Evaluation of the Aras dam reservoir water quality by phytoplankton indexes Ali Mohsenpour Azari*, Feridoon Mohebbi, Abasali Motaalebi, Reza Ahmadi, Alireza Asem, Saber Shiri, Syavash Ganji Iranian Artemia Reference Center, Urmia, Iran  Summary: The Aras river is one of the largest rivers in northwest of Iran and an important one in Caspian Sea watershed. Aras watershed area is 102000 km2; the reservoir average width and length are 3 km and 52 km respectively; its maximum depth is 27.5 m. Sampling was conducted seasonally from three stations (A1- upstream; A2- intermediate; A3- downstream) along reservoir from June 2007 to March 2008. Phytoplankton population changes were investigated in order to calculate phytoplankton indices in each site. In the present study, 46 algal species were determined. These were belonged to five classes: Diatoms (Bascillariophytae); green algae (Chlorophytae); blue-green algae (Cyanophytae); Pyrrophytae and Euglenophytae. The water quality in sampling sites was studied based on the more utilized ecological indices such as Index of Dominance, Richness, Shannon-Wiener species Diversity index and evenness index. The lowest values of Species diversity index was observed in the summer. Evenness index showed the lowest values during summer and higher values in the spring.   Home