engleski

The structure and dynamics of microphytoplankton assemblages in the saline lake Vlaška (eastern Adriatic coast)

Analyses of microphytoplankton from the highly stratified Lake Vlaška were carried out in the period from April 1999-April 2000. A total of 145 microphytoplankton taxa was identified. Diatoms, dinoflagellates and cyanophytes were the most important microphytoplankton constituents of the lake. The Bacillariophyceae gave the highest number of taxa (74), followed by Dinophyta (58), Prymnesiophyceae (8), Chrysophyceae (3), Euglenophyceae (1), Cyanophyceae (1) and Chlorophyceae (1). The seasonal development of microphytoplankton cell numbers exhibited two peaks (in April and in August 1999). The first peak reflected the intensive development of Cyclotella sp. and Chaetoceros curvisetus. The second peak was mostly made up of the species Nitzschia longissima and Chaetoceros vixvisibilis. Four different microphytoplankton assemblages, occurring throughout the year with some overlapping, have been distinguished in the microphytoplankton community of the lake. The first assemblage was noted between April-June, the second July-September, the third October- December, and the fourth January-March. The main feature of these assemblages is the simultaneous dominance of more than one species. The reason for this can be found in the very frequent and rapid changes of environmental conditions in this dynamic ecosystem. Diatoms (50-99%) dominated the microphytoplankton cell numbers throughout the year, while dinoflagellates caused outbursts of growth in September 1999. Cyanophyte (Oscillatoria sp.) appeared from January to March 2000.

microphytoplankton; saline lake; eastern Adriatic

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