Coral reefs are often considered the “rainforests of the ocean” because they create great diversity. A selected type of coral controls this diversity and maintains a symbiotic relationship with plankton. Distinct types of plankton are called zooxanthellae. This symbiotic relationship between hosts and partners that use photosynthesis allows corals to soar in nutrient-poor seas and send calcium carbonate to the ocean floor to grow reefs (Toller et al. 2001). Coral bleaching This occurs when there is a decrease in zooxanthellae involved in the symbiotic relationship with their coral host. This also causes a loss of the coral's beautiful colors, sometimes visible to the human eye. Bleaching causes coral to die over time. Some causes of bleaching are linked to ocean salinity and sedimentation. The main known causes of severe coral bleaching are climate change and radiation. These two elements are extremely harmful to corals, especially when they work together at the same time (Fitt et al. 2001). There are two types of bleaching caused by zooxanthellae damage. The first is bleaching due to algal stress. Algal stress bleaching occurs when there is a discharge of zooxanthellae from a host cell. There is also another type called animal stress bleaching. Bleaching due to animal stress occurs when the host cell detaches, that is, the zooxanthellae leaving the coral with the host cell in which they live. These types of bleaching have only been observed when viewed under a microscope in the laboratory (Fitt et al. 2001). . There is also another type of whitening called physiological whitening. This usually occurs when shedding extra zooxanthellae. The density of zooxanthellae may increase or decrease...... middle of paper ......orals which are more severely affected (Marshall and Baird 2000). The vulnerability of fast-growing corals as they bleach has environmental consequences. The corals most vulnerable to bleaching are those that use space most quickly to colonize and only live for a short period of time. These corals dominate any open space and kill slower growing species. Bleaching is thought to influence coral reef diversity by preventing more aggressive corals from taking over (Marshall and Baird 2000). It is obvious that contradictory observations remain. The occurrence of coral bleaching will most likely be at the top of the list to watch for in the future. The importance of future findings on coral bleaching will help us understand the discrete effects of bleaching on the environmental well-being of coral reefs..