Preventing marine plastic pollution through citizen science while promoting public stewardship of aquatic environments.

Plastics waste is a global emerging threat for aquatic ecosystems, ubiquitous in rivers, lakes and marine areas, where about 8 million metric tons of plastic debris end up every year. It is estimated that 80% of marine debris has land based origins, transported to the sea by rivers and sewage. By comparison, the amount of plastics released into freshwater and terrestrial environments is likely to be much higher as these provide the main transport pathways to the marine environment. As an example, in the Mediterranean Sea, terrestrial debris represent 94%, of which 95% consists of macro and micro plastic litter. However, relatively little is known about the abundance and sources of this anthropogenic litter. This information is fundamental to determine its impact and to identify successful mitigation strategies prior to its arrival in our waters. Importantly, while the scientific community (including ourselves) is dedicating much effort on the impacts of plastic on marine and in general, aquatic ecosystems, the problem of plastic pollution needs to be tackled on land. We present here a citizen-science project aimed at promoting public stewardship of local aquatic resources, quantifying the type and quantity of plastic entering our rivers with the aim of reducing the amount of plastic reaching our seas. Efforts to solve the plastic problem require a partnered approach between research institutions, municipalities, educational institutions and citizens, achievable through citizen science. Focusing on the connectivity of all aquatic ecosystems in the emerging challenge of plastic debris in the hydrosphere, we present recent research activity and the efforts of the community of citizen scientists monitoring local water bodies for anthropogenic litter presence and composition