Bioindicators and Ecological Assessment of Drigh Lake Water Quality: Physico-Chemical, Biological and Hydrological Characterization Under Anthropogenic Influences

Abstract

Drigh Lake is a historically important freshwater lake located at N 27° 34’, E 68°02’ in the Province of Sindh, approximately 18 km northwest of Larkana and 10 km from Qambar towards Gaibi Dero Road at District Qambar @ Shahdadkot. The current study offers a comprehensive framework for assessing the water quality of Drigh Lake by integrating bioindicators with ecological and physico-chemical assessments to identify anthropogenic stressors causing environmental degradation. Water quality was evaluated through hydrological parameters including Temperature, Transparency, pH, Total Suspended Solids (TSS), Total Dissolved Solids (TDS), Salinity, Alkalinity, Chlorides, and Dissolved Oxygen, along with biological investigation revealed diverse phytoplankton communities dominated by Euglenophyta, Chlorophyta, Cynophayta, and Bacillariophyta, with phytoplankton abundance exceeding that of zooplankton. Zooplankton diversity included mainly Rotifera, Copepoda, and Cladocera. Seasonal variations significantly influenced plankton composition and abundance, thereby affecting water quality. The dominance of marshy, floating, and submerged macrophytes such as Typha domingensis, Phragmites vallatoria, Eichhornia crassipes, Nelumbo nucifera, and Hydrilla verticillate indicates eutrophic conditions driven by high nitrogen and phosphorus levels. The lake supports a productive fish community, including major carps and predatory species. This study showed that sewage discharge and agricultural runoff encouraged eutrophication and biodiversity loss. Diversity indices and bioassays highlight ecosystem vulnerability, emphasizing the need for certain management strategies to reduce pollution load, restore ecological balance, and ensure sustainable lake ecosystem.