Marine biodiversity of South Africa

Last updated
Coelacanth off Pumula on the KwaZulu-Natal South Coast, South Africa, on 22 November 2019 Coelacanth off Pumula on the KwaZulu-Natal South Coast, South Africa, on 22 November 2019.png
Coelacanth off Pumula on the KwaZulu-Natal South Coast, South Africa, on 22 November 2019
Kelps Laminaria pallida (top) and Ecklonia maxima (below) Laminaria pallida (top) and Ecklonia maxima (below) P3290141.JPG
Kelps Laminaria pallida (top) and Ecklonia maxima (below)

The Marine biodiversity of South Africa is the variety of living organisms that live in the seas off the coast 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.

Contents

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. [1]

History

Research on biodiversity of South African waters started in the colonial period from the late 18th century to the late 19th century, with shipboard survey and collection expeditions, like the Challenger, Deutsche Tiefsee and Discovery expeditions. From the early 20th century to the 1970s a group of local marine taxonomists such as J.D.F. Gilchrist and K.H. 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. This has left the region with a shortage of taxonomic expertise in comparison with most of the developed world. [2] :21

The SeaKeys project was started in 2014 to help develop foundational marine biodiversity knowledge by addressing some of the more significant gaps. The project had some success in collating species checklists and records, and national inventories covering over 9700 species in various groups were compiled. Data sets were digitised, distribution data updated for fish and benthic invertebrates, and a guide to offshore marine invertebrates was published. This project highlighted the deficit in taxonomic skills, as it became apparent that most of the guides and lists had not changed much since the 1970s. [2] :22

National Biodiversity Assessments

The National Biodiversity Assessment (NBA) is recurring project by the South African National Biodiversity Institute in collaboration with the Department of Environmental Affairs and several other organisations to assess the state of South Africa's biodiversity over time as an input for policy and decision making where the environment may be affected. The NBA looks into genetic, species and ecosystems biodiversity for terrestrial, freshwater, estuarine and marine environments. Each assessment cycle takes approximately five years, and both generates new knowledge and analyses existing knowledge. [3] NBA reports are named for the year of the data, and are usually published in the following year. They have been published for 2004, [4] 2011, [5] and 2018, [2] and include reports, data, and supplementary documents. [6]

Physical oceanography

Physical oceanography is the sub-domain of oceanography which focuses on the study of physical conditions and processes within the ocean, including the physical properties and circulation of ocean waters. These matters influence the biodiversity by providing the setting in which the ecology and biodiversity evolve.

The physical setting for the biodiversity of the South African coastal and offshore waters is mainly temperate continental shelf, slope and abyss in the South Atlantic and South-west Indian Oceans off the southern part of the continent of Africa. The geomorphology of this region has local effects on the ocean circulation, particularly effects on ocean currents and upwellings, which in turn affect the distribution of organisms and the environment in which they live.

Continental shelf

The continental shelf of southern Africa varies considerably in width along the coast, and the shelf edge also varies in depth. To the north-east the shelf is narrow to very narrow, with a relatively shallow break, but it is much wider over the Agulhas Bank off the southern tip of the continent. This gradual increase in width affects the path of the powerful Agulhas Current, pushing it further offshore towards the Southern Ocean.

Ocean currents

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 Agulhas Current NLOM .png
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. Agulhas chla.png
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 South Atlantic Gyre.png
Benguela Current in the South Atlantic Gyre

The Agulhas Current is the western boundary current of the southwest Indian Ocean. It flows south along the African east coast and along the south-eastern edge of the bank. It then retroflects back into the Indian7 Ocean south-west of the bank. This retroflection results in intense eddy activities such as meanders, eddies, and filaments. [7] In upper layer water, the Agulhas rings and eddies move warm and salty water into the large South Atlantic gyre, which exports it to the tropics. In the lower ocean layers water is transported in the opposite direction. [8]

The Agulhas acts as an oceanic convergence zone. Due to mass continuity this drives surface waters down, resulting in the upwelling of cold, nutrient rich water south of the current. Additionally, the convergence tends to increase the concentration of plankton in and around the Agulhas. Both of these factors result in the area being one of enhanced primary productivity as compared to the surrounding waters. This is especially notable in the Agulhas Retroflection waters, where chlorophyll-a concentrations tend to be significantly higher than the surrounding South Indian Ocean and South Atlantic Ocean waters. [9] Warm core rings are known to have lower primary productivity than surrounding cold waters. 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). [9] Agulhas Rings have also been observed as removing larval and juvenile fish from the continental shelf.

The Benguela Current is the broad, northward flowing ocean current that forms the eastern portion of the South Atlantic Ocean gyre. The current extends from roughly Cape Point in the south, to the position of the Angola-Benguela front in the north, at around 16°S. The current is driven by the prevailing south easterly trade winds. Inshore of the Benguela Current proper, the south easterly winds drive coastal upwelling, forming the Benguela Upwelling System . 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.

Upwellings

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. Upwelling animated.gif
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.

Upwelling is an oceanographic phenomenon that involves wind-driven motion of surface water away from the coast, which is replaced by a flow of deeper dense, cooler, and usually nutrient-rich water towards the ocean surface, The nutrient-rich upwelled water stimulates the growth and reproduction of primary producers such as phytoplankton. Due to the biomass of phytoplankton and presence of cool water in these regions, upwelling zones can be identified by cool sea surface temperatures (SST) and high concentrations of chlorophyll-a. [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]

Ecological regions

Marine ecoregions of the South African Exclusive Economic Zone (redefined 2011) Ecoregions of SA EEZ.png
Marine ecoregions of the South African Exclusive Economic Zone (redefined 2011)

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. There were originally five inshore bioregions over the continental shelf and four offshore bioregions covering the continental slope and abyssal regions. These bioregions are used for conservation research and planning. They were defined in the South African National Spatial Biodiversity Assessment of 2004. [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. [5]

Habitat types

A total of 136 marine habitat types have been identified. These include 37 coastal habitat types, 17 inshore habitat types in the 5 to 30 m depth range, 62 offshore benthic habitat types deeper than 30 m, and 16 offshore pelagic habitat types, [13] three types of island and one type of lagoon. [5]

Endemism

Endemism is the ecological state of a species or other taxonomic group being native to a single defined geographic location, such as an island, country or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. The extreme opposite of an endemic species is one with a cosmopolitan distribution, having a global or widespread range. Although the specific drivers of endemism are unclear, physical, climatic and biological factors can contribute to endemism. Endemic species can easily become endangered or extinct if their already restricted habitat changes, particularly—but not only—due to human actions, including the introduction of new species.

Over 13000 species of marine organisms are recorded from South African waters. Endemism is estimated at between 26 and 33%, the third highest marine endemism after New Zealand (51%) and Antarctica (45%). This varies between taxonomic groups from no endemic marine mammals or birds, to over 90% of chitons. [2] :20

The region of highest known endemism is the south coast Agulhas inshore ecoregion, which is relatively far from the national borders, and relatively isolated from large scale oceanic circulation due to the effects of the widening of the continental shelf at the Agulhas Bank on the path of the Agulhas current, and far from other warm temperate regions. 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. It is also isolated from the South Atlantic and Southern Ocean, so has been more prone to niche speciation. [2] :20

Species lists

National

Marine animals

Seaweeds

Prokaryotes

Regional

Economic value

Protection

Biodiversity protection is one of the priorities of the network of marine protected areas of South Africa. [14]

A marine protected area of South Africa is an area of coastline or ocean within the exclusive economic zone (EEZ) of the Republic of South Africa that is protected in terms of specific legislation for the benefit of the environment and the people who live in it and use it. [15] An MPA is a place where marine life can thrive under less pressure than unprotected areas, like underwater parks, and this healthy environment can benefit neighbouring areas. [16] [17]

There are a total of 45 marine protected areas in the South African EEZ, with a total area of 5% of the waters as of 2019. The target was to have 10% of the oceanic waters protected by 2020. 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.

People can take part in a wide range of non-consumptive activities in all of South Africa's MPAs, and some parts of some MPAs are zoned for limited consumptive activities. [17] Some of these activities require a permit, which is a form of taxation.

Threats

Research organisations

Publications

Books

Field guides:

Journals

Reports

See also

Related Research Articles

<span class="mw-page-title-main">Benguela Current</span> Ocean current in the South Atlantic

The Benguela Current is the broad, northward flowing ocean current that forms the eastern portion of the South Atlantic Ocean gyre. The current extends from roughly Cape Point in the south, to the position of the Angola-Benguela front in the north, at around 16°S. The current is driven by the prevailing south easterly trade winds. Inshore of the Benguela Current proper, the south easterly winds drive coastal upwelling, forming the Benguela Upwelling System. The cold, nutrient rich waters that upwell from around 200–300 m (656–984 ft) depth in turn fuel high rates of phytoplankton growth, and sustain the productive Benguela ecosystem.

<span class="mw-page-title-main">Agulhas Bank</span> Broad southernmost part of the African continental shelf

The Agulhas Bank is a broad, shallow part of the southern African continental shelf which extends up to 250 km (160 mi) south of Cape Agulhas before falling steeply to the abyssal plain.

<span class="mw-page-title-main">Nils Bang</span>

Nils Daniel Bang was a South African oceanographic scientist who was a pioneer in the study of the fine structure of coastal upwelling systems. In March 1969, Bang initiated, planned and executed South Africa's first truly multi-ship oceanographical research operation, the Agulhas Current Project, along the current's length. Although the research was conducted on a limited budget and with rudimentary equipment, Bang's studies using thousands of closely spaced bathythermograph readings were later corroborated by satellite imagery and airborne radiation thermometry.

The Good Hope Jet is the northward-running shelf edge frontal jet of the Southern Benguela Current off the Cape Peninsula of South Africa's west coast. The jet, an intrusion of water from the Agulhas Current, was first described by South African oceanographers, Nils Bang and W.R.H. (Bill) Andrews in 1974. This warm water jet forms a sharp front as it comes into contact with the colder upwelled water over the shelf and plays a key role in carrying fish eggs and larvae from their food-poor Agulhas Bank spawning grounds to inshore nurseries.

<span class="mw-page-title-main">Table Mountain National Park Marine Protected Area</span> Marine conservation area around the Cape Peninsula in South Africa

The Table Mountain National Park Marine Protected Area is an inshore marine protected area around the Cape Peninsula, in the vicinity of Cape Town, South Africa. It was proclaimed in Government Gazette No. 26431 of 4 June 2004 in terms of the Marine Living Resources Act, 18 of 1998.

<span class="mw-page-title-main">Marine ecoregions of the South African exclusive economic zone</span> Geographical regions of similar ecological characteristics

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 marine protected areas of South Africa are in an area of coastline or ocean within the exclusive economic zone (EEZ) of the Republic of South Africa that is protected in terms of specific legislation for the benefit of the environment and the people who live in and use it. An MPA is a place where marine life can thrive under less pressure than unprotected areas. They are like underwater parks, and this healthy environment can benefit neighbouring areas.

The Helderberg Marine Protected Area is a small marine conservation area on the north-eastern side of False Bay in the Western Cape province of South Africa, It lies between the mouths of the Lourens River in the Strand, and the Eerste River in Macassar.

The Agulhas Bank Complex Marine Protected Area is an offshore marine protected area on the continental shelf lying approximately 39 nautical miles southeast of Cape Agulhas off the Western Cape in the Exclusive Economic Zone of South Africa.

The Southeast Atlantic Seamounts Marine Protected Area is an offshore conservation region in the exclusive economic zone of South Africa

The Dwesa-Cwebe Marine Protected Area is an inshore and offshore conservation region, off the coast of the Dwesa-Cwebe Nature Reserve in the Eastern Cape province, in the territorial waters of South Africa.

The Amathole Offshore Marine Protected Area is an offshore conservation region, extending the Amathole Marine Protected Area in the territorial waters of South Africa.

The Namaqua Fossil Forest Marine Protected Area is an offshore conservation region in the territorial waters/exclusive economic zone of South Africa

The Namaqua National Park Marine Protected Area is an inshore conservation region in Namaqualand in the Northern Cape province in the territorial waters of South Africa. It is closely associated with the Namaqua National Park, with which it has a common border and management.

The Pondoland Marine Protected Area is an inshore conservation region in the territorial waters of South Africa.

The Stilbaai Marine Protected Area is an inshore conservation region in the territorial waters near Stilbaai on the south coast of the Western Cape province of South Africa.

The Marcus Island Marine Protected Area is a inshore conservation region in the territorial waters of South Africa

The Biodiversity of South Africa is the variety of living organisms within the boundaries of South Africa and its exclusive economic zone. South Africa is a region of high biodiversity in the terrestrial and marine realms. The country is ranked sixth out of the world's seventeen megadiverse countries, and is rated among the top 10 for plant species diversity and third for marine endemism.

The Amathole Marine Protected Area is an inshore conservation region in the territorial waters of South Africa, near East London on the coast of the Eastern Cape.

The Trafalgar Marine Protected Area is an inshore conservation region in the territorial waters of South Africa in kwaZulu-Natal, between Port Edward and Margate.

References

  1. "Tenfold increase in marine protected areas supports SA'S sustainable oceans economy". www.sanbi.org. 7 October 2019. Retrieved 30 August 2020.
  2. 1 2 3 4 5 Sink, Kerry, J; Van der Bank, Megan; Majiedt, Prideel; Harris, Linda; Atkinson, Lara; Kirkman, Stephen; Karenyi, Natasha (29 September 2019). South African National Biodiversity Assessment 2018 Technical Report (Report). Vol. 4: Marine Realm. South African National Biodiversity Institute. hdl:20.500.12143/6372.{{cite report}}: CS1 maint: multiple names: authors list (link)
  3. "National Biodiversity Assessment". www.sanbi.org. 4 March 2018. Retrieved 14 February 2019.
  4. 1 2 Lombard, A.T.; Strauss, T.; Harris, J.; Sink, K.; Attwood, C.; Hutchings, L. (2004). South African National Spatial Biodiversity Assessment 2004: Technical Report (PDF) (Report). Vol. 4: Marine Component. Pretoria: South African National Biodiversity Institute.
  5. 1 2 3 Sink, K; Holness, S; Harris, L; Majiedt, P; Atkinson, L; Robinson, T; Kirkman, S; Hutchings, L; Leslie, R; Lamberth, S; Kerwath, S; von der Heyden, S; Lombard, A; Attwood, C; Branch, G; Fairweather, T.; Taljaard, S.; Weerts, S.; Cowley, P.; Awad, A.; Halpern, B.; Grantham, H; Wolf, T. (2012). National Biodiversity Assessment 2011: Technical Report (PDF) (Report). Vol. 4: Marine and Coastal Component. Pretoria: South African National Biodiversity Institute. p. 325. Note: This is the full document, with numbered pages.
  6. "2018 National Biodiversity Assessment". biodiversityadvisor.sanbi.org. Retrieved 30 August 2020.
  7. Blanke, B.; Penven, P.; Roy, C.; Chang, N.; Kokoszka, F. (2009). "Ocean variability over the Agulhas Bank and its dynamical connection with the southern Benguela upwelling system" (PDF). Journal of Geophysical Research. 114 (C12028): Introduction, pp. 1–2. Bibcode:2009JGRC..11412028B. doi: 10.1029/2009JC005358 . Retrieved 2 January 2015.
  8. Ruijter, W. P. M., de; Cunningham, S. A.; Gordon, A. L.; Lutjeharms, J. R. E.; Matano, R. P.; Piola, A. R. (2003). "On the South Atlantic Climate Observing System (SACOS)" (PDF). Report of the CLIVAR/OOPC/IAI Workshop: 45. Retrieved 4 January 2015.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  9. 1 2 3 Mann, K. H.; Lazier, J.R. (2006). Dynamics of Marine Ecosystems: Biological-Physical Interactions in the Oceans (3rd ed.). Blackwell Publishing. ISBN   978-1405111188.
  10. Anderson, DM; Prell, WL (1993). "A 300 KYR record of upwelling off Oman during the late quaternary: evidence of the Asian southwest monsoon". Paleoceanography. 8 (2): 193–208. Bibcode:1993PalOc...8..193A. doi:10.1029/93pa00256.
  11. Sarhan, T; Lafuente, JG; Vargas, M; Vargas, JM; Plaza, F (1999). "Upwelling mechanisms in the northwestern Alboran Sea". Journal of Marine Systems. 23 (4): 317–331. doi:10.1016/s0924-7963(99)00068-8.
  12. Jennings, S.; Kaiser, M.J.; Reynolds, J.D. (2001). Marine Fisheries Ecology. Oxford: Blackwell Science Ltd. ISBN   0-632-05098-5.
  13. Sink, K.; Holness, S.; Harris, L.; Majiedt, P; Atkinson, L; Robinson, T; Kirkman, S; Hutchings, L.; Leslie, R; Lambeth, S; Kerwath, S; von der Heyden, S; Lombard, A; Attwood, C.; Branch, G.; Fairweather, T.; Taljaard, S.; Weerts, S.; Cowley, P.; Awad, A.; Halpern, B.; Grantham, H; Wolf, T. (2012). National Biodiversity Assessment 2011: Technical Report (PDF) (Report). Vol. 4: Marine and Coastal Component. Pretoria: South African National Biodiversity Institute. Key findings. Note: This is the executive summary
  14. "Government Notices - Department of Environmental Affairs". Regulation Gazette No. 10553. Pretoria: Government Printer. 608 (39646). 3 February 2016.
  15. "Protecting the ocean". www.marineprotectedareas.org.za. Retrieved 18 January 2019.
  16. "Marine Protected Areas". www.saambr.org.za. Retrieved 16 May 2019.
  17. 1 2 Mann-Lang, Judy; Mann, Bruce; Sink, Kerry, eds. (September 2018). "Fact sheet 3: Marine Protected Areas" (PDF). SAAMBR. Retrieved 15 May 2019.