ECOLOGY, DIVERSITY AND WATER-QUALITY RELATIONSHIPS OF ZOOPLANKTON IN THE GANGA RIVER AT BHOJPUR, INDIA

Abstract

This study evaluated the limnology and zooplankton of the Ganga River at Bhojpur, Bihar, India, from August 2024 to July 2026. We measured limnological parameters and corresponding biodiversity indices. Water temperature showed a negative relationship with pH, dissolved oxygen, total alkalinity, and hardness, while a direct relationship with electrical conductivity, total dissolved solids, chloride, nitrate, and phosphate. We identified 24 genera of zooplankton, including 7 Rotifera, 5 Protozoa, 5 Cladocera, 4 Copepoda, and 3 Ostracoda, ranging from 05 to 247 ind./L. The analysis showed that zooplankton density declined in post-monsoon and remained highest in summer due to the water body’s environmental and inflow characteristics. Density also showed a positive relationship with electrical conductivity, total dissolved solids, chloride, nitrate, and phosphate, but a negative correlation with water pH, dissolved oxygen, total alkalinity, and hardness. The Shannon-Wiener index, Simpson indices, Pielou’s evenness index, Menhinick’s index, and Margalef richness index assess zooplankton and the limnological profile. The diversity indices indicated moderate to high diversity and moderately polluted conditions.