Zooplankton distribution and its associated hydrology across Indian Sundarbans over the last decade: Insights from...

Zooplankton play a crucial role in estuarine ecosystems by aiding nutrient cycling through trophic chains and contributing to large-scale water filtration. The present review highlights the zooplankton research conducted over the last decade (2014-2024) in the Indian Sundarbans, with a focus on research trends, species distribution, hydrological associations, and long-term monitoring and conservation strategies. The study reveals a surge in zooplankton research after 2019, with an emphasis on both small- and large-scale studies. However, tidal creek/canals remain less explored compared to rivers. A lack of methodological standardization in zooplankton research is evident across the Indian Sundarbans. The Saptamukhi-Thakuran-Matla river stretch exhibited the highest species diversity, with 70 species recorded. Similarly, the tidal creeks and canals of Sagar Island were identified as species-rich habitats, with 63 species reported. Oithona brevicornis was found in seven riverine stretches, while Paracalanus parvus and Labidocera euchaeta were each recorded from six rivers, but Bestiolina similis was mostly reported as the numerically predominant zooplankton species. Salinity emerged as the most influential hydrological factor for zooplankton distribution, followed by dissolved oxygen and water temperature. However, increasing pollution, climate change-induced cyclones, salinization, and human activities are threatening zooplankton communities of the Indian Sundarbans. Furthermore, the review underscores the need for long-term monitoring strategies in the Sundarbans, by addressing the integration of remote sensing method, automated devices, data repositories, and ecological modeling approaches. Additionally, the present review recommends future policies for zooplankton conservation, emphasizing habitat protection, water quality assessment, stakeholder engagement, and securing funding to implement long-term monitoring initiatives.