 “Reef Builders”
 Organisms that secrete the calcium
carbonate skeletons that form the reef
▪ Examples:
 Calcareous Corals
 Coralline Algae

Organisms that produce sediment or live in
the cracks & crevices of the reef
 Examples:
 Encrusting coralline algae
 Fragments of coral
 Foraminifera
 one-celled animals that make shells – for ex: paper shells
 Mollusks
 Echinoderms

Organisms that use the structure of the reef to
live and hide in; don’t affect the structure, but
may eat inhabitants of be eaten by them
 Examples:
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Anemones
Crustaceans
Many Fish
Worms
Red, green, brown algae
Octopuses
Many mollusks

Organisms that destroy by chewing, eroding,
blanketing, or producing acid
 Examples:
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Boring sponges
Coral-eating fish (ex: parrotfish)
Worms
Sea Urchins & Sea Stars
Boring Mollusks
Rapid-growing algae

“Builders”
 Examples:
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Calm Water
Adequate sunlight
Optimum salinity
Clear water
Solid substrate
Adequate nutrients

Actions & Organisms that kill coral and wear
away the reef
 Examples:
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Pounding waves
Moving sand
Smothering sediments (silt)
Freshwater rain
Very low tides
Rising seafloor
Sinking seafloor
Rising or falling water temperature
Runoff from land
Excessive nutrients in water
Pollution
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Agents affecting Reefs Growth