Plastic pollution has emerged as a major environmental issue. However, knowledge about the occurrence and characteristics of plastic-associated biofilms, its dynamics and contribution to the fate and environmental effects of plastic pollution is still very poor. This urgent and timely research question will be addressed by an international consortium of recognized biofilm and fluvial ecologists from Germany, Sweden, Canada, Denmark, Switzerland, France, Argentina and Spain. The main aim of the action is to create an international excellence network for the investigation of the dynamics of plastic particles in fluvial systems. To reach this goal the consortium will: 1) Organize a meeting of all consortium members to discuss and agree on a protocol and a pilot sampling to examine the occurrence of plastic particles in fluvial biofilms covering a wide range of climatic and land use gradients in distant regions of the world; 2) Travel to the most distant places to contribute to the correct implementation of the protocol at the extremes of the selected gradient; 3) Host foreign researchers to refine the protocol; 4) Organize a workshop with a core group to work on a methodological paper reporting the results obtained; 5) Write the draft of project to investigate the dynamics of plastic particles in fluvial systems (third and final meeting).