Reefs

Coral reefs are Araonit structures produced by living organisms, found in marine waters with little to no nutrients in the water. High nutrient levels such as those found in runoff from agricultural areas can harm the reef by encouraging the growth of algae. In most reefs, the predominant organisms are stony corals that secrete an exoskeleton of calcium carbonite. The accumulation of skeletal material, broken and piled up by wave action and bioeroders, produces a massive calcareous formation that supports the living corals and a great variety of other animal and plant life. Tropical corals do not grow at depths of over 30 m (100 ft). Temperature has less of an effect on the distribution of tropical coral, but it is generally accepted that they do not exist in waters below 18 Degree Celcius.However, deep waters corals can exist at greater depths and colder temperatures. Although deep water corals also form reefs, very little is known about them.