Experiments were conducted to determine the relationship between the response of a bacterial isolate to copper, as measured by cellular incorporation of 14C-glucose, and the complexation of copper by organic ligands. Inhibition of glucose incorporation was dependent on the cupric ion activity and independent of the concentration of organic complexes of copper both in UV-treated seawater (36‰) containing different concentrations of a model chelator, nitrilotriacetate (NTA), and in low salinity media (1.8‰) containing varied amounts of commercially-prepared or river-borne humic compounds....