Page 12 - The World About Us

Coral reef
1.1.1
2.1.4

What is the global distribution of coral reefs?

Florida Reef
Andros Reef
Red Sea
Coral Reefs Raja Ampat Reefs
Indian Pacific Mesoamerican
Ocean Ocean Barrier Reef Equator

Great
Barrier Reef New Caledonia
Barrier Reef
Approximate loca ons of
warm water coral reefs
fig.28 The global distribution of coral reefs.

Shallow water coral reefs are found Coral reefs can be considered as a
in the tropics and sub-tropics in fragile environment as they are very
rela vely shallow waters. suscep ble to change and disturbance.
Coral is very par cular about the
Nearly all tropical coral reefs are
o
o
found between 30 north and 30 south condi ons in which it can thrive. These
condi ons include:
of the Equator, in shallow waters along o o
the edges of coastlines and out into the ¤ Water between 18 C and 27 C.
shallow seas of the 'con nental shelf'. ¤ Shallow water less than 25m.
2
There is an es mated 300,000km ¤ Salt water at a specific salinity
of coral reefs on the planet. That is just (30-32 parts per thousand).
0.1% of the total area of the oceans. ¤ Water with very li le sediment. fig.29 Mooréa Island, French Polynesia.
Amazingly, tropical coral reefs contain ¤ Areas of strong wave ac on which
an es mated 25% of all the marine produces oxygen-rich water. With such a long list of op mum
species on the planet. They have been ¤ Li le or irregular storm damage. condi ons it is no wonder that coral
described as the 'rainforests of the reefs are rela vely rare. Unfortunately,
seas.’ As coral is not able to cope with ¤ Clean seawater, free of nitrites human ac vity from climate change
and nitrates.
too much sediment in the water, reefs and over-fishing to water pollu on and
are rarely found near river mouths. ¤ Li le exposure to air at low de. sediment from deforesta on are
pu ng many coral reefs at threat.

fig.30 Wave breaking over a reef in the Marshall Islands. Out in the deep oceans some reefs
are found growing on the edges of
volcanic islands as fringing reefs. As the
volcanoes have become ex nct, and
the islands have sunk into the sea, coral
has grown upwards keeping pace with
the surface of the sea. This has resulted
in the forma on of barrier reefs
(separated from the land by a lagoon).
As the islands have sunk completely
beneath the waves, ring-like coral
atolls form as the coral grows to keep
close to the sunlit surface waters.
Scien sts have dated the age of coral
remains at the very base of some
Pacific atolls, discovering it was as old
as 90 million years.
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There are major coral reefs in the world..