Up to ten per cent of coral reefs are threatened by bleaching caused by chemicals in sunscreens, according to Italian scientists

Between 4,000 and 6,000 tonnes of sunscreen wash off swimmers annually in oceans worldwide. Many popular brands contain ingredients that can stimulate viruses in the algae, known as zooxanthellae, that live within corals, say the researchers.

The scientists looked at the effect of sunscreen on corals in the Pacific, Atlantic and Indian oceans, and the Red Sea. They found that four sunscreen chemicals – parabens, cinnamates, benzophenones and a camphor derivative – cause the viruses to replicate until their algae hosts explode, spilling virus particles into the surrounding seawater, where they can infect neighbouring coral communities. Without the algae, the coral turns white and often dies.

‘Sunscreens cause the rapid and complete bleaching of hard corals, even at extremely low concentrations,’ said Roberto Danovaro of the Polytechnic University of Marche in Ancona, Italy, who led the research team. ‘By promoting viral infection, sunscreens can potentially play an important role in coral bleaching in areas prone to high levels of recreational use by humans.’

The researchers suggested that tourists use sunscreens that break down in the water, or that are free of parabens and the other chemicals identified as a problem.         

Mark Rowe

May 2008