By Sabine Schultes
Edited by Katyanne M. Shoemaker
Most people who like the sea and the shore also enjoy a sunny day at the beach, playing in the water when the weather is warm. Luckily, the education campaigns for skin cancer protection have made us all aware of the importance of protecting ourselves from harmful ultraviolet (UV) radiation which is a part of natural sunlight. UV light is at the lower end of the light spectrum and is divided into UVA, UVB and UVC. The highly energetic UVC is absorbed by our atmosphere, but UVA and UVB reach the surface.
So, we all adopted the habit to regularly apply cosmetic sunscreens before sunbathing, but we are typically not as attentive when it is time to take a dip in the lake or ocean. Probably, you are just like me and are so anxious to cool off, that you rush over the hot sand and to take a wonderfully refreshing dive head first into the waves.
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UV radiation is not only a problem for us, but for all living beings, especially if they are without protective pigmentation, feathers, fur, or scales. Single-celled organisms have it even harder, so much so that one way to kill bacteria to make a sterile environment is to expose the lab bench to a couple of minutes of UV radiation. Sunburn for a single cell is lethal!
Plankton are, in most cases, single celled or transparent, so they are very sensitive to UV light. Luckily, ocean and lake water progressively absorbs the incident sunlight. Depending on how clear the water is, UV light only reaches a few meters below the surface. Planktonic organisms have nevertheless evolved repair mechanisms to cope with the constantly occurring DNA damage.
Alternatively, plankton can avoid UV radiation by migrating to water depths with no or little UV radiation. This strategy has been adopted by the zooplankton such as some copepods . Other copepods that live in very clear alpine lakes or in the surface layer of the tropical ocean are pigmented, often orange or even blue! Instead of getting a suntan - when our skin cells produce melanin - the zooplankton simply accumulates the pigments from their algal food. One example are the beautiful blue copepods from the genus Anomalocera, in the family of the Pontellidae.
Now, what happens if you and I take our dive into the waves and the sunscreen we have applied to our skin is washed off, into the sea? Yes, large parts are washed off, even if you use waterproof lotion. Looking through the scientific literature makes it clear: sunscreen cosmetics are a source of pollution with growing concern. Waters of popular beaches all show high concentrations of the organic molecules used as chemical UV filters in sun protection creams. Very low concentrations (10µg/L) are sufficient to promote coral bleaching. The chemicals persist in the aquatic environment and accumulate in mussels, fish and dolphins. Lakes and rivers are also subject to this type of contamination.
This is why I have decided to do at least two things:
Before taking a swim I will try to get rid of most of the cream on my skin. Many modern beach facilities have showers connected to a wastewater system. So why not have a quick wash before you dive? If showering is not an option, I bring baby wipes and rub off the excess.
I started to do my own research into the question. I am interested in learning how plankton growth and diversity is affected by sublethal concentrations of sunscreen. Is the pelagic food web disturbed? Are there alternative cosmetics available with potentially less harmful effects for the aquatic environment?
Sunscreen cosmetics are complex mixtures of organic UV-filters (e.g. oxybenzone, octocrylene, …), oils, perfumes, stabilizers and often nanoparticles. Our experiments also try to find out, which of the components are particularly harmful, and if sunscreen cosmetics that are solely based on natural oils may be a better option for the aquatic environment. I will tell more about this in my next post - so wait and see!
Preliminary results show that plankton growth can either be enhanced or reduced when the water is polluted with conventional sunscreen, depending on the concentration we add and whether the water comes from an oligotrophic or eutrophic environment. The community composition of the phytoplankton is modified because some algal groups are more sensitive to sunscreen pollution than others. The use of sunscreen may even be one of the causes of cyanobacterial blooms in recreational lakes leading to skin irritation in summer swimmers.
We need recreation, and we need to protect ourselves from UV radiation to prevent skin cancer. How can we fulfill the needs of human society without totally spoiling our environment? This question is exemplary for many issues in nature conservation! So, I am passing this question on to others and will make an opinion poll at the beach...
Beach life in Ubatuba, Brazil Beach life in Munich, Germany
Further reading:
Balmer, M., Buser, H.R., Müller, M.D., Poigner, T. 2005. Occurrence of some organic UV
filters in wastewater, in surface waters, and in fish from Swiss lakes. Environ. Sci. Technol. 39: 953-962
Cunha, C., Fernandes, J.O., Vallecillos., L., Cano-Sancho, G., Domingo, J.L., et al. 2015. Co-occurrence of musk fragrances and UV-filters in seafood and macroalgae collected in European hotspots. Environ. Res.143: 65–71
Danovaro, R., Bongiorni, L., Corinaldesi, C., Giovannelli, D., Damiani, E., et al. 2008. Sunscreens cause coral bleaching by promoting viral infections. Environ. Health Perspect. 116:441–447
Gago-Ferrero, P., Alonso, M. B., Bertozzi, C. P., Marigo, J., Barbosa, L., et al. 2013. First determination of UV filters in marine mammals. Octocrylene levels in Franciscana Dolphins. Environ. Sci. Technol. 47: 5619−5625
Sánchez Rodríguez, A., Rodrigo Sanz, M., Betancort Rodríguez, J.R. 2015. Occurrence of eight UV filters in beaches of Gran Canaria (Canary Islands). An approach to environmental risk assessment. Chemosphere 131: 85–90
Tovar-Sánchez, A., Sánchez-Quiles, D., Basterretxea, G., Benedé, J.L., Chisvert, A., et al. 2013 Sunscreen products as emerging pollutants to coastal waters. PLoS ONE 8(6): e65451.
About Sabine:
With the goal to become a marine biologist, I studied biology and hydrobiology at Hamburg University and then earned a Master’s degree in oceanography from Université du Québec à Rimouski, in Canada. My doctoral studies in biological oceanography at the Alfred Wegener Institute in Bremerhaven were followed by various post-doc projects in Brest, France and Sao Paulo, Brazil. Since 2012, I teach ecology and zoology at LMU Munich. Growing up, my parents gave me the incentive to search new ways and to relate with people and cultures around the world. I am convinced that today, more than ever, we need to take good care of our Oceans.