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Community composition and photophysiology of phytoplankton assemblages in coastal Oyashio waters of the western North Pacific during early spring

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Title: Community composition and photophysiology of phytoplankton assemblages in coastal Oyashio waters of the western North Pacific during early spring
Authors: Yoshida, Kazuhiro Browse this author
Endo, Hisashi Browse this author
Lawrenz, Evelyn Browse this author
Isada, Tomonori Browse this author →KAKEN DB
Hooker, Stanford B. Browse this author
Prasil, Ondrej Browse this author
Suzuki, Koji Browse this author →KAKEN DB
Keywords: Coastal Oyashio
Spring diatom bloom
P-E curve
Diatom-specific rbcL
Chlorophyll a fluorescence
Issue Date: 15-Nov-2018
Publisher: Elsevier
Journal Title: Estuarine Coastal and Shelf Science
Volume: 212
Start Page: 80
End Page: 94
Publisher DOI: 10.1016/j.ecss.2018.06.018
Abstract: Globally, the western subarctic Pacific is known as the region with the largest seasonal drawdown in the partial pressure of CO2 due to biological activity, i.e., high spring primary production and particulate organic carbon flux. These distinctive features are mainly caused by intense spring diatom blooms in coastal Oyashio (COY) and Oyashio (OY) waters. Although phytoplankton assemblages in OY waters are rather well studied, little is known about COY waters. In this study, photophysiological properties and phytoplankton community composition in COY waters were investigated during the pre-bloom and bloom periods from March to April 2015. Next-generation sequencing targeting the 18S rRNA gene revealed that the diatom Thalassiosira generally dominated the phytoplankton community and showed distinct differences in the diatom communities in shelf and offshore waters of the COY. Additionally, the relative contribution of Thalassiosira to the total diatom assemblages showed a positive correlation with maximum photosynthetic rates (P-max(B)) occurring throughout this study. Chlorophyll a concentration and primary productivity were also positively correlated with sea surface temperature, suggesting that temperature was a critical factor for bloom development. Short-term on-deck incubation experiments were carried out to examine the role of temperature in determining planktonic photosynthetic processes. Our results showed an increase in P-max(B) with rising temperature in assemblages from the shelf COY waters. Similarly, transcription levels of the diatom-specific rbcL gene, which encodes the large subunit of RuBisCO, also increased with rising temperature in the shelf assemblages. In contrast, temperature had little effect on the maximum photochemical quantum efficiency (F-v/F-m) of photosystem II. The results suggested that the transcription activity of the diatom-specific rbcL gene was upregulated by the increase in temperature, and that led to the higher P-max(B) values and the spring diatom bloom in the shelf COY region.
Rights: ©2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
https://creativecommons.org/licenses/by-nc-sa/4.0/
Type: article (author version)
URI: http://hdl.handle.net/2115/79655
Appears in Collections:環境科学院・地球環境科学研究院 (Graduate School of Environmental Science / Faculty of Environmental Earth Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 鈴木 光次

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