Water Pollution Effect on Community Structure and Diversity of fish in Shatt al-Arab River, southern Iraq

Abstract

Shatt al-Arab River is subjected to extreme levels of environmental degradation due to decreased inflow of freshwater, intrusion of salinity and industrial/agricultural wastes. The paper evaluated the fish diversity and heavy metal pollution within a 120-km long area between Qurna (freshwater) and Fao (marine-influenced) between the months of February and September 2024. Standardized gill nets collected a total of 2,847 fish specimens representing 24 species, 12 families and this was the effort (3 nets 12 hours per site per month). The species richness of fish decreased greatly downstream (ANOVA: F=18.4, p=0.001), as there were 18 species at Site 1 and 9 species at Site 4. Shannon diversity index (H 7 ) was between 2.41 (Site 1) and 1.28 (Site 4). The native freshwater species declined by 72 per cent upstream and 28 per cent downstream by euryhaline/marine species. Analysis of heavy metals showed that Pb levels in water (18.4-42.6 ug/L) is more than WHO (10 ug/L) recommendations in Sites 3-4. Cd levels in fish muscle tissue (0.12-0.38 ug /g wet weight) were greater than FAO/WHO limit (0.05 ug/g wet weight) in Planiliza abu and Coptodon zillii at downstream localities. The bioaccumulation factors were between 156 and 2840. Such results reveal the extreme amount of ecological degradation and food safety issues, which require immediate management actions such as the restoration of the freshwater flows and the prevention of pollution.