12 August 2022, Mecklenburg-Western Pomerania, Greifswald: A so-called algae carpet floats in the Eldena lido in Greifswald. Blue-green algae have been detected at the Eldena lido in Greifswald (district of Vorpommern-Greifswald). On the same day, the health-damaging cyanobacteria were discovered and a bathing warning was issued. They can be recognized by the bluish-green turbidity of the water, the formation of streaks and algae carpets on the surface. The midsummer weather favors the growth of blue-green algae on the Baltic coast. Photo: Stefan Sauer/dpa