Distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) are frequently employed for reconstructing terrestrial paleotemperatures from lake sediment archives. Although brGDGTs are globally ubiquitous, the microbial producers of these membrane lipids remain unknown, precluding a full understanding of the ways in which environmental parameters control their production and distribution. Here, we advance this understanding in three ways. First, we present 43 new high-latitude lake sites characterized by low mean annual air temperatures (MATs) and high seasonality, filling an important gap in the global dataset. Second, we introduce a new approach for analyzing brGDGT data in which compound fractional abundances (FAs) are calculated within structural groups based on methylation number, methylation position, and cyclization number. Finally, we perform linear and nonlinear regressions of the resulting FAs against a suite of environmental parameters in a compiled global lake sediment dataset (n = 182). We find that our approach deconvolves temperature, conductivity, and pH trends in brGDGTs without increasing calibration errors from the standard approach. We also find that it reveals novel patterns in brGDGT distributions and provides a methodology for investigating the biological underpinnings of their structural diversity. Warm-season temperature indices outperformed MAT in our regressions, with the mean temperature of months above freezing yielding the highest-performing model (adjusted R² = 0.91, RMSE = 1.97 ^∘C, n = 182). The natural logarithm of conductivity had the second-strongest relationship to brGDGT distributions (adjusted R² = 0.83, RMSE = 0.66, n = 143), notably outperforming pH in our dataset (adjusted R² = 0.73, RMSE = 0.57, n = 154) and providing a potential new proxy for paleohydrology applications. We recommend these calibrations for use in lake sediments globally, including at high latitudes, and detail the advantages and disadvantages of each.

中文翻译：

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修正的丰度分数和暖季温度显着改善了湖泊沉积物中的 brGDGT 校准

支化甘油二烷基甘油四醚 (brGDGT) 的分布经常用于从湖泊沉积物档案中重建陆地古温度。尽管 brGDGT 在全球范围内无处不在，但这些膜脂的微生物生产者仍然未知，因此无法充分了解环境参数控制其生产和分布的方式。在这里，我们从三个方面推进这种理解。首先，我们展示了 43 个新的高纬度湖泊站点，其特点是年平均气温 (MAT) 低且季节性强，填补了全球数据集中的一个重要空白。其次，我们引入了一种分析 brGDGT 数据的新方法，其中基于甲基化数、甲基化位置和环化数在结构组内计算化合物分数丰度 (FA)。n  =  182）。我们发现我们的方法去卷积了 brGDGT 中的温度、电导率和 pH 趋势，而不会增加标准方法的校准误差。我们还发现它揭示了 brGDGT 分布的新模式，并提供了一种研究其结构多样性的生物学基础的方法。在我们的回归中，暖季温度指数的表现优于 MAT，高于冰点的月份平均温度产生了性能最高的模型（调整后的R ²  =  0.91，RMSE  =  1.97  ^∘ C， n  =  182）。电导率的自然对数与 brGDGT 分布（调整后的R²  =  0.83，RMSE  =  0.66， n  =  143），在我们的数据集中明显优于 pH（调整后的R ²  =  0.73，RMSE  =  0.57， n  =  154），并为古水文学应用提供了一个潜在的新代理。我们建议将这些校准用于全球湖泊沉积物，包括在高纬度地区，并详细说明每种方法的优缺点。