FEBRUARY 9, 2008—Common ingredients in sunscreen activate dormant viruses in algae that cause the algae to explode and kill the coral beds they feed.

Additionally, when the algae explodes, it releases the virus into nearby coral beds.

The algae provides the coral with food energy through photosynthesis. Without the algae, 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,” study leader Roberto Danovaro of the Polytechnic University of Marche in Italy told National Geographic.

Swimmers leave 4,000 to 6,000 metric tons of sunscreen in the world’s oceans worldwide, threatening about 10 percent of the world’s coral, the study published in the journal Environmental Health Perspectives found.

Even low levels of sunscreen can trigger the virus, which can decimate a coral bed in as few as four days.

The study showed that seawater around the infected coral beds was 15 times more likely to contain the algae-killing virus.

Paraben, cinnamate, benzophenone and a camphor derivative are the common sunscreen ingredients found to activate the virus.

While signs point to banning sunscreen for oceangoers, Danovaro said that won’t be necessary. There are two things swimmers can do to reduce their impact on coral: One, choose a sunscreen that reflects rather than absorbs ultraviolet radiation; two, use an eco-friendly sunscreen.

Researchers in Australian are hard at work on a sunscreen based on a natural ultraviolet-blocking compound found in coral.