Harnessing citizen science to tackle urban-sourced ocean plastic pollution: Experiences and lessons learned from implementing city-wide surveys of plastic litter.

Plastic litter is an endemic problem within all regions, particularly cities. Much of this litter reaches the world's oceans with well documented environmental impacts. However, the monitoring of urban litter is often piecemeal at best. Citizen science, the action of utilising the public to support research, has been used to excellent effect for both research and engagement, usually for area clean-ups such as beach cleans. However, to date very few studies have assessed plastic pollution at a city scale. This study presents a novel citizen science approach, using a smartphone application to collect geolocated photographs of plastic litter during 5 city-wide surveys. The study has compiled a significant dataset of photographs (n = 3760), classified by plastic type to assess patterns of plastic pollution Portsmouth, UK. The method is shown to have significant potential for further development to facilitate detailed analysis of plastic litter in urban centres across the world.