Baseline trace metals in Patella caerulea in a central Tyrrhenian ecosystem (Pontine Islands archipelago and Lazio region coastal sites, Italy)

In this study, we tested the aptitude of the gastropod mollusk Patella caerulea as biomonitor of elemental pollution in seawater of a central Tyrrhenian ecosystem (Pontine Islands archipelago and Lazio region coastal sites, Italy). Concentrations of Cd, Cr, Cu, Ni, Pb, and Zn were measured in 120 individuals collected in six strategic locations in two sampling campaigns during 2011 and 2012. Samples of surrounding seawater were also collected in the same sites and tested for the same metals in order to obtain the respective concentration factors (CFs). Then, we analyzed the evolution of contamination in the selected sites and compared our results with the baseline levels (control charts) previously established for Tyrrhenian seas (Conti et al. Environ Sci Pollut R 22:3640–3651,2015). With this purpose, we defined six new variables (one for each metal) and then we applied multivariate statistics, i.e., cluster analysis and discriminant analysis on the principal component analysis factors in order to obtain more reliable results. Patella resulted to be a strong bioaccumulator of Cd (CFs = 8990) and a good accumulator of Cr, Pb, and Zn. The levels of the majority of metals (i.e., Cr, Cu, Ni, Pb, and Zn) in Patella decreased in the range from −13.06% of Zn to −42.51% of Ni in Fiumicino harbor, Anzio beach, and Ponza Harbor from 2011 to 2012. In general, the metal levels in these marine areas are low and within the previously established baseline ranges for Tyrrhenian Sea (control charts). Here, we found a not univocal trend of metal bioaccumulation patterns between the two sampling campaigns (2011–2012) in the selected sites. No one site resulted to be clearly more contaminated than another (i.e., harbor sites as expected). For instance, for Cd, we detected a relevant increase of its levels (+118%) in the harbors and Anzio beach sites from 2011 to 2012; however, they remained at lower levels of the lower limit (Q ₂.₅) of the control chart. Higher Pb levels with respect to the baseline values were observed for the majority of samples in the Ponza Cala Fonte site. Patella confirmed its usefulness as a cosmopolitan trace metal biomonitor in marine Mediterranean areas. The possibility of employing these results as a baseline level for comparative purposes in other marine areas is fully debated.