Corals can survive in clean water which have not pollutants and sediment. They smother corals cause decrease rate of the growth of algae, inhibit growth and reproduction of corals, change food structures on the reef and decrease quality of water. Nowadays researchers are trying to prove and find theories of the exact mechanism of sediment of which nutrients overload can affect corals. The sediment may add pathogens on corals tissue, provides the nutrient needed for existing pathogens to grow. Although, researchers cannot confirmed pollution and sediment is the cause, but this seems to be one of the factors that promote causes coral bleaching.