Africa’s Wildest Coast: Life At The Sweeping Edge | Free Documentary Nature

Welcome to one of the most dynamic and violent environments on earth. This rocky shore lies at the edge of the continent, relentlessly covered and exposed by the tides. Here, every living creature clings and holds on for dear life. But despite the punishing forces of the ocean and land, these shores are packed with spectacular life in every color and shape. We are on the tip of the African continent. The two dramatic coasts at the southern tip of Africa harbor a long fringe of nearly 3,000 kilometers between the land and sea, unrivaled for its beauty. This narrow band of coast hosts one of the most vibrant and diverse marine lives on our planet, as two very different ocean currents wash up along opposite shores. The warm Agulhas current sweeps down along the east side of the South African coast, and the cold Benguela current moves up along the south and west coasts. On the windy west and south coasts, the cold ocean is loaded with nutrients thanks to a massive coastal upwelling. These are perfect conditions for the large expanses of submerged golden forests thriving along the shallow rocky coastline. The massive floating forests not only provide shelter from the fury of the Atlantic, but also generate huge amounts of plant food, which is channeled to the shores, creating one of the most abundantly fertile shores on our planet. In the cold ocean, the giant seaweeds are always swaying while breaking up large amounts of plant material, using the waves to move it towards the shores. The rough Atlantic acts as a huge threshing machine, continuously breaking down the floating plants into microscopic pieces. The turbulent ocean near kelp forests also generate impressive amounts of nutritious foam. Down here on the rocky shores, there are millions of customers waiting for this nutritious soup to reach them. Living in this hostile environment has its benefits. The daily rhythm of the tides brings large quantities of food. All you need to do is cling to a rock and wait to be served by the waves. This extra food supplied by the kelp forests creates one of the most productive rocky shores on earth, with record-beating concentrations of plant-eating limpets and filter feeders. Food may be abundant, but what is rarely in short supply is the living space. Every bit of bare rock is crowded and any open space is eagerly contested. Animals and plants are not found at random in the sweeping zone. Order is dictated by a tolerance to extreme forces. In the lower zone, the violence of the pounding waves will remove anything not securely attached to the rocks. Animals with soft and flexible bodies anchor themselves to the rocks. At the other extreme, live limpets with their hard shells and a low profile. And then high on the shore, animals and plants face long hours of being exposed to the sun and dry winds. With low tide, these are potentially lethal conditions and living creatures have to minimize water loss and heat gain to survive until the tides return. To attach to rocks, mussels generate superglue in the form of strings that stick firmly to the rocks. This glue is so potent that it sticks even under cold water. Others take refuge in numbers, forming impressive colonies which diffuse the Living on top of rocks, completely exposed to the waves, is by far one of the hardest challenges along these shores. To survive pounding waves, a soft body must be protected and many creatures living here have solved the problem by developing a hard shelled roof. They are called limpets, a rather flat snail with a large foot and a strong top shield. They look like the marine version of da Vinci's war machine. The rocky shores at the southern tip of Africa are prime limpet territory. But what is even more remarkable is the different way these molluscs stay alive and thrive. They feed on algae by using a long grasping tongue, which is a marvel of cutting engineering. The rod of sharp teeth is lined with hard minerals that keep the razor sharp cutting edge filed. A limpet's foot produces a sticky and dense mucus that creates a perfect seal between the rock and the foot, making it impossible to dislodge a limpet by simply pulling on it. The thicker the mucus, the stronger the attachment to the rocks. The shell design is also vital. Some resemble a fast sports car. Limpets living on more exposed shores grow hydrodynamic shells with little resistance to water flow. What is even more astonishing is that despite their appearance as a simple mollusc, they display several unique adaptations to survive this hostile environment. Some are able to attain massive densities by maintaining fast growing gardens of nutritious seaweeds around them. Continuous grazing stimulates the growth of these gardens, so limpets never go hungry and virtually never have to move away. The only problem here is that baby limpets need to stay away from bare rock to avoid being crushed or bulldozed by the adults. The solution? To piggyback on larger limpets until they are large enough to maintain their own kingdom of rock and garden. Limpets with fast growing gardens can reach impressive numbers on these shores, living in harmony with each other as neighbours. But for other gardeners, the situation is very different. This spiky limpet has a different and much larger seaweed garden. The intricate pattern of the algae patch is the result of the limpet's erratic grazing, which increases the surface area of the algae, thereby preventing the algae from maturing to the point where it can produce its own defensive chemical weaponry. This limpet shell is heavily armed with strong spikes for self-defence against the other grazers who would love to have a free meal from this tasty garden. These shell spikes are used to bulldoze away competition or unwanted visitors. Other species of limpets do not bother to grow gardens and go for a much larger meal using an ingenious method. This thick cupped limpet has a serrated edge shell and is preparing to catch its supper. They are most active during the incoming tide that brings the kelp leaves into striking distance. The trap goes up and a vegetarian ambush is set. All that is needed now is good timing. A neighbour already caught a kelp blade. Once the piece is secured, the limpet remains close to the rock and the waves will do the rest. A piece of algae trapped under the shell can be grasped at leisure, safe from the fast currents and waves. Other species of limpets stay away from the pounding waves and live in sheltered and calmer bays. They also need the help of the incoming tides. Sheltered bays house large amounts of drift algae, a potential feast for these flat snails. These are granite limpets which sit securely fastened on the rocks, but all that changes when they feel the tides coming in. The limpets start to mushroom from the rocks. Some are also trying to avoid being a free ride for young limpets. Because the flow is gentle here, these granite limpets not only lift their shell but the entire front part of the sticky foot. They are setting their traps to catch a drifting meal. The incoming tides bring plenty of loose algae ever closer to the sticky foot. Large and heavy pieces of drift kelp can make this operation a bit more complicated, but persistence finally pays off and a meal is secured on the sticky foot. Now there will be plenty to eat for a few days. This large abundance of drift algae helps to maintain one of the largest concentrations of limpets along South Africa's cold shores. One of the reasons why there are so many marine animals and plants crowded on this narrow piece of shore is that the tides and waves bring predictably large amounts of food every day. Some sea travelers took advantage of this food bonanza in the process, changing these rocky shores for good. An alien invasion took place here several decades ago. They arrived from distant shores riding on international commercial trade. Attached to the hull of large ships and living in ballast water, a few individuals spawned in the cold water and soon multiplied. These are Mediterranean mussels. They are one of the most aggressive alien species on the African coast and are taking over large sections of the rocks. Today the invasion continues to expand west and south along southern Africa, completely crowding the rocky shores. Only the warmer Gullis current further east seems to stop the advance. The success of this species is due to the massive amount of food available in the water in the form of microscopic pieces of kelp, which is a nutritious soup for filter feeders. Large amounts of food means that these mussels can grow fast and put a large portion of their energy into reproduction. They are prolific breeders, spawning in the water and producing massive numbers of larvae that settle on the rocks all year round. If the space was limited on the rocks before their arrival, now it is far worse. Mussels are dominating every patch of bare rock and many limpets have no option but to live on top of the mussel shells. Most of the competition here is for bare rock and not even the presence of these well-established limpets can stop the fast-growing mussels from encroaching rapidly on their living space. A dramatic increase of proteins on these shores brought an unexpected bonanza, especially for those that can sit and wait for the food to be brought by the waves. Carpets of sandy anemone do just that. They are one of the longest living organisms in our oceans. Individuals can easily pass the 150-year mark. They are beautiful and primitive creatures that show no sign of aging and they have almost no as their tentacles are armed with powerful stinging cells. Here they sit and wait, forming a carpet of open tentacles ready to capture anything that is dislodged and brought by the tides. These creatures are not picky and any food will do. From pieces of algae to a tasty mollusk, an alien is high on the menu list. Empty clean shells are expelled from their single opening. The mussel bonanza has far-reaching consequences along these sweeping shores. The arrival of a massive food supply on the rocks also changed the life of a unique bird. This is the local African black oyster catcher. A specialized shorebird armed with a razor chisel bill, a unique tool able to dislodge limpets and open mussel shells. Before the arrival of alien mussels this bird was not abundant along the shoreline. There were serious concerns that this beautiful bird may be extinct within a few decades but all that changed quickly. The dramatic abundance of alien mussels on the rocks has done a great deal to restore the bird population. They breed mostly on offshore islands but a few venture to settle along this rocky and sandy coast. On a sandy beach their simple nests are exposed to land predators and off-road vehicles. The survival rate of eggs and chicks is very low and parents have to be constantly on the defensive. But some have adapted to the ever-encroaching urban developments. Here some parents choose to establish their territory next to a coastal railway line. This home is rather noisy and the chicks struggle to catch a morning snooze. Their parents constantly check in on these vulnerable chicks. They need to warm up in the safety of a small cave. Parents are also busy chasing away competition but soon this family home will hit morning rush hour. The sound and vibrations are too much to handle so for these youngsters it becomes a run and hide routine. The safety of the cave is much needed as some above are also looking for breakfast. The noisy hide is just a temporary refuge as parents are waiting for the low tide to start feeding the chicks. At last a fresh worm heralds the beginning of breakfast and the oyster catcher family is on the move. Not far away there is another breeding pair but after a few weeks only one chick survives. Parents start the morning routine by first fencing off neighbours and then waiting for the low tide to expose breakfast for the hungry chick. Getting food from the rocks is a high risk undertaking and getting wet is part of the job. First delivery is a tasty mussel. Next on the menu marine spaghetti. As the morning progresses the chick is finally full and no longer comes out of the shelter. Not a worm goes to waste. Mussels are not the only ones that swarm over the shore. Bear rock is a prime location along this cold coast as food is abundant and the tides and waves always bring more to the millions of filter feeders. If there is no space some animals build their own. These marine worms are master architects. All that they need is plenty of sand to build their intertidal empire. These reef worms build massive intertidal reefs of sandy tubes. These reefs can be up to three meters in diameter and half a meter high. They are built with several tons of sand. Each worm catches sand grains and cements them together to build their home tubes. The trumpet-like tubes are ridged and this design helps with the concentration of food particles along the ridges as well as the easy removal of waste by the fast currents. The dome shape of these tunnels allows water to flow smoothly and reduce drag. At the same time it optimizes foraging for each worm in the colony. The large concentration of worms is aggressive taking up a large space on the shore suffocating everything that doesn't move out of the way. This large whelk is searching for a succulent worm found inside those sandy tubes. This hunter uses a powerful and liquid weapon saliva so acidic that it is able to dissolve the worm's protective sandy tubes to expose the inner tasty flesh. These gigantic sandy castles are temporary as the force of the pounding waves eventually erodes the smooth dome shape of the colony until the entire structure is destroyed. New lava will settle nearby and a new colony will emerge. The cycle of building and destruction goes on as these marine worms need to live in the fast-flowing zone where there is plenty of food. The complex geology of the rocky shore along the South African coast creates a magical world. These are rock pools. They form a complete marine universe ranging from a large diversity of plants to unique inhabitants. These pools are constantly replenished and refreshed by the tides. Many creatures find refuge in sheltered rock pools and not all dangers come from the ocean. For some it may come from the sky. Spiky and rather threatening these beautiful sea urchins have a sensitive skin that cannot cope with the excessive solar radiation. The solution is simple. Build an umbrella and any material will do. This not only creates a much-needed shade for the owner but also helps to conceal its presence. These rock pools have some unique and charismatic landlords. These are the rockfish. They spend most of their time in these pools resting on their pectoral fins waiting for any morsel to be brought by the tides. Their markings and fin movements communicate their intentions. The females do not lay eggs but undergo internal fertilization and give birth to fully developed juveniles. A remarkable adaptation to such a fast-moving environment. They are voracious and opportunistic and are part of the pool cleaning team. As in the African savannah efficient scavengers keep these rock pools in good shape. These are delicate cushion stars that are mostly grazers but can also enjoy some marine flesh. These snails are by far the most efficient cleaning team and their noses detect minute amounts of chemical substances released from body fluids of anyone in trouble. These whelks move fast and are the marine hyenas of the rock pools. They come from all directions and a limpet is no obstacle. In a few minutes the flesh of the victim is quickly removed using their powerful sucking proboscis leaving only a clean shell. Legged predators are more conspicuous here. This is a carnivorous sea star and it is a marvel of hydraulic engineering. Protected with a flexible armor the sea star has hundreds of connected tubular feet that are controlled by water pressure and muscles guiding it with a strong grip and controlled movement over the rocks. Most of their potential prey stays clear when the sea star is searching for food. Many can run at rather high snail speed. Moving south along the South African coast the geology creates an ideal rocky shore. This is De Hoop Nature Reserve one of the 21 marine protected areas along the South African coast. Washing down along the shore the ocean carved the soft sandstone forming a diverse and rugged shore with an abundance of intricate rock pools. As the tide drops the flat rocky shore is exposed and for a few hours the rock pools offer a sheltered and a calm environment. The rock pools create a wonder world with a diverse intricate landscape providing a home for many. It is here where the most intelligent and charismatic mollusk lives. The octopus. Related to limpets and mussels this marine creature evolved into a superb hunter. Instead of a broad and flat foot octopi have eight dexterous tentacles armed with powerful suckers. The shell has been reduced to a minimum and its fluid rubbery body can squeeze into any crevice or even create its own home. The octopus's eyes are among the most complex in the animal world. An ambush hunter they are master of camouflage and are able to learn very complex tasks. If hunting conditions are no good they can simply move to the next rock pool even if that involves getting out of the water. These shallow rocky platforms are rich in food. Large seaweed beds grow in the abundant sunlight and form extensive patches along the shoreline. These are equivalent to the grasslands of the African savannah and to see the grazers that live here we need to wait for the tides to flood the shore. Hundreds of fish move into the shallow water to feed amongst the seaweed beds one of the most productive areas of these sweeping shores. Many of these indigenous fish depend on these tidal shores to find food and shelter and today we see this tidal migration in action since this area is a marine protected area and fish stocks are fully protected. Along the eastern border of the South African coast the landscape changes dramatically. This is a lush coast with many rivers entering the Indian Ocean. This coastal landscape is the product of a much warmer ocean thanks to the Agalus current. The kelp forests so typical of the cold Atlantic can no longer survive in these warm and low nutrient waters. Here live a different set of organisms. Lower down the shore there is a magical gathering of colorful algae and soft corals taking advantage of the fast flowing waters. Magnificent crabs find shelter and food here and this female is carrying a mass of eggs. Sea urchins look more threatening here and some also carry an umbrella. Filter feeder worms put on a magnificent feeding display. Further higher up on the shore large carpets of zoanthids or colonial anemone like creatures cover the rocks. Each polyp forms an upright hollow column crowned by tentacles around the mouth but unlike anemones each individual polyp is joined at the base by connective tissue. Their tentacles are able to capture minute prey and they host microscopic symbiotic algae in their tissues that provide much of its nutrition as well as their green to yellow color. These rather innocent looking polyps are exposed and it's easy to think that any intertidal predator can eat them at leisure. Recently it was discovered that the mucus of these flower-like creatures contains a powerful poison called palytoxin and this explains why zoanthids have few predators. If you eat this jelly you die. Some innovative application in human medicine is now being developed from this potent toxin. This colorful spray of anemones looks similar to zoanthids but they are a collection of individuals forming a formidable and delicate carpet of unmatched beauty on the rocks. They seem motionless but each anemone feeds by capturing tiny creatures from the water as they're moving tentacles open in a time-lapse sequence. Orange anemones do not live in such groups but feed in a similar way. Grazes can be rather intriguing. This is a sea hare in reality a marine snail with just a remnant of a shell on its back usually not visible. This rudimentary shell covers the animal's heart and gills. To breathe water flows in from the front of the folded skin over the gills and out the back through the anus which also discharges the creature's waste. The pulsating movement replaces the water and waste from the chamber as the snail moves. Two pairs of tentacles on the sea hare's head are the smelling organs which help it find edible seaweed. The one closer to her mouth can change shape from tube-like to a flat spade when foraging. Like the zoanthids this naked snail is completely exposed and it could become an easy morsel for any predatory fish or a crab. However their tissues are loaded with toxic chemicals and they are certainly not on the menu of any wary predator. More Alice in Wonderland meets the eye on this warmer shore. Here colonies of sea squirt decorate the rock pools. They look like an underwater forest of blue lollipops. Sea cucumbers lick their tentacles to extract any captured food particles. Higher up on the shore live hardier inhabitants. These are oysters that need to take care not to dry out by being exposed during low tide. This they do by keeping their shells tightly closed. But in a few hours the rhythm of the tides once again will inundate the exposed coast. Large schools of fish wait for the turn of the tides under the cover of rocky ledges. Soon this shore is refreshed. The oysters have plenty of microscopic food brought by the fast-moving water and fish will search for tasty pickings. The sweeping shores of the southern tip of Africa may have more relevance to humanity than previously thought. Large shell middens found along the western south coast of Africa give new insight into the evolution of modern humans. It is well established that the modern human evolved from Africa and new discoveries along the coast of South Africa indicates that people lived here at least 160,000 years ago. They already developed advanced techniques to produce sharp rock tools. The amount of shellfish found in these old middens reveals that our ancestors had a mostly marine diet harvested from the sweeping coast and that may have contributed to the development of modern humans who eventually moved from Africa to the rest of the world. This narrow, rich and violent band of the African coast could become one of the most relevant landscapes in the history of humankind.