Kinetics of Microbial Manganese Oxidation and Trace Metal Binding in Sediments: Results from an in Situ Dialysis Technique

Sediments associated with freshwater ferromanganese concretions in Lake Charlotte, Nova Scotia, contained microscopic precipitates of manganese and iron. These precipitates were dispersed throughout the sediment and were as rich in nickel, cobalt, and copper as deep sea concretions. In addition, the development of the precipitates appeared to be associated with the microbial oxidation of manganese. Results from the deployment of poisoned and unpoisoned dialysis probes or "peepers" demonstrated that microbial manganese oxidation and nickel binding were closely associated, causing a fivefold enhancement of abiotic processes such as adsorption. The microbial enhancement of copper binding was far less pronounced, due to orgnic-metal interactions in competition with manganese oxidation. Organic-metal interactions and oxidation may both have been in effect during iron binding, but the relative importance of the two processes could not be determined from the kinetic data.