mortality rate changes proportional to the standing stock of living cells. Fig. 2 reflects this dependence. If initial and final standing stocks of phytoplankton are equal, all additional production must be grazed Therefore, they zooplankton benefits by feeding strictly periodically and near nightfall(especially if feeding takes place during a few night hours(c) If phytoplankton grazing is uniform during the whole day, phytoplankton production can be calculated from Eq. (16), where Q, is uniform grazing determined from Eq. (14) if BT=B0 grazing rate is proportional to the initial standing stock