eW/FS/WE/001 The water environment WATER RESOURCES: Marine Water - Ecology AD3.2 South Africa has unique oceanographic conditions. Nowhere else in the world are there such contrasts in currents and physical conditions. This leads to an extraordinary biological diversity. (http://www.botany.uwc.ac.za/sancor) The South African coast has a large number (over 10,000) of species of plants and animals. It comprises almost 15 % of global coastal species and 12 % of these are endemic, that is they occur nowhere else (DEA&T 1997). South Africa’s inshore coastline is divided into 5 bioregions: Above: Gannet colonies at Lamberts Bay. Left: Fishing boats at Laaiplek. Namaqua bioregion: This is a cool, temperate region, dominated by the cold Benguela current, with intensive upwelling. The nutrient rich coastal water has low oxygen levels. This productive bioregion is characterised by extensive mud banks. It supports a significant proportion of the commercial linefish effort. Large colonies of sea birds occur along this region. South-western Cape bioregion: From Cape Columbine southward, the geology changes from mud banks to granite. The biological characteristic of this region is prominent in the seaweed population. South of Cape Columbine the oxygen deficient bottom water extend inshore, causing hypoxic (oxygen deficiency) conditions and subsequently crayfish emerge on the beach. Fishing in this bioregion comprises of trawling and longline fishing. Right: Kelp beds. Right: West Coast crayfish , Jasus lalandii Agulhas bioregion: Contact: ewisa@wamsys.co.za URL: www.waterinfo.co.za Prepared by: eWISA Copyright: All right reserved Sponsored by: This warm, temperate region constitutes an overlay zone with a mixing area of two currents. The continental shelf is at its broadest here (240 km). This region hosts the greatest number of endemics, sparid reef fish, octocorals and algae. It is the spawning and nursery ground for many species, including squid. Pilchard and anchovy spawn on the Agulhas bank and are transported along the west coast via the Benguela jet. This region supports pelagic fishing, trawl fisheries for hake and sole, trap fishery for the indigenous rock lobster and abalone and squid fisheries. The horse-mackerel stock is the mainstay of the mid-water fishery in South Africa. Natal bioregion: The narrow continental shelf ranges from less than 5 to 50km off the Tugela Bank. This area has high riverine input. It is strongly influenced by the southward flow of the Agulhas current. South of Cape St. Lucia a dynamic upwelling exists, providing an important source of nutrients for the Tugela Bank. The commercial line fishery is one of the most important fisheries in this bioregion. Reef habitat is limited and major reef complexes include the Aliwal Shoal and Protea banks. The Natal bioregion supports endemic soft corals. Annually the sardine run is a feature of the southern portion of the Natal bioregion. Above and right: Fishing trawlers and rock lobster. Above: Baby turtle. Right: Sardine run. Delagoa bioregion: This region is characterised by a narrow continental margin, a shallow, steep shelf break and the highest density of submarine canyons. The strong, warm, south-flowing Agulhas current is the dominant oceanographic feature. The water is clear, with little riverine input. Offshore reefs are colonised by corals. Sub-aqueous dunes occur on the shelf. Leatherback and loggerhead turtle nesting occurs only on this region’s beaches. There are no commercial fisheries in the South African component of this bioregion. Rock shore habitats changes dramatically at Cape Vidal. Above: Reef habitat. Contact: ewisa@wamsys.co.za URL: www.waterinfo.co.za Prepared by: eWISA Copyright: All right reserved Sponsored by: