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Climate change weakens the purification function of lakes
https://www.unibas.ch/en/News-Events/News/Uni-Research/Climate-change-weakens-the-purification-function-of-lakes.htmlLakes play a vital filtering role in the ecosystem: they remove excess nitrogen from the water. An international research team led by the University of Basel and Eawag has now shown that climate change could weaken this natural purification process. This would have consequences extending all the way to coastal marine ecosystems.
25 May 2026 | Catherine Weyer
When we think of lakes, fish and frogs often come to mind, along with birds on the shore or places to swim. But lakes also play a central role in the global nitrogen cycle. Microorganisms convert nitrogen compounds such as nitrate or ammonia into dinitrogen gas (N₂), which is released to the atmosphere and effectively removed from the biosphere. This nitrogen removal process is called denitrification.
About 20 percent of natural nitrogen removal in inland waters is attributable to such processes. A new study led by the University of Basel and Eawag shows that this purification function is highly sensitive to warming caused by climate change. The results were published in "Nature Microbiology".
Filters are particularly active in winter
For their research, the scientists collected samples from Lake Baldegger in the Lucerne Lake District. The 5.3-square-kilometer lake is typical of many lakes in our latitudes, where the water completely mixes once a year.
The researchers showed that denitrification activity is closely linked to this seasonal mixing. In winter, the three water layers in Lake Baldegg mix completely: the warm, oxygen-rich surface water, the transition zone, and the cold, oxygen-poor deep water.
…
Callbeck, C.M., Mazzoli, A., Paulus, T.J. et al. Seasonality of lake microbial denitrification and its sensitivity to climate warming. Nat Microbiol (2026). https://doi.org/10.1038/s41564-026-02349-9
25 May 2026 | Catherine Weyer
When we think of lakes, fish and frogs often come to mind, along with birds on the shore or places to swim. But lakes also play a central role in the global nitrogen cycle. Microorganisms convert nitrogen compounds such as nitrate or ammonia into dinitrogen gas (N₂), which is released to the atmosphere and effectively removed from the biosphere. This nitrogen removal process is called denitrification.
About 20 percent of natural nitrogen removal in inland waters is attributable to such processes. A new study led by the University of Basel and Eawag shows that this purification function is highly sensitive to warming caused by climate change. The results were published in "Nature Microbiology".
Filters are particularly active in winter
For their research, the scientists collected samples from Lake Baldegger in the Lucerne Lake District. The 5.3-square-kilometer lake is typical of many lakes in our latitudes, where the water completely mixes once a year.
The researchers showed that denitrification activity is closely linked to this seasonal mixing. In winter, the three water layers in Lake Baldegg mix completely: the warm, oxygen-rich surface water, the transition zone, and the cold, oxygen-poor deep water.
…