Archive of Blue-green algae bulletins

Note: This is an archived report.
You can access the latest blue-green algae bulletin here.

Published 25.7.2024

The blue-green algae situation has remained stable in inland waters, and slightly less blue-green algae have been observed than in previous monitoring years. Blue-green algae observations have increased on the coasts, and plenty of observations have also been made in the Bothnian Sea and the Åland Sea.

The number of blue-green algae observations on inland waters made through national blue-green algae monitoring has not changed much since last week. Despite the current hot period, blue-green algae observations have been slightly fewer than is typical of the season. Very abundant algae have been observed at one national blue-green algae monitoring site in South Karelia. Abundant blue-green algae have been detected at seven monitoring sites, and some blue-green algae have been detected at 26 monitoring sites. Blue-green algae observations still mainly occur in Southern and Central Finland, but individual observations have been made everywhere in Finland, up to northern Lapland.

The number of blue-green algae observations in the coastal area has increased slightly since last week, and blue-green algae are slightly more abundant than in the previous years of national monitoring (1998–2023). Blue-green algae have been observed at 33 national blue-green algae monitoring sites. Very abundant algae were detected at one observation site in Southwest Finland. Large amounts of blue-green algae were observed in 12 sites and some blue-green algae in 20 of them. Blue-green algae were observed mainly on the coasts of Southwest Finland and Uusimaa, but observations were also made on the coasts of Åland, Satakunta, Ostrobothnia and North Ostrobothnia.

In the Bothnian Sea, the number of blue-green algae has increased significantly both in the open sea and in coastal areas. The number is large considering the season. The number of blue-green algae has also increased in the Åland Sea. The surface waters in the Gulf of Finland have warmed up by several degrees. In addition to warm weather, cool water has not been able to reach the surface due to the lack of wind. Nevertheless, the blue-green algae situation has remained stable. Observations have been made, for example, between Porkkala and Tammisaari and at the entrance to the Gulf of Finland.

In addition to official monitoring, information on the blue-green algae situation is also gathered from the public. A total of almost 190 observations made by citizens were obtained through the Lake-seawiki and Vesi.fi this week. Blue-green algae were found in around 140 of them.