Ecological guild rather than taxonomy drives metal and metalloid bioaccumulation in Mediterranean elasmobranchs: a multi-species ICP-MS assessment

Elasmobranchs are effective bioindicators of chemical contamination, integrating habitat use, trophic ecology, and longevity. We quantified 16 metals and metalloids by ICP-MS in the muscle of 81 individuals from six Mediterranean elasmobranch species spanning a benthic-to-pelagic gradient (Raja radula, Mustelus mustelus, Mustelus punctulatus, Myliobatis aquila, Dasyatis pastinaca, and Alopias vulpinus). Arsenic and iron dominated elemental profiles in benthic and demersal species; R. radula showed the highest As, Sr, Mn, and Ni concentrations, consistent with sustained sediment contact, while A. vulpinus (n = 3) showed markedly lower As and an aluminium-dominated profile. Kruskal-Wallis tests revealed significant interspecific differences for nine elements, and Principal Component Analysis explained 41.7% of variance, revealing a clear benthic-to-pelagic gradient. Model comparisons indicated that ecological guild, rather than species identity, better explained accumulation patterns. Mean concentrations of Pb and Cd were below EU maximum levels in all species; Pb exceeded the limit in one M. mustelus individual. These results support Mediterranean elasmobranchs as guild-sensitive bioindicators and establish a baseline for ecotoxicological monitoring.