# Phytoplankton competition during the spring bloom in four Plankton Functional Type Models

Author(s) Hashioka, T., Vogt, M., Yamanaka, Y., Quéré, C. le, Noguchi Aita, M., Alvain, S., Bopp, L., Hirata, T., Lima, I., Sailley, S., Doney, S. C.
Publication Type Journal Items, Publication Status: Published
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Title Phytoplankton competition during the spring bloom in four Plankton Functional Type Models
Author(s) Hashioka, T.
Vogt, M.
Yamanaka, Y.
Quéré, C. le
Noguchi Aita, M.
Alvain, S.
Bopp, L.
Hirata, T.
Lima, I.
Sailley, S.
Doney, S. C.
Journal or Series Title Biogeosciences discussions
Volume Number 9
Issue Number 12
Start Page 18083
End Page 18129
ISSN 1726-4170
1726-4189
Publisher Copernicus
Publication Date 2012-12
Abstract We investigated the mechanisms of phytoplankton competition during the spring bloom, one of the most dramatic seasonal events in lower-trophic level ecosystems, in four state-of-the-art Plankton Functional Type (PFTs) models: PISCES, NEMURO, PlankTOM5 and CCSM-BEC. In particular, we investigated the relative importance of different ecophysiological processes on the determination of the community structure, focusing both on the bottom-up and the top-down controls. The models reasonably reproduced the observed global distribution and seasonal variation of phytoplankton biomass. The fraction of diatoms with respect to the total phytoplankton biomass increases with the magnitude of the spring bloom in all models. However, the governing mechanisms differ between models, despite the fact that current PFT models represent ecophysiological processes using the same types of parameterizations. The increasing trend in the percentage of diatoms with increasing bloom magnitude is mainly caused by a stronger nutrient dependence of photosynthesis for diatoms compared to nanophytoplankton (bottom-up control). The difference in the maximum photosynthesis rate plays an important role in NEMURO and PlankTOM5 and determines the absolute values of the percentage of diatoms during the bloom. In CCSM-BEC, the light dependency of photosynthesis plays an important role in the North Atlantic and the Southern Ocean. The grazing pressure by zooplankton (top-down control), however, strongly contributes to the dominance of diatoms in PISCES and CCSM-BEC. The regional differences in the percentage of diatoms in PlankTOM5 are mainly determined by top-down control. These differences in the mechanisms suggest that the response of marine ecosystems to climate change could significantly differ among models, even if the present-day ecosystem is reproduced to a similar degree of confidence. For further understanding of plankton competition and for the prediction of future change in marine ecosystems, it is important to understand the relative differences in each physiological rate and life history rate in the bottom-up and the top-down controls between PFTs.
DOI 10.5194/bgd-9-18083-2012
Document Type Article
Publication Status Published
Language English
Assigned Organisational Unit(s) 03731
Organisational Unit(s)
NEBIS System Number 006289717
Source Database ID FORM-1357827625
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@article{Hshk2012,
author = "Hashioka, T. and Vogt, M. and Yamanaka, Y. and Qu{\'{e}}r{\'{e}}, C. le and Noguchi Aita, M. and Alvain, S. and Bopp, L. and Hirata, T. and Lima, I. and Sailley, S. and Doney, S. C.",
title = "{P}hytoplankton competition during the spring bloom in four {P}lankton {F}unctional {T}ype {M}odels",
journal = "Biogeosciences discussions",
year = 2012,
volume = "9",
number = "12",
pages = "18083--18129",
month = dec,
}


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