Specifically, what researchers found was that four commonly found sunscreen ingredients have the ability to awaken dormant viruses in the symbiotic algae called zooxanthellae that live inside reef-building coral species. The chemicals then cause the viruses to replicate until their algae hosts explode, spilling viruses into the surrounding seawater, where they can spread out to infect neighboring coral communities.

How could sunscreen make any difference in such a vast ocean? The amount of sunscreen involved is probably larger than most of us would guess. An estimated 4,000 to 6,000 metric tons of sunscreen wash off swimmers bodies annually