Multiple trace element accumulation in the mussel Septifer virgatus: Counteracting effects of salinity on uptake and elimination

Highlights: • Long-term bioaccumulation and elimination and short-term uptake of different metals were quantified in the mussels. • Salinity had relatively weak or no significant influence on trace element bioaccumulation in the black mussels. • Salinity effects on the uptake and elimination of Ni and Zn counteracted with each other. • Synchronized variations of uptake and efflux can explain the trace element accumulation at different salinities. • Elimination may play a more important role than uptake in determining the overall influences of salinity. Salinity effects on the bioaccumulation and biokinetic processes of eight trace elements (Cu, Cr, Pb, Ni, Zn, Cd, Se, and As) in the black mussel Septifer virgatus were explored in the present study. A 6-week laboratory waterborne exposure first showed that salinity (15, 20, 25, and 30) had relatively weak or even no significant influence on trace element accumulation in the black mussels. Biokinetics including uptake and efflux was then quantified in the mussels at different salinities. Uptake rates of Ni and Zn were negatively correlated with the salinity, while the uptake of Cd was not significantly influenced by salinity. The efflux rates of Ni and Zn also exhibited an inverse relationship with salinity, whereas the case of Cd was on the contrary. Biokinetic modeling showed that the salinity effects on uptake and elimination of Ni and Zn counteracted with each other, thus weakening the combined effects on accumulation. Overall, the response of uptake to salinity could weakened, removed, or even overturned by elimination, depending on the relative magnitude of the change of the two processes. The combined effects of uptake and elimination further led to negative, no, or positive relationship between trace element accumulation and salinity.