All about coral reefs [1]

What is a coral reef?

Coral reefs are the most biologically diverse marine eco-systems on earth, rivaled only by the tropical rainforests on land. Corals grow over geologic time and have been in existence about 200 million years. Corals reached their current level of diversity 50 million years ago.The delicately balanced marine environment of the coral reef relies on the interaction of hard and soft corals, sponges, anemones, snails, rays, crabs, lobsters, turtles, dolphins and other sea life.

References: http://www.reefrelief.org