Table Bay Marine Ecosystem forms part of the Benguela upwelling system, one of the richest marine ecosystems in the world. The Benguela current, which runs up the West Coast of Africa from Cape Point to Angola, pushes warm and nutrient-depleted surface water offshore. This allows the upwelling of colder, deeper water laden with nutrients, such as nitrates, phosphates and irons. These nutrients feed tiny plants, called phytoplankton, in the surface layers of the water.
Small predators are eaten by large predators, including mature jellyfish, squid and octopus; large fish such as sharks, tuna, and mackerel; marine mammals, including seals, dolphins and some species of whales; and birds such as albatross, penguins and skua.
Due to the Benguela system, sea and air temperatures drop markedly as soon as the vessel leaves the harbour. The water in the bay changes in colour at different stages of the upwelling cycle. After strong summer south easters, the water is blue, clean and very cold, carrying fresh nutrients from deeper water layers. After a few days of sunlight, the water becomes greener, a clear sign of algal bloom. The higher densities of zooplankton attract schools of pelagic fish, which, in turn, attract birds, seals, dolphins, and other predators.