Damaged Reefs or Sunburn?: corals threatened by sunscreen use

Many people, even those with only a passing interest in ocean conservation, know that many of the world's coral reefs are being threatened by a variety of environmental impacts. Ocean acidification, pollutants, runoff from urban development, and increasing water temperatures are having their effect, usually in the form of coral bleaching. Corals are supported in a symbiotic fashion by zooxanthellae, algae embedded in the very tissues of the coral. When environmental conditions are not right, the algae dies off and the weakened coral loses its color and starts a slow decline that can often lead to death.

With each summer, as tourism swells and swimmers, snorkelers, and divers entire the water, another threat takes aim at these beautiful but fragile marine ecosystems. And it is an unusual and seemingly unlikely danger. Sunscreen.

That's right. The very stuff that keeps you from looking like a lobster right out of the pot, is also a proven danger to coral. The effects of sunscreen on coral has been the subject of several studies over the past several years. One of the most revealing was conducted in 2008 and published in Environmental Health Perspectives. Researchers from Italy's Polytechnic University of Marche Region, studied the effect of several sunscreen compounds on corals in a controlled laboratory setting and found that four common ingredients caused dormant viruses in the zooxanthellae to awaken and replicate, killing the zooxanthellae and spilling into the surrounding water to do more damage to other corals.

The four ingredients - paraben, cinnamate, benzophenone, and camphor derivatives - are found in many leading brands of sunscreen. The research showed that even very small amounts of these compounds can induce coral bleaching in as little as four hours.

But really, how much of a threat can this be? The World Trade Organization (WTO) has some numbers to illustrate the problem's potential. Ten percent of all tourism takes place in tropical areas, amounting to approximately 80 million people visiting coral reefs annually. With that, the WTO estimates that as much as 6,000 tons of sunscreen lotions are released in reef areas each year, putting as much as 10% of the reefs at risk of death by sunscreen.

You can check your sunscreen label for the chemical culprits or look for sunscreens that are labeled as "coral or reef-safe." No one is suggesting that you fry in the sun and spend your later years in the dermatologist's office, dealing with skin damage. But by reading labels and purchasing sunscreen known to be safe for corals, you'll be taking a personal proactive step to protect coral reefs - while we focus worldwide efforts on the other challenges to the ocean's colorful undersea gardens.

Read a summary of the study in Environmental Health Perspectives.
Read more about coral death by sunscreen in National Geographic News.