Citizen scientists help discover microplastics along the entire German coastline

Global plastics production could almost triple by 2060, according to estimates by the Organisation for Economic Co-operation and Development (OECD). This leads to more plastic waste and a build-up of plastic in water bodies, where it breaks down into microplastics -- particles smaller than or equal to five millimeters. "This irreversible plastic pollution is affecting species, populations and ecosystems, including along the German coast," says Dr Bruno Walther, formerly of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), now at Heinrich Heine University Düsseldorf and lead author of the recently published study. The extent to which our beaches in the North Sea and Baltic Sea are polluted has so far only been assessed for individual areas or locations, but not for the entire German coast. "This is why we launched the citizen research project 'Microplastic Detectives' to collect comparable data on the large-scale distribution of microplastic pollution along the German coastline."

With the help of citizen scientists, the research team was able to collect a total of 2.2 tons of sand from 71 locations along the German coast, covering a total area of 68.36 square meters. "We have combined a total of 1139 comparable samples into one large dataset. That's more geographic coverage than we've ever had before," says co-author and AWI biologist Dr Melanie Bergmann. The samples were then dried at the AWI, sieved and analyzed under a microscope for plastic particles as small as one millimeter in size. "In this study, we deliberately focused on large microplastics in order to rule out airborne contamination with small microplastic particles and to simplify sampling for the citizen scientists."

The results were surprising: "Although we found plastic on 52 out of 71 beaches, the amount of large microplastics in the North Sea and Baltic Seas was lower than in other studies," explains Bruno Walther. "If we had also analyzed smaller microplastic particles, we would certainly have found much higher concentrations," adds Melanie Bergmann. In previous AWI studies in the North Sea and the Arctic, microplastics smaller than one millimeter accounted for over 90 per cent of the microplastics found in sediments. "We also randomly selected sampling sites on the beach, rather than focusing on accumulation areas such as drift lines." This may also explain differences.

Of the 1139 samples analyzed, 177 contained a total of 260 plastic particles. This is an average of about four plastic particles per square meter. On a ten-hectare beach, that would be 400,000 plastic particles. However, the analysis also shows that microplastic pollution varies greatly from place to place.

How effective are policies, and where do policies need to be re-adjusted?

"Our study is the first to provide comparable data on the large-scale distribution of plastic pollution along the entire German coast using standardized methods," emphasizes Melanie Bergmann. This is necessary, for instance, to be able to map the status quo against the success of future policies to limit plastic pollution. For example, monitoring results suggest that legislative changes may have led to fewer plastic bags being found on the seafloor in north-west Europe over the past 25 years. "But we need stronger, science-based policies that set binding rules on how we avoid, reduce and recycle plastics." This would include measures to limit the production and use of plastics to essential applications, to ban hazardous ingredients, to increase degradability in nature and thereby enable the circular use of fewer resources.

"Microplastic Detectives" also shows that monitoring programs that involve citizens to collect comprehensive and timely data collection are successful. Interest in supporting science to tackle plastic pollution is huge: "We were surprised by the number of citizen scientists who enthusiastically spent several hours on the beach, diligently collecting, packing and sending samples. We would like to express our heartfelt thanks for this," says Bruno Walther. "The ideal outcome of our project would be, to use it as a blueprint for long-term and even more intensive monitoring of microplastics pollution on German beaches," adds Melanie Bergmann. "This is the only way we can review and adapt the measures we urgently need to turn the tide on plastics and their negative impacts on our coastal environment, tourism and human health." The "Microplastic Detectives" project has now come to an end. However, citizens can still get involved in campaigns such as the Plastic Pirates citizen science project, which has school children collecting data on plastic pollution on coasts and rivers.