Evaluation of Agreement among Ecological Indices in Determining the Quality of Karaj River (Alborz Province)

In this study, the degree of agreement between five benthic indices in assessing the ecological status of the Karaj River was investigated. We sampled macrobenthic fauna using a sorber sampler in nine stations during 2017-2018, seasonally. In terms of abundance, the Shironomide family was dominant. Baetis, Tubifex, Micrasema, Rhithrogena, Eporus, Hydropsyche, Leptophlebiidae, and Simulium made up 83% of the samples. The values ​​of H', EPT, ASPT, BMWP, and HFBI were calculated (12.2±0.65), (5.6±2.8), (3.9±1), (48.8±23.34) and (4.6±1), respectively. The relative agreement in the results obtained from the five studied indicators was seen in 67% of the stations with unacceptable quality in the case that 22% of the river stations showed complete agreement and 11% of the stations showed disagreement. As a result, due to the occurrence of structural and population changes of macrobenthos in aquatic ecosystems due to natural factors and human activities, in order to use biological indices in each region for environmental management, there is a need to simultaneously use indices. It is important to check the agreement between different methods and choose the appropriate ecological index. Based on the results of the present study, the Helsinhof index (HFBI) can be introduced as a more suitable index than other studied indices to evaluate the ecological status of the Karaj River.