Zooplankton in the Indian Sundarbans: Distribution, water parameters, threats and opportunities

Zooplankton plays crucial roles in the food web by transferring energy from primary producers to higher trophic levels. The Indian Sundarbans, being a large mangrove-estuarine ecosystem, harbors rich aquatic diversity but endures several threats from anthropogenic activities. The present review comprehensively summarizes the status of zooplankton in the Indian Sundarbans. This review discusses the distribution of zooplankton across rivers and tidal creeks/canals, the influences of water parameters, possible threats, and conservation proposals through potential long-term monitoring. Calanoid copepods (similar to 32.02 %) are predominant in the Indian Sundarbans, followed by Choreotrichida (similar to 17.8 %), Cyclopoida (similar to 8.67 %), Decapoda (similar to 7.55 %), and Harpacticoida (similar to 5.66 %). As per previous studies, calanoid Pseudodiaptomus serricaudatus is predominant in rivers, followed by Paracalanus parvus, Bestiolina similis, Acartia plumosa, and Acartiella tortaniformis. Salinity is the key water parameter influencing the assemblage and distribution of zooplankton in the Indian Sundarbans. Zooplankton in this region face several threats, such as pollution, natural disasters, and the development of river dykes, which may raise serious concerns about their survival. This review recommends conservation and long-term monitoring programs, including mass culture, database development, and the use of advanced techniques to support conservation policies for zooplankton communities. Special emphasis is given to habitat conservation and the implementation of river conservation programs like "Namami Gange" initiated by the Government of India. Additionally, this review outlines a baseline draft on zooplankton monitoring in the Indian Sundarbans, addressing sampling frequency, sampling locations, and possible funding opportunities for the smooth running of this program.