This trend has been widely reported in many phytoplankton species. The optimum requirement of light different in the range between 2500 and 6000 Lux for different diatom species viz, S. costatum, Asterionella socialis and Navicula (Hoff and Snell, 1989). Small portions of cellular carbon lost to the medium during dark periods following period of photo assimilation (Hellebust, 1974). Nutrition is essential component for phytoplankton and its groups. The growth depends on the availability of certain nutrients like nitrogen phosphorus and silicon. These nutrients were found to limit the reproduction in the marine phytoplankton