Most coral reefs are located in tropical shallow waters less than 50 meters deep, in the western regions of the Indian ocean, Pacific Ocean and Greater Caribbean. Corals thrive best in tropical waters where temperatures range from 23 to 29 °C (73 to 84 °F); however, some corals are able to thrive in water temperatures below 18 °C (64 °F), and some have adapted to survive in more extremes temperatures. Coral reefs are not common along the western coasts of South America and the African continent. This is due primarily to the upwelling of colder ocean currents that reduce water temperatures in these regions.
The Indo-Pacific region
The Indo-Pacific region is the largest coral reef development in the world, covering a vast area of the Eastern Indian and Western Pacific oceans. The geological features of the Indo-Pacific region permit the formation of the three types of coral reefs, including fringing reefs, barrier reefs and atoll reefs. The greater variety of coral reef formations and biodiversity sets this region apart from other coral reefs in the world. The coral reef ecosystem of this region hosts the greatest marine biodiversity on Earth.
Approximately 700 species of coral and more than 3,000 species of fish have been discovered in the Indo-Pacific region and most of the marine life in this region is concentrated in a region, comprising western New Guinea, eastern Indonesia and southern Philippines. In this region the conditions are ideal for the abundance of marine biodiversity. Coral reefs situated farther from this region provide habitat for a fewer number of marine species. some regions of the Indo-Pacific still remain unexplored and new species of plants and sea animals still remain to be discovered.
This region extends along the Caribbean Sea, including south Florida to the north, Bermuda, The Bahamas and the northeastern coastal region of South America. The Caribbean region is where the second largest barrier, the Mesoamerican Barrier reef, is located. This coral reef barrier extends for 1,000 km (620 miles) from the Yucatan peninsula in Mexico to the Gulf of Honduras. The Caribbean region is dominated by fringing reef formation, including those formed off the coast of Cuba, the Bahamas and other smaller islands. The Caribbean includes a few atolls, the best known is the Glover's atoll reef which is located off the coast of Belize.
The biodiversity in the Caribbean coral reef ecosystem comprises approximately 65 known species of hard corals and an approximate number of between 500-700 fish species. The greater biodiversity in the Caribbean is found in the Mesoamerican Barrier Reef and the biodiversity decreases as the distance separates outer regions from this central region. Coral reefs in the Caribbean provide protection from hurricanes to many coastal communities. These coastal communities are also dependent on the coral reef ecosystem for subsistence.
Red Sea region
The Red sea coral reef ecosystem is located in the north region of the Indian ocean, between the Africa and the Arabian Peninsula, and extends for 2,000 km (1,240 miles) along the shoreline, which consist mostly of fringing reef formations. The water exchange between the Red Sea and the Indian ocean is minimum, allowing the development of unique characteristics which distinguishes this reef ecosystem from other reef ecosystems of the world. Coral reefs in the Red Sea have developed high tolerance to variations on water temperatures. The region around the Red Sea is one of the driest and hottest on Earth, producing high levels of evaporation and turning the Red Sea waters into some of the saltiest and hottest seawaters on Earth.
Coral reef biodiversity in the Red Sea is characterized by having a high endemism (are found nowhere else). From the approximate number of more than 1200 fish species, it has been estimated that about 10% species of fish found in this region are endemic. Approximately 300 species of hard corals have been found in the Red Sea. Unlike other coral reef ecosystems at the tropics, the coral reefs in the Red Sea have adapted to variable temperatures. The average surface water temperature in the summer is about 26 °C (79 °F) in the north and 30 °C (86 °F) in the south with a temperature variation of 2 °C (3.6 °F) during the winter.
The distribution of coral reefs around the world is determined by a group of environmental conditions in which the principal builders of coral reefs, hard corals, may thrive. Hard corals require warm, clear and shallow waters, such as those found in the tropics at 30 degrees north or south of the equator, although some species of corals can withstand other temperatures. According to Coral-Reef-Info.com, coral reefs are found in three world Oceans that have portions of water in the tropics; the Atlantic Ocean, the Pacific Ocean and the Indian Ocean.