Microbial Potential for the Anaerobic Degradation of Simple Aromatic Compounds in Sediments of the Milwaukee Harbor, Green Bay and Lake Erie

Abstract

The ability of microbial populations to mediate the anaerobic transformation of six aromatic compounds in sedi ments from the Milwaukee Harbor, Green Bay, and Lake Erie was examined Sediment slurries were incubated in an anaerobic mineral salts medium that was amended with multiple electron acceptors, including manganese(1V) and Fe(II1) oxides, and the concentrations of the aromatic substrates were followed over a six to 18 month period Most sediment samples showed a com plete loss of benzoate and 4 hydroxybenzoate within approximately two months Benzoate losses were partially to markedly inhibited by the addition of molybdate, whereas losses of 4 hydroxybenzoate were not molybdate inhibited Significant losses of aniline, 3 chlorobenzoate, and 2,4-dichlorophenoxyacetic acid were observed with many of the sediments after approximately 18 months Molybdate markedly inhibited the metabolism of 3 chlorobenzoate with all sediments, and of aniline with some sed iments Increases in free chloride, which are indicative of reductive dechlorination were coincident with losses of 3 chlorobenzoate and 2,4 dichlorophenoxyacetic acid No significant metabolism of 4 chlorobenzoate was apparent in any of the sediments Over all, the results indicate that microbes with the ability to degrade at least certain aromatic compounds are present at various sites within these environments

Influence of protozoan grazing on contaminant biodegradation

“…Once the presence of protozoa was documented, laboratory experiments were conducted to evaluate the in£uence of protozoan grazing under both aerobic and anaerobic conditions. The objectives of the ¢rst experiment were: (1) to screen a number of protozoan inhibitors under aerobic conditions for iden-ti¢cation of a suitable inhibitor for use under anaerobic conditions; and (2) to evaluate whether protozoan grazing could be signi¢cant under aerobic conditions. Aerobic conditions were employed because the population of aerobic protozoa exceeded that of anaerobes in the sediment tested and results could be obtained more rapidly than under anaerobic conditions.…”

“…Groundwater aquifers have been contaminated with a wide variety of hazardous organic chemicals as a result of both primitive waste disposal practices and accidental releases [1,2]. Common contaminants include petroleum hydrocarbons, chlorinated solvents, ketones and ethers.…”