Glycerol Dialkyl Glycerol Tetraethers (GDGTs) are ubiquitous biomolecules whose structural diversity or isotopic composition is increasingly used to reconstruct environmental changes such as air temperature or pCO₂. Isoprenoid GDGTs (iGDGT), in particular GDGT-0, are biosynthesized by a large range of Archaea. To assess the potential of GDGT-0 as a tracer of past methane cycle variations, three sediment cores from the Mackenzie River Delta have been studied for iGDGT and diploptene concentration, distribution and stable carbon signature. The absence of crenarchaeol, high GDGT-0 vs crenarchaeol ratio values, and ¹³C-enriched carbon signature of GDGT-0 indicate production by acetoclastic methanogens as well as heterotrophic Archaea. The oxidation of methane seems to be dominated by bacteria as indicated by the high abundance of ¹³C-depleted diploptene. Branched GDGTs (brGDGT), thought to be produced by heterotrophic bacteria, are dominated by hexa- and penta-methylated 5- and 6-methyl compounds. The presence of 5,6-methyl isomer IIIa’’ points towards in situ production of brGDGTs, with only a minor input from soil branched GDGT brought by the Mackenzie River. Carbon isotopic compositions of brGDGTs are in agreement with heterotrophic producers, likely living during summer. The reconstructed temperatures using a global lake calibration reflect recorded summer air temperature (±2 °C) during the last 60 years, and further highlight the absence of warming in summer in this region during the last 200 years. Oxygen availability and connection time to the Mackenzie River also seem to control the distribution of brGDGT with an increase in 6-methyl and 5,6-methyl isomers during periods of increased anoxia.

甘油二烷基甘油四醚 (GDGT) 是无处不在的生物分子，其结构多样性或同位素组成越来越多地用于重建环境变化，例如气温或p CO ₂。类异戊二烯 GDGT (iGDGT)，特别是 GDGT-0，是由大范围的古细菌生物合成的。为了评估 GDGT-0 作为过去甲烷循环变化示踪剂的潜力，研究了来自 Mackenzie 河三角洲的三个沉积物岩心的 iGDGT 和双萜浓度、分布和稳定的碳特征。不存在 crenarchaeol、高 GDGT-0 与 crenarchaeol 比率值，以及¹³GDGT-0 的富含 C 的碳特征表明产甲烷菌以及异养古细菌。甲烷的氧化似乎以细菌为主，如¹³C-耗尽的双萜。支链 GDGT (brGDGT) 被认为是由异养细菌产生的，主要由六甲基化和五甲基化的 5 和 6 甲基化合物组成。5,6-甲基异构体 IIIa'' 的存在表明 brGDGT 的原位生产，只有少量来自 Mackenzie 河带来的土壤支链 GDGT 的输入。brGDGT 的碳同位素组成与异养生产者一致，可能生活在夏季。使用全球湖泊校准重建的温度反映了过去 60 年记录的夏季气温 (±2°C)，进一步突出了该地区在过去 200 年中没有夏季变暖。与 Mackenzie 河的氧气可用性和连接时间似乎也控制了 brGDGT 的分布，增加了 6-甲基和 5，