Adaptive strategies by Southern Ocean phytoplankton to lessen iron limitation: Uptake of organically complexed iron and reduced cellular iron requirements

We report results of laboratory studies examining the effect of low levels of iron (Fe) availability on the intracellular Fe concentrations and specific growth rates in Southern Ocean diatoms ( Fragilariopsis kerguelensis , Eucampia antarctica , Proboscia inermis , and Thalassiosira antarctica ) and...

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Bibliographic Details
Published in:Limnology and Oceanography
Main Authors: Strzepek, Robert F., Maldonado, Maria T., Hunter, Keith A., Frew, Russell D., Boyd, Philip W.
Format: Article in Journal/Newspaper
Language:English
Published: Wiley 2011
Subjects:
Southern Ocean
Antarc*
Antarctica
Online Access:http://dx.doi.org/10.4319/lo.2011.56.6.1983
https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.4319%2Flo.2011.56.6.1983
https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.2011.56.6.1983
Description
Summary:We report results of laboratory studies examining the effect of low levels of iron (Fe) availability on the intracellular Fe concentrations and specific growth rates in Southern Ocean diatoms ( Fragilariopsis kerguelensis , Eucampia antarctica , Proboscia inermis , and Thalassiosira antarctica ) and Phaeocystis antarctica . All species grew on Fe complexed to the siderophore desferrioxamine B (DFB). Concentrations of DFB up to 100‐fold in excess of Fe were required to limit growth rates by ≥ 50%. Southern Ocean phytoplankton also grew on Fe complexed by ≥ 10‐fold excess concentrations of the siderophores ferrichrome, enterobactin, or aerobactin, whereas the temperate coastal diatoms Thalassiosira weissflogii and Thalassiosira pseudonana did not. Intracellular Fe concentrations and Fe : C ratios of all Southern Ocean species were exceptionally low and decreased with decreasing Fe availability. However, large diatoms had significantly lower cell‐volume‐normalized Fe content and Fe : C ratios than Phaeocystis . Short‐term Fe uptake and extracellular Fe(II) production measurements provided evidence that Phaeocystis possesses a reductive Fe transport pathway. Our findings demonstrate that the large‐diatom Fe requirements are at least 2‐fold lower than currently reported for oceanic algal species and suggest that bioreduction may enable resident phytoplankton to directly use Fe bound to strong organic ligands.

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