Archive of Blue-green algae bulletins

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

Published 8.8.2024

Somewhat more blue-green algae have been detected in inland waters and coastal areas than last week. Inland water observations have been made especially in the southern and western parts of the country, as well as along Central Finland. Slightly more blue-green algae have also been observed on the coast of Southwest Finland compared to last week. In the open sea, the blooms have become more prevalent on the south side of the Archipelago Sea.

Nutrients introduced to waters by heavy local showers and windless weather have increased the number of blue-green algae blooms in lakes in some places. Compared to last week, blue-green algae observations have been slightly more common at national blue-green algae monitoring sites in inland waters. There have been slightly more observations than is typical of late summer. Very abundant blue-green algae have been observed at four observation sites in Uusimaa, Southwest Finland and Päijät-Häme. Abundant blue-green algae have been detected at 16 monitoring sites, and some blue-green algae have been detected at 36 monitoring sites. Blue-green algae observations have mainly been made in the southern, central and western parts of the country, and the northernmost individual observations have been made in North Ostrobothnia and Kainuu.

The number of blue-green algae has also increased slightly in coastal areas since last week. Blue-green algae have been observed at 23 national blue-green algae monitoring sites. Very abundant algae have been observed at two of these monitoring sites in Southwest Finland. Abundant blue-green algae were observed at four sites and some blue-green algae at 17 of them. Blue-green algae were observed mainly on the coasts of Southwest Finland, but individual observations were also made on the coasts of Uusimaa, Kymenlaakso, Satakunta and Ostrobothnia.

In open sea areas, the blue-green algae situation has remained largely similar to last week, but the blooms have become more prevalent to the south of the Archipelago Sea. In the Archipelago Sea, algae are mainly mixed with water, but local surface mats may occur. On the west coast, algae mixed with water are most abundant in the area between Uusikaupunki and Rauma and near Korsnäs.

In the Gulf of Finland, algae occur mixed with water in the open sea areas of Inkoo and Porkkala and as surface mats in the eastern Gulf of Finland around Gogland. This week, the greatest number of blue-green algae have been observed south of the Archipelago Sea and in the area spanning from Kemiönsaari all the way to the Åland archipelago. Blue-green algae are found in the area both mixed with water and as surface mats.

In addition to official monitoring, information on the blue-green algae situation is also gathered from the public. A total of over 80 observations made by citizens were obtained through the Lake-seawiki and Vesi.fi this week. Blue-green algae were found in 64 of them.

This year’s weekly reports on the blue-green algae situation prepared by the Finnish Environment Institute will end on 8 August, but the national monitoring of blue-green algae will continue until 30 September. Blue-green algae typically still occur in inland waters and sea areas well into the autumn. In the future, the Finnish Environment Institute will provide information on the blue-green algae situation as needed. A summary of this summer’s blue-green algae monitoring will be published on 29 August 2024.