The influence of iron on copper toxicity to the marine diatom, Nitzschia closterium (ehrenberg) W. Smith

Abstract

The effect of iron on the toxicity of copper (0–60 μg Cu l −1) to the marine diatom, Nitzschia closterium (Ehrenberg) W. Smith was studied using unsupplemented sea water for growth rate experiments. Intracellular and extracellular iron and copper concentrations were determined by inductively coupled plasma emission spectrometry and anodic stripping voltammetry. Cells cultured under normal f medium iron levels (790 μg Fe·l −1) were more tolerant to copper than cells cultured in iron deficient medium (79 μg Fe·l −1 and 7.9 μg Fe·l −1). Lower extracellular iron and higher intracellular copper concentrations were found in cells grown previously in iron deficient medium compared to cells grown in normal iron medium. Iron, however, had no effect on the toxicity of the lipid soluble copper complex, copper-oxine. It is proposed that copper toxicity is reduced by colloidal ferric hydroxide, carried over in the assay inoculum, which binds to the diatom cell membrane, absorbs copper and prevents copper penetration into the cell.