The beels or floodplain lakes are unique ecosystem supporting huge and diverse biodiversity, as represent the transition between land and water. In recent years, however, such beels have been subjected to indiscriminate exploitation leading to aberrations at various trophic levels. Most of the lakes are reeling under high to vary high level of eutrophication as evidenced from the existence of dense macrophytic stands. The plankton population in particular has suffered the most both in terms of quality and quantity. So far, no study was conducted in the dynamic aspects of plankton production in the Borobila beel. Therefore, it is of paramount importance to study the qualitative and quantitative aspects of unravel plankton population and its interaction with various physico-chemical parameters of the Borobila beel. Thus, the present study was conducted to determine the status of plankton population of Borobila beel both qualitatively and quantitatively in relation to the physico-chemical characteristics of the beel. Borobila beel is located in Rangpur district in northern Bangladesh. It is a semi-closed beel connected with other beels. The approximate water area during rainy season is 700 ha and that during dry season is 50 ha. Water depth varies from 1.8 meter to 3.4 meter.

Results/Conclusions

Altogether 51 genera of plankton were recorded from the beels of which 40 genera representing phytoplankton while zooplankton represented 11 genera. Maximum forty genera of phytoplankton belonged to Chlorophyceae (18), Cyanophyceae (10), Bacillariophyceae (8), Euglenophyceae (3) and Dinophyceae (1) were recorded from Borobila beel while zooplankton belonged to Crustacea (6) and Rotifera (5). Beel showed considerably higher phytoplankton diversity than its zooplankton diversity. Plankton biodiversity represented strong correlation (P<0.01) with phytoplankton where r values was 0.938 in Borobila beel. Quantitative abundance of plankton were found to fluctuates from 983 to 3500 cells/l in Borobila beel. Significants negative correlation was noted in respect to total alkalinity (P<0.05) and pH (P<0.01) with quantitative abundance of phytoplankton population. Quantitative abundance of zooplankton population significant negative correlation (P<0.05) was observed with pH (r = -0.589) in Borobila beel. Plankton population was significantly correlated with different water quality parameters found in the beel although their levels of relationship varied from beel to beel.