A stable-carbon-isotope-based constraint of bulk particulate organic carbon dynamics and budgets in the Yellow Sea: Combining field surveys and isotope fractionation modeling

文献类型： 外文期刊

第一作者： Guo, Cong-cong

作者： Guo, Cong-cong;Yang, Shu;Liu, Zi-chen;Luan, Qing-shan;Liu, Qian-qian;Zhai, Wei-dong;Luan, Qing-shan;Liu, Qian-qian

作者机构：

关键词： Organic geochemistry; Stable carbon isotope; Isotope fractionation modelling; Temperate coastal ocean

期刊名称：PROGRESS IN OCEANOGRAPHY （ 影响因子：3.6； 五年影响因子：4.0 ）

ISSN： 0079-6611

年卷期： 2025 年 236 卷

页码：

收录情况： SCI

摘要： The isotopic composition of POC (delta C-13(POC)) serves as a critical tracer for marine carbon dynamics. Its traditional applications usually assume a fixed delta C-13 value for marine phytoplankton (delta C-13(phyto)) of - 20 +/- 1 parts per thousand, overlooking spatiotemporal variabilities in phytoplankton carbon isotope fractionation (epsilon(P)). This study quantifies epsilon(P)-mediated delta C-13(POC) variations in the Yellow Sea - a temperate shelf sea characterized by seasonal stratification, intense diatom blooms, and terrestrial inputs - by coupling isotope fractionation models (passive CO(2)aq diffusion vs. active HCO3- transport) with multi-season delta C-13 measurements of Dissolved Inorganic Carbon (DIC) and delta C-13(POC). During algal bloom periods, delta C-13(POC) values were relatively heavier (-20 +/- 1 parts per thousand), driven by active HCO3- uptake under low CO(2)aq concentrations ([CO(2)aq]). Strong agreement between delta C-13(POC) and modeled delta C-13(phyto) values confirmed compositional similarity between POC and algal biomass, with epsilon P exhibiting significant covariation with [CO(2)aq]. In non-bloom periods, lighter delta C-13(POC) values (from - 26 to - 24 parts per thousand) dominated surface layers, with even more depleted signatures (<-26 parts per thousand) occurred in the Deep Chlorophyll Maximum (DCM) and middle layers. Although detritus inputs caused deviations of delta C-13(POC) from modeled delta C-13(phyto) values, temperature-dependent correlations still revealed epsilon P-related isotopic dynamics in POC. This research underscores the necessity of using environment-specific delta C-13(phyto) values to refine POC budget estimates, reducing flux uncertainties by 20-30 % and minimizing isotopic errors to < 1 parts per thousand across different timescales. This work establishes a framework for incorporating delta C-13(phyto) plasticity into coastal carbon models, resolving long-standing paradoxes of isotopically light POC (<-26 parts per thousand) in marine-dominated systems and advancing high-resolution carbon flux estimates in marginal seas.

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