Scientists Discover What's Destroying Fragile Coral Reefs: Tourists' Sunscreen

A new study has identified an elusive culprit behind the lethal bleaching of coral reefs worldwide. The popular sunscreens that tourists slather on before a dip in the ocean contains chemicals that quickly kill off fragile reefs.

Specifically, what researchers found was that four commonly found sunscreen ingredients have the ability to awaken dormant viruses in the symbiotic algae called zooxanthellae that live inside reef-building coral species. The chemicals then cause the viruses to replicate until their algae hosts explode, spilling viruses into the surrounding seawater, where they can spread out to infect neighboring coral communities.

These symbiotic algaes, called Zooxanthellae, are what provide coral with food energy through photosynthesis and contribute to the organisms' beautiful colors. When then die off, the coral "bleaches” white and dies.

"The algae that live in the coral tissue and feed these animals explode or are just released by the tissue, thus leaving naked the skeleton of the coral," said study leader Roberto Danovaro of the Polytechnic University of Marche in Italy.

How could sunscreen make any difference in such a vast ocean? The amount of sunscreen involved is probably larger than most of us would guess. An estimated 4,000 to 6,000 metric tons of sunscreen wash off swimmers bodies annually in oceans around the world. While sunscreen isn’t the only factor behind declining reefs, it has a big impact. It is also estimated that up to 10 percent of coral reefs are directly threatened by sunscreen-induced bleaching.

Danovaro and his team studied the effects of sunscreen exposure on coral from reefs in the Pacific, Atlantic, and Indian Oceans. They 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.

According to study author Danovaro, the effect is not dose dependent—so coral's exposure to a very small dose of sunscreen is just as dangerous as a high exposure.

"It is more like on-off," he said. "Once the viral epidemic is started, it is not a problem of toxicity."

They found that seawater surrounding coral exposed to sunscreen contained up to 15 times as many viruses as unexposed samples. Several brands of popular sunscreens were tested. All of them were found to have four ingredients in common: paraben, cinnamate, benzophenone, and a camphor derivative.

Fortunately there are ways around the problem. Danovaro says banning sunscreen from beaches altogether isn’t necessary. He says swimmers can reduce their impact on coral by using sunscreens with physical filters, which reflect instead of absorb ultraviolet radiation, or they can choose sunscreens that use eco-friendly chemical sunscreens. Australian researchers are also currently working to develop eco-friendly sunscreens based on a natural ultraviolet-blocking compound already found in coral naturally.

Posted by Rebecca Sato

* This study appeared online in the journal Environmental Health Perspectives.

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Story link:
http://news.nationalgeographic.com/news/2008/01/080129-sunscreen-coral.html

Comments

[Linda]

Sunscreen also cause a problem with people with reactive airways disease. Last summer I had to rush home after sitting at the pool breathing sunscreen, spent the night vomiting, migraine, etc. Linda

[Michael]

I was recently in Hawaii, the hotel gave me a reef-friendly product called burn b gone which contains no sunscreen but was quite effective in keeping me from getting burnt while snorkeling in the coral reefs.