Regulation of the Phytoplankton Heme b Iron Pool During the North Atlantic Spring Bloom

• Published in: Frontiers in Microbiology
• Main Authors: Louropoulou, Evangelia, Gledhill, Martha, Browning, Thomas, Desai, Dhwani K., Barraqueta, Jan-Lukas Menzel, Tonnard, Manon, Sarthou, Géraldine, Planquette, Hélène, Bowie, Andrew, R., Schmitz, Ruth, Laroche, Julie, Achterberg, Eric
• Other Authors: Helmholtz Centre for Ocean Research Kiel (GEOMAR), Christian-Albrechts-Universität zu Kiel (CAU), Dalhousie University Halifax, Department of Earth Sciences Stellenbosch, Stellenbosch University, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Antarctic Climate and Ecosystems Cooperative Research Centre (ACE-CRC), Institute for Marine and Antarctic Studies Hobart (IMAS), University of Tasmania Hobart, Australia (UTAS), . Biodisponibilité du fer et des métaux traces dans les particules marines (2012). Une étude internationale GEOTRACES le long de la section OVIDE en Atlantique Nord et en Mer du Labrador (2013). LabexMER Marine Excellence Research: a changing ocean (2010), ANR-12-PDOC-0025,BITMAP,Biodisponibilité du fer et des métaux traces dans les particules marines(2012), ANR-13-BS06-0014,GEOVIDE,GEOVIDE, Une étude internationale GEOTRACES le long de la section OVIDE en Atlantique Nord et en Mer du Labrador(2013), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: heme b; North Atlantic; phytoplankton; diatoms; iron; limitation; GEOTRACES; GEOVIDE; ACL; [SDV.MP]Life Sciences [q-bio]/Microbiology and Parasitology; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Irminger Basin; Iceland; Labrador Sea
• Online Access: https://hal.science/hal-02322547; https://hal.science/hal-02322547/document; https://hal.science/hal-02322547/file/Louropoulou_etal_FiM_2019.pdf; https://doi.org/10.3389/fmicb.2019.01566

International audience Heme b is an iron-containing co-factor in hemoproteins. Heme b concentrations are low (< 1 pmol L-1) in iron limited phytoplankton in cultures and in the field. Here, we determined heme b in marine particulate material (> 0.7 mu m) from the North Atlantic Ocean (GEOVIDE cruise - GEOTRACES section GA01), which spanned several biogeochemical regimes. We examined the relationship between heme b abundance and the microbial community composition, and its utility for mapping iron limited phytoplankton. Heme b concentrations ranged from 0.16 to 5.1 pmol L-1 (median = 2.0 pmol L-1, n = 62) in the surface mixed layer (SML) along the cruise track, driven mainly by variability in biomass. However, in the Irminger Basin, the lowest heme b levels (SML: median = 0.53 pmol L-1, n = 12) were observed, whilst the biomass was highest (particulate organic carbon, median = 14.2 mu mol L-1, n = 25; chlorophyll a: median = 2.0 nmol L-1, n = 23) pointing to regulatory mechanisms of the heme b pool for growth conservation. Dissolved iron (DFe) was not depleted (SML: median = 0.38 nmol L-1, n = 11) in the Irminger Basin, but large diatoms (Rhizosolenia sp.) dominated. Hence, heme b depletion and regulation is likely to occur during bloom progression when phytoplankton class-dependent absolute iron requirements exceed the available ambient concentration of DFe. Furthermore, high heme b concentrations found in the Iceland Basin and Labrador Sea (median = 3.4 pmol L-1, n = 20), despite having similar DFe concentrations to the Irminger Basin, were attributed to an earlier growth phase of the extant phytoplankton populations. Thus, heme b provides a snapshot of the cellular activity in situ and could both be used as indicator of iron limitation and contribute to understanding phytoplankton adaptation mechanisms to changing iron supplies.