SANDY SHELF
Much of the life in sandy shelves is buried in the sand, invisible to the naked eye. Worms, snails, mussels, clams and tiny crustaceans are some of the animals that live in sandy shelves. Just as tracks on land give us clues as to who passed by, the trails, tracks and burrows of these animals can be seen on sandy seabeds. These ecosystems support important fisheries such as South Africa’s most valuable fishery which targets hake. Although kingklip was thought to prefer rocky habitats, scientists were surprised to observe these fish burrowing in soft sediments. Rays, guitarsharks and catsharks are often seen on sandy seabeds. Anemones and soft corals including seapens (corals adapted to anchoring in loose sediment) are found on sandy shelves and these attract other species to live among their tentacles. Spiny skinned animals (echinoderms), such as sea urchins, starfish, brittle stars and sea cucumbers are also characteristic of these ecosystems with more being observed with increasing depth.
Pressures on sandy shelves include trawling, mining, petroleum activities and other fisheries (e.g. demersal longlining). South African scientists are working to understand the impacts and ability of sandy seabed habitats to recover after demersal (bottom) trawling. Camera surveys and seabed samples are used to investigate this in experimental trawl closures off Hondeklipbaai. Pollution impact studies, including that from drilling petroleum wellheads, have also been undertaken to guide management of sandy shelves and ensure that healthy seafood continues to be provided by these ecosystems.
Protection for important sandy shelf ecosystems are provided in Namaqua Fossil Forest MPA, Benguela Bank MPA, Agulhas Bank Complex MPA, Protea Banks MPA, Aliwal Shoal Offshore MPA, uThukela Banks MPA, Amathole Offshore MPA and iSimangaliso MPA.
