The leak of some 66 tonnes of nickel into the river Kokemäenjoki in early July is believed to have caused a mass death of mussels. Its effects on fish populations, in turn, remain unknown.The Environment Department of Pori has issued a statement advising against eating fish from the Kokemäenjoki at least until fish samples caught from the contaminated river have been tested for toxins.

The statement was issued after the matter was discussed with the Finnish Environment Institute and the Centre for Economic Development, Transport and the Environment (ELY Centre) of Varsinais-Suomi.

Up to 66 tonnes of nickel and at least an equivalent amount of sulphate was released into the river from the Harjavalta plant of Norilsk Nickel in early July, representing the biggest nickel leak in Finnish history.

The ELY Centre of Varsinais-Suomi will hand over fish samples caught from the river to the Finnish Food Safety Authority (Evira) for examination.

“It's a precautionary measure. We can't be entirely sure of the concentrations of nickel in the backwaters or deep parts [of the river]. Nickel accumulates in fish belatedly, but we don't know its effect,” Matti Lankiniemi, the environmental director at Pori, states in the bulletin.

The leak is also believed to have caused a mass death of mussels. Experts from the ELY Centre of Varsinais-Suomi examined the river bed on Monday and Tuesday, discovering an abnormal number of dead mussels.

Among the several species affected is the endangered and protected thick-shelled river mussel.

Environmental experts have also reminded that determining the impact of the leak on the entire river ecosystem will require further monitoring. At present, water samples are also taken off the coast of Pori to determine how far the effects of the leak reach.

Jussi Ahlroth – HS
Aleksi Teivainen – HT
Photo: Reijo Hietanen