Introduction

Many phenomena threaten the biological integrity of the Great Lakes. We highlight two: the continuing impacts of aquatic alien invasive species and the little-understood threats posed by disease-causing or pathogenic organisms. According to scientists’ best estimates, a new aquatic alien invasive species finds its way into the Great Lakes system about every eight months. The impact of introduced species already in the system, from the sea lamprey to the zebra mussel, serve as harbingers of the economic and environmental costs to come if this crucial threat is not controlled. Similarly, documented surprise outbreaks of gastrointestinal diseases, sometimes with fatal consequences, should serve as a warning that residents of the Great Lakes basin face serious, largely unacknowledged threats from an everyday substance we all tend to assume is safe – the water we depend on for recreation and drinking. Fortunately, options exist to address both of these crucial challenges.