Uptake and utilization characteristics of Prorocentrum donghaiense, Phaeoecystis globosa, Karenia mikimotoi and Skeletonema costatum for dissolved free amino acids
海洋微藻对游离氨基酸的利用特性研究

The growth dynamics, photosynthetic characteristics and uptake kinetics of three harmful algae, Prorocentrum donghaiense, Phaeoecystis globosa, Karenia mikimotoi and a common phytoplankton species Skeletonema costatum were studied in the laboratory. The four algae were isolated or collected from the coastal waters of China, with alanine, glycine, glutamate and aspartate used as its sole nitrogen source, respectively. Dissolved inorganic nitrogen nitrate and ammonium were used as controls. The results showed that P. donghaiense and P. globosa were able to utilize multiple free amino acids, while K. mikimotoi and S.costatum could not grow with amino acids as the sole nitrogen sources under axenic conditions. The specific growth rates of P. donghaiense and P. globosa were the highest when alanine acted as the sole nitrogen source, followed by glutamate, aspartate and glycine. Fv/Fm values of amino acid treatments declined slightly and slowly in the later growth stage, but still higher than inorganic nitrogen treatments. The maximum uptake rates of P. donghaiense and P. globosa for alanine were 3.32 and 0.41 pmol·cell-1·h-1,respectively, and the half saturation constants were 6.99 and 20.54 pmol·L-1, respectively. Consequently, the capability of uptake and utilization for DFAAs were significantly different among marine microalgae. In the coastal waters with increasing organic pollution, some harmful phytoplankton species equipped with broader nitrogen niche, such as P. donghaiense and P. globosa may enhance their competition potential, and even form red tides under suitable environmental conditions.