Blue-green algae record at Altmühlsee: Bathing ban endangers tourism!

Blue-green algae record at Altmühlsee: Bathing ban endangers tourism!

The bathing season around the Altmühlsee is under an unfavorable star. SPD member of the state parliament Harry Scheuenstuhl expresses his concern about the alarming situation in the popular recreational water. In 2024 there were massive occurrences of blue-green algae, which, according to the Nuremberg News led to the beaches being closed on 50 of 139 bathing days. The warnings and bathing bans from the Weißenburg-Gunzenhausen health department have been a constant companion for those who love swimming ever since. This situation could lead to the Altmühlsee being deregistered as an EU bathing water if the high blue-green algae concentrations continue.

Another worrying news: a record concentration of 260 micrograms of blue-green algae per liter was measured in 2024. These are values ​​that exceed the long-term average many times over and trigger bathing warnings from 15 micrograms and bathing bans from 75 micrograms. That reports BR. This summer, for the first time, there was a ban on swimming at the Schlungenhof surf center, a circumstance that unsettled both locals and guests.

Causes and effects

The problem is not new, but has been building up over years. The main cause is nutrient inputs from agriculture, which are exacerbated by heavy rain. Phosphorus and nitrogen from fertilized soil and sewage sludge enter the Altmühlsee, which promotes the growth of cyanobacteria. Experts estimate that around 40 tons of phosphorus enter the lake every year, a third of which comes from sewage treatment plants. These findings are essential to develop effective measures to improve water quality.

The Bavarian Farmers' Association reports progress through stricter fertilizer regulations. Farmers are encouraged to leave unfertilized strips of water bodies, and there is increasing participation in contracted nature conservation programs to maintain meadows without fertilizer. But is that enough to defuse the situation? A holistic approach is needed to break the downward spiral, demands Scheuenstuhl. Measures such as dredging and the renovation of sewage treatment plants are already showing progress, but there is still a lot to do.

Climate change as another factor

In addition to human influences, climate change is exacerbating the problem. The water temperatures in the Altmühlsee have increased by four degrees in the last 40 years, which promotes the growth of blue-green algae. According to an analysis by biologists at the Technical University of Munich, the increase in blue-green algae in swimming lakes has increased significantly worldwide. Climate change is changing the conditions in the waters and contributing to the criticality of the situation daily news reported.

The negative effects on tourism and the local economy are noticeable. In the summer of 2024 in particular, there was a decline in overnight stays in the Franconian Lake District of around 1% compared to the previous year. Gastronomy, retail and leisure providers are suffering from the low number of visitors. Even the fishing association has noticed declining sales of fishing licenses, which is alarming for the region.

In order to improve the situation, Scheuenstuhl is calling for close cooperation with agriculture to ensure clean water and avert further bathing bans. The hope for early solutions remains, not only for nature lovers, but also for all those who value the quality of life and the tourism economic value of the Altmühlsee.