Hepatic fatty acid fingerprints as biomarkers of persistent pollutant exposure in the ubiquitous blue shark (Prionace glauca)

Sharks exhibit remarkable species diversity, with most functioning as apex predators, making them particularly vulnerable to bioaccumulation of persistent pollutants (PPs). The ubiquitous blue shark ( Prionace glauca ) in particular, shows a strong capacity to accumulate contaminants that persist in marine ecosystems. Considering the biological relevance of fatty acids (FAs) and their potential interaction with pollutants, this study aimed to characterize hepatic FAs in 43 juvenile specimens and correlate them with two major PP classes to better understand their interactions and effects. An integrative Pollution Load Index (PLI), adapted from the literature and used here as a relative index of cumulative contamination, revealed that individuals were potentially in a concerning contamination state. Significant correlations were observed between PPs and specific FAs: positive associations with monounsaturated fatty acids such as oleic, erucic, and trans-FAs, and negative correlations with highly unsaturated fatty acids, mainly omega-3. These patterns reflect previously reported hepatic injuries and suggest a potential link between PP exposure and altered lipid metabolism or stress-related membrane remodeling, essential for the species' health and longevity. However, direct causal mechanisms cannot be inferred from the present data. Notably, trans-FAs, often overlooked in ecological studies and known for adverse health impacts, were strongly linked to increasing pollutant levels, especially persistent organic pollutants (POPs). The study further highlights that distinct fatty acid profiles and the membrane Double Bond Index can serve as reliable indicators of contamination stress and injuries. Overall, these findings provide valuable insight into how PPs affect essential lipid molecules in P. glauca , enhancing understanding of pollutant impacts on both coastal and deep-water marine organisms. • Cosmopolitan blue shark bioaccumulate harmful Persistent Pollutants (PPs). • Liver fatty acids from 43 juvenile sharks were correlated with metals and POPs using an integrative pollution load index. • Strong correlations found between specific PPs, and -trans and omega-3 FA classes. • Results highly suggestive of disruptive effects in normal lipid metabolism with potential long-term consequences. • FAs can be reliable markers of specific marine pollution and helpful to predict adverse effects at higher biological levels.