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 Coral abundance & diversity decrease with depth
Fig
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

5. Coral Reefs Types Fringing Fig. 15-10
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

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

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

9. Fig

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 Food webs
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 Diverse lifestyles
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 Diverse lifestyles
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. Nematoda Free living and parasitic forms Cosmopolitan/Ubiquitous
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