p -Nitrophenyl Acetate Esterase Activity and Cortisol as Biomarkers of Metal Pollution in Blood of Olive Ridley Turtles ( Lepidochelys olivacea )

This study was designed to determine the concentrations of p - nitrophenyl acetate esterase activity (EA) and cortisol in serum of marine Olive Ridley turtles ( Lepidochelys olivacea ) from a Mexican Pacific population (“La Escobilla” beach) and to evaluate the possible relationship of inorganic elements with these biomarkers. EA, cortisol, and selected chemical elements (Cd, Pb, Ti, Sr, Se, Al, As, and Zn) were measured in the blood of 44 sea turtles from the Eastern Pacific (Southeast Mexico). Serum EA ranged from 0.4 to 3.9 UI mL −1 , and cortisol concentrations ranged from 0.07 to 2.5 μL dL −1 . A strong negative correlation between EA and cortisol was observed ( r = − 0.59, p < 0.01), and significant correlations also were found between EA and important metals, such as Cd ( r = − 0.31, p < 0.05) and Pb ( r = − 0.27, p < 0.05), and elements of growing concern like Ti ( r = − 0.37, p < 0.01) or Al ( r = − 0.34, p < 0.05) and between cortisol and Sr ( r = 0.29, p < 0.05), Se ( r = − 0.38, p < 0.01), and As ( r = − 0.26, p < 0.05). These results suggest that turtles chronically exposed to different inorganic elements (such as Pb and Cd), driving to a highly consume of esterase and to a prolonged cortisol elevation. The obtained results indicate the usefulness of these biomarkers in the assessment of inorganic elements pollution in this species.