Seasonal Assessment of Zooplankton Communities in Ponds of Hisua Block, Nawada, Bihar

Abstract

Zooplankton constitute a key trophic link between primary producers and higher consumers and are widely used as bioindicators of freshwater ecosystem health. Seasonal changes in monsoon-driven systems of the Indo-Gangetic plain strongly influence hydrology and water quality, with consequences for plankton community structure. The present study investigated seasonal variation in zooplankton communities and basic physicochemical characteristics of three village ponds located in Hisua Block, Nawada District, Bihar, India, during pre-monsoon and post-monsoon periods in 2024. One pond each from Gopalpur, Bagodar, and Chandipur villages was selected as a representative perennial pond subjected to domestic and agricultural use. From each pond, five replicate plankton samples were collected in pre-monsoon and post-monsoon seasons, and zooplankton were quantified to major taxonomic groups (Cladocera, Copepoda, Ostracoda, Protozoa, and Rotifera). Concurrently, water depth, transparency, temperature, pH, dissolved oxygen, total alkalinity, and total hardness were measured following standard limnological protocols. Across all ponds, total zooplankton abundance increased from pre-monsoon to post-monsoon, driven mainly by marked rises in Cladocera, Copepoda, and Ostracoda, while Rotifera densities declined and Protozoa showed pond-specific trends. Rotifera dominated numerically in pre-monsoon, whereas the community became more evenly shared between rotifers, cladocerans, and copepods in post-monsoon. The results highlight clear seasonal restructuring of zooplankton communities associated with monsoon-related changes in water column depth and basic chemistry, and demonstrate the value of small village ponds in Hisua Block as productive freshwater habitats with potential implications for fisheries and local water management.