Chasing iron bioavailability in the Southern Ocean: Insights from Phaeocystis antarctica and iron speciation ...

• Main Authors: Fourquez, Marion, Janssen, David J., Conway, Tim M., Cabanes, Damien, Ellwood, Michael J., Sieber, Matthias, Trimborn, Scarlett, Hassler, Christel
• Format: Article in Journal/Newspaper
• Language: English
• Published: ETH Zurich 2023
• Subjects: Antarc*; Antarctica; Southern Ocean
• Online Access: https://dx.doi.org/10.3929/ethz-b-000621914; http://hdl.handle.net/20.500.11850/621914

Dissolved iron (dFe) availability limits the uptake of atmospheric CO2 by the Southern Ocean (SO) biological pump. Hence, any change in bioavailable dFe in this region can directly influence climate. On the basis of Fe uptake experiments with Phaeocystis antarctica, we show that the range of dFe bioavailability in natural samples is wider (<1 to ~200% compared to free inorganic Fe') than previously thought, with higher bioavailability found near glacial sources. The degree of bioavailability varied regardless of in situ dFe concentration and depth, challenging the consensus that sole dFe concentrations can be used to predict Fe uptake in modeling studies. Further, our data suggest a disproportionately major role of biologically mediated ligands and encourage revisiting the role of humic substances in influencing marine Fe biogeochemical cycling in the SO. Last, we describe a linkage between in situ dFe bioavailability and isotopic signatures that, we anticipate, will stimulate future research. ... : Science Advances, 9 (26) ...