Oasis of the Sea

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Coral Reefs

• Oasis of the Sea

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Coral Reefs

• Why are coral reefs unique?

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Coral Types

• Hermatypic
• Ahermatypic
• Both groups belong to the phylum Cnidaria

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Coral Structure Anatomy
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Coral Reproduction
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Coral Nutrition

• Zooxanthellae provide nourishment for the coral
  through photosynthesis
• Polyps eat and are voracious predators on
  zooplankton

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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

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Conditions Needed For Reef Growth

• 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)

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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
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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