Coral Reefs
What is a Coral Reef?
• CaCO3 from living things
• Reef builders– Corals– Algae– Sponges– Bryozoans– Shells
Reef Corals (Hermatypic)
• Anthozoans (no medusa stage)• Scleractinian corals = “true” corals• Zooxanthellae
– Symbiotic dinoflagellates• Photosynthesize• Help deposit skeleton
• Most are colonies from founder polyp– Interconnected digestive and nervous
systems
Coral NutritionCoral Nutrition Zooxanthellae Predation on
zooplankton Polyp tentacles Mucus Mesentarial
filaments
Zooxanthellae Predation on
zooplankton Polyp tentacles Mucus Mesentarial
filaments
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Coral ReproductionCoral Reproduction
Asexual
Sexual Some internal Broadcast
spawning
Asexual
Sexual Some internal Broadcast
spawning
Corals in action!Corals in action!
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Coral RestrictionsCoral Restrictions
Light for zooxanthellae (usually best in shallow, clear water)
Warm water (but not too warm!!) - 68-86 F Substrate availability Salinity Sedimentation Pollution and eutrophication
Light for zooxanthellae (usually best in shallow, clear water)
Warm water (but not too warm!!) - 68-86 F Substrate availability Salinity Sedimentation Pollution and eutrophication
Coral Coral BleachingBleaching
Normal ReefNormal Reef
BleachedBleached
Fringing ReefsFringing Reefs
Near shore - more vulnerable to? Reef flat
Wide inner area Shallow - may be exposed
Reef slope Steep outer area Much richer biologically
Near shore - more vulnerable to? Reef flat
Wide inner area Shallow - may be exposed
Reef slope Steep outer area Much richer biologically
Fringing ReefsFringing Reefs
Barrier ReefsBarrier Reefs
Lagoon Separates reef from shore Usually soft-sediment with gentle water
Reef flat May form sand cays (keys)
Reef slopes Back slope and fore slope
Lagoon Separates reef from shore Usually soft-sediment with gentle water
Reef flat May form sand cays (keys)
Reef slopes Back slope and fore slope
Barrier ReefsBarrier Reefs
AtollsAtolls
Ring of reef surrounding central lagoon Indo-West Pacific
Ring of reef surrounding central lagoon Indo-West Pacific
Reef Ecology
Reef Ecology
Nutrient CyclingNutrient Cycling
Symbiotic algae Zooxanthellae Also in sponges, giant clams, others
Animal waste Nitrogen fixation (cyanobacteria,
symbionts) Currents
Symbiotic algae Zooxanthellae Also in sponges, giant clams, others
Animal waste Nitrogen fixation (cyanobacteria,
symbionts) Currents
Eating Coral??Eating Coral??
Eating Coral??Eating Coral??
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Eating Coral??Eating Coral??
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Eating Coral??Eating Coral??
CompetitionCompetition
Sessile animals compete for space and light
Methods: Rapid growth Overgrowth Attack (poisons, stinging, digestions)
Sessile animals compete for space and light
Methods: Rapid growth Overgrowth Attack (poisons, stinging, digestions)
CompetitionCompetition
What about fish?What about fish?
Pre-settlement hypothesis Species present are result of larvae
settlement Competition unimportant
Post-settlement hypothesis Diversity determined by available niches and
competition
Pre-settlement hypothesis Species present are result of larvae
settlement Competition unimportant
Post-settlement hypothesis Diversity determined by available niches and
competition
SymbiosisSymbiosis
What is symbiosis? Do they have to live together?
Obligatory vs. facultative symbiosis Types of symbiosis
Mutualism (+,+) Commensalism (+, 0) Parasitism (+, -)
What is symbiosis? Do they have to live together?
Obligatory vs. facultative symbiosis Types of symbiosis
Mutualism (+,+) Commensalism (+, 0) Parasitism (+, -)
Mutualism: AnemonefishesMutualism: Anemonefishes
Why aren’t they stung?
Fish gain protection and place to brood eggs
Fish drives away potential predators of anemone, may provide nutrients
Why aren’t they stung?
Fish gain protection and place to brood eggs
Fish drives away potential predators of anemone, may provide nutrients
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Mutualism: CleaningMutualism: Cleaning
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Mutualism: CleaningMutualism: Cleaning
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