The gas hydrate-bearing structure—mud volcano Kedr-1 (Lake Baikal, southern basin)—is located near the coal-bearing sediments of the Tankhoy formation of Oligocene–Miocene age and can be an ideal source of gas-saturated fluid. A significant amount of siderite minerals (FeCO₃) were collected from sediments at depths ranging from 0.5 to 327 cm below the lake floor (cmblf). An important feature of these carbonate minerals is the extremely strong enrichment in the heavy ¹³C isotope, reaching values of +33.3‰ VPDB. The δ¹³C of the siderite minerals, as well as their morphology and elemental composition, and the δ¹³C_DIC of the co-existing pore water, differed across layers of the core, which implies at least two generations of siderite formation. Here, we leverage mineralogical and geochemical data with 16S rRNA data from the microbial communities in sediments surrounding layers containing siderite minerals. Statistical data reveal the formation of three clusters of microbial communities based on taxonomical composition, key taxa among bacteria and archaea, and environmental parameters. Diversity and richness estimators decrease with sediment depth, with several similar prevailing clades located at the bottom of the core. Most of the taxa in the deep sediments could be associated with putative metabolisms involving organotrophic fermentation (Bathyarchaeia, Caldatribacteriota, and Chloroflexota). Various groups of methanogens (Methanoregulaceae, Methanosaetaceae, and Methanomassiliicoccales) and methanotrophic (Methanoperedenaceae) archaea are present in the sediment at variable relative abundances throughout the sampled depth. Based on the physicochemical characteristics of the sediment, carbon isotope analysis of carbonate minerals and DIC, and phylogenetic analysis of individual taxa and their metabolic potential, we present several models for subsurface siderite precipitation in Lake Baikal sediments.

中文翻译：

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贝加尔湖 Kedr-1 泥火山周围沉积物中的微生物多样性和自生菱铁矿介导

含天然气水合物构造——泥火山Kedr-1（贝加尔湖，盆地南部）——位于渐新世-中新世Tankhoy组的含煤沉积物附近，可以成为天然气饱和流体的理想来源。从湖底以下 0.5 至 327 厘米 (cmblf) 深度的沉积物中收集到大量菱铁矿矿物 (FeCO _{3 )。}这些碳酸盐矿物的一个重要特征是重13C^同位素极强富集，达到+33.3‰VPDB值。菱铁矿矿物的δ ¹³ C及其形态和元素组成，以及共存孔隙水的δ ¹³ C _DIC在岩心各层之间有所不同，这意味着至少有两代菱铁矿形成。在这里，我们利用矿物学和地球化学数据以及来自含有菱铁矿矿物的周围沉积物层中微生物群落的 16S rRNA 数据。统计数据揭示了基于分类组成、细菌和古细菌之间的关键类群以及环境参数的三个微生物群落的形成。多样性和丰富度估计量随着沉积物深度的增加而减少，几个相似的主要分支位于岩心底部。深层沉积物中的大多数类群可能与涉及有机营养发酵的推定代谢有关（Bathyarchaeia、Caldatribacteriota 和 Chloroflexota）。在整个采样深度的沉积物中，各种产甲烷菌（Methanoregulaceae、Methanosaetaceae和Methanomassiliicoccales）和甲烷营养菌（Methanoperedenaceae）古菌的相对丰度各不相同。基于沉积物的物理化学特征、碳酸盐矿物和 DIC 的碳同位素分析以及单个类群及其代谢潜力的系统发育分析，我们提出了贝加尔湖沉积物中地下菱铁矿沉淀的几种模型。