Authigenic metastable iron sulfide minerals preserve microbial organic carbon in anoxic environments
Authigenic metastable iron sulfide minerals preserve microbial organic carbon in anoxic environments
复制标题
DOI：
10.1016/j.chemgeo.2019.119343
复制
发表时间：
2019-12
期刊：
影响因子：
3.9
通讯作者：
A. Picard;A. Gartman;Julie Cosmidis;M. Obst;C. Vidoudez;D. Clarke;P. Girguis
中科院分区：
文献类型：
--
作者：
A. Picard;A. Gartman;Julie Cosmidis;M. Obst;C. Vidoudez;D. Clarke;P. Girguis
沉积环境中有机碳（OC）的埋藏促进了长期的碳固存，这使得大气中的氧气得以释放。陆源矿物与OC在海底运输和沉积过程中形成的有机-矿物相互作用增强了OC的保存。在这里，我们提出了一种在缺氧条件下耦合保存不稳定OC和亚稳硫化铁矿物的自生机制。硫酸盐还原微生物（SRM）在缺氧环境中普遍存在，并在海洋沉积物中产生大部分游离硫化物，导致原位硫化铁矿物的形成。利用高空间分辨率显微镜、光谱学和光谱显微镜，我们发现在SRM存在下沉淀的硫化铁生物矿物结合并吸附有机分子，导致形成稳定的有机矿物聚集体，可以在缺氧环境中持续数年。碳酸盐/硫化铁组合由亚稳硫化铁矿物相麦氏铁矿和/或灰长岩组成，以及来自微生物生物量或SRM在细胞外释放的有机分子的不稳定有机化合物。总之，这些结果强调了一组主要的缺氧微生物在OC保存中所起的作用，并说明了由此产生的自生亚稳硫化铁矿物mackinawite和灰长铁矿在保护不稳定有机分子免受时间降解方面的价值。
The burial of organic carbon (OC) in sedimentary environments promotes long-term carbon sequestration, which allows the release of oxygen in the atmosphere. Organo-mineral interactions that form between terrigenous minerals and OC during transport to and deposition on the seabed enhance OC preservation. Here, we propose an authigenic mechanism for the coupled preservation of labile OC and metastable iron sulfide minerals under anoxic conditions. Sulfate-reducing microorganisms (SRM) are ubiquitous in anoxic environments and produce the majority of free sulfide in marine sediments, leading to the formation of iron sulfide mineralsin situ. Using high spatial resolution microscopy, spectroscopy and spectro-microscopy, we show that iron sulfide biominerals precipitated in the presence of SRM incorporate and adsorb organic molecules, leading to the formation of stable organo-mineral aggregates that could persist for years in anoxic environments. OC/iron sulfide assemblages consist of the metastable iron sulfide mineral phases mackinawite and/or greigite, along with labile organic compounds derived from microbial biomass or from organic molecules released extracellularly by SRM. Together these results underscore the role that a major group of anoxic microbes play in OC preservation and illustrate the value of the resulting authigenic metastable iron sulfide minerals mackinawite and greigite in protecting labile organic molecules from degradation over time.