Mytilus edulis as a quantitative indicator of dissolved cadmium. Final study and synthesis

Abstract

Juvenile blue mussels Mytilus edulis were cultivated in flow-through aquaria to investi-gate the influence of dissolved cadmium on cadmium accumulation (in terms of the Cd/shell-wt index). Where the ratio (by weight) of dissolved Zn to Cd remains within the range 25:l to 60:1, accumulation of Cd is not significantly influenced by dissolved Zn. Higher levels of concomitant Zn reduce the Cd/shell-wt index. A lower ratio of Zn to Cd may slightly increase Cd accumulation. The Cd/shell-wt index is proportional to ambient levels of dissolved Cd up to 100 yg 1-' There were no significant effects on growth up to ca 30 pg 1-' Cd. Results corresponded to earlier experimental work and to field surveillance data reported in the literature. A procedure is suggested by which the concentration of dissolved Cd In natural environments may be estimated from 'mussel watch' data (Cd body burden, shell weight) and salinity. Cd accumulation in the mussel is described by the integral of the Cd/shell-rut index with growth of shells by weight. A model of biochemical accumulation of metals requires laboratory and field transplant experiments to be designed such that considerable growth is allowed in a new environment in order to approximate a new balance of metal residues in organisms in relation to ambient levels.