Eawag Annual Report 2022

12
The quagga mussel conquers Switzerland
Since 2014, the invasive mussel species has been spreading into more and more lakes in Switzerland.
Where the quagga mussel settles, it multiplies en masse. Now, researchers at Eawag are showing that this
could unbalance lake ecosystems, decimate fish stocks and increase the cost of maintaining and cleaning
water pipes.
In the picture Since its first
detection in Switzerland in
2014 in the Rhine near Basel,
the quagga mussel has been
spreading rapidly in
Switzerland.
Esther Michel, Eawag
The quagga mussel (Dreissena bugensis) originates
from the Black Sea region. But now it is widespread in
Europe and North America, where it is an aggressive
invasive species that contributes to the loss of biodiversity.
It was first detected in this country in Lake Constance
in 2014. Since then, it has been found in more
and more lakes, as a team led by Linda Haltiner from
Eawag’s Aquatic Ecology department and Hui Zhang
from the University of Konstanz has proven.
New habitats
Quagga mussels spread naturally by floating in the current
in the larva stage. However, the larvae are also
carried away unintentionally in the ballast or engine
cooling water of ships and recreational boats. In addition,
the adult mussels stick to objects in the water: If
these are not cleaned or dried thoroughly before they
are released into other water bodies, the mussels can
also enter new habitats in this way.
Where the quagga mussel settles, it multiplies en
masse. This is because it finds enough to eat even
when food is scarce, reproduces almost all year round
and also colonises soft substrate in the deep zone of a
lake that is inaccessible to other mussels. It is thus capable
of completely displacing other species. In North
America, at least, it has succeeded in doing so.
It is still too early to make a final assessment of the
consequences of the quagga mussel invasion in Switzerland,
says Eawag researcher Piet Spaak. But he
fears that the invasive mussel species could also affect
how we humans use the lakes: because quagga
mussels efficiently filter food out of the water, less
is left for the plankton. And the fish stocks that feed
on plankton are becoming smaller. In addition, the tiny
larvae easily find their way into pipes, which increases
the effort required for the maintenance and cleaning of
drinking water supply systems.
Quagga mussel
Fact sheet (PDF)