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Preprints
https://doi.org/10.5194/egusphere-2024-3467
https://doi.org/10.5194/egusphere-2024-3467
05 Dec 2024
 | 05 Dec 2024

Biogeochemical Layering and Transformation of Particulate Organic Carbon in the Tropical Northwestern Pacific Ocean Inferred from δ13C

Detong Tian, Xuegang Li, Jinming Song, Jun Ma, Huamao Yuan, and Liqin Duan

Abstract. 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), δ13C-POC, and δ13C-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, 300–1,000 m), and the stable layer (SL, 1,000–2,000 m). From the top to the bottom of the RSDL, δ13C-POC decreased by an average of 2.23 ‰, while the carbon-to-nitrogen ratios (C:N) increased by an average of 2.3:1, indicating the selective degradation of POC. In the NDL, δ13C-POC and δ13C-DIC exhibited a significant negative correlation (r = 0.43, p < 0.05), indicating a net transformation of POC to DIC. In the SL, POC proved to be resistant to degradation, with POC exhibiting the highest C:N (15:1 on average) and the lowest δ13C-POC (average -27.71 ‰).

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Particulate organic carbon plays a vital role in the ocean carbon cycle, yet its transformation...
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