Please use this identifier to cite or link to this item: https://hdl.handle.net/2440/130559
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Type: Journal article
Title: Low Fe availability for photosynthesis of sea-ice algae: ex situ incubation of the ice diatom fragilariopsis cylindrus in low-Fe sea ice using an ice tank
Author: Yoshida, K.
Seger, A.
Corkill, M.
Heil, P.
Karsh, K.
McMinn, A.
Suzuki, K.
Citation: Frontiers in Marine Science, 2021; 8:1-20
Publisher: Frontiers Media
Issue Date: 2021
ISSN: 2296-7745
Statement of
Responsibility: 
Kazuhiro Yoshida, Andreas Seger, Matthew Corkill, Petra Heil, Kristen Karsh, Andrew McMinn and Koji Suzuki
Abstract: <jats:p>Sea-ice algae play a crucial role in the ecology and biogeochemistry of sea-ice zones. They not only comprise the base of sea-ice ecosystems, but also seed populations of extensive ice-edge blooms during ice melt. Ice algae must rapidly acclimate to dynamic light environments, from the low light under sea ice to high light within open waters. Recently, iron (Fe) deficiency has been reported for diatoms in eastern Antarctic pack ice. Low Fe availability reduces photosynthetic plasticity, leading to reduced ice-algal primary production. We developed a low-Fe ice tank to manipulate Fe availability in sea ice. Over 20 days in the ice tank, the Antarctic ice diatom <jats:italic>Fragilariopsis cylindrus</jats:italic> was incubated in artificial low-Fe sea ice ([total Fe] = 20 nM) in high light (HL) and low light (LL) conditions. Melted ice was also exposed to intense light to simulate light conditions typical for melting ice <jats:italic>in situ</jats:italic>. When diatoms were frozen in, the maximum photochemical quantum efficiency of photosystem II (PSII), <jats:italic>F</jats:italic><jats:sub>v</jats:sub>/<jats:italic>F</jats:italic><jats:sub>m</jats:sub>, was suppressed by freezing stress. However, the diatoms maintained photosynthetic capability throughout the ice periods with a stable <jats:italic>F</jats:italic><jats:sub>v</jats:sub>/<jats:italic>F</jats:italic><jats:sub>m</jats:sub> value and increased photoprotection through non-photochemical quenching (NPQ) via photoprotective xanthophyll cycling (XC) and increased photoprotective carotenoid levels compared to pre-freeze-up. Photoprotection was more pronounced in the HL treatment due to greater light stress. However, the functional absorption cross section of PSII, σ<jats:sub>PSII</jats:sub>, in <jats:italic>F. cylindrus</jats:italic> consistently increased after freezing, especially in the LL treatment (σ<jats:sub>PSII</jats:sub> &amp;gt; 10 nm<jats:sup>2</jats:sup> PSII<jats:sup>–1</jats:sup>). Our study is the first to report such a large σ<jats:sub>PSII</jats:sub> in ice diatoms at low Fe conditions. When the melted sea ice was exposed to high light, <jats:italic>F</jats:italic><jats:sub>v</jats:sub>/<jats:italic>F</jats:italic><jats:sub>m</jats:sub> was suppressed. NPQ and XC were slightly upregulated, but not to values normally observed when Fe is not limiting, which indicates reduced photosynthetic flexibility to adapt to environmental changes during ice melt under low Fe conditions. Although ice algae can optimize their photosynthesis to sea-ice environments, chronic Fe starvation led to less flexibility of photoacclimation, particularly in low light conditions. This may have detrimental consequences for ice algal production and trophic interactions in sea-ice ecosystems if the recent reduction in sea-ice extent continues.</jats:p>
Keywords: Sea-ice diatom; pack ice; iron limitation; ice-edge bloom; Southern Ocean; chlorophyll a fluorescence; gene expression; photoprotection
Rights: © 2021 Yoshida, Seger, Corkill, Heil, Karsh, McMinn and Suzuki. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
DOI: 10.3389/fmars.2021.632087
Grant ID: http://purl.org/au-research/grants/arc/SR140300001
Published version: http://dx.doi.org/10.3389/fmars.2021.632087
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Environment Institute publications

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