SUMMARY: Gel-stabilized model sediment ecosystems were prepared using agar and colloidal silica as gelling agents and were employed in studies of the effects and degradation of xenobiotics in marine and freshwater sediments. All models produced physicochemical and microbiological profiles characteristic of sediments. The fate of 3-nitrophenol was studied in a freshwater system and the compound was found to be readily distributed through the gel column and to be rapidly degraded. The release of the nitro-group during metabolism resulted in the accumulation of nitrate in the aerobic portion of the gel column. The fate of a 1:1 hexadecane/naphthalene mixture was investigated using a seawater model system. The metabolism of these compounds resulted in oxygen depletion in the gel column and in a decrease in the population size of aerobic heterotrophic bacteria. Conversely, the populations of anaerobic heterotrophic bacteria and sulphate-reducing bacteria were significantly increased. The data are discussed with particular respect to the practical uses of gel-stabilized model ecosystems in research into the microbiology of sediments.


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