Diversity of Biological Communities Along the Major Rivers of Sundarbans in Bangladesh

Despite recent unexpected and irreversible changes in the environment brought on by global climate change, the largest mangrove forest of Sundarbans is still considered a biodiversity hotspot in Bangladesh. This study aimed to assess the abundance, diversity indices and richness of plankton and fisheries resources of the four major rivers (Pasur, Sela, Sibsa, and Kapotakkho) in Sundarbans. During the study period (July 2017 to November 2018), the range of pH, temperature, salinity and dissolved oxygen values were from 7.1 to 8.7, 25 °C to 32.8 °C, 1.5 ‰ to 23 ‰ and 4.3 mg.L-1 to 7.7 mg.L-1 , respectively. Phytoplankton and zooplankton communities were represented by 29 and 18 species, respectively. The number of plankton per litre was highest in the Pasur River during both pre-monsoon and post-monsoon season. A total of 186 species of fish and crustaceans were recorded in the rivers of Sundarbans. The plankton, fish and crustacean diversity indices were as follows: Shannon-Wiener diversity (1.22 ± 0.27 to 3.48 ± 0.22), Margalef’s richness (1.29 ± 0.33 to 4.56 ± 0.45) and Pielou’s evenness (0.94 ± 0.04 to 1.02 ± 0.04). The results of the present study underscore new insight on riverine biological communities of the Sundarbans and emphasise the need for long-term monitoring in this ecologically fragile ecosystem