Salinity influences on the response of Mytilus galloprovincialis to the rare-earth element lanthanum

The multiplicity and wide variety of applications of electrical and electronic equipment has largely increased with the technological and economic progress and, in consequence, the amount of generated waste of electrical and electronic equipment (WEEE). Due to inappropriate processing and disposal of WEEE, different chemical elements and compounds, including rare-earth elements such as Lanthanum (La) have been released in the environment. Nevertheless, the environmental risks resulting from La presence are almost unknown, especially in marine systems, which may be challenged by foreseen climate changes such as water salinity shifts. Within this context, the present study aimed to understand the combined effects of salinity and La by assessing biochemical alterations in mussels Mytilus galloprovincialis exposed to La (0 and 10 μg/L) at different salinity levels (20, 30 and 40). A decrease in salinity caused a wide range of biochemical changes to both non-contaminated and contaminated organisms, such as metabolism, antioxidant and biotransformation defenses activation, associated to hypotonic stress. Furthermore, the decrease in salinity enhanced the effects of La exposure seen as an increase on lipid and protein cellular damage in those exposed, probably due to free metal ions increase at lower salinities, resulting in a higher bioaccumulation and toxicity. In general, La exposure caused cellular damage and inhibition of antioxidant defenses in contaminated mussels when compared to non-contaminated ones, with cellular damages being higher at the lowest salinity. Overall, the present study highlights the need to investigate the presence and impacts of emerging contaminants of WEEE source at environmental relevant concentrations, not just at present but also under forecasted climate change scenarios, thus providing a more realistic environmental risk assessment.