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Plankton research for environmental protection: pollution from sunscreen cosmetics

Atualizado: 24 de nov. de 2021

By Sabine Schultes

Illustration by Joana Ho

In my last post I introduced you to the concern of polluting the aquatic environment with cosmetics that protect us from UV-radiation. Since then, I’ve had help from many of our biology students at LMU Munich to collect data on specific research questions and to reach out and communicate the problem to the public. In this post, I dwell on the results that Helena, Theresa, Alexandra, Franziska, Mirjam, Daniela and Isabel obtained in their B.Sc. theses or post-graduate lab internships - yes, only smart young women were at work here!

Our research focused on plankton, which is the basis of aquatic food webs and we were able to work with timely lab methods to study pollution effects on growth, physiology and diversity. Plankton communities from lakes and coastal waters were sampled, individual species of phytoplankton and zooplankton were grown in culture and used in experiments. The students worked hard in the laboratory and spent weeks at the microscope - even the electron microscope! - they used cell counters and pigment analyzers to gather results.

A straightforward approach to find out about negative effects was to work with cultures of one species and pollute those with different concentrations of a sunscreen cosmetic. It allowed us to estimate changes in the rate of cell division, for single celled organisms such as phytoplankton, or to measure the success of development from larvae to adult when working with zooplankton. To cut a long story short, we found out that growth and recruitment in a copepod culture, i.e. tiny crustaceans, were delayed at sunscreen concentrations that were two orders of magnitude lower than the concentrations needed to reduce the growth rate of their food. I will get back to the consequences of this later.

Taking complexity one step further, the students incubated lake water, which contained a natural mixture of phytoplankton species, and again polluted the samples with different concentrations of sunscreen. This time, we were able to observe that one phytoplankton group, the diatoms, was particularly sensitive to the changes in water chemistry. Cyanobacteria, however, could take advantage and grew even under highly polluted conditions where species belonging to the other functional groups (chlorophytes and cryptophytes) were also disappearing. At these levels, copepods die within 24 hours. In this image from the scanning electron microscope, you can see how mineral particles contained in sunscreen cosmetics stick to a diatom cell.

A photograph taken from a microscope of several diatoms disposed on a blade.

Several diatoms disposed on a blade

(Copyright D.Maurer ,Bachelor thesis, LMU Munich)

Why is it a problem when chemical pollution interferes with plankton growth?

In the aquatic environment, both freshwater and marine, all species of the community are connected in a complex food-web where energy is transferred from producers (phytoplankton) via first order consumers (zooplankton) to top-consumers (fish, for example). Inorganic nutrients are constantly used and recycled and the ecosystem is considered to be in a dynamic equilibrium. When some of the components of the food-web are lost because of greater sensitivity to pollution, this equilibrium is shifted leading eventually to further loss of species and ultimately to a degradation of the water quality to levels where human health is also affected. Whether sunscreen pollution entails this kind of consequences will depend on the amount of cosmetics that enter the water with the swimmers.

Six petri dishes showing differences sunscreen  brands. Some of them dissolve completely and others don't.

As you can see in this figure, how easily a sunscreen dissolves in water varies strongly between brands. (Copyright M.Kathol, Bachelor thesis, LMU Munich)

Water circulation will dilute the locally enhanced pollution throughout the water column. Therefore, plankton in small lakes or systems with little exchange and stirring of water during the summer will be more at risk than along ocean beaches that have a high rate of flushing. Also, if cosmetic ingredients can be broken down by bacteria the ecosystem will recover quickly, but some components are refractory to microbial degradation and will accumulate along the food chain in top-consumers.

What can we do to find a solution to this problem?

Instead of polluting the plankton samples with commercial brands and hence chemical mixtures, we started to explore which of the individual components were “plankton safe” and which were not. For this, we used a DIY (do it yourself) recipe for natural cosmetics - that was the easy part - and experimented with an artificial plankton food web. It was extremely tedious work! In this picture you can compare the color of the bottles to the left with the ones on the right. One of the components that we tested shifted the balance between the green producers (algae) and their consumers – so we need to consider it NOT ”plankton safe”.

Six incubation bottles, the left ones have a brown layer in the bottom and the right ones have a green layer in the bottom.

Incubation bottles

(Copyright I.Schultz-Pernice, Master internship report, LMU Munich)

To communicate our scientific work to the general public, one of my students made an opinion poll at popular bathing spots around Munich. She got help from a social scientist working in the field of environmental communication – another bright young woman! - and together they developed a questionnaire. Swimmers were asked about their habits of buying and using sunscreen.

A vertical bar graph showing peoples selections to purchase sunscreen.  30 people selected price, 22 selected skincompatibility, 10 selected environmental compatibility and 14 selected ingredients.

(Copyright M. Kathol, Bachelor thesis, LMU Munich)

The majority of people were not yet aware of the water pollution due to sunscreen cosmetics and other personal care products. We informed them about our research and suggested to them strategies on how to reconcile their own “sun safety” with an environment-friendly behavior. Swimmers and sunbathers are open to find solutions such as buying environmentally safe cosmetics but products need to remain affordable, since the price is really important for consumer choice.

So, can you protect yourself AND the aquatic environment?

I guess this question needs to be answered individually. If you work outside and in contact with water, for example if you teach water sports, the choice should be to wear protective clothing. As a tourist who has the habit to sunbathe intensively during your short holidays, you should search for sunscreen cosmetics that are environmentally friendly even if they cost a little bit more. As a matter of fact these will also be good for your skin – and remember all the research effort that has probably been invested into its development! We are working on it...

six incubation bottles wrapped in a plastic bag inside ocean water.

Ongoing work: Incubation of water samples to test the plankton safety of a DIY sunscreen cosmetic under real light conditions (~ 2m water depth) at a Mediterranean beach.

(License CC4.0 BY)


About Sabine

Hi and thanks for coming to my profile. I am happy to contribute to this blog and to reach out to other Ocean lovers. My university education is in biology and oceanography. I spent 20 years away from home studying and working in other countries and on other continents. I had the chance to work as a scientist and university teacher. At present, I live at home again and I teach at a wonderful school in Munich. Water is a fascinating substance. No life is possible without liquid water. Water shapes our land and all the water in the Ocean helps maintain Earth’s temperature. Next time you are at the beach, take a bottle and fill it with (clean!) seawater. Smell it and shake it. Compare it to your mineral water and you will get a first glimpse that the Ocean is alive.

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