2006 Fiscal Year Final Research Report Summary
LIGHT ABSORPTION CHARACTERISTICS OF PHYTOPLANKTON : DEPENDENCY OF LIGHT INTENSITY, DIEL CYCLE, AND UNTRIENT LIMITATION
| Project/Area Number |
16580161
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General fisheries
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| Research Institution | SOKA UNIVERSITY |
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Principal Investigator |
TAGUCHI SATORU SOKA UNIVERSITY, FACULTY OF ENGINEERING, PROFESSOR, 工学部, 教授 (40277877)
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| Co-Investigator(Kenkyū-buntansha) |
OHI NOBUAKI (moved to Texas A & M University in April 2005) SOKA UNIVERSITY, FACULTY OF ENGINEERING, ASSISTANT PROFESSOR (70367192)
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| Project Period (FY) |
2004 – 2006
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| Keywords | LIGHT ABSORPTION / CHLOROPHYLL a SPECIFIC ABSORPTION COEFFICIENT / CHLOROPHYLL a / DIEL CYCLE / DAY LENGTH / N : P SUPPLY RATIO |
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| Research Abstract |
Global marine primary production has been estimated using the algorithm from the concentration of surface chlorophyll a of the oceans detected from the satellites. In this algorithm, one of the critical parameters is the chlorophyll a specific absorption coefficient a* and considered as a constant throughout the oceans. However a* has been known to be variable. As long as only the average of a* is considered, not only the accuracy of our estimations but also our understanding of changing global environment can not be improved at all. Both solar light intensity and day length vary with time and latitude, and also surface nutrient concentrations in the oceans vary with time and place. In the present project we have investigated how those three factors affect on a* using a chemostat culture system with a model species of Isochrysis galbana and a semi-continuous culture system with harmful algal species Alexandrium tamarense.
Our conclusions are followed;(1)a* decreases with light intensity and a phase of diel cycle in a* shifts by 12 hours at maximum with light intensity, (2) a* decreases with a length of day time, and (3) a* may be controlled by nitrate: phosphate ratio (N:P ratio) but their trends are depending on species, i.e., a* increases with decreasing N:P ratio for isochrysis galbana while a* dose not respond to a change of N:P ratio for Alexandrium tamarense. Once those relationships are formulated into the algorithms, the accuracy of our estimation in global marine primary production and our understanding of changing global environments can be much improved.
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