Coral Reefs - International Reading Association

Octocoral
Corals are related to jellyfish. Their bodies are water-filled sacs.
They have a mouth surrounded by stinging tentacles. Unlike
jellyfish, though, adult corals do not move around. Instead, they
build cup-shaped skeletons to protect their soft bodies. Reefbuilding
corals live in large groups called colonies. A single colony
can contain thousands of individual animals, called polyps.
Different species of coral grow in different patterns, forming the
variety of shapes on the reef. The colonies grow larger as some
polyps die off and leave their skeletons behind. New polyps then
create skeletons on top of the old ones. Large reef-building colonies
may grow less than one inch per year.
Coral polyps use their stinging tentacles to catch tiny organisms
that float by. They have another important source of food, too,
though. Coral polyps have algae living in their bodies. The algae
can use the sun’s light to create energy, just like plants. In return
for nutrients and a safe place to live, the algae give the polyp
oxygen and nutrients that it needs. Algae can provide a coral polyp
with more than half of its energy. The algae also give the coral its
beautiful colors. Most corals must live in shallow, clear water so
that the algae can get enough sunlight.
Elkhorn Coral
Pink Coral
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