Wagner Sasha

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  • Article
    Soothsaying DOM: A current perspective on the future of oceanic dissolved organic carbon
    (Frontiers Media, 2020-05-25) Wagner, Sasha ; Schubotz, Florence ; Kaiser, Karl ; Hallmann, Christian ; Waska, Hannelore ; Rossel, Pamela ; Hansman, Roberta L. ; Elvert, Marcus ; Middelburg, Jack J. ; Engel, Anja ; Blattmann, Thomas M. ; Catalá, Teresa S. ; Lennartz, Sinikka T. ; Gomez-Saez, Gonzalo V. ; Pantoja-Gutiérrez, Silvio ; Bao, Rui ; Galy, Valier
    The vast majority of freshly produced oceanic dissolved organic carbon (DOC) is derived from marine phytoplankton, then rapidly recycled by heterotrophic microbes. A small fraction of this DOC survives long enough to be routed to the interior ocean, which houses the largest and oldest DOC reservoir. DOC reactivity depends upon its intrinsic chemical composition and extrinsic environmental conditions. Therefore, recalcitrance is an emergent property of DOC that is analytically difficult to constrain. New isotopic techniques that track the flow of carbon through individual organic molecules show promise in unveiling specific biosynthetic or degradation pathways that control the metabolic turnover of DOC and its accumulation in the deep ocean. However, a multivariate approach is required to constrain current carbon fluxes so that we may better predict how the cycling of oceanic DOC will be altered with continued climate change. Ocean warming, acidification, and oxygen depletion may upset the balance between the primary production and heterotrophic reworking of DOC, thus modifying the amount and/or composition of recalcitrant DOC. Climate change and anthropogenic activities may enhance mobilization of terrestrial DOC and/or stimulate DOC production in coastal waters, but it is unclear how this would affect the flux of DOC to the open ocean. Here, we assess current knowledge on the oceanic DOC cycle and identify research gaps that must be addressed to successfully implement its use in global scale carbon models.
  • Dataset
    Dissolved black carbon (DBC) concentrations and related data from water samples collected between 2011 and 2019 in the Pacific and Atlantic Oceans and from rivers in North America, South America, Africa, and Russia
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2022-08-19) Wagner, Sasha ; Brandes, Jay ; Stubbins, Aron
    Pacific Ocean samples were collected from Station ALOHA (22.45°N, 158.00°W) during the Hawaii Ocean Time-series (HOT) 301 cruise aboard the R/V Ka`imikai-O-Kanaloa in April 2018. Atlantic Ocean samples were collected from Hydrostation S (31.67°N, 64.17°W) during the Bermuda Atlantic Time Series (BATS) 358 cruise aboard the R/V Atlantic Explorer in April 2019. River samples were collected from the main stem of the Amazon (Brazil), Congo (Democratic Republic of the Congo), Northern Dvina (Russia), Kolyma (Russia), and Mississippi Rivers (USA) at various time points between 2011 and 2018. Samples were analyzed for dissolved black carbon (DBC), dissolved organic carbon (DOC), and stable carbon isotopes. Data are published in Table 1 and as Supplemental Data in Wagner et al., 2019 (doi: 10.1038/s41467-019-13111-7). 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/878750