Ecotoxicological links between trace elements, fatty acids, and oxidative stress in Atlantic and Mediterranean shearwaters.

Trace elements can disrupt oxidative balance in vertebrates by inducing the production of reactive oxygen species, leading to oxidative damage to key biomolecules, including DNA, lipids, and proteins. This study investigated (i) the concentrations of 15 essential and non-essential trace elements (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Sr, Ti, Zn) in the blood of Calonectris shearwaters breeding in three colony sites in the Northeast Atlantic Ocean and the western Mediterranean Sea, (ii) their associations with oxidative damage biomarkers (DNA damage and lipid peroxidation), and (iii) their influence on fatty acid signatures. While most trace elements exhibited consistent levels across shearwaters from the different colonies, the non-essential As, Hg, Ni, and Ti, and the essential Co showed spatial variations, suggesting site-specific contamination sources. Trace element concentrations were associated with variations in fatty acid signatures. More specifically, higher concentrations of As, Hg, and Ni were negatively correlated with highly unsaturated ω-3 fatty acids, suggesting potential physiological stress in Mediterranean shearwaters. Conversely, increased saturated and monounsaturated fatty acids suggested adaptive mechanisms to counteract oxidative damage caused by trace elements. Specific odd-chain fatty acid markers of heterotrophic bacterial activity were also in accordance with proximity to environments with higher anthropogenic pressure. These findings highlight the need for further research on trace element exposure in seabirds and the effects of environmental stressors on fatty acid profiles, particularly regarding their ecological and physiological consequences concerning the health of marine ecosystems.