Photo Credit: AVRAM for ReefBase.org

This is a real kicker: Four commonly found sunscreen ingredients can awaken dormant viruses in the symbiotic algae called zooxanthellae that live inside reef-building coral species and kill them.

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 provide coral with food energy through photosynthesis and contribute to the organisms' vibrant color. Without them, the coral "bleaches"--turns 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.


The researchers estimate that 4,000 to 6,000 metric tons of sunscreen wash off swimmers annually in oceans worldwide, and that up to 10 percent of coral reefs are threatened by sunscreen-induced bleaching.

Hard to believe the reefer madness?

An example of how runoff is killing our oceans and seas is right on the US's Caribbean coastline. Fertilizers and animal waste have created a dead zone in the Caribbean sea the size of New Jersey.

Yet runoff is predictably not the only killer. An international team of 19 scientists have published the first ever comprehensive map showing the combined impact of human activity on the planet's seas and oceans. They have found that more than 40% of our marine environments have been either significantly altered by runoff, yes, but also by other factors such as fishing, ocean acidification, temperature change, species extinctions and invasions, and the shipping, oil and gas industries.

All these factors should put into perspective the decision not to use sunscreen and to look for alternative sun-protection methods. It's a choice our skin or the life of our oceans and seas.