Rocky shelves, gravels & Reef mosaics

In the mid and outer shelf, rocky or hard shelf ecosystems occur. These are different from sandy or muddy ecosystems because their rocky habitats provide places for animals to anchor themselves to the seabed. South Africa has several rocky shelf areas, particularly in the current-scoured south and east coast. Sponge gardens and coral habitats are characteristic of such rocky areas. These ecosystems are sensitive to pressures that can damage the seabed, including bottom trawling, seabed mining and petroleum drilling.

Gravel habitats are not well studied, especially in South Africa. Gravel is hard like rocky reef habitat, but the rocky sediment is loose or unconsolidated like sandy habitats. Like rocky habitats, gravels provide places for animals such as soft corals to attach, but like sandy habitats, they can be subjected to movement from strong currents or physical disturbance. Gravels also support burrowing animals and seapens (soft corals with a “foot” adapted to anchor them in loose sediment). Gravel sediments have been shown to take longer to recover than sandy ecosystem types after trawling.

Protection for important rocky shelf ecosystems will be provided in Orange Shelf Edge MPA, Namaqua Fossil Forest MPA, Agulhas Bank Complex MPAAmathole Offshore MPA, iSimangaliso MPA and uThukela Banks MPA.