1996 Fiscal Year Final Research Report Summary
Physiological ecology of marine planktonic prochlorophytes
| Project/Area Number |
07836007
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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 | 時限 |
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| Research Field |
海洋生物学
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| Research Institution | The University of Tokyo (1996)
Mie University (1995) |
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Principal Investigator |
FURUYA Ken The University of Tokyo, Graduate School of Agricultural and Life Sciences, Associate Professor, 大学院・農学生命科学研究科, 助教授 (30143548)
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| Co-Investigator(Kenkyū-buntansha) |
ISHIKAWA Akira Mie University, Faculty of Bioresources, Research Associate, 生物資源学部, 助手 (00273350)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Prochlorphyte / picophytoplankton / phytoplankton / divinylchlorophyll a / Kuroshio / Subsurface chlorophyll maximum / 亜表層クロロフィル極大 |
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| Research Abstract |
The present study investigated spatial distribution of marine planktonic prochlorophytes in the Kuroshio and adjacent area and determined their growth dependence on light environments. Prochlorophytes occurred in Kuroshio and adjacent subtropical waters ubiquitously. They were found at temperature or 18 to 28ﾟC with maximum occurrence at 21ﾟC.their vertical distribution showed subsurface maximum around 10% illumination of the surface at the initial phase of stratification of the water column, and around 1% depth in summer, where the deep maxima of chlorophyll a developed. Ratio of divinylchlorophyll a (chl a2), a marker pigment of prochlorophytes to chlorophyll b increased along with depth indicating pigment adaptation to blue light fields of low intensity. Prochlorophytes were important primary producers in terms of standing stock : chl a2 occupied 29% of fluorometrically determined chlorophyll a on the average. In contrast, prochlorophytes were minor constituents in neritic and coastal phytoplankton communities and they were not found in Oyashio water, subarctic water. Based on comparison of distributions of chl a2 and numerical abundance of <1mum particles that emitted red fluorescence under blue light excitation, many particles other than prochlorophytes were detected on the shelf of the East China Sea. Pigment signature suggested these were likely either chlorophytes or prasinophytes.
Culture experiment revealed variations in light-dependency of growth among three strains used with optimal photon flux ranging from 53 to 283mumol m^<-2>s^<-1> and maximum specific growth rates of 0.26 to 0.66 d^1 at 14L : 10D photoperiod. Cellular chl a2 content and relative chlorophyll b contents increased with decrease in growth light intensity. Minimum light intensity for their growth was below 4mumol m^<-2>s^<-1>. These findings agreed well with the results obtained in the field survey.
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