Biogeochemical layering and transformation of particulate organic carbon in the Tropical Northwestern Pacific Ocean inferred from <i>δ</i><sup>13</sup>C
<p>Particulate organic carbon (POC) serves as the main carrier of the biological pump and determines its transmission efficiency, yet the transformation processes of POC remain incompletely understood. This study reports the vertical distribution of POC, dissolved inorganic carbon (DIC), <s...
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| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-07-01
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| Series: | Ocean Science |
| Online Access: | https://os.copernicus.org/articles/21/1627/2025/os-21-1627-2025.pdf |
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| Summary: | <p>Particulate organic carbon (POC) serves as the main carrier of the biological pump and determines its transmission efficiency, yet the transformation processes of POC remain incompletely understood. This study reports the vertical distribution of POC, dissolved inorganic carbon (DIC), <span class="inline-formula"><i>δ</i><sup>13</sup></span>C-POC, and <span class="inline-formula"><i>δ</i><sup>13</sup></span>C-DIC in the tropical Northwestern Pacific Ocean (TNPO). The research identified three distinct biogeochemical layers governing POC transformation: the POC rapid synthesis-degradation layer (RSDL, 0–300 m), the net degradation layer (NDL, 300–1000 m), and the stable layer (SL, 1000–2000 m). From the top to the bottom of the RSDL, <span class="inline-formula"><i>δ</i><sup>13</sup></span>C-POC values decreased by an average of 2.23 ‰, while the carbon-to-nitrogen (<span class="inline-formula">C:N</span>) ratios increased by an average of <span class="inline-formula">2.3:1</span>, indicating the selective degradation of POC. In the NDL, <span class="inline-formula"><i>δ</i><sup>13</sup></span>C-POC and <span class="inline-formula"><i>δ</i><sup>13</sup></span>C-DIC exhibited a significant negative correlation (<span class="inline-formula"><i>r</i>=0.43</span>, <span class="inline-formula"><i>p</i><0.05</span>), indicating a net transformation of POC to DIC. In the SL, POC proved to be resistant to degradation, with POC exhibiting the highest <span class="inline-formula">C:N</span> (<span class="inline-formula">15:1</span> on average) and the lowest <span class="inline-formula"><i>δ</i><sup>13</sup></span>C-POC values (average <span class="inline-formula">−</span>27.71 ‰).</p> |
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| ISSN: | 1812-0784 1812-0792 |