Physicochemical parameters and their relation to phytoplankton community and chlorophyll a concentration in Karoun 4 reservoir (Chahar Mahal and Bakhtiari province)

The present study was carried out in Karun 4 Dam lake, Chaharmahal-v-Bakhtiari province with the aim of tropic determination and assessing some of the relationships between physical, chemical and biological properties of water from March, 2011 to 2012. Three stations were selected in the dam: one station near the dam wall and two stations at the entrance of Urmand and Bazoft rivers, respectively. Some of physicochemical properties of water including temperature, turbidity, hardness, temperature, pH, dissolved oxygen, biological oxygen demand, chemical oxygen demand, total soluble solids, total suspended solids, nitrates and phosphoric acid, as well as biological properties such as phytoplankton identification and counting, chlorophyll a were monthly evaluated. Based on the present results, 5 branches and 30 species of phytoplankton were identified with the most frequency of Bacillariophyta (17 species), Chlorophyta (6 species), Chrysophyta (4 species), Dinophyta (2 species), and Cyanophyta (1 species), respectively. The maximum and minimum chlorophyll a content were obtained in June (4.9 μg L-1) and its minimum in February (2.1 μg L-1), respectively. Findings of the current research showed that chlorophyll a concentration correlates with the temperature, while no correlation was found with the suspended solids (P> 0.01). On the other hand, chlorophyll a content and phytoplankton diversity showed a significant negative correlation with transparency, total nitrogen, and total phosphorus (P <0.01). The highest and lowest richness index was observed in summer (0.061117) and in autumn (0.058), respectively. The Simpson species diversity index was also reached to the highest and lowest value in spring (0.98889) and autumn (0.9905), respectively.