The microbial carbon pump (MCP) concept regroups different processes that contribute to the formation of refractory dissolved organic matter (DOM) from labile substrates. In this study, long-term (1 yr) incubation experiments in fresh- and sea-waters were done with glucose as the only source of carbon for microorganisms. Bulk carbon, glucose and amino acid enantiomers analyses confirmed that glucose was transformed into microbial biomass and complex non-labile DOM. Dissolved organic carbon concentrations decreased during the first four months and then remained constant at ~20% of the initial level. After one year, the microbial DOM and DOM from natural waters were concentrated by evaporation and a low volume solid-phase extraction (SPE) that resulted in a very high (70 to 85%) extraction efficiency. These SPE-DOM samples were characterized by size-exclusion chromatography (HPLC-SEC) coupled with Fourier transform infrared spectroscopy (FTIR). These are the first HPLC-SEC-FTIR analyses of microbial DOM and of such high proportions of natural DOM. Results revealed that microbial DOM showed all the FTIR absorption bands seen in the DOM from natural waters. However, amino acids, carbohydrates, and aliphatic CH were more abundant in the microbial DOM, whereas phenols and esters were more visible in DOM from natural waters. It was difficult to identify consistent (in all samples) compositional trends according to molecular weight (MW). Cluster analyses showed that 72% of the variability in the relative absorbance for all the bands was explained by the origin and the type of the DOM extracts. The microbial DOM from freshwater had the most unique bulk composition while the microbial DOM from seawater was more similar to the DOM from natural waters. The DOM from natural fresh- and sea-waters exhibited the most similar composition when all the bands and MW are considered. The lack of consistent trends in the composition of the samples having the same origin (e.g., the two microbial DOM or the two freshwater DOM) shows the high heterogeneity and complexity of DOM, including the microbial non-labile DOM produced by the MCP. This suggests that the MCP contributes to the heterogeneity and complexity of the DOM found in natural waters.

微生物碳泵（MCP）概念重新组合了不同的过程，这些过程有助于从不稳定的基质中形成难溶的溶解有机物（DOM）。在这项研究中，在淡水和海水中进行了长期（1年）温育实验，葡萄糖是微生物唯一的碳源。大量碳，葡萄糖和氨基酸对映体的分析证实，葡萄糖已转化为微生物生物量和复杂的非不稳定DOM。在头四个月中，溶解的有机碳浓度下降，然后保持在初始水平的约20％。一年后，通过蒸发和小体积固相萃取（SPE）浓缩了自然水中的微生物DOM和DOM，这导致了非常高的萃取效率（70％至85％）。这些SPE-DOM样品通过尺寸排阻色谱（HPLC-SEC）与傅立叶变换红外光谱（FTIR）进行了表征。这是对微生物DOM和如此高比例的天然DOM的首次HPLC-SEC-FTIR分析。结果表明，微生物DOM显示了在DOM中从自然水域看到的所有FTIR吸收带。但是，微生物DOM中的氨基酸，碳水化合物和脂肪族CH含量较高，而天然水中DOM中的酚和酯含量更高。很难根据分子量（MW）来确定一致的（在所有样品中）组成趋势。聚类分析表明，所有谱带的相对吸光度的72％变异是由DOM提取物的来源和类型解释的。来自淡水的微生物DOM具有最独特的体积组成，而来自海水的微生物DOM与天然水的DOM更相似。当考虑所有波段和MW时，天然淡水和海水的DOM表现出最相似的组成。具有相同来源的样品（例如，两种微生物DOM或两种淡水DOM）的成分组成缺乏一致的趋势，表明DOM的高度异质性和复杂性，包括MCP产生的微生物不稳定的DOM。这表明，MCP有助于自然水中发现的DOM的异质性和复杂性。当考虑所有波段和MW时，天然淡水和海水的DOM表现出最相似的组成。具有相同来源的样品（例如，两种微生物DOM或两种淡水DOM）的成分组成缺乏一致的趋势，表明DOM的高度异质性和复杂性，包括MCP产生的微生物不稳定的DOM。这表明，MCP有助于自然水中发现的DOM的异质性和复杂性。当考虑所有波段和MW时，天然淡水和海水的DOM表现出最相似的组成。具有相同来源的样品（例如，两种微生物DOM或两种淡水DOM）的成分组成缺乏一致的趋势，表明DOM的高度异质性和复杂性，包括MCP产生的微生物不稳定的DOM。这表明，MCP有助于自然水中发现的DOM的异质性和复杂性。