Hard like a stone and unable to move, most people do not know that corals are not plants or rocks but living animals. What is even more surprising is that they are actually many many animals living together in colonies because one coral animal (called a polyp) is very small; less than 0.5cm.
Each coral polyp lives in a hard cup-shaped skeleton and has a mouth that is surrounded by tentacles. The tentacles are used to filter plankton from the water, but most of their nutrients come from microscopic algae that live symbiotically in their tissue. Through photosynthesis, the algae use sunlight to produce nutrients for the corals. Corals get most of their nutrients from the algae and only a small proportion from plankton caught in their tentacles.
Despite their tiny size, corals are able to create massive structures known as coral reefs. They do this by secreting calcium carbonate which not only forms their cup-shaped skeletons but also creates the foundation of the coral reef ecosystem. Corals come in many different shapes and sizes and their skeletons build three-dimensional homes for millions of marine creatures. Many different types of animals live in corals, under corals and between coral branches. Coral reefs are not only important from a biodiversity perspective. They are also very important because they provide food, habitat and shelter to 25% of the world’s fish species and millions of people throughout the world rely on coral reef fish for food. Coral reefs also act as natural barriers and protect coastlines from wave damage and erosion.
Despite their hard skeletons, corals are fragile and can break easily. They are slow growing animals and damaged coral can take years to recover. Corals also do not like to be touched because they have a mucus layer that protects the polyps from disease. Care must be taken to avoid handling and walking on corals. (Check out our article here on what "not" to do while snorkeling)
Corals grow best in warm clear water with plenty of sunlight. In South Africa, these conditions are found along the Maputaland coast in northern KwaZulu-Natal. Here, corals have formed reefs rich in colour and life. The high coral cover on the reefs provides living space for a wide variety of fish species as well as other critters such as octopuses, nudibranchs, shrimps, giant clams, starfish and turtles. These coral reefs are rated among the top ten dive destinations in the world.
Corals can also be found in many rock pools from Sheffield beach down to Port Edward. The rock pools around Chaka’s Rock are particularly rich in coral diversity. Many of the rock pools are full of corals and the main tidal pool at Chakas rock has at least 15 different species of coral which is really remarkable. The forms and colours of the corals are very varied and range from pretty blue soft corals to pink and brown branching corals. They can easily be seen from the surface but their beauty is truly revealed when you put on a mask and snorkel and look closely at their delicate structure.