LIMNOLOGICAL ASPECTS OF ATRAI RIVER IN DINAJPUR, BANGLADESH

Abstract

Plankton functions the key role by transferring the food energy to higher trophic level in the ecosystem and often influenced by the environmental variability in inland waterbodies. A study was carried out to investigate plankton diversity and associated physico-chemical parameters of Atrai river from Dinajpur district in Bangladesh. Fortnight water sampling was performed at three sites namely Poromeshpur, Rubber dam and Mohonpur from Atrai river during July 2016 - February 2017. Collected samples were analyzed in the laboratory of Department of Fisheries Management, Faculty of Fisheries, Hajee Mohammad Danesh Science and Technology University (HSTU), Dinajpur. Shannon-Wiener index and Evenness index were used to calculate the diversity indices of plankton. ANOVA showed a significant variation (P < 0.05) in physico-chemical parameters among the sites. Mean value (±SD) of water temperature, pH and DO were 25.52±4.630C, 25.19±4.630C and 25.89±4.620C; 7.64±0.31, 7.81±0.31 and 7.47±0.35 and 7. 7.45±0.96, 7.91±0.98 and 7.06±1.06 mg/l in site 1, 2 and 3 respectively. Higher dissolved oxygen concentration was observed in site 1 while, pH was significantly variable among the sites during the study period. Moreover, there were significant variations in plankton abundance among the sites in Atrai river. However, the abundance of copepod and crustacean larvae did not show significant variation among the sites. A total of 57 genera of plankton were identified composed of 43 genera of phytoplankton and 14 genera of zooplankton. The abundance of chlorophyceae was higher (13.5×103 cells/l) followed by cyanophyceae (5.40×103 cells/l) at site 1 in January 2017. Total zooplankton found higher at site 1 in January 2017. Comparatively lower abundance of plankton (10.88×103 cells/l) was observed at site 3 in July 2016. Phytoplankton showed a Shannon-Wiener index value between 2.503 and 3.520 where, the Evenness index was from 0.884 to 0.941. In case of zooplankton Shannon-Wiener index showed the value from 1.468 to 2.295 and Evenness index value was 0.898-0.966. Overall, the diversity of plankton indicates variable biological productivity in the Atrai river of Dinajpur