What makes zebra mussels an invasive species?

Zebra mussels are an invasive, fingernail-sized mollusk that is native to fresh waters in Eurasia. They filter out algae that native species need for food and they attach to and incapacitate native mussels. Power plants must also spend millions of dollars removing zebra mussels from clogged water intakes

Explanation:

Zebra mussels negatively impact ecosystems in many ways. They filter out algae that native species need for food and they attach to--and incapacitate--native mussels. Power plants must also spend millions of dollars removing zebra mussels from clogged water intakes.