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Blue-green algae expanding on southwest coast, lakes

Algae observations are slightly above average at this point in the season.

In marine areas, blue-green algae was observed this week, especially in the inner archipelago of the Archipelago Sea. Image: Markku Ojala / AOP

Blue-green algae, or cyanobacteria, has increased in marine areas and has also been observed in lakes, Finland's Centre for Economic Development, Transport and the Environment (Ely) has reported.

Blue-green algae was observed during this week in particular in the Archipelago Sea and inner archipelago. Observations were made in the sea along the coasts of Kemiönsaari, Kaarina, and Naantali.

However, the amounts of blue-green algae observed have been low and blooms have not grown to large, floating clumps yet. In addition to the Archipelago Sea, algal blooms have also been observed close to the coast in the Gulf of Bothnia.

In open water, the algal concentrations are mostly clustered around sheltered areas of the archipelago, but the majority of Finland's Baltic coast is so far free from cyanobacteria.

Algal sightings in inland lakes are mostly low, but warm and calm weather can quickly change the situation. Similar conditions apply to marine areas.

According to Ely, the algae situation is above average at this point in the season.

In Lapland, the first cyanobacteria sightings were made on Midsummer, while many observations in southern parts of the country came beforehand.

The Finnish Environment Institute recommends that bathers avoid swimming spots contaminated with blue-green algae due to its adverse health effects.

The observations come from Ely monitoring sites, Rotary International observation points, and individual reports.