e - poz 2 - Central Institute of Brackishwater Aquaculture

summer. The pure saline forms that were abundant at this sector during thesummer could not be recorded under the present condition. This obsewatiy is inconformity with the present study. Twenty four species of green algae, tenspecies of blue green algae, one species of yellow brown algae, 13 species .ofdesmids and 19 species of diatoms formed the phytoplankton population in thepresent investigation. But, during the prebamge only about 30 species ofphytoplankton was recorded from the same Sector by Joseph and Pillai (1975)within a salinity range of 0.2 to 33%. Moreover, the species present during themonsoon and post-monsoon period were qualitatively different from that of thepre-barrage phase. There was no perceptible change in the overall density ofplankton population in the sector during the post-barrage phase. The dominantspecies like Hormidium, Spirogyra, Microspora and Anacystis recorded during thepresent study were not reported from the studies conducted during the pre barragephase by Joseph and Pillai (1975).Table.6 Dominant forms of plankton in southern =tor of Vembanad lakebrfon and after the commissioning of thc Th.nccrmukkombmagrPie-barrdge phapostman^, 1971Salinity - 11-19.75 ppt(Nair, rt aL, 1975,joreph & Pillai, 1975)Post-barrage phaseP~monroon 1994-96