Marine biodiversity of South Africa

It includes genetic, species and ecosystems biodiversity in a range of habitats spread over a range of ecologically varied regions, influenced by the geomorphology of the seabed and circulation of major and local water masses, which distribute both living organisms and nutrients in complex and time-variable patterns.

South Africa has a wide range of marine diversity with coastline in three oceans, two major current systems, major ocean frontal systems and benthic topography extending to a maximum depth of 5 700 m. There are 179 defined marine ecosystem types, 150 of them around South Africa and 29 around the sub-Antarctic territory of the Prince Edward Islands.

Barnard, described most of the common fauna on a morphological basis, and after 1970 marine research shifted to ecological aspects and taxonomy was largely neglected.

[2]: 21 The SeaKeys project was started in 2014 to help develop foundational marine biodiversity knowledge by addressing some of the more significant gaps.

This gradual increase in width affects the path of the powerful Agulhas Current, pushing it further offshore towards the Southern Ocean.

Agulhas Rings have been observed to carry waters with low chlorophyll-a concentration into the South Atlantic.

The size of phytoplankton in Agulhas Rings tends to be smaller than in the surrounding water (around 20 μm in diameter).

The cold, nutrient rich waters that upwell from around 200–300 m depth in turn fuel high rates of phytoplankton growth, and sustain the productive Benguela ecosystem.

[10][11] The increased availability of nutrients in upwelling regions results in high levels of primary production.

Upwellings that are driven by coastal currents or diverging open ocean have the greatest impact on nutrient-enriched waters and global fishery yields.

[12][9] 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.

[4] 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.

This region is largely bypassed by the Agulhas current, and has cooler inshore water due to upwelling, making it less hospitable to tropical Indo-west Pacific species.

All but one of the MPAs are in the exclusive economic zone off continental South Africa, and one is off Prince Edward Island in the Southern Ocean.

Coelacanth off Pumula on the KwaZulu-Natal South Coast, South Africa, on 22 November 2019
Kelps Laminaria pallida (top) and Ecklonia maxima (below)
Eddies of the Agulhas Current meander past the Agulhas Bank leaking warm and salty water into the South Atlantic before retroflecting back into the Indian Ocean
Mean chlorophyll-a concentration map of the oceans surrounding Southern Africa for 2009. Note the high productivity water in the Agulhas Retroflection and the very high concentrations along the west coast, due to the upwelling of mineral rich water from the cold depths the South Atlantic Ocean, forming the Benguela Current.
Benguela Current in the South Atlantic Gyre
If the wind blows parallel to the coast with sea to the left in the southern hemisphere (such as along the west coast of South Africa), then Ekman transport can produce a net offshore movement of surface water. This may result in coastal upwelling.
Marine ecoregions of the South African Exclusive Economic Zone (redefined 2011)