Rates of change in physical and chemical lake variables – are they comparable between large and small lakes?
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Changes over time in 16 physical and chemical variables were analysed and compared between Sweden’s largest lakes, Vättern and Vänern, and 48 smaller Swedish reference lakes during spring over the period 1984–2003. The rates of changes varied substantially among lakes and among variables, and they were clearly influenced by changes in both climate and atmospheric deposition. Rates of change of variables associated with atmospheric deposition such as sulphate concentrations were dependent on lake morphometry. This also applied to the rates of change of variables associated with climate change effects in the catchment such as calcium and magnesium concentrations. However, climate change effects could also be comparable between large and small lakes. Rates of change in physical and chemical variables directly influenced by the climate via the lake water surface, e.g., surface water temperature, and variables associated with the spring phytoplankton development such as phosphate–phosphorus and nitrate–nitrogen concentrations, were similar and therefore independent of lake morphometry. This study shows that climate change effects that act via the lake surface can be of the same order of magnitude among large and small lakes, but climate change effects that act via the catchment differ substantially in large lakes. It is essential to differentiate between these two types of climate effects in order to assess the impacts of climate change and the adaptation and vulnerability of lake ecosystems.
KeywordsClimate Atmospheric deposition Water chemistry Spring phytoplankton development Lake volume
This work was partly funded by the European Union within the framework of the European Commission projects CLIME (“Climate and Lake Impacts in Europe”, EVK1-CT-2002-00121 and Euro-limpacs (“Integrated Project to Evaluate the Impacts of Global Change on European Freshwater Ecosystems”, GOCE-CT-2003-505540). The author is a research fellow of the Royal Swedish Academy of Sciences supported by a grant from the Knut and Alice Wallenberg Foundation. Funding was also received by the Swedish Research Council (621-2005-4335). The author is grateful to the Swedish Environmental Protection Agency and the IMA laboratory for financing, sampling and analyzing numerous water samples.
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