The detection of bacterial magnetite in recent sediments of Lake Chiemsee (southern Germany)
The detection of bacterial magnetite in recent sediments of Lake Chiemsee (southern Germany)
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DOI：
10.1016/j.epsl.2005.01.006
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发表时间：
2005-03-30
影响因子：
5.3
通讯作者：
Zhu, RX
中科院分区：
文献类型：
--
作者：
Pan, YX;Petersen, N;Zhu, RX
Chiemsee湖的沉积物位于德国南部的高山前陆，是多种趋磁细菌（MTB）的宿主，这些趋磁细菌含有呈线性链排列的细胞内磁铁矿晶体。为了检测碳酸盐为主的表层沉积物中的细菌磁铁矿，并进一步量化其对沉积物磁信号的贡献，我们进行了详细的岩石磁测量以及补充的非磁分析（电子显微镜，粉末x射线衍射和沉积物孔隙水分析）。我们的研究结果表明，生物成因的单畴磁铁矿（以子弹形和截形六边形棱柱形为特征）是沉积物最顶部几厘米的主要铁磁成分。磁性能随深度的变化是由于活的MTB的出现和生物成因磁铁矿的溶解作用向下增加所致。此外，通过Verwey转变对饱和等温剩余物的增温损失(δ (FC)/ δ (ZFC))的比值(δ (FC)/ δ (ZFC))分别为含MTB的冻干和风干沉积物样品的1.47和1.25。这些低比率表明细菌磁铁矿链在很大程度上被破坏和/或细菌磁小体可能经历了部分低温氧化。本文提出，尽管岩石磁测量适合于量化细粒颗粒对沉积物整体磁信号的贡献，但互补的非磁方法对于明确识别其细菌来源至关重要。(c) 2005 Elsevier B.V.版权所有
The sediments of Lake Chiemsee, located in the Alpine foreland in Southern Germany, host a variety of magnetotactic bacteria (MTB), which contain intracellular crystals of magnetite arranged in linear chains. To detect bacterial magnetite in the carbonate-dominated surface sediments and further quantify its contribution to the magnetic signal of the sediments, we conducted detailed rock magnetic measurements as well as complimentary non-magnetic analyses (electron microscopy, powder X-ray diffraction, and sediment pore-water analysis). Our results demonstrate that biogenic single-domain magnetite (characterized by bullet- and truncated hexagonal prismatic shapes) is the dominant ferrimagnetic component in the topmost few centimetres of the sediment. The changes of magnetic properties with depth are due to the occurrence of live MTB and the downward increasing dissolution of biogenic magnetite. Moreover, the ratios of remanence loss on warming through the Verwey transition after field cooling and zero-field cooling of saturation isothermal remanence (delta(FC)/delta(ZFC)) were determined as 1.47 and 1.25 for freeze-dried and air-dried sediment samples containing MTB, respectively. These low ratios suggest that the bacterial magnetite chains were disrupted to a large extent and/or that the bacterial magnetosomes might have undergone partial low-temperature oxidation. It is proposed that although rock magnetic measurements are suitable for quantifying the contribution of fine-grained particles to the overall magnetic signal of sediments, complementary non-magnetic methods are essential to unambiguously identify its bacterial origin. (c) 2005 Elsevier B.V. All rights reserved.