SPATIO-TEMPORAL VARIATION OF SOME PHYSICO-CHEMICAL PARAMETERS AND ABUNDANCE OF PLANKTONIC COMMUNITY IN THE ATRAI RIVER, DINAJPUR, BANGLADESH

Abstract

The study was conducted to assess spatial and seasonal variations of some physico-chemical parameters and plankton community of the Atrai River in Dinajpur district for a period of one year from August 2017 to July 2018. The whole period was grouped into four seasons such as summer, autumn, winter and spring. Samples were collected monthly from three sampling sites named Vushi, Birga and Jhanjira assigned as site-1, site-2 and site-3, respectively. Some physico-chemical parameters namely, air and water temperature (°C), transparency (cm), depth (m), pH, dissolved oxygen (mg L-1 ) and alkanity (mgL-1 ) and plankton community were determined both at the field level and at the laboratory of the faculty of Fisheries, Hajee Mohammad Danesh Science and Technology University (HSTU), Dinajpur. The physicochemical parameters and plankton abundance did not vary significantly (P>0.05) among the sites but varied significantly (P<0.05) among seasons. However, all the physico-chemical parameters were within the acceptable limits for fishes, except transparency. The mean values of air temperature (°C)varied from 22.04±2.25 to 31.04±1.830C water temperature (°C)varied from 21.02± 2.29 to 30.24±1.990C and water transparency varied from 54.37± 9.98 to 67.74±13.58 cm. Water depth (m) was highest (6.66±1.34 m) in autumn andlowest (1.95± .17 m) in summer. The level of water of the river was influenced byseason. The pH value varied from 7.67±.53 to 9.42±.35 in autumn and winter, respectively. Dissolved oxygen concentration washighest (9.62±1.01 mg/L) in winter andlowest(8.69±.96 m/L) in autumn. The mean values of total alkalinity (mgL-1 ) varied from 29.18± 6.75 to 45.19± 2.90 mg/L in the present study. Total 28 phytoplankton genus identified of which 11 belongs to Chlorophyceae, 11 to Bacillariophyceae, 4 to Cyanophyceae and 2 to Euglenophyceae. Similarly, 9 genus of zooplankton were identified of which 3 belongs to Rotifera, 3 to Cladocera and 2 to Copepoda and 1 to Nauplius, the crustacea larvae. The number of genera and density of plankton showed sky-scraping seasonal variation during winter and summer. The overall density of plankton community were higher throughout the winter season.However, phytoplankton abundance was higher in winter and zooplankton in Autumn season. From this study, it can be concluded that physico-chemical parameters remain an acceptable range all the year but the plankton densities varies seasonally with higher in winter and lower in summer. This information could be helpful for further research work and fisheries management point of view.