Climate change
Analysis shows: Lake Constance is getting warmer
“We don’t know much yet, but there are initial indications,” says the head of the research center, Alexander Brinker. Photo
© Felix Kästle/dpa
Lake Constance is not yet inviting for swimming, but an analysis shows that the water is getting warmer. Climate change is leaving its mark – the effects are already noticeable.
Last year, the average was 13.6 degrees. The Langenargen Lake Research Institute of the Baden-Württemberg State Office for the Environment (LUBW) has been measuring the water temperature in the lake since 1962. Back then, it was still 10.5 degrees on average.
The consequences of climatic warming on water bodies are very diverse, explained an expert from LUBW. Temperature is a key parameter for the condition of water bodies. “It influences the mixing and stratification conditions of the lakes, the water chemistry or the species composition and the impact pathways of the food webs.”
“Seewandel” project
In Lake Constance, warming is accompanied by a weak exchange of deep water with surface water. This reduces the transport of oxygen from the surface layer to the depths and thus increases the risk of oxygen deficiency for the organisms living there. “Conversely, fewer nutrients are transported from the depths to the surface layer, which influences the lake’s ecosystem via the food web.”
The impact of climate change on fish populations and aquatic plants in Lake Constance is currently being investigated in more detail in the “Lake Change Climate” project. The project will run for three years until 2026. However, there are already initial indications of the effects.
Temperatures also rise at depth
“We don’t know very much yet, but there are initial indications,” said the head of the research center, Alexander Brinker, in Langenargen. The higher temperature has a negative effect on the burbot, for example. “For them, the water in the deep area has to be colder than five degrees, otherwise the eggs cannot develop properly.” The temperature in that area is already higher, however, which leads to lower catch numbers.
According to an analysis by the Maritime Research Institute, the average annual temperature at depth in 2023 was 5.4 degrees. This is a new high. Ten years ago it was 4.3 degrees. The temperature is rising from year to year.
Whitefish eggs and larvae are also affected by rising temperatures. The researchers assume that there is a higher mortality rate for eggs and larvae when it is too warm. And there are fears that adult whitefish will no longer swim into these areas in the summer, when they normally feed on water fleas in the light-flooded areas on the lake surface, because the water is too warm. “They can no longer get to their hunting grounds.”
Trout farming also affected
According to a new study by the Langenargen Fisheries Research Center, higher temperatures outside Lake Constance are having an impact on local trout farms, which get their water from adjacent rivers or springs. For the trout, which depend on cold and oxygen-rich water, higher temperatures mean stress.
They would lead to a reduction or cessation of food intake and an increased susceptibility to disease. In extreme cases, the animals would die. “In summary, by the end of the century between 37 and 77 percent of current trout farms will find themselves in unfavorable climatic conditions,” says the research team.