Major changes in the composition of a Southern Ocean bacterial community in response to diatom-derived dissolved organic matter

• Published in: FEMS Microbiology Ecology
• Main Authors: Landa, Marine, Blain, Stéphane, Harmand, Jérôme, Monchy, Sébastien, Rapaport, Alain, Obernosterer, Ingrid
• Other Authors: Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire océanologique de Banyuls (OOB), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), University of California Santa Cruz (UC Santa Cruz), University of California (UC), Laboratoire de Biotechnologie de l'Environnement Narbonne (LBE), Institut National de la Recherche Agronomique (INRA)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD France-Nord ), Mathématiques, Informatique et STatistique pour l'Environnement et l'Agronomie (MISTEA), Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences de l'Univers (INSU)-Les Enveloppes Fluides et l'Environnement (LEFE)-Cycles Biogeochimiques, Environnement et Ressources (CYBER), French Ministry of Science, ANR-10-BLAN-0614,KEOPS 2,Kerguelen : Comparaison plateau Ocean2(2010)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: Dissolved organic matter; Southern Ocean; Bacterial community composition; 16S rRNA gene sequencing; Continuous cultures; [SDV.BID]Life Sciences [q-bio]/Biodiversity; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [MATH.MATH-DS]Mathematics [math]/Dynamical Systems [math.DS]; [INFO.INFO-MO]Computer Science [cs]/Modeling and Simulation; Kerguelen; Kerguelen Island
• Online Access: https://hal.science/hal-01734675; https://hal.science/hal-01734675/document; https://hal.science/hal-01734675/file/fiy034.pdf; https://doi.org/10.1093/femsec/fiy034

International audience In the Southern Ocean, natural iron fertilization in the wake of islands leads to annually occurring spring phytoplankton blooms associated with enhanced heterotrophic activity through the release of labile dissolved organic matter (DOM). The aim of this study was to investigate experimentally how diatom-derived DOM affects the composition of Southern Ocean winter water bacterial communities and to identify the most responsive taxa. A bacterial community collected in the naturally iron-fertilized region off Kerguelen Island (KEOPS2 October-November 2011) was grown onboard in continuous cultures, on winter water alone or amended with diatom-derived DOM supplied at identical DOC concentrations. 454 sequencing of 16S amplicons revealed that the two DOM sources sustained strikingly different bacterial communities, with higher relative abundances of Sulfitobacter, Colwellia and Methylophaga OTUs and lower relative abundances of Polaribacter, Marinobacter, NAC11–7 and SAR11 OTUs in diatom-DOM compared to winter water conditions. Using a modeling approach, we obtained growth rates for phylogenetically diverse taxa varying between 0.12 and 0.49 d−1 under carbon-limited conditions. Our results identify diatom-DOM as a key factor shaping Southern Ocean winter water bacterial communities and suggest a role for niche partitioning and microbial interactions in organic matter utilization.