Biological Evaluation of Epilithic Algal Distribution; An Applicable Approach for River Water Quality Assessment (Case Studies of Karw and Bozhan Rivers)

At the same time with development of agricultural and industrial activities and reduction of quantity and quality of water resources, assessment of surface water resources quality has been paid more attention. Due to limitations of conventional methods for surface water quality assessment, development of alternative methods has been considered for monitoring water quality. For example, biomonitoring using alga is a proper indicator for surface water quality assessment. In this study, the relationship between epilithic alga population and concentration of common nutrient residuals including nitrate, nitrite, phosphate, sulfate and water-soluble iron in Bozhan and Kharw Rivers in Neishabour was determined in two consecutive years; 2017 and 2018. IRWQISC quality index for Bozhan and Kharw River was calculated as 50.03, 66.65% and 47.66, 55.69% during 2017-2018 respectively, which ranged between moderate to relatively good. Significant differences were observed in the concentrations of phosphate and iron in Bozhan River. The source of iron could be due to effluent from Bozhan village gardens. This gardens use Sequesteren iron fertilizer with no management. Due to the direct role of these nutrients in stimulating growth of alga communities, distribution rate of epilithic alga in Bozhan River was shown to be more than the ones in Kharw River. Therefore, investigation of changes in alga communities as a proper bioindicator could be useful for assessment and prediction of residuals such as phosphate and iron ions in water resources. These findings could be used in better recommendations for gardening and more accurate management of drainage water entering the riverside by studying the distribution of algal communities.