The Post-Standard is reporting that zebra and quagga mussels (Dreissena polymorpha and D. bugensis) were indirectly responsible for the shut-down of a nuclear power plant on three different occasions last September and October. The James A. FitzPatrick Nuclear Power Plant in New York relies on water intake pipes from Lake Ontario, which is inhabited by both mussel species. While the official cause of the shutdowns was wave action leading to the clogging of the intake pipes with the green alga Cladophora, the mussels are being blamed for the proliferation of algae since 1) they don't eat it 2) their filtering abilities are clearing up the lake, allowing sunlight to reach lower depths and spurring the production of more Cladophora and 3) their waste products act as fertilizer to further enhance algae production. Plant workers have responded by enhancing the screens and other contraptions in place to keep the intake pipes clear.
Update: In related news, the mussels discovered late last year in the Pueblo Reservoir in Colorado have turned out to be zebra mussels - a new species for that state. (If you follow the ISW Twitter feed, you found that out about six hours ago.)
(Tip of the virtual hat to the Protect Your Waters website for linking to the power plant story.)