The New Childrens Encyclopedia

 BRAIN CORAL

is arranged in wiggly

lines that look like the

surface of a brain.

 FAN CORAL

feathers into delicate

shapes and provides a

home for tiny creatures.

 STAGHORN coral

grows in the shape of

branches, which look

like tiny antlers.

Gut

cavity

Tentacle Mouth

Limestone

exoskeleton

1

Fringing reef

forms around

volcanic island.

BIRTH OF AN ATOLL

An atoll starts life as a fringing reef

around a volcanic island. As the

volcano weakens and sinks (or sea

levels rise), the coral grows and

turns into a barrier reef. Eventually,

the volcano disappears, leaving an

atoll—a ring of established coral

reef around a central lagoon.

ALL SHAPES AND SIZES

Coral reefs come in different forms.

The most common is the fringing reef

(such as this one in the Indo-Pacific

Ocean), which grows off many

tropical coasts. Corals can’t grow above

water, so the reef ’s flat top usually lies

just below the surface. Barrier reefs

grow parallel to a coastline, but farther

out, while atolls (see right) form coral

rings in the middle of the sea.

2

Barrier reef grows

around sinking

volcano.

3

Volcano disappears

leaving atoll with

central lagoon.

CROWN OF THORNS

The world’s largest starfish (it has a leg span of 12–16 in/

30–40 cm), the crown of thorns feeds mainly on corals.

Because of this, it can cause serious harm to coral reefs.

The Great Barrier Reef off the coast of Australia, for

example, has been severely

damaged by hungry crown of

thorns. These prickly

creatures hurt people,

too—their spines are

poisonous, so stepping on

one can cause severe pain

and sickness.

Connecting
tissue to
other polyps

AND ECOLOGYENVIRONMENT

77

 SOFT CORALS

have tiny, individual

polyps and can look

like branching bushes.

CORAL REEFS

77

(c) 2012 Dorling Kindersley. All Rights Reserved.(c) 2012 Dorling Kindersley. All Rights Reserved.