While corals may look like rocks and share several characteristics of plants, they are in fact animals. To be exact they are aquatic marine invertebrates (known as polyps) that live in the warm shallows of the clear coastal waters around the world. A huge number of marine organisms make their home among the corals, making reefs some of the most abundant and varied habitats on Earth. Corals live in partnership with single-celled zooxanthellae algae. If the algae die the coral will turn white, a damaging effect known as coral bleaching.
The large coral reefs seem to be the oldest living animals in the world. Their longevity is 541 to 485.4 million years. However light and temperature are necessary conditions for the survival of corals, the temperature must be between 25 and 30 °c. If the temperature rises or if the light is too intense for a long time, corals whiten this translates into dieback. This bleaching could become colored again if the conditions return to normal in a short time.
Coral reproductive methods vary according to the species. Some species, such as brain and star corals, are hermaphrodites, meaning they produce both sperm and eggs at the same time. Other corals, such as Elkhorn and boulder corals, are gonochoric, meaning that they produce single-sex colonies. In these species, all of the polyps in one colony produce only sperm, and all of the polyps in another colony produce only eggs. Other species of coral reproduce by ejecting large quantities of eggs and sperm into the surrounding water. When this happens, the eggs and sperm fertilize in the water. This process is called coral spawning.
Corals are the fundamental elements of reef construction. They are both supports, shelters and food. Their forms offer a protective refuge to many species. Indeed, the health of fish is due in large part to the presence and good health of the reefs. Coral reefs also represent a source of sandy sediments feeding on coral sand beaches. Their presence is a support for many cultural and leisure activities. Coral reefs have 4000 species of fish, 700 species of corals, and thousands of other plants and animals, scientists estimate that, in total, more than one million species of plants and animals are associated with the coral ecosystem. Coral reefs are a bulwark against the violence of the sea; Their role as natural protection of the coasts is crucial. Particularly in the southwestern Indian Ocean region where the southern swells and cyclonic swells are present. The protection of coral reefs also has an economic interest for all tourists, leisure and commercial activities that take place (Scuba diving, sliding sports, glass-bottomed boats, professional fishing and more extensive sightseeing tours to beach hotels and restaurants).
Coral reefs are found in more than 100 countries around the world. Most reefs are located between the Tropics of Cancer and Capricorn, in the Pacific Ocean, the Indian Ocean, the Caribbean Sea, the Red Sea, and the Persian Gulf. But only tropical and subtropical corals form large barriers and reefs at shallow depths. In fact, algae present in their tissues (zooxanthellae) need light for photosynthesis and prefer water temperatures between 22 and 29 °c. Hard corals and soft corals can be found in deep seas.
Stretching over more than 2 300 km of shallow waters off the Australian northeast coast, the Great Barrier Reef of Australia is the largest marine park in the world. An extraordinary diversity of species evolves in these tropical waters, including 400 types of corals, 1 500 species of fish and 400 kinds of molluscs. Boats transport divers between the shore and the reef. The Belize Reef Barrier is the second largest in the world after the great coral barrier of Australia. The reef barrier is about 300 kilometers long and 40 kilometers offshore at its largest distance from the shore, but only 300 meters to its nearest point. The atolls are located off the barrier and offer extraordinary dive. The translucent waters surrounding the Andros archipelago in the Bahamas offer an ideal diving setting. The corals extend over 225 km along the east coast of Andros, until the end of the “Tongue Ocean”. An oceanic trench whose depth falls from 35 m to 1 800 m.
Coral reefs are also being degraded by many other factors. The increase in demand for fish has led to overfishing of reef species. Overfishing of some species can easily affect the ecological balance and biodiversity of the reef. For example, overfishing of herbivorous fish can lead to high levels of algal growth asphyxiating the current coral. Tourism generates large amounts of income for the host countries. When not regulated, tourism pressures can cause damage to the surrounding environment: Careless divers, boat anchors, hotels evacuating untreated wastewater. Coral reefs need mineral-poor water to grow. Over the past 10 years, the incidence of diseases developed in corals appears to have increased. This contributes to the deterioration of coral reef communities around the world.
In order to protect the corals that are very sensitive animals you should avoid hitting them with your boat, touching them with your fingers or stepping on them because its mucus that protects it is destroyed. Do not sail, anchor or fish nearby as this can seriously damage a coral reef to the point of causing death. It is important not to pollute by throwing objects or wastes on a beach. When you dive, it is necessary to follow the rules such as not to pluck the reefs to take them away. There are associations that you can subscribe to protect coral reefs such as Acroporis, Coral Gardening, Coral Guardian which propose to clean the coastlines in order to avoid pollution or the destruction of coral reefs.