Sunscreen chemicals cause coral bleaching

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Italian scientists have found that ingredients in sunscreen can hasten coral bleaching by promoting viral infections in the symbiotic algae (zooxanthellae) in the coral.

The study, to be published in the journal Environmental Health Perspectives, was conducted by Roberto Danovaro, Lucia Bongiorni, Cinzia Corinaldesi, Donato Giovannelli, Elisabetta Damiani, Paola Astolfi, Lucedio Greci and Antonio Pusceddu of the Polytechnic University of the Marche.

The authors used in situ and laboratory assays by supplementing coral branches with small quantities of sunscreens and common ultraviolet filters contained in sunscreen formulas.

The assays were conducted on Acropora spp. and the in situ studies were carried out in four coral reef areas: Siladen, Celebes Sea (Indonesia, Pacific Ocean); Akumal, Caribbean Sea (Mexico, Atlantic Ocean); Phuket, Andaman Sea (Thailand, Indian Ocean) and Ras Mohammed, Red Sea (Egypt, Indian Ocean).

The researchers found that in all replicates and at all sampling sites, sunscreen addition even in very low quantities (about 10 microlitres per litre of seawater) resulted in the release of large amounts of coral mucus (composed of zooxanthellae and coral tissue) within 18"48 hours, and caused complete bleaching of hard corals within 96 hours.

They identify the following ingredients in sunscreen as being the responsible agents of death: butylparaben, ethylhexyl methoxycinnamate, benzophenone-3 and 4-methylbenzylidene camphor, and conclude that ...sunscreens containing parabens, cinnamates, benzophenones and camphor derivatives can contribute to hard-coral bleaching if released into natural systems.

These agents are organic UV filters that are able to induce the lytic viral cycle in symbiotic zooxanthellae with latent infections, causing death of the coral.

The authors estimate about 4,000-6,000 tons of sunscreen are released per year in reef areas worldwide. They also estimated that up to 10% of the world reefs is potentially threatened by sunscreen- induced coral bleaching.

For more information, see the paper: Danovaro, R, L Bongiorni, C Corinaldesi, D Giovannelli, E Damiani, P Astolfi, L Greci and A Pusceddu (2008) Sunscreens cause coral beaching by promoting viral infections. Environmental Health Perspectives doi:10.1289/ehp.10966