The results showed that the experimental set using initial density of × 104 cells/ml revealed the highest maximum density at × 104 cells/ml with growth rate of ; average cell size from 30-31 µm after 48 hours of culture. The differences were significant. | Trường Đại học Vinh Tạp chí khoa học, Tập 46, Số 4A (2017), tr. 11-20 EFFECTS OF INITIAL DENSITY AND pH ON THE GROWTH OF THALASSIOSIRA PSEUDONANA UNDER LABORATORY CONDITIONS Nguyen Van Cong (1), Tran Dinh Quang (2) Nguyen Kim Duong (2), Do Thi Hoa Vien (1) 1 Hanoi University of Science and Technology 2 Vinh University Received on 14/12/2017, accepted for publication on 15/3/2018 Abstract: The effects of initial density on the growth of Thalassiosira pseudonana were investigated in five different densities including × 104 cells/ml; × 104 cells/ml; × 104 cells/ml; × 104 cells/ml and × 104 cells/ml. The pH levels were also tested in nine different ranges which were divided into 2 groups namely wide pH range (pH = , , , ) and narrow pH range (pH = , , , , ). Each experiment was replicated 3 times resulting in a total of 42 experimental sets culturing in each 250 ml bottle individually. The results showed that the experimental set using initial density of × 104 cells/ml revealed the highest maximum density at × 104 cells/ml with growth rate of ; average cell size from 30-31 µm after 48 hours of culture. The differences were significant. Furthermore, we also found that those T. pseudonana cultured at pH ÷ showed higher growth rate and higher maximum density ( × 104 cells/ml and × 104 cells/ml, respectively) as well as shorter time of reaching the stationary phase compared to other pH levels of under and above . Noticeably, the optimal pH of led to the highest maximum density. The differences were significant. 1. Introduction Under artificial biomass conditions, Thalassiosira pseudonana shows a fast growth rate and the ability to adapt to environmental changes such as pH, light and temperature [2, 10]. Due to these advantages along with its small size, this microalgae becomes one of the preferred microalgae species used in marine fish breeding hatcheries (. feeding for .
