, Volume 12, Issue 6, pp 944-960
Date: 10 Sep 2009

Paleolimnologic Evidence for Recent Eutrophication in the Valley of the Great Lakes (Mongolia)

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Climate warming and major land-use changes have profoundly affected the Mongolian landscape in the past several decades. Previous studies have recognized the impacts of a warmer, more arid climate and Mongolia’s 1991 transition from a command to a market economy on terrestrial ecosystems, including impaired sustainability of subsistence herding and threats to wild animals. In this study, we examined the combined effects of changing climate and herding practices on lake eutrophication in Western Mongolia. We sampled 65 lakes for modern nutrients and found the majority of lakes were eutrophic to hyper-eutrophic. Sediment cores were taken from five of the lakes to compare current lake status to paleolimnologial measures of lake eutrophication over the past 100–2000 years, including changes in diatom assemblages, diatom-inferred total phosphorus, biogenic silica, organic matter, and sediment accumulation rates. Variance partitioning analysis showed that recent shifts in diatom assemblages were related to changes in both climate and herding practices. The results presented here demonstrate a need for further study and long-term monitoring of water quality in Mongolia to understand the complicated interactions of climate and land use on aquatic resources and to preserve water quality in this remote and ecologically important region.

Author Contributions

ALCS carried out diatom analysis, statistical analysis of the data and paleo-environmental reconstructions, 210Pb dating, assisted in sediment core collection, and took primary responsibility for writing of the manuscript; JEA was a co-P.I. for the project and also collected water samples and carried out analysis, quality control, and synthesis of the water chemistry data; CEU led sediment core collection and headed sediment analyses including loss-on-ignition and biogenic silica analyses; MBE was a co-P.I. for the project and contributed to sediment core collection, data interpretation, and writing of the manuscript; and NS identified sampling sites, coordinated field logistics, and assisted with water and sediment sample collection.