Plankton diversity of two hill rivers of Bangladesh

Abstract

This study was made for one year and dealt with the phytoplankton and zooplankton of the rivers Halda and Karnaphuli with respect to their monthly variations, abundance, and diversity as determined by Shannon-Wiener diversity index and Evenness index for major taxa. A total of 23 and 18 genera belonging to five groups of phytoplankton (Blue green Algae, Green Algae, Non-motile green Algae, Desmids, and Diatoms) and a total of 16 and 13 genera belonging to four groups of zooplankton (Cladocera, Copepoda, Rotifera and Protozoa) were recorded in Halda and Karnaphuli rivers respectively. Monthly mean total numbers of phytoplankton varied from 13927/m³ to 197304/m³ and zooplankton from 21278/m³ to 86616/m³ in the Halda River, and from 11993/m³ to 99297/m³ phytoplankton and 15797/m³ to 92204/m³ zooplankton in the Karnaphuli River. Halda River was found to be richer in phytoplankton than the Karnaphuli River. The Shannon-Wiener diversity index (H′) for phytoplankton ranged from 0.00 to 1.85, that of zooplankton from 0.00 to 2.00, and the evenness (J′) of phytoplankton from 0.00 to 0.99 and of zooplankton from 0.00 to 1.00 in the Halda and Karnaphuli rivers, respectively. Diversity indices (H′) of these two rivers indicated poor to very poor water quality. Evenness values for both rivers indicated that community members were not distributed equally and that the water bodies were polluted.

Bangladesh J. Zool. 54(2): 167-182, 2026