Seasonal Variation in Water Quality and Plankton Communities in a Eutrophic Tropical Lake (Central, India)

Abstract

The study was conducted during the year 2024 at Koteshwar Lake, Ramtek, Maharashtra, India to evaluate seasonal variations in water quality and plankton community structure and to determine the trophic status of the lake in relation to monsoon-driven nutrient inputs. Monthly sampling was performed at four representative stations covering inlet, settlement-influenced, open water, and littoral zones. Physicochemical parameters, nutrient concentrations, biochemical oxygen demand, chemical oxygen demand, chlorophyll a, and plankton diversity were analysed using standard methods. Statistical analyses included one-way ANOVA, correlation analysis, and principal component analysis. The lake exhibited pronounced seasonal variability, with higher temperatures during the pre-monsoon period and lower dissolved oxygen levels. Nutrient concentrations, biochemical oxygen demand, and chemical oxygen demand increased significantly during the monsoon, indicating strong external nutrient loading. Chlorophyll a concentration peaked during the post-monsoon season, reflecting enhanced primary productivity. Multivariate analysis identified nutrient variables as the major factors influencing ecological variation. Phytoplankton diversity remained relatively stable, whereas zooplankton showed marked seasonal fluctuations with greater abundance during the monsoon. The dominance of nutrient-tolerant taxa confirmed eutrophic conditions. The findings demonstrated that monsoon-driven nutrient enrichment and catchment influence strongly regulated the ecological dynamics of Koteshwar Lake and highlighted the importance of catchment-level management strategies for long-term lake conservation.