The microbial lipid signature in sediments and chimneys within a back-arc basin hydrothermal system south of the Antarctic Polar Front

IF 2.3 3区 地球科学 Q2 OCEANOGRAPHY
Maria T. Hernández-Sánchez , Laura Hepburn , Michael J. Stock , Douglas P. Connelly , Richard D. Pancost
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引用次数: 0

Abstract

The impact of hydrothermal systems on surrounding sedimentary microbial communities is not well understood and previous work has been limited to high temperature vent sites at slow or ultraslow spreading oceanic centres. To build on the current understanding of hydrothermal systems, we explore for the first time the organic geochemistry of the only known back-arc basin hydrothermal system outside the Pacific Ocean: the East Scotia Ridge (ESR), which belongs to the South Georgia and South Sandwich Islands Marine Protected Area. Lipid biomarkers contained in sediments and hydrothermal sulphides along two hydrothermal vent fields north and south of the ESR, respectively, revealed the impact of hydrothermal activity, including both high temperature and low temperature diffusive venting, on sedimentary microbial communities. In the vent field north of the ESR, elevated ring indices of glycerol dialkyl glycerol tetraethers (GDGTs) and proportions of monoalkyl glycerol tetraethers (GMGTs), and a high ratio of total fatty acids (FAs; free plus polar lipids) to putative phytoplankton biomarkers in sediments suggest that high-temperature hydrothermalism has a local impact on surrounding sediments through the input of plume dwelling archaea and bacteria. This impact seems to be restricted to the periphery of the vent source, in agreement with the limited dataset available from slow or ultraslow spreading centres. Likewise, elevated FA to phytoplankton biomarker ratios within a diffusive hydrothermal field south of the ESR suggest an additional input of bacterial biomass relative to background sediments. Our results indicate that low temperature diffusive venting might have a higher impact than previously thought, being locally important in supporting the food chain in deep-sea environments. The distribution of tetraether lipids suggests that a higher proportion of thermophilic archaea thrive in the interior of sulphide chimneys, whereas total FA concentrations and distributions suggest that most bacteria inhabit the exterior chimney layers, where temperature is cooler than the innermost layer in contact with the hydrothermal fluid. Furthermore, differences in total FA concentrations suggest that chimney wall thickness is a control on bacterial abundance through the availability of a higher or lower diversity (and volume) of microhabitats. Our results also indicate that bacteria adapt to increasing temperatures by decreasing their degree of unsaturation. By comparison to GDGT data from other settings, it seems that overall ring indices in hydrothermal deposits are governed by growth temperature, although they might also reflect ecological factors. Our results suggest that hydrothermalism shapes microbial communities within chimneys and surrounding sediments following broadly similar patterns regardless of the type of spreading centre they are located at.

南极极地前沿以南的后弧盆地热液系统沉积物和烟囱中的微生物脂质特征
热液系统对周围沉积微生物群落的影响尚不十分清楚,以往的工作仅限于慢扩张或超慢速扩张海洋中心的高温喷口地点。在目前对热液系统了解的基础上,我们首次探索了太平洋以外唯一已知的弧后盆地热液系统的有机地球化学:东斯科舍海脊(ESR),该海脊属于南乔治亚和南桑威奇群岛海洋保护区。东斯科舍海脊北部和南部两个热液喷口区沉积物和热液硫化物中的脂质生物标志物分别揭示了热液活动(包括高温和低温扩散喷口)对沉积微生物群落的影响。在 ESR 北部的喷口区,沉积物中甘油二烷基甘油四醚(GDGTs)环指数和单烷基甘油四醚(GMGTs)比例升高,总脂肪酸(FAs;游离加极性脂质)与推定浮游植物生物标志物的比例较高,这表明高温热液通过羽流栖息古细菌和细菌的输入对周围沉积物产生了局部影响。这种影响似乎仅限于喷口源的周边地区,这与从慢速或超慢速扩张中心获得的有限数据集是一致的。同样,在 ESR 南部的扩散热液场中,FA 与浮游植物生物标志物的比率升高,表明相对于背景沉积物,细菌生物量的额外输入。我们的研究结果表明,低温扩散性喷口的影响可能比以前认为的要大,在支持深海环境食物链方面具有局部重要性。四醚脂的分布表明,嗜热古细菌在硫化物烟囱内部生长的比例较高,而总脂肪酸的浓度和分布表明,大多数细菌栖息在烟囱外层,那里的温度低于与热液接触的最内层。此外,总脂肪酸浓度的差异表明,烟囱壁的厚度可以通过提供较高或较低的微生境多样性(和体积)来控制细菌的数量。我们的研究结果还表明,细菌通过降低不饱和程度来适应温度的升高。与其他环境中的 GDGT 数据相比,热液沉积中的总体环指数似乎受生长温度的影响,尽管它们也可能反映生态因素。我们的研究结果表明,热液作用塑造了烟囱和周围沉积物中的微生物群落,无论它们位于哪种类型的扩张中心,其模式都大致相同。
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来源期刊
CiteScore
4.60
自引率
4.20%
发文量
144
审稿时长
18.3 weeks
期刊介绍: Deep-Sea Research Part I: Oceanographic Research Papers is devoted to the publication of the results of original scientific research, including theoretical work of evident oceanographic applicability; and the solution of instrumental or methodological problems with evidence of successful use. The journal is distinguished by its interdisciplinary nature and its breadth, covering the geological, physical, chemical and biological aspects of the ocean and its boundaries with the sea floor and the atmosphere. In addition to regular "Research Papers" and "Instruments and Methods" papers, briefer communications may be published as "Notes". Supplemental matter, such as extensive data tables or graphs and multimedia content, may be published as electronic appendices.
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