Zooplankton is an important bioindicator of ecosystem functioning. Knowledge of the seasonal fluctuation in the zooplankton population in estuarine waters of the Indian Sundarbans is rather limited. In the present study, we analysed the community structure of zooplankton assemblages and their spatio-temporal variations based on different multivariate statistics and indicator value analysis. A total of 56 taxa were identified and the density was primarily dominated by planktonic copepods and few meroplankton communities during four sampling seasons. The most abundant species were: Acartia spinicauda, Acartia sp., Bestiolina similis, Euterpina acutifrons, Labidocera acuta, Paracalanus aculeatus, Paracalanus parvus and Paracalanus indicus. Canonical Correspondence Analysis highlighted that temperature, pH, DO, salinity and nutrients were the prevailing environmental parameters associated with significant spatio-temporal changes of zooplankton distribution in this area. The highest abundance of zooplankton was recorded in winter, followed by monsoon, summer and spring. Throughout the study period, different zooplankton indices were observed in good condition. Seasonal occurrence of dominant zooplankton with high IndVal index was markedly observed and it might be used as a potential bioindicator for a particular season and environmental condition in this estuarine complex. The results of this study provide evidence for the presence of warm water species in the estuarine waters of the Indian Sundarbans and can be a clear indication of climate change-mediated elevated temperature in the estuarine system. Our results underscore the high diversity of zooplankton from mangrove dominated estuarine complex and emphasize the need for long-term monitoring in ecologically fragile ecosystems like the Sundarbans Estuarine System.

浮游动物是生态系统功能的重要生物指标。关于印度桑达班河河口浮游动物种群季节性波动的了解非常有限。在本研究中，我们基于不同的多元统计量和指标值分析，分析了浮游动物组合的群落结构及其时空变化。在四个采样季节中，总共鉴定出56个分类单元，其密度主要由浮游pe足类和浮游鱼类组成。最丰富的物种是：car螨，,螨。，Bestiolina similis，Euterpina acutifrons，Labidocera acuta，Paracalanus aculeatus，Paracalanus parvus和Paracalanus indicus。典型对应分析强调，温度，pH，DO，盐度和养分是该区域浮游动物分布时空变化显着相关的主要环境参数。冬季浮游动物的丰度最高，其次是季风，夏季和春季。在整个研究期间，观察到不同的浮游动物指数处于良好状态。高IndVal的优势浮游动物的季节性发生明显观察到该指数，并且可以用作该河口综合体中特定季节和环境条件的潜在生物指标。这项研究的结果为印度桑达班河河口水中存在温水物种提供了证据，并且可以清楚地表明气候变化介导的河口系统温度升高。我们的结果强调了红树林为主的河口区浮游动物的高度多样性，并强调需要对生态脆弱的生态系统（如Sundarbans河口系统）进行长期监测。