Archive of Blue-green algae bulletins

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

Published 20.7.2023

The blue-green algae situation has deteriorated in marine areas and inland waters

The number of blue-green algae observations has increased since last week both in both coastal areas and in the open sea. Blue-green algae surface blooms have been observed in many places in the open sea areas of the northern part of the Gotland Basin and in the vicinity of the western coast of Finland. Blue-green algae has also been more commonly observed in lakes.

The national blue-green algae monitoring sites have reported no observations of very abundant blue-green algae blooms in inland waters this week. There have been observations of abundant blue-green algae at seven observation sites in different parts of Finland, with the exception of Lapland. A small amount of algae has been observed at 32 lake observation sites throughout the country.

Currently, only one blue-green algae monitoring site in Southwest Finland, Mynämäki in the inner part of Mynälahti Bay, has observed abundant blue-green algae on the coast. Abundant blue-green algae have been observed at four different observation sites along the coast of Naantali and Rauma. There is still some blue-green algae at 20 coastal observation sites. Blue-green algae observations mostly take place on the southern and southwestern coasts and the Archipelago Sea.

In addition to the official blue-green algae monitoring observations, citizens have made a total of 49 observations, 28 of which concern blue-green algae blooms.

During the week, scattered but sometimes considerable surface algae surface blooms have been observed near the coast on the western coast, south from Mäntyluoto toward the northern parts of the Archipelago Sea. There is plenty of algae mixed with water in the open sea around the middle of the Sea of Bothnia, on the latitude of Pori. Parts of it might also be on the surface. North of Åland, a few occurrences of surface algae have also been observed in the vicinity of the coast.

Since the beginning of the week, there have been surface blooms in large open sea areas in the northern part of the Gotland Basin. In the open sea, algae mixed with water have also been observed in the western part of the Gulf of Finland, west of Inkoo. On Wednesday, surface algae ribbons have appeared in the Archipelago National Park, from south of Korppoo all the way to the open sea. The amount of algae in the western parts of the Gulf of Finland has also increased, but no surface blooms have been observed in this area.

The information on this page was produced by the Finnish Environment Institute (Syke).