These changes have both positive and negative consequences for Lake Constance. One positive aspect is certainly that the water quality of the lake is not endangered by invasive species. The water has even become clearer, it is suitable for swimming and diving and the quality of the drinking water is excellent.
However, the negative consequences outweigh the positive ones: quagga mussels grow on everything, including the intake pipes of water extraction plants, which can become clogged. This forces water suppliers to build new plants that contain an automatic quagga cleaning system. These investments will cost hundreds of millions of euros.
I am also afraid that fish catches in Lake Constance will continue to decline. The quagga mussel generally reduces the productivity of the lake by filtering out the algae from the water. And the stickleback also contributes to the fact that the already scarce plankton that is still available as fish food is not available for the fish that are interesting for fishing, for example the whitefish. Unfortunately, quagga mussels and sticklebacks are hardly eaten by fish in Lake Constance.
Are there any efforts being made to reduce the dominance of quagga mussels and sticklebacks?
That is difficult. Diving ducks love the Dreissena mussels, but unfortunately they cannot keep the quagga mussel population in check. Therefore, at the moment we cannot do much more than closely examine and document the situation. We have just started a two-year monitoring campaign to track the quagga mussel at all depths of the lake. In this way, we want to find out whether it spreads as quickly as it does in North American lakes. This way we can at least prepare ourselves for what to expect.
How is biodiversity being promoted in Lake Constance?
Despite the points mentioned, there are also many positive things to say about Lake Constance. It is an important aquatic habitat for numerous species. To date, 330 bird species have been observed in the Rhine delta and the lake is an important resting place for water birds. Around the lake there are also various nature reserves and repeated efforts to renaturalise built-up shores in order to create more habitats for shore animals and plants.