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Light utilization efficiency of phytoplankton in the Western Subarctic Gyre of the North Pacific during summer |
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| Authors: | Yuichi Nosaka Tomonori Isada Isao Kudo Hiroaki Saito Hiroshi Hattori Atsushi Tsuda Koji Suzuki |
| Affiliation: | 1. Graduate School of Environmental Science, Hokkaido University, North 10 West 5, Kita-ku, Sapporo, Hokkaido, 060-0810, Japan 2. Field Science Center for Northern Biosphere, Hokkaido University, Aikappu 1, Akkeshi, Hokkaido, 088-1113, Japan 3. Graduate School of Fisheries Sciences, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan 4. Tohoku National Fisheries Research Institute, Shinhama-cho 3-27-5, Shiogama, Miyagi, 985-0001, Japan 5. School of Biological Sciences, Tokai University, Minamisawa 5-1-1-1, Minami-ku, Sapporo, Hokkaido, 005-8601, Japan 6. Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwanoha, Kashiwa, Chiba, 277-8564, Japan 7. Faculty of Environmental Earth Science, Hokkaido University, North 10 West 5, Kita-ku, Sapporo, Hokkaido, 060-0810, Japan 8. CREST, Japan Science and Technology Agency, North 10 West 5, Kita-ku, Sapporo, Hokkaido, 060-0810, Japan |
| Abstract: | We investigated the water-column light utilization efficiency (Ψ) of phytoplankton photosynthesis in the Western Subarctic Gyre (WSG) of the North Pacific during summer 2008. The Ψ values (0.64–1.86 g C [g Chl a]?1 [mol photon]?1 m2) obtained were observed to increase significantly with decreasing daily photosynthetic available radiation (PAR) and were generally higher than those of previous studies, not only from the subarctic Pacific but also from the world’s oceans. To examine the effect of iron availability on Ψ in the WSG, Ψ values were estimated from the data of two in situ iron fertilization experiments: the Subarctic Pacific Iron Experiment for Ecosystem Dynamics Study I (SEEDS-I) and II (SEEDS-II). We found that iron availability did not affect Ψ values. Overall, this study revealed that Ψ values changed remarkably in the WSG during the summer, and that higher values were found at the stations where moderate PAR levels (ca. 10–30 mol photons m?2 day?1) were observed and where autotrophic flagellates predominated in the phytoplankton assemblages. |
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