RESEARCH ARTICLE Physicochemical and biological status of Aghlagan river, Iran: effects of seasonal changes and point source pollution Ehsan Asadi Sharif 1 & Behnaz Yahyavi 2 & Abolfazl Bayrami 2 & Shima Rahim Pouran 3 & Ehsan Atazadeh 4 & Ramesh Singh 5,6 & Abdul Aziz Abdul Raman 7 Received: 22 June 2020 /Accepted: 12 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract Although the macroinvertebrates have been widely used as bio-indicator for river water quality assessment in developed countries, its application is new in Iran and data on the health status of the most ecologically important rivers in Iran is scarce. The present study aimed at monitoring and assessing the ecological quality of Aghlagan river, northwest of Iran, using integrated physicochemical-biological approaches. A total of 14,423 samplings were carried out from the headwater to downstream sites at four stations (S1, 2, 3, 4) by a Surber sampler (30 cm × 30 cm) from June 2018 to April 2019. The results obtained from macroinvertebrate biotic index revealed that the genera of Gammarus (Amphipoda) and Baetis (Ephemeroptera) were the most abundant in all seasons. The PAST software was applied to analyze the diversity indices (Shannon-Weiner diversity, Evenness, and Simpson indices). Based on the cluster analysis, S3 established the least similarity to other stations. The average frequency of each macroinvertebrate species was determined by one-factor analysis of similarities (ANOSIM). In accordance with canonical correspondence analysis (CCA), temperature and phosphate were found as the dominant factors effecting the macroinvertebrate assemblage and distribution. Moreover, the results obtained from the biological indices concluded very good quality of S4 by Helsinhoff and EPT indices and fair quality using BMWP index. The data on the macrobenthos assemblage and dynamics in the Aghlagan river across a hydraulic gradient provided useful information on water management efforts that assist us to find sustainable solutions for the enhanced quality of the river by balancing environmental and human values. Keywords Biological indices . Freshwater . Macroinvertebrates . Organic pollution . Seasonal effect Abbreviations ANOSIM Analysis of Similarity APHA American Public Health Association AusRivAS Australian River Assessment System BEAST BEnthic Assessment of SedimenT BIBI Benthic Index for Biotic Integrity BMWP Biological Monitoring Working Party CCA Canonical correspondence analysis DO Dissolved oxygen EC Electrical conductivity Responsible Editor: Thomas Hein * Abolfazl Bayrami abolfazlbayrami@gmail.com; a_bayrami@uma.ac.ir * Shima Rahim Pouran rahimpooran@yahoo.com 1 Department of Fisheries Sciences, Faculty of Natural Resources, University of Guilan, Guilan, Rasht, Iran 2 Department of Biology, Faculty of Science, University of Mohaghegh Ardabili, Ardabil, Iran 3 Department of Environmental and Occupational Health, Social Determinants of Health Research Centre, Ardabil University of Medical Sciences, Ardabil, Iran 4 Department of Biology, Faculty of Natural Sciences, University of Tabriz, Tabriz, Iran 5 Department of Mechanical Engineering, Centre of Advanced Manufacturing and Materials Processing, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia 6 Department of Mechanical Engineering, Faculty of Engineering, Universiti Teknologi Brunei, Tunku Highway, Gadong BE1410, Darussalam, Brunei 7 Department of Chemical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia Environmental Science and Pollution Research https://doi.org/10.1007/s11356-020-11660-9