The invasive quagga mussel
The quagga mussel is an invasive species in Switzerland. It spreads rapidly in affected waters and has a profound impact. It changes ecosystems, affects infrastructure and causes costs in the hundreds of millions of francs. Eawag researchers are therefore working to understand and predict the impact as accurately as possible.
The quagga mussel (Dreissena rostriformis bugensis) is an invasive species: it originally comes from the Black Sea region, but is now widespread in parts of Europe and North America. It is found in lakes, slow-flowing rivers and estuaries.
The invasive mussel is a problem mainly in the deep lakes of the Alpine foothills, because here, unlike along the shallow water zones in its original habitat, it is only eaten by a small number of birds and fish.
The larvae can spread naturally by floating in the current and thus being carried downstream. The larvae are also unintentionally spread by humans in the bilge, engine cooling or ballast waters of boats that are used in different bodies of water. The adult mussels also stick to boats and other objects. In addition to spreading via boats, it can also be carried from one body of water to the next via water sports or fishing equipment.
Far-reaching impact on nature and infrastructure
The speed at which the quagga mussel spreads and the high level of damage it can cause are posing challenges for authorities and operators of energy and water utilisation facilities on water bodies.
The presence of the mussel significantly changes ecosystems. Due to the high filtration rate, phytoplankton, for example, is greatly reduced, which deprives other organisms, such as water fleas (zooplankton), of a food source. These creatures are, in turn, food for fish, whose food supply is also reduced. A reduction in phytoplankton also makes the water clearer, allowing light to penetrate deeper into the lake, enabling aquatic plants to grow more prolifically. This, in turn, results in changes in ecosystem structure and food webs. Eawag researchers are working to understand and predict the impact on ecosystems as accurately as possible. However, interactions with other invasive species, possible pollution and even climate change make predictions unique and complex for each water body. In addition, the quagga mussel interferes with human water use.
The biggest problem is pipe blockage in water supply or cooling water systems. Maintenance and renewal costs are rising sharply. But fishers who catch more mussels than fish with their bottom-set nets also have a considerable amount of extra work cleaning their nets.
The current situation in Switzerland
Once the quagga mussel has settled in a body of water, it cannot be eliminated. This applies to Lake Constance, Lake Geneva, Lake Neuchâtel , Lake Biel, Lake of Murten, Lake Joux and Lake Hongrin, as well as the Rhine and the Aare. Lake Constance, Lake Geneva and Lake Neuchâtel are particularly affected. Recently, the quagga mussel has also been discovered in Lake Zurich, Lake Zug and Lake Alpnach.
In these lakes, the biomass of quagga mussels per square metre is likely to increase by a factor of 9 to 20 over the next 20 to 30 years. In addition, it will also penetrate into the deeper areas of the lakes, as demonstrated by a comparison with North American lakes, where the mussel has been widespread for much longer. Without preventive measures, it is likely that it will quickly spread to previously unaffected water bodies.
Calculated biomass of quagga mussels per square metre over a period of 33 years since initial detection. The dots represent the status in 2022. (Graphic: Kraemer et al., 2023, revised)
Joint action is necessary
Eawag recommends that water bodies that are not yet affected be protected as best as possible. This can be achieved by inspecting, cleaning and drying boats, equipment for water sports and fishing when moving from one body of water to the next. In affected bodies of water, the consequences can be mitigated by designing the infrastructure in such a way that the mussels and their larvae cannot enter.
Together with the federal government and cantonal authorities, Eawag is working on a standardised concept for the early detection and monitoring of the quagga mussel. They also advise cantonal alien species agencies, water and heating suppliers and other stakeholders on the continued development and harmonisation of preventive and protective measures.
History of the quagga mussel in Switzerland
Current distribution of the quagga mussel in Swiss water bodies (red dots). The first finding was in 2014 in an environmental DNA sample from the River Rhine in Basel. The years next to the dots indicate the year of the first discovery. Lakes in which no quagga mussels have yet been found are indicated by empty squares. The remaining lakes have not been investigated.
Graphic: Haltiner et al. 2022, (revised)
Video: The quagga mussel threatens to upset Lake Geneva ecosystem
How will the quagga mussel spread in Lake Geneva? To find out, a team from the University of Geneva, Eawag and the University of Konstanz compared four North American Great Lakes, where the invasive species has been proliferating for over 30 years, with three Swiss lakes where colonisation is less advanced: Lakes Biel, Constance and Geneva.
Picture gallery
We have made the following images of quagga mussels available under the Creative Common Licence CC BY-NC-SA 4.0..
Publications for practice
Research projects
Network
We work together with a wide variety of partners.
The working group of the Conference of Environmental Agencies assists the cantons with invasive alien species (website in German, French, Italian).
The federal government coordinates the management of invasive alien species (website in German, French, Italian).
The IGKB wants to protect Lake Constance as a unique habitat (website in German).
International Commission for the Protection of Lake Constance (IGKB)
Scientific publications
Cover picture: Quagga mussels from Lake Constance (photo: Keystone, Gaetan Bally, photo montage: Eawag).