As part of its commitment to advancing scientific research in aquatic ecology and biodiversity, Rend Raad Ahmed Majeed, a master’s student in the Department of Biology at the College of Education for Pure Sciences (Ibn Al-Haitham), defended her thesis entitled “The Effect of the Diyala River on Rotifer Diversity in the Southern Section of the Tigris River,” supervised by Assistant Professor Intisar Faisal Abd.
The study aimed to assess the influence of the Diyala River, a tributary of the Tigris, on the physicochemical and biological characteristics of Tigris River water upstream and downstream of the confluence. It also investigated quantitative and qualitative variations in rotifer communities in the Diyala and Tigris rivers and applied several biodiversity indices to evaluate the condition of the aquatic ecosystem and its response to pollution.
The research involved monthly sampling at four sites from October 2024 to July 2025. Sixteen environmental parameters were measured, including air and water temperatures, electrical conductivity, pH, salinity, dissolved oxygen, biochemical oxygen demand (BOD), turbidity, total hardness, calcium and magnesium concentrations, nitrate and phosphate concentrations, and dissolved and suspended solids.
The study also examined rotifer communities in terms of total density, relative abundance, species constancy, species richness, diversity, evenness, and similarity among sampling sites. Several ecological indices were employed, and the collected data were statistically analysed using SAS software. Correlation coefficients were also calculated to investigate relationships among the measured environmental variables.
The results identified 81 rotifer taxonomic units, with substantial variation in total density among the study sites, ranging from 25 to 55,866.59 individuals/m³. Seasonal variations were also observed in biodiversity indices. The highest species-richness values were recorded in spring, whereas the highest Shannon–Wiener diversity index values occurred in winter. Diversity and evenness indices declined during summer, indicating seasonal variations in the environmental conditions affecting rotifer communities.
The water-quality findings revealed elevated biochemical oxygen demand at some sampling sites, with values ranging from 0.8 to 78.2 mg/L, indicating evidence of organic pollution, particularly in the Diyala River. Elevated total hardness and calcium and magnesium concentrations were also recorded at certain sites. The findings further indicated that variations in the physicochemical characteristics of the water coincided with differences in rotifer density and diversity, highlighting the potential value of rotifers as biological indicators for assessing the condition of aquatic ecosystems.
The thesis recommended strengthening environmental monitoring of river pollution sources, treating domestic, municipal, agricultural, and industrial wastewater before discharge, and establishing monitoring stations for the continuous assessment of water quality. It also recommended further investigations into organic and bacterial pollutants, heavy metals, pesticides, and agricultural fertilisers. In addition, the study emphasised the importance of expanding taxonomic and ecological investigations of zooplankton communities and using the findings as a reference database for assessing rotifer communities in Iraqi aquatic environments.
The significance of this research lies in its contribution to scientific knowledge of rotifer diversity and water-quality conditions in the area where the Diyala River joins the Tigris River. The findings may support water-pollution assessment, biodiversity conservation, and the sustainable management of water resources.
The examination committee comprised Professor Nibras Lafta Abdul Qadir, Chair; Assistant Professor Rawaa Jaafar Hameed, Member; Chief Researcher Muhannad Ramzi Nashat, Member; and Assistant Professor Intisar Faisal Abd Mohammed, Member and Supervisor.
The research is aligned with several United Nations Sustainable Development Goals, particularly:
SDG 6: Clean Water and Sanitation — through the assessment of water quality, the identification of pollution indicators, and the emphasis on wastewater treatment and the monitoring of pollution sources.
SDG 14: Life Below Water — through the investigation of aquatic microbial biodiversity and the assessment of how rotifer communities respond to environmental changes and pollution.
SDG 3: Good Health and Well-being — by supporting scientific efforts to improve water quality and reduce potential health risks associated with contaminated water resources.
SDG 15: Life on Land — through strengthening scientific understanding of biodiversity and promoting the protection of ecosystems associated with natural resources.
This research highlights the importance of applying scientific investigation to identify environmental challenges and establish an evidence base that supports the protection of Iraqi rivers, the improvement of water quality, and the conservation of aquatic biodiversity.
