Trophic influence on selenium, cadmium, and manganese accumulation in fish from tropical estuary (Sepetiba Bay, Brazil).

Estuarine regions are highly valuable ecosystems due to their high biological productivity and their role in providing food and habitats for numerous species. However, in the densely populated Southeast region of Brazil, these ecosystems face significant human-induced degradation and pollution. This study examined hepatic concentrations of selenium (Se), manganese (Mn), and cadmium (Cd) in five fish species from Sepetiba Bay (SB), Rio de Janeiro, Brazil, and explored their relationship with trophic position (δN). Our findings showed that Se concentrations increased significantly with trophic level when Trichiurus lepturus was excluded from the analysis (r = 0.45, p = 0.0002), suggesting a potential for Se biomagnification in species sharing similar feeding zones. In contrast, Mn exhibited no correlation with trophic position, and the hypothesis that lower trophic level species would show higher Mn levels was not supported. Cd accumulation appeared to be species-specific, possibly linked to benthic invertebrate consumption and historical contamination in the bay. Additionally, T. lepturus showed a strong positive correlation between Se and Cd concentrations (Spearman r = 0.86, p = 0.0107), suggesting potential detoxification mechanisms, as well as evidence of biodilution, indicated by the negative correlation between Cd and body mass (Pearson r = -0.83, p = 0.0116). These results highlight the influence of trophic ecology on trace element dynamics in estuarine food webs. Given the ecological and economic importance of these fish, our findings contribute to environmental risk assessments and reinforce the need for continued monitoring in anthropogenically impacted tropical estuaries.