Trace metal exchange in solution by the fungicides Ziram and Maneb (dithiocarbamates) and subsequent uptake of lipophilic organic zinc, copper and lead complexes into phytoplankton cells

Abstract

Abstract The fungicides Ziram and Maneb (class dithiocarbamate) are organic Zn and Mn complexes in which the trace metal is chelated to organic dithiocarbamate ligands. The resulting organic metal complex is small, neutrally charged, and lipophilic in character. Short-term uptake experiments using a coastal diatom demonstrated that these lipophilic organic Zn and Mn complexes diffuse across the lipid bilayer that constitutes the plasma membrane. In addition, Cu2+ and Pb2+ ions in seawater solution undergo exchange reactions with Zn and Mn and form lipophilic organic Cu and Pb complexes that also diffuse across the plasma membrane and into the cytosol of the cell. Intracellularly, these trace metals are thought to dissociate from the transport ligand and complex intracellular ligands. Based on these results, the presence of dithiocarbamate fungicides in surface water can inadvertantly enhance the passive uptake of a variety of toxic heavy metals from the water into microorganisms.