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.l-1 since 2001. The increased salinity has greatly 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 Cl- 176.2-201.3 g.l-1 , CO2 95-175mg.l-1 , dissolved oxygen (DO) 0.1-2.8 mg.l-1 , HCO3 - 144-496 mg.l-1 , PO42+ 104-875 mg.l-1, NO3- 330-4104 mg.l-1, NO2- 4-21.5 mg.l-1, SO42- 10490-29840 mg.l-1, Ca2+ 561-1606 mg.l-1, Mg2+ 3649-14587 mg.l-1 while water hardness was 21000- 62000 mg.l-1. Fourteen 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 lake's phytoplankton. Statistical analysis of phytoplanktons fluctuations showed a significant difference among different months (p< 0.05)

Relationship between Artemia population dynamics and chlorophyll a fluctuations in Urmia Lake (Iran)

Determination of chlorophyll a is one of the most common methods for measuring the primary production in the lakes and sea water. We studied Artemia Leach. dynamics and chlorophyll a fluctuation and their relationship in Urmia Lake. Sampling was performed monthly during one year (2007) at eleven sampling stations in Urmia Lake. Population dynamics analysis of Artemia from Urmia Lake suggested that the highest diversity in various Artemia morphological stages was present from May to July and the highest densities in March. On the other hand, no morphological stages were observed, at all stations in the lake, from January to April. The mean chlorophyll a concentration in Urmia Lake was 0.8 µg.L-1, and the highest and the lowest concentrations of chlorophyll a were measured in June and July with 2.53 µg.L-1 and 0.1 µg.L-1 respectively. According to the Carlson classification Urmia Lake was oligothrophic. Artemia biomass appeared in the mid spring and bloomed in the summer. Generally, there was a negative relationship between Artemia population and chlorophyll a