Effects of dithiocarbamate and 8-hydroxyquinoline additions on algal uptake of ambient copper and nickel in South San Francisco Bay water

The addition of synthetic organic ligands such as diethyldithiocarbamate (DDC) and 8-hydroxyquinoline (Ox) to the dissolved fraction (<0.2 mu m) of South San Francisco Bay water facilitated the transport of ambient Cu and Ni into phytoplankton cells. The uptake mechanism is diffusion of the lipophilic organic Cu(DCC)(2)(0) and Cu(Ox)(2)(0) complexes (and corresponding Ni complexes) across the plasma membrane. Short-term uptake experiments were carried out using a coastal diatom, Thalassiosira weissflogii, and resulted in rapid uptake rates and high cellular concentrations of the metal relative to the bay water control. Steady-state conditions between the solution and cellular Cu concentrations occurred within 10 min for a 4 mu M addition of DDC and after 3 h for a 100 mu M addition of Ox. Steady-state cellular Cu concentrations were over 10 times and 6 times greater, for DDC and Ox treatments, than in the bay water controls. Steady-state cellular Ni concentrations were attained within 10 min far both ligand additions and were more than 6 times and 2 times greater than in the absence of the added Ligands. Using this bioassay, we were also able to gain insight into the character of the background organic Cu complexes in South Bay. Our results suggest that the natural organic Cu complexes are relatively hydrophilic in character and do not appear to he directly assimilated across the plasmalemma.