• Medientyp: E-Artikel
  • Titel: Regulation of the Phytoplankton Heme b Iron Pool During the North Atlantic Spring Bloom
  • Beteiligte: Louropoulou, Evangelia [VerfasserIn]; Gledhill, Martha [VerfasserIn]; Browning, Thomas J. [VerfasserIn]; Desai, Dhwani K. [VerfasserIn]; Menzel Barraqueta, Jan-Lukas [VerfasserIn]; Tonnard, Manon [VerfasserIn]; Sarthou, Géraldine [VerfasserIn]; Planquette, Hélène [VerfasserIn]; Bowie, Andrew R. [VerfasserIn]; Schmitz, Ruth A. [VerfasserIn]; LaRoche, Julie [VerfasserIn]; Achterberg, Eric P. [VerfasserIn]
  • Erschienen: Frontiers, 2019-07-11
  • Sprache: Englisch
  • DOI: https://doi.org/10.3389/fmicb.2019.01566
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  • Beschreibung: 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 μm) 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 μmol 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.
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