EFFECT OF VITAMIN CONCENTRATIONS ON GROWTH AND DEVELOPMENT OF VITAMIN‐REQUIRING ALGAE 1

SUMMARY Vitamin‐requiring marine algae , Cyclotella nana, Monochrysis lutheri, and Amphidinium carterae, were grown in batch culture with limiting concentrations of vitamin B 12 , thiamine, and biotin, respectively. Cell numbers, average cell volumes, biomasses, 11 CO 2 uptake rates, and chlorophyll a contents were determined daily. Maximum 14 CO 2 uptake rates in most vitamin concentrations were obtained at 2 days with C. nana and M. lutheri and at 4 days with A. carterae after starved cultures were exposed to the vitamin. Radiocarbon uptake rates approximately reflect biomass increases. Cell numbers were proportional to vitamin concentrations when cells were incubated for 2 to 3 more days. Cell sizes varied depending on time of incubation. Chlorophyll a content did not always reflect vitamin concentrations. Maximum carbon assimilation rates (K m ) and saturation constants (K s ) determined from 14 CO 2 , uptake rates in different vitamin concentrations during early incubation were higher than when determined from cell number in log phase growth. Dissolved vitamin B 12 , thiamine, and biotin in many samples of seawaters were in the ranges which influence the growth rate, cell size, and chlorophyll a content of C. nana, M. lutheri, and A. carterae, respectively, in laboratory studies. The effects of vitamins on these algae in situ may be similar .