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Coral Reef Formations

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Coral Organisms

•Corals are made up of individual polyps

•Polyps form colonies

•Hermatypic corals build reefs

•Polyps secrete a calcium carbonate

skeleton

Zooxanthellae

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Coral Organisms

•Cnidarians

•Nematocysts

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Photosynthesis

Fixed carbon

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Branching versus Boulder Corals

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Reef formation

• Fringing Reef • Barrier Reef 

• Patch Reef 

•  Apron Reef • Bank Reef 

• Ribbon Reef 

•  Atoll Reef • Table Reef 

Largest biological

constructions on earth!

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Reef formation

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Fringing Reef 

-a reef that is directly attached to a shore or

borders it with an intervening shallow channel or

lagoon.

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Barrier Reef 

- a reef separated from a mainland or island

shore by a deep lagoon

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Patch Reef 

- an isolated, often circular reef, usually within a lagoon or embayment.

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Apron Reef 

- a short reef resembling a fringing reef, but more sloped; extending out

and downward from a point or peninsular shore.

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Bank Reef 

- a linear or semi-circular shaped-outline, larger than a patch reef.

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Ribbon Reef 

- a long, narrow, somewhat winding reef, usually associated with an

atoll lagoon.

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Atoll Reef 

- a more or less circular or continuous barrier reef extending all the way

around a lagoon without a central island.

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Table Reef 

-an isolated reef, approaching an atoll type, but without a lagoon.

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Island Reef Formation

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Reef Zonation

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Reef morphology

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Spur and Groove formation

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Coral Ecosystems

•Oligotrophic systems

•Low nutrients lead to symbioses

•Important nurseries

•

Protection from predation

Highest biodiversity of any

ocean ecosystem!!!

http://www.youtube.com/watch?v=5d3qie3jbHk

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Threats to Corals

•Bleaching

•Stressed corals expel zooxanthellae

•Corals already live at their thermal maximum

Predictions for temperature

increases are between 2 and11.5o F!!!

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Threats to Corals

•Sea Level Rise

•Light attenuates with depthPredictions for sea level rise

are between 7 and 23inches!!!

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Threats to Corals

•Overgrowth by macroalgae

•Increased nutrients

•Overfishing of herbivorous fish

•Dieoff of sea urchins

http://www.youtube.com/watch?v=cbN161yBBGA

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Phase shifts Coral dominated

reef 

 Algal

overgrowth

 Algal

dominance

-persistent change in two

or more variables

describing a state ofsomething

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Branching versus Boulder Corals

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Threats to Corals

•Hurricanes•Branching Corals

•Shallow-water corals

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Sea Level Rise

•Why would corals be good indicators of past sea level

rise and fall?