A study published in Environmental Health Perspectives journal found that ultraviolet filters in sunscreen cause viral infections in the algae that keeps coral healthy and bleaches hard corals. From the study authors found that sunscreen could play a damaging role in coral reefs, while some scientists say it's not a pressing issue.
The authors estimate that travelers release 4000 to 6000 tons of sunscreen into reef areas annually. Biodegradable sunscreen is a relevant option for beach goers that want to protect the environment. Jean-Michel Cousteau, son of the famous Jacques Cousteau and founder of Ocean Futures Society, promoted biodegradable products in Diver Magaine saying that ingredients in conventional sunscreen such as titanium dioxide and zinc oxide has the potential to harm sea life and precious coral reefs. However he wrote, that he "would not suggest that sunscreen products are the primary reason our reefs are collapsing", but "everything is connected".
Though overfishing affects almost all of the reefs worldwide and pollution is a huge issue, sunscreen is just one minor thing that swimmers can change in their vacation routine.
Some scientists believe that the sunscreen issue is not a major concern. Kiho Kim, professor of environmental science at American University in Washington DC said to The BBC, "while it's good to use products that are biodegradable, the issue with sunscreen is "probably not even on the radar of things people ought to be thinking about".
Some things travelers can do to help protect coral reefs is not buying coral jewelry and choosing sustainably harvested seafood. As far as reducing ones carbon travel footprint, it's important for travelers to look for hotels that are doing things to be ecologically friendly.
Kim added to the BBC, "Travelling is not particularly sustainable. If biodegradable sunscreen is part of the mix that's fine. But travelers, "shouldn't have the illusion that they're protecting the destruction of the coral".