Study on Bentic organisms of Ghazal Ozan River in Zanjan Province

Ghazal Ozen is one of the two main Caspian Sea catchments entering to the Sefidrood Dam. Sampling was done within 45 days from October 2009 till October 2011 on 3 stations. Benthic samples were fixed with %4 fomaline and were identified to the genus or species levels and investigated using to the Hilsenhoff biogogical index. In this study, 20 genera 7 orders were identified chironomidae as dominant family. Hilsenhoff Biological Index (HBI) for the 9 studied stations, were respectively, 5.4, 6.3, 5.46, 5.11, 5.13, 4.13, 4.25, 4, 4.23.The biological status of rivers based on HBI data was in the range of very good level. In the study, Chironomidae (30%), caenis sp. (16%), Baetis sp.(12%), Hydropsyche sp. (13%), Simmulium sp. (11%), Tabantus atratus and Sericostoma sp. (2%) and remaining benthos (14%) in Ghazan Ozan River. The results showed that the presence of organic matter pollutant has reduced oxygen levels and also affected the biota in Ghazal Ozan River.