Abstract The TEX86 paleotemperature proxy is based on the distribution of archaeal glycerol dibiphytanyl glycerol tetraether (GDGT) lipids preserved in marine sediments, yet both the influence of different physiological factors on the structural distribution of GDGTs and the mechanism(s) by which GDGTs is(are) exported to marine sediments remain(s) unresolved. We investigated the abundance and structural distribution of GDGTs in the South-west and Equatorial Atlantic Ocean in four water column profiles spanning 48 degrees of latitude. The depth distribution was consistent with production by ammonia-oxidizing Thaumarchaeota; maximum GDGT concentration occurred at the base of the NO2− maximum, core GDGTs dominated the structural distribution in surface waters above the NO2− maximum, and intact polar GDGTs – potentially indicating live cells – were more abundant below the NO2− maximum. Between 0 and1000 m, > 98% of the integrated GDGT inventory was present in waters at and below the NO2− maximum. Depth profiles of TEX86 temperature values displayed local minima at the NO2− maximum, while the ratio of GDGT-2:GDGT-3 increased with depth. A model based on the results predicts an average depth of origin for GDGTs exported to sediments between ca. 80–250 m. In the model, exported TEX86 values are remarkably insensitive to change in the average depth of origin of GDGTs. However, TEX86 values exported from the water column appear to reflect euphotic zone productivity, possibly due to the correlative intensity of organic matter remineralization providing substrates for ammonia oxidation. Predicting the influence of these regional controls on sedimentary TEX86 records requires a better understanding of the interaction between GDGT production, particle dynamics, and the depth of origin for exported organic matter.

中文翻译：

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西大西洋水体悬浮颗粒物中类异戊二烯四醚脂质的分布和输出

摘要 TEX86 古温度代理基于海洋沉积物中保存的古菌甘油二联植烷甘油四醚 (GDGT) 脂质的分布，但不同生理因素对 GDGTs 结构分布的影响以及 GDGTs 的机制（是）出口到海洋沉积物的问题仍未得到解决。我们研究了西南和赤道大西洋中横跨 48 度纬度的四个水柱剖面中 GDGT 的丰度和结构分布。深度分布与氨氧化奇古菌生产一致；最大 GDGT 浓度出现在 NO2− 最大值的底部，核心 GDGT 主导了 NO2− 最大值以上地表水中的结构分布，完整的极地 GDGT（可能表明活细胞）在 NO2− 最大值以下更丰富。在 0 到 1000 m 之间，> 98% 的综合 GDGT 清单存在于处于和低于 NO2− 最大值的水域中。TEX86 温度值的深度剖面在 NO2− 最大值处显示局部最小值，而 GDGT-2:GDGT-3 的比率随深度增加。基于结果的模型预测了 GDGT 输出到沉积物的平均起源深度。80-250 米。在模型中，导出的 TEX86 值对 GDGT 平均起源深度的变化非常不敏感。然而，从水体输出的 TEX86 值似乎反映了富光区的生产力，这可能是由于有机物再矿化的相关强度为氨氧化提供了底物。