Baseline Trace Metals Concentration in Monodonta turbinata Throughout Pontine Islands Archipelago, Italy

With the aim to assess the gastropod mollusk Monodonta turbinata as biomonitor of trace metal pollution in seawater of a central Tyrrhenian ecosystem (Pontine Islands archipelago, Italy), one hundred individuals were collected in five strategic locations in two sampling campaigns during 2011 and 2012. Concentrations of Cd, Cr, Cu, Ni, Pb and Zn were measured in the mollusks and in seawater samples (soluble fraction) collected in the same sites in order to obtain the respective concentration factors (CFs). Two-way ANOVA was applied to verify the presence of site and time effects. Then, the significant time effect due to the two sampling campaigns was eliminated by defining six new variables (one for each metal) and applied multivariate statistics in order to obtain more reliable results. Subsequently, the levels of metal contamination of Pontine Islands were compared with the naturality concentration ranges (control charts) previously established for the Tyrrhenian Sea (Italy; Conti et al. in Environ Sci Pollut Res 22:3640–3651, 2015). Monodonta resulted to be a very good accumulator of Cd (CF = 2100) and good accumulator of Cr (CF = 1570), Pb (CF = 1000) and Zn (CF = 1160). Levels of Cd, Ni, Pb and Zn in Monodonta from 2011 to 2012 decreased in the range from −22.8 of Pb to −41.9% of Cd in Ponza Frontone, Ponza Cala Fonte and Ponza harbor sites; on the contrary, Cr and Cu showed an increase of 3.4 and 63.7%, respectively, in the same sites from 2011 to 2012. A not univocal trend of metal bioaccumulation patterns between the two sampling campaigns (2011–2012) in the selected sites was observed. No one site resulted to be evidently more contaminated than another (i.e., Ponza harbor site as expected). In general, the metal levels in these marine areas are low and within the previously established baseline ranges for Tyrrhenian Sea (control charts). The results here reported can be used as a reference baseline levels for comparison with other marine geographical areas.