The Unseen World of Corals

India is one of the most biodiverse countries in the world. When we think of this rich and unique variety of species, what comes to mind are creatures of the land. But there is another world that we often overlook. A world that is hidden from us. The Coral Reef. Surrounded by the Bay of Bengal, the Arabian Sea and the Indian Ocean, India has a coastline that borders the mainland and two island groups. This vast expanse spans 7,517 km and sustains diverse marine ecosystems. Coral reefs are mainly found in the Gulf of Kutch on the Gujarat coast, on the Gulf of Mannar and Pakpe, and along two archipelagos, Lakshadweep and Andaman and Nicobar Islands. The reefs along the Indian coasts are a mix of fringing or ring-shaped reefs which grow directly from the shore and barrier reefs that form a border along the coastline with a wide and deep lagoon separating them. A fringing reef forms around a volcanic island that sinks completely below sea level and when the coral continues to grow upward, it is called an atoll. Atolls are usually circular or oval with a central lagoon. India's only group of atolls lies on the 36 islands of Lakshadweep. Andaman and Nicobar Islands are home to 89% of India's coral diversity. So what are corals? They may look like underwater plants or rocks, but actually are complex combinations of countless tiny animals called polyps, algae and minerals. A coral is formed when free-swimming polyp larvae or planulae attach to submerged rocks or other hard surfaces along the edges of islands or continents. In a few weeks, the larvae mature into adult polyps. At night, polyps get more active and hunt prey swimming by with their tentacles. Polyps acquire calcium from the food they intake and deposit calcium carbonate to form its stony structure. Thousands of polyps come together to create structures that look like underwater plants permanently fixed in one place. Hundreds of thousands of diverse coral structures slowly form a coral reef. Corals are naturally white. Their vibrant colors come from a type of plant called zooxanthellae, an algae which finds a home inside each coral polyp. The algae and the coral rely on each other to survive. The coral provides the algae shelter and compounds necessary for photosynthesis. Apart from the color, the algae also gives the coral oxygen and feeds its sugars gained through photosynthesis. All corals are not hard corals that build skeletons of limestone around their polyps. There is an entire world out there of soft corals, black corals, sea fans, sea whips and sea pens. Also, there are corals that do not necessarily depend on zooxanthellae and can be found in dark, poorly lit waters. And there are sponges or anemones which grow on coral reefs but are not corals. So why are coral reefs important? Coral reefs cover less than 1% of the ocean floor, but they give shelter to 25% of marine life. They not only maintain the health of the ocean, but also protect our coasts from storms and erosion. They are a vital source of food and income for millions of people around our coast. They also give opportunities of reef tourism like snorkeling and scuba diving. We are losing our coral reefs at a steady pace. Corals are sensitive. A little increase in ocean temperature can cause coral bleaching, where the algae leave the corals, increasing coral mortality. Our oceans are warming at an alarming rate because of human-induced climate change. To add to this, marine pollution, marine debris, overfishing and anchoring are some of the key reasons for the destruction and bleaching of corals. The oceans cover nearly 71% of the Earth's surface. Healthy coral reefs lead to healthy marine life, which will in turn keep the rest of our planet healthy.