Regulation of the Phytoplankton Heme b Iron Pool During the North Atlantic Spring Bloom
|Author(s)||Louropoulou Evangelia1, 2, Gledhill Martha1, Browningi Thomas J.1, Desai Dhwani K.3, Barraqueta Jan-Lukas Menzel1, 4, Tonnard Manon5, 6, 7, Sarthou Geraldine5, Planquette Helene5, Bowie Andrew R.6, 7, Schmitz Ruth A.2, Laroche Julie3, Achterberg Eric P.1|
|Affiliation(s)||1 : GEOMAR Helmholtz Ctr Ocean Res Kiel, Kiel, Germany.
2 : Christian Albrechts Univ Kiel, Inst Gen Microbiol, Kiel, Germany.
3 : Dalhousie Univ, Dept Biol, Halifax, NS, Canada.
4 : Stellenbosch Univ, Dept Earth Sci, Stellenbosch, South Africa.
5 : UBO, IFREMER, CNRS, UMR 6539,LEMAR,IUEM,IRD, Brest, France.
6 : Antarctic Climate & Ecosyst Cooperat Res Ctr, Hobart, Tas, Australia.
7 : Univ Tasmania, Inst Marine & Antarctic Studies, Hobart, Tas, Australia.
|Source||Frontiers In Microbiology (1664-302X) (Frontiers Media Sa), 2019-07 , Vol. 10 , N. 1566 , P. 16p.|
|WOS© Times Cited||3|
|Keyword(s)||heme b, North Atlantic, phytoplankton, diatoms, iron, limitation, GEOTRACES, GEOVIDE|
|Abstract||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.|