There are few places on this blue planet that can match the marine diversity found along the shores of Southern Africa. Two very different oceanic currents flank the coast of the southern tip of the African Continent. The west coast of Southern Africa is surrounded by the cold Benguela Current and on the east coast the warm Agulhas Currents moves south from the tropics. These two currents create not only two radically different marine environments but also shape the terrestrial ecosystems and the human settlements along the South African coast.
The cold Benguela Current host one of the largest wind driven upwelling systems in the world, as the dominant and strong south easterly winds push coastal surface waters offshore forcing deep, cold and rich-nutrient waters to wells from the depth. When this cold soup full of nutrients reaches the sunlight at the surface it triggers one of the richest marine environment on earth dominated by large production of plankton and massive kelp forests that fringe the rocky shallow coast. Giant kelp plants dominate the shallow reefs along the Benguela and it is under the shelter of this golden forest that there are a myriad of life with many endemic species. The abundance of kelp also feed the shores as plants and particulate seaweed fuels grazers, filter feeders and scavengers waiting on the rocks and sandy beaches. The west coast of South Africa has some impressive records as the world largest biomass of marine flesh of grazers per unit of rock.
As consequence of the large plankton production the west coast of South Africa support the largest fisheries in the country and some impressive offshore island are home to thousand of marine birds including the Benguela endemics such as the African Penguin, Bank Cormorant, Cape Gannet and the African Black Oystercatcher. The wind driving upwelling not only creates a cold sea along the west coast but because the wind strength can changes daily so does the water temperature and very few species are able to tolerate such large fluctuations, as consequence the marine diversity on the west coast is rather low with few species that can attain massive biomass. The cold oceans also releases very little moisture into the air and most of the west coast is a rather semi-arid land with little fresh water available and therefore fewer human settlements are found along this shores. The effects of the cold Benguela Current can be felt all the way to Algoa Bay in Port Elizabeth and explains the large concentration of breeding Cape Gannets and African Penguins in that area.
Diving in the kelp forest inside marine protected areas is a unique experience to see at close range playful Cape Fur Seals, west coast rock lobsters, large abalone and one of the few places on the planet to dive with large numbers of Seven-gill sharks.
On the east side of Southern Africa the warm, fast flowing current moves south from the Mozambique Channel. This is the intense Agulhas Current of about 100km wide and surface water reaching speeds of 2 meters per second.
The Warm Agulhas Current creates a much benign environment as the warm ocean releases more moisture into the air generating more precipitation and creating a much greener landscape on land. Many more rivers enter the sea compared to the west coast and many more people settle along these shores, as fresh water is more abundant. For the first time semitropical flora and fauna is seen along this coast. The first large mangrove forests are found along the Mgazana Estuary on the Wild Coast.
At the heart of the warm Algulhas Current is the iSimangaliso Wetland Park that is South Africa’s first World Heritage Site with 332000 hectares and containing 3 major lake system and 8 interlinke
d ecosystems. It is also home to Africa’s largest estuarine system and includes large coastal forest dunes, some of the highest in the world. This is a key marine protected area with the most important pristine breeding sites for marine turtles in Africa and also a corridor for migratory humpback whales, dolphins and sharks. This Park is an icon in conservation along the warm Algulhas realm with a distinctive semitropical flavor.
For SCUBA divers this part of the country is paradise as iSimangaliso also protects the southern most coral reef of the African Continent and Sodwana bay is recognized as one of the top diving sites in the world. These reefs are divided into three
groups Northern, Central and Southern reef complexes and unlike other reefs they are attached to submerged and fossilized dunes and host a great diversity of fish species for its size. Since these reefs are located at various depth their show different array of species and makes exploration much more exciting with over a 1000 fish species to be found.
This Park also protects a living fossil. At depth of more than 100 meters, an intricate rocky outcrops form caves that is home of the world’s oldest fish, the coelacanth. This giant belongs to a group of fish found in fossil deposits about 380 million years old, which were presumed to have become extinct before the dinosaurs, but in October 2000 Peter Timm and a team of Trimix divers made the remarkable discovery that shocked the scientific world.
Filming for a television documentary “Shoreline” we have found that the reefs of Sodwana are one of the best in Africa as they are protected and the damages have been kept to a minimum. The reef yield great opportunities for photographers and film makers to record unique species and behavior, and one of the most important component of such a rewarding experience is the deep knowledge of the dive masters at Triton Dive Lodge, as they have been working closely with the scientific and marine conservation community in that region for several years. Filming underwater on Sodwana reefs for Shoreline was a true adventure of discovery as the knowledge and logistic support of Triton divers allows us to obtain unique underwater sequences in such short time, and definitively we will return again to film more interesting underwater stories.
Written by Claudio Velásquez Rojas (Marine Biologist-Film Maker; Homebrew films)