Diatom dynamics during the last six centuries in Lake Odensjön: a new varved sediment record from southern Sweden

IF 1.7 3区 地球科学 Q4 ENVIRONMENTAL SCIENCES
Ethan L. Silvester, Karl Ljung, Richard Bindler, Hanna Hertzman, Giulia Lodi, Dan Hammarlund
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引用次数: 0

Abstract

Varved lake sediments offer valuable insight into past environmental conditions with high temporal resolution and precise chronological control. A combination of diatom and geochemical analyses of the recently deposited sediments of Odensjön, a small dimictic lake in southern Sweden, shows alternating light and dark laminae composed of greater amounts of biogenic silica and organic matter, respectively. As confirmed by independent radiometric dating and Pb pollution data, and supported by scanning electron microscopy of individual laminae, these features represent ongoing deposition of biogenic varves. Corresponding diatom and geochemical data obtained from a 92-cm long freeze core provide evidence of substantial lake-ecosystem dynamics during the last six centuries, related mainly to variations in light penetration and wind shear driven by human-induced changes in catchment vegetation. The diatom assemblage of Odensjön’s varved sediments is dominated by planktonic species, primarily Asterionella formosa, Fragilaria saxoplanktonica and Discostella lacuskarluki during periods of forest cover, while increased catchment openness from the mid-1500s to the late 1800s led to increased abundance of Lindavia comensis. Long-term variations in climate and land use, mediated through changing length of the ice-cover season and nutrient input, respectively, probably contributed to the observed trends, as well as to variations in the appearance and visibility of the varve record across the sampled sediment sequence. Odensjön represents the southernmost varved sediment record in Fennoscandia documented to date, offering potential to study the effects of various types of external forcing on its sensitive lacustrine ecosystem since the Late Weichselian deglaciation. In the present study, we investigated the possibility of assessing the local impacts of two major, historically documented volcanic events, Laki 1783–84 and Tambora 1815, which are known to have affected European societies. Although the mildly alkaline waters of the lake are well buffered and hence relatively resilient to volcanic acid deposition, a minor response to the Laki eruption may be recorded in the diatom stratigraphy.

Abstract Image

奥登斯约恩湖过去六个世纪的硅藻动态:瑞典南部新的变异沉积物记录
多变的湖泊沉积物具有很高的时间分辨率和精确的年代控制能力,为了解过去的环境状况提供了宝贵的信息。对瑞典南部一个小型二叠纪湖泊 Odensjön 最近沉积的沉积物进行的硅藻和地球化学综合分析表明,浅色和深色层理交替出现,分别由较多的生物硅质和有机质组成。独立的放射性年代测定和铅污染数据证实了这些特征,单个层状物的扫描电子显微镜也证明了这一点,这些特征代表了生物成因变异体的持续沉积。从一个 92 厘米长的冰冻岩芯中获得的相应硅藻和地球化学数据证明,在过去的六个世纪中,湖泊生态系统发生了巨大变化,这主要与人类引起的集水区植被变化所导致的透光率和风切变有关。在森林覆盖时期,奥登斯约恩变异沉积物中的硅藻群以浮游生物为主,主要有 Asterionella formosa、Fragilaria saxoplanktonica 和 Discostella lacuskarluki,而从 15 世纪中期到 18 世纪晚期,集水区的开放程度增加,导致 Lindavia comensis 的数量增加。气候和土地利用的长期变化(分别通过冰盖季节长度和养分输入的变化)很可能导致了观察到的趋势,以及取样沉积物序列中变异记录的出现和可见度的变化。奥登斯约恩是迄今为止所记录的芬诺斯坎迪亚最南端的变异沉积记录,为研究自晚期魏希塞尔脱冰期以来各种类型的外力作用对其敏感的湖沼生态系统的影响提供了可能。在本研究中,我们调查了评估两个有历史记载的重大火山事件(拉基 1783-84 年和坦博拉 1815 年)对当地影响的可能性。虽然该湖的弱碱性水体具有良好的缓冲能力,因此相对能够抵御火山酸沉积,但硅藻地层中可能记录了对拉基火山爆发的轻微反应。
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来源期刊
Journal of Paleolimnology
Journal of Paleolimnology 地学-地球科学综合
CiteScore
3.70
自引率
9.50%
发文量
44
审稿时长
3 months
期刊介绍: The realization that a historical perspective is often useful, if not essential, to the understanding of most limnological processes has resulted in the recent surge of interest in paleolimnology. The main aim of the Journal of Paleolimnology is the provision of a vehicle for the rapid dissemination of original scientific work dealing with the reconstruction of lake histories. Although the majority of papers deal with lakes, paleoenvironmental studies of river, wetland, peatland and estuary systems are also eligible for publication. The Journal of Paleolimnology, like the subject itself, is multidisciplinary in nature, and papers are published that are concerned with all aspects (e.g. biological, chemical, physical, geological, etc.) of the reconstruction and interpretation of lake histories. Both applied and more theoretical papers are equally encouraged. The Journal of Paleolimnology will continue to be a major repository for papers dealing with climatic change, as well as other pressing topics, such as global environmental change, lake acidification, eutrophication, long-term monitoring, and other aspects of lake ontogeny. Taxonomic and methodological papers are also acceptable provided they are of relatively broad interest. New equipment designs are frequently featured. In addition to original data and ideas, the Journal of Paleolimnology also publishes review articles, commentaries and program announcements. A relevant Book Review Section is also featured.
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