Corals is limestone rock made by the accumulation of skeletons of tiny marine organisms called coral polyps.
Reefs are shallow, mostly submarine features, built primarily by colonies of living marine organisms, including corals, sponges, and shellfish.
Coral reefs occur only in the places coral polyps can survive and thrive.
The following are five conditions which favor occurrence of coral reef
coral reefs need to grow in shallow water where sunlight can reach them.
Corals depend on the zooxanthellae (algae) that grow inside of them for oxygen and other things, and since these algae need sunlight to survive corals also need sunlight to survive.
Corals rarely develop in water deeper than 50 meters since sunlight can not penetrate beyond this point.
corals need clean water that lets the sunlight through.
They do not thrive well in muddy like near river mouths. Sediments and plankton can cloud water which decreases the amount of sunlight that reaches the zooxanthellae
reef-building corals require warm water conditions to survive.
Different corals living in different regions can withstand various temperature fluctuations.
However corals generally in water temperature of 20 – 30 degrees Celsius, this is the reason why coral reefs appear on the eastern part of continents due to the presence of warm currents.
corals need salty water to survive and require a certain balance in the ratio of salt to the water.
this is why corals do not live in areas where rivers drain freshwater into the sea.
Corals in order to grow also need a plentiful supply of plankton and enough oxygen
This is important because like any other living organism coral polyps need food and oxygen so as to grow and be able to reproduce