Some Sunscreens Kill Coral

Coral reefs are one of nature’s most spectacularly beautiful sights. At home in shallow tropical waters, these living organisms are well known to divers and David Attenborough fans. They are fragile, and even small disruptions in their environment can have catastrophic consequences. Now it appears that sunscreens might be one of those disruptions.

Researchers from Pisa, Italy found that some sunscreens, even at low concentrations, can cause complete and permanent bleaching of coral reefs.

Brilliantly colored algae live in coral reefs providing nutrients to the coral by photosynthesis. The algae make the spectacular colors for which corals are known. When the algae die, the coral cannot obtain nutrients from the nutrient-deprived tropical waters and subsequently die. Bleached coral is dead coral.

The Italian researchers collected coral from various oceans and incubated them in water that contained minute amounts of sunscreen. They found that the sunscreen induced viral infections in the algae, killing the algae and bleaching the coral.

The researchers found that four commonly found sunscreen ingredients — paraben, cinnamate, benzophenone, and camphor derivatives — were the offending culprits.

Although only about 10% of coral reefs are threatened by sunscreens, that number is significant and could rise as the number of reefs visited by tourists increases each year.

About 25% of the sunscreen’s ingredients are released into the water within 20 minutes leading to 4,000 to 6,000 tons of sunscreen released annually in reef areas.

One possible solution: choose a sunscreen that uses zinc oxide and titanium dioxide rather than chemical sunscreens. Zinc and titanium are excellent broad spectrum sunscreen ingredients and are not included on the list chemicals know to bleach coral.

Post written by Jeffrey Benabio, MD. You might also like:

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Photo credit: Mike Baird, Belize

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