Quagga mussels have now also been found in the River Lorze near Cham

The quagga mussel is spreading in Lake Zug. This will have consequences - and not just for nature.

"The quagga mussel will become a massive problem," says Marcel Fähndrich, Head of Energy at the WWZ company (Zug Water Works). "You only have to look at Lake Constance to see that the damage will be considerable." The invasive mussels not only settle in the lake, but also on and in facilities that are in the lake or that flow into it.

And the quagga mussel is no longer only found in Lake Zug itself. "At the end of July, during an inspection of the Wärmeverbund Cham (Cham Heating Network), we found mussels in the Lorze river, for the first time," says Marcel Fähndrich.

Divers searching in Lake Aegeri
The situation in Lake Aegeri is not as clear-cut as in Lake Zug. "To be on the safe side, we have sent divers into the lake to search the lake bed in defined areas," says Roman Keller, deputy head of the officeCantonal Office for Forests and Game (Amt für Wald und Wild). "Of course, we hope that the mussel has not yet arrived in Lake Aegeri."

Because once the mussel spreads, it can cause massive damage to facilities. But not only that. As the quagga mussel feeds on plankton, the entire food chain is at risk, explains Roman Keller. In addition, the quagga mussel has hardly any natural enemies.

It is not only the installations of the Cham Heating Network that are affected by the mussel infestation; the Circulago installations of the WWZ company are also likely to be infested. According to Marcel Fähndrich, this is only a matter of time. The WWZ had already realised that the mussel could one day become a problem when planning the Circulago, which extracts heating and cooling energy from Lake Zug, and precautions were therefore taken. "We took current experience from Switzerland and abroad into account," explains Fähndrich.

According to him, only mechanical cleaning of infested systems is possible. Pipes, for example, are cleaned with a plastic device similar to a bottle cleaner. This is moved back and forth in the infested pipe, loosening the mussels from the pipe wall and crushing them.

Quagga mussels have now also infested a plant belonging to the Cham Heating Network on the River Lorze   Photo: zvg/WWZ AG
Roman Keller, Deputy Head of the Hunting and Fishing Department at the Zug Office for Forests and Game           
Marcel Fähndrich, Head of Energy at WWZ AG     Photo: zvg
The quagga mussel in Lake Geneva.          Photo: zvg/Linda Haltiner, Eawag

Millions of Swiss Francs of damage to be feared
The quagga mussel causes millions of Swiss Francs of damage, because it blocks discharge and intake pipes. Maintenance work therefore has to be carried out much more frequently, and this results in a corresponding increased need for personnel.

What's more, quagga larvae migrate through the intake baskets and filters, and can also penetrate sensitive systems and damage heat pumps. An example of this is the cooling systems of the EPFL Technical University and the University of Lausanne, which are located on Lake Geneva. It is estimated that it will cost a good CHF 6 million to renovate and upgrade these systems against the mussel.

"If you look at the private facilities that need to be maintained on Lakes Aegeri and Zug, the costs are likely to be in the hundreds of millions of Swiss Francs," explains the WWZ expert. It will be particularly expensive if the largest drinking water reserve in the canton, Lake Zug, has to be utilised, as drinking water extraction facilities would then have to be built around the lake.

Marcel Fähndrich expects the plague to reach devastating proportions in three to five years. "This time must be used to get all the facilities up to scratch," he explains. As the mussel cannot be tackled by other means, there is an urgent need to invest in fully automated cleaning systems.

Ship and boat cleaning to be continued
Now that the quagga mussel has already found its way into Lake Zug, the consistent ship cleaning programme ordered by the Central Swiss authorities no longer seems to make much sense. "On the contrary," says Marcel Fähndrich. The cleaning of ships should definitely be maintained. "This may prevent the spread from carrying on at breakneck speed."

When approached by the Zuger Zeitung newspaper, the Zugersee Schifffahrt (Lake Zug Navigation Company) wrote: "We assume that the ship's hulls and the water inlets on the ship (inlet and outlet openings for the cooling circuits, etc.) will become overgrown with quagga mussels, and that this will lead to an increase in cleaning work. In particular, this means that the intervals at which ships are lowered into the water in the port of Zug will become shorter and lowering into the water will become more important."

But one thing is clear for Marcel Fähndrich: the mussel will spread in Lake Zug. If you look at Lake Constance, the picture is bleak. Marcel Fähndrich, who recently observed the situation on site again, explains: "I saw nothing but mussels on the bottom of Lake Constance."

More information:
An invasive species
The quagga mussel is an invasive, alien species with great potential for damage. Originally from the Black Sea region, it is spreading rapidly in Swiss waters. According to the Canton of Zug's Office for Forests and Wildlife, the main reason for its spread is boats changing waters. The quagga mussel has already colonised several Swiss waters, including Lake Constance and Lake Geneva. They can be found there in aggregations of up to 25,000 mussels per square metre. Quagga mussels alter and impoverish habitats, clog lake water intakes, lead to losses in fishing and impair recreational use of the lake.