MEPS 299:179-191 (2005)  -  doi:10.3354/meps299179

ABSTRACT: This study investigated whether the nature of the binding of the trace metals cadmium, silver and zinc accumulated by phytoplankton can affect their subsequent assimilation efficiencies (AE) in 3 filter-feeding benthic invertebrates, the green mussel Perna viridis, the clam Ruditapes philippinarum and the barnacle Balanus amphitrite. Seven phytoplankton species were chosen from a wide systematic range to ensure large differences in the partitioning of their accumulated trace metals into 3 fractions: (1) exchangeable metal adsorbed on the outside of the cells, as defined by extraction with the chelating agent 8-hydroxyquinoline-5-sulphonate; (2) incorporated metal that is in a soluble form; and (3) insoluble incorporated metal. There were few significant correlations between AE and the percentage of phytoplankton metal incorporated into any 1 fraction or combination of fractions. There is no support, therefore, for a generalised conclusion that any of the 3 fractions isolated represents the sole form of phytoplankton metal that is bioavailable for trophic transfer to a herbivore. Even trace metals bound to the insoluble fraction in phytoplankton may be bioavailable to herbivores. Furthermore, there were no consistent effects of phytoplankton concentration on metal AEs in 1 of the herbivores—P. viridis. There was no evidence that the AE of any of the 3 trace metals was changed when the herbivores were feeding on the phytoplankton species (Thalassiosira weissflogii) on which they were fed during acclimation.

KEY WORDS: Trace metal assimilation · Phytoplankton · Filter-feeding invertebrates