This work presents a multi-analytical approach for the characterization of marine dissolved organic matter (DOM). The determination of marine dissolved organic carbon (DOC) was performed by size exclusion chromatography (SEC) and validated using a certified reference material (CRM) as well as through an intercomparison exercise. Multi-detection SEC, fluorescence and electrochemical methods were used in order to describe the size distribution spectra, the composition and chemical properties of marine DOM, in the (ultra)oligotrophic West Tropical South Pacific Ocean (WTSP). In this work, we defined the state of degradation of DOC in the different size fractions, operationally defined by SEC. We estimated that on average 62% of DOC was of humic nature (0.5–10 kDa), of which ~9% was able to complex trace elements, such as iron (Fe). Our results tend to support that non-refractory DOC is of high molecular weight (HMW), nitrogen (N)-rich, aliphatic, and has a weak fluorescence quantum yield and an enhanced binding capacity for Fe. The ageing of marine DOM occurring within mesopelagic waters is mainly driven by microbial respiration and alters these chemical properties. Although our results are in agreement with a paradigm describing oceanic DOM biogeochemistry known as the size-reactivity continuum, 3 μmolC L⁻¹ of very HMW (> 10 kDa) were still observed in a water mass mainly composed of Pacific Deep Waters. This persistence could be explained by a significant content (5%) of aromatic carbon that may protect HMW DOM from long term biodegradation.

这项工作提出了一种用于表征海洋溶解有机物 (DOM) 的多分析方法。海洋溶解有机碳 (DOC) 的测定通过尺寸排阻色谱 (SEC) 进行，并使用经认证的参考材料 (CRM) 以及通过比对进行验证。使用多检测 SEC、荧光和电化学方法来描述（超）贫营养的西热带南太平洋 (WTSP) 中海洋 DOM 的尺寸分布光谱、组成和化学性质。在这项工作中，我们定义了由 SEC 在操作上定义的不同尺寸部分中 DOC 的降解状态。我们估计平均 62% 的 DOC 是腐殖质（0.5-10 kDa），其中约 9% 能够复合微量元素，如铁 (Fe)。我们的结果倾向于支持非难熔 DOC 具有高分子量 (HMW)、富含氮 (N)、脂肪族，并且具有弱的荧光量子产率和增强的 Fe 结合能力。发生在中层海域的海洋 DOM 的老化主要是由微生物呼吸驱动的，并改变了这些化学性质。虽然我们的结果与描述海洋 DOM 生物地球化学的范式一致，称为尺寸反应连续体，3 μmolC L在主要由太平洋深水组成的水团中仍然观察到^-1的高分子量 (> 10 kDa)。这种持久性可以通过大量 (5%) 的芳香碳来解释，这些碳可以保护 HMW DOM 免受长期生物降解。