Effect of Chelating Agents on the Accumulation of Cadmium by the Barnacle Semihlanus balanoides, and Complexation of Soluble Cd, Zn and Cu

Abstract

The effect of the presence of the chelating agents humate, alginate and EDTA on the accumulation of dissolved cadmium from seawater by the barnacle Semibalanus balanoides (L.) has been investigated. Humate and alginate significantly reduced the accumulation of cadmium after 7 d but any reduction in accumulation after 15 and 30 d was not significant. EDTA significantly reduced cadmium accumulation throughout 30 d exposure. It is concluded that the amount of cadmium accumulated by the barnacles is a function of the level of free Cd2+ ions available in solution. Soluble Cd, Zn and Cu in the barnacles are bound to high (> 30,000 MW) molecular weight proteins and to low molecular weight compounds eluting at or below the lower limit of linear separation of the gel Sephadex G-50 (- 1500 MW). There was no evidence for the binding of Cd, Zn and Cu to metallothionein-like proteins. The presence externally of dissolved cadmium complexed with low molecular weight metabolites extracted from barnacles, resulted in no change of cadmium accumulation by barnacles, indicating that the uptake of cadmium does not require the external binding of Cd ions with released metabol~tesb efore entry into the barnacle.