A dangerous new threat to coral reefs might be the fault of cruise ships. A peer-reviewed study suggests ships that improperly dispose of wastewater are causing outbreaks of an unusually lethal and fast-spreading disease known as stony coral tissue loss disease, reports the Guardian. SCTLD first turned up in Florida in 2014 but has since become widespread in the Bahamas and in 18 other countries. The new study focused on the Bahamas, where researchers picked up on a telltale clue: The disease was worse near shipping ports, per the Cayman News Service. While cruise ships have rules that prohibit them from dumping wastewater in the vicinity of reefs, enforcement isn't easy.
"If ballast water was taken on board in a port area where SCTLD was present and not exchanged in open water away from reefs as required in The Bahamas, ballast water may have been the means by which SCTLD reached the Grand Bahama area,” notes the study in Frontiers in Marine Science. At this point, scientists know little about the disease, including whether it's caused by bacteria or a virus. So far, the most effective treatment appears to be an antibiotic, suggesting bacteria is the culprit, reports IFL Science. Regardless, given yet another threat to already besieged coral reefs, scientists say the study demonstrates the need for early detection and suggests that "preventing the spread of the disease between islands via vessel traffic is of utmost importance." (Read more coral reefs stories.)