An Introduction to Coral Reefs

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An Introduction to Coral Reefs
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What is coral?

• Its a living organism!
• It is an invertebrate
• 2 different types
• Reef Building Hermatypic
• Solitary Ahermatypic
• Coral is cousins to jellyfish and anemones
  (Cnidarians)
• Today we will talk mainly about reef building
  coral

Sun Coral Polyps
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Where Can You Find Coral Reefs?

• Coral is found all over the world
• Tropical
• Temperate
• Polar
• Only tropical corals build reefs

Coral reefs around the world
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Coral Builds Reefs?

• The animal portion of the reef is called a polyp
• The polyp absorbs calcium carbonate out of the
  water
• The calcium carbonate is used to build the reef

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Reefs Corals Build

• Corals can build three types of reefs
• Fringing grows close to shore
• Barrier also grows close to shore but has a
  lagoon separating it from the shore
• Atoll a ring of coral that surrounds a lagoon,
  often grows on a submerged mountain or volcano

http//www.nos.noaa.gov/education/kits/ corals/med
ia/coral04a_240.jpg
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Coral are Cnidarians

• Soft bodied
• Carnivorous
• Stinging tentacles arranged in a circle around
  their mouth
• Body symmetry
• Specialized tissues

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Cnidarians

• Usually two life stages
• Polyp
• Medusa
• Gastrovascular cavity
• Food is broken down here but digested
  intracellularly

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Cnidarians

• Respiration and waste removal takes place through
  body walls
• Nerve net
• Some have a hydrostatic skeleton
• Some move through jet propulsion

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Anatomy of Coral

• The coral polyps build a calcium carbonate cup
  called a corallite to live in
• Coral has stinging cells called nematocysts

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Stinging Cells

• Nematocysts help coral catch food
• They also help protect the coral
• When the cell is stimulated, it releases a sharp
  barb
• The barb will fire and catch the food and bring
  it back towards the mouth

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Coral and Zooxanthella

• Symbiotic relationship
• Zooxanthella is an algae that lives in the skin
  of coral
• Coral provides protection
• Zooxanthella provides food and color!

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Coral is Picky

• Very specific habitats
• Temperature 73-75?F
• Depth Less than 80 ft to 230 feet
• Salinity Normal salt levels (35ppt)
• Light Zooxanthellae need light to survive
• Sedimentation Being covered with silt interferes
  with photosynthesis
• Desiccation being exposed to air. The corals
  will die if exposed too long

• Coral likes areas with lots of waves
• They are strong enough to withstand the pressure
• Freshwater means more food
• Waves remove silt
• New water brings more oxygen

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Asexual Reproduction

• To reproduce coral can reproduce asexually or
  sexually
• Asexual reproduction in corals is called budding
• A baby polyp will begin growing off the adult
• When it is ready it will detach and live on its
  own
• This can not start new colonies, only help the
  old colony grow bigger

This is a hydra (cousin to coral) with two buds.
One bud (on the right) is older than the other.
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Coral Reproduction

• Sexual reproduction is called spawning
• External fertilization
• It can start new colonies
• Sperm and eggs are released into the water column
• The fertilized egg is then called a planula
• The planula swims until it finds a good place to
  live

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A New Home

• Corals now have a choice of where to live
• Corals are very sensitive and are rapidly dying
• People are trying to help by creating artificial
  reefs

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Arguments for Artificial Reefs

• It can help build or rebuild a reef
• It will increase fish populations by making new
  habitats

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Arguments Against Artificial Reefs

• Moveable
• Chemical leaking and leaching into the ocean
• It does not increase fish populations but rather
  moves them to one location away from their
  natural habitat which makes them easier to catch

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Reefs in North Carolina

• North Carolina has reefs too!
• They similar to tropical reefs
• Reef fish swept up on the Gulf Stream live here
  until winter
• River beds that were covered when sea levels rose
• Also made up of
• Low rock ridges
• Outcroppings
• Coral patches
• Ship wrecks