I Coral Reefs C Components Dynamics Corals important

I. Coral Reefs C. 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

Fig. 15 -8

I. Coral Reefs D. Structure • • • 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? ) Fig. 15 -12

I. Coral Reefs D. Structure Fig. 15 -12

I. Coral Reefs E. Types 1. 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

I. Coral Reefs E. Types 2. 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

I. Coral Reefs E. Types 3. Atoll • • Fig. 15 -10 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

I. Coral Reefs E. Types 3. Atolls • • How do atolls form? Why do they occur in rings?

Fig. 15 -11

II. 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? A. Trophic Structure 1. Nutrient cycling • Within corals, tight relationship between polyps and zooxanthellae

II. Coral Reef Ecology A. Trophic Structure 1. 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

II. Coral Reef Ecology A. Trophic Structure 2. Nitrogen fixation • • • 3. 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

II. Coral Reef Ecology B. Competition • Limited resources include space and light 1) Fast-growing corals may overgrow or shade slowergrowing species

II. Coral Reef Ecology B. Competition • Limited resources include space and light 2) 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

II. Coral Reef Ecology B. Competition • Limited resources include space and light 3) Soft corals may release toxins that harm hard corals • Ecological role filled by sponges on Caribbean reefs (fewer species of corals than in Pacific)

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

II. Coral Reef Ecology D. 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

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

Fig. 9 -1

III. 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

III. Annelida A. 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

Fig. 9 -21

III. Annelida A. • 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 Suspension feeders • • • Active Passive • Solitary • Colonial Reproduction Fig. 9 -10 Pomatoceros lamarckii Haliotis asinina Wikipedia

III. Annelida A. • 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 • Fig. 9 -23 • Deposit feeders • • • Nonselective Suspension feeders • • • Often well-developed eyes and sense organs, jaws Active Passive • Solitary • Colonial Reproduction niwa. co. nz

tolweb. org IV. 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