Effects of ontogenetic vertical migration of zooplankton on annual primary production – using NEMURO embedded in a general circulation model

Authors

  • Maki N. Aita,

    Corresponding author
    1. Global Warming Research Program, Frontier Research System for Global Change, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, Kanagawa, 236-0001, Japan
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  • Yasuhiro Yamanaka,

    1. Global Warming Research Program, Frontier Research System for Global Change, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, Kanagawa, 236-0001, Japan
    2. Graduate School of Environmental Earth Science, Hokkaido University, N10W5, Kita-ku, Sapporo, Hokkaido, 060-0810, Japan
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  • Michio J. Kishi

    1. Global Warming Research Program, Frontier Research System for Global Change, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, Kanagawa, 236-0001, Japan
    2. Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1, Minato-cho, Hakodate, Hokkaido, 041-8611, Japan
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*e-mail: macky@jamstec.go.jp

Abstract

We developed a global three-dimensional physical–biological coupled model and applied it in simulations with and without ontogenetic seasonal vertical migration of large zooplankton (copepods). The annual cycle of phytoplankton behaviour is well reproduced by this model with the seasonal vertical migration of zooplankton. A comparison of the two cases shows that in the northwestern Pacific and subarctic southern ocean, primary production is higher in the case with vertical migration. In these regions, large phytoplankton (diatoms) dominate, and the presence of large zooplankton throughout the year reduces primary production by large phytoplankton (diatoms). This effect is greatest for the diatom bloom. On the other hand, for regions where small phytoplankton dominate, primary production is higher in the case without vertical migration. This is because small zooplankton are suppressed by grazing pressure from large zooplankton, reducing grazing pressure on small phytoplankton.

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