Coral Reefs Components & Dynamics Corals important components of reefs

1. Coral Reefs • Components & Dynamics • Corals important components of reefs • Other organisms also contribute • Coralline red algae cement debris together • More important in Pacific than Atlantic • Part of bioerosion process

2. Fig. 15-8

3. Coral Reefs • Structure Fig. 15-12 • Coral abundance & diversity decrease with depth • Competition for light affects growth forms • Upper slope - doming corals • Mid slope - branching corals • Lower slope - plate-like corals (Why?)

4. Coral Reefs • Structure Fig. 15-12

5. Coral Reefs • Types • Fringing • Simplest, most common type of reef • Occur near shore throughout tropics • Form narrow band (fringe) along shoreline • Proximity to land  vulnerability to sedimentation, freshwater runoff, human influence Fig. 15-10

6. Coral Reefs • Types • Barrier • Not always obviously distinct from fringing reefs • Often occur farther from shore (up to 100+ km) • May be sand cays on back reef slope Fig. 15-10

7. Coral Reefs • Types • Atoll • Most common in Indo-West Pacific • Rare in Caribbean, tropical Atlantic • Usually far from land • Little influence from freshwater runoff, sedimentation • Range in size from <1 to 20+ miles in diameter • Often influenced by trade winds • Differences between windward and leeward sides • Windward: Spur-and-groove, distinct algal ridge Fig. 15-10

8. Coral Reefs • Types • Atolls • How do atolls form? • Why do they occur in rings?

9. Fig. 15-11

10. Coral Reef Ecology • Among most productive communities in ocean • Generally occur in areas with low nutrient concentrations, low primary production • How can coral reefs be so productive? • Trophic Structure • Nutrient cycling • Within corals, tight relationship between polyps and zooxanthellae

12. Coral Reef Ecology • Trophic Structure • Nutrient cycling • “Nutrient traps” • Other reef animals also contain symbionts and recycle nutrients within their tissues • Sponges • Nudibranchs • Giant clams • Sea squirts • Waste products also recycled • Some inputs still required

13. Coral Reef Ecology • Trophic Structure • Nitrogen fixation • Primarily by cyanobacteria • Some free living, some symbiotic in sponges • Nitrogen may not limit productivity in coral reefs • Different from most other marine communities • Nitrogen also acquired by • Absorption of dissolved organic matter (DOM) • Predation on zooplankton • Food webs • Base formed by corals and algae (esp. turf algae) • Complex feeding interactions • Diversity from extensive resource partitioning • More niches More species

14. Coral Reef Ecology • Competition • Limited resources include space and light • Fast-growing corals may overgrow or shade slower-growing species

15. Coral Reef Ecology • Competition • Limited resources include space and light • More aggressive corals may attack other corals • Mesenterial filaments used to digest away tissue from competitor/neighbor (video) • Special sweeper tentacles sting adjacent colonies • Slower growers tend to be most aggressive • Faster growers tend to be less aggressive

16. Coral Reef Ecology • Competition • Limited resources include space and light • Soft corals may release toxins that harm hard corals • Ecological role filled by sponges on Caribbean reefs (fewer species of corals than in Pacific)

17. Coral Reef Ecology • Predation • Most coral predators eat portion of coral • Ex: Butterflyfishes, parrotfishes • Doesn’t kill coral; permits regrowth • Predation may limit growth rates of certain fast-growing species • Other coral predators eat entire corals • Ex: Crown-of-Thorns Sea Star • Extrudes stomach, digests coral tissue

18. Coral Reef Ecology • Grazing • Many fishes are herbivorous • Ex: Surgeonfishes, parrotfishes, damselfishes • Invertebrate grazers and microherbivores also important • Ex: Sea urchins, gastropods, crustaceans • Grazing controls populations of seaweeds • Could overgrow corals if not grazed by herbivores • Ex: Seaweeds protected from grazers grew much faster than unprotected seaweeds • Removal of grazers  proliferation of algae

19. Coral Reef Ecology • Mutualism • Numerous mutualistic interactions in reef community • Ex: Corals & zooxanthellae • Ex: Giant clams & zooxanthellae • Ex: Anemones & anemone fishes, crabs, shrimps

20. Fig. 9-1

21. Annelida • Mostly segmented worms • Body composed of repeated segments • Gut runs through body cavity (coelom) • Coelom filled with fluid – hydrostatic skeleton • Longitudinal and radial muscles • Efficient locomotion and burrowing • More than 15,000 species • Cosmopolitan

22. Annelida • Polychaeta (class) • 10,000+ species (mostly marine) • Body segments bear pairs of parapodia • Parapodia used for locomotion, feeding • Often tipped with setae • Closed circulatory system** • Efficient transport of blood, gases • Gas exchange • Small species exchange gases across body wall • Large species have gills for gas exchange • Highly vascularized with capillaries and thin body walls

23. Fig. 9-21

24. Annelida • Polychaeta • Larva = Trochophore • Band of cilia around body; tuft on apex • Same larval stage in Mollusca • Diverse lifestyles • Errant vs. Sedentary • Free-living predators • Often well-developed eyes, sense organs, jaws • Deposit feeders • Nonselective • Selective • Suspension feeders • Active • Passive • Solitary • Colonial • Reproduction Haliotis asinina Wikipedia Pomatoceros lamarckii Fig. 9-10

25. Annelida • Polychaeta • Larva = Trochophore • Band of cilia around body; tuft on apex • Same larval stage in Mollusca • Diverse lifestyles • Errant vs. Sedentary • Errant: Free-living predators • Often well-developed eyes and sense organs, jaws • Deposit feeders • Nonselective • Selective • Suspension feeders • Active • Passive • Solitary • Colonial • Reproduction niwa.co.nz Fig. 9-23

26. tolweb.org • Nematoda • Free living and parasitic forms • Cosmopolitan/Ubiquitous • Mostly in sediments (free living) or hosts (parasitic) • Common in fine muds • Organic rich areas • Described species: 28,000+ (>55% parasitic) • May be up to 500,000 species total! • Extremely abundant!! • Up to hundreds of individuals per ml of sediment • 90,000 in one rotting apple (not marine) • Hydrostatic skeleton • Longitudinal muscles only • Move by whipping back and forth