The sunscreen we slather on to protect ourselves from the sun's harmful rays is doing incredible damage to the world's coral reefs.

A 2015 study found that just a small amount of sunscreen containing the ingredient oxybenzone is enough to break down coral, causing it to lose its nutrients, turn ghostly white or bleach and often die. The study was conducted in Hawaii and the U.S. Virgin Islands, reports the Washington Post, after a chance encounter with a vendor waiting for another group of tourists and the "long oil slick" of sunblock they would leave in their wake.

According to the National Park Service, 4,000 to 6,000 tons of sunscreen enters reef areas annually. But tourists at the beach aren't the only ones spreading harmful sunscreen chemicals to the coral reefs. Kids on playgrounds and athletes out for runs all come home and wash away the chemicals at home, and those chemicals can also end up being swept out to sea.

Not all coral reefs end up bleaching. Some become "zombie corals." These are corals that look like normal and healthy, but they just can't reproduce.

Research presented at the June 2016 International Coral Reef Symposium in Hawaii, studied 327 coral colonies off the coasts of Florida, Puerto Rico, and St. Thomas, St. John and St. Croix in the U.S. Virgin Islands to determine the reproductive potential of elkhorn coral, a threatened coral species that appears to be healthy.

In some locations, including the Florida Keys, the coral couldn't reproduce because it didn't have sperm or eggs. The researchers dubbed them "zombie corals," saying they were essentially walking dead and would eventually die out.

“It’s pretty discouraging,” said researcher John Fauth of the University of Central Florida, in a statement. “This is not good news.”

However, two samples from the St. Croix area had complete reproductive ability. “Basically the places with the heaviest tourism had the most severe damage,” said Fauth, who was also an investigator in the 2015 coral/sunscreen study and released another related study at the symposium. There, researchers found that oxybenzone is common in Hawaii, Florida and the U.S. Virgin Islands where concentrations peak during high tide.

“It’s almost counterintuitive,” said Fauth. “We think that aerosol sunscreen is to blame.” That's because when you spray sunscreen, a lot of it lands on the sand or in the water. When the high tide comes in, Fauth said, it collects all that overspray and pulls it out to sea.

The new studies show that coral reefs are in more danger than we thought.

So what's the solution?

The National Park Service encourages visitors to take a more "reef-friendly approach" to sun protection. Although no sunscreen has been found to be completely safe for coral reefs, those with titanium oxide or zinc oxide as the active ingredients haven't been found to harm corals. NPS rangers suggest covering up with hats, sunglasses and long-sleeved shirts or rash guards. And always remember: "If it’s on your skin, it’s on the reef."

Mary Jo DiLonardo Mary Jo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.