Marine debris ingestion by cetaceans stranded on the coast of Southern Brazil

The Southwestern Atlantic Ocean (SWAO) is a global biodiversity hotspot where the impact of plastic pollution on cetaceans remains poorly understood. This study evaluated debris ingestion in cetaceans stranded along the southern Brazilian coast from 2015 to 2020. Of the 884 individuals with analyzed gastrointestinal contents, representing 22 species, debris was found in 10.1% of cases, with coastal species being the most vulnerable. The endangered Franciscana dolphin ( Pontoporia blainvillei ) showed the highest ingestion rate (17.9%). Pathological analysis of a subsample ( n = 20) revealed that gross lesions in the digestive tract were rare and showed no apparent association with debris in these cases. In a subset of individuals with known causes of death, the most common findings were consistent with asphyxia caused by fishery interactions. This suggests that the high incidence of plastic ingestion warrants further investigation into chronic, sublethal impacts, such as toxic effects, that coexist alongside immediate threats, such as interactions with fisheries. Our findings provide an important baseline and underscore the need to assess plastic pollution within the context of multiple, simultaneous stressors to effectively protect vulnerable marine wildlife. • Out of 884 cetaceans with analyzed gastrointestinal tracts, 10.1% ingested debris. • Endangered P. blainvillei shows high vulnerability with a 17.9% ingestion rate. • Plastic ingestion is a sublethal threat; digestive lesions were not significant. • Plastic's toxicological risk must be studied alongside acute threats like bycatch.