This is through a process of slow deposition and accumulation of limestone removed from seawater. Stony corals and coralline red algae grow among the coral colonies. Limestone is used for the outer part of coral polyps and hardening the fleshy parts of the coralline algae. After organisms die, they leave the limestone skeletons. The reef-building process is very slow, it takes decades to centuries. Coral reefs start to form when coral larvae attach to hard surfaces such as submerged rock along edges of continents or islands. As corals expand and grow, reefs adopt one of the characteristic structures. An atoll forms if a fringing reefs forms around a volcanic island that subsides under sea level as coral grows upward. They are usually circular or oval and have a central lagoon. Barriers and atolls are some of the oldest habitats in the ocean. Coral reefs are found in over a hundred countries. Most are found between the Tropics of Capricorn and Cancer, in the Indian and Pacific Ocean, Red Sea, Caribbean Sea and the Persian Gulf. They are also found farther from the equator, where warm currents flow out of the tropics like Southern Japan or Florida. They cover about 110,000 square miles. The largest is the Great Barrier Reef which is in Australia. The second largest is in …show more content…
The first one is protection for beaches, communities and coastal cities. The next one is food for people living close to the coral reefs. They provide potential treatments for many people. The next one is a habitat for over one million aquatic species. This includes thousands of fish. The last one is income. This includes over a million jobs and thousands of dollars in over one hundred countries. Coral reefs have a lot of threats. The biggest one is weather related. Cyclones and hurricanes can flatten large coral heads or break apart. This scatters their fragments. A single storm kills a whole colony. Another threat is tidal emersions. Long periods of very low tides leave shallow coral heads which damages reefs. The amount of damage has to do with weather conditions and time of day. If it is daylight, corals are subjected to the most ultraviolet radiation. This can dry out and overheat the coral tissues. The last threat is predation. Some of the preys are sea stars, fish, sea worms, snails and crabs. Entire reefs can be destroyed in this type of predation. About 90% of coral were destroyed when a huge outbreak of crown of thorns starfish attacked at the Fagatele Bay National Marine Sanctuary in Florida. Coral reefs could recover from traumas that are caused by weather or other natural causes. If they have numerous traumas, they will eventually