Corals
Have you seen soft jelly like structures deep under water, in a movie or pictures? You must have thought them to be marine structures as marine plants or rocks. But you are mistaken. These animals are called corals. They are marine invertebrates meaning, invertebrate animals that live in marine habitats.
They are made up of number of very tiny creatures called as 'polyps' that are connected together.
A polyp is a sac-like cylindrical animal. They are a few centimeter in length and a few millimeter in diameter. At one end, it has a mouth which is surrounded by organs called tentacles. With the help of tentacles they snatch food. Apart from small fish and planktons, corals also form their food by photosynthesis done by photosynthetic unicellular algae present in their tissues. The tentacles kill the prey using venom, a toxin, which is released when the tentacles are in contact with other organism.
Corals are reef builders. Reefs are underwater colonies of polyps. Stony corals are most important for this reef building.
A small coral swims under sea until it finds a suitable place to build a house. With the use of special glue like substance, it sticks to the rock or to another piece of coral. This starts the process of making the underwater colonies of reef. Over thousands of years, the colony formed by many generations creates a large skeleton like species. Calcium carbonate is the main compound which holds these colonies together. Warm, shallow and clear water is the best source for reefs. Coral reefs are earth's most diverse underwater ecosystem (Ecosystem is a community made up of living organism and non-living components such as air and water). They are just 0.1% of the total ocean area and still are the home for 255 of marine species.
There are different types of reefs such as --- fringing reefs and atolls. Charles Darwin first identified and classified them. The most known example of reef is The Great Barrier Reef. It is the world's largest coral reef system. Located in the Queensland, Australia, it consists of 2,900 individual reefs and 900 islands. It is spread over an area of approximately 3,44,400 square kilometres. It is the world's largest and biggest structure made up of living organisms. In 1981, it was declared as a world heritage site.
Apart from being home to many marine species, corals have other benefits and uses as well. The colonies are very rich in number of fishes and help the fisheries.
They are used in jewellery and medicines as well. They are used in the treatment of diseases such as cancers and HIV. Coral calx, known as Praval Bhasm is widely used to treat the calcium deficiency and bone related problems. Reefs are now a part of global tourism economy. Tourists across the globe visit the reef areas to explore the coral ecosystem. But due to heavy human intervention, reefs are under threat.
Over fishing, pollution, coral mining, global warming are few of the major threats to coral ecosystem. Almost 60% of the world's coral reefs are in danger due to human activities. People and governments of different nations started serious initiatives and took steps to protect this amazing ecosystem through Marine Protected areas (MPAs), Biosphere reserves, marine parks, national monuments world heritage status, fishery management etc.
