Sub-lethal effects of several metallic salts—organic compounds combinations upon the heterotrophic microflora of a natural water

The effects of several sub-lethal combinations of the metallic salts Ag₂SO₄, CuCl₂, HgCl₂ and ZnCl₂ with the organic compounds -cysteine and albumin upon the heterotrophic activity of the microflora of a natural water are studied. This heterotrophic activity technique is based upon the uptake and mineralization of a radioactivity labelled metabolite by the indigenous microflora of the Simon Fraser University reflecting pool water. Data analysis by Michaelis—Menten enzyme kinetics equations allows the estimation of the maximum rate of heterotrophic activity as well as a determination of the turnover time of the nutrient in question. The addition of a sub-lethal combination of Cu²⁺ and Zn²⁺ to a sample of the pool water decreases heterotrophic activity to approximately the same extent as the additive decrease caused by these two cations added separately to samples of this water. Cu²⁺ and Zn²⁺ treated water samples do not recover the pre-metallic salt treatment activity following a 3-day incubation. Both -cysteine and albumin have no protective effect upon heterotrophic activity inhibition caused by Hg²⁺ and Ag⁺ respectively, at the concentrations used.