This study investigates the changes in the distribution and species composition of macrobenthic communities in the Jajrood River in response to two major anthropogenic factors: the construction of the Latyan Dam and the discharge of urban wastewater. Seasonal sampling was conducted at five selected stations during the fall and winter of 2014 and the spring and summer of 2015. Stations located upstream of the dam represented relatively natural conditions, while stations downstream of the dam and within the urban area reflected regions influenced by human activities. Results indicated that downstream of the dam and within the urban zone, the density of pollution-tolerant species such as Chironomidae and Tubificidae increased significantly, whereas overall species diversity and the presence of pollution-sensitive taxa such as Ephemeroptera declined. These findings highlight the substantial impacts of dam construction and urban effluents on riverine benthic ecosystems.
