Exopolymeric Substances Control Microbial Community Structure and Function by Contributing to both C and Fe Nutrition in Fe-Limited Southern Ocean Provinces

• Main Authors: Blanco-Ameijeiras, Sonia, Cabanes, Damien, Cable, Rachel, Trimborn, Scarlett, Jacquet, Stéphan, Wiegmann, Sonja, Völkner, Christian, Lelchat, Florian, Bracher, Astrid, Duhaime, Melissa, Hassler, Christel
• Other Authors: Université de Genève = University of Geneva (UNIGE), University of Michigan Dearborn, University of Michigan System, Helmholtz Ctr Polar & Marine Res, Alfred Wegener Inst, D-27570 Bremerhaven, Germany, University of Bremen, Centre Alpin de Recherche sur les Réseaux Trophiques et Ecosystèmes Limniques (CARRTEL), Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Observatoire des Sciences de l'Univers de Grenoble (Fédération OSUG), Ecole Polytechnique Fédérale de Lausanne (EPFL), University of Geneva FNS PP00P2-138955Helmholtz Association (Young Investigators Group EcoTrace) VH-NG-901
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: virus; prokaryotes; phytoplankton; Southern Ocean; exopolymeric substances; iron; [SDV.MP]Life Sciences [q-bio]/Microbiology and Parasitology; Drake Passage
• Online Access: https://hal.inrae.fr/hal-03151884; https://hal.inrae.fr/hal-03151884/document; https://hal.inrae.fr/hal-03151884/file/2020_Blanco_Microorganisms.pdf; https://doi.org/10.3390/microorganisms8121980

International audience Organic ligands such as exopolymeric substances (EPS) are known to form complexes with iron (Fe) and modulate phytoplankton growth. However, the effect of organic ligands on bacterial and viral communities remains largely unknown. Here, we assessed how Fe associated with organic ligands influences phytoplankton, microbial, and viral abundances and their diversity in the Southern Ocean. While the particulate organic carbon (POC) was modulated by Fe chemistry and bioavailability in the Drake Passage, the abundance and diversity of microbes and viruses were not governed by Fe bioavailability. Only following amendments with bacterial EPS did bacterial abundances increase, while phenotypic alpha diversity of bacterial and viral communities decreased. The latter was accompanied by significantly enhanced POC, pointing toward the relief of C limitation or other drivers of the microbial loop. Based on the literature and our findings, we propose a conceptual framework by which EPS may affect phytoplankton, bacteria, and viruses. Given the importance of the Southern Ocean for Earth's climate as well as the prevalence of viruses and their increasingly recognized impact on marine biogeochemistry and C cycling; the role of microbe-virus interactions on primary productivity in the Southern Ocean needs urgent attention.