新不列颠海沟碳酸钙沉积物溶解有机质光学属性和分子特征

Optical and molecular properties of dissolved organic matter in carbonate sediments of the New Britain Trench

水深超过6000 m的深渊海沟是海洋中的极端环境,频发的事件沉积使海沟成为深海有机质埋藏的热点区域。为深入认识深渊有机质的降解机制,本研究以有机质降解的中间产物——溶解有机质(DOM)为研究对象,利用光谱(EEMs)和傅里叶变换回旋共振质谱(FT-ICR MS)分析了新不列颠海沟轴部正常泥质沉积和碳酸钙异常沉积层中DOM的性质。结果表明,无论是正常沉积还是异常沉积层,DOM均以类腐殖质为主,其分子构成主要为C、H、O三种元素。此外,对化合物组成、木质素指数等的分析发现,异常沉积层中不仅包含较多陆源植物降解产物,而且还包含有丰富的多肽等生物活性物质,指示事件沉积不仅埋藏了惰性的陆源有机物,而且还带来了活性的海源有机质,从而促进了碳酸钙沉积层中的生命活动。本研究揭示了深渊事件沉积对DOM性质的影响,也为理解深渊生命过程提供了新思路。

Hadal trenches with water depth exceeding 6000 m,are extreme ocean environment where frequent event deposition has made them hotspots for the burial of deep-sea organic matter.This study examined dissolved organic matter(DOM),an intermediate product of organic matter degradation,to understand the degradation mechanism in trenches.Using fluorescence spectroscopy and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry(FT-ICR MS),we analyzed DOM properties of normal muddy sediments and carbonate anomalous sedimentary layers in the New Britain Trench axis.The results showed that DOM in the two types of sediments is mainly composed of humic-like substances,of which carbon,hydrogen and oxygen are main elemental components.In addition,the composition and lignin index showed that the anomalous sedimentary layer contains not only terrestrial plant degradation products but also abundant peptides and other labile substances,indicating that the event deposition buried refractory terrestrial organic matter and brought reactive marine-derived organic matter.This would stimulate life processes within carbonate sedimentary layers.This study highlights the impact of event deposition on DOM and offers new insights into life processes in the hadal zone.