Abstract
Changes in some chemical components of Alexandrium catenella (Whedon et Kofoid) Balech and Scrippsiella trochoidea (Stein) Loeblich III (Dinophyceae) during their growth cycles were examined. Results clearly showed that the cellular content of carbon and nitrogen gradually increased during lag and early exponential phases of growth. Thereafter, they decreased and became nearly constant from mid exponential phase to the end of the experiment. Changes in cellular phosphorus and cellular ATP content of these dinoflagellates showed the same general patterns as those of carbon and nitrogen. It was observed that after cellular content of ATP remarkably increased and reached a maximum level, cell number increased rapidly. Glutamic acid, glycine, and alanine were the predominant components of amino acids in both dinoflagellates. The mean values of nitrogen content in total amino acids in A. catenella and S. trochoidea throughout the growth cycle were higher than 40 and 60% of total cellular nitrogen, respectively. Since the changes in pattern of cellular amino acid content followed the same pattern as that of cellular nitrogen, it could be concluded that cells accumulated nitrogen compounds mainly in the form of amino acids. Relative abundance of arginine in S. trochoidea was nearly stable throughout the growth cycle, whereas, the relative abundance of arginine in A. catenella dramatically increased from the beginning of the stationary phase to the end of the experimment. It could be suggested that changes in cellular amino acid composition played an important role in the growth processes of this marine dinoflagellate.
