In summary, our study demonstrated that both the green mussel and the Manila clam
were able to assimilate metal from resuspended sediment particles. Metal concentration
in the sediment did not appreciably affect the assimilation of sediment-bound metals,
although Cd assimilation increased with increasing Cd concentration in sediment
presumably due to the increased desorption under an acidic condition. Metal assimilation
from ingested diatom was higher than assimilation from ingested natural sediment. The
presence of other particles did not significantly affect metal assimilation from a
particular type of food particles. Cd assimilation from diatom was however reduced with
the presence of sediment. Furthermore, metals were more bioavailable from oxic
sediment than from the anoxic sediment. Understanding metal bioavailability from sediment with different geochemical properties is important in assessing metal toxicity
from contaminated sediment. Our study highlights the importance of sediment as a
potentially important source of metal accumulation in the two bivalves common in
subtropical and tropical waters.