Multi-tissue elemental profiling of Atlantic bluefin tuna across temporal scales reveals shifts in environmental exposure

One of the most consumed fish in the Mediterranean Sea is the Atlantic bluefin tuna (Thunnus thynnus), which has long supported coastal communities through traditional fishing activities (tuna traps) and remains a key resource for modern commercial fisheries. In this context, biomineralized tissues such as vertebrae provide information on elemental incorporation over the lifetime of individuals and offer insights into past environmental conditions and pollutant exposure. This study aims to evaluate differences in major (Ca, K, Mg, Na), trace (Al, Fe, Mn, Cu, Zn, Co, Cr, Ni, Se, Sn), and toxic elements (Hg, As, Cd, Pb) across biological tissues (gills, muscle, vertebrae, liver) from 24 Atlantic bluefin tuna individuals belonging to three temporal groups (6 ancient, 6 historical, 12 contemporary) for a total of 37 samples. Elemental concentrations were determined by ICP-OES (Agilent 5800) and TDA-AAS (DMA-1, Milestone) following microwave-assisted mineralization (MARS-5, CEM). Statistical differences among groups were assessed using the Kruskal–Wallis test followed by Dunn’s post hoc test with Bonferroni correction for multiple comparisons, while principal component analysis (PCA) was applied to explore latent clustering patterns. The results of the PCA show a clear separation among temporal groups, with vertebrae providing the strongest discrimination; in particular, ancient samples generally exhibit higher concentrations of both trace and toxic elements compared to historical and contemporary ones. A second PCA focused on tissue variability indicates the liver as the matrix with the highest overall elemental accumulation, consistent with its central role in metal metabolism and detoxification processes [1]. The observed patterns may reflect a combination of environmental and biological factors. Higher elemental concentrations in ancient samples could be partially explained by natural geochemical baselines and inputs prior to industrial era, as well as shifts in trophic structure and feeding ecology over time altering biomagnification pathways in marine food webs [2]. These findings provide new insights into long-term trends in marine pollution and environmental variability, integrating geochemical proxies into the study of marine ecosystems across temporal scales, highlighting the value of combining biomineralized and soft tissues to reconstruct historical baselines. References [1] MM. Storelli, et. al., 2005, Marine Pollution Bulletin, doi:10.1016/j.marpolbul.2005.06.041. [2] RA. Lavoie, et. al., 2013, Environmental Science & Technology, dx.doi.org/10.1021/es403103t.