Download An Introduction to Coral Reefs

What is coral?
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It’s a living organism!
It is an invertebrate
2 different types:
 Reef
Building: Hermatypic
 Solitary: Ahermatypic
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Sun Coral Polyps
Coral is cousins to jellyfish and anemones
(Cnidarians)
Today we will talk mainly about reef building
coral
Where Can You Find Coral Reefs?
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Coral is found all over
the world:
 Tropical
 Temperate
 Polar
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Only tropical corals
build reefs
Coral reefs around the world
Coral Builds Reefs?
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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
Reefs Corals Build
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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/media/coral04a_240.jpg
Coral are Cnidarians
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Soft bodied
Carnivorous
Stinging tentacles
arranged in a circle
around their mouth
Body symmetry
Specialized tissues
Cnidarians
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Usually two life
stages:
 Polyp
 Medusa
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Gastrovascular cavity
 Food
is broken down
here but digested
intracellularly
Cnidarians
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Respiration and
waste removal takes
place through body
walls
Nerve net
Some have a
hydrostatic skeleton
Some move through
jet propulsion
Anatomy of Coral
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The coral polyps build
a calcium carbonate
cup called a corallite
to live in
Coral has stinging
cells called
nematocysts
Stinging Cells
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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
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
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Very specific habitats:
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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
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Coral likes areas with lots
of waves:
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They are strong enough to
withstand the pressure
Freshwater means more
food
Waves remove silt
New water brings more
oxygen
Asexual Reproduction
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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.
Coral Reproduction
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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
A New Home
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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
Arguments for Artificial Reefs
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It can help build or
rebuild a reef
It will increase fish
populations by
making new
habitats
Arguments Against Artificial Reefs
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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
Reefs in North Carolina
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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
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Low rock ridges
Outcroppings
Coral patches
Ship wrecks