Abstract
Freshwater reservoirs constitute one of India's most extensive and ecologically significant aquatic habitat types, with over 5,000 large and medium reservoirs providing water for irrigation, municipal supply, and hydropower generation.
Zooplankton communities in these systems serve as critical trophic links between primary producers and fish, regulate
phytoplankton biomass through grazing, and contribute substantially to nutrient cycling. Despite this ecological
importance, the zooplankton diversity of Indian reservoirs remains poorly synthesised, with published surveys scattered
across regional journals spanning six decades. This review synthesises published data on zooplankton species richness
and community composition from 87 Indian reservoirs documented in 146 studies published between 1960 and 2021,
covering all major biogeographic zones. A total of 624 zooplankton taxa are recorded across reviewed studies,
comprising 284 Rotifera, 196 Cladocera, 88 Copepoda, and 56 Protozoa and other microzooplankton. Species richness
per reservoir ranged from 18 to 124 taxa, with highest richness in peninsular reservoirs of the Western Ghats foothills.
Trophic state, water retention time, and catchment land use are identified as primary determinants of zooplankton
community composition. Eutrophication, driven by agricultural and urban runoff, is the dominant threat to zooplankton
diversity, promoting cyanobacteria-tolerant rotifer dominance at the expense of large-bodied cladocerans. Conservation
and management recommendations for maintaining zooplankton diversity in Indian reservoirs are presented.