Berlin issues blue-green algae warning for 2 Havel River swimming spots

Berlin health authorities have issued a warning against swimming at two popular spots along the Havel River following a massive bloom of blue-green algae (blaualgenmassenentwicklung). People in the capital planning a day by the water will now need to dodge a couple of murky locations.

High algae concentrations prompt rescue and toxin warnings

Official warnings are currently active for the Breitehorn swimming spot in Spandau and the Radfahrerwiese area in Steglitz-Zehlendorf. The State Office for Health and Social Affairs (Lageso) confirmed that both sites along the Havel River are experiencing a massive growth of cyanobacteria, commonly known as blue-green algae.

The rapid proliferation has caused water visibility to drop below 0,5 metres. Lageso noted that such murky conditions make emergency water rescue operations significantly more difficult. Following guidelines from the Federal Environment Agency (UBA), health officials have initiated additional testing for algae toxins at both Breitehorn and Radfahrerwiese.

Heat drives blooms, but 37 other Berlin spots remain safe

Cyanobacteria thrive when water temperatures rise alongside high levels of sunlight. Heavy rainfall followed by extended warm weather can cause sudden shifts in water quality, creating ideal conditions for algae to multiply rapidly across freshwater bodies.

Fortunately for local swimmers, the remaining 37 official bathing spots across the capital remain safe to visit. Lageso regularly monitors all 39 designated swimming areas in Berlin throughout the season, conducting microbiological measurements for bacteria like Escherichia coli and intestinal enterococci to ensure water safety.