Blue-green algae in water bodies

Symbolbild Schmerikon

The Office for the Environment has examined water samples of several water bodies in SG, TG, and ZH, and confirmed the presence of blue-green algae. These might be widespread, potentially dangerous species that could form blue-green algae toxins. These toxins can be dangerous to humans and animals.


The blue-green algae have only been detected in definable areas of lake Constance and lake Zurich.


Blue-green algae develop mainly at higher temperatures and in stagnant waters – such as in the harbor basin in Horn. If the toxic algae develop, the water becomes discolored.

Most recently, blue-green algae made headlines when five dogs died at the lake in Schmerikon in July.

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