Yoshida, K and Endo, H and Lawrenz, E and Isada, T and Hooker, SB and Prasil, O and Suzuki, K, Community composition and photophysiology of phytoplankton assemblages in coastal Oyashio waters of the western North Pacific during early spring, Estuarine, Coastal and Shelf Science, 212 pp. 80-94. ISSN 0272-7714 (2018) [Refereed Article]
Copyright 2018 Elsevier Ltd.
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 (PBmax) 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 PBmax 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 (Fv/Fm) 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 PBmax values and the spring diatom bloom in the shelf COY region.
|Item Type:||Refereed Article|
|Keywords:||spring diatom bloom, chlorophyll a fluorescence, gene expression, next generation sequencing|
|Research Division:||Earth Sciences|
|Research Field:||Biological Oceanography|
|Objective Group:||Flora, Fauna and Biodiversity|
|Objective Field:||Marine Flora, Fauna and Biodiversity|
|UTAS Author:||Yoshida, K (Mr Kazuhiro Yoshida)|
|Web of Science® Times Cited:||3|
|Deposited By:||Ecology and Biodiversity|
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