Archive of Blue-green algae bulletins

Note: This is an archived report.
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Published 26.6.2025

Unstable weather has kept the blue-green algae situation calm

The blue-green algae situation continues mostly calm, and observations in inland waters and coastal areas have remained minor. The unsettled weather of the past week has hampered satellite observations in offshore areas. However, based on automatic observations made by merchant vessels, the amount of blue-green algae has been slightly elevated in the open sea areas in the western part of the Gulf of Finland.

Unstable weather has kept the blue-green algae situation calm this week. During the past week, no abundant blue-green algae have been observed at the inland water observation sites of the national blue-green algae monitoring. Some blue-green algae have been observed at a total of 15 inland water observation sites in South and North Karelia, South and North Savo, Central Finland, Pirkanmaa and South Ostrobothnia.

In coastal areas, the number of blue-green algae observations has not changed much since last week. Abundant algae have been observed at one observation site in Kymenlaakso.  Some blue-green algae have been observed at one coastal observation site in Southwest Finland.

Due to unstable and cloudy weather, no comprehensive satellite observations have been obtained from the open sea areas, this week. However, resuspension has been observed in the inner water bodies on the west coast, i.e. the winds and waves have raised the matter from the bottom to the surface. Material that has risen into the surface causes turbidity when mixed with the water.  Based on automatic observations made by merchant vessels, the amount of blue-green algae mixed with water is slightly elevated in the open sea areas in the western part of the Gulf of Finland.

In addition to official monitoring, valuable information on the blue-green algae situation is also gathered from the public. This week, a total of 49 observations made by citizens were obtained through the Lake-seawiki and Vesi.fi.