Ecological water health assessment using benthic macroinvertebrate communities (case study: the Ghezel Ozan River in Zanjan Province, Iran).

Macroinvertebrates are without spinal cord living organisms that spend their main phases of metamorphosis in water; so, changing the ecological structure of their communities represents environmental health condition. The main purpose of this study was to identify the macroinvertebrate families as a biological indicator and, consequently, determining the water ecological quality in the Ghezel Ozan River, NW Iran. The sampling was conducted at 18 stations in autumn 2017. At the same time, dissolved oxygen, temperature, turbidity, electrical conductivity, fecal and total coliform, BOD5, COD, phosphate, nitrate, nitrite, ammonia, chloride, and sulfate were measured based on APHA in each station. Then, based on the collected data, the NSFWQI, IRWQIsc, EQR, and BMWP/ASPT indices were calculated. In total, 1778 individual belong to 12 orders and 22 families were identified, which the most abundant order was Ephemeroptera by 47.8%. Except for the pH, COD, DO, and nitrogen compounds, other studied parameters were exceeded from their acceptable level. It seems that the geological characteristics are very effective in changing the parameters especially salinity. The best water quality was at Kharmaneh-Sar station (7), which runs from the protected area at high altitudes without human pressure. Also, the trend of water quality decreases from the upstream to downstream, which is completely in line with human activities. Therefore, the results of this study can well illustrate the role of land use and geology changes on the macroinvertebrate communities, which can be used to evaluate the ecological integrity of the river. Regular monitoring of river water quality and controlling and managing the quantity and quality of fish farms along the river can help in the ecological health of the river.