Marconi Dario

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Marconi
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Dario
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  • Dataset
    Compiled dataset consisting of published and unpublished global nitrate d15N measurements from from 1975-2018
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-06-17) Rafter, Patrick ; Bagnell, Aaron ; DeVries, Timothy ; Marconi, Dario
    Nitrate d15N observations were compiled from studies dating from 1975 to 2018. Whenever possible, the data was acquired via the original author, but in other cases the data was estimated from the publication directly. All observations were treated equally, although the failure to remove nitrite when using the "denitrifier method" may bias the nitrate d15N to low values (Rafter et al., 2013). This version of the dataset (1.0) will be updated as new data are published. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/768627
  • Dataset
    Estimated nitrate d15N modeled using an ensemble of artificial neural networks (EANNs)
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-06-17) Rafter, Patrick ; Bagnell, Aaron ; DeVries, Timothy ; Marconi, Dario
    We utilize an ensemble of artificial neural networks (EANNs) to interpolate our global ocean nitrate d15N database, producing complete 3D maps of the data. By utilizing an artificial neural network (ANN), a machine learning approach that effectively identifies nonlinear relationships between a target variable (the isotopic dataset) and a set of input features (other available ocean datasets), we can fill holes in our data sampling coverage of nitrate d15N. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/768655
  • Article
    The Angola Gyre is a hotspot of dinitrogen fixation in the South Atlantic Ocean
    (Nature Research, 2022-06-30) Marshall, Tanya ; Granger, Julie ; Casciotti, Karen L. ; Dähnke, Kirstin ; Emeis, Kay-Christian ; Marconi, Dario ; McIlvin, Matthew R. ; Noble, Abigail E. ; Saito, Mak A. ; Sigman, Daniel M. ; Fawcett, Sarah E.
    Biological dinitrogen fixation is the major source of new nitrogen to marine systems and thus essential to the ocean’s biological pump. Constraining the distribution and global rate of dinitrogen fixation has proven challenging owing largely to uncertainty surrounding the controls thereon. Existing South Atlantic dinitrogen fixation rate estimates vary five-fold, with models attributing most dinitrogen fixation to the western basin. From hydrographic properties and nitrate isotope ratios, we show that the Angola Gyre in the eastern tropical South Atlantic supports the fixation of 1.4–5.4 Tg N.a−1, 28-108% of the existing (highly uncertain) estimates for the basin. Our observations contradict model diagnoses, revealing a substantial input of newly-fixed nitrogen to the tropical eastern basin and no dinitrogen fixation west of 7.5˚W. We propose that dinitrogen fixation in the South Atlantic occurs in hotspots controlled by the overlapping biogeography of excess phosphorus relative to nitrogen and bioavailable iron from margin sediments. Similar conditions may promote dinitrogen fixation in analogous ocean regions. Our analysis suggests that local iron availability causes the phosphorus-driven coupling of oceanic dinitrogen fixation to nitrogen loss to vary on a regional basis.