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Blue-green algae pops up on southern lakes ahead of Midsummer

Toxic algae levels in the sea remain low, due to relatively cool water temperatures.

Water containing blue-green algae is unsafe for swimming, drinking or washing. Image: Markku Ojala / AOP

Observations of blue-green algae—or cyanobacteria— have increased somewhat since last week, the Finnish Environment Institute (Syke) said on Thursday. Most observations of cyanobacterial blooms have come from inland waters in Southern Finland, Häme, Pirkanmaa and Eastern Finland.

Syke said in a press release that the hot weather expected for Midsummer is likely to accelerate blue-green algal blooms. If the warm weather continues, the risk of blue-green algae in lakes will increase.

Surface temperatures at many lakes in southern Finland are between 17 and 19 degrees Celsius, close to the long-term average. In the central part of the country, temperatures are between 14 and 17 degrees while northern lakes are between 11 and 14 degrees.

Situation still calm at sea

The cyanobacteria situation around the Finnish sea coast is typically calm in the early summer, as the seawater is still too cold for blue-green algae to flourish. However, there have been isolated observations of blue-green algae in the Archipelago Sea and the western Gulf of Finland.

Satellite observations have not yet detected blue-green algae blooms along the Finnish coast.

Water containing blue-green algae in water "must not be consumed by people or animals, not even after boiling," said Syke.

Harmful for kids and pets

Children and pets must not be allowed to swim in water contaminated by blue-green algae, and grown-ups should also avoid swimming, the institute said.

"If you suspect having been exposed to contaminated water, you should wash yourself with clean water after swimming. Pets should also be washed with clean water, as they could become exposed to algal toxins by licking their fur after swimming," it added.

Water contaminated with blue-green algae must never be thrown onto a sauna stove, either, as exposure through skin and respiration causes even more symptoms than swallowing it.

Last week Finland's ministries and agricultural sector organisations unveiled a plan aimed at limiting agricultural runoff, which accelerates eutrophication and algal blooms.