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Differences in cell viabilities of phytoplankton between spring and late summer in the northwest Pacific Ocean

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Title: Differences in cell viabilities of phytoplankton between spring and late summer in the northwest Pacific Ocean
Authors: Hayakawa, Maki Browse this author
Suzuki, Koji Browse this author
Saito, Hiroaki Browse this author
Takahashi, Kazutaka Browse this author
Ito, Shin-ichi Browse this author
Keywords: Phytoplankton
Cell death
Viability
Cell lysis
Oyashio
Pacific Ocean
Issue Date: 6-Jun-2008
Publisher: Elsevier
Journal Title: Journal of Experimental Marine Biology and Ecology
Volume: 360
Issue: 2
Start Page: 63
End Page: 70
Publisher DOI: 10.1016/j.jembe.2008.03.008
Abstract: Cell viabilities of phytoplankton in the Oyashio and Kuroshio-Oyashio transition regions of the northwest Pacific Ocean were examined in September 2003 (late summer) and May 2005 (spring) using a membrane permeability test. Specific lysis rates of the phytoplankton during late summer were also assessed by an esterase activity assay. In late summer, cyanobacteria Synechococcus spp. were > 2 x 10^4 cells ml^[-1] and numerically dominated the phytoplankton communities. The cell viabilities of Synechococcus spp. and eukaryotic ultraphytoplankton (<10 μm in size) were 60-79% and 26-41% in surface waters, respectively. The specific lysis rates of the phytoplankton were 0.12-0.67 d^[-1] in late summer. By contrast, in spring, eukaryotic cells were predominant in the phytoplankton communities. The cell viabilities of surface eukaryotic ultraphytoplankton in spring were > 70% and significantly higher than those in late summer. During spring, Synechococcus spp. only occurred with < 1 x 10^4 cells ml^[-1] in the Kuroshio-Oyashio transition region, and their viabilities were 80%. In the Oyashio region where a spring diatom bloom developed, the viability of fucoxanthin-containing algae (mainly diatoms and prymnesiophytes) was ca. 90%. These results suggested that the cell viability of phytoplankton could vary seasonally with their community structure in the study area. The phytoplankton cell death in late summer was particularly significant for their loss process and could support the microbial food webs by supplying dissolved organic carbon (DOC) derived from the dead cells.
Type: article (author version)
URI: http://hdl.handle.net/2115/39932
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: 早川 真紀

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