The lipid content of a high mountain lake (Lake Isoba) allowed the reconstruction of the paleoenvironmental changes and anthropic influence in Northern Spain during the last 550 years. Fatty acids (FAs) and alkan-2-ones indicate little degradation of OM. Three units were delimited. During Unit A (ca. 1460-1780 CE) high carbon preference index values, predominance of high-molecular-weight saturated FAs, and good correspondence between the predominant alkane and saturated FA chains indicate higher OM input and evidence of minimal degradation, linked to the cold and dry Little Ice Age, that favoured the OM input derived mainly from land plants, and the reduced bacterial activity. In Unit B (ca. 1780-2006 CE) the -alkane and saturated FA profiles showed a remarkable mismatch suggestive of preferential microbial synthesis of long chain saturated FAs from primary OM and/or bacterial activity (predominance of low-molecular-weight saturated FAs but with a bimodal distribution), in coincidence with a decrease in OM input, which could be linked to the global warming that started in the second half of the 19 century. Although OM continued deriving mainly from terrigenous plants, aquatic macrophytes increased their contribution to the OM indicating the amelioration of environmental conditions. Evidence of considerable phytoplankton productivity and microbial activity was significant in Unit C (ca. 2006-2018 CE) coinciding with the highest concentrations of alkanes and saturated FAs, linked to warmer and drier conditions, and to greater anthropogenic influence. In addition, organic sulfur and gammacerane indicates loss of oligotrophy, and the record of faecal stanols, particularly that of 24-ethylcoprostanol, strongly evidences notable and rising water pollution associated with increasing cattle ranching in the lake catchment during the past 10-15 years.

中文翻译：

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坎塔布连山脉（西班牙北部）高山湖泊中的脂质生物标志物：自然驱动因素和人为驱动因素之间的相互作用

高山湖泊（伊索巴湖）的脂质含量可以重建西班牙北部过去 550 年的古环境变化和人类影响。脂肪酸 (FA) 和 alkan-2-one 表明 OM 几乎没有降解。划定了三个单位。在 A 单元（约公元 1460-1780 年）期间，高碳偏好指数值、高分子量饱和 FA 占主导地位，以及主要烷烃和饱和 FA 链之间良好的对应关系表明较高的 OM 输入和最小降解的证据，这与寒冷干燥的小冰河时期，有利于主要来自陆地植物的有机质输入，并且细菌活性降低。在单元 B（约 1780-2006 CE）中，α-烷烃和饱和 FA 谱显示出显着的不匹配，表明微生物优先从初级 OM 和/或细菌活性合成长链饱和 FA（低分子量饱和 FA 占主导地位）但呈双峰分布），与 OM 输入的减少同时发生，这可能与 19 世纪下半叶开始的全球变暖有关。尽管有机质继续主要来源于陆源植物，但水生植物对有机质的贡献有所增加，这表明环境条件的改善。有证据表明，C 单元（约 2006-2018 CE）具有相当大的浮游植物生产力和微生物活性，恰逢烷烃和饱和 FA 浓度最高，与温暖和干燥的条件以及更大的人为影响有关。此外，有机硫和伽马蜡烷表明寡营养的丧失，而粪便甾烷醇的记录，特别是24-乙基粪甾烷醇，有力地证明了过去10-15年中与湖流域养牛场增加有关的显着且不断上升的水污染。