| Resumo: |
The phytoplankton of the Kars River was studied from May to October 2005 at five sampling stations. Sixty-six phytoplankton taxa were determined, consisting of Cyanophyta (9), Chlorophyta (25), Euglenophyta (18), Bacillariophyta (7), Cryptophyta (3), Dinophyta (1) and Chrysophyta (3). Total phytoplankton density increased from May to July and then decreased until October. The dominant phytoplankton group was Cyanophyta (36.5 - 64.4%) for most of the study period, followed by Bacillariophyta (20.4 - 38.7%) and Chlorophyta (20.9 - 28.9%). Temperature, pH and dissolved oxygen ranged from 9.6 °C to 21.6 °C; 7.6 to 8.0, and 5.9 to 7.4 mg/L, respectively. Chlorophyl a level changed from 0.0025 to 0.0059 mg/L. On the other hand, both phosphate and nitrogen levels tended to increase from May to July. The maximum and minimum densities of phytoplankton were 19781 (July) and 8851 (October) org/mL, respectively, and this variable correlated significantly with temperature. Soluble Reactive Phosphorus (SRP), Total Phosphate (TP), Dissolved Oxygen (DO) and abundance of Cyanophyta, Chlorophyta, Bacillariophyta and Cryptophyta.
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