queen)

  17. Feeding: algae (surgeon fish)

  18. Feeding: other fish/ cleaning symbiosis • Pacific Cleaner Wrasse • Moray Eel • Saber Tooth Blenny

  19. External factors influencing diversity • Proximity to mangrove nurseries • Mumby et al. 2004, Nature 427:533 • Compare fish biomass from reefs near mangroves and where mangroves scarce

  20. How can coral/algal reefs support so many species? • “Bottom-up” hypotheses • High degree of nutrient recycling (symbiotic mutualism) promotes corals • Coral diversity promotes associated species • “Biotic multiplier effect” • “Top-down” hypotheses • Predation rates/disturbance reduce competition • Patchy environments with variable colonization • Priority advantage (inhibition model)

  21. Utilitarian justification for reef conservation • Therapeutic compounds from marine species • Anti-virals from sponges, seagrass • Anti-tumor compounds from tunicate, dogfish, bryozoan, sea hares, cyanobacteria, sponge • Compounds to promote bone grafts from stony corals • Tourism • Food • Impact on global climate, carbon exchange • Models for scientific study

  22. Processes important in reef dynamics – what maintains the reef structure? • Symbiosis (and dissolution of associations) • Competition • Predation and grazing • Disturbance & recovery

  23. Competitive dynamics • Exploitation competition (for light) • Upright, branching corals can shade massive corals • Encrusting algae can spread over corals • Interference competition (for space) • External digestion by some corals • “Sweeper” tentacles for some species • Hierarchy of competitive dominance • Algae easily overgrow most corals • Among corals Pocillopora is nastiest

  24. Dynamics of predation on coral reef species • Coral-feeding fish are present but usually not devastating • Territorial damselfish create safe zones (up to 60% of surface area) • Coral-feeders have their own predators • Starfish, such as “Crown-of-Thorns” can be problematic • Population “outbreaks” can damage living corals

  25. Dynamics of grazing on algal reef species • Urchins are major consumers (e.g., Diadema antillarum) • Grazing by herbivorous fish can be specialized on algae (more impact than fish feeding on corals) • Grazing can suppress competitively dominant algae • Indirect effects can become important

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