Chemical stratification and stability of meromictic lakes in the Upper Romerike district |
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| Authors: | Dag Hongve |
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| Institution: | (1) Present address: Section of Limnology, University of Oslo, Blindern, P.O. Box 1027 N-Oslo 3, Norway |
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| Abstract: | A number of lakes in Southeast Norway have developed biogenic meromixis and have typically also considerable concentrations
of dissolved iron and manganese in the bottom waters. Eight such lakes are described. Products of biological decomposition
like carbon dioxide, methane and some inorganic salts gave a difference in density between mixo- and monimolimnion and hence
chemical stability to the lakes. The concentration of iron and manganese gave minor contributions to the density gradients,
and these substances are regarded as less important for the stability because of their reduced solubility under oxic conditions.
Quantitative expressions of wind influence on lake surfaces were obtained by calculation of the work of the wind during the
heating season. These values were low compared with a more exposed lake in the same region. Water movements generated by the
wind have eroding effects on the chemical stratification only during short periods of homothermy before icelaying. During
the rest of the year the monimolimnion is protected by either thermal stratification or ice cover. During the autumnal partial
circulation a substantial reduction in chemical stability took place. For some of the lakes it is assumed that full circulation
may take place in years with favourable weather conditions. |
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