Record heat triggers rapid spread of toxic blue-green algae in the Baltic Sea
Prolonged heat has caused a sharp rise in toxic blue-green algae along Germany's Baltic coast and in several northern German lakes, prompting swimming bans and public warnings.
Extensive blooms of blue-green algae, or cyanobacteria, have formed in the Baltic Sea off Germany's coast, with similarly hazardous blooms also reported in numerous lakes across northern Germany, according to Euronews.
In the state of Schleswig-Holstein, swimming bans are already in place at several lakes, while people are being urged to exercise extra caution along parts of the Baltic coastline. Health authorities near Rostock are also advising residents to avoid swimming in areas where toxic cyanobacteria have been spotted.
Heat has created ideal conditions
Experts explain that prolonged heat, strong sunshine and calm weather, combined with high water temperatures, are driving the rapid proliferation of the bacteria. High nutrient levels in the Baltic Sea are further fueling the blooms.
Although commonly called blue-green algae, these organisms are actually bacteria, and some species release toxins that are dangerous to both humans and animals. Contact with contaminated water can cause skin irritation and allergic reactions, while swallowing it may lead to nausea, vomiting and other gastrointestinal problems. Particular caution is urged for children, and dog owners are warned never to let their pets drink water where the bacteria have been observed.
Conditions can change quickly
On the water's surface, the bacteria typically appear as greenish or bluish streaks, a film, or a dense "mat." Because wind and currents strongly influence their spread, conditions along the coast can worsen within just a few hours.
Satellite imagery from the EU's Copernicus Earth observation programme showed extensive greenish clusters in early August in the Arkona Basin, the waters between southern Sweden, Denmark's Møn island and Germany's Rügen island.
Experts note that not every green patch in the water indicates toxic algae, but that danger cannot be judged by appearance alone. If water appears strongly green or cloudy, or a dense algal mass is visible, it is advisable to avoid swimming and to follow warnings from local health authorities.
