Bacterial and eukaryotic intact polar lipids point to in situ production as a key source of labile organic matter in hadal surface sediment of the Atacama Trench
Bacterial and eukaryotic intact polar lipids point to in situ production as a key source of labile organic matter in hadal surface sediment of the Atacama Trench
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DOI：
10.5194/bg-19-1395-2022
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发表时间：
2022-03
期刊：
影响因子：
4.9
通讯作者：
E. Flores;Sebastian I. Cantarero;P. Ruiz-Fernández;N. Dildar;M. Zabel;O. Ulloa;J. Sepúlveda
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文献类型：
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作者：
E. Flores;Sebastian I. Cantarero;P. Ruiz-Fernández;N. Dildar;M. Zabel;O. Ulloa;J. Sepúlveda
摘要。相对于周围的深海海底，在超深渊表层沉积物中发现了较高的有机物（OM）浓度。然而，这种生物物质的来源仍然难以捉摸。在此，我们报告了从阿塔卡马海沟最深点及其相邻的半深海边缘周围表层沉积物中提取的细胞膜完整极性脂质（IPL）的组成和分布，以评估和确定超深渊海底不稳定有机物的来源。对IPL结构多样性和丰度进行的多尺度自助重采样表明，阿塔卡马海沟沉积物中具有独特的脂质特征，与半深海沉积物中的脂质特征更为相似，而与该地区先前报道的上层海洋水体中的脂质特征差异较大。虽然超深渊沉积物中独特的IPL结构总数在总IPL库中所占比例较小，但我们也发现，含有单不饱和脂肪酸和双不饱和脂肪酸的磷脂占比较高，这些脂肪酸与光合自养来源无关，且类似于对高压和低温的生理适应特征。我们的研究结果表明，阿塔卡马海沟超深渊沉积物中的IPL主要来源于原位微生物生产和生物量，而来自真光层和上覆氧最小层的有机物库中最不稳定的脂质成分的输出可忽略不计。虽然不能排除其他有机物来源，如不稳定有机物的下坡和/或侧向运输，且仍需进一步研究，但鉴于酯键IPL的不稳定性，它们可能不太重要。我们的研究结果有助于理解控制不稳定有机物向这种极端深海生态系统输送的机制。此外，它们还为原位微生物群落通过脂质重塑对高压和低温的一些潜在生理适应提供了见解。
Abstract. Elevated organic matter (OM) concentrations are found in hadal surface sediments relative to the surrounding abyssal seabed. However, the origin of this biological material remains elusive. Here, we report on the composition and distribution of cellular membrane intact polar lipids (IPLs) extracted from surface sediments around the deepest points of the Atacama Trench and adjacent bathyal margin to assess and constrain the sources of labile OM in the hadal seabed. Multiscale bootstrap resampling of IPLs' structural diversity and abundance indicates distinct lipid signatures in the sediments of the Atacama Trench that are more closely related to those found in bathyal sediments than to those previously reported for the upper ocean water column in the region. Whereas the overall number of unique IPL structures in hadal sediments contributes a small fraction of the total IPL pool, we also report a high contribution of phospholipids with mono- and di-unsaturated fatty acids that are not associated with photoautotrophic sources and that resemble traits of physiological adaptation to high pressure and low temperature. Our results indicate that IPLs in hadal sediments of the Atacama Trench predominantly derive from in situ microbial production and biomass, whereas the export of the most labile lipid component of the OM pool from the euphotic zone and the overlying oxygen minimum zone is neglectable. While other OM sources such as the downslope and/or lateral transport of labile OM cannot be ruled out and remain to be studied, they are likely less important in view of the lability of ester-bond IPLs. Our results contribute to the understanding of the mechanisms that control the delivery of labile OM to this extreme deep-sea ecosystem. Furthermore, they provide insights into some potential physiological adaptation of the in situ microbial community to high pressure and low temperature through lipid remodeling.