The researchers  investigated the effects on coral of adding controlled amounts of three brands of sunscreen and common ultraviolet filters to the surrounding seawater. They conducted in vitro and in situ experiments in several tropical regions: the Atlantic, Indian, and Pacific Oceans, and the Red Sea. Even when sunscreen was added in low quantities, large amounts of coral mucous, composed of algae and coral particles, were released within 18-48 hours. Within 96 hours, complete bleaching of corals had occurred.
Coral reefs are among the most biologically productive and diverse ecosystems. However, they also appear as being among the most sensitive and are particularly affected by marine pollution and climate change. Sunscreens may act in synergy with other chemical pollutants that have also been pointed out for their negative impact on coral’s health.
According to the Italian researchers, up to 10% of the world coral reefs are potentially threatened by sunscreen-induced coral bleaching. They estimate to 4,000-6,000 tons the amount of sunscreen that tourists dilute in the seawaters in reef areas every year.