Abstract
The plankton are the crucial component of the riverine ecosystem as primary producers , food web components, and indicate the ecosystem health to inform management strategies. Thus, plankton biodiversity directly influences aquatic system productivity and sustainability. A study was conducted to assess the phytoplankton and zooplankton diversity and assemblage in relation to water quality in the upper stretch of Godavari River (Maharashtra) during the post-monsoon (2024) and pre-monsoon (2025) seasons . Over 90 plankton species were documented, with the rich taxonomic diversity of the phytoplankton assemblage, comprising 73 species, encompassing 11 classes, 29 orders, 40 families, and 60 genera. The class Bacillariophyceae displayed the highest richness, followed by Chlorophyceae. The zooplankton community comprised 23 species, dominated by Rotifera > Arthropoda > Cladocera. The phytoplankton and zooplankton abundance ranged from 0.48 – 1.2 ×10ˉ5 cell Lˉ1 and 0.2 – 8 ×10ˉ2 cell Lˉ1 . Spatially rich species diversity was recorded at Vishnupuri for both phytoplankton and zooplankton during the pre-monsoon season. Further, the highest Shannon-Wiener diversity index ( phyto: 4.0; zoo: 2.75), Simpson’s diversity index ( phyto: 0.98; zoo: 0.93 ), and Margalef richness index ( phyto: 3.94 ; zoo: 1.85) were recorded at Vishnupuri during the pre-monsoon season. This indicates a peak in species richness and evenness at this site and period. The diversity patterns suggest favorable ecological conditions supporting planktonic biodiversity during the pre-monsoon period. Statistical analysis revealed a significant correlation between the plankton groups and physicochemical parameters. This study results are crucial to understand the spatio-temporal variations in the plankton assemblage structure for monitoring the ecosystem health.
Keywords: Seasonal Variation, Phyto & zooplankton diversity, Physicochemical Parameters, Godavari River