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Marine Ecology Progress Series

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MEPS 399:39-52 (2010)  -  DOI:

Temporal and spatial variations in photosynthetic physiology of diatoms during the spring bloom in the western subarctic Pacific

Naoki Yoshie1,2,3,*, Koji Suzuki4, Akira Kuwata2, Jun Nishioka5, Hiroaki Saito2

1Division of Coastal Oceanography, Center for Marine Environmental Studies, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577, Japan
2Tohoku National Fisheries Research Institute, Fisheries Research Agency, 3-27-5 Shinhama-cho, Shiogama 985-0001, Japan
3Japan Society for the Promotion of Science, 6 Ichibancho, Chiyoda-ku, Tokyo 102-8471, Japan
4Faculty of Environmental Earth Science, Hokkaido University, N10W5 Kita-Ku, Sapporo 060-0810, Japan
5Institute of Low Temperature Science, Hokkaido University, N19W8 Kita-Ku, Sapporo 060-0819, Japan

ABSTRACT: Variations in photosynthetic parameters of phytoplankton during the spring bloom were investigated in the western subarctic Pacific. Light-saturated maximum photosynthesis rate (PBmax) and light-limited slope (αB) in the photosynthesis-irradiance (P-E) curve were almost constant in the first half of the bloom and then concurrently increased by 5 times in the latter half with a constant light-saturation index (Ek = PBmaxB). In contrast, the maximum photochemical quantum efficiency (Fv/Fm) of the algal photosystem II increased in the first half and thereafter decreased. Water temperature significantly affected the covariation in PBmax and αB (i.e. Ek-independent variability), suggesting that dark reaction processes in photosynthesis mainly regulated the changes in the P-E parameters. Although influences of nitrate, silicic acid, and dissolved iron on the P-E parameters were not observed, the elevated ammonium levels found in the latter half of the bloom could contribute to the Ek-independent variability. There was no significant relationship among algal net growth rate, PBmax, and αB throughout the observations. Since most ecosystem models have used a constant αB, parallel changes in PBmax and αB should be taken into account in models reproducing ecosystem dynamics during spring diatom blooms.

KEY WORDS: Iron · P-E curve · Photosynthesis · Spring bloom · Western North Pacific

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Cite this article as: Yoshie N, Suzuki K, Kuwata A, Nishioka J, Saito H (2010) Temporal and spatial variations in photosynthetic physiology of diatoms during the spring bloom in the western subarctic Pacific. Mar Ecol Prog Ser 399:39-52.

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