Archive of Blue-green algae bulletins

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

Published 29.6.2023

The blue-green algae situation has deteriorated significantly in inland waters and coastal areas, also abundant blue-green algae in sea areas

Blue-green algae observations in lakes and coastal areas have doubled since last week, as a result of warm weather. Observations have even been made in the northern parts of the country. Abundant amounts of subsurface blue-green algae have also been observed in Finland’s open sea areas, and some of the blooms have already surfaced in the Gulf of Finland.

Due to warm weather conditions, the number of blue-green algae observations has increased significantly since last week. This week, blue-green algae observations have been made in both inland waters and coastal areas, significantly more than typical for the time period. Compared to earlier, blue-green algae have now also been found in the northern parts of the country.

At inland water and coastal observation sites, blue-green algae observations have doubled compared to last week. Citizens have also reported blue-green algae observations, in various parts of Finland.

Seven inland water observation sites have had abundant blue-green algae, while some blue-green algae have been observed at 42 sites, across Finland. The northernmost observation is from Posio, in Southern Lapland. For the coastal observation sites, abundant blue-green algae have been observed at five sites and some blue-green algae at 15 sites. The northernmost coastal observations are off the coast of Oulu and Ii, both of which have had abundant algae.

Satellite images have revealed abundant amounts of subsurface blue-green algae in the open sea areas in the Gulf of Finland, the main basin of the Baltic Sea and the Sea of Åland. In the Gulf of Finland, the blue-green algae areas have expanded and moved closer to the Finnish coast, during the week. Some of the blue-green algae have already reached the surface, in the area extending from the mouth of the Gulf of Finland to Gogland.

The slightly cooler summer weather forecast for the next few days, may restrain the development of blue-green algae blooms. Then again, showers and thunderstorms forecast in part of the country, may increase the nutrient load discharged into water systems and increase the abundance of blue-green algae blooms.