200
WORLD ATLAS OF CORAL REEFS
Seychelles
MAPS 7f and g
The
Seychelles is a very large archipelagic nation in
the Western Indian Ocean. The 115 named islands
and atolls together with their associated reef systems can be clearly divided into two distinct regions: the
high islands to the north and the low coralline islands
spread over wide areas to the south and southwest.
The Seychelles Bank lies at the northernmost point of
the Mascarene Ridge and is a large, shallow area (some
31 000 square kilometers) of water, mostly above a depth
of 100 meters. In its center are a number of high granitic
islands of continental origin. These have been described as
a "micro-continenf , having been left behind during the
northwards migration of the Indian sub-continent about 135
million years ago. These are surrounded by widespread but
discontinuous, fringing reefs. Along the east coast of Mahe
and the west coast of Praslin such fringing reefs are well
developed. Reef flats reaching over 2 kilometers in width
and terminating in a high algal ridge are followed by a reef
slope descending to a floor typically at 8-12 meters. Such
clearly zoned reefs are less apparent in more sheltered
locations where more complex reef formations have
developed. Coral cover varies, being virtually absent from
some former reef structures, but abundant in other areas,
including non-reefal slopes and granitic surfaces.
The low coralline islands to the south and west of the
Seychelles Bank fall into a number of geographic groups.
The largest is that of the Amirante Islands, which extend
along a shallow north-south ridge, with the Alphonse group
forming a slightly separate southern section of this chain.
Further south are two small and more disparate island
groups, those of Providence-Farquhar and the Aldabra
group. Finally, directly to the south of the Seychelles
Bank are the isolated islands of Platte and Coetivy. The
reefs in these outer island areas are highly varied, and
include true atolls (St, Joseph, Alphonse, Farquhar), raised
atolls (Aldabra), submerged or partially submerged atolls
(Desroches, Coetivy), and platform or bank structures
(African Banks, Providence-CerO- Coral cover varies considerably between localities, ranging from close to zero on
some banks and reef slopes (notably the large ProvidenceCerf Bank), to 60-70 percent on some atoll slopes.
The Seychelles lie in an area of relatively high faunal
diversity. Some 101 hermatypic coral species and 920
fish species have been listed. The reef fauna is fairly typical of the Western Indian Ocean, as exemplified by the
reef fish: many are widespread across the ocean basin or
wider areas of the Indo-Pacific, however about 15 percent
are confined to the western part. The coral reefs of the
Aldabra Atoll is a raised atoll in the southwest Seychelles and a World Heritage Site. There are many unique species
on land, including the last giant tortoises in the region, while the reefs are important and relatively pristine ISTS068248-4i, 19941.
WORLD ATLAS OF CORAL REEFS
Seychelles
MAPS 7f and g
The
Seychelles is a very large archipelagic nation in
the Western Indian Ocean. The 115 named islands
and atolls together with their associated reef systems can be clearly divided into two distinct regions: the
high islands to the north and the low coralline islands
spread over wide areas to the south and southwest.
The Seychelles Bank lies at the northernmost point of
the Mascarene Ridge and is a large, shallow area (some
31 000 square kilometers) of water, mostly above a depth
of 100 meters. In its center are a number of high granitic
islands of continental origin. These have been described as
a "micro-continenf , having been left behind during the
northwards migration of the Indian sub-continent about 135
million years ago. These are surrounded by widespread but
discontinuous, fringing reefs. Along the east coast of Mahe
and the west coast of Praslin such fringing reefs are well
developed. Reef flats reaching over 2 kilometers in width
and terminating in a high algal ridge are followed by a reef
slope descending to a floor typically at 8-12 meters. Such
clearly zoned reefs are less apparent in more sheltered
locations where more complex reef formations have
developed. Coral cover varies, being virtually absent from
some former reef structures, but abundant in other areas,
including non-reefal slopes and granitic surfaces.
The low coralline islands to the south and west of the
Seychelles Bank fall into a number of geographic groups.
The largest is that of the Amirante Islands, which extend
along a shallow north-south ridge, with the Alphonse group
forming a slightly separate southern section of this chain.
Further south are two small and more disparate island
groups, those of Providence-Farquhar and the Aldabra
group. Finally, directly to the south of the Seychelles
Bank are the isolated islands of Platte and Coetivy. The
reefs in these outer island areas are highly varied, and
include true atolls (St, Joseph, Alphonse, Farquhar), raised
atolls (Aldabra), submerged or partially submerged atolls
(Desroches, Coetivy), and platform or bank structures
(African Banks, Providence-CerO- Coral cover varies considerably between localities, ranging from close to zero on
some banks and reef slopes (notably the large ProvidenceCerf Bank), to 60-70 percent on some atoll slopes.
The Seychelles lie in an area of relatively high faunal
diversity. Some 101 hermatypic coral species and 920
fish species have been listed. The reef fauna is fairly typical of the Western Indian Ocean, as exemplified by the
reef fish: many are widespread across the ocean basin or
wider areas of the Indo-Pacific, however about 15 percent
are confined to the western part. The coral reefs of the
Aldabra Atoll is a raised atoll in the southwest Seychelles and a World Heritage Site. There are many unique species
on land, including the last giant tortoises in the region, while the reefs are important and relatively pristine ISTS068248-4i, 19941.