Archive of Blue-green algae bulletins

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Published 13.7.2023

Warm weather has increased the number of blue-green algae observations in inland waters and sea areas

Observations on blue-green algae have increased this week, as a result of warm weather, both in inland waters and at sea. For example, the summer’s first larger blue-green algae observations have been made in the Bothnian Sea. In open sea areas, blue-green algae surface blooms have been observed especially south of Åland and in the eastern parts of the Gulf of Finland.

The period of warm weather that started after the cool and rainy week has increased the number of blue-green algae observations in both lakes and on the coast. This week yielded more blue-green algae observations than is typical of the season. Blue-green algae observations have also been made by citizens all around Finland.

Very abundant blue-green algae have been observed at two, abundant blue-green algae at eight and some blue-green algae at 51 inland water observation sites across Finland. The northernmost observation of blue-green algae monitoring is from Kemijärvi. The northernmost citizens’ observation is from Muonio.

For the coastal observation sites, abundant blue-green algae have been observed at seven sites and some blue-green algae at 25 sites. The observations mostly occurred in the region from the Gulf of Finland to the Bothnian Sea, but some blue-green algae have also been observed in the Bothnian Bay near Oulu.

During the past week, the first larger-scale blue-green algae observations were made in the southern parts of the Bothnian Sea. Blue-green algae have also been found in the Sea of Åland, the main basin of the Baltic Sea and the Gulf of Finland. Blue-green algae surface blooms occur especially south of Åland and east of Helsinki, all the way to the coast of the Gulf of Finland.

The warmer waters promote the growth of blue-green algae, as a result of which the number of blue-green algae observations is likely to increase over the next few days due to the continuous warm and sunny weather.

 

The information on this page was produced by the Finnish Environment Institute (Syke).