Zebra mussels are some of the most high profile and impactful invasive species in Canada, and have transformed the Great Lakes watershed in the past three decades. Voracious feeders that consume all algae, they have clarified our lakes, caked our beaches with their sharp shells, and denied other species precious food. Interactions between zebra mussels and algal blooms, another notorious nuisance, are largely unknown. My research uses environmental DNA, an emerging technology, to examine what factors make an ecosystem resilient to zebra mussel invasion, how native mollusk communities react to zebra mussels, and if they help or hinder algal blooms.