The response of marine ammonia-oxidizing archaea (AOA) to environmental stress is reflected in changes in their membrane lipid composition, particularly the unique isoprenoid glycerol dialkyl glycerol tetraethers (iGDGTs). However, the influence of dissolved oxygen (DO) on the composition of iGDGTs in the ocean remains unclear. This study aims to investigate the link between DO levels and the fractional abundances of iGDGTs in the East China Sea (ECS) to establish a redox proxy. Results suggested that the absolute abundances of iGDGTs were influenced by Thaumarchaeota biomass when DO concentrations exceeded 2 mg/L. Vertical distributions of iGDGTs through the water column suggested their transport from bottom waters to sediments. Increasing proportions of iGDGT-0 and the sum of iGDGT-1, iGDGT-2 and iGDGT-3 from suspended particulate matters to surface sediments indicated their preferential preservation. DO concentrations (2–6 mg/L) in the water column showed a significant positive correlation with the relative abundance of crenarchaeol (cren%) but a negative correlation with iGDGT-0%, suggesting insufficient DO levels to promote AOA cyclization. However, bottom DO concentrations exhibited significant negative correlations with both cren% and iGDGT-0% in surface sediments, attributed to enhanced cyclization of iGDGTs and Euryarchaeota abundance within more reducing sediments, respectively. The consistent relationship between iGDGT-0% and DO in both water column and sediments enabled iGDGT-0% to be a potential redox proxy. Temporal variations in iGDGT-0% in the ECS in recent decades aligned well with DO monitoring data, further validating iGDGT-0% as a promising redox proxy.

中文翻译：

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海洋环境中类异戊二烯四醚脂质的氧化还原指示潜力：来自东海的见解


海洋氨氧化古菌（AOA）对环境压力的反应反映在其膜脂成分的变化，特别是独特的类异戊二烯甘油二烷基甘油四醚（iGDGT）。然而，溶解氧（DO）对海洋中 iGDGT 组成的影响仍不清楚。本研究旨在调查东海 (ECS) 中 DO 水平与 iGDGT 丰度分数之间的联系，以建立氧化还原代理。结果表明，当 DO 浓度超过 2 mg/L 时，iGDGT 的绝对丰度受到奇古菌生物量的影响。 iGDGT 在水体中的垂直分布表明它们从底层水迁移到沉积物。从悬浮颗粒物到表层沉积物中，iGDGT-0 以及 iGDGT-1、iGDGT-2 和 iGDGT-3 总和的比例不断增加，表明它们优先保存。水体中的 DO 浓度 (2–6 mg/L) 与 crenarchaeol 的相对丰度 (cren%) 呈显着正相关，但与 iGDGT-0% 呈负相关，表明 DO 水平不足以促进 AOA 环化。然而，底部 DO 浓度与表层沉积物中的 cren% 和 iGDGT-0% 表现出显着的负相关，这分别归因于更多还原性沉积物中 iGDGT 和广古菌丰度的环化增强。 iGDGT-0% 和水体和沉积物中 DO 之间的一致关系使 iGDGT-0% 成为潜在的氧化还原代理。近几十年来 ECS 中 iGDGT-0% 的时间变化与 DO 监测数据非常吻合，进一步验证了 iGDGT-0% 作为一种有前途的氧化还原代理。