Evaluation of Water Quality of the Karun River in Ahvaz, Iran Based on Biological Indicators (Daphnia and Crustaceans)

Given the fact that the Karun River, as the most important source of water supply in Khuzestan province, has recently been affected by various pollutants such as sewage, monitoring its water quality is a necessity. This study aimed to determine the water quality of the Karun River based on biological indicators (Daphnia-crustaceans). In each season of the year, water samples were obtained from three stations at three different points along the river. After measuring the physical and chemical parameters, the samples were left to settle for 24 hours in the laboratory. Then 1 cc of the sediment was placed on the slide to study the diversity and frequency of crustaceans. Data were analyzed using SPSS version 21. In the present study, the frequency and variety of crustacean species isolated from the samples decreased from the initial station of the river to the final station. In addition, 27 species of Protozoa were isolated from three stations, of which Daphnia and Rotifer species with an average of 2.166 and 4.833 and standard deviation of 1.984 and 5.166, respectively had the highest frequency compared to other species. The results of the Pearson correlation showed that there is a direct and statistically significant relationship between dissolved oxygen (DO), Turbidity, Daphnia, and Rotifers. Based on the results of this study, it can be stated that the entry of effluents into river water causes a significant reduction in water quality, which in turn reduces the diversity and frequency of crustaceans living in the water. This is possibly due to an increase in sewage discharge from Ahvaz city to Karun river.