‘Coral Zombies’ linked to sunscreen pollution

A group of scientists at the University of Florida has been conducting research into the potential for healthier looking coral reefs to repopulate flagging colonies, but evidence is pointing to the widespread appearance of sterile corals that point to even bigger challenges for any recovery effort.

And the researchers also say that it is areas where tourism and, in turn, sunscreen pollution is at its highest levels, where the highest incidence of these coral zombies was found.

'Not good news'​

"It's pretty discouraging,"​ said University of Central Florida biologist John E. Fauth, one of the researchers who sampled 34 sites across the Caribbean for the study. "This is not good news."​

The findings of the study were revealed at the 13^th​ International Coral Reef Symposium, held in Honolulu last week, and point to an even grimmer future for coral reefs than previously predicted.

The study was led by Cherly M. Woodley, a marine biologist at NOAA’s National Ocean Service, and sampled 327 coral colonies off the coasts of Florida, Puerto Rico and the US Virgin Islands.

Areas of high tourism worst affected​

On analysing the coral samples, the team found that in some places in the Florida Keys, the coral had no eggs or sperm – rendering it sterile and pointing to elkhorn coral eventually dying out in those spots.

This contrasted starkly to more remote parts of the Virgin Islands, where the corals still had full reproduction ability, underlining the fact that the areas with the most tourism and human activity were those where the corals were most affected .

The study links with a 2015 that underlined how high levels of oxybenzone from UV-filtering compounds in sunscreens has had a direct impact on corals near tourist beaches.

Scientists say oxybenzone is the culprit​

That evidence highlighted how oxybenzone kills corals and also causes DNA damage in adult corals, while simultaneously deforming it at the larva stage, severely impacting future growth, while also bleaching the corals.

"It's almost counterintuitive," said Fauth, who is a co-author of that study as well. "We think that aerosol sunscreen is to blame."​ Fauth adds her belief that when sunscreen is sprayed, much of it lands on the sand or water. So when the high tide comes in, it collects all the overspray and pulls it back out to sea.

In both the presentation and the published study, the researchers have hammered home the message that something needs to be done to stem the damage, suggesting that individuals can help fight the problem by wearing rash guards or going without sunscreen during dives.