Copper toxicity in freshwater sediment and Aeromonas hydrophila cell suspensions measured using an O2 electrode

The effect of CuSO4 on O2 consumption in sediment samples and a pure culture of Aeromonas hydrophila were examined using an O2 electrode. Maximum inhibition of O2 consumption in sediment samples was 85% at Cu concentrations ranging from 400 to 500 μg/g sediment. In contrast, O2 consumption by A. hydrophila cell suspensions was inhibited 100% at Cu concentrations of 150 μg/mL in stream water and 250 μg/mL in sediment extract, respectively. Nonbiological (chemical) O2 consumption also occurred in sediment samples during the bioassay. This was demonstrated by respiration insensitive to KCN (metabolic inhibitor) and the observation that chemical O2 consumption occurred in autoclaved sediment samples. Caution should be taken when interpreting O2 consumption data in environmental samples as nonbiological reactions may interfere with the bioassay.