Microbially mediated manganese oxidation in a freshwater lake1

Geochemical and microbiological studies support the hypothesis that bacteria mediate manganese oxidation in aerobic bottom waters of Oneida Lake, N.Y. In lake water samples maintained in the laboratory, decreases in soluble Mn2+ and the formation of oxidized manganese (MnO2) occurred only in summer samples which supported metabolically active Mn‐oxidizing bacteria. The eff’ect of initial Mn2+ concentrations on Mn oxidation and on the disappearance of soluble Mn2+ (binding) was studied in water enriched from natural levels (1.2 ± 0.4 µM in June and 0.48 µM in August 1979) to 9.1–200 µM Mn2+. Highly enriched lake water (⩾65 µM Mn2+) inhibited Mn oxidation. Binding and oxidation of Mn was inhibited in filtered samples when particles >0.4 µm were removed, and inhibition persisted when the particles were first ethanol treated and then reintroduced into filtered lake water. Within the range of 0–20 µM Mn2+ rates of Mn2+ binding varied with the initial Mn2+ concentrations in August water samples.