Interview: „A somewhat bold interpretation“
Melanie Bergmann is a polar and deep-sea researcher at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). Since 2012, Ms. Bergmann has been working intensively on the pollution of the oceans with plastics, has published extensively on this topic, among others, the book "Marine Anthropogenic Litter". Furthermore, she is a member of several expert groups - including the German delegation for negotiating the UN Plastics Treaty - and coordinates the international MICRO symposia on microplastics. At AWI, she is involved in the development of new methods for measuring plastic litter and microplastics in the seas, and also works on studies about the effects of plastic residues on organisms. Against this professional background, we asked Ms. Bergmann for her assessment of the results of the study by the Thünen Institute for Fisheries Ecology (see the report "Microplastics not harmful to fish").
Ms. Bergmann, in our newsletter we report on the results of the Thünen Institute's study, which in a way gives the all-clear: According to the study - to put it briefly - microplastics do not seem to affect the health of fish and, as a result, would not pose a health risk to humans who consume the fish. Were you surprised by the results?
I have no doubts about the results themselves regarding the impact of microplastics on sticklebacks; it has been assessed by experts and published in a good specialist journal. However, the interpretation that the laboratory results of this one study could be transferred to other fish species or vertebrates as a whole, including humans, is surprising for me and for many of my colleagues.
According to the results of a study conducted by the AWI on behalf of the environmental organisation WWF, you found effects on 90 percent of the marine animals studied, which you described as "worrying". Can you give us more details about these effects?
In our overview study1), we summarized the knowledge available from hundreds of such individual studies up until 2019. This showed that at least 2,144 marine species are confronted with plastic pollution in their natural environment. The vast majority of these interactions involve consumption, entanglement, or being cut off from the supply of oxygen, light, or food. Whether interactions with plastic cause any harm was studied for 297 species, 88 percent of which showed adverse effects. 112 of these were fish species. One example would be rock bass, which ate less, swam less, and were restricted in their movement. The fish grew less and had lower energy reserves. In a study from Argentina, all the examined fish species had consumed microplastics and had less energy reserves in their livers. And in another study, glass perch, for example, were found to have lower growth rates due to microplastics. Microplastics from car tyres were found in another study2) to be highly toxic to North American salmon, and explained the increased dying of salmon frequently observed there after heavy downpours.
In an AWI study)3), microplastics were even found in the fillet of sea bass. In this way, it can thus be consumed by humans. Recently, microplastics have also been detected in human lungs4), blood5), placenta6), meconium7) and breast milk8) with unknown consequences for human development. Inflammatory reactions in certain blood cells9) have been proven as well as a connection with inflammatory bowel diseases10). There are thus certainly many indications of negative consequences for humans – not to mention the impact of the more than 10,000 plastic chemicals.
How would you classify the results obtained by the Thünen Institute in the context of research on the effects of microplastics on marine life, and where do you see the most urgent need for research on this topic?
In the study, only one fish species was examined - namely the stickleback – and also only one of very many plastic types and forms was studied - namely microfibres. Apart from that, the tests were only carried out over a limited period of time. To apply this to all fish in the North and Baltic Seas, or even to all vertebrates, is a somewhat bold interpretation in the context of the many other studies mentioned.
We still know far too little about how microplastics affect animals on the seabed. This is a huge gap in our knowledge, considering that the deep sea covers 60 percent of the Earth's surface, and many studies conclude that plastic accumulates there in particular. In the Arctic, we have found over 13,000 microplastic particles per kilogram of sediment11). It is very unsatisfactory that we can say nothing about the consequences. Nevertheless, the state of research is already sufficient to say that plastic is now found everywhere, and that we must curb the production of new plastics in order not to make the problem worse. After all, the plastic that is already in the environment breaks down over time into microplastics, which - with all their chemicals - we can no longer not remove.