Hidden Life on Africa's Coasts | Two Oceans | Episode 1

Along this almost barren landscape there lies a submerged and lush forest. Its giant plants keep on growing and reaching for the sunlight. This is kelp and their dense growth form the golden forest of Africa. The forest shelters remarkable and unique marine life. One could say it's the backbone of the cold ocean that surrounds the southern tip of Africa. This delicate forest is one of the most productive ecosystems on our planet. A mysterious world where everything that lives along these shores is linked to these giant plants. This is the southern tip of Africa. Here at the edge of the continent vast expanses of plants line the shallow waters. The forest forms a formidable long barrier that buffers the force of the angry Atlantic. Under the forest there's a sense of calm and shelter. It's a magic world. These upright flexible giants create a protective canopy swaying with the currents. For those dwelling under the forest this means protection from the unruly ocean and plenty of food from above. Kelp is one of the fastest growing plants on our planet. One plant can reach up to 12 meters in length and doesn't need to be supported in the water. These plants can grow up to an astonishing 13 million meters per day. The kelp grows in the cold and rich nutrient waters of the world's oceans and it seems ironic that they flourish at the southern tip of the African continent but the conditions here are perfect for the plants to thrive. The forest only exists along this coast thanks to a mighty natural power. Wind. Along this coast strong and predominantly southeastly winds blow mostly during the spring and summer. Their force is able to push surface waters offshore causing deep cold and nutrient-rich water to surge creating the world's largest wind-driven coastal upwelling. This oceanic conveyor belt brought by the strong winds provides an unlimited supply of nutrients for the plants to grow. Kelp is sensitive to nutrients and temperature and it only lives where water is cold and rich in plant food. The presence of the golden forest along these shores is a result of the cold water along the west and south coasts of South Africa. Here winds are strongest in summer bringing massive amounts of nutrients from the depths. At the same time this coast also receives maximum light from the sun. Plenty of nutrients, cold water and huge doses of sunlight create the perfect conditions for these giant plants to flourish. They race to the surface to keep their photosynthetic blades close to the sun. Surges of cold water create a barren landscape along the west coast of southern Africa. The cold water releases little moisture to the air and most of the moisture on land comes from the sea as fog. In sharp contrast the cold nutrient-rich water produces perfect conditions for the massive kelp forest fringing the shallow coast. Here the contrast between land and sea could not be more dramatic. Kelp needs a rocky substrate to anchor it firmly to the rock. It has a root-like structure that fixes the plant to the rocks but it plays no part in the absorption of nutrients. This is known as a holdfast. To maintain an upright position the plant has a hollow gas-filled stem or stipe that expands at the top to form a floating bulb which holds the strap-shaped leaves on the surface. Everything about kelp is huge. Their fertile blades produce massive amounts of spores. Some 10,000 are released per hour from each square centimeter of blade. The spores are microscopic and will develop into minute males or females that eventually will produce gametes. These gametes will be fertilized to create new plants that will grow to gigantic proportions. Competition on the ocean floor is harsh and rather ingenious. This is a much shorter kelp species that does not float and lives on the rocky floor of the forest. The sweeping action of the plants creates a clean zone around it allowing young plants to settle and grow. This action also removes any potential grazer including urchins that can eat the young plants. Now the clump of seaweed can expand. But life also thrives on vertical rock faces or caves as many animals and plants take advantage of the large food supply and shelter provided by the sweeping leaves. In spite of the wealth of plants in the kelp forest there are few herbivores. However, the ones you do find there are impressive. This giant plant is home to some specialists that only live here. A limpet has adapted to live exclusively on this plant so much so that the shells of adult limpets are shaped to fit their cylindrical home. Young limpets live at the base of the leaves. As they become larger they move to the hand of the plant and once they reach adult size they live exclusively on the stem with a shell fitting perfectly into their home. This is an adult kelp limpet. This mollusk patrols the stem of the plant and bulldozes any competition. The grazing marks are clearly visible as they scratch the surface of the stem for food. Perhaps this is done to avoid overgrazing and making their home vulnerable to destruction by strong currents. The giant kelp plant is also a feeding ground for other creatures and plants that find a safe home here. In deeper waters where there are not that many kelp plants life is prolific on rocky formations. The sway action is absent but food from the forest in the form of microscopic plant detritus feed many of these creatures. These forests are not only beautiful but are among the most productive in the world exceeding the yield of most agricultural areas. Each kelp plant will produce about six times its own weight in waste each year releasing food into the adjacent oceans and shores. In fact this giant forest feeds the entire shoreline as waves carry large amount of plant material to the shores. After strong winds and rough seas large amounts of kelp floats ashore and this is the lifeblood of many waiting along the extensive beaches on this cold coast. At day these beaches seem deserted and devoid of life. Only strange sand heaps suggest that there's something under the sand. These beaches are actually the playground of scavengers but for the moment they are hiding and waiting for the sun to go down and the tide to be right. It's now low tide and with an infrared light we can witness this army coming to the surface. This is the cleaning team of the beach. These are giant isopods. They emerge as a synchronized mob swarming over the beach as they only have about an hour to feed. After emerging they do not care about light and start to search frantically for anything to eat. Their treats are mostly ripe kelp. The giant seaweed was deposited high on the beach by spring tide at least a week ago and by now the plant is soft and tender ready for these hard-working scavengers. These giant isopods plan their exit from their burrows to coincide with the low tide to avoid being washed away by the waves. They also have an internal biological clock that times their daily appearance on the beach by correcting for the delay of the tide that's about 50 minutes later each day. Kelp is not the only item on the menu. Dead seals or a large piece of whale are also tackled. After an hour of ferocious foraging they also synchronize their disappearance act. The next morning the tide brings more kelp to the beach. Each drifting plant is closely inspected for easy pickings. Sandhoppers feast on the fresh abundant gift. High up on the shore a mat of dry kelp helps to conceal the delicate nest of the endemic African black oyster catcher. Parents take turns sheltering the eggs from the cold wind and the blasting sand. And the chain started by the golden forest also provides food to seagulls with good table manners that just need to sit and aim at the ever jumping target. To live under the swaying canopy of this giant forest many fish have developed superb camouflage and even their movement mimic the movement of the seaweeds. Like in any forest there are key species that rule this golden submarine landscape. One of the most fascinating is the sea urchin, a living spiny set of armor. Another key species here is the abalone, a rather large mollusk that feeds mostly on drift algae and kelp leaves. Lifting its shell and part of its foot it's able to trap algae. They grow slowly and only reproduce when they are eight years old. Once they reach a large size they are very much safe under the canopy. Under calm and dark conditions these giant snails are ready to spawn. A few eggs in the water indicate that some females have already started the race. Males soon start to release massive amounts of sperm turning the surrounding waters into a milky soup. The presence of sperm in the water stimulates the females to go on full alert. They respond by having several contractions and expelling large clouds of eggs to be fertilized. Millions of eggs are released and in a few minutes it's all over. After this massive effort only a few eggs will eventually develop into adults. The larvae of abalone are delicate and have a short swimming life. They settle on the rocky seafloor where they need to find a specific hard coralline algae. Once the larva becomes a baby abalone it will seek protection under a spiny nanny and that is a sea urchin. The spiny mobile fortress not only provides safety to the fragile abalone but also some free meals. This relationship is vital for the survival of young abalones under the golden forest. The golden forest floor is ruled by another spiny creature. The rock lobster, a voracious predator. They can open or break almost anything with their sharp claws. The armor of the urchins no match for them. In this forest there is a delicate balance. Too many rock lobsters means disaster for urchins and baby abalones. Too many urchins will prevent the establishment of young kelp as they are removed from the rocky floor by the urchins scraping the baby kelp plants. In this forest these giant snails are becoming fewer and fewer, now dangerously approaching extinction. A situation that has nothing to do with the natural predators that are found under these leaves. Abalone is a tasty morsel for humans particularly in Asia and their high market value is fueling a massive illegal trade. If the situation does not change in the near future this mollusk will be extinct in a few decades as they grow slowly and require a certain critical density of adults to ensure successful reproduction. Human impact extends further as large predatory fish have been overexploited and are rare in this forest. Fish that live in the golden forest are particularly sensitive and for a good reason. Many of them have a restricted area to live in. They are endemic, live long and are hermaphroditic. They can live for more than 30 years. This is a good example, the beautiful red roman. As an individual it started its life as a female and as it grew became a male. The simple reproductive system of fish allows them to change sex by making small changes in the gonad structure. It's a good idea to reproduce as a female when they are small and protected by the larger males. Red roman males are territorial. This male has a perfect living space with a cave well flushed by the waves, something that filter feeding worms and sponges appreciate. Males constantly compete for the best living space under the canopy and keep a close eye on their neighbor by regularly patrolling their territories. But sex reversal does create some problems when we bring humans to the equation and the fish population is heavily overexploited. Usually the larger and more aggressive fish is caught first. In the case of the red roman that is mostly the male and the result is a serious imbalance in the male-female ratio in the population. Such imbalance where there are low numbers of males encourages females to change sex when they are still small, therefore producing fewer eggs. Finally the egg production is insufficient to sustain the population. For the red roman and many similar species it's paramount to protect both the large male as well as the smaller females and this can only be achieved by creating marine protected areas where a healthy pool of fish is protected from fishing. Closely linked to the upwelling there are some truly charismatic inhabitants. The african penguin is the only penguin found along these cold waters of Africa. They are one of the four banded penguins found on earth. They feed on fish that thrive in the open sea far away from the golden forest but when it's breeding season they have to return to their colony daily. During spring low tide the kelp forest forms a formidable and slippery barrier of ever-moving giant plants. Wrestling with these giant sea bamboos requires determination and effort. Some attack this problem head-on and make it to land safely. This is the seven gill shark or a cow shark one of the most primitive sharks found in our oceans. They glide at ease amongst the kelp. Most of the individuals have mating bite marks and the females seem to be heavily pregnant. Here in the shelter of this forest several sharks gather perhaps to seek refuge from its real enemy the great white shark. In open water seven gill sharks do not stand a chance. It is in this golden forest of Africa where cow sharks gather in one of the largest concentrations found in the world's oceans. Many divers travel to South Africa to experience a close encounter with these sharks under completely natural conditions. No shark bait or chum is used and divers can freely swim with them. The cow sharks may look slow and placid but they're also formidable hunters. Working in packs they are able to hunt large fish and marine mammals. Seals are also on their menu. Seals evolved in the north pacific ocean 11 to 12 million years ago and subsequently spread to the southern hemisphere. Here in South Africa they live along the cold benguela current associated with the kelp forest. Seals are an extraordinary example of evolution. That of a land mammal that's adapting to an aquatic marine life. Their skeleton structure and physiology enables them to become master divers. They do however remain true to their amphibian lifestyle and retain a bond with the shore for breeding. One of their unique adaptations is the increased total body oxygen for diving. Like the majority of marine mammals most of the oxygen is stored in the blood and muscle and lungs are a minor source of oxygen. Seals exhale most of their total lung capacity just before diving. Seals are strikingly different to humans but you can easily recognize our common origins. The front flippers are bone by bone equivalents to our arms and hands. The front flippers are powered by well-developed pectoral muscles while the rear flippers trail behind and are only used in turning and stopping. Their agility and fluid movements underwater are astonishing. Seals are intelligent mammals and just like a dog they can be trained to perform complex tasks. While they are young they use playful activities to practice hunting and to escape fast chasing sharks. But here in this unique breeding colony seals seem to be also doing something rather different. The colony has an area where young seals are concentrated in large numbers in the water. Having thick blubber makes them overheat on land and the cold water is an ideal place to remain comfortable especially in the hot summer. But the same blubber is also great food for sharks. As seals play they seem to be constantly inspecting the ocean floor eyeing the rubbery algae that are an invitation to bite and play. Soon the seals play turns into cropping kelp plants. Hundreds of seals biting the plants every day lead to some interesting underwater landscaping. At the extreme end some plants are completely destroyed as the leaf is bitten off killing the plant. The snowball effect of such activity leaves the ocean floor with a rather short algae cover. Perhaps seals are doing this to make sure that sneaky sharks are detected underwater in time as they only rely on vision to detect danger and have a very short window to escape. For seals swimming underwater to have constant visual contact with one another can be of great survival value. If an individual detects approaching danger the fast swimming reaction can be easily seen by the other seals alerting the entire group. This situation can be even more critical when visibility underwater is low or at night. It seems that in this shallow playground large kelp plants are not welcome and playful seals are also kelp killers. This golden forest of Africa thrives in the cold ocean where massive amounts of nutrients are brought to the surface by strong offshore winds. A unique phenomenon occurs that spells disaster for all the inhabitants of the submerged wonderland. After several weeks of strong southeasterly winds the wind suddenly stops for several days. This means that the water is loaded with nutrients which are no longer replaced periodically by cold clear water from the depths as the conveyor belt driven by wind suddenly stops. At the same time gentle onshore wind is a sure sign for disaster. In the water microscopic algae start to multiply using nutrients rapidly. Some species even migrate from deeper water and dominate the plankton in the ocean surface to the point where the water changes its colour. As a result the oxygen in the water is severely reduced and many that live under the canopy of the kelp forest have nowhere to go. The west coast rock lobster starts to gather in large numbers as they feel the sudden drop of oxygen in the water. Dark waves announce the beginning of a dramatic event along the golden forest of Africa. Many are waiting for the unexpected gift from the sea. An army of rock lobsters tries to escape the oxygen poor environment to reach the shallow waters. Here waves toss them onto the beach and huge numbers are stranded only to die on land. This event provides a huge free meal for gulls that spend days on the beach taking as much as winds restart the conveyor belt once again blowing the oxygen poor water offshore. The new cold clean water surges and life in the forest starts once again. The golden forest of Africa is one of the most diverse environments in the world's oceans. Beautiful creatures have evolved here adorning this magical underwater world. The golden forest has also deeply touched human destiny. For millennia these underwater kelp forests have provided for people around the coastal shores of the world. But it is here at the southern tip of Africa where recent archaeological research suggests these plants also fueled the beginnings of modern human evolution. This forest provides massive amounts of food that leads to the huge production of shellfish along the coast. Large amounts of shellfish fed our ancestors dating back more than 160,000 years. This giant submerged golden water world of the African coast touches all of us.