The Effect of Metal Concentration in Bottom Sediments on the Accumulation of Metals by the Mytilids Crenomytilus grayanus and Modiolus kurilensis

The relationship between the concentration of Pb, Cu, Cd, Zn, and Ag in soft tissues of mytilids Crenomytilus grayanus and Modiolus kurilensis and in bottom deposits was studied to determine the potential and limitations in the use of these molluscs as bioindicators of contamination of coastal waters near Vladivostok (northwest of the Sea of Japan). It was found that the mussel C. grayanus began to accumulate Pb and Cu after certain threshold concentrations of these metals (60 and 150 g/g respectively) in fine fractions of sediments was reached. Accumulation of Pb and Cu by M. kurilensis also depended on the level of sediment contamination, but the higher initial metal content in tissues and the higher individual variability reduced the sensitivity of this species as a bioindicator. Accumulation of Cd and especially of Zn in mytilid tissues is adjusted by the organism, which restricts the opportunity of their use for tracking the anthropogenic input of bioavailable forms of these metals.