Sources of core and intact branched tetraether membrane lipids in the lacustrine environment: Anatomy of Lake Challa and its catchment, equatorial East Africa
Sources of core and intact branched tetraether membrane lipids in the lacustrine environment: Anatomy of Lake Challa and its catchment, equatorial East Africa
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DOI：
10.1016/j.gca.2014.04.042
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发表时间：
2014-09-01
影响因子：
5
通讯作者：
Damste, Jaap S. Sinninghe
中科院分区：
文献类型：
--
作者：
Buckles, Laura K.;Weijers, Johan W. H.;Damste, Jaap S. Sinninghe
MBT/CBT古温度代理使用分布的支链甘油二烷基甘油四醚（brGDGT），膜脂，应该来自土壤细菌，重建平均年气温（MAAT）。在沿海海洋沉积物中的成功应用，将其扩展到具有潜在高时间分辨率的湖泊沉积物记录将大大扩展其实用性。然而，在过去的几年里，研究表明，湖泊系统内存在其他来源的brGDGT。为了限制影响湖泊MBT/CBT古温度代用指标的因素，有必要对现代湖泊系统中的brGDGT通量进行详细调查，以确定其潜在来源。这项研究集中在查拉湖，一个永久分层的火山口湖在赤道东非有限的集水面积。近3年的时间序列，大约每月样品的沉降颗粒，补充了悬浮颗粒物（SPM）的深度剖面和集深的表面沉积物和集水区土壤样品，分析了“活”完整的极性脂质（IPL）和“化石”核心脂质（CL）的GDGT。我们发现，brGDGT产生在好氧，缺氧和缺氧区的水柱，并在大量的集水土壤相比，流入。湖泊沉积物中的额外原位生产是最有可能的，但目前无法肯定。这些湖相brGDGT显示不同的温度变化的反应比土壤来源的brGDGT，这意味着一个不同的生理适应变化的条件下的水柱和/或不同的组合物的相应的细菌群落。使用这种特定的温度关系，在SPM的brGDGT分布的基础上，本地校准产生相对准确的水温估计从沉降颗粒，但失败的表层沉积物。(C)2014爱思唯尔有限公司版权所有。
The MBT/CBT palaeotemperature proxy uses the distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs), membrane lipids that are supposed to derive from soil bacteria, to reconstruct mean annual air temperature (MAAT). Applied successfully in coastal marine sediments, its extension to lake-sediment records with potentially high time resolution would greatly expand its utility. Over the last years, however, studies have indicated the presence of additional sources of brGDGTs within lake systems. To constrain the factors influencing the MBT/CBT palaeotemperature proxy in lakes, detailed investigation of brGDGT fluxes in a modern lake system is necessary to identify their potential sources. This study concentrates on Lake Challa, a permanently stratified crater lake in equatorial East Africa with limited catchment area. An almost 3-year time series of approximately monthly samples of settling particles, supplemented with a depth profile of suspended particulate matter (SPM) and sets of profundal surface-sediment and catchment soil samples, were analysed for both the 'living' intact polar lipids (IPLs) and 'fossil' core lipids (CLs) of GDGTs. We found that brGDGTs are produced in oxic, suboxic and anoxic zones of the water column, and in substantial amounts compared to influxes from catchment soils. Additional in situ production within the lake sediments is most probable, but cannot be definitely confirmed at this time. These lacustrine brGDGTs display a different response to temperature variation than soil-derived brGDGTs, signifying either a different physiological adaptation to changing conditions within the water column and/or a different composition of the respective bacterial communities. Using this specific relationship with temperature, a local calibration based on brGDGT distributions in SPM generates relatively accurate water temperature estimates from settling particles but fails for surface sediments. (C) 2014 Elsevier Ltd. All rights reserved.