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Toxic blue-green algae blooms grow in Archipelago Sea, Gulf of Finland

Thanks to warmer-than-average temperatures, blooms are not expected to decrease any time soon.

File photo of blue-green algae in seawater. Image: Markku Ojala / AOP

Toxic blue-green algae, or cyanobacteria, blooms are being found in abundance in Finnish waters, especially in coastal areas of the Archipelago Sea and the Gulf of Finland, according to the latest Finnish Environment Institute (Syke) report on the matter.

The situation is slightly worse than in recent years, according to the institute's senior research scientist, Mika Raateoja.

"It is reasonably worrying," he said.

The institute has warned that people and animals – especially small children and dogs – can become very ill from touching, swallowing or even breathing in water droplets containing the toxic algae.

According to Raateoja, as long as wind and rain mix the blue-green algae with the water mass, the blooms do not appear on the surface, making it difficult to estimate its levels from the water's surface.

"For us scientists, the blue-green algae situation is bad, even if you can't see it on the surface," Raateoja explained. "Blue-green algae is very slow-growing. Its numbers don't suddenly rise to worse levels."

As cyanobacterial growth is favoured by continued warmth, its concentration in marine areas is not expected to decrease any time soon, due to warmer-than-average temperatures.

Inland water conditions better

According to the report, blue-green algae conditions in inland waters are better than average at the moment.

However, the worst season for blue-green algae growth is still ahead, so it is too early to breathe a sigh of relief, according to Syke's team leader, Satu Karjalainen.

"The number of blue-green algae usually peaks in July and August, when the waters are warm," she said.

While temperature is a major factor in the growth of blue-green algae, thunderstorms also play a role.

"Thunderstorms may increase the nutrient levels of water bodies by leaching them from catchments. Therefore, if there are more thunderstorms in July, blue-green algae blooms can also increase," Karjalainen explained.