In this article it looks at the Coral Bleaching that is happening in the great barrier reef. Coral bleaching occurs when the waters are too warm and the coral releases the algae that gives the coral its color. This can be fatal for the coral if the bleaching is too intense or happens for a prolonged period of time. If this happens then the algae will not be able to recolonize the coral. The impact this poses it very large. The great barrier reef is one of the largest coral reef in the world covering 134,364 square miles. At this point they are expecting about a 50% mortality rate for the bleached coral. The main factor scientist have come up for the bleaching of the coral is the past years El Niño.