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MARINE LIVING RESOURCES OF THE RED SEAA. REFAI BAYOUMIDirectorInstitute of Oceanography and FisheriesAcademy of Scientific Research and Technology101 Kasr El-Ainy StreetCairo, A.R. EgyptABSTRACTThe fauna and flora of the Gulf of Suez, the Gulf of Aqaba and the Red Sea show greatvariability, but consist almost entirely of members of the tropical Indo-Pacific assemblage; many ofthese species range. across the Indian Ocean into the tropical central Pacific. Some algal species,however, come from the Mediterranean Sea. Red Sea flora include about 400 species of seaweeds, 10sea grasses, 50 cyanophytes and two species of mangrove trees. As such the Red Sea fauna and floraoffer’good examples for the study of migration, endemism and distribution of marine organisms.TOPOGRAPHY OF THE RED SEAThe Red Sea has a rifted origin, so that its parallel coasts contain systems of parallel faultsrunning southeast - northwest. In the north, the Gulf of Aqaba marks the beginning of south-southwest- north-northeast rift which ends near Aleppo in Syria. Ras Mohamed, the southernmost tip ofthe Sinai Peninsula, thus lies at a triple junction between the continental plate of Asia, Sinai and Africa.Lateral displacements also have occurred, especially in the Gulf of Aqaba rift (VON WISSMANN,1932; LAMARE, 1936; VON WISSMANN et al., 1942; RATHJENS, 1947; LAUGHTON, 1966).Because of its origin, the Red Sea displays a fairly single topography (e.g. GOHAR, 1954),with a narrow straight trough extending more than 2000 kms in length. The sides run almost parallelto one another, with a maximum distance of some 340 kms at Massawa. The entrance at Babel-Mandab is only 26 kms wide.Deep areas in the Red Sea, exceeding 2000 metres, tend to be narrow, elongated, steep, andirregular. They generally occur near the long axis, but slightly to the east. Such rift-related deepsoften descend by a series of steps about 400 metres in relief. Bottom topography is highly irregular,and locally seamounts are shallow enough to be capped by corals [e.g. Abul Kizan (Daedalus) andPanorama Reefs]. Similarly the Gulf of Aqaba has a trench over 1800 metres deep, discovered by theE.R.S. “Mabahiss”. This also lies nearer to the east side of the Gulf.The Gulf of Suez offers an extreme contrast. It is flat-bottomed and shallow, having anaverage depth of only 50 metres. It shoals to the north; greatest depths in the south are about 80metres.An important feature of the topography of the Red Sea is the shallow sill (about 100 metresdeep) in the south, slightly north of the Straits of Bab el-Mandab, and on which lie the Hanish andJebel Zukur Islands. As will be seen later, this “sill” has a profound effect not only on thehydrography of the Red Sea but also on its biology, and may be considered as the oceanographicboundary of the Red Sea.THE RED SEA ENVIRONMENTThe pelagic and benthic communities of the Red Sea are intimately linked with its hydrographywhich differs from normal oceanic conditions (see GOHAR, 1954, for a detailed review).This abnormality is largely due to the partial isolation of the Red Sea basin from the open ocean, theprevailing wind system and excessive evaporation. The shallow sill north of Bab el-Mandab allows359