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<p>Understanding the dynamics of marine dissolved organic carbon (DOC) is essential for predicting its role in carbon cycling and its response to climate change. Here, we unveil molecular transformations of marine chromophoric dissolved organic matter (CDOM) across the global ocean using Ultraviolet-visible spectroscopy. Significant variability in CDOM composition within the epi- and mesopelagic layers ( &lt; 1000 m) correlates with physicochemical parameters, driven by irradiation, primary production, biological activity, transport, and riverine inputs. In the bathypelagic layer (1000–5000 m), up to 18.2% of highly conjugated molecules transform into low-molecular-weight CDOM, despite stable DOC concentrations. This dynamic process sustains biomass production and respiration in deep ocean, contributing a carbon flux of 3–24 Pg C yr<sup>−1</sup>—up to an order of magnitude more than the fast-sinking particulate organic carbon flux. Our findings offer insights into the molecular transformation of deep-ocean DOM and underscore the need to reassess the bathypelagic DOC pool’s role in the global carbon cycle.</p>

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Unveiling ongoing biogeochemical dynamics of CDOM from surface to deep ocean

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2025年6月4日

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  • Shansheng Mo,
  • Zhongli Liu,
  • Yuanhao Hao,
  • Norbert Hertkorn,
  • Hanzhe Wang,
  • Chenyang Zhang,
  • Gregory Korshin,
  • Jinren Ni,
  • Mingquan Yan

摘要

Understanding the dynamics of marine dissolved organic carbon (DOC) is essential for predicting its role in carbon cycling and its response to climate change. Here, we unveil molecular transformations of marine chromophoric dissolved organic matter (CDOM) across the global ocean using Ultraviolet-visible spectroscopy. Significant variability in CDOM composition within the epi- and mesopelagic layers ( < 1000 m) correlates with physicochemical parameters, driven by irradiation, primary production, biological activity, transport, and riverine inputs. In the bathypelagic layer (1000–5000 m), up to 18.2% of highly conjugated molecules transform into low-molecular-weight CDOM, despite stable DOC concentrations. This dynamic process sustains biomass production and respiration in deep ocean, contributing a carbon flux of 3–24 Pg C yr−1—up to an order of magnitude more than the fast-sinking particulate organic carbon flux. Our findings offer insights into the molecular transformation of deep-ocean DOM and underscore the need to reassess the bathypelagic DOC pool’s role in the global carbon cycle.