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<p>Marine nitrogen cycle, shaped by nitrogen input and loss processes, regulates ocean productivity and leaves a distinct imprint on the ratio of stable nitrogen isotopes, δ<sup>15</sup>N. However, quantifying spatial patterns and centennial-scale variations in marine nitrogen cycling through δ<sup>15</sup>N fingerprints remains poorly constrained. Here, we present a global database of δ<sup>15</sup>N in marine sediments, comprising over 8400 seafloor samples, and create 148 time series from sediment cores spanning the past century. Our findings reveal that bulk δ<sup>15</sup>N in global marine sediments predominantly records organic matter, despite the non-negligible role of inorganic nitrogen. A widespread centennial δ<sup>15</sup>N increase, averaging 1.3‰ (interquartile range: 0.6<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(-\)</EquationSource> <EquationSource Format="MATHML"><math> <mo>−</mo> </math></EquationSource> </InlineEquation>3.3‰) per 100 years, coinciding with total nitrogen enrichment, indicates external nitrogen inputs, productivity, and accelerated denitrification across global coastal oceans. However, in river-influenced continental margins, terrestrial sedimentary processes can obscure the <sup>15</sup>N-enriched signal, as riverine export of <sup>15</sup>N-depleted refractory organic matter likely lowers sedimentary δ<sup>15</sup>N.</p>

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Global patterns and drivers of nitrogen isotope signal in modern marine sediments

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年11月25日

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  • Xueshi Sun,
  • Dejiang Fan,
  • Limin Hu,
  • Houjie Wang

摘要

Marine nitrogen cycle, shaped by nitrogen input and loss processes, regulates ocean productivity and leaves a distinct imprint on the ratio of stable nitrogen isotopes, δ15N. However, quantifying spatial patterns and centennial-scale variations in marine nitrogen cycling through δ15N fingerprints remains poorly constrained. Here, we present a global database of δ15N in marine sediments, comprising over 8400 seafloor samples, and create 148 time series from sediment cores spanning the past century. Our findings reveal that bulk δ15N in global marine sediments predominantly records organic matter, despite the non-negligible role of inorganic nitrogen. A widespread centennial δ15N increase, averaging 1.3‰ (interquartile range: 0.6 \(-\) − 3.3‰) per 100 years, coinciding with total nitrogen enrichment, indicates external nitrogen inputs, productivity, and accelerated denitrification across global coastal oceans. However, in river-influenced continental margins, terrestrial sedimentary processes can obscure the 15N-enriched signal, as riverine export of 15N-depleted refractory organic matter likely lowers sedimentary δ15N.