Vaibhavi Bhausaheb Pagar and Ramakant Keshavrao Patil
Abstract
Freshwater rivers play a vital role in sustaining aquatic biodiversity, supporting livelihoods, and maintaining ecological balance. However, increasing anthropogenic activities altered river health, especially in semiarid zones of India. This study presents a seasonal hydrobiological assessment of the Girna River in Kalwan Taluka, Maharashtra, focusing on the interaction between physico-chemical parameters and algal community dynamics across four georeferenced stations (GSS IâIV) from July 2023 to June 2024. Physico-chemical analysis followed APHA (2017) protocols and included parameters such as pH, temperature, free CO2, nitrate, phosphate, sulphate, total hardness, alkalinity, and TDS. Algal samples were collected and identified to assess composition, abundance, and pollution tolerance using Palmerâs Pollution Index and the Saprobity Index. Results revealed a spatial and seasonal gradient in water quality: upstream sites (GSS I) showed lower pollution loads and higher diatom diversity, while midstream stations (GSS II, III) exhibited elevated nutrient concentrations and dominance of chlorophytes and cyanophytes, indicating eutrophication. GSS III recorded the highest Palmer Index, suggesting organic enrichment, while saprobity analysis confirmed polysaprobic conditions. Seasonal algal peaks in summer corresponded with high nutrient levels and temperature. The findings demonstrate the sensitivity of algal communities to environmental fluctuations and reinforce their utility as reliable bioindicators for riverine ecosystem assessment. This study provides critical ecological baselines and supports the use of biological indices in freshwater monitoring programs for sustainable river basin management.