The Fluctuations of Physicochemical Factors and Phytoplankton Populations of Urmia Lake, Iran

Urmia lake is one of the two large hypersaline lakes in the world which have artemia. it is located in northwest of iran. due to a decrease in water inflow and volume, the salinity of urmia lake has reached to more than 300 g.r^-1 since 2001. the increased salinity has reatly influenced biological aspects of the lake, and caused the lake undergoes at critical conduction. the aim of the present study was to investigate the distribution fluctuations of phytoplanktons and selected physicochemical factors in relation to artemia distribution in urmia lake during 8 months. statistical analysis of mean values of ion concentrations and phytoplankton abundance indicated significant differences among sampling months. the minimum and maximum values for the selected factors were, as ci- 176.2-201.3 g.1^-1 co2 -1^ -1 -1 2+ 95-175mg.1 ,dissolved oxygen (do) 0.1-2.8 mg.l ,rc03- 144-496 mg.l ,p04 104-875 -1 - -1 - -1 2 -1 2+ mg.l ,n03 330-4104 mg.i ,n02 4-21.5 mg.l ,s04 - 10490-2984·0 mg.l ,ca 561-1606 -1 2+ -1 -1 mg.i ,mg 3649-14587 mg.i while water hardness was 21000- 62000 mg.l . ourteen phytoplankton genera included bacillariophyceae (10 genera), chlorophyceae (2 genera) and cyanophyceae (2 genera) were identified during sampling period. the smallest average density of phytoplankton 97249 l-1 was observed in december 2005 and the greatest average density 481983 l-1 in august 2005. dunaliella sp. composed 92.1 % of the ake's phytoplankton. statistical analysis of phytoplanktons fluctuations showed a significant difference among different months (p< 0.05).