Document Type : Primary Research paper
Assistant Professor, Department of Zoology Laboratory, St. Joseph’s College, North Point, Darjeeling, Affiliated to University of North Bengal, West Bengal, India
The present contribution explores the usefulness of zooplankton as a tool for assessing the water quality and trophic status of a fresh water lake Saheb Bandh, situated between 23º29'42"N latitude and 86º21'37"E longitude of Purulia district, West Bengal, India. The lake water was sampled monthly and investigated for water limnology and zooplankton community structure using statistical measurement of diversity indices to characterize the zooplankton fauna for a period of one year (March 2014 to February 2015). Regarding zooplankton species composition, a total of 32 species belonging to 22 genera were recorded, out of which Rotifera was represented by 15 species, Cladocera by 10 species, Copepoda by 6 species and Ostracoda by 1 species. Rotifera was the predominant group (44.38%), followed by Cladocera (35.34%), Copepoda (19.37%) and Ostracoda (0.9%) in the following order of dominance: Rotifera > Copepoda > Cladocera > Ostracoda. There were strong correlations between the lake’s limnological parameters and its zooplankton communities. From limnological analysis, it is evident that variables like lake surface temperature and dissolved oxygen are the most important factors influencing the seasonal pattern of zooplankton population. Alkaline pH and nutrients were the main environmental factors which affected zooplankton abundance in the lake. Monthly and seasonal variation of zooplankton species in respect of dominance, diversity, evenness and richness were calculated. Presence of certain species was considered to be a biological indicator for water quality status and trophic condition of the lake. Q Brachionus/Trichocerca (QB/T) index was used for the determination of trophic level of the lake and the lake is eutrophic. Overall, results showed that limnological parameters and zooplankton assemblages’ have considerable effects on the water quality and trophic condition that can potentially affect the functioning of this ecosystem.