The effect of point source pollution (fish pond effluent) on macro-invertebrates communities and validation of three biotic indexes (EPT, BMWP, HFBI) in assessing the water quality of Baliglu river in Ardabil province

Biotic indexes are an effective tool for measuring the water quality of rivers and lakes. In this study, the effect of fish pond effluent on water quality and validation of three common biotic indexes EPT, BMWP, and HFBI in Baliqlu river of Ardabil province was investigated. A sampling of invertebrates communities was done seasonally from the summer of 2018 for one year with the help of a Sorber sampling device with dimensions of (40 * 40 cm) and in three replications.10582 samples from 10 orders and 14 families were identified. The highest frequency was related to the order of Ephemeroptera and then Diptera, which belonged to the Baetidae and then Chironomidae family, respectively. Shannon-Wiener (H)(1.20) diversity, uniformity (exp(H)/S)(0.83), Simpson (1-D)(0.66), and dominance (D)(0.33) indices were used to study the diversity of macro-invertebrate communities. The results of determining the correlation of environmental parameters with the distribution of macrobenthos and environmental factors with each other by Detrended Correspondence Analysis (DCA) in PAST software (version 3.25) showed that the environmental parameters of nitrate and phosphate were positively correlated with Chironomidae and Tipulidae families. Based on the Helsinhoff(HFBI) biotic index, the water quality of the Baliqlu River in the third station with severe pollution (HFBI = 8.24), based on the EPT, water quality in the third station is poor (EPT = 9.5) and the BMWP biotic index reflects poor results. The water quality of Baliqlu River in all stations was in a poor quality class. The validation results of the three indicators used, showing that the BMWP, unlike other indicators, has a relatively poorer performance in the Baliqlu River and in the quality assessments of our country's rivers, it is better to use a combination of several biological indicators.