Archive of Blue-green algae bulletins

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

Published 1.8.2024

Unstable weather has reduced blue-green algae blooms since last week. Cooled and rainy weather and winds have mixed the water mass and reduced blue-green algae blooms in open sea areas, especially in the Gulf of Finland. The number of blue-green algae on the coast and inland waters has also decreased compared to last week, but individual abundant blue-green algae deposits are still visible.

Less blue-green algae have been observed at national blue-green algae monitoring sites in inland waters than is typical of the time. Unstable weather reduces the abundance of blue-green algae, mixes blue-green algae mass with water and reduces the formation of blooms. No very abundant blue-green algae were observed at national blue-green algae monitoring sites. Abundant blue-green algae have been detected at seven monitoring sites, and some blue-green algae have been detected at 18 monitoring sites. Blue-green algae observations are mainly found in Southwest Finland, Uusimaa and Pirkanmaa, but individual observations have also been made in different parts of central Finland.

The blue-green algae situation on the coast is quite typical of the season, and the number of blooms has decreased since last week. Blue-green algae have been observed at 24 national blue-green algae monitoring sites. Abundant blue-green algae were observed in three sites and some blue-green algae in 21 of them. Blue-green algae were observed mainly on the coasts of Southwest Finland, but observations were also made on the coasts of Uusimaa, Kymenlaakso, Satakunta and Ostrobothnia.

The algae situation has calmed down as a result of cooler and windy weather, especially in the Sea of Bothnia. At the weekend, the Gulf of Finland still had abundant blue-green algae at the eastern and western ends of the bay, along the coast on the Finnish side, and in the area extending from the Archipelago Sea to the northern Baltic Sea. However, at the beginning of the week, the blooms were mixed with water and dispersed, and hardly any algae have been detected. Minor amounts have been observed, e.g., in the vicinity of Utö and Jurmo and on the western bay of Hanko. In places, cloudiness has prevented obtaining extensive satellite observations.

In addition to official monitoring, information on the blue-green algae situation is also gathered from the public. A total of 34 observations made by citizens were obtained through the Lake-seawiki and Vesi.fi this week. Blue-green algae were found in 11 of them.