Coral bleaching is when stressed coral reefs expel their zooxanthellae, which is a form of photosynthetic algae that lives in the tissues of the corals. This process reveals the coral’s underlying white skeleton. This makes them more vulnerable to any stressors, including diseases and storms, which may eventually cause them to die. Coral can become stressed due to a plethora of factors, including changing temperatures and pH levels. 

With increasing temperatures, the survival rate of coral reefs are negatively affected as these ecosystems need to be maintained at very specific conditions. From the year 1992 to 2019, the total heat stored in oceans has increased by 187 x 1021 joules. Such a significant change in the environment makes the coral drastically more stressed out, leading to the destruction of coral. It is projected that coral reefs would decline by 70% to 90% if average global air temperatures continues increasing. 

The acidity of the ocean can also affect the coral reefs. As the pH level of the water decreases due to pollution, the acidity goes up. This increased acidity weakens the exoskeleton of the coral because of its interference with the process of thickening the skeleton in order to better protect them. Consequently, the exoskeletons would be less dense and can be easily broken.