What is coral bleaching?

Coral bleaching is defined as the phenomenon where corals expel their symbiotic algae known as zooxanthellae, which provide corals with essential nutrients and their vibrant colors. This process is typically triggered by environmental stressors such as increased water temperatures, pollution, and changes in salinity. When under stress, corals lose these algae, leading to a stark white appearance, which is why it is termed "bleaching."

The expulsion of zooxanthellae disrupts the coral's ability to perform photosynthesis, severely impacting their health and nutritional intake. If the stress conditions persist, it may result in coral mortality, making understanding and mitigating coral bleaching critical for coral conservation and restoration efforts.

In contrast, the other options describe processes or states that do not accurately characterize coral bleaching. Coral reproduction involves the ways corals spawn or bud new polyps, while accelerated growth refers to how corals can increase in size under optimal conditions. Coral diseases involve infections or conditions that affect coral health, but they are distinct from the bleaching process, which primarily revolves around the loss of their symbiotic algae rather than an infection or pathological condition.