Blue-green algae warning in the Schultheis pond: bathers beware!

Blue-green algae warning in the Schultheis pond: bathers beware!

There has been a significant occurrence of cyanobacteria, also known as blue-green algae, in the Schultheis pond in Offenbach. The health department assessed the situation on June 25, 2025 with the monitoring level of “increased attention”. Bathers and residents should be careful. Signs have already been installed on site warning of the presence of these microorganisms, which can pose health risks in certain conditions. In particular, it is advisable to avoid cloudy, greenish water or visible algae carpets, as these are signs of increased algae growth. This is especially true for small children, who could swallow large amounts while playing in the water.

Particular caution is required as some types of blue-green algae can produce toxic substances called cyanotoxins, which can cause nausea, diarrhea or other symptoms. In individual cases, skin contact can also cause skin or mucous membrane irritation, especially in sensitive people. Reassuring news: visible cyanobacteria only pose a serious risk when large amounts of water are ingested, which should not be the case for most bathers.

Growing concern about water quality

The swimming season at Schultheis-Weiher runs from May 1st to September 15th, during which time a lifeguard ensures additional safety. The water quality is checked regularly in order to counteract health risks at an early stage. According to information from the Federal Environment Agency Health risks can arise during the bathing season due to increased concentrations of cyanobacteria in bathing water. It should also be noted that high temperatures and stable weather conditions are favorable factors for the spread of these algae.

Interestingly, satellite-based evaluations of lakes in Germany show that although there are no clear trends in cyanobacteria pollution, very warm summers can increase the likelihood of heavily polluted waters. Climate change could play a crucial role here. The main cause of rampant algae growth is high nutrient content, particularly total phosphorus, which is often due to over-fertilization.

Recommendations and measures

In order to minimize the health risks for bathers, the Institute for Water, Soil and Air Hygiene of the Federal Environment Agency has made various recommendations in a federal health bulletin. These include:

1. Sicherung der Badewasserqualität gemäß den EG-Richtlinien durch präventive Maßnahmen.
2. Vermeidung von Gesundheitsrisiken durch Sofortmaßnahmen.

In summary, the topic of blue-green algae is a serious problem in many natural bodies of water, not just in Offenbach. Many bathing areas in Germany are struggling with similar problems, although according to... Technical reports Around half of these bathing areas do not have a visibility depth of more than one meter. This ultimately represents a significant health risk, especially for immature bathers.

As a swimmer and water sports enthusiast, it is important to be vigilant, take local advice seriously and find out about the water quality. This is the only way to keep summer by the water carefree and healthy!