Methodological Assessment of Macro- and Mesoplastics Pollution in Rivers

Globally, plastic pollution in aquatic environments has been considered one of the major contemporary environmental challenges. Even though environmental effects associated with plastic pollution have been largely known, research on plastic concentrations mainly focuses on the marine environment. In recent years, an increasing number of studies reported environmental consequences and concentrations of plastic particles in freshwater systems comparable to those found in marine ecosystems. The observed abundance of plastic particles in ecosystems may be influenced not only by their actual presence in the aquatic environment but also by factors such as sampling methods and identification processes. Facing that, in this study, we assessed the variation in macro- and mesoplastics abundance and composition in the river Rhine collected using a larvae net, a trawl net, and a stow net. Additionally, we highlighted the strengths, weaknesses, opportunities, and threats through a SWOT analysis of the used methods for plastic monitoring. During trawl net and stow net monitoring, more unique macro- and mesoplastics categories were found in comparison with simultaneous larvae net monitoring. However, the main categories follow the same patterns among methods, and the relative abundance per category per method slightly differs. Overall, the SWOT analysis pointed towards a better performance of the trawl net for plastic monitoring in the river Rhine. The outcome of the current study can be used to support policymakers, industry, and the scientific community to devise a successful monitoring strategy for macro- and mesoplastics pollution in rivers that best aligns with the specific monitoring goals and the environmental conditions of the target area.