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Plastic waste from the fishing industry, particularly lobster trap identification tags from the USA and Canada, poses a significant threat to marine ecosystems due to its resilience. This study unveils a novel link between North American fisheries and the appearance of these plastic tags in Macaronesia. Collected in the Azores and Canary Islands, these tags offer a unique insight into the sources and spatio-temporal scales of marine plastic pollution. Ocean model data indicates the Labrador Current and Gulf Stream as key forces transporting these tags. Virtual particle simulations show a small fraction reaching Macaronesia (4.12 % in the Azores, 0.76 % in the Canary Islands), suggesting real ocean drift. The Azores, with more collected tags, are more susceptible, and tags can reach Macaronesia in under a year. These findings underscore the urgency of better waste management and emphasize the role of citizen science in monitoring and combating marine pollution. • Plastic lobster tags disperse extensively, reportedly reaching Macaronesia. • The Labrador Current and Gulf Stream play a pivotal role in plastic tag dispersal. • Lagrangian tracking confirms Azores' greater vulnerability to plastic tag arrivals. • Simulated estimates agree on observed particle arrival at Macaronesia in <1 year. • Plastic tags serve as 'bottled messages,' showcasing pollution monitoring potential. [ABSTRACT FROM AUTHOR]

[Display omitted] • Temporal trend detected in the number of plastics but not in the mass. • A threshold value to monitor floating plastics using Cory's shearwaters is proposed. • Its implementation as a bioindicator is relevant for OSPAR and the MSFD. • Seabird victims of light pollution are robust indicators of plastic contamination. • The use of similar shearwaters as bioindicators would enable worldwide assessments. The potential of using organisms as bioindicators of marine litter has been an area of general interest in multiple scientific and monitoring programs across the globe. Procellariiformes seabirds are particularly vulnerable to plastic contamination, which makes them a research focus group. This study investigated plastic ingestion in deceased fledglings and adults Cory's shearwaters (Calonectris borealis) collected over eight years (2015 to 2022) at two Atlantic archipelagos: the Azores and the Canaries. Necropsies were carried out in a total of 1,238 individuals showing a high prevalence of plastic ingestion (90%), with approximately 80% of items recovered from the gizzard. Fledglings carried greater plastic loads compared to adults, yet plastic morphologies were similar between both age classes. The temporal analyses conducted with generalised additive mixed-effect models revealed a distinct temporal trend in plastic numbers, but not in terms of plastic mass. In addition, the spatial analyses showed that Cory's shearwaters from the Canary Islands ingest a higher quantity of plastic and a greater proportion of threadlike items than the Azorean birds. These results suggest higher contamination at the NW Africa foraging grounds next to the Canaries and highlight fisheries as a potential source of marine litter in that region. On the other hand, the information gathered from the Azorean birds suggests they would be able to monitor changes in the composition of the plastic items floating in the North Atlantic Subtropical Gyre. Overall, our outcomes support the use of Cory's shearwater fledglings that are victims of light pollution as a key bioindicator of plastic contamination in the North Atlantic. For its policy application, the presented threshold value in combination with the assessment method will enable effective tracking of floating plastic litter in the framework of the MSFD and OSPAR. [ABSTRACT FROM AUTHOR]