Diversity and Seasonal Variation of Zooplankton in Avudaiyar Pond, Tiruchendur, Tamil Nadu, India

Background: Zooplankton constitute an essential component of freshwater ecosystems, functioning as key intermediaries in aquatic food webs and serving as sensitive indicators of environmental change. Aims: The present study investigates the diversity, composition, and seasonal variation of zooplankton communities in Avudaiyar Pond, located in Tiruchendur, Thoothukudi District, Tamil Nadu, South India, over one year from January 2024 to December 2024. Method: Zooplankton samples were collected monthly from selected sites using a standard plankton net with a mesh size of 60 μm, and organisms were identified to the species level using standard taxonomic keys. A total of 55 zooplankton species belonging to four major taxonomic groups—Rotifera, Cladocera, Copepoda, and Ostracoda—were recorded during the study period. Among these groups, Rotifera emerged as the dominant group, contributing the highest species richness, followed by Cladocera and Copepoda, while Ostracoda showed comparatively lower diversity. Results: Distinct seasonal variations were observed in zooplankton abundance and species richness, with higher diversity during the summer and post-monsoon seasons and a marked decline during the monsoon period. The reduced diversity during the monsoon season is attributed to increased water inflow, turbidity, and hydrological disturbance. Diversity index analysis revealed moderately high Shannon diversity and evenness values, indicating a stable and well-balanced zooplankton community and suggesting favourable ecological conditions in Avudaiyar Pond. Conclusion: The findings highlight the effectiveness of zooplankton as bioindicators of freshwater ecosystem health and provide valuable baseline ecological data for long-term monitoring, conservation planning, and sustainable management of freshwater resources in the Tiruchendur region.