PHYSICO-CHEMICAL CONDITIONS AND PHYTOPLANKTON OF THE RIVER KIRTONKHOLA NEAR BARISAL CITY

PHYSICO-CHEMICAL CONDITIONS AND PHYTOPLANKTON OF THE RIVER KIRTONKHOLA NEAR BARISAL CITY

Phytoplankton diversity in relation to physico-chemical conditions of Kirtonkhola River near Barisal City has been studied from July 2005 to December, 2005 at three different spots. The City and the river is overwhelmingly important for its contribution to the socio-economy, inland transport, environmental maintenance of biodiversity in the southwestern part of Bangladesh. It comprises an area with a small habitat for many species of plankton and fauna coexist. The inland open water resources of the existing extent and magnitude should harbor and support population of a large varieties of aquatic species organisms. Important physical and chemical factors prevailing in the study area were determined viz, air temperature, water temperature, TDS, pH, EC, free CO2, DO, BOD5, carbonate, bicarbonate alkalinity, salinity, phosphate , chloride and silicate contents. Water temperature was always less than the surrounding air temperature and varied within 2˚C to 3˚C. The nature of water was alkaline and pH value varied from 5.5 to 7.6.Electric conductivity ranged from 186 to 281 ms, dissolve oxygen content varied 2.6 to 8.5 mg/l, transparency of water varied 15 to 17 cm, TDS varied from 93 to 141 gm/l, free CO2 from 0.5 to 5 mg/l, carbonate alkalinity was 164 to 200 mg/l, bicarbonate alkalinity varied 98 to 158 mg/l , BOD5 from 0.8 to 5.9 mg/l, total hardness varied from 14 to 20 mg /l, calcium hardness from 12 to 17 mg/l, magnesium hardness varied 1 to 4 mg/l salinity from 0.5 to 1 ppt, silicate varied from 13 to 19 mg/l and 0.4 to 0.6 mg/l, total phosphate were recorded. The phytoplankton abundance varied from 58404 to 109906 units /l. Attempts have been made wherever possible, to attribute the reasons for the changes of physico-chemical factors and their relationship with phytoplankton. Total 12 genera of phytoplankton under 4 classes (Cyanophyceae, Chlorophyceae, Bacillariophyceae and Euglenophyceae) were recorded. Melosira sp., Synedra sp. and Navicula sp. were the dominant genera in phytoplankton community. Among the three spots Bacillariophceae was the most dominant group and their percentage composition was 87.57 % in spot-1 and 82.64 % in spot-2 respectively and this group was also dominant in spot-3 and percentage composition was 74.87 %. The physico-chemical condition and phytoplankton data of the present study indicate the present river conditions specially the water quality of the Kirtonkhola river.