Secondary Productivity of Zooplanktons in Lotic Water of River Saryu and Ganga at Saran District, Bihar, India

The role of Zooplankton in the aquatic food chain is very important as is it a member of trophic level two because it is secondary producer as well as primary consumer. The productivity of zooplankton will reflect the status of the aquatic ecosystem. Scanty reports are available on the secondary productivity of river Ganga. The present study was conducted in stretch of river Saryu and Ganga in Saran district, Bihar that was unexplored earlier. Secondary productivity of zooplankton was estimated following method suggested by Dalai & Parulekar (1986) based on displacement volume and Mangas and Garcia (1991). Zooplankton secondary productivity was in higher range 70.12-227.89 µg during winter followed by summer and monsoon in both the rivers. Zooplankton group wise individual biomass was as follows: (cladocerans > copepods > rotifers). However average biomass indicated that rotifers were dominating zoo plankton in the biomass contribution causing secondary production of zooplankton. The study identifies secondary productivity as a more integrative tool for the assessment of the ecosystem function.