Under the Coral Africa's Hidden Reef | Two Oceans| Episode 3

This is the warmer of the two oceans which flow around South Africa's coastline. Along the narrow cliffs of the wild coast, the Agulhas current moves quickly towards the southern point of the African continent. On its journey, the current brings abundant rain, which splashes into the many rivers along this portion of coast. This is a pleasant environment and many people settle here. These warm waters also drastically change the marine landscape. Here, a myriad of life and colour flourish. For the first time, we begin to see tidal forests which host a unique diversity of plants and animals. Submerged reefs with vibrant life and colour adorn this underwater world. It is in this warm ocean, hugging Africa, that we find the most pristine coastal marine ecosystem in the world. A miracle of diverse life, protected for all of us to appreciate. As we travel along the eastern coastline of southern Africa, the landscape changes. This coast is warmer than the dry and cold west coast of southern Africa. Kilp forests can no longer survive here as the water temperature is far too warm for these giant algae to flourish. This is the kingdom of the Agulhas current, a warm, narrow and intense body of water that moves ever southwards. Current originates from the tropic and subtropic regions of the Indian Ocean and as such, it is low in nutrients. The mostly narrow edge of the continental shelf off east Africa allows this warm current to flow close to the coast. Unlike the cold Benguela current off south Africa's western coast, these warm waters release massive amounts of moisture into the air. Ample clouds are formed and the interaction between the warm ocean and the atmosphere results in generous rainfall. A greener coastal landscape meets the eye. More people live here and more rivers enter the Indian Ocean. Fresh water is abundant in this paradise. Majestic inland waterfalls and rivers have modeled the landscape, creating massive gorges that pour the fresh water into the Indian Ocean. Here some rivers end abruptly, falling into the sea below. A different environment is found along this coast, sheltered by large river mouths. These are tidal forests. These unique trees adapted to life in a marine environment where their roots are first flooded and then exposed by the tides. Their roots are planted in potentially deadly sediment with no oxygen which would kill any other plant. But these trees have found a solution. Well-developed aerial roots allow each tree to breathe during low tide, much like a plant's snorkel. These aerial roots come in all forms and shapes. Some are knobbly, others delicate and pencil-shaped. The excess of salt can also kill these trees. But once again, the trees adapted by gathering the salt on their leaves. The leaves eventually turn yellow and drop to the mud floor. And if that's not enough, for this bizarre marine forest, the seeds of the mangrove tree germinate while still attached to the flower. Each seedling forms a cigar-shaped fruit which falls into the mud once it matured. A new tree now develops under the shade of the parent tree. One mangrove tree is rather different, however. It drops round seedlings which float some distance from the parent tree before taking root. They become the pioneer species, easily colonizing new areas. These tidal forests are crucial for the warm shoreline as their roots stabilize the sediment in river mouths and coastal lagoons and so maintain a healthy and diverse habitat. Mangroves are one of the most productive environments on earth and below, on the floor, there are many opportunists waiting for a meal. Here, the large amounts of food in the form of leaves, fruits and waste do not go unnoticed. Under these forests, there is also an army of crabs. These are fiddler crabs. They feed by scooping up small amounts of mud, extracting any foodstuff and discarding it as small, clean balls. But what is really amusing are the brightly colored males, rhythmically waving their oversized pinchers to attract females and also to warn male competition to stay clear. The signal doesn't always work and some pincher battles do break out. Most crabs here live in burrows. The sound of a mangrove leaf or a fruit dropping in the mud is enough to alert them to a free meal. Leaves are easy to deal with, but the fruit is an entirely different matter and requires some crab problem solving. Of course, a dead mangrove crab does not go to waste here. The cleaning team is a crab mob. The riches of the mangrove attract other visitors too. A family of vervet monkeys check out the floor for seeds and a small antelope nibbles on a young mangrove tree. Another remarkable creature lives in these mangrove forests. This is the mudskipper, an amphibious fish which walks on land using its pectoral fins to move in a series of skips. This fish truly feels at home out of the water. They also flip their bodies to throw themselves up to two feet into the air. As long as their bodies are moist, they breathe through the skin lining their mouths and throats. They also retain a bubble of air in their enlarged gill chamber, a fish version of a scuba tank. They live in burrows and even here they maintain an air pocket to keep on breathing in the low oxygen level of the water. Watching this interesting lord of the mangrove, it is easy to understand that millions of years ago some fish species gradually adapted to live on land as the first amphibians, so sparking the unprecedented vertebrate evolution. Travelling further north along the warmer gallus current, we find one of the most pristine coasts of southern Africa. This is Isimangaliso, the miracle wetland park. The park is South Africa's third largest protected area and a world heritage site. This shoreline has incredible diversity of coastal habitats, all linked from land to sea with diverse flora and fauna. For hundreds of kilometres, rich coastal forests run parallel to the Indian Ocean all the way to Mozambique. The long neighbouring sandy beaches are prime undisturbed turtle breeding areas. The rich lagoon and estuary have extensive mangroves and unlike other coastal areas in Africa, here hippos and Nile crocodiles are part of the system. They are also protected and give a glimpse of the true mangrove swamps as they were before these large animals were hunted to extinction along the east coast. This magical miracle wetland park was listed as South Africa's first world heritage site in 1999 in recognition of its unmatched beauty and unique biological diversity. The 332,000 hectare park contains three lake systems and eight interlinked ecosystems as well as Africa's largest waterway environment. The 25,000 year old coastal dune forest is incredibly diverse in its plant and animal life. This fragile area is one of the most unique ecosystems on our planet. People are an integral part of this large conservation area as they have lived here collecting marine resources and maintaining small-scale agriculture for at least 800 years. Ingenious barriers along the cosy estuary have ensured that many generations were fed continuously. This trap uses the tidal cycle. During high tide, fish follow the long barriers eventually entering the final funnel trap. At low tide, the owner simply wades to spear the catch. Small fish can easily escape through the gaps. But from the air, the trap provides something subtler. The large palisade structure changes the water and sediment flow around the traps and in doing so brings food for a variety of other fishes. The trap walls create a new living space and new opportunities. The long weaved barrier creates a complex and diverse habitat and the reduction of the current allows seagrass to flourish near these structures. Small fish can move in and out of the traps. That means good food for those willing to wait. These floral moray eels have taken residence under the traps. They feed mostly on crabs and small fish and are active hunters at night. Another beauty attracted to these traps is the flamboyant firefish. Their long spines are venomous and their spiky appearance is well advertised. Their long pectoral fins are used to corner potential prey which is swiftly swallowed with a tubular protruding mouth. This elegant fish spends many hours hiding upside down, waiting patiently for the tide to bring small fish closer. As the tide pushes into the estuary, schools of fish gather near the shade of these traps. All that's left to do for these beautiful predators is sit and wait. Above water, there are always some ready to steal a fish. A small tax to pay back nature. From the air, it is easy to understand why this region was protected, becoming the Miracle Wetland Park. The natural connection between land and sea is uninterrupted as coastal lakes are separated from the sea by a majestic and rich dune forest. But the Miracle Park has many secrets and one of the biggest is found in an underwater playground. Fossil dunes lie under the shallow waters. Unlike true coral reefs which are built over old coral, here localized groups of coral grow directly on top of the solid dunes. Clusters of reef are dotted along this coast, ranging in The dense groups of hard and soft corals create a complex matrix with plenty of living space. The living coral makes this underwater city come alive. This is the southernmost distribution of coral in Africa and as they are protected, they put up a magnificent display of living color and forms. For its size, it holds one of the largest diversity of fish on our planet. Many of them only found here. The rich caves and overhangs are busy marine cities with plenty of tenants. And whenever there is a crowd, their interactions are fascinating. A potato bass becomes a clown following visitors like a pet over the reef. But the real clown here is this appealing fish. The Nemo of the reef, also called anemone fish or clown fish. This courageous little fish lives among deadly anemone. Some hard carapace crabs also take great advantage of living under such a fortress. The tentacles of this anemone can easily kill this beautiful clown, but instead they feel completely at home with each other. The relationship of the fish and the anemone start at a young age. It is a long and gradual process of getting used to one another. It involves chemical changes in the mucus covering the fish, which the anemone then recognizes as a friend. The discharge of lethal stinging cells by the anemone is inhibited by the fish's gentle touch. So young anemone fish spend many days making sure that this is a truly trustworthy affair. The story does not end here. It is not Nemo who rules this deadly crown of tentacles, instead it is the larger dominant female clown. She lives on the anemone with a slightly smaller adult male and several stunted juveniles. If the large female is taken by predators, the adult male changes sex and takes over the role of the dominant female who guards the anemone and her eggs, becoming the new mama of the African reef. The next largest stunted juvenile in line then becomes the male and helps mama to look after the eggs and their home. All clownfish are born as males. It is only when the dominant female dies that the next largest clownfish develops into a fully formed female. Other species of anemone fish or clownfish live in the same manner and some are associated with much larger carpets of deadly tentacles. This is a unique symbiotic relationship between the fish and the anemone. The fish gets a safe home while the anemone is protected from predators and cleaned of parasites. There is no divorce between these two and anyone trying to break their bond will have a painful encounter. Knowing that they are well protected, they can live on the exposed side of the reef. Small fish are always a danger on these reefs and Nemo has found a genius solution. Many other small species have no option but to hide in the nooks and crannies of the reef. These rock cods are alluring but deadly. They are fast predators and are always keeping an eye out for an opportunity to feast. Small fish such as soldier and squirrel fish remain in groups gathering close to the safety of the reef during the day. Among the coral shelter there are some more familiar inhabitants found in home aquariums around the world. This is the sea goldie and they live a rather stressful life on the reef. They are a favorite food for many predatory fish which means they have evolved some unique strategies to survive here. They form a social unit like a harem. The unit is comprised of a brightly colored male with several smaller pale orange females and juveniles. The male spawns with several females of his harem. In contrast to the anemone fish, if a predator takes the male sea goldie, the largest dominant female changes sex and color to take the place of the missing Romeo. This transformation can take just two weeks so the unit is able to swiftly replace the lost leaders. Losing a mate is not uncommon here even under the protection of deadly tentacles. Once every few years the coastal waters of the Isimangaliso wetland park are visited by a group of ancient wanderers. A bloom of jellyfish passes over the reef. This primitive flotsam has been drifting in the oceans of the world for over 500 million years. Closely related to permanently attached anemones, they spend most of their life floating in the water column in the shape of a transparent and gelatinous bell. Like the anemone they are a carnivorous species. They drag deadly tentacles behind them and feed on any victim that gets entangled. Jellyfish are simple marine creatures but have the ability to detect sunlight and depth while traveling in the open ocean. These marine wanderers display a magnificent underwater spectacle that can match any science fiction movie. They are not traveling alone. Some juvenile fish find refuge here never moving too far away from the gelatine fortress. Somehow they are able to tolerate stinging cells and reap the benefits of feeding on leftovers while they are commuting. Jellyfish are both beautiful and opportunistic creatures but they are also a good indicator of ocean health. Scientists are studying how to use these creatures as a natural warning system in our oceans. Many big groups of jellyfish may be normal but can also be the first signs of increasing water temperatures and overfishing of pelagic fish. One way or another these prehistoric and beautiful creatures continue to drift and adorn the oceans. The slow growth of these reefs over thousands of years has formed a diverse hidden world packed with hiding places. Fantastic underwater caves provide refuge for schools of fish to rest and hide. Smaller caves are home to some magnificent moray eels which sometimes get annoyed by inquisitive intruders. A cupped sponge becomes the perfect hiding place for a deadly ambusher. This is a frogfish able to eat a prey larger than itself and it can gulp a victim at a speed much faster than the strike of a cobra. Not far away another beautifully camouflaged ambusher is hunting. The scorpionfish. Turtles also visit the reef. This hawkbill turtle is looking for a snack as is this male parrotfish. Powerful beaks keep the reef and algae growth at Many fish know these special areas on the reef and they happily queue here for service. This is a cleaning station on the reef. Large rock cods visit these areas frequently to get rid of skin parasites or infected skin. This may sound disgusting but any leftover skin is a good meal for an army of marine creatures. After all in tropical waters food is not abundant and nothing is wasted. The service providers are rather small and could easily become a fish dinner themselves. But here advertising is the name of the game and everyone sends the right message. When large and threatening rock cods enter the zone the fish indicate that they mean no harm by changing their skin to bright colors. They also move gently and slowly open their mouths signaling that they are not looking for food but rather for a cleaning service. They enter slowly on the cracks that are crowded by flashy cleaner shrimps and tiny dancing cleaner fish all advertising their services. Once the large customer parks on the reef cleaning rapidly takes place with some competition for the best spot. Cleaner shrimp have no problem jumping on the client and they're even allowed to clean the most delicate parts. Some cleaner fish also use large and flat coral platforms to advertise and provide much needed services. This gentle beauty treatment of the large predator means a short break from the cat and mouse lifestyle on the reef. For many the best strategy to survival here is strength in numbers. A shoal moving over the reef forms a super cloud moving like a giant. Most large groups of fish do not visit cleaning stations but a few are able to sneak in for a quick cleanup. There is always a watchful eye and a large mouth nearby but sometimes romance can overwhelm appetite. This is a large shoal of blue banded snappers. They are moving slowly towards the edge of the reef searching for the sandy bottom. Joining the snappers are goat fish which are able to mimic the color and pattern of the snappers. So getting protection from predators seeking them out. For utmost protection it is best to blend in. Standing out from the crowd means predators can easily single you out as a tasty snack. Many eyes can keep predators at bay. Traveling in such groups also facilitates the finding of a mate and if attacked they can easily confuse a predator. The group increases the individual's survival. It has been suggested that lines and marks on shoaling fish help them to maintain visual contact with their neighbours to coordinate movement and take evasive action. The blue snapper's shoal can spend several hours hovering over the reef but a closer look near the sandy bottom reveals what they are really up to. Here under the cover of the massive floating wall fish take turns to rub themselves up against the sand occasionally finding the odd morsel to eat. This shoal provides effective protection on the reef but sometimes danger comes from the most unexpected places. This colourful mob of fish has discovered a breeding colony of sergeant majors. Some blue snappers also join in the party. The tenacity and aggression of the males is no match for the frenzy that quickly plunders the flat nesting site. But the sergeant major calls the cavalry for help. 220 volts delivered at once and it is all over. A marbled electric ray was waiting for this opportunity. In slow motion it is possible to see how the victim is completely paralysed by the powerful discharge of the electric organs. A second discharge is visible as fish scatter from the electric shock. Once the prey is paralysed it is swallowed whole and the ray once again disappears under the sand. Shoaling does not protect fish from such shocking weaponry. This magnificent coastal wetland park is an international hot spot for the protection of rare marine creatures. By protecting this mosaic of unique habitats both under and above the water we ensure that many creatures make a home in one of the last refuges on the African coast. From the air the magnificent and uninterrupted coastal dunes run parallel to the coast for hundreds of kilometres. The extensive sandy beaches here are free of human disturbance and these sands are one of the last and largest refuges for breeding marine turtles in the Indian Ocean. The park hosts the longest running leatherback and loggerhead turtle monitoring project in the world which started in 1963. Thanks to the visionary approach to protecting this coast this is one of the few places in the world where female turtles of both species can be seen breeding side by side. Only female turtles return to land when it is breeding season. This is the largest living turtle on our planet, the leatherback. A leathery skin covers its shell. They hold many records. They are huge and can weigh up to 700 kilograms each and they are accomplished divers with recorded dives below 1200 meters. They are also great travellers in the open ocean. The turtles prefer to hunt in colder waters for jellyfish but when it is time for breeding they come here to the warmer ocean. A large female such as this one may lay as many as nine clutches during a breeding season. Each clutch the size of about a hundred eggs. Eggs hatch in about 60 to 70 days and like any other reptile the temperature surrounding the nest determines the sex of each turtle. The nest temperature ranges from 26 to 32 degrees Celsius. A cold nest produces mostly males and females are the result of warmer nesting conditions. The extensive sandy beaches of Issy Mangaliso provide a safe breeding home for this gentle giant. The global impact of such coastal protection is immense. Leatherback turtles are now declared a critical endangered species. Few remain in the seas as many are caught in fishing nets and long lines in the open oceans. In spite of their flesh being full of highly toxic chemicals that result in many human casualties they continue to be eaten by people the world over. This part of Africa provides some hope for their survival but a larger protective umbrella is needed at international level to protect this has also allowed the reef to maintain a healthy and rich fish population. Spectacular groups of breeding ragged tooth sharks find safety in sheltered sandy reefs. Just like marine turtles the shallow waters are vital for them to complete their breeding cycle. This magnificent coast continues to give up more and more biological treasures and these are mostly found on the deeper reefs. In October 2000 a group of divers led by Peter Tim discovered the presence of coelacanth at a depth of 104 meters. Since this amazing discovery many diving expeditions have confirmed that there is a healthy population of this ancient fish which was presumed to have gone extinct over 400 million years ago. Today a long-term project on coelacanths in this park continues to reveal new insights into the life of the spectacular Lord of the Depths. Along the warm African coast there are few protected areas and this miracle wetland park is a shining beacon of hope. Here terrestrial and aquatic life is protected alongside human traditions for the future. By protecting this paradise we recognize the complexity and diversity of this region which makes it one of the most spectacular coastlines in the world. This is Africa's unmatched wonder shore that will continue to amaze and enchant explorers and visitors for generations to come.