Seasonal Variation in Zooplanktonic Community in Swamp of Purnia (Bihar), India

Abstract

Zooplankters occupy an intermediate position in food web and are good indicators of the changes in water quality, because they are strongly affected by environmental conditions and respond quickly to changes in water quality. Hence, qualitative and quantitative studies of zooplankton are of great importance. The present study was undertaken to quantify the seasonal variations of zooplankton and selected physico-chemical variables (temperature, pH, Secchi disc transparency, dissolved oxygen, free CO2, bicarbonate, chloride, nitrate, phosphate and silicate concentrations) in the swamp of Purnia for one annual cycle (March 2007 to February 2008). The zooplankton taxa collected from the swamp water belong to three dominant groups viz. rotifers, cladocera and copepods. 26 zooplankton species were identified in which 17 belong to rotifer, 5 to cladocera and 4 to copepod. Rotifers were the most dominant group showing highest percentage (47.38%) composition and diversity followed by cladocera (39.64%) and copepod (12.98%). The zooplankton density in different seasons was in order of summer> winter > monsoon. The diversity of the overall zooplankton shows high in summer winter (H'= 0.964), summer (H'= 0.821) and less in monsoon (H'= 0.789). Density, diversity and composition of zooplankton also exhibited monthly variations. Brachionus, Keratella, Filiina, Cyclops and Diaptomus indicated organic pollution in the swamp. Zooplankters showed negative correlation with pH and DO2 in summer season as well as with free CO2, nitrate and phosphate during monsoon and winter. Further zooplankters exhibited negative correlation with water temperature and pH in monsoon and winter seasons respectively. The study established possible influences of the change in water quality to zooplankton population.