Brown dinoflagellates, Heterocapsa triquetra. Picture: Environment Centre of the City of Helsinki/Marjut Räsänen

According to the Environment Centre of the City of Helsinki the amounts of algae are small or moderate in Helsinki’s inner and outer archipelago. In bay areas there are a lot of algae. The water temperature has risen quickly in all the Helsinki sea area because of the hot weather and is now high in relation to the time of the year. The surface water temperature is around 17–20 degrees in the inner and outer archipelago and 22–23 degrees in bay areas.

The forecast very warm weather is likely to increase the amount of blue-green algae and contribute to algae gathering in the surface layer of the sea.