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Photosynthetic protein stoichiometry and photophysiology in the high latitude North Atlantic

Photosynthetic protein stoichiometry and photophysiology in the high latitude North Atlantic
Photosynthetic protein stoichiometry and photophysiology in the high latitude North Atlantic
Iron availability influences phytoplankton physiology and growth over more than one-third of the surface oceans, with recent evidence even indicating iron stress during and following the latter stages of the spring bloom in the high latitude North Atlantic. The mechanistic basis of the phytoplankton physiological responses used for diagnosing iron stress and the broader ecophysiological consequences of iron stress within natural phytoplankton communities still remain unclear. We describe photosynthetic macromolecular and physiological responses of natural phytoplankton communities both in situ and within factorial nutrient-addition (iron and nitrogen) experiments over a seasonal growth cycle in the subpolar North Atlantic. The abundance of quantified photosynthetic proteins increased under relief of iron stress, with the synthesis of the associated protein catalytic complexes accounting for ? 3% of inorganic nitrogen drawdown. However, no significant differences in the stoichiometries of the photosynthetic complexes were observed, suggesting that re-modeling of the photosynthetic electron transport chain was not a significant influence on the community-level ecophysiological responses to iron stress. In marked contrast, iron stress resulted in significant increases in the cellular ratios of chlorophyll to the photosynthetic catalysts, including photosystem II (PSII), alongside a marked increase in PSII normalized chlorophyll fluorescence. Characteristic depressions in apparent photosynthetic energy conversion efficiencies in iron-limited oceanic regions are thus likely driven by a significant accumulation of partially energetically uncoupled chlorophyll-binding complexes. Such iron-stress–induced chlorophyll-binding proteins may contribute ? 40% of the total chlorophyll pool during iron-stressed periods.
0024-3590
1853-1864
Macey, A.I.
fcb2ab5c-e144-44c7-bda0-720d1609c760
Ryan-Keogh, T.
df796601-6ed6-47c0-b8a0-fb926b444c35
Richier, S.
0fc0b375-6918-4c06-9d6f-229f6c4046ca
Moore, C.M.
7ec80b7b-bedc-4dd5-8924-0f5d01927b12
Bibby, T.S.
e04ea079-dd90-4ead-9840-00882de27ebd
Macey, A.I.
fcb2ab5c-e144-44c7-bda0-720d1609c760
Ryan-Keogh, T.
df796601-6ed6-47c0-b8a0-fb926b444c35
Richier, S.
0fc0b375-6918-4c06-9d6f-229f6c4046ca
Moore, C.M.
7ec80b7b-bedc-4dd5-8924-0f5d01927b12
Bibby, T.S.
e04ea079-dd90-4ead-9840-00882de27ebd

Macey, A.I., Ryan-Keogh, T., Richier, S., Moore, C.M. and Bibby, T.S. (2014) Photosynthetic protein stoichiometry and photophysiology in the high latitude North Atlantic. Limnology and Oceanography, 59 (6), 1853-1864. (doi:10.4319/lo.2014.59.6.1853).

Record type: Article

Abstract

Iron availability influences phytoplankton physiology and growth over more than one-third of the surface oceans, with recent evidence even indicating iron stress during and following the latter stages of the spring bloom in the high latitude North Atlantic. The mechanistic basis of the phytoplankton physiological responses used for diagnosing iron stress and the broader ecophysiological consequences of iron stress within natural phytoplankton communities still remain unclear. We describe photosynthetic macromolecular and physiological responses of natural phytoplankton communities both in situ and within factorial nutrient-addition (iron and nitrogen) experiments over a seasonal growth cycle in the subpolar North Atlantic. The abundance of quantified photosynthetic proteins increased under relief of iron stress, with the synthesis of the associated protein catalytic complexes accounting for ? 3% of inorganic nitrogen drawdown. However, no significant differences in the stoichiometries of the photosynthetic complexes were observed, suggesting that re-modeling of the photosynthetic electron transport chain was not a significant influence on the community-level ecophysiological responses to iron stress. In marked contrast, iron stress resulted in significant increases in the cellular ratios of chlorophyll to the photosynthetic catalysts, including photosystem II (PSII), alongside a marked increase in PSII normalized chlorophyll fluorescence. Characteristic depressions in apparent photosynthetic energy conversion efficiencies in iron-limited oceanic regions are thus likely driven by a significant accumulation of partially energetically uncoupled chlorophyll-binding complexes. Such iron-stress–induced chlorophyll-binding proteins may contribute ? 40% of the total chlorophyll pool during iron-stressed periods.

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Published date: November 2014
Organisations: Ocean and Earth Science

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Local EPrints ID: 372401
URI: http://eprints.soton.ac.uk/id/eprint/372401
ISSN: 0024-3590
PURE UUID: 822d22d3-219d-46da-b44c-f7ef53015553

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Date deposited: 02 Dec 2014 16:40
Last modified: 15 Jul 2019 21:36

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