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Marine Ecology Progress Series

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MEPS 578:35-50 (2017)  -  DOI:

Iron sources alter the response of Southern Ocean phytoplankton to ocean acidification

Scarlett Trimborn1,2,*, Tina Brenneis1, Clara J. M. Hoppe1, Luis M. Laglera3, Louiza Norman4, Juan Santos-Echeandía5, Christian Völkner1, Dieter Wolf-Gladrow1, Christel S. Hassler

1Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven 27570, Germany
2University of Bremen, Leobener Straße NW2, Bremen 28359, Germany
3FI-TRACE, University of Balearic Islands, Palma 07122, Spain
4University of Cambridge, Cambridge CB2 3EA, UK
5Spanish Institute of Oceanography (IEO), San Pedro del Pinatar 30740, Spain
6Department F.-A. Forel, University of Geneva, Geneva 1211, Switzerland
*Corresponding author:

ABSTRACT: The projected rise in anthropogenic CO2 and associated ocean acidification (OA) will change trace metal solubility and speciation, potentially altering Southern Ocean (SO) phytoplankton productivity and species composition. As iron (Fe) sources are important determinants of Fe bioavailability, we assessed the effect of Fe-laden dust versus inorganic Fe (FeCl3) enrichment under ambient and high pCO2 levels (390 and 900 µatm) in a naturally Fe-limited SO phytoplankton community. Despite similar Fe chemical speciation and net particulate organic carbon (POC) production rates, CO2-dependent species shifts were controlled by Fe sources. Final phytoplankton communities of both control and dust treatments were dominated by the same species, with an OA-dependent shift from the diatom Pseudo-nitzschia prolongatoides towards the prymnesiophyte Phaeocystis antarctica. Addition of FeCl3 resulted in high abundances of Nitzschia lecointei and Chaetoceros neogracilis under ambient and high pCO2, respectively. These findings reveal that both the characterization of the phytoplankton community at the species level and the use of natural Fe sources are essential for a realistic projection of the biological carbon pump in the Fe-limited pelagic SO under OA. As dust deposition represents a more realistic scenario for the Fe-limited pelagic SO under OA, unaffected net POC production and dominance of P. antarctica can potentially weaken the export of carbon and silica in the future.

KEY WORDS: Climate change · Ocean acidification · Phytoplankton · Iron · Dust · Southern Ocean · Community composition · Diatoms · Phaeocystis

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Cite this article as: Trimborn S, Brenneis T, Hoppe CJM, Laglera LM and others (2017) Iron sources alter the response of Southern Ocean phytoplankton to ocean acidification. Mar Ecol Prog Ser 578:35-50.

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