A coral reef can have several or several thousand different types of coral, ranging from the very exotic to the very common live coral. You can have your own little piece of coral reef in your very own home. There are over 500,000 species in the 600,000 square miles of coral reef throughout the world. Live coral is helpful for many different underwater species. Different types of fish, eels, sponges, grasses, algae, mollusks, crabs, worms, etc. use the coral reef as home or as nurseries for their young. While the coral reef is a useful home for many species, it is an exotic and fun thing to look at and observe for humans. Anyone can enjoy the natural phenomena of the coral reef. They can be seen in their natural habitat or in your very own home.
Even after the live coral dies, it leaves its skeletons made of calcium carbonate behind. This gives a home to new live coral to plant themselves to and provides nice crevices for other species. There are three different levels of coral reef: fringe, barrier, and atolls. The fringe coral reef is found near shore and is separated from land by low water. Reefs that are at least 10 kilometers away from land are called barrier reefs. A circular coral island that is far away from land is called an atoll. Atolls happen to be a unique type of coral reef. They form when coral develops on a volcanic island that has sunk below the water. It can take years before any type of coral reef grows. In fact, it may take up to 100 years for an inch of coral reef to grow. This is one of the reasons that the coral reef is such an exotic thing to see in nature.
