Nano and microplastic interactions with freshwater biota – Current knowledge, challenges and future solutions

Current understanding of nano- and microplastic movement, propagation and potential effects on biota in freshwater environments is developing rapidly. Still, there are significant disconnects in the integration of knowledge derived from laboratory and field studies. This review synthesises the current understanding of nano- and microplastic impacts on freshwater biota from field studies and combines it with the more mechanistic insights derived from laboratory studies. Several discrepancies between the field and laboratory studies, impacting progress in process understanding, were identified including that the most prevalent plastic morphologies found in the field (fibres) are not those used in most of the laboratory studies (particles). Solutions to overcome these disparities are proposed to aid comparability of future studies. For example, environmental sampling and separation of biota into its constituents is encouraged when conducting field studies to map microplastic uptake preferences. In laboratory studies, recommendations include performing toxicity studies to systematically test possible factors affecting toxicity of nano- and microplastics, including morphology, chemical makeup (e.g., additives) and effects of plastic size. Consideration should be given to environmentally relevant exposure factors in laboratory studies, such as realistic exposure medium and effects of plastic ageing. Furthermore, based on this comprehensive review recommendations of principal toxicity endpoints for each of the main trophic levels (microbes, primary producers, primary consumers and secondary consumers) that should be reported to make toxicity studies more comparable in the future are given.