Study of the effects of environmental factors on the biochemical compositions of four species of marine single-celled algae

Photosynthetic rates(PR) of four species of marine single-celled algae were determined by means of ¹⁴C-tracer method under the experimental modeling conditions. The effects of environmental factors, such as light, temperature and nutrients, on the biochemical compositions of the algae were studied. The results indicate that the suitable light intensities for the growth of Phaeodactylum tricornutum, Dunaliella spp.,Skeletonema costatum and Isochrysis galbana are in the range 5.8×10³ to 15×10³lx, showing an increasing trend of PR with the heightened light intensities. The irradiance response of Dunaliella spp. and Isochrysis galbana is significant. The contents of carbohydrate increase, but those of protein decrease, otherwise, the contents of lipids changed little. The optimum temperatures for the growth of the four species of algae are 14, 26, 21 and 26℃ respectively, characterized by the maxima of PR and the contents of carbohydrate, protein and lipids as well as their variations. The apparent activation energies in the photosynthesis process of Phaeodactylum tricornutum, Dunaliella spp.,Skeletonema costatum and Isochrysis galbana are 23.2, 38.5, 22.4 and 61.7 kj/mol respectively, and the temperature coefficients for the four algae are 1.74, 1.74, 1.38 and 1.69 respectively. The peaks of PR appeared in some culture media(N/P=16) of Phaeodactylum tricornutum and Skeletonema costatum,while in other media(N/P=28) of Dunaliella spp. and Isochrysis galbana.The contents and their variations of carbohydrate, protein and lipids of the four species of algae are all maximum when N/P is equal to 16 in culture media.