Which environmental factor determines why coral reef populations are found only in shallow waters?

Corals are the important part of marine ecosystems. They are found in both deep water and shallow water. However, coral reef are found in shallow water. The environment factor on which coral reef is depends is the presence of sunlight. In shallow water where sunlight can reach because corals depend on algae zooxanthellae. These algae grow inside them and provide oxygen for them through photosynthesis. Besides coral need clear warm water to grow which is present in the shallow region of an ocean.

from my research i have to the conclusion that decomposers, such as fungi, bacteria and invertebrates, play a critical role in nutrient cycling and without them the earth's ecosystem may not support life as we know it. elements such as carbon, nitrogen and phosphorus exist in limited amounts on earth, although huge amounts of carbon are being released into the atmosphere from underground sources now by humans. it is still extremely important that other nutrients be retained by the process of re-use. decomposers are organisms that are able to chemically break down dead material and make these elements available for use by other organisms. without this breakdown of dead material, dead bodies would pile up. so decomposers also play a role in clean up also. without them, life might not continue as we know it and dead material would overwhelm the earth.    

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