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Photosynthetic adaptation to low iron, light, and temperature in Southern Ocean phytoplankton


Strzepek, RF and Boyd, PW and Sunda, WG, Photosynthetic adaptation to low iron, light, and temperature in Southern Ocean phytoplankton, Proceedings of the National Academy of Sciences of the United States of America, 116, (10) pp. 4388-4393. ISSN 0027-8424 (2019) [Refereed Article]

Copyright Statement

Copyright 2019 The Authors

DOI: doi:10.1073/pnas.1810886116


Phytoplankton productivity in the polar Southern Ocean (SO) plays an important role in the transfer of carbon from the atmosphere to the oceanís interior, a process called the biological carbon pump, which helps regulate global climate. SO productivity in turn is limited by low iron, light, and temperature, which restrict the efficiency of the carbon pump. Iron and light can colimit productivity due to the high iron content of the photosynthetic photosystems and the need for increased photosystems for low-light acclimation in many phytoplankton. Here we show that SO phytoplankton have evolved critical adaptations to enhance photosynthetic rates under the joint constraints of low iron, light, and temperature. Under growth-limiting iron and light levels, three SO species had up to sixfold higher photosynthetic rates per photosystem II and similar or higher rates per mol of photosynthetic iron than temperate species, despite their lower growth temperature (3 vs. 18 įC) and light intensity (30 vs. 40 μmol quanta⋅m2⋅s−1), which should have decreased photosynthetic rates. These unexpectedly high rates in the SO species are partly explained by their unusually large photosynthetic antennae, which are among the largest ever recorded in marine phytoplankton. Large antennae are disadvantageous at low light intensities because they increase excitation energy loss as heat, but this loss may be mitigated by the low SO temperatures. Such adaptations point to higher SO production rates than environmental conditions should otherwise permit, with implications for regional ecology and biogeochemistry.

Item Details

Item Type:Refereed Article
Keywords:iron, light, temperature, Southern Ocean, phytoplankton
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Biological oceanography
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Antarctic and Southern Ocean oceanic processes
UTAS Author:Strzepek, RF (Dr Robert Strzepek)
UTAS Author:Boyd, PW (Professor Philip Boyd)
ID Code:133839
Year Published:2019
Web of Science® Times Cited:53
Deposited By:Oceans and Cryosphere
Deposited On:2019-07-11
Last Modified:2020-07-17

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