Gastrointestinal content analysis in juvenile green turtles (Chelonia mydas) as an indicator of coastal pollution in Rio de Janeiro, Brazil

Abstract

ABSTRACT This study aimed to analyze the gastrointestinal contents of 315 juvenile Chelonia mydas rescued along the coast of Rio de Janeiro State between 2020 and 2023, in order to characterize the ingestion of anthropogenic debris and assess its spatial patterns, while exploring potential temporal variation as an indicator of coastal pollution. Records derived from necropsies conducted under the Santos Basin Beach Monitoring Project were accessed through the Aquatic Biota Information and Monitoring System. The analysis was based on the presence or absence of solid debris and oily residues, and occurrence frequencies were evaluated across monitoring sections and seasonal categories. The natural diet was predominantly composed of algae (88.3%), followed by invertebrates and fish. Solid anthropogenic debris was detected in 45.1% of individuals, while oily residues were found in 1.3%. The chi-square test revealed a significant association between solid-debris occurrence and monitoring section (χ² = 16.61; df = 4; p = 0.002), indicating spatial heterogeneity. Seasonal patterns were described using absolute and relative frequencies and should be interpreted with caution because the numbers of recorded strandings differed among seasons. The findings indicate that the ingestion of anthropogenic debris is widespread among juvenile C. mydas along the coast of Rio de Janeiro and may represent a potential threat to the species. Spatial differences in debris occurrence suggest heterogeneity in contamination patterns. These results support the use of this species as a bioindicator of environmental contamination and underscore the importance of integrated coastal management and pollution control measures.