Abstract. Marine sedimentation rate and bottom-water O₂ concentration control the remineralization/sequestration of organic carbon across continental margins; but whether/how they shape microbiome architecture (the ultimate effector of all biogeochemical phenomena), across shelf/slope sediments, is unknown. Here we reveal distinct microbiome structures and functions, amidst comparable pore fluid chemistries, along 300 cm sediment horizons underlying the seasonal (shallow coastal) and perennial (deep sea) oxygen minimum zones (OMZs) of the Arabian Sea, situated across the western-Indian margin (water-depths: 31 m and, 530 and 580 m, respectively). The sedimentary geomicrobiology was elucidated by analyzing metagenomes, metatranscriptomes, and enrichment cultures, and also sedimentation rates measured by radiocarbon and lead excess (²¹⁰Pb_xs); the findings were then evaluated in the light of the other geochemical data available for the cores investigated. Along the perennial- and seasonal-OMZ sediment cores, microbial communities were dominated by Gammaproteobacteria and Alphaproteobacteria, and Euryarchaeota and Firmicutes, respectively. As a perennial-OMZ signature, a cryptic methane production-consumption cycle was found to operate near the sediment-surface (within the sulfate reduction zone); overall diversity, as well as the relative abundances of simple-fatty-acids-requiring anaerobes (methanogens, anaerobic methane-oxidizers, sulfate-reducers and acetogens), peaked in the topmost sediment-layer and then declined via synchronized fluctuations until the sulfate-methane transition zone was reached. The entire microbiome profile was reverse in the seasonal-OMZ sediment horizon. In the perennial-OMZ sediments organic carbon deposited was higher in concentration and marine components-rich, so it potentially degraded readily to simple fatty acids; lower sedimentation rate afforded higher O₂ exposure time for organic matter degradation despite perennial hypoxia in the bottom-water; thus, the resultant abundance of reduced carbon substrates sustained multiple inter-competing microbial processes in the upper sediment-layers. Remarkably, the whole geomicrobial scenario was opposite in the sediments of the seasonal/shallow-water OMZ. Our findings create a microbiological baseline for understanding carbon-sulfur cycling across distinct marine depositional settings and water-column oxygenation regimes.

中文翻译：

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沉积速率和有机质动力学塑造了整个大陆边缘的微生物群落

摘要。海洋沉积速率和底水O ₂浓度控制大陆边缘的有机碳的再矿化/隔离；但是，它们是否/如何在整个架子/斜坡沉积物上塑造微生物组结构（所有生物地球化学现象的最终影响者）。在这里，我们揭示了在可比的孔隙流体化学作用下，沿着横跨印度西部的阿拉伯海的季节性（浅海沿海）和多年生（深海）最小含氧量区域（OMZ）下方300厘米的沉积层，具有独特的微生物组结构和功能。边缘（水深分别为31 m和530和580 m）。通过分析元基因组，元转录组和富集培养，以及通过放射性碳和铅超标（²¹⁰ Pb _xs）测量的沉积速率，阐明了沉积地球微生物学。）; 然后根据可用于研究岩心的其他地球化学数据对发现进行评估。沿常年和季节性OMZ沉积物核心，微生物群落主要由γ-变形杆菌和α-变形杆菌，Euryarchaeota和Firmicutes组成。， 分别。作为多年生OMZ的特征，人们发现在沉积物表面附近（硫酸盐还原带内）有一个秘密的甲烷生产-消耗循环。总体多样性以及需要简单脂肪酸的厌氧菌（甲烷，厌氧甲烷氧化剂，硫酸盐还原剂和产乙酸菌）的相对丰度在最顶层的沉积层达到峰值，然后通过同步波动而下降，直到硫酸盐到达甲烷过渡区。整个微生物组概况在季节性OMZ沉积层范围内是相反的。在多年生OMZ沉积物中，沉积的有机碳浓度较高且海洋成分丰富，因此可能容易降解为简单脂肪酸。较低的沉降速率提供较高的O ₂尽管底水中常年缺氧，但有机物降解的暴露时间；因此，所产生的大量还原碳底物在上部沉积层中维持了多个相互竞争的微生物过程。值得注意的是，季节性/浅水OMZ的沉积物中，整个微生物环境是相反的。我们的发现为理解跨不同海洋沉积环境和水柱充氧制度的碳硫循环创造了微生物学基线。