Effects of heavy metals on microbial activity of water and sediment communities

The effects of Cd2+, Cr3+ and Zn2+ on the microbial activity of water and s ediment samples from a contaminated stream were studied. The maximum [C-14] glucose uptake (V-max) and the mineralization ((CO2)-C-14) rates were deter mined. A 10% reduction in V-max was obtained at lower metal concentrations in water samples than in sediment ones. Moreover, a 10% decrease in (CO2)-C -14 was observed at significantly minor metal levels, so (CO2)-C-14 was mor e sensitive to evaluated heavy metal pollution. On the basis of MICs obtain ed for both communities, they were more sensitive to Cd2+ than to Cr3+ and Zn2+. Zinc was less inhibitory to V-max and (CO2)-C-14 rates; Cr3+ showed a n intermediate toxicity, and Cd2+ was 10-100 times more inhibitory than the other metals.