I’m Gonna Soak Up the Sun: Sunscreen’s Impact on Coral Communities

Paper: Occurrence, Distribution, and Fate of Organic UV Filters in Coral Communities. Mirabelle M. P. Tsui, James C. W. Lam, T.Y. Ng, P. O. Ang, Margaret B. Murphy, and Paul K. S. Lam Environmental Science & Technology 2017 51 (8), 4182-4190, DOI: 10.1021/acs.est.6b05211

Got my 45 on so I can rock on

Even though winter in New England has been mild, I’m ready for some sunny beach days! I try my best to avoid sunburn but, without fail, the first nice day I get too much sun. I spend the rest of summer wearing lots of sunscreen so I can enjoy the beach without looking like a lobster when I go home. I’m sure we have all heard that we need to reapply sunscreen every 2 hours because it washes off but have you considered where it goes? What is in sunscreen that helps keep humans from turning into lobsters (and prevents skin cancer!)? Sunscreen contains UV (ultraviolet) filters that absorb the sun’s harmful UV rays that cause skin cancer.  Organic UV filters are a common ingredient in sunscreens and lotions to protect human skin but are also found in household products (textiles, plastics, paints, etc) to prevent discoloring and degradation.  Organic UV filters contain chemicals that absorb UV rays. One example is benzophenone-3, BP-3, measured in this study. Inorganic UV filters contain chemicals that reflect and scatter the UV rays so they can’t be absorbed (ex. zinc oxide). The organic UV filters end up in the water either by direct addition (when you jump into the ocean) or indirect addition through wastewater treatment plants (all the water that goes down the drain has to go somewhere!). There have been recent studies investigating the impacts these organic UV filters have on aquatic systems.

Negative impact on aquatic systems

Studies have shown that organic UV filters that end up in the water bioaccumulate and are found in organisms at multiple levels of the food chain from mussels to dolphins. Scientists have also found these filters are adversely affecting the development of coral larvae and causing coral bleaching. Recreational activities serve as a direct pathway of adding organic UV filters, and other anthropogenic pollutants, to coral reef communities. Recent work suggests that increasing recreational activities will exacerbate the negative effects of ocean acidification and increasing ocean temperature on coral communities. Preliminary work in Hong Kong detected organic UV filters near coral habitats. This study built upon that work with the ultimate goal to identify which organic UV filters were present and to assess the risk posed to the local coral ecosystem.

Study Site

The area is heavily urbanized and, with its impressive marine biodiversity, is a recreational hotspot for snorkeling. Nearby reefs are susceptible to pollutants via two pathways. Organic UV filters can be added by direct addition from recreational activities (e.g. tourists who remembered to wear sunscreen!) and indirect addition from wastewater treatment plants and river runoff.

Figure 1: Map showing the four study sites where coral, water, and sediment samples were collected


Scientists collected water, sediment, and coral samples during the wet (August 2015) and dry (April 2015) seasons from four locations in Hong Kong (Figure 1). They were careful to take small samples from corals and to only sample each colony once to minimize stress responses. All the samples were tested for seven common organic UV filters. They also took water and sediment samples to help determine where the organic UV filters go in the aquatic system and perform a preliminary environmental risk assessment.


Where did the organic UV filters go?

Scientists measured the seven most frequently used organic filters. There were no detectable organic UV filters found in the coral skeletons; however, five of the tested filters were found in the tissue in the wet season. I will focus on BP-3 (benzophenone-3) and BP-8 (benzophenone-8) as they represented 65% of the total organic UV filters measured during the study period in the coral tissue.  Only BP-3 and BP-8 were found in the coral tissue in the dry season. BP-3 was the dominant organic UV filter found in coral tissue as well as water and sediment samples (Figure 2).

Figure 2: A schematic of how organic UV filters end up in the ocean and the spatial distribution of BP-3 at the four sample sites for both sampling seasons

Previous work had also found substantial BP-3 in wastewater, surface water, and sediment in Hong Kong supporting its dominance in discharge in the area.  BP-3 is one of the most common organic UV filters used and most of the other chemicals tested are actually byproducts of metabolism (including BP-8). This explains why BP-3 was found in all sample types for both seasons. BP-8 is also used in personal care products for UV protection but in a much lower concentration.

Why is there more BP-3 in the wet season?

Compared to the dry season, the wet season is associated with increased recreational activity (e.g. snorkeling) which leads to a greater direct release of the organic UV filters to the water column. This study also suggests there could be a greater discharge from urban areas in the wet season via run-off and increased river flows increasing the indirect release of the organic UV filters. Wu Pai and Sharp Island had significantly higher BP-3 concentrations during the wet season compared to the other two sites. Sharp Island is considered a diving hotspot which could explain the higher concentration of BP-3. Therefore, the high BP-3 concentrations in the wet season are expected since it is released directly and not a chemical or metabolic byproduct.

Will the corals be safe?

A final goal of this study was to estimate the environmental risk for these coral species associated with the organic UV filters. They found that, at the current levels, there was only a low risk of coral bleaching. However, they caution that steps should be taken to protect the corals during the spawning season to minimize the impact these organic UV filters can have on the larvae.

What can we do?   

Figure 3: A coral community at the Beijing Aquarium (Source: Flickr, Matthew Stinson)

If you are a seasoned Oceanbites reader, you have an appreciation of the impact our choices have on the ocean. One step you can take to help protect coral reef communities is to use sunscreens that don’t use these organic UV filters. There are several companies that offer biodegradable alternatives. In the long run, we all need to be aware of the far reaching impacts our choices have. If we are not careful, the only way we will be able to see these beautiful coral reef communities in the future will be at aquariums (Figure 3). If you plan to spend your summer snorkeling or scuba diving to explore coral reef communities, be sure to limit the impact you have on their home. And remember that your sunscreen choices inland will wash down the drains and may reach coral reefs too!


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