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Photochemical bleaching of fluorescent dissolved organic matter in the subtropical North Pacific Ocean

  • Omori Yuko
    Graduate School of Life and Environmental Sciences, University of Tsukuba
  • Hama Takeo
    Graduate School of Life and Environmental Sciences, University of Tsukuba
  • Ishii Masao
    Geochemical Research Department, Meteorological Research Institute

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Abstract

We examined the molecular weight distribution of the fluorescence intensity of FDOMM and dissolved organic carbon (DOC) concentrations in the subtropical western North Pacific, in order to characterize photoreactivity of FDOMM and understand the relationship between FDOMM and DOC pool. DOC concentrations in a hydrophobic fraction (O-DOC),which is extracted by solid phase extraction, accounted for 34 and 38% of bulk organic carbon in the surface and deep layer. FDOMM in a hydrophobic fraction (O-FDOMM) accounted for 78 and 37% of FDOMM in the surface and 1000-m depth seawater, respectively. Molecular weight distribution of O-FDOMM and O-DOC showed that ratio of the fluorescence intensity to the DOC concentration of each MW fraction increased with depth. This suggests that the contribution of O-FDOMM to O-DOC in the deeper seawater is higher than that in the surface layer. When deep-seawater samples were irradiated by natural sunlight for 5 days, the fluorescence intensity of O-FDOMM decreased to almost half and its molecular weight shifted to lower one, whereas the O-DOC concentration did not decrease. It implies that a part of O-FDOMM remains as photobleached FDOMM (no-fluorescence DOM) after photobleaching.

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Details

  • CRID
    1390282679530208000
  • NII Article ID
    130005067939
  • NII Book ID
    AA00654975
  • DOI
    10.2343/geochemj.2.0343
  • ISSN
    18805973
    00167002
  • NDL BIB ID
    026326574
  • Text Lang
    en
  • Data Source
    • JaLC
    • NDL
    • Crossref
    • CiNii Articles
  • Abstract License Flag
    Disallowed

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