The Relationship Between Embryotoxicity and Oxidative Stress Produced by Aluminum, Iron, Mercury, and Their Mixture on Cyprinus carpio

Aluminum, mercury, and iron have been found in high concentrations in various freshwater bodies around the world and have been shown to be very harmful contaminants to hydrobionts, causing metabolic dysfunction and damage at various levels. However, studies on mixtures of these pollutants are scarce, particularly in younger or developing organisms, which are more sensitive to damage. Therefore, the objective of this work was to evaluate the toxicity of Al, Fe, and Hg, in isolation and in mixture, on common carp embryos exposed to the maximum permissible limits described in the Mexican regulations for the protection of aquatic life, correlating the biomarkers of oxidative stress with the effects on embryonic development. For this purpose, the Cyprinus carpio embryos were exposed to iron (0.1 mg L⁻¹), mercury (0.00001 mg L⁻¹), aluminum (0.05 mg L⁻¹), and their mixture, throughout their development and until hatching. The activity of the antioxidant enzymes (SOD, CAT, and GPx), the degree of lipoperoxidation, and the content of hydroperoxides and total proteins, as well as the morphological development of the embryos were evaluated at 12 h, 24 h, 48 h, 72 h, and 96 h of exposure. The results showed that the metals under study are toxic to C. carpio embryos and that their interaction modifies the toxic response. Thus, iron generates alterations in the activity of antioxidant enzymes and modification in embryonic development to a lesser extent than aluminum and the mixture of metals, while mercury exerts its toxicity on embryos by mechanisms other than oxidative stress, but the modification to the activity of antioxidant enzymes may contribute to the changes observed in embryonic development. The changes in the response of biomarkers of embryotoxicity and oxidative stress suggest that the combination of metals produces an antagonism-type interaction, so this study provides a precedent for future research to determine the type of interaction that a mixture of contaminants generates in developing aquatic organisms.