Swiss lakes are facing a new threat: molluscs. The Quagga mussel, originally from the Black Sea, is spreading rapidly and gobbling up the food that fish need.
The worst-hit area is Lake Constance, where 15,000 Quagga mussels per m2 cover the lakebed. The invasive species has also been found in lakes Neuchâtel and Geneva.
The Quagga mussels, measuring up to 40mm, were first noticed in the bed of Lake Constance in 2016. The species is a prolific breeder and a major threat to indigenous fish. They are prodigious filterers, removing substantial amounts of phytoplankton from the water and decreasing the food source for zooplankton – small, floating animals that fish need to eat to survive.
Water supply threat
They also disrupt water supplies by clinging to and blocking supply pipes. Four extra staff had to be hired at Lake Constance to remove them.Ozone is used to kill the Quagga mussels’ larvae. Sand filters then remove them from the water. A spokesperson from the Lake Constance Water Supply Association said they expect to spend millions in their efforts to eliminate the threat to water supplies.
The Swiss federation, various cantons and the European Union have invested several million francs into a research project at the Water Research Institute of the Federal Institute of Technology in Zurich, to find out more about the mollusc and its effect on the ecosystem.
The Quagga mussel originally comes from the Black Sea catchment area and was introduced by boats or even, possibly, from the Rhine via waterfowl. The species has also hit fish stocks in the Great Lakes of North America, with scientists blaming the effects the mussels have had on the lake’s food chain.