GROWTH OF SKELETONEMA COSTATUM CLEVE UNDER DIFFERENT LIGHT REGIMES

Light impact on growth of Skeletonema costatum at 20 treatments of light regimes including combination bf five intensities of 2000, 4000, 6000, 8000 and 10000 lux and four periods of (LightDark) 24:0, 18:6, 12:12 and 6:18 hours was studied. Daily random sampling was done for all treatments to determine cell concentration and growth rate. Among different light periods, growth rate was maximum and cell concentration was minimum at continuous light. At 4000 lux growth rate was higher than other intensities. However, there were not significant differences between treatments for growth, except 6:18 h (L:D); in this light period at different irradiances, growth rate and cell concentration was very low, and this made a significant difference between these treatments and others. The results showed that S. castatum's active cells adapted to light changes very well. But in older cells, i. e. the cells at late stationary phase or at death phase, there might be some growth disorders caused by environmental parameters, before active growth begin.