This research aimed to assess the diversity and seasonal distribution of zooplankton from January to December 2024 and analyze its relationship with key physico-chemical parameters in Lakshmipuram Lake, a tropical freshwater body located in Anakapalli District, Andhra Pradesh. Samples were collected seasonally—pre-monsoon (March-May), monsoon (June-September), and post-monsoon (October-December) — using a 64 ?m mesh plankton net. Samples were preserved in 4% formalin and analyzed in the laboratory using a Sedgwick-Rafter chamber under compound and stereo microscopes. Identification was performed using standard taxonomic keys. Concurrently, water samples were analyzed for various physico-chemical parameters including temperature, pH, turbidity, salinity, alkalinity, BOD, COD, nutrients, and more, following standard protocols.

Microscopic analysis revealed five major zooplankton groups, comprising 26 species: Rotifera (10 species), Cladocera (8 species), Copepoda (3 species), Ostracoda (3 species), and Protozoa (2 species). Rotifera emerged as the most dominant group, followed by Cladocera and Copepoda. Seasonal variations indicated that post-monsoon conditions supported the highest species richness and abundance, while monsoon showed relatively lower densities likely due to unfavorable environmental conditions. The highest density of Cladocera was recorded in post-monsoon (441 Ind/L), while Rotifera peaked in summer (438 Ind/L). Diversity indices indicated ecological stability, with the Shannon-Wiener Index rising from 2.4890 (pre-monsoon) to 2.9957 (post-monsoon), and Simpson’s Index values consistently above 0.93.

Correlation analysis revealed water quality parameters, particularly salinity, conductance, and nutrient levels play a significant role in shaping zooplankton biodiversity. The study emphasizes the sensitivity of zooplankton diversity to water quality and underlines their role as bioindicators for aquatic ecosystem health.

In conclusion, this study provides valuable baseline data on the zooplankton diversity of Lakshmipuram Lake, highlighting seasonal trends, ecological balance, and environmental influences, which are essential for future biomonitoring and conservation strategies.