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.