The Hungry Snail, the Fragile Coral, and the Friendly Microbe

Off the coast of Vietnam, two recent events seem to have contributed to the death of coral reefs: the rapid invasion of a small marine snail called Drupella, and the emergence of a disease that spreads over corals. We decided to investigate whether there is a link between the corals, the snails, and the disease. We analyzed the mucus covering the surface of corals, both in healthy corals and those infested by Drupella snails. Mucus produced by corals is usually full of helpful microbes, protecting the corals from harmful microbes that can make them ill or kill them. Our analyses showed that, when Drupella eats corals, the snail also removes one of the corals’ primary defenses by eliminating most of the tiny protectors in their mucus. This allows harmful microbes to cause additional damage to the corals.