Archive of Blue-green algae bulletins

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

Published 27.6.2024

Warm weather has increased blue-green algae observations in inland waters, on the coasts and in the Gulf of Finland area

The number of blue-green algae observations has increased since last week. As a result of the warmer weather, the occurrences of blue-green algae in inland waters are slightly above average for the time of year. There has been a significant increase in blue-green algae observations in the Gulf of Finland and in the northern part of the Baltic Proper.

The number of blue-green algae observations has increased in inland waters since last week. In Southern, Eastern and Western Finland, seven of the inland sites in the national blue-green algae monitoring programme have observed high levels of blue-green algae. There have been observations of some blue-green algae at 34 inland water observation sites in Southern and Central Finland. As a result of the warmer weather, the occurrences of blue-green algae in inland waters are slightly above average for the time of year. Towards the weekend, however, more unstable weather is likely to curb the abundance of blue-green algae and reduce the formation of blooms.

There have also been slightly more blue-green algae in coastal areas than is typical for the time of year. Blue-green algae have been observed at 21 of the national blue-green algae monitoring sites, with high algae counts at two sites and lower counts at 19 sites. Blue-green algae were mainly observed along the coasts of Southeast, Southern and Southwest Finland.

This week, cloud cover has not limited satellite observations of blue-green algae in open sea areas. Over the weekend, satellites observed blue-green algae on the water surface in the Gulf of Finland, and mixed with the water in the northern part of the Baltic Proper. Since the beginning of the week, algae have also been present on the surface in some places in the Archipelago Sea. No blue-green algae have been observed in the Bothnian Sea. In Tuesday’s satellite image, blue-green algae can be seen throughout the Gulf of Finland, from off Kotka to off Helsinki and all the way to the southern parts of the Archipelago Sea. In the eastern Gulf of Finland in particular, extensive blue-green algae accumulations have been observed in surface waters.

In addition to official monitoring, information on the blue-green algae situation has also been gathered from the public. The number of observations by the public and other observations outside official monitoring via Järvi-meriwiki and Vesi.fi has increased since last week. In the current week, a total of around 300 observations by members of the public have been received.