Cape Canyon is one of two submarine canyons off the west coast of South Africa and this broader area has been recognized as important in three systematic conservation plans. Both benthic and pelagic features are included, and the area is important for pelagic fish, foraging marine mammals and several threatened seabird species. The canyon and a muddy habitat on the shelf edge are habitat types of limited extent and are considered Critically Endangered. There is evidence that the submarine canyon hosts fragile habitat-forming species, and there are other unique and potentially vulnerable benthic communities in the area. The hard ground areas, particularly those outside of the trawl footprint, are also likely to be susceptible to damage and there are increasing petroleum and mining applications in this area. There are several small coastal MPAs within this area.
The site description has been updated; changes to the delineation are being discussed.
Introduction of the area
This area extends from the Sixteen Mile Beach MPA to include Langebaan Lagoon, Marcus, Malgas and Jutten islands, the Cape Canyon submarine canyon and adjacent shelf edge, and part of St Helena Bay. This area was identified as a priority area through a national plan to identify areas for offshore protection (Sink et al., 2011) and by a systematic biodiversity plan for the west coast (Majiedt et al., 2013). It was also identified as an important area for pelagic ecosystems and species (Grantham et al., 2011).
Description of location
This area is located off the southwest coast of South Africa and is completely within South Africa’s national jurisdiction. The area includes the Cape Canyon, the adjacent shelf edge, outer and inner shelf areas and parts of St Helena Bay. Langebaan Lagoon and the islands off Saldana Bay are also included in this area.
Feature description of the area
The Cape Canyon and surrounding area includes important benthic and pelagic habitats, including a submarine canyon, sand, gravel and mud habitats. It is a dynamic area and parts of the area, particularly within St. Helena Bay, experience low-oxygen water that may support unique biological communities (Sink et al., 2011). The area includes unconsolidated sand and mud benthic habitats and a pelagic habitat type that is characterised by elevated productivity and frequent fronts associated with shelf-edge upwelling (Lutjeharms et al., 2000, Lagabrielle 2009). Biological communities include four distinct benthic macrofaunal communities characterized by molluscs, polychaetes, amphipods and brittle stars (Karenyi, unpublished data), and hard-ground habitats that are poorly known (Sink et al., 2012b). Cold water corals have been collected within the area. Many small islands that provide breeding habitat for several endemic seabird species, most of which are threatened, or seals, occur within in the area (Kemper et al., 2007). The area encompasses a key foraging area for marine mammals (Best 2006, Barendse et al., 2011) and two marine Important Bird Areas (Birdlife et al., 2013). The area has been included in annual demersal fish trawl surveys conducted by the Department of Agriculture, Forestry and Fisheries.
Feature conditions and future outlook of the proposed area
Habitat condition within this broad area ranges from good to poor (Sink et al., 2012a). Pressures are increasing, although the area includes several coastal MPAs (Langebaan, Sixteen Mile Beach, Marcus Island, Malgas Island and, Jutten Island) which protect habitats and species to varying extents. It has been recommended that MPAs in the area should be considered for consolidation, extension, or re-zoning to resolve existing resource conflicts, protect threatened species in their core areas, and minimize stakeholder impacts (Sink et al., 2011). The lagoon system is vulnerable to further impacts, and the islands with their associated seabird colonies are all threatened (Kemper et al., 2007). Petroleum exploration is increasing in the area, and there are new applications for seabed mining for phosphates and other minerals.
Assessment of the area against CBD EBSA criteria
Uniqueness or rarity
Cape Canyon is one of two reported submarine canyons on the west coast of South Africa and in the southern Benguela. This area was identified by two systematic plans because of rare habitat types including the canyon, rare muds and low-oxygen benthic habitats (Sink et al., 2011, 2012a, 2012b, Majiedt et al., 2013). The Southern Benguela Muddy Shelf Edge comprises two patches off Saldahna, covering an estimated 567 km2.
Special importance for life-history stages of species
The area encompasses a key foraging area for marine mammals including humpback and southern right whales (Best 2006, Barendse et al., 2011) and two marine Important Bird Areas. Closer to shore the Canyon is adjacent to several terrestrial IBAs (Bird Island, Dassen Island, Heuningnes River and estuary system, and the Lower Berg river wetlands). The seas extending from these sites have been proposed as a marine IBA for the following seabird species: African Penguin, Bank Cormorant, Cape Cormorant, Cape Gannet, Caspian Tern, Crowned Cormorant, Damara Tern, Great Crested Tern, Kelp Gull and Hartlaub’s Gull. Further offshore, along the shelf edge where commercial fisheries are concentrated, BirdLife International has identified a large area, which overlaps with the Cape Canyon area, as a potential marine IBA for Atlantic Yellow-nosed and Black-browed albatrosses and Cory’s Shearwater. Several other species (e.g. Shy Albatross and White-chinned Petrel) are likely to qualify as trigger species in this area, but tracking data or analyses are lacking. Grantham et al., (2011) also showed that this area had the highest density of breeding seabirds that feed on pelagic species. High densities of sardine and anchovy eggs contributed to the high selection frequency of this broader area in the offshore systematic biodiversity plan for South Africa (Sink et al., 2011). Spawning and nursery habitat for Cape hakes and is also included in this area (Sink et al., 2011, Kone et al., 2013).
Importance for threatened, endangered or declining species and/or habitats
This area is importance for several threatened seabirds including four Endangered seabirds – African Penguin, Bank Cormorant, and Black-browed and Atlantic Yellow-nosed albatrosses. These animals are highly dependent on this area for some or all of their life stages, particularly for foraging. In addition, several species of lower conservation threat status are similarly dependent on this area: the Vulnerable White-chinned Petrel, Cape Cormorant and Cape Gannet. Threatened habitat types include the Southern Benguela Canyon and the Southern Benguela Muddy Shelf Edge, both assessed as Critically Endangered (Sink et al., 2012a,b) and recognized as critical habitats of concern for impacts from the trawl industry (Sink et al., 2012b). The dominant pelagic habitat within the area is considered Vulnerable and is the most threatened of South Africa’s 16 pelagic habitat types (Sink et al., 2012a).
Vulnerability, fragility, sensitivity, or slow recovery
The submarine canyon in this area is considered vulnerable to impact because cold water corals, gorgonians and other slow-growing, habitat-forming species were observed within this area on submersible footage (Diamondfields International unpublished footage, Sink and Samaai 2009). Gilchrist (1921) also reported cold water corals, black corals and two hundred large sponges in a single otter trawl in this area in 1920, and it was only in the 1990s that trawling was initiated in the hard-ground habitats within this area (Sink et al., 2012b). Deep reefs and hard grounds in the area are also likely to host fragile three-dimensional, habitat-forming species, although this has not been confirmed by in-situ research. These habitats are all considered sensitive to demersal trawling and mining (Sink et al., 2011, 2012a, 2012bb).
The most persistent and intense upwelling cell on the entire South African west coast is found within this area at Cape Columbine, resulting in the area downstream having the highest productivity, organic loading (Demarq et al., 2007) and organic carbon deposits on the seafloor (Bailey 1991) on this coast. St Helena Bay has also been identified as the area having the most persistent oxygen-deficient water in the region (Bailey 1991). South of Cape Columbine, a different set of oceanographic features dominate, and frequent pulse upwelling events result in high productivity over shorter periods (Demarq et al., 2007). Cape Canyon and Surrounds includes part of the area with highest copepod biomass on the west coast (Grantham et al., 2011). Large populations of marine top predators forage and/or breed within the area, including several species of seabirds, cetaceans and seals (Best 2006, Barendse et al., 2011, Hutchings et al., 2012).
South Africa’s national habitat map indicates many ecosystems in this area (Sink et al., 2012 a), and this diversity of habitat types is a key driver of this area’s selection in two systematic biodiversity plans (Sink et al., 2011, Majiedt et al., 2013). The submarine canyon, sand and mud habitats, patches of low oxygen water, islands and the adjacent lagoon system contribute to the high habitat diversity in this area (Sink et al., 2011,2012a, Majiedt et al., 2013).
There is some naturalness within this area. Of the two mapped submarine canyons, there is lower trawling effort and fewer pressures in the Cape Canyon, which is the closer canyon to the city of Cape Town (Sink et al., 2011, Sink et al., 2012a,b). Some of the canyon habitat is outside of the trawling footprint, and there are adjacent hard ground areas that are also untrawled (Wilkinson 2009, Sink et al., 2012b). However, there is a port at Saldanha, and several fisheries sectors operate within this area.
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