Most studies on the genesis of polymetallic nodules suggested that nodules in the South China Sea (SCS) are hydrogenetic; however, the complexity and the heterogeneity in hydrology and geochemistry of the SCS might cause different processes of nodule formation, impacting their application and economic value. Microbial-mediated ferromanganese deposition is an important process in nodule formation, but the related microbial potentials are still unclear in the SCS. In this study, we sampled in three typical regions (A, B, and C) of the SCS enriched with polymetallic nodules. Firstly, we investigated environmental and microbial characteristics of the water columns to determine the heterogeneity of upper seawater that directly influenced deep-sea environments. Then, microbial compositions and structures in sediment cores, overlying waters, and nodules (inside and outside) collected within the same region were analyzed for inferring features of nodule environments. Microbial interactions between nodules and surrounding environments were estimated with collinear network analysis. The microbial evidence indicated that geochemical characteristics in deep sea of the SCS that were key to the polymetallic nodule formation were severely affected by organic matter flux from upper water column. The sediment in region A was sub-oxic due to the large input of terrigenous and phytoplankton-derived organic matter, potentially enhancing the overflow of reduced metals from the porewater. The intense microbial interaction between nodules and surface sediment reinforced the origin of metals for the ferromanganese deposition from the sediment (diagenetic type). Contrarily, the sediments in regions B and C were relatively rich in oxygen, and metal ions could be majorly supplied from seawater (hydrogenetic type). The large discrepancy in microbial communities between nodule inside and remaining samples suggested that nodules experienced a long-term formation process, consistent with the feature of hydrogenetic nodules. Overall, distributions and interactions of microbial communities in nodules and surrounding environments significantly contributed to the nodule formation in the SCS by manipulating biogeochemical processes that eventually determined the source and the fate of metal ions.

中文翻译：

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异质海洋环境使南海微生物驱动的多金属结核形成多样化


大多数关于多金属结核成因的研究表明，南海 （SCS） 的结核是氢化的;然而，南海水文和地球化学的复杂性和非均质性可能导致不同的结核形成过程，从而影响其应用和经济价值。微生物介导的锰铁沉积是结节形成的重要过程，但 SCS 中相关的微生物潜力仍不清楚。在这项研究中，我们在富含多金属根瘤的 SCS 的三个典型区域 （A、B 和 C） 中取样。首先，我们研究了水柱的环境和微生物特征，以确定直接影响深海环境的上层海水的异质性。然后，分析在同一区域内收集的沉积物岩芯、上覆水域和结核（内部和外部）中的微生物组成和结构，以推断结核环境的特征。通过共线网络分析估计根瘤与周围环境之间的微生物相互作用。微生物证据表明，南海深海的地球化学特征是多金属结核形成的关键，受到上层水柱有机物通量的严重影响。由于陆源和浮游植物衍生的有机物的大量输入，区域 A 的沉积物是亚氧沉积物，可能增强了孔隙水中还原金属的溢出。结核和表层沉积物之间强烈的微生物相互作用加强了沉积物中锰铁沉积的金属来源（成岩类型）。 相反，B 区和 C 区的沉积物含氧量相对较丰富，金属离子主要来自海水（水生型）。内部根瘤与剩余样品之间微生物群落的巨大差异表明，根瘤经历了一个长期的形成过程，这与水生根瘤的特征一致。总体而言，微生物群落在根瘤和周围环境中的分布和相互作用通过操纵最终决定金属离子来源和命运的生物地球化学过程，对 SCS 中根瘤的形成做出了重大贡献。