Archive of Blue-green algae bulletins

Note: This is an archived report.
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Published 15.6.2023

Blue-green algae observations increased slightly in inland waters and coastal areas

The blue-green algae situation remains calm, even though the number of observations in lakes and coastal areas has increased. Abundant blooms of blue-green algae have been observed at two inland water observation sites in Southern Finland. So far, no observations of surface blooms have been made in Finland’s open sea areas. Surface waters both at sea and on inland waters are becoming warmer.

The blue-green algae situation is still calm, even though the number of blue-green algae observations has increased slightly since last week. Abundant blooms of blue-green algae have been observed at two national inland water observation sites in Southern Finland. Some blue-green algae have been detected at nine inland water observation sites, mainly in Southern Finland, and at three observation sites along the coast of the Gulf of Finland and the Archipelago Sea.

The situation is typical for early summer. The warm weather forecast for the coming week may contribute to the development of blue-green algae blooms, especially if the winds remain weak.

Plenty of coniferous pollen may still be in the water in places, colouring the water yellowish. It might look deceptively like blue-green algae. All discolouration in water should be treated with due caution, as blue-green algae can only be distinguished from pollen by microscopic examination.

No surface algae has been detected in the satellite images taken on the open sea areas of Finland’s territorial waters. However, some blue-green algae mixed with water can be observed in the eastern Gulf of Finland near the Estonian coast.

The temperatures of surface waters that cooled down at the end of May have started rising during the warm beginning of the week.  The surface waters will also continue getting warmer next week.