Chemical elements in Perna perna mussels as a tool to support the economic value of traditional fishing communities

The concentrations of chemical elements (Al, As, Ca, Cd, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Ti, and Zn) in the shell and soft tissue of the mussel Perna perna (L. 1758) are used to determine the individuals’ geographic origin. Additionally, a mineralogical analysis of shell is presented to confirm its primary crystalline structure. Mussels were sampled in Rio de Janeiro State, southeastern Brazil, from five geographically close sites. The COVID-19 pandemic served as a temporal reference for sampling, as it was a short-term conservation event that significantly influenced element concentrations in the mussels. Mineralogical analysis confirmed that aragonite is the sole polymorph of CaCO₃ present in the P. perna shell. Discriminant analysis demonstrated that element concentrations effectively distinguished the mussels’ geographic origin. For shells that developed before the pandemic, classification accuracy reached 97%, with Li, Mn, and Mg being the main discriminating elements. In contrast, for shells formed during the pandemic, accuracy was 89%, with Mn and Mg playing the most significant roles. For mussel soft tissue, discriminant analysis achieved 100% accuracy in classifying samples from both periods. The key elements contributing to model success were Na and K (pre-pandemic) and Fe and Mn (pandemic). These results indicate that the elemental composition of both the shell and soft tissue of P. perna can be successfully used to differentiate populations of the species, enhancing its traceability and supporting the economic value of traditional fishing communities.