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www.biogeosciences-discuss.net/5/3457/2008/
doi:10.5194/bgd-5-3457-2008
© Author(s) 2008. This work is distributed
under the Creative Commons Attribution 3.0 License.
Methane dynamics in different boreal\newline lake types
1Department of Biology, University of Joensuu, Finland
2Finnish Environment Institute, Helsinki, Finland
3Department of Environmental Sciences, University of Kuopio, Finland
4Finnish Forest Research Institute, Joensuu Research Unit, Finland
*now at: Environmental Studies Program, Mount Holyoke College, South Hadley, MA, USA
Abstract. This study explores the variability in concentrations of dissolved CH4 and annual flux estimates in the pelagic zone in a statistically defined sample of 207 lakes in Finland. The lakes were situated representatively in the boreal zone, where the mean annual air temperature ranges from −2.8 to 5.9°C. We examined how lake CH4 dynamics related to regional lake types assessed according to the EU water framework directive. Ten lake types were defined on the basis of water chemistry, color, and size. Lakes were sampled for dissolved CH4 concentrations four times per year, at four different depths at the deepest point of each lake. We found that CH4 concentrations and fluxes to the atmosphere tended to be high in nutrient rich calcareous lakes, and that the shallow lakes had the greatest surface water concentrations. CH4 content in the hypolimnion was related to oxygen and nutrient concentrations, and lake depth or area. The surface water CH4 concentration was related to the depth or area of lake. Methane close to the bottom can be viewed as proxy of lake status in terms of frequency of anoxia and nutrient levels. Median CH4 release from randomly selected lakes was 45 mmol m−2 a−1. Shallow lakes had the highest median CH4 effluxes, with the clear shallow lake type having the smallest median. Our data, combined with other studies, suggest that lake surface area could be used for an approximation of CH4 release from lakes. Shallow small lakes common in boreal and arctic landscapes may have disproportional significance with respect to CH4 release.
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Citation: Juutinen, S., Rantakari, M., Kortelainen, P., Huttunen, J. T., Larmola, T., Alm, J., Silvola, J., and Martikainen, P. J.: Methane dynamics in different boreal\newline lake types, Biogeosciences Discuss., 5, 3457-3496, doi:10.5194/bgd-5-3457-2008, 2008. Bibtex EndNote Reference Manager XML
