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)