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Swimming possible in almost all Berlin lakes despite blue-green algae


A paddle boat crosses the carpet of blue-green algae in Lake Stößensee, which is fed by the Havel River.

Blue-green algae are currently turning many swimming lakes in Berlin a striking green. However, the vast majority of official swimming spots are still suitable for swimming and bathing, the State Office for Health and Social Affairs (Lageso) announced on request.

According to the Lageso, the amount of algae is completely normal for late summer. "At the moment, we only advise against swimming at the Schmöckwitz swimming site," a spokeswoman said on Wednesday.

Intensity of color not an indicator of toxic effect

Blue-green algae are actually bacteria. According to urban nature expert Derk Ehlert, the bacteria rise from the bottom of the soil to the surface during the day. "There they perform photosynthesis and are visible to us as a thick green broth." The prerequisites for this, he said, are a high nutrient content in the water, warm weather and high water temperatures, as well as sunshine. In the evening, the bacteria would then sink again. The blue-green algae currently appearing in Berlin waters have a low toxic effect, Ehlert explained. "But that can change quickly because there are many thousands of bacteria." The intensity of the green color, however, has nothing to do with how toxic the bacteria are, he said.

Swimmers advised to change out of swimwear after bathing

At lakes that are still suitable for bathing, the Lageso recommends not to bathe in areas with visible green or blue-green streaks or alage "carpets", especially for children. After bathing, it is advisable to change out of and rinse your swimwear - and to take a shower. Information about water quality is available online on the Lageso website in the "Gesundheit" section. According to the authority, there have been individual reports of gastrointestinal complaints as well as irritation of the respiratory tract, skin and mucous membranes in connection with blue-green algae.

Author: dpa/
Further information: Swimming lakes in Berlin
Publication date: 7 September 2023
Last updated: 7 September 2023

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