‘It’s an open invasion’: how millions of quagga mussels changed Lake Geneva for ever

The molluscs are decimating food chains in Switzerland, have devastated the Great Lakes in North America, and this week were spotted in Northern Ireland for the first time

Like cholesterol clogging up an artery, it took just a couple of years for the quagga mussels to infiltrate the 5km (3-mile) highway of pipes under the Swiss Federal Technology Institute of Lausanne (EPFL). By the time anyone realised what was going on, it was too late. The power of some heat exchangers had dropped by a third, blocked with ground-up shells.

The air conditioning faltered, and buildings that should have been less than 24C in the summer heat couldn't get below 26 to 27C. The invasive mollusc had infiltrated pipes that suck cold water from a depth of 75 metres (250ft) in Lake Geneva to cool buildings. It's an open invasion," says Mathurin Dupanier, utilities operations manager at EPFL.

Mathurin Dupanier indicates the water cooling systems that were blocked by the invasive quagga mussels. Photographs: Phoebe Weston/the Guardian; Ecole Polytechnique Federale de Lausanne