Document Type : Review paper
According to the long term hydrobiological survey on the Aras reservoir based on phytoplankton, zooplankton and zoobenthose indices, the organic contamination of water was evaluated. Regarding its biological indicators, the saprobic quality of Aras reservoir was determined as (1.6-2.0 or β-mesosaprob). The higher saprobic indices (3-3.5 or α-mesosaprob) were observed on its deeper areas. In spring increased of water flow may mitigate the saprobic condition and change the related indicators to a lower level in the reservoir.