Sunscreens Promote Coral Bleaching by Stimulating Viruses

soft coral reef
Image courtesy of jon hanson via flickr

You may not realize this, but that sunscreen you typically slather your back with at the beach - though beneficial to you - does tremendous harm to coral reefs. According to ES&T's Robert Weinhold, 4 ingredients commonly found in sunscreens that tend to wash off into the water - a paraben preservative, cinnamate, benzophenone and a camphor derivative (the last 3 are UV filters) - cause bleaching by killing zooxanthellae, the algae that form a symbiotic relationship with corals - even at very low levels.

The team of Italian scientists that carried out the study observed that the noxious ingredients killed the algae within a span of just 4 days; they do so by stimulating viruses typically found in coral-inhabiting algae. They measured a 15-fold increase in the number of viruses surrounding the coral samples, many of which were also in and around the zooxanthellae.

They experimented on more than half a dozen species from various sites with a range of brands, SPFs and concentrations; in all cases, they found that the sunscreens bleached the corals. By their calculations, close to 10% of all of the world's reefs could be at risk from the 4,000-6,000 metric tons of sunscreen that wash off on an annual basis.

Via ::Environmental Science & Technology: Sunscreens go viral on coral (news website)