ASSIMILATION OF TRACE-ELEMENTS BY THE MUSSEL MYTILUS-EDULIS - EFFECTSOF DIATOM CHEMICAL-COMPOSITION

Mussels have been widely used as bioindicators of coastal contaminatio n, and recent reports have demonstrated that metals are accumulated fr om both the dissolved phase and from ingested food. In the winter and spring of 1995, we examined the influence of the chemical composition of food (protein content, trace element concentrations and ratios in t he diatom Thalassiosira a pseudonana) on the assimilation of six trace elements (Ag, Am, Cd, Co, Se and Zn) in the mussel Mytilus edulis (L. ). Differences of up to 38% in diatom protein content had no major inf luence on the assimilation of any trace element or carbon. Protein ass imilation in M. edulis examined with a S-35 radio-tracer was also inde pendent of protein content in the diatoms. Similarly, Se assimilation in mussels was not affected by the different Se concentrations in the diatoms. Cd assimilation increased with increasing Cd concentration, p resumably due to higher desorption of Cd under acidic conditions typic al of the mussel gut. Zn assimilation was inversely related to Zn conc entration in the food particles, implying a partial regulation of this metal in the mussels. There was no evidence of any interaction of Cd and Zn in their assimilation by the mussels. These results suggest tha t mussels are highly responsive, in an element-specific way, to some c omponents of ingested food (e.g., metal concentration), but other food components (such as the biochemical composition of the algae) have li ttle effect on assimilation.