Ecological Health Assessment of Vandiyur Lake, Madurai, India: A Multi- parametric Approach Using Physico-chemical and Planktonic Indicators

Vandiyur Lake, a critical urban wetland in Madurai, faces ecological degradation mainly from encroachment and untreated sewage discharge. This study evaluates the lake’s ecological health from December 2023 to March 2024 using physico-chemical profiling and planktonic analyses. Over the study period, both the physico-chemical profiles and planktonic community structures showed significant spatial and seasonal variability. In sampling station II the highest organic loading was observed, with total alkalinity (321 mg/L), free CO₂ (22.25 mg/L), total nitrogen (1.16 mg/L), total phosphorus (1.01 mg/L), and BOD (6.66 mg/L) coinciding with suppressed dissolved oxygen (6.82 mg/L). A total of 25 phytoplankton and 45 zooplankton species were recorded. Phytoplanktons were dominated by Cyanophyceae and Bacillariophyceae including Euglena sp., Microcystis sp. Closterium sp., Asterionella sp., and Anabaena sp., while Rotifera was the most diverse zooplankton group, including Branchionis spp., Daphnis sp., and Diaptomus sp. These taxa are widely recognized as reliable bio-indicators of eutrophication and organic pollution. Diversity indices indicated that Station I had higher species diversity and evenness, reflecting a relatively stable ecosystem. In contrast, Station II showed high species richness but lower diversity and evenness, suggesting dominance of pollution-tolerant species due to anthropogenic stress. Overall, these findings suggest an ecological imbalance caused by nutrient enrichment and sewage discharge, emphasizing the urgent need for management strategies to restore the health of the lake’s ecological health.