Coral reefs are having a rough go over the last few decades and in a worst-case scenario, scientists were counting on large, healthy-looking corals to repopulate.
But it turns out these seemingly healthy colonies are "Coral Zombies" with no reproductive ability, which makes them useless in a recovery effort.
University of Central Florida biologist John E. Fauth, who sampled 34 sites across the Caribbean for a recent study, said "It's pretty discouraging. This is not good news."
The study, led by Cheryl M. Woodley, sampled 327 coral colonies off the coasts of Florida, Puerto Rico, and St. Thomas, St. John and St. Croix in the US. The researchers analyzed the samples to determine the reproductive ability of elkhorn coral (Acropora palmata), which is a threatened species.
In some places - including two sites in the Florida Keys - the coral had no eggs or sperm. The study suggests that with no ability to propogate, elkhorn corals in those spots will eventually die out - like zombies, they essentially are walking dead. Two samples from a more remote area in St. Croix found the coral had 100 percent reproduction ability.
"Basically the places with the heaviest tourism had the most severe damage," Fauth said. He dove and took samples from all of the Puerto Rican sites in the study, along with marine biologists Michael Nemeth and Katie Flynn.
This study adds to growing evidence that coral reefs frequented by divers are in peril.
The study has been presented at the 13th International Coral Reef Symposium in Honolulu.