Study on the primary production in the Vembanad lake

Abstract

This paper forms part of a study on the phytoplankton standing crop, primary production and related properties in the Vembanad Lake and connected backwaters extending from -Aleppey in the south to Azhicode in the north. A total area of 300 sq. km. has been covered by 28 stations for hydrographic properties and 7 stations for primary and secondary production. In the composition of phytoplankton, spatial heterogeneity is observed with fresh water, estuarine and marine forms distributed at different regions. The standing crop does not always reflect the photosynthetic production which has regional and spatial variation In the magnitude. The annual grass production ranger from about (150 to 650 gClm2)d.y maximum during pre and post-monsoon period unlike in the adjacent marine environment. Total organic production in the Vembanad Lake has been estimated as 10.00,000 tonne of carbon. The quantum of respiration by zooplankton and the surplus quantity left for alternate pathways in the food chain have been indicated.