Cyanobacteria in the sea or lakes can effectively spoil your summer vacation. This weekend, the weather is not very favorable for sunbathers and swimmers, but the water is usually clean. According to the Sanitary Inspectorate, you can safely, without fear of cyanobacteria, use all guarded bathing sites on the Baltic Sea and lakes in Pomerania, and the vast majority of bathing sites in the country.
Information on the state of bathing water, including the presence of cyanobacteria, is regularly provided by the Chief Sanitary Inspectorate. According to the latest data, on Sunday in all guarded bathing sites organized this summer in the Pomeranian Voivodeship – both those on the Baltic Sea and the lakes – the water is free from cyanobacteria that are harmful to health and can be used safely.
Also, almost all bathing areas in the rest of the country are free from cyanobacteria.
Cyanobacteria are dangerous. When not to bathe?
The Sanitary Inspectorate reminds you that in the case of cyanobacteria bloom, it is recommended that you do not enter the water. Bathing in water contaminated with cyanobacteria can cause unfavorable reactions of the body: from a rash on the skin to reddening of the conjunctiva. If such water is swallowed, gastrointestinal complaints including diarrhea, vomiting and abdominal pain may occur. Cyanobacteria are among the oldest organisms on Earth. They are found in both salt and inland waters, floating freely in them. During windless weather, some cyanobacteria may rise to the surface of the water and form a blanket there. They then look like spilled paint, jelly, or flakes floating on the surface of the water.
The inspectors remind us not to confuse cyanobacteria with macroalgae that may float near the water surface in the coastal zone of lakes or the Baltic Sea. Often the waves throw these green mats ashore, which, although they do not look aesthetically pleasing and may emit an unpleasant odor as a result of decomposition by bacteria, are not harmful themselves and are not a source of toxins.
What is favorable for cyanobacteria?
The seasonality of the cyanobacterial mass blooms is a natural phenomenon. Factors that influence the appearance of cyanobacterial water blooms include water temperature above 16-20 degrees Celsius (although cyanobacteria blooms and at lower temperatures are known – editorial note), the presence of biogenic salts (especially phosphates – editorial note), light wind and no rainfall. Predicting the occurrence of water blooms is very difficult because changing weather conditions, such as sunlight, wind or rain, are important here. Therefore, it is impossible to determine in advance when the cyanobacteria will appear and how long they will persist in a given body of water. As a rule, cyanobacteria can persist much longer in places sheltered from the wind, in bays where there is less wave and water mixing than in open space. Along the coast of Gdańsk Bay, the mass bloom of cyanobacteria can be recorded only on some beaches, and this is related to the direction and force of the wind, which can shift the surface bloom even within a few hours.
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