Investigation of Zayandeh River water quality based on Macrobenthos as biological indicators

To evaluate of water quality of the Zayandeh River using some macrobenthos as biological indicators, five sampling stations were selected upstream of the river. Sampling operations were done monthly for one year in all stations with three replications using a Surber sampler. Identification and counting of invertebrates were done using standard methods under a binocular microscope. To evaluate the water quality, four biological indicators, including Shannon-Wiener, Hilsenhoff, BMWP, and ASPT indexes were applied. Data analysis and calculation of studied indicators were done using Species Diversity and Richness version 4 (SDR4) software. Based on the results, the Zayandeh River water quality was evaluated in the range close to pollution. The Shannon- Wiener index categorized the Zayandeh River in the range of moderate pollution, the Hilsenhoff index assessed most of the stations with severe organic pollution, and the BMWP index classified the stations in the biologically acceptable range. In conclusion, the water quality of the Zayandeh River is classified as biologically acceptable but not stable.