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The Gulf of Aden

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The Gulf of Aden

Abstract

The Gulf of Aden lies between southern Arabia and the Horn of Africa and connects with the Red Sea and Indian Ocean. The Socotra Archipelago lies at its entrance, off the Horn of Africa. The largest influence comes from the reversing monsoon system with strong and persistent winds that blow from the southwest in summer, and from the northeast in winter. These also cause a reversal in the direction of surface currents. Associated with the summer monsoon are upwelling areas along the eastern coast of Yemen, and one centrred on the Somali coast southwest of Socotra. Both have a profound effect on coastal habitats and stimulate high marine productivity which supports a rich fishery. Marine biodiversity is relatively high since the area is a transition zone between the Red Sea, Southern Arabia and East Africa. Terrestrial diversity, particularly in the flora of Socotra, is also elevated by high levels of endemism. Coasts are mainly exposed sandy beaches separated by rocky headlands. Coral communities and reefs have developed most notably in Djibouti and offshore islands of Somalia. Seagrasses are relatively uncommon, and mangrove stands are most abundant to the west and southwest. A striking feature of rocky shores is the abundant macroalgae that appears following the onset of the Southwest Monsoon in particular. Green turtles nest in tens of thousands, and thousands of dolphins have also recently been observed. Perhaps the most serious single threat to sustainable use of marine resources comes from overfishing, particularly by industrial fleets that operate with or without licences. Some stocks have collapsed or are showing signs of strain, including cuttlefish, shark and lobster. Wildlife species are also harvested and incidental mortality appears high. Levels of pollution are low except around larger towns where sewage and solid wastes are starting to affect resources. Chronic oil pollution originating from tankers is also cause for concern, but levels appear to be low. Harsh environmental conditions and lack of infrastructure limits exploitation of coastal resources and traditional methods of limiting exploitation are still effective. Political instability and unrest, and lack of funding have hampered coastal management, though a strategic action plan for the conservation and protection of the marine environment has recently been prepared by PERSGA as a crucial first step. There are only two small marine parks in the region, both in Djibouti.
... Further east, almost nothing is yet known of the nature of coral communities along the Makran and Baluchistan coasts of Iran and Pakistan (Ikramuddin & Mermon, 1995), much of which appears to be unsuitable for coral communities, although it is clear that areas of hard substrate do occur (Sheppard & Wells, 1988 These papers have contributed to a number of valuable reviews of the distribution and ecology of corals and reefs that refer to the Arabian region (Sheppard & Wells, 1988;Sheppard, 1988;Sheppard & Sheppard, 1991;Sheppard et al., 2000), updates on the status of corals and reefs Hassan et al., 2002;Rezai et al., 2004;Kotb et al., 2004), and more general texts on the region's marine ecology and conservation status (Sheppard et al., 1992;Wilson & Klaus 2000). ...
... In contrast, the Gulf of Aden was formed by a rift that separated the Arabian and Somali plates during the Miocene era. The Gulf of Aden has more volcanic activity than the rest of the region, and horizontal effusions of black basalt, features called harik (meaning 'burnt or hot place'), occasionally cross the coastal plain to provide hard substrates on which coral communities are most frequently found (Wilson & Klaus, 2000 (Samuel et al., 1997). These too are resistant to erosion. ...
... Sites surveyed in Chagos are those described in Sheppard et al. (2002), and correspond to sites of various reef surveys dating back to the 1970s. 4 See Wilson & Klaus (2000) for the definitions of the boundaries of the Gulf of Aden used here Table 4.4. Please refer to inserts for location of site maps. ...
... Within this area, Masirah Island has been comparatively well investigated as the island harbours a wide diversity of biotopes (from upwelling affected shores to large monotypic reefs) within a limited geographic area (de Vaugelas 2001). The Socotra Archipelago, located within the Somali upwelling area, is likewise identified as the "Galapagos of the Indian Ocean" (Wilson & Klaus 2000) due to its diversity in biota and biotopes. The archipelago recently received scientific interest owing to the comparatively pristine state of its natural environment. ...
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