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Iron limitation drives the globally extreme fluorescence/chlorophyll ratios of the Southern Ocean


Schallenberg, C and Strzepek, RF and Bestley, S and Wojtasiewicz, B and Trull, TW, Iron limitation drives the globally extreme fluorescence/chlorophyll ratios of the Southern Ocean, Geophysical Research Letters, 49, (12) Article e2021GL097616. ISSN 0094-8276 (2022) [Refereed Article]

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Copyright Statement

Copyright 2022 The Author(s). This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) License, ( which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

DOI: doi:10.1029/2021GL097616


The ratio between fluorescence (F) and chlorophyll-a (Chl)—where fluorescence is measured with a saturating fluorometer—is variable in the world's oceans, with the highest ratios and highest variability observed in the Southern Ocean. While species composition and Chl packaging per cell are strong drivers for the observed variability, additional factors, including iron limitation, have to this date not specifically been evaluated. Radiometers on biogeochemical (BGC)-Argo floats allow for an independent estimate of Chl concentration that is based on the light attenuation coefficient, Kd. Making use of 4,000 radiometry profiles from BGC-Argo floats in the Southern Ocean, we estimate Chl based on Kd and investigate the variability in F/Chl. Our analysis reveals a positive correlation between F/Chl and a proxy for iron limitation based on non-photochemical quenching dynamics. The strong influence of iron limitation on F/Chl is further corroborated by data from Southern Ocean phytoplankton cultures.

Item Details

Item Type:Refereed Article
Keywords:phytoplankton, chlorophyll fluorescence, iron, Southern Ocean, Argo
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:Schallenberg, C (Dr Christina Schallenberg)
UTAS Author:Strzepek, RF (Dr Robert Strzepek)
UTAS Author:Bestley, S (Dr Sophie Bestley)
UTAS Author:Wojtasiewicz, B (Dr Bozena Wojtasiewicz)
UTAS Author:Trull, TW (Professor Thomas Trull)
ID Code:150899
Year Published:2022
Deposited By:Australian Antarctic Program Partnership
Deposited On:2022-07-04
Last Modified:2022-08-08
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