Silicon isotope records of recent environmental change and anthropogenic pollution from Lake Baikal, Siberia

贝加尔湖是世界上最古老的湖泊，位于西伯利亚东南部的裂谷地带（东经103043′- 109058′和北纬51028′-55o47′），形成于2000多万年前。作为世界上最深、面积最大的湖泊，它也是一个主要的水资源，占全球地表淡水的20%。贝加尔湖的一个主要特征是高度的生物多样性，有超过2500种动植物，其中大多数是地方性的。如此高的地方性使得该湖被称为“淡水生态系统最杰出的例子”，并于1996年被指定为世界遗产。然而，自20世纪50年代以来，工业发展和集水区土地利用的变化对湖泊生态系统的稳定构成了现实和严重的威胁，主要城市、工业中心、采矿和农业活动的污染进入湖泊。湖泊对人为气候变化的反应也很强烈。首先，全球变暖对区域永久冻土产生了重大影响，融化加剧，导致湖泊的营养输入增加。其次，南部盆地水柱温度明显升高。第三，近几十年来，冰盖的持续时间和厚度显著下降，预计未来还会进一步下降。这种变化将对食物网的相互作用和更广泛的生态系统产生重大影响，从冰下初级生产者的快速增长到湖中最大的消费者——西伯利亚海豹（世界上唯一的淡水海豹）。为了确保未来的流域发展和政策计划能够维持贝加尔湖独特的生态系统，需要详细了解人为影响对湖泊的影响。这方面的努力正在进行，并由俄罗斯伊尔库茨克湖沼研究所的监测方案领导。该项目将通过在贝加尔湖开发硅同位素测量的应用来补充和扩展这项工作，以提供有关生物源养分利用变化的信息。首先在现代水柱中对该方法进行校准，然后从湖泊周围的一系列沉积物岩心中进行测量，以检查：1)最近20世纪集水区发展和气候变化对养分利用的影响；2)确定湖泊对过去1000年来发生的自然气候变化的反应。该项目的结果将提供有价值的信息，帮助科学家、政策制定者和其他利益相关者了解近期集水区/气候变化对贝加尔湖的影响，并表明该湖对未来气候变化的脆弱性。

Lake Baikal is the world's oldest lake lying in a rift zone in south eastern Siberia (103o43'-109o58'E and 51o28'-55o47'N) that began to form over 20 million years ago. As well as being the world's deepest and most voluminous, the lake also acts as a major water resource containing c. 20% of global surface freshwater. A key feature of Lake Baikal is the high degree of biodiversity with over 2,500 flora and fauna, the majority of which are endemic. Such high levels of endemicity have led to the lake being cited as the "most outstanding example of a freshwater ecosystem" and resulted in the site being designated a World Heritage Site in 1996. Industrial development and changes in catchment land-use since the 1950's, however, pose real and serious threats to the stability of the lake's ecosystem with pollution entering the lake from major conurbations, industrial centres, mining and agricultural practises. The lake is also responding strongly to anthropogenic climate change. Firstly, global warming is having a major impact on regional permafrost with increased melting leading to enhanced nutrient inputs to the lake. Secondly, marked increases in water column temperatures have been observed in the south basin. Thirdly, the duration of ice cover and ice thickness have declined significantly in recent decades with further declines forecast for the future. Such changes will have major implications for the food-web interactions and the wider ecosystem from the rapid growth of primary producers underneath clear ice to the lake's top consumer, Phoco sibirica (the world's only freshwater seal).In order to ensure that future development and policy plans for the catchment are capable of sustaining Lake Baikal's unique ecosystem, there is a need for a detailed understanding as to the impact of anthropogenic influences on the lake. Efforts towards this are ongoing and led by monitoring programmes from the Limnological Research Institute in Irktusk, Russia. This project will complement and extend this work by developing the application of silicon isotope measurements in Lake Baikal to provide information on changes in biogenic nutrient utilisation. By first carrying out a calibration of the method in the modern day water column, measurements will then be taken from a series of sediment cores from around the lake to examine: 1) the impact of recent 20th Century catchment development and climate change on nutrient utilisation; 2) ascertain the response of the lake to natural climatic changes that have occurred over the last 1000 years. Results from this project will provide valuable information that will aid scientists, policy makers and other stakeholders as to the impact of recent catchment/climate changes on Lake Baikal as well as an indication of the lake's vulnerability to future climate change.