Distribuição de metais-traço (Cu, Cd, Pb e Zn) em quatro espécies de tartarugas marinhas da costa do Nordeste do Brasil

Abstract

Sea turtles are long-lived organisms widely distributed in coastal environments and are recognized as important models for studies of environmental contamination, especially by persistent pollutants such as metals. In this context, the present study aimed to evaluate trace metal concentrations in four species of sea turtles, as well as to identify the main biological, ecological, and environmental factors influencing the levels of these metals in these species. To achieve this, considering that these animals are threatened with extinction, priority was given to the use of non-invasive methods, such as the use of carapace fragments, and, whenever possible, tissues from dead individuals were also used. Concentrations of copper (Cu), cadmium (Cd), lead (Pb), and zinc (Zn) were quantified in four species of sea turtles found along the northeastern Brazilian coast: Chelonia mydas, Eretmochelys imbricata, Caretta caretta, and Lepidochelys olivacea. Bioaccumulation patterns were associated with feeding habits in two of the four species, investigated through stable isotope analysis of carbon (¹³C) and nitrogen (¹⁵N), in addition to the evaluation of morphological data and estimation of life stage. No significant differences in metal concentrations were observed among sampling areas for each species, when comparisons were possible, suggesting the absence of spatial variation in the evaluated regions. Therefore, samples from northeastern Brazil were consolidated as a single analytical unit for each species. Cu concentrations differed among species, with C. caretta showing the highest values and L. olivacea the lowest. Cd was predominantly below the detection limit and showed no interspecific differences. For Pb, C. mydas presented the highest concentrations, differing significantly from E. imbricata. Zn was the most abundant metal in the carapace and showed the greatest segregation among species, with higher values in C. caretta and L. olivacea. Significant interspecific differences were confirmed for Cu, Pb, and Zn. In the tissue analysis of C. mydas, Zn showed the highest concentrations, with no significant differences among tissues, suggesting homeostatic regulation of this element in the organism. Cu showed higher concentrations in the liver, with significant differences compared to the other tissues, reflecting its physiological role and participation in metabolic processes. Cd showed higher concentrations in the liver and kidney, associated with the formation of complexes with metallothioneins in these organs, which are involved in detoxification processes. Pb showed relatively similar concentrations among tissues, with a significant difference only between the carapace and muscle. Overall, the results indicate that variations in trace metal concentrations in sea turtles from northeastern Brazil reflect bioaccumulation patterns modulated by physiological and ecological characteristics of the species. These findings contribute to expanding knowledge about metal dynamics in these organisms and reinforce the importance of monitoring these species to better understand environmental contamination in marine ecosystems.