Corals reefs are made up tiny individual coral polyps similar to sea anemones. These polyps secrete calcium carbonate which results in the formation of external skeletal structures referred to as reefs. The creation of coral reefs is a dynamic and intricate process involving continual coral polyp reproduction and the creation of a colorful and unique coral colony.
Coral reefs have a stony or rock like appearance due to the stone-like skeleton of each individual coral polyp. The skeleton is composed of calcium carbonate and is responsible for the form and shape of the reef structure. When a polyp lifts up from its base it will deposit a hard skeletal or calcium carbonate substance. This is why coral reefs grow in an upward direction. The hard skeletal substance deposited will then become a new base for young coral polyps to attach to and the cycle of detachment and skeletal deposit will begin again.
Coral reefs can be found in shallow water no more than 100 feet deep and lie between 30N to 30S of the equator. Water temperatures in areas where coral reefs are known to subside are usually 73F or warmer. A colony is composed of three zones including the base zone where coral polyps attach to a hard substrate such as a rock, the growing edge zone where the coral polyp asexually reproduce and the upper zone where light exposure occurs.
As the coral reef continues to grow it takes on one of three distinct formations or structures. These are categorized as fringing, barrier and atoll. This is the basis by which coral reefs are classified.
Fringing reefs are coral reefs that continue to grow in close proximity to the shoreline in shallow water. Barrier reefs are extremely large continually growing reefs that are separated from land areas by the existence of a lagoon. Atoll reefs are ring shaped reefs found toward the surface of the sea over various circular land masses such as inactive volcanoes or submerged islands.
The growth rate for coral reefs is extremely slow and it can take over 10 000 years for a colony of larvae to successfully form a visible and clearly defined reef. Barrier reefs can take even longer to form. The Great Barrier Reef is one of the largest natural structures on earth and it has taken thousands upon thousands of years to create the formation now hailed as one the seven natural wonders of the world.
Coral reefs are an amazing natural structure providing a unique habitat, feeding area and breeding ground for numerous species of marine animals, reptiles, fish and birds.