From the Great Lakes in the US to the glacial-melt waters of Switzerland, quagga mussels have wreaked havoc on local ecosystems. Now, they’ve been reported in Northern Ireland. Bastiaan Ibelings is a microbial ecologist at the University of Geneva. He tells The World’s Host Marco Werman that the pesky mollusks have transformed Lake Geneva over the past decade. He joins Marco from a small village near Martigny, Switzerland.