Reconstructing pollution histories in the Lake Baikal basin: an application of silicon isotope geochemistry

This post represents the contributions of three authors. Anson Mackay is a professor in the Department of Geography at University College London and a member of the Open Quaternary Editorial Board. Virginia Panizzo is a Research Fellow in the School of Geography at the University of Nottingham. George Swann is an Assistant Professor in the School of Geography at the University of Nottingham.

Figure 1.  Freshwater seals (Pusa sibrica) in Lake Baikal. Photo credit: Sergey Gabdurakhmanov

Figure 1. Freshwater seals (Pusa sibrica) in Lake Baikal. Photo credit: Sergey Gabdurakhmanov

Lake Baikal [map] is one of our most iconic freshwater ecosystems – it is the deepest, oldest and most voluminous lake in the world. Most of the plants and animals that live in Lake Baikal are endemic, that is they are found nowhere else in the world, from the microscopic algae responsible for much of the lake’s primary production to one of the world’s few species of freshwater seal. Since the 1960s Lake Baikal has faced many environmental threats, including effluent from the Baikal Paper and Pulp Mill situated in the south basin (although this has now closed), multiple sources of pollution being released into the Selenga River and unregulated logging in the lake’s catchment. While these threats remain real, Lake Baikal has displayed considerable resilience, in the main due to its sheer size and volume. However, new threats are widespread, most notably economic development in the catchment (e.g. mining and pipelines), on-going pollutant release into the Selenga River, increasing tourism (PDF), and anthropogenic climate change, which is already impacting ice cover on the lake (Todd and Mackay, 2003), and the lake’s biota (Hampton et al., 2008).

Our UK-led consortium  of British, Russian and Swiss scientists is currently exploring the impact of environmental threats on primary producers in Lake Baikal, because these are at the base of it’s food-web, and therefore act as early warning indicators of disruption of the lake’s ecosystem. The two main approaches used are pigment analyses and silicon isotope geochemistry; it is this latter, rather novel, approach which forms the basis for the rest of this blog.

Figure 2.  The cozy kunks of Lake Baikal.  Credit: Beat Mueller.

Figure 2. The cozy kunks of Lake Baikal. Credit: Beat Mueller.

Silicon stable isotope geochemistry (d30Si) has the potential to provide critical information for our understanding of both regional and global silicon and carbon cycles (Leng et al., 2009). To date there are few terrestrial studies, especially those that focus on freshwater environments. We hypothesise that d30Si analyses from Lake Baikal and its catchment, will record changes in aquatic productivity, linked to industrial development, urban growth and agricultural practises. To disentangle enrichment caused by either pollution or climate change, cores from different parts of the lake are being examined over three timeframes (the past 5 years, 50 years and 500-1000 years).

Figure 3. Sampling on the surface of Lake Biakal.

Figure 3. Sampling on the surface of Lake Biakal.

Like all palaeoenvironmental proxies, a robust interpretation requires detailed understanding of their behaviour in the contemporary environment. This necessitated two fairly intensive and very different field expeditions. The first took place in March 2013, where we lived in ‘cozy’ kunks by the edge of the frozen lake. At this time we co-operated with Swiss and Russian scientists on their long-term Lake Baikal sedimentation monitoring programme. We analysed d30Si of dissolved silica from different water depths d30SiDSi as well as the d30Si composition of diatoms (d30Sidiatom) from open sediment traps deployed between 2012-2013. In July-August 2013 we also collected samples for d30SiDSi from major Baikal tributaries (especially the Selenga River which provides the majority of riverine inflow to the lake) and from water samples across the lake itself. These data are currently being analysed to assess the impact of human alteration of Lake Baikal’s catchment. During both fieldtrips a number of sediment cores were extracted from the bottom of Lake Baikal from each of its three basins using a Uwitek corer. These are currently being dated using the unstable radioisotope 210Pb so that any changes in the past 150 years linked to pollution and / or global warming can be accurately dated.

Figure 4.  Coring on the surface of Lake Biakal.

Figure 4. Coring on the surface of Lake Biakal.

Results are currently being written up for publication. But they will be presented at three up-coming conferences: the AGU (Session: Biogeochemical Cycling of Silicon and Isotopes in Biogenic Silica, San Francisco. December 2014), ASLO (Recent Ecological Change in Ancient Lakes, Grenada, Spain. February 2015) and the next Isotopes in Biogenic Silica (IBiS) meeting,  to be held in London, May 2015.  The authors gratefully acknowledge UK NERC (NE/J010227/1) for funding this research programme.

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About downwithtime

Assistant scientist in the Department of Geography at the University of Wisconsin, Madison. Studying paleoecology and the challenges of large data synthesis.
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One Response to Reconstructing pollution histories in the Lake Baikal basin: an application of silicon isotope geochemistry

  1. Pingback: A view from the field. | OpenQuaternary Discussions

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