Abstract Glycerol dialkyl glycerol tetraethers (GDGTs) have been widely used to elucidate sources of sediment total organic carbon (TOC), past temperature and presence of methanogenesis in diverse environments. However, their applicability to hadal trenches with their unique deposition dynamics remains unknown. Here, we analyzed GDGTs and their stable isotope values and content of TOC in surface sediments from the Kermadec Trench region (KT; 6080–10010 m), New Britain Trench region (NBT; 1553–8931 m), and Atacama Trench region (AT; 2560–8085 m). These regions are at very different distances from terrestrial sources and have varying net primary productivity (NPP) in the waters above them. The GDGT concentration was highly variable (54.5–2416 μg g−1 TOC) within and between trench regions and was not directly related to local NPP or apparent terrestrial inputs. This finding is presumably due to complex deposition dynamics within the trench interior. Isoprenoidal GDGTs (isoGDGTs; 75.4–99.1%) were dominant over branched GDGTs (brGDGTs, 0.91–24.6%) in all samples, leading to low levels of Branched versus Isoprenoidal Tetraether (BIT) index (0.01–0.27). Thus, sediment TOC is mainly derived from marine sources. However, compared to adjacent non-hadal sites, trench axis sites have a higher BIT index, lower acyclic hexa-/pentamethylated brGDGT and lower δ13C, supporting relative enrichment of terrestrial organic carbon at the trench axis. The application of TetraEther indeX of tetraethers consisting of 86 carbon atoms (TEX86) resulted in sea surface temperature (SST) estimates of 18.9–23.7 °C in the KT, 28.6–30.2 °C in the NBT, and 17.9–20.4 °C in the AT. The close agreement between TEX86-SST with observed in situ SST suggests that isoGDGTs are not selectively degraded during the transport towards the hadal realm, and that TEX86 from hadal settings robustly records an integrated regional SST signal.

中文翻译：

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三个太平洋海沟表层沉积物中的甘油二烷基甘油四醚：分布、来源和环境影响

摘要 甘油二烷基甘油四醚 (GDGTs) 已被广泛用于阐明沉积物总有机碳 (TOC) 的来源、过去的温度和不同环境中产甲烷的存在。然而，它们对具有独特沉积动力学的深渊沟槽的适用性仍然未知。在这里，我们分析了克马德克海沟地区 (KT; 6080–10010 m)、新不列颠海沟地区 (NBT; 1553–8931 m) 和阿塔卡马海沟地区 (AT) 表层沉积物中的 GDGT 及其稳定同位素值和 TOC 含量；2560–8085 米）。这些地区与陆地资源的距离大不相同，其上方水域的净初级生产力 (NPP) 也各不相同。GDGT 浓度变化很大（54. 5–2416 μg g-1 TOC）在沟槽区域内和沟槽区域之间，并且与当地 NPP 或明显的地面输入没有直接关系。这一发现可能是由于沟槽内部复杂的沉积动力学。在所有样品中，类异戊二烯 GDGT（isoGDGT；75.4–99.1%）比分支 GDGT（brGDGT，0.91–24.6%）占优势，导致分支与类异戊二烯四醚 (BIT) 指数 (0.01–0.27) 的水平较低。因此，沉积物 TOC 主要来源于海洋。然而，与相邻的非哈达尔位点相比，沟渠轴位点具有更高的 BIT 指数、更低的非环六甲基化/五甲基化 brGDGT 和更低的 δ13C，支持沟渠轴处陆地有机碳的相对富集。由 86 个碳原子组成的四醚 (TEX86) 的 TetraEther 指数的应用导致海面温度 (SST) 估计值为 18。KT 为 9–23.7 °C，NBT 为 28.6–30.2 °C，AT 为 17.9–20.4 °C。TEX86-SST 与观察到的原位 SST 之间的密切一致性表明 isoGDGT 在向深海领域的运输过程中没有选择性降解，并且来自深海环境的 TEX86 稳健地记录了综合的区域 SST 信号。