Potentially sublethal physiological effects of metal pollution exposure in a reef-associated shark, Carcharhinus...

Reef-associated sharks are increasingly exposed to marine pollution, yet sublethal physiological consequences of contaminant exposure remain poorly understood. Associations between metal and metalloid exposure and circulating physiological biomarkers were investigated in free-ranging Caribbean reef sharks (Carcharhinus perezi) from Eleuthera Island, The Bahamas. Using non-lethal blood sampling from 32 individuals, serum concentrations of essential, potentially toxic, and toxic elements were quantified and related to physiological stress markers. Seven significant metal-physiology associations were identified. Lactate concentrations were positively associated with rubidium and scandium, suggesting altered energetic demands. Triglycerides increased with mercury, while total cholesterol was positively associated with arsenic and thorium, consistent with elasmobranch-specific lipid metabolism. In contrast, β-hydroxybutyrate showed negative associations with lithium and scandium, indicating potential modulation of ketone-based energy pathways. Although causality cannot be inferred, these findings provide the first evidence of pollutant-associated physiological variations in wild C. perezi and highlight the importance of incorporating sublethal stressors into elasmobranch conservation assessments.