Identify and evaluate the diversity of Macrobenthos in Karaj River

Study on diversity and distribution of macrobenthos on Karaj River, was conducted during year 1393-1394. In the study area, selected five study sites and faunistic macrobenthos the seasonally by quadrat and 5 time repeat, samples were taken at each station. Samples collected by 4% formalin and isolated, identified and were counted. In this study, 6 orders, 22 families and 24 genus were identified from macrobenthos and the winter and spring seasons in sequence had the most and the fewest abundance of macrobenthos, on Karaj River. Between five selected stations on Karaj River, the station 4 in winter season had the most abundance (1067) and the station 5 in spring season had the fewest abundance (254) of samples. Insecta had the most abundance (88.7 % of total) and Malacostraca had the fewest abundance (1% of total) between five classes were identified on Karaj River. Among the cases identified, 879 species per square meter Simulim sp. with the highest abundance and species Asellus aquaticus, Atherix sp. With frequency of 1 per square meter the lowest among the species had been identified. On average during the year Shannon-Wiener diversity index was 1.73, Simpson dominance species was 0.74 and Margalef richness species was 3.31. According to the biological values HFBI, stations, spread over 3 classes very good quality (Station 1), excellent (stations 2 and 3), very good (4 stations) and good (Station 5) was reported.