Coral reefs are highly biodiverse ecosystems home to many interdependent species. Corals are composed of calcium carbonate secreted by coral polyps in a symbiotic relationship with algae. This relationship provides nutrients to the polyps and gives corals their color. There are two main types of corals - hard corals with rigid skeletons and soft corals without. Coral reefs consist not just of corals but also many other plants and animals that rely on corals for food and shelter. The ecosystem derives its initial energy from sunlight which powers photosynthesis, providing energy that passes through the food web.

1. CORAL REEF ECOSYSTEMS
Done by Thoiban, Ameen, Haniu & Saneeh

2. WHAT IS A CORAL?
• Corals are composed of thin plates, or
layers, of calcium carbonate secreted over
time by hundreds of soft bodied animals
called coral polyps.
• Polyps range in size from a pinhead to a
foot in length.
• Each polyp lives in a symbiotic relationship
with a host zooxanthellae that gives the
coral its color

3. • Zooxanthellae take in carbon
dioxide, process it through
photosynthesis, and give off oxygen and
other important nutrients that are then
used by the host polyp.
• As in all photosynthesizing organisms, this
means that corals must be exposed to a
sufficient amount of sunlight. This confines
most corals to shallow waters that are
clean and clear.

4. • There are two kinds of corals: hard and
soft. Hard corals (Scleractinia), such as
brain, star, staghorn, elkhorn and pillar
corals have rigid exoskeletons, or
corallites, that protect their soft delicate
bodies.
• Soft corals (Gorgonians), such as sea
fans, sea whips, and sea rods, sway with
the currents and lack an exoskeleton.

5. WHAT IS A CORAL REEF?
• Coral reefs are one of the most biologically
diverse ecosystems on earth, rivaled only
by tropical rain forests.
• They are made up not only of hard and
soft corals, but also
sponges, crustaceans, mollusks, fish, sea
turtles, sharks, dolphins and much more.

6. • Competition for resources such as
food, space and sunlight are some of the
primary factors in determining the
abundances and diversity of organisms on
a reef.
• Each component of a coral reef is
dependent upon and interconnected with
countless other plants, animals and
organisms.

7. • This means that fluctuations in the
abundance of one species can drastically
alter both the diversity and abundances of
others.
• While natural causes such as hurricanes
and other large storm events can be the
stimulus for such alterations, it is more
commonly anthropological forces that
effect these types of shifts in the
ecosystem.

8. • For example, overfishing of herbivorous
fish often results in increased growth of
algae and sea grasses. This generally
results in an increase in other herbivorous
marine life, such as sea urchins.
• Over time all ecosystems will naturally
establish these types of balances between
predators and prey and organisms in
competition for similar resources.

9. WHAT IS A CORAL REEF
ECOSYSTEM?
• The coral reef ecosystem is a diverse
collection of species that interact with each
other and the physical environment.
• The sun is the initial source of energy for
this ecosystem.
• Through
photosynthesis, phytoplankton, algae, and
other plants convert light energy into
chemical energy. A portion of this energy
is passed on as animals eat plants or

10. CORAL REEF ANIMALS
• Coral reefs provide habitats for a large
variety of plants and animals. These plants
and animals rely on corals as a source of
food and shelter. Sponges are found
inhabiting holes in the reef. They remove
small chips from the coral. These
sponges, such as Cliona, cause
deterioration in corals.

11. • Sponges inhabit corals for the purpose of
protection from predators. Sea worms
depend on corals for food. They feed on
corals such as Porites and Agaricia.
• Shrimps and crabs depend on corals for
shelter. Xantid crabs form hole in some
types of coral.
• Fish also depend on corals for protection
against predators. One such is the parrot
fish.

12. • Sea stars are coral predators. This crown-
of-thorns starfish relies on corals for food.
• There are many other species of
fungi, sponges, sea worms, crustaceans
and mollusks that bore into coral
skeletons.
• Other organisms that inhabit the coral
reefs include sea
urchins, jellyfish, oysters, clams, turtles, an
d sea anemones.