Changes of biochemical and lipid composition of phytoplankton (Prorocentrum minimum) in environmental factor; effects of light intensity and temperature

Abstract

Effects of light intensity and temperature on the biochemical composition of Prorocentrum minimum, a dinoflagellate causing red tide, were examined. Cultures were grown under 14:10 h light:dark (L:D) regime at three light intensity ranging from 1,000 to 9,000 Lux and three temperatures ranging from 15 to 30℃. Cells were harvested at late-logarithmic phase for analysis of biochemical composition. In the results from light intensity effect experiment, growth pattern was not differ over the 2,000 Lux. The highest levels of carbohydrate, protein and lipid were present in cells from cultures grown at 7,000-9,000 Lux, 2,000-3,000 Lux and 1,000-1,300 Lux, respectively. The protein/carbohydrate ratio and MGDG/DGDG ratio was highest in cells from culture grown at 2,000-3,000 Lux. The activity of photosystem II of the culture grown 7,000-9,000 Lux was lower than others. Therefore the cells grown 2,000-3,000 Lux represented highest cellular activity and photosynthetic activity. In the results from temperature effect experiment, growth pattern of cells grown at 25℃ was not differ from the cells grown at 30℃. The levels of protein, carbohydrate and lipid were increased as temperature was declined. In contrast to the cultures grown at 25 and 30℃, the MGDG/DGDG ratio and activity of photosystem II were significantly decreased in the cultures grown at 15℃. The levels of phosphatidylserine and phosphatidic acid were very high in the culture grown at 15℃. Therefore we suggest that optimal temperature for the growth of P. minium is 25℃ and low temperature (15℃) affected the cellular activity and photosynthesis of the cells.