Influence of non-photosynthetic pigments on light absorption and quantum yield of photosynthesis in the western equatorial Pacific and the Subarctic North Pacific |
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| Authors: | Anil Kumar Vijayan Takashi Yoshikawa Shigeki Watanabe Hiroaki Sasaki Kazuhiko Matsumoto Sei-Ichi Saito Shigenobu Takeda Ken Furuya |
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| Institution: | 1.Graduate School of Agricultural and Life Sciences,The University of Tokyo,Bunkyo-ku, Tokyo,Japan;2.School of Marine Science and Technology,Tokai University,Orido, Shimizu-ku, Shizuoka,Japan;3.Fisheries Research Agency,Seikai National Fisheries Research Institute,Taira-machi, Nagasaki-shi, Nagasaki,Japan;4.Japan Agency for Marine-Earth Science and Technology Center (JAMSTEC),Mutsu Institute for Oceanography (MIO),Sekine, Mutsu, Aomori,Japan;5.Graduate School of Fisheries Sciences,Hokkaido University,Hakodate,Japan |
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| Abstract: | Regional variations in the contribution of non-photosynthetic pigments (ā
np*) to the total light absorption of phytoplankton (ā
ph*) and its influence on the maximum quantum yield of photosynthesis (φ
m) were investigated. In the western equatorial Pacific, the surface ā
np* : ā
ph* ratio was higher in the western warm pool than that in the upwelling region. This difference appears to be attributable to
severe nitrate depletion and higher percentage of prokaryotes, which can accumulate very high concentrations of zeaxanthin
in the western warm pool. In the subarctic North Pacific, the ā
np* : ā
ph* ratio was expected to be higher in the Alaskan Gyre where the thermocline is sharper and iron limitation may possibly be
more severe than in the Western Subarctic Gyre. However, the ratio was actually higher in the Western Subarctic Gyre, contradictory
to our expectations. This east-west variation appears to be attributable to changes in the taxonomic composition; cyanobacteria
were more abundant in the Western Subarctic Gyre. The values of ā
np* : ā
ph* and its vertical variations were relatively small in the subarctic North Pacific compared to those in the western equatorial
Pacific. These inter-regional variations appear to be attributable to the lower solar radiation intensity, smaller percentage
of cyanobacteria, and relatively strong vertical mixing in the subarctic North Pacific. The spatial variations in ā
np* : ā
ph* significantly influence φ
m. In comparison with φ
m based on the total light absorption (φ
m ph), the values corrected for the contribution of non-photosynthetic pigments (φ
m ps) showed an increase in both the western equatorial Pacific and the subarctic North Pacific. |
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| Keywords: | Light absorption coefficient photosynthetic pigments non-photosynthetic pigments quantum yield of photosynthesis western Equatorial Pacific subarctic North Pacific |
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