Marine ecoregions of the South African exclusive economic zone
The marine ecoregions of the South African exclusive economic zone are a set of geographically delineated regions of similar ecological characteristics on a fairly broad scale, covering the exclusive economic zone along the South African coast.
The South African National Spatial Biodiversity Assessment of 2011 amended this to reduce the number of regions to four inshore and two offshore and rename them as ecoregions.
The resulting regions are: Benguela, Agulhas, Natal, and Delagoa ecoregions, which include the coast, continental shelf and shelf edge, and the Southeast Atlantic and Southwest Indian ecoregions include the upper and lower continental slope and abyssal regions.
Along the coastline there are supratidal, above the high-water mark, intertidal between high and low water, shallow photic, or subtidal shoreface, where there is turbulence and enough light for seaweeds to flourish, down to about 10 m, deep photic, where there is less light, down to about 30 m, and sub-photic (lightless) zones, down to the edge of the continental shelf, which varies from about 400 m in the northern part of the west coast, to 200 m in the Agulhas region, 100 m off Natal, and can be shallow as 50 m in the Delagoa bioregion.
[clarification needed] This approximates the line of the mixing zone between the Benguela and Agulhas currents, which separates their fish communities.
[7] The classification of South African marine and coastal habitat types takes connectivity, depth and slope, substrate geology and sediment grain size, shoreline wave exposure, and biogeography into account.
Most of these were offshore, as most of the existing protected areas extend only a short distance from the coastline, and 13 of these are critically endangered.
[clarification needed] The greatest identified impact on marine biodiversity is fishing, including poaching, which additionally threatens the livelihoods of legitimate fishers.
[7] The reduction of freshwater flow from rivers due to dams and other use impacts marine, coastal and particularly estuarine ecosystems.
About 40% of the flow from the largest catchments no longer reaches the estuaries, and this can have disruptive effects to the local ecological processes such as nursery functions.
These effects are most severe on the east coast, and have been linked to linefish stock abundance more than 40 km offshore.
Observed climate change has already affected the ecological, fisheries, and resource management and has further socio-economic implications.
The uncertainty of climate change trends makes the impacts difficult to predict, which increases the complexity of research and management.
