Nanoplastics rewire freshwater food webs

The accelerating use of plastics worldwide is of societal concern, especially as plastics fragment into smaller, micro- and nano-sized particles. Of particular importance is the effects on aquatic ecosystems since a major part of the nanoplastics eventually reach natural water systems. We identify, using replicated experimental wetlands, a tipping point where nanoplastics become detrimental to the key planktonic grazer, Daphnia. Moreover, the phytoplankton diatoms were also strongly affected by nanoplastics, whereas we detected no effects on the less efficient herbivore copepods, cyanobacteria, benthic bacterial decomposition, or any bottom dwelling organisms. That some organisms and ecosystem functions, but not others, are strongly affected by nanoplastic particles predicts considerable alterations in aquatic food webs and a rewiring of feeding links. In a broader context, our study provides crucial data on the effects of nanoplastics in semi-natural, complex ecosystems, constituting urgently needed understanding for risk assessment, legislation, and management of plastic material.

Methods
A long-term, large -scale freshwater mesocosm set-up was exposed to a gradient of nanoplastics. Organisms, inlcuding pelagic (zoo- and phytoplankton) and benthic organisms, as well as ecosystem functions were assessed.