Effect of Al-Dalmaj Marsh Discharge Canal on Copepoda Community and Water Quality in the Main Outfall Drain River in Al-Qadisiya Governorate by Using Biodiversity and CCME-WQ Indices

The research evaluated the effect of mixing the Dalmaj Marsh water with the Main Outfall Drain River, which reflected on copepod communities and its water quality. Three sites were selected to test water variables as well as the Copepoda diversity index (Shannon-Wiener index) and density in 2023. The turbidity, DO, BOD₅, and TDS exceeded the acceptable limits for aquatic life. The most effective parameters were TDS, BOD₅, and turbidity, which contributed to creating a low water quality for the river due to it being used for the disposal of agricultural effluents. The CCME-WQ Index values of the sites ranged from marginal in site 2 to poor quality in sites 1 and 3. Site 3 had the lowest quality because it had double the TDS values and the highest turbidity values due to the water coming from the marsh canal to the river. The highest densities and diversities were downstream meeting point of Al-Dalmaj Marsh Discharge Canal with the Main Outfall Drain River (MOD) (at site 3), compared with site 2. The canal water affected copepod density and diversity due to this fauna was positively influenced by high TDS and DO caused by the canal water in the brackish river. The taxa numbers were 22 species. These few species number of the river may be due to the salinity being the most important factor changing the species and abundance of copepods, where it is predicted to be greater when salinity levels are nearer to that of freshwaters or marine waters than in brackish waters. Copepoda taxa of the river were most abundant by nauplii because they fed on a wide range of cell sizes of the phytoplankton as adults. Moreover, Cyclops sp. and Cyclops (♂) dominated Copepod communities due to their ability to survive seasonally unfavorable conditions.