SEASONAL ANALYSIS OF VOLATILE ORGANIC BIOGENIC SUBSTANCES (VOBS) IN FRESHWATER PHYTOPLANKTON POPULATIONS DOMINATED BY DINOBRYON,MICROCYSTIS AND APHANIZOMENON1

Over the course of one year the volatile organic biogenic substances (VOBS) found in the water of a eutrophied shallow lake were determined by gas chromatographic and mass spectrometric methods. The substances detected belonged to nor-carotenoids, terpenoids, unsaturated hydrocarbons, ketones, and aldehydes. The occurrence of particular VOBS correlated with the frequency with which certain phytoplankton species were recorded. The latter showed a well developed succession in that year. The following correspondences were found: β-cyclocitral and Microcystis; heptadec-cis 5-ene and Oscillatoria redekei; geosmin and argosmin and Aphanizomenon gracile; hepta-trans, cis 2,4-dienal, deca-trans, cis 2,4-dienal and Dinobryon; octa-trans, cis 1,3,5-triene and Asterionella formosa. Dictyopterenes and ectocarpene were only detected in high amounts in one sample obtained in August. The VOBS exhibited marked dynamics in the lake and usually were rapidly eliminated from the water body.