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March 2008    Download the Entire Issue (PDF) Available to the Public Vol. 23, No. 3   RSS Feed for Undercurrent Issues
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Diversí and Snorkelersí Sunscreen Is Killing Off Coral

from the March, 2008 issue of Undercurrent   Subscribe Now

The sunscreen you dutifully put on before a dive or snorkel may prevent sunburn, but its chemicals are killing coral reefs worldwide. A study in the journal Environmental Health Perspectives states that four common sunscreen ingredients can awaken viruses in an algae called Zooxanthellae that lives inside reef-building coral species. The chemicals cause the viruses to replicate until their algae hosts explode, spilling viruses into the surrounding seawater, where they can infect neighboring coral communities. Zooxanthellae provides coral with food energy through photosynthesis and contributes to coralsí vibrant color. Without it, the coral bleaches white and dies.

The studyís researchers looked at the effects of sunscreen exposure on coral samples from reefs in the Pacific, Atlantic, and Indian Oceans. Seawater surrounding the coral exposed to sunscreen contained up to 15 times more viruses than unexposed samples. Researchers found that even low levels of sunscreen, at or below the typical amount used by swimmers, could activate the algae viruses and completely bleach coral in just four days. They estimate that 4,000 to 6,000 metric tons of sunscreen wash off swimmers, snorkelers and divers annually in oceans worldwide, and that up to 10 percent of coral reefs are threatened by sunscreen-induced bleaching.

Several brands of popular sunscreens were tested and all had four ingredients in common: paraben, cinnamate, benzophenone, and a camphor derivative. Banning sunscreen isnít necessary. To reduce their impact on coral, divers and snorkelers can use sunscreens with titanium dioxide and zinc oxide, which reflect instead of absorb ultraviolet radiation. Some eco-friendly sunscreens that meet those standards come from Caribbean Solutions ( and from Aubrey Organics (

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