Biological assessment of Baliqlu River by investigating the structure of macro-invertebrates (Ardabil province)

Qualitative assessment by macro-invertebrates is known as a suitable method to determine the health of the river. In this study, the diversity and abundance of Baliqlu River macro-invertebrates were evaluated from June 2019 to May 2021. SamplingsSamples were taken by Surber sampler during four seasons and physico-chemical parameters such as TEM, DO, pH, BOD, and some heavy metals (Cd and Pb) were measured. Diversity indices (Shannon-Wiener), and biotic indices (EPT, HFBI, and BMWP) were calculated in four stations. A total of 8328 macro-invertebrates from the Diptera, Ephemeroptera, and Isopoda were identified. The highest frequency percentage of the dominant groups was related to the Caenidaed, Chironomidae, and Simuliidae. The results of heavy metal accumulation in two classes showed more cadmium and lead accumulation in the Clitellata class (suborder Hirudinea) than the Insecta class (Caenidae family). The results of conventional comparative analysis (CCA) demonstrate that the distribution of most macro-invertebrate families is influenced by the DO parameter. According to the HFBI, the water quality decreased from upstream to downstream in all seasons, and the level of pollution was higher in station 5 compared to other stations, due to human activities, cattle crossing, and sewage output of fish farms.