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 = PBmax/αB). 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
Full text in pdf format | 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. https://doi.org/10.3354/meps08329
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