Unveiling the spatiotemporal variation of zooplankton community structure and their relationship with environmental variables using multivariate analysis in a tropical mangrove estuary

Zooplankton assemblages and their relationship with environmental variables were studied in the Karanja estuary from January 2022 to March 2023. Thirty-seven zooplankton taxa were identified from the 60 samples, with copepoda emerging as the dominant group, contributing 33.6% of total abundance, followed by decapoda larvae (16.75%). Two-away ANOVA depicted significant spatiotemporal variation (p < 0.05) of zooplankton community structure. Zooplankton abundance peaked during the monsoon season (248.94 ± 24.35 ind. m⁻³), followed by the pre-monsoon (200.65 ± 7.40 ind. m⁻³), and post-monsoon seasons (83.9 ± 2. 85 ind. m⁻³). Multivariate, biotic-environmental (BIO-ENV), and redundancy analyses revealed salinity, temperature, nitrite, nitrate, and transparency are the prevailing environmental parameters affecting zooplankton dynamics. Seasonal diversity indices, including the Shannon–Wiener index (2.56 ± 0.35), Margalef index (4.25 ± 1.05), and Pielou’s index (0.97 ± 0.01) indicate a functionally healthy and diverse zooplankton community. Indicator species analysis (IndVal) revealed that Calanus sp., Centropages sp., Acartia sp., Oithona sp., and Diphyes dispar and Pleurobrachia pileus are potential indicators of environmental changes for a particular season. This study highlights the utility of zooplankton community structure as an indicator of estuarine ecosystem health and environmental variation. Identifying seasonal-specific indicator taxa facilitates practical tools for long-term monitoring systems. Overall, the findings provide a scientific basis for formulating effective management strategies for conserving the biodiversity of the Karanja estuary.