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Seagrass-Mediated Phosphorus and Iron Solubilization in Tropical Sediments
journal contribution
posted on 2017-11-17, 00:00 authored by Kasper
Elgetti Brodersen, Klaus Koren, Maria Moßhammer, Peter J. Ralph, Michael Kühl, Jakob SantnerTropical seagrasses are nutrient-limited
owing to the strong phosphorus
fixation capacity of carbonate-rich sediments, yet they form densely
vegetated, multispecies meadows in oligotrophic tropical waters. Using
a novel combination of high-resolution, two-dimensional chemical imaging
of O2, pH, iron, sulfide, calcium, and phosphorus, we found
that tropical seagrasses are able to mobilize the essential nutrients
iron and phosphorus in their rhizosphere via multiple biogeochemical
pathways. We show that tropical seagrasses mobilize phosphorus and
iron within their rhizosphere via plant-induced local acidification,
leading to dissolution of carbonates and release of phosphate, and
via local stimulation of microbial sulfide production, causing reduction
of insoluble Fe(III) oxyhydroxides to dissolved Fe(II) with concomitant
phosphate release into the rhizosphere porewater. These nutrient mobilization
mechanisms have a direct link to seagrass-derived radial O2 loss and secretion of dissolved organic carbon from the below-ground
tissue into the rhizosphere. Our demonstration of seagrass-derived
rhizospheric phosphorus and iron mobilization explains why seagrasses
are widely distributed in oligotrophic tropical waters.
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carbonate-rich sedimentsSeagrass-Mediated Phosphorusbelow-ground tissueO 2chemical imagingoligotrophicphosphate releaseTropical Sediments Tropical seagrassesIron Solubilizationseagrass-derived rhizospheric phosphorusnovel combinationFerhizosphere porewateriron mobilizationbiogeochemical pathwaysmultispecies meadowssulfide productionphosphorus fixation capacitymobilization mechanismsO 2 lossnutrients iron
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