Coral bleaching is an event that causes coral reefs to lose their colors and slowly turn white. This event is triggered by the separation of hard coral and the photosynthetic algae living in a symbiotic relationship with them due to environmental stress. These tiny algae, called zooxanthellae, provide coral with their vivid colors. When the algae leave the coral, the coral loses its color.

One of the main reasons for this separation is the increase in water temperatures in the oceans due to global warming. Climate change, ocean acidification, and human intervention have caused significant damage to coral reefs around the world and led to their bleaching. The loss of reefs is already causing significant harm to the marine ecosystem. Researchers studying the period between 1957 and 2007 found that live coral cover on reefs had declined by approximately 50%. Coral cover in most countries has declined by up to 6.8% over the last decade.
Furthermore, there has been a decline in the ability of corals to perform crucial functions for the marine ecosystem, such as providing food and sequestering carbon.