Satellite image of the Baltic Sea from July 16. The green-blue streaks and eddies are carpets of algae
The DLRG had to issue an absolute bathing ban on the beaches of the Baltic Sea resort of Eckernförde on Sunday. The reason is a carpet of blue-green algae that has been driven into Eckernförde Bay by the easterly winds of the past few days.
Actually, it is not about algae, but about cyanobacteria. These occur regularly in the Baltic Sea in summer, they multiply vigorously, especially in light wind, sunny weather, as has been the case in recent weeks, and then die off. The dead bacteria float across the Baltic Sea as large blue-green carpets. Some of the cyano strains develop strong neurotoxins which can lead to allergic reactions, nausea if swallowed and in the worst case to liver damage and death.
Since the algae carpets are driven by wind and currents, it is difficult to predict future developments on German beaches.
The Swedish Hydrographic Institute provides information on the current status at this link.