Western Australia Organic and Isotope Geochemistry Centre, School of Molecular and Life Sciences, Curtin University, Bentley, Western Australia, Australia.
Western Australia Organic and Isotope Geochemistry Centre, School of Earth and Planetary Sciences, The Institute for Geoscience Research (TIGeR), Curtin University, Bentley, Western Australia, Australia.
Geobiology. 2021 Mar;19(2):162-172. doi: 10.1111/gbi.12421. Epub 2020 Dec 3.
The vertical distribution of subseafloor archaeal communities is thought to be primarily controlled by in situ conditions in sediments such as the availability of electron acceptors and donors, although sharp community shifts have also been observed at lithological boundaries suggesting that at least a subset of vertically stratified Archaea form a long-term genetic record of coinciding environmental conditions that occurred at the time of sediment deposition. To substantiate this possibility, we performed a highly resolved 16S rRNA gene survey of vertically stratified archaeal communities paired with paleo-oceanographic proxies in a sedimentary record from the northern Red Sea spanning the last glacial-interglacial cycle (i.e., marine isotope stages 1-6; MIS1-6). Our results show a strong significant correlation between subseafloor archaeal communities and drastic paleodepositional changes associated with glacial low vs. interglacial high stands (ANOSIM; R = .73; p = .001) and only a moderately strong correlation with lithological changes. Bathyarchaeota, Lokiarchaeota, MBGA, and DHVEG-1 were the most abundant identified archaeal groups. Whether they represented ancient cell lines from the time of deposition or migrated to the specific sedimentary horizons after deposition remains speculative. However, we show that the majority of sedimentary archaeal tetraether membrane lipids were of allochthonous origin and not produced in situ. Slow post-burial growth under energy-limited conditions would explain why the downcore distribution of these dominant archaeal groups still indirectly reflect changes in the paleodepositional environment that prevailed during the analyzed marine isotope stages. In addition, archaea seeded from the overlying water column such as Thaumarchaeota and group II and III Euryarchaeota, which were likely not have been able to subsist after burial, were identified from a lower abundance of preserved sedimentary DNA signatures, and represented direct markers of paleoenvironmental changes in the Red Sea spanning the last six marine isotope stages.
海底古菌群落的垂直分布主要受沉积物中电子受体和供体等原位条件的控制，尽管在岩性边界也观察到了明显的群落变化，这表明至少一部分垂直分层的古菌形成了一个长期的遗传记录，记录了在沉积物沉积时同时发生的环境条件。为了证实这种可能性，我们对来自红海北部的一段沉积记录进行了高分辨率的 16S rRNA 基因调查，该记录与古海洋学替代指标配对，跨越了末次冰消期-间冰期旋回（即海洋同位素阶段 1-6；MIS1-6）。我们的结果表明，海底古菌群落与与冰期低水位与间冰期高水位相关的剧烈古沉积变化之间存在很强的显著相关性（ANOSIM；R=0.73；p=0.001），而与岩性变化的相关性仅为中度强。广古菌门、洛基古菌门、MBGA 和 DHVEG-1 是最丰富的古菌分类群。它们是代表沉积时的古老细胞系，还是在沉积后迁移到特定的沉积层位，这仍然是推测。然而，我们表明，大多数沉积古菌四醚膜脂都是异地起源的，而不是原地产生的。在能量有限的条件下，缓慢的埋藏后生长可以解释为什么这些主要古菌群的向下分布仍然间接反映了在分析的海洋同位素阶段期间占主导地位的古沉积环境变化。此外，从上层水柱中播下的古菌，如泉古菌和 II 类和 III 类广古菌，在埋藏后可能无法生存，从保存下来的沉积 DNA 特征的低丰度中得到了鉴定，它们代表了过去六个海洋同位素阶段期间红海古环境变化的直接标志物。
