It’s a very common sighting and many people wouldn’t consider going on holiday without it: sunscreen. An essential item for beach and sun lovers, but recently discovered to be harmful to the marine life.
Both lab and field experiments were conducted where researchers introduced various compounds found in sunscreen. They then measured the level of coral bleaching to determine the harmful effects to the reef.
As you might know, coral bleaching is a more common phenomenon these days. Corals actually consist of an animal part (the polyp) and symbiotic algae (zooxanthellae). The algae are much more important for the symbiosis than the polyps. Algae can account for up to 95% of the nutrition in the coral symbiosis.
If certain factors, such as water temperature, are altered, the corals may expel the algae, which only function in a very narrow temperature range. Consequently, as the coral loses up to 95% of their nutrition, it might eventually die.
Researchers have shown that the addition of sunscreen – even in small amounts – resulted in the release of zooxanthellae within 18 – 48 hours and complete bleaching within 96 hours. The researchers hypothesised that sunscreen compounds induced lethal viral infections in the corals that made them expel their essential algae.
As sunscreen applied to the skin (about 25%) will eventually end up in the water, the use of it should be carefully considered when undertaking any ocean activities.