Exotic species are plants and animals that are introduced, either intentionally or accidentally, into areas where they are not native. An exotic species often spreads rapidly due to a lack of natural predators, parasites, pathogens and competitors that would otherwise limit its growth. This can result in a loss of native species and, therefore, a decrease in biodiversity. As such, exotic species are often considered to be “invasive.”

Two invasive aquatic species found within Lake George are Eurasian Milfoil and Zebra Mussels. Both of these species are believed to have been introduced into Lake George through the emptying of ballast water from commercial transatlantic ships into the Great Lakes. Cargo ships carry significant amounts of ballast water to stabilize the vessels during transoceanic crossings. When ballast tanks are filled, many forms of aquatic life in the source water are drawn into the tanks. Once in ballast tanks, organisms can be transported to other areas and subsequently discharged into waters at foreign ports.