Qualitative Assessment and Group-wise Composition of Zooplankton in Pimpalgaon (Wakhaji) Dam, Nagpur, Maharashtra, India

Zooplankton are an important component of freshwater ecosystems and contribute significantly to aquatic food webs and biological productivity. The present study was undertaken to assess the qualitative composition of zooplankton in Pimpalgaon (Wakhaji) Dam, Nagpur, Maharashtra, during a one-year study period from June 2023 to May 2024. Zooplankton samples were collected from the reservoir and examined for taxonomic identification using standard microscopic methods. The identified forms were documented and grouped into major taxonomic categories to describe the composition of the zooplankton assemblage. A total of 26 zooplankton forms comprising 25 distinct taxa and one developmental stage (nauplius larva) were recorded during the study, belonging to Rotifera, Cladocera and Copepoda. Rotifera represented the largest component with 11 taxa (44%), followed by Cladocera with 9 taxa (36%) and Copepoda with 5 taxa (20%). The rotifer assemblage included representatives of Brachionus, Keratella, Filinia, Asplanchna and Monostyla. The cladoceran assemblage included Diaphanosoma, Ceriodaphnia, Moina, Bosmina, Chydorus and Macrothrix. Copepoda were represented by genera including Mesocyclops, Eucyclops, Thermocyclops, Cyclops and Nauplius larva (the developmental stage of copepods). Seasonal succession was evident from the winter emergence of cold-tolerant cyclopoids (Cyclops spp.) to the predominance of thermotolerant rotifers during summer. The occurrence of several taxa commonly reported from freshwater ecosystems showed similarities with earlier observations from Indian reservoirs and lakes. However, differences in the representation of individual groups and taxa indicate variation in zooplankton composition among freshwater habitats. The present study provides a qualitative baseline of the zooplankton assemblage of Pimpalgaon (Wakhaji) Dam and contributes to the taxonomic documentation of its freshwater biological community.