178
WORLD ATLAS OF CORAL REEFS
Part
The Indian Ocean and
Southeast Asia
The
Indian Ocean is the third largest ocean. It
IS closed to the north, and a large proportion
of Its waters are tropical or near tropical.
Unlike the Atlantic it is largely bounded
by relatively arid countries and does not
receive particularly high inputs of freshwater or terrestrial sedinnents. The great exception to this is the
Bay of Bengal in the northeast, which is fed by massive
riverine discharge from a number of rivers, leading to
conditions of high sediments and low, fluctuating
salinities - inimical to coral reef development. To the
northwest are the enclosed sea areas of the Red Sea
and the Arabian Gulf, with very different tectonic
histories, but both occurring in highly and regions with
little terrestrial runoff. The coast of East Africa is also
relatively dry. Continental shelf areas are generally
narrow, although there are a few nearshore island
groups which are important for coral reef development.
There are also several oceanic island groups, notably in
the west and central parts of this ocean. The largest
chain of islands follows the Chagos-Laccadive Ridge,
a volcanic trace which has formed the Lakshadweep
Islands in India, the Maldives and the Chagos
Archipelago. Reunion and Mauritius are high islands
lying at the most recent end of this volcanic trace, with
active vulcanism on Reunion. The Seychelles form a
more complex group of islands with varied origins.
To the east there are fewer remote oceanic islands,
and the region blends into the reefs of Southeast Asia
with the island chains of the Andaman and Nicobar
Islands, and the Mentawai Islands to the west of
Sumatra in Indonesia.
There are large areas of coral reef right across
this region, making up nearly 20 percent of the world
total. Fringing reefs predominate along much of the
Red Sea, particularly northern and central parts.
Further south in the Red Sea and Arabian Gulf coastal
sediments and high salinities restrict fringing reef
development, though there are extensive offshore
patch reefs. Cool upwellings limit the development of
true reefs along parts of southern Arabia and Pakistan.
Further south there are fringing communities on the
coasts of East Africa, and particularly along the shores
of continental islands. Some of the best developed reef
I
WORLD ATLAS OF CORAL REEFS
Part
The Indian Ocean and
Southeast Asia
The
Indian Ocean is the third largest ocean. It
IS closed to the north, and a large proportion
of Its waters are tropical or near tropical.
Unlike the Atlantic it is largely bounded
by relatively arid countries and does not
receive particularly high inputs of freshwater or terrestrial sedinnents. The great exception to this is the
Bay of Bengal in the northeast, which is fed by massive
riverine discharge from a number of rivers, leading to
conditions of high sediments and low, fluctuating
salinities - inimical to coral reef development. To the
northwest are the enclosed sea areas of the Red Sea
and the Arabian Gulf, with very different tectonic
histories, but both occurring in highly and regions with
little terrestrial runoff. The coast of East Africa is also
relatively dry. Continental shelf areas are generally
narrow, although there are a few nearshore island
groups which are important for coral reef development.
There are also several oceanic island groups, notably in
the west and central parts of this ocean. The largest
chain of islands follows the Chagos-Laccadive Ridge,
a volcanic trace which has formed the Lakshadweep
Islands in India, the Maldives and the Chagos
Archipelago. Reunion and Mauritius are high islands
lying at the most recent end of this volcanic trace, with
active vulcanism on Reunion. The Seychelles form a
more complex group of islands with varied origins.
To the east there are fewer remote oceanic islands,
and the region blends into the reefs of Southeast Asia
with the island chains of the Andaman and Nicobar
Islands, and the Mentawai Islands to the west of
Sumatra in Indonesia.
There are large areas of coral reef right across
this region, making up nearly 20 percent of the world
total. Fringing reefs predominate along much of the
Red Sea, particularly northern and central parts.
Further south in the Red Sea and Arabian Gulf coastal
sediments and high salinities restrict fringing reef
development, though there are extensive offshore
patch reefs. Cool upwellings limit the development of
true reefs along parts of southern Arabia and Pakistan.
Further south there are fringing communities on the
coasts of East Africa, and particularly along the shores
of continental islands. Some of the best developed reef
I