Planktonic abundance and diversity in an upstream area of the northeastern Bay of Bengal: Rabnabad channel, Patuakhali, Bangladesh

Author: Syeda Jasia Firdaws, Most Israt Jahan Mili, Saif Khan Sunny, Md. Ashifur Rahman Shaheen, Md. Shafiq Reza
DOI: doi.org/10.70279/bmj-v8-1032
Click here to view citation data

The Rabnabad channel, serving as the navigational route for the Payra Sea Port, is a significant upstream region in southern Patuakhali, Bangladesh. The channel holds significant economic value, supporting diverse aquatic resources and providing livelihoods for thousands of fishermen, yet it has been largely overlooked in ecosystem studies. Given its significance, the first initiative to study the planktonic community was carried out with the purpose of discussing the abundance and diversity. Field sampling and data collection were conducted in January 2021. A total of 30 phytoplankton species, belonging to 7 classes: Bacilariophyceae, Chlorophyceae, Coscinidiscophyceae, Cyanophyceae, Dynophyceae, Fragilariophyceae, Zygnematophyceae, and 7 zooplankton species across three classes: Branchiopoda, Copepoda, and Monogononta were identified. Among these, Coscinodiscophyceae (37%) was the most abundant phytoplankton class, while Branchiopoda (83%) dominated the zooplankton community. The highest phytoplankton and zooplankton abundances (48,101 cells L^-1 and 12,643 cells L^-1) were recorded in the upstream station, whereas lower abundances were observed at the estuary mouth where the channel meets the northern Bay of Bengal (BoB). Physicochemical parameters, including temperature (T), salinity (PSU), pH, dissolved oxygen (DO), and total dissolved solids (TDS), were also measured and found to have association with the planktonic distribution. TDS and salinity had a clear increasing trend from upstream to downstream stations, whereas plankton abundance showed a decreasing trend in the same direction. The species identified, along with the associated physicochemical data will provide a baseline for understanding the planktonic ecosystem of the Rabnabad channel. This will serve as a valuable reference to identify knowledge gap, and guide broader investigations into the ecosystem of the area throughout the seasons.