• Medientyp: E-Artikel
  • Titel: Spatial heterogeneity and short‐term oxygen dynamics in the rhizosphere of Vallisneria spiralis: Implications for nutrient cycling
  • Beteiligte: Marzocchi, Ugo; Benelli, Sara; Larsen, Morten; Bartoli, Marco; Glud, Ronnie N.
  • Erschienen: Wiley, 2019
  • Erschienen in: Freshwater Biology
  • Umfang: 532-543
  • Sprache: Englisch
  • DOI: 10.1111/fwb.13240
  • ISSN: 1365-2427; 0046-5070
  • Schlagwörter: Aquatic Science
  • Zusammenfassung: <jats:title>Abstract</jats:title><jats:p> <jats:list> <jats:list-item><jats:p>Aquatic macrophytes modify the sediment biogeochemistry via radial oxygen loss (<jats:styled-content style="fixed-case">ROL</jats:styled-content>) from their roots. However, the variation in <jats:styled-content style="fixed-case">ROL</jats:styled-content> and its implication for nutrient availability remains poorly explored.</jats:p></jats:list-item> <jats:list-item><jats:p>Here, we use planar O<jats:sub>2</jats:sub> optodes to investigate the spatial heterogeneity of oxic niches within the rhizosphere of <jats:italic>Vallisneria spiralis</jats:italic> and their alteration following variable light and ambient O<jats:sub>2</jats:sub> levels. The effect of <jats:styled-content style="fixed-case">ROL</jats:styled-content> on <jats:styled-content style="fixed-case">NH</jats:styled-content><jats:sub>4</jats:sub><jats:sup>+</jats:sup> and <jats:styled-content style="fixed-case">PO</jats:styled-content><jats:sub>4</jats:sub><jats:sup>3−</jats:sup> distribution in the rhizosphere was evaluated by a combination of <jats:sup>15</jats:sup>N isotopic techniques, 2D sampling, and electron microscopy.</jats:p></jats:list-item> <jats:list-item><jats:p>A single specimen of <jats:italic>V. spiralis</jats:italic> could maintain an oxidised sediment volume of 41–47 cm<jats:sup>3</jats:sup> and 10–27 cm<jats:sup>3</jats:sup> in the rhizosphere at 100% and 38% dissolved oxygen saturation in the overlying water, respectively. Whatever the environmental conditions, the <jats:styled-content style="fixed-case">ROL</jats:styled-content> was, however, very heterogeneous and dependent on root age and architecture of the root system.</jats:p></jats:list-item> <jats:list-item><jats:p><jats:styled-content style="fixed-case">ROL</jats:styled-content> stimulated the coupling between denitrification and nitrification in the sediment both under dark (+25 μmol N‐N<jats:sub>2</jats:sub> m<jats:sup>−2</jats:sup> hr<jats:sup>−1</jats:sup>) and light (+70 μmol N‐N<jats:sub>2</jats:sub> m<jats:sup>−2</jats:sup> hr<jats:sup>−1</jats:sup>) conditions. This, in combination with plant uptake, contributed to intense removal of <jats:styled-content style="fixed-case">NH</jats:styled-content><jats:sub>4</jats:sub><jats:sup>+</jats:sup> from the pore water. Similarly, <jats:styled-content style="fixed-case">PO</jats:styled-content><jats:sub>4</jats:sub><jats:sup>3−</jats:sup> was highly depleted in the rhizosphere. The detection of Fe‐P plaques on the roots surface indicated substantial entrapment of P as a consequence of <jats:styled-content style="fixed-case">ROL</jats:styled-content>.</jats:p></jats:list-item> <jats:list-item><jats:p>The extensive spatio‐temporal heterogeneity of oxic and anoxic conditions ensured that aerobic and anaerobic processes co‐occurred in the rhizosphere and this presumably reduced potential nutrient limitation while maximising plant fitness in an otherwise hostile reduced environment.</jats:p></jats:list-item> </jats:list> </jats:p>
  • Beschreibung: <jats:title>Abstract</jats:title><jats:p>
    <jats:list>

    <jats:list-item><jats:p>Aquatic macrophytes modify the sediment biogeochemistry via radial oxygen loss (<jats:styled-content style="fixed-case">ROL</jats:styled-content>) from their roots. However, the variation in <jats:styled-content style="fixed-case">ROL</jats:styled-content> and its implication for nutrient availability remains poorly explored.</jats:p></jats:list-item>

    <jats:list-item><jats:p>Here, we use planar O<jats:sub>2</jats:sub> optodes to investigate the spatial heterogeneity of oxic niches within the rhizosphere of <jats:italic>Vallisneria spiralis</jats:italic> and their alteration following variable light and ambient O<jats:sub>2</jats:sub> levels. The effect of <jats:styled-content style="fixed-case">ROL</jats:styled-content> on <jats:styled-content style="fixed-case">NH</jats:styled-content><jats:sub>4</jats:sub><jats:sup>+</jats:sup> and <jats:styled-content style="fixed-case">PO</jats:styled-content><jats:sub>4</jats:sub><jats:sup>3−</jats:sup> distribution in the rhizosphere was evaluated by a combination of <jats:sup>15</jats:sup>N isotopic techniques, 2D sampling, and electron microscopy.</jats:p></jats:list-item>

    <jats:list-item><jats:p>A single specimen of <jats:italic>V. spiralis</jats:italic> could maintain an oxidised sediment volume of 41–47 cm<jats:sup>3</jats:sup> and 10–27 cm<jats:sup>3</jats:sup> in the rhizosphere at 100% and 38% dissolved oxygen saturation in the overlying water, respectively. Whatever the environmental conditions, the <jats:styled-content style="fixed-case">ROL</jats:styled-content> was, however, very heterogeneous and dependent on root age and architecture of the root system.</jats:p></jats:list-item>

    <jats:list-item><jats:p><jats:styled-content style="fixed-case">ROL</jats:styled-content> stimulated the coupling between denitrification and nitrification in the sediment both under dark (+25 μmol N‐N<jats:sub>2</jats:sub> m<jats:sup>−2</jats:sup> hr<jats:sup>−1</jats:sup>) and light (+70 μmol N‐N<jats:sub>2</jats:sub> m<jats:sup>−2</jats:sup> hr<jats:sup>−1</jats:sup>) conditions. This, in combination with plant uptake, contributed to intense removal of <jats:styled-content style="fixed-case">NH</jats:styled-content><jats:sub>4</jats:sub><jats:sup>+</jats:sup> from the pore water. Similarly, <jats:styled-content style="fixed-case">PO</jats:styled-content><jats:sub>4</jats:sub><jats:sup>3−</jats:sup> was highly depleted in the rhizosphere. The detection of Fe‐P plaques on the roots surface indicated substantial entrapment of P as a consequence of <jats:styled-content style="fixed-case">ROL</jats:styled-content>.</jats:p></jats:list-item>

    <jats:list-item><jats:p>The extensive spatio‐temporal heterogeneity of oxic and anoxic conditions ensured that aerobic and anaerobic processes co‐occurred in the rhizosphere and this presumably reduced potential nutrient limitation while maximising plant fitness in an otherwise hostile reduced environment.</jats:p></jats:list-item>
    </jats:list>
    </jats:p>
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