-Gautam Sanka
What is a Coral?
 Coral is an animal in the
phylum Cnidaria and class
Anthozoa
 Coral exists in the ocean as
polyps which are a form of
life in Cnidarians.
 Polyps are cylindrical and
are attached to a substrate.
They also have many
tentacles extending
outwards to gather food.
Corals as Polyp
Then what are Coral Reefs?
 A coral reef is about a
million of these individual
coral polyp shells all stuck
one on top of the other.
 As coral die, new coral
builds up on top of dead
shells
 These reefs are best suited
for shallow, clear, warm
waters
 Reefs are some of the most
biodiverse places on earth.
Coral Reef with many coral and
fish as well
How do Coral Reefs Form?
 Coral Reefs form in
tropical waters as these
waters satisfy their specific
conditions:
 Salinity between 34-37 ppt
 Temperature between 25
to 37 degrees C
 Lots of Sunlight that limits
them to a depth of 40m
 Reefs have a cycle that they
follow:
 Fringing Reef
 grow in shallow water that
is connected to the shore
 Barrier Reef
 separated from a mainland
or island shore by a deep
lagoon
 Atoll
 circular or continuous
barrier reef extending all
the way around a lagoon
without a central island
Darwin’s Structure and Distribution
of Coral Reefs
Lagoon
What are Zooxanthellae?
 Zooxanthellae are
flagellate protozoa that
are golden-brown
 They are autotrophs and
need the sunlight to
survive
Zooxanthellae algae
Coral-Zooxanthellae Symbiosis
 Symbiosis is a relationship that benefits both the coral
and the Zooxanthellae
 Inside the sac of each coral polyp the zooxanthella
 The algae gives off oxygen and other nutrients that the
coral polyp needs to live and the polyp gives the algae
CO2 and a home
 This partly the reason that Coral live in shallow watersto have proper access to sunlight
Bleaching and Death
 Recent increases in ocean
temperatures have caused
much stress on coral reefs
 Coral bleaching occurs
when the Zooxanthellae
leave due to the stress on
the ecosystem
 The algae gives the coral
their color and without
them, the white limestone
shells show through.
 Other plants will come to
replace the algae which
usually leads to the Coral
dying.
This coral reef is undergoing
massive coral bleaching
Youtube Video of Bleaching
Review Questions
 Is Coral an Animal or Plant?
 What Phylum does Coral belong to?
 What is one example of a symbiotic relationship with
coral?
 Name the three types of reefs summarized by Darwin.
 What are some general conditions Corals must live in
to survive?
 What is one human cause of Coral Bleaching?