The biodiverse zooplankton of Bhereki, Holmari and Ghotonga beels of Majuli River Island, the Brahmaputra river basin of upper Assam, northeast India (NEI) revealed total richness of 141 (118±8) species and thus suggested habitat diversity of these floodplain wetlands. Low community similarities, monthly richness variations and the cluster groupings affirmed heterogeneity of zooplankton species composition. Zooplankton formed the dominant component of net plankton in Ghotonga beel and showed sub-dominance in Bhereki and Holmari beels. Rotifera > Rhizopoda influenced zooplankton density in Bhereki and Ghotonga beels; Rhizopoda > Rotifera showed importance in Holmari beel; and Copepoda > Cladocera recorded sub-dominance in all beels. Zooplankton is characterized by higher species diversity and equitability, and lower dominance. The richness, abundance and diversity of zooplankton and abundance of the constituent groups followed oscillating monthly variations. While explaining limited influence of individual abiotic factors and low cumulative influence along two axes (vide Canonical Correspondence Analysis), our results suggested that zooplankton are largely generalists in terms of abiotic factors and thus hypothesized importance of factors associated with microhabitat. formalin. These samples were subsequently screened for various zooplankton species and their permanent mounts were made in polyvinyl alcohol-Lactophenol mixture.Monthly quantitative zooplankton samples were also obtained by filtering 25 litres of the lake water through nylobolt plankton net (No. 25). Individual collections were then concentrated to 25 ml each and preserved in 5% formalin. The quantitative enumeration (n/l) was done with the help of a Sedgewick-Rafter counting cell. The zooplankton was identified following the works of [1,[14][15][16][17][18][19]. Quantitative samples were analyzed for abundance of zooplankton. Community similarity (Sørensen's index) and species diversity (Shannon's index) were calculated following [20,21]. ANOVA was used to analyze the significance of temporal variation of the biotic communities. Ecological relationships between abiotic and biotic parameters of Bhereki beel, Holmari beel and Ghotonga beel were determined by simple correlation co-efficient (r 1, r 2 and r 3, respectively); P values were calculated and their significance was ascertained after the use of Bonferroni correction. The canonical correspondence analysis (XLSTAT 2014) was done to analyse cumulative influence of seventeen abiotic parameters (water temperature, rainfall, pH, specific conductivity, dissolved oxygen, free CO 2 , total alkalinity, total hardness, calcium, magnesium, chloride, dissolved organic matter, total dissolved solids, phosphate, nitrate, sulphate and silicate) on the zooplankton assemblages.