Study on the Physiological Responsws of a Nexious Phytoplankton to the Enviromental Changes using Unsteady-state Continuous Culture Method.

1993 Fiscal Year Final Research Report Summary

• Project/Area Number: 04806025
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: General fisheries
• Research Institution: HIROSHIMA UNIVERSITY
• Principal Investigator: YAMAMOTO Tamiji Hiroshima University Faculty of Applied Biological Science Assistant Professor, 生物生産学部, 講師 (40240105)
• Co-Investigator(Kenkyū-buntansha): MATSUDA Osamu Hiroshima University Faculty of Applied Biological Science Professor, 生物生産学部, 教授 (60034469)
• Project Period (FY): 1992 – 1993
• Keywords: Alexand rium / Continuous culture / Phosphorus / Mikawa Bay / Semi-contimuous culture

Research Abstract

Achievement of continuous culture of Alexandrium tamarense was unsuccessful due to the inherent property attaching to the wall of the clture vessel in the mixing water. Therefore, we ompoloyed both batch culture and semi-continuous culture methods insterad. The experimental results obtained in this study were as follows. (1) Optimum temperature and salinity for the growth were 15 ﾟC and 32-35%. (2) Maximum specific growth rate was 0.26d^<-1> using screw-capped test tube, and 0.48d^<-1> using 1l flusk, shich obviously showed the wall effect of the vessel. (3) the threshols light intensity for the growth was 30muE m^<-2> s^<-1> , which means A.tamatense could never grow below the light level. (4) Light-and-dark experiment revealed that A.tamarense takes up phosphate in the light period and grow in the dark period. (5) Minimum phosphorus cell quota of A.tamarense was 0.56pmol cell^<-1> . (6) Miaximum specific uptake rate and half saturation constant for phosphate were 1.59h^<-1> and 1.85muM.(7) Similar experiments were carried out for a diatom Skeletonema costatum. The comparison of phosphate uptake kinetic parameters and growth parameters between them suggested that A.tamarense could not prevail over S.costatum in natural environment, hence disappearance of coexisting in the water column by some other reasons would be necessary gor propagation of A.tamarensw.