Threats to reefs: Coral reef bleaching

When corals undergo certain kinds of stress, much of the zooxanthellae – the symbiotic algae that provide coral polyps with nutrients – are expelled from the coral tissue. Ultimately, weakened corals may die. Bleaching is a frequent symptom of pollution-induced stress, as well as a response to natural factors such as changes in water temperature, salinity levels, and possibly ultraviolet light.[1] < p> During the El Ni