Lake Qarun is an inland closed saline basin, used as a reservoir for agriculture drainage water. The Zooplankton-Phytoplankton interface was studied through 3 in situ experiments. The major conclusion that can be drawn from this study is that zooplankton play a major role in regulation of phytoplankton biomass in lake Qarun during Summer. The grazing pressure of zooplankton was mainly on the nano & pico phytoplanktonic fraction. Brachionus plicatilis was reported to feed
exclusively on Nitzschia sigma and N. frustulum var. perpnsilla.