Coral Reefs 1

Coral Reefs

Oasis of the Sea

Coral Reefs 2

Coral Reefs Why are coral reefs

unique?

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Coral Types Hermatypic Ahermatypic Both groups

belong to the phylum Cnidaria

Coral Reefs 4

Coral Structure & Anatomy

Coral Reefs 5

Coral Reproduction

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Coral Nutrition Zooxanthellae provide

nourishment for the coral through photosynthesis Polyps eat and are

voracious predators on zooplankton

Coral Reefs 7

Other Reef Builders Corals do not build a reef alone

Coralline algae produces a skeleton of calcium carbonate that grows in hard sheets on the surface of the reef

Coral Reefs 8

Temperature All reefs are bounded by the 20 C isotherm Optimal reef development occurs at 23-25

C and up to 36-40 C Water temperature that is too warm will

cause coral bleaching The zooxanthellae is expelled from the coral

El Nino events cause massive bleaching in some areas (1997-98)

Conditions Needed For Reef Growth

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Coral Reefs 10

Light Zooxanthellae dependent corals do not develop in

water deeper than 50-70 meters This limitation occurs due to photosynthetic

requirements

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Salinity and Sedimentation Corals are intolerant of salinities

ranging outside of 32-35 ppt Human activities; dredging, mining,

logging, and construction increase the amount of sediment and freshwater runoff Sedimentation clogs feeding mechanism

and reduces the penetration of sunlight

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Wave Action Usually not a

problem due to hard coral exoskeletons

Benefits: renews oxygen, removes sediment, brings in new plankton

Reefs cannot tolerate extended periods of exposure to air

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Fringing Reefs

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Barrier Reefs

Atoll Reefs

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Coral Reef Ecology Coral reefs are easily the richest and most

diverse of all the oceans ecosystems How do these animals interact with each other, what

role do they play in the ecosystem? Reefs are found in areas that are usually poor in

nutrients, lack phytoplankton and other means of primary production

The question is how do these habitats thrive in these nutrient poor waters?

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Nutrient Cycling

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Competition Space is a limiting

resource Sessile animals compete

for space in interesting ways Fast growers shade out

their neighbors Some use mesentery

filaments or sweeper tentacles to sting neighbors

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Predation and Grazing Predation

Grazing Grazers are very

important to the ecosystem since they help keep the algae in check