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How Chemical Sunscreen Effects Coral

Between 6,000 and 14,000 tons of sunscreen wash off swimmers, scuba divers, and snorkelers into coral reef environments each year. Even more sunscreen pollution can reach coastal areas via waste water discharges. Up to 10% of the world’s coral reefs may be threatened by certain chemicals found in most sunscreens.

Healthy coral reefs are one of the most valuable ecosystems on Earth. They provide billions of dollars in economic and environmental services, such as food, coastal protection, and tourism. However, coral ecosystems around the world face serious threats from a number of sources, including climate change, unsustainable fishing, land-based pollution, coastal development, disease, and invasive species.

Oxybenzone is a common ingredient in sunscreen that disrupts coral reproduction, causes coral bleaching, and damages coral DNA. Oxybenzone is found in over 3500 sunscreen products worldwide. Octinoxate is another common sunscreen ingredient shown to cause coral bleaching.

Coral bleaching (the release of coral symbiotic zooxanthellae) is an increasing world-wide phenomenon which is associated with temperature anomalies, high irradiance, pollution, and bacterial diseases. Recently, it has been demonstrated that personal care products, including sunscreens, have an impact on aquatic organisms similar to that of other contaminants.

Sunscreens cause the rapid and complete bleaching of hard corals, even at extremely low concentrations. The effect of sunscreens is due to organic ultraviolet filters, which are able to induce the lytic viral cycle in symbiotic zooxanthellae with latent infections.

These compounds are expected to be potentially harmful for the environment; hence, the use of sunscreen products is now banned in a few popular tourist destinations, for example, in marine ecoparks in Mexico, and in some semi-enclosed transitional systems.

In a study published by NCBI, which tested the affects of sunscreens on the loss of zooxanthellae in corals, researchers found that sunscreen addition even in very low quantities resulted in the release of large amounts of coral mucous (composed of zooxanthellae and coral tissue) within 18–48 hr, and complete bleaching of hard corals within 96 hr. Different sunscreen brands, protective factors, and concentrations were compared, and all treatments caused bleaching of hard corals, although the rates of bleaching were faster when larger quantities were used. Bleaching also occurred at a higher rate in warmer temperatures, which from the overall sea temperature rise this is become an increasing issue. All these results indicate that sunscreens have a rapid effect on hard corals and cause bleaching by damaging the symbiotic zooxanthellae.

Scientists have also discovered that some of the chemicals found in sunscreen and other personal health products threaten the health of coral reefs. How these, and other compounds, affect reef ecosystems remains an active area of research. Researchers are reviewing the environmental impacts of sunscreen ingredients as part of a National Academy of Sciences study expected to be completed in 2022. NOAA will review this study when it is available and update the information presented in this article as warranted.