Hadal trenches (> 6,000 m water depth) have been revealed as hotspots of organic carbon deposition and mineralization. Here, we present the molecular compositions of porewater dissolved organic matter (DOM) at the “Challenger” Deep (Site MT02; 10,954 m water depth) sediments of the Mariana Trench and the adjacent abyssal plain sediments (Site MT04; 5,800 m water depth) using ultra high-resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS). The "Challenger" Deep sediments are characterized by higher abundance of recalcitrant compounds, mainly composed of highly unsaturated compounds (79.7%) and carboxyl-rich alicyclic molecules (57.1%), compared to the abyssal plain sediments (68.3%&51.5%). Principal component analysis suggests that TOC content in the sediments exerts an important control on the molecular characteristics of porewater DOM. It is likely that higher TOC content triggers elevated microbial-mediated organic matter mineralization, thereby forming more refractory organic matter compounds. These results improved the knowledge of the poorly-understood DOM compositions and microbial organic matter degradation in the ultra-deep, extreme ocean environment.

中文翻译：

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“挑战者”号深部沉积物孔隙水中溶解有机物的分子特征


哈达尔海沟 （x3E 6 000 m水深 ） 已被揭示为有机碳沉积和矿化的热点地区。在这里，我们使用超高分辨率傅里叶变换离子回旋共振质谱法 （FT-ICR MS） 展示了马里亚纳海沟的“挑战者”深处（站点 MT02;10,954 米水深）沉积物和相邻的深海平原沉积物（站点 MT04;5,800 米水深）的孔隙水溶解有机物 （DOM） 的分子组成。与深海平原沉积物 （68.3%&51.5%） 相比，“挑战者”号深部沉积物的特点是顽固化合物丰度较高，主要由高度不饱和化合物 （79.7%） 和富含羧基的脂环族分子 （57.1%） 组成。主成分分析表明，沉积物中 TOC 含量对孔隙水 DOM 的分子特性起着重要控制作用。较高的 TOC 含量可能会触发微生物介导的有机物矿化升高，从而形成更多难降解的有机物化合物。这些结果提高了对超深、极端海洋环境中知之甚少的 DOM 组成和微生物有机物降解的认识。