Blue-green algae likely turned Tupos swimming water turquoise

Blue-green algae and its decomposition are the likely explanation for turquoise water at a swimming spot in Tupos, Liminka, Yle reports.

The water changed colour earlier this week. Biologist Mirja Heikkinen from the water and marine management unit of the Oulu licensing and supervision authority said decomposing blue-green algae often turns water turquoise and gives it an earthy smell.

The unusual colour was previously reported by Rantalakeus. People interviewed by the newspaper said they had gone to look at the swimming spot because of a strong smell.

Emergency services visited the location on Thursday and separated the oil-like area of water from the rest. Heikkinen said they carried out what is known as a stick test.

If the substance had been paint, it would have been visible on the shores and stuck to the stick, she said. Nothing stuck to the stick, while the substance broke down, which also points to blue-green algae.

A sample has been taken from the swimming spot and is being analysed in a laboratory.