Elevated levels of coliform bacteria were detected only at the "Kleine Badewiese" swimming area on the Havel River. The swimming traffic light there is therefore set to "yellow." According to the information provided, swimming is still permitted, but warnings should be heeded. Blue-green algae have also been detected in Lake Tegel. According to the latest assessment, the risk to swimmers is low as long as they do not swallow any water, the State Office reported. The bathing traffic light remains "green" at all five affected locations. However, dogs should not enter the water there or come into contact with plant debris washed up on the shore. On behalf of the State Office for Health and Social Affairs, water samples from Berlin’s bathing areas are tested every two weeks for potential bacterial contamination, among other things. Water quality is then assessed using a traffic light system.