Climatic and ecological changes of the past 1900 years inferred from long-chain alkenones in Kusai Lake, northern Qinghai-Tibetan Plateau
Climatic and ecological changes of the past 1900 years inferred from long-chain alkenones in Kusai Lake, northern Qinghai-Tibetan Plateau
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DOI：
10.1016/j.quaint.2018.02.007
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发表时间：
2018-09
影响因子：
2.2
通讯作者：
Xudong Wu;Xingqi Liu;Jianjun Wang;Masanobu Yamamoto
中科院分区：
文献类型：
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作者：
Xudong Wu;Xingqi Liu;Jianjun Wang;Masanobu Yamamoto
我们报告了从青藏高原北部库赛湖取回的沉积物岩芯中长达 1900 年的烷酮浓度、C 38/C 37 比值、U 37 k、U 37 k' 以及新开发的基于烯酮不饱和指数 U 37 k'' 的温度记录。 C 37 和 C 38 烯酮占主导地位，少量存在 C 39 和 C 40 烯酮，并且不存在 C 38 甲基烯酮，这表明等鞭金藻产生了烯酮，这与沉积的固定植物 DNA 分析的结果一致。公元400年至1200年的时间间隔的特征是比其他时间间隔更高的烯酮浓度和C 38 / C 37 比率，这可以归因于整个浮游植物水华期间等鞭金藻的主要产生。在基因丰度信息的帮助下，我们将这一现象归因于公元1200年左右库赛湖因气候从温暖潮湿到寒冷干燥条件的变化而发生的剧烈生态变化，导致河流流入量减少但养分浓度增加。根据对德国高纬度地区湖泊研究得出的方程，以 U 37 k'' 为基础的 U 37 k'' 代替 U 37 k'' 的温度是库赛湖最可靠的重建夏季地表水温，因为它们与库赛湖以南约 50 公里处的五道梁气象站当前夏季月平均气温接近，并表现出以下变化： 总体上与根据库赛湖沉积物中的 varve 轻层厚度重建的 51 年移动平均夏季温度一致。此外，基于U 37 k''的夏季地表水温显示的变化也与重建的中国气温显示的变化基本一致。
We report 1900-year long records of alknone concentration, C 38/C 37 ratio, and U 37 k, U 37 k'and a newly-developed alkenone unsaturation index U 37 k''-based temperatures in a sediment core retrieved from Kusai Lake in the northern Qinghai-Tibetan Plateau. The predominance of C 37 and C 38 alkenones with minor presence of C 39 and C 40 alkenones, and the absence of C 38 methyl alkenones are indicative of alkneones produced by Isochrysis, which is consistent with the results of sedimentary haptophyte DNA analyses. The interval from 400 to 1200 AD is characterized by higher alkenone concentrations and C 38/C 37 ratios than the other intervals, which can be attributed to the predominant production of Isochrysis during the entire phytoplankton blooms. With the assistance of information on gene abundance, we attributed this phenomenon to drastic ecological changes in Kusai Lake around 1200 AD in response to climatic changes from warm and wet to cold and dry conditions, and resultant decreased riverine inflow but increased nutrient concentration. The U 37 k''-based temperatures with U 37 k''substituting U 37 k'in a equation concluded based on studies on lakes from high latitude areas in Germany are the most reliable reconstructed summer surface water temperatures for Kusai Lake since they are close to the current summer monthly mean temperature of Wudaoliang Meteorological Station, approximately 50 km to the south of Kusai Lake, and exhibit variations that are generally in accordance with those of the 51-year moving average summer temperatures reconstructed from thicknesses of varve light layers in Kusai Lake sediments. Besides, variations showed by this U 37 k''-based summer surface water temperatures are also generally consistent with those showed by reconstructed temperatures in China.