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Depth profiles of geosmin, of which a dissolved and particle-bound fraction was distinguished, were analyzed monthly in a seasonal study in a stratified mesotrophic prealpine lake (Lake Zurich). Remarkable seasonal and spatial differences in the total amounts and ratios between both fractions were observed. Equally low concentrations of dissolved and particle-bound geosmin were found in the winter season during turnover conditions (maximum total geosmin 3.1 ng l −1 ). In the clear-water period the dissolved fraction of geosmin increased dramatically (93% of the total) whereas the particle-bound geosmin showed only minor changes. In the autumn and first part of the winter surface films contributed essentially to the particle-bound fraction of geosmin exhibiting maximum concentrations of 21 ng l −1 . Possible producers of geosmin in Lake Zurich ( Aphanizomenon , Oscillatoria , Planktothrix ) were cultivated and their content of geosmin was determined. Feeding experiments with Daphnia and Simocephalus simulating the phenomenon of the clear-water period clearly demonstrated that grazing can be regarded as a major mechanism for the liberation of geosmin from particles. The mean degradation rate in a microcosm experiment caused by pelagic bacteria was 3.1 ng l −1 d −1 ; this rate was high enough to explain the concentration differences between consecutive sampling dates.

The Vitek Auto Microbic System (AMS) automated identification device was used in rapid identification of staphylococci and coliforms originating from food factory environments. From a total of 3324 isolates, an average of 76% were identified with a confidence > 50% (staphylococci: 61%, coliforms: 82%). AMS identifications of presumed staphylococci did not match well (24%) with ATB 32 STAPH identifications, but coliforms matched for 80% of the isolates compared with the API 20 E system. The differences observed between the AMS and ATB 32 STAPH in identifications could be due to inadequate isolation media, insufficient isolate purification, incorrect pre-screening of isolates or an incompetent AMS database. For coliforms, the overall performance proved sufficient for rapid screening of isolates from food factory bacterial ecology studies.