Early weeks’ wind and rain have mixed the blue-green algae, observed in the southern part of the Archipelago Sea a week ago, into the entire water layer. On the left, blue-green algae in the layers close to the surface, on the right, wind-induced waves in the same area.


Cool and rainy weather in Finland has had a positive impact on the blue-green algae situation in lakes and along the coast. Observations of blue-green algae in both inland waters and coastal areas have been below average this week, thanks to the unfavorable conditions for their growth. The recent rainfall and wind have mixed the blue-green algae, which were previously observed in the southern part of the Archipelago Sea, throughout the entire water layer.

The Finnish Environment Institute (Syke) and various local authorities collaborate to monitor cyanobacterial occurrences as part of their environmental monitoring efforts. This monitoring involves approximately 400 observation sites across the country, covering inland and coastal waters, as well as the archipelago. The data collected provides an overview of the cyanobacterial situation in different water bodies.

Information about cyanobacterial occurrences in open sea areas is primarily obtained from satellite images. Additional information is gathered from sources such as the Finnish Border Guard, the research vessel Aranda, the Utö Atmospheric and Marine Research Station, and cruise and merchant ships equipped with Alg@line measuring equipment. Drift forecasts for cyanobacterial rafts in open sea areas are prepared in collaboration with the Finnish Meteorological Institute's Maritime Services.

Cyanobacterial occurrences can pose health hazards, as these organisms produce various compounds that can cause symptoms. While some cyanobacteria can generate liver or nerve toxins, other compounds may also contribute to the symptoms experienced by swimmers. It is particularly important to keep young children and pets away from water containing cyanobacteria. This water should not be used for saunas, washing, or irrigation.

If poisoning is suspected, it is advisable to seek medical advice or take affected pets to a veterinarian. The Poison Information Centre can provide additional guidance if needed. Municipal health authorities monitor cyanobacterial situations on beaches to ensure public safety.

To enhance the monitoring efforts, individuals are encouraged to report cyanobacterial observations through platforms like Järvi-meriwiki (Lake and Sea Wiki) and the smartphone-friendly Havaintolähetti website. These observations are displayed on the national cyanobacterial observation map, helping to assess the overall algal situation. It is equally important to report the absence of cyanobacteria, as these observations contribute valuable data.

Järvi-meriwiki is an online service developed in collaboration with authorities and citizens. It provides comprehensive information about lakes larger than one hectare and different areas of the Baltic Sea. Users can share photos and other observations, supporting a collective effort to monitor and understand water ecosystems.

Cyanobacterial maps are available on the MarineFinland.fi and Waterinfo.fi websites, combining observations reported to Järvi-meriwiki, observations from the City of Helsinki's beaches, and satellite interpretations by Syke over the past three days.

The current cool and rainy weather has played a vital role in maintaining a calm blue-green algae situation in Finnish lakes and coastal areas. Continued monitoring and public engagement are crucial to ensuring the ongoing health and safety of these water ecosystems.