Assessing the Impact of Urbanization on Aquatic Ecosystem Health Through Water Quality Habitat Transformation and Biodiversity Analysis

Freshwater ecosystems are changing rapidly in response to an increase in impervious surfaces, wastewater discharge, stormwater runoff, and riparian encroachment; however, the cumulative effects on water quality, ecosystem condition, and biological communities are not typically measured in one framework. The present study compared the health of aquatic ecosystems across an urbanization gradient in a tropical urban river–wetland corridor. In 2024, a total of 60 stations were sampled in four seasons, 15 stations in each season, in 15 urbanization areas representing low, moderate, and high urbanization. The Water Quality Index (WQI), Habitat Integrity Score, biodiversity indicators, correlation and regression, Kruskal–Wallis tests, and principal component analysis were used to estimate twelve physicochemical parameters, land-use and habitat indicators, and macroinvertebrate and fish communities. All these components were combined into an Aquatic Ecosystem Health Index (AEHI). The dissolved oxygen (DO) decreased between the low- to high-urbanization zones, from 7.2 to 3.1 mg L-1, while BOD₅ increased from 2.1 to 12.6 mg L-1 and nitrate-N from 0.82 to 5.93 mg L-1. The WQI rose from 38.6 to 162.7, and impervious cover accounted for 83% of the variability for dissolved oxygen. Riparian cover and Shannon diversity decreased by 79.6% and 57.0%, respectively, while the taxa of the tolerant group increased to 72.6% and the EPT abundance decreased to 3.2%. The AEHI decreased from 0.83 to 0.19, while PC1 accounted for 68.4% of the total variance. The results indicate that urbanization causes simultaneous degradation of water quality, habitat structure, and biodiversity. Wastewater control, riparian restoration, and impervious-surface management are thus priorities in the urban aquatic ecosystem conservation program.