The effect of pollutants from the diyala tributary on the environmental characteristics of the tigris river water

The Tigris River is the main water resource in central Iraq, yet its quality is increasingly threatened by pollutants from its tributaries. This study assessed the impact of the Diyala tributary on the environmental characteristics of the Tigris River by analyzing physicochemical and biological parameters across four stations from October 2024 to June 2025. Results revealed elevated turbidity, total dissolved solids, biological and chemical oxygen demand, and nutrient concentrations downstream of the confluence, particularly during low-flow seasons. Dissolved oxygen levels decreased significantly, reflecting high organic loads from untreated sewage and agricultural runoff. This study highlights significant spatial variation in the relative abundance and composition of rotifer species (Rotifera) across the four sampling stations in the Diyala and Tigris rivers and their confluence. The dominance of specific taxa such as Rotaria sp., R. neplunia, Monostyla bulla, and Keratella quadrata reflected differences in organic load, nutrient enrichment, and hydrological conditions. These findings confirm that rotifers are sensitive bioindicators of ecological status and water quality, providing reliable insights into the impacts of natural variability and anthropogenic activities on river ecosystems. Consequently, the study underscores the importance of using rotifer communities as effective tools for ecological monitoring and river management strategies.