Abstract

This study examines the biological integrity of the Abbasiyah River ecosystem within the city of Najaf, Iraq, through the examination of the spatio-temporal growth of Pseudomonas sp. as a main sign of degradation of the aquatic environment. A multidisciplinary strategy was used to measure the density of microorganisms at twenty sampling locations in four hydrological periods in 2024 to test how anthropogenic and environmental factors influence the density of microorganisms. The high-precision Membrane Filtration technique was used to perform laboratory isolation on selective Cetrimide Agar with spatial distribution calculated in ArcGIS 10.8 using the Inverse Distance Weighting (IDW) interpolation. These findings indicate the existence of critical biological threshold overages in comparison with the Iraqi Standard (417/2009) and WHO (2017) guidelines. Statistical testing showed that there were major seasonal peaks, with the maximum mean concentration of  cells/100ml observed during the Spring, which was equivalent to an increase of 130% compared to the lowest levels in Winter. The spatial mapping provided hotspots of high risks in sites S13, S18, and S14, in which the bacterial loads were always greater than cells/100ml because of the closeness to untreated municipal outfalls. Results reveal that 40% of the area of study is affected by sewage discharge, whereas 35% of the variance of the microbes is catalyzed by thermal optimization and stagnation of water. These opportunistic pathogens represent a significant disturbance of the microbial equilibrium of the aquatic system and represent systemic threats to the well-being of the native fish and riparian communities. The study concludes that urgent ecological repair, such as built wetlands and controlled environmental flow, is necessary to reduce the biological stress and to recover the natural self-cleaning capacity of the river.

Keywords: Aquatic microbiology, Spatio-temporal dynamics, Pseudomonas sp., Bio-indicator hotspots, Ecosystem health, Ecological restoration, Anthropogenic stressors