Page 13 - The World About Us

Coral reef
2.1.2
1.1.1

What flora and fauna is found on coral reefs?

Coral reefs are one of the most bio-
diverse ecosystems on Earth. The reefs
provide food and shelter for tens of
thousands of different species of
molluscs, rep les, fish and even large
mammals.
The reefs themselves are built up
over thousands of years by coral
polyps. These are organisms, related to
jelly fish, that live in communi es. Each
head of coral consists of a colony of a
dis nct species.
Hard corals secrete a protec ve
calcium carbonate shell. This hard shell
gives structure to a growing coral
colony. As individual coral polyps die,
new polyps grow on the previous
genera on's skeletons and the coral fig.31 Coral reef, in the sea off Pohnpei, Federated States of Micronesia.
head grows larger.
onto the coral, while the algae have Some molluscs, such as giant clams,
Reefs consist of the living corals and access to the waste products of the se le between the coral heads and
skeletons of tens or even hundreds of coral from phosphorus to nitrogen. filter out plankton from the sea water.
different coral species. The shape of Some reefs have areas of sea Predatory fish, such as reef sharks,
each coral is determined by the species grasses growing across beds of coral patrol the waters of the reef, o en
of coral.
sands. The grasses are grazed upon by hun ng at night when the other fish are
Tropical corals feed on microscopic fish, as well as grazing mammals such less alert.
plankton floa ng in the water, which as manatees and dugong. The crown-of-thorns starfish (see
they catch using s nging cells on the Coral reefs provide homes for as page 29) is a coral killer. It crawls over
polyps' tentacles.
many as two million species, including coral heads, secre ng diges ve juices
The most important plants in coral 4,000 species of fish. Some, such as which dissolve the coral polyps into
reefs do not grow on the reef but are parrot fish, feed directly on the coral, 'soup', ready to be taken into the
actually found growing inside the coral nipping off chunks of coral with their starfish. These starfish are themselves
itself. This Zooxanthellae algae beak-like mouths. The hard parts of the preyed upon by the Triton's Trumpet, a
produces sugars through the process of coral pass through the parrot fish to be large, but slow moving, univalve
photosynthesis. Some of this is passed excreted as coral sand. predatory mollusc.

fig.32 A simplified diagram of a coral polyp. KEY TERMS

tentacles with
s nging cells Atoll: roughly ring-shaped, coral island
(nematocysts) mouth zooxanthellae built above a submerged volcano.
algae
Barrier reef: a coral reef separated
from the land by a lagoon of relatively
shallow water.
Fringing reef: coral structures found
diges ve sac close to the shore.
nematocysts catch
living ssue floa ng prey Polyp: individual member of each coral
linking polyps head colony.
Reef: the solid structure built from
thousands of individual coral heads,
itself built upon layers of dead coral.
coral
skeleton Zooxanthellae algae: symbiotic partner
living inside coral tissues.
calcium carbonate calicealcium carbonate calicealcium carbonate calice
c c
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Ecosystems have distinct distributions and characteristics.cosystems have distinct distributions and characteristics.cosystems have distinct distributions and characteristics.
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