Warmer water temperatures increasing algae growth

There are no large rafts of algae forming yet, but conditions have produced blue-green algae growth at levels normally seen later in the summer.

Scientist taking water samples off the Helsinki coast / Credit: Elias Haro

The warm summer temperatures heating the coastal Baltic Sea have helped blue-green algae bloom earlier than usual.

While the algae levels on most beaches are still quite low, new observations in eastern and western Helsinki shores show the water temperatures have risen from +17°C to +23°C. This, combines with calm weather and increased light levels means blue-green algae is being see at levels normally expected in July or August.

Public health officials say that a small amount of the blue-green algae – or cyanobacteria – not visible to the naked eye shouldn’t prevent normal swimming activities. However if there’s a lot of the algae in the water swimming should be avoided, and anyone coming from the water should take a shower immediately afterwards.

Children in particular are being urged not to go into the water if the seasonal algae is spotted.

In warm weather with calm waters, large cyanobacteria rafts can float on the surface of the water but due to eastern winds pushing away from the Gulf of Finland these algae rafts haven’t been observed yet this year.