It would be hard to design a better invasive species delivery system than the Great Lakes overseas freighter. The vessels pick up ballast water at a foreign port to balance less-than-full cargo loads. When the ships arrive in the Great Lakes, cargo is taken onboard and the ballast water—up to 10 Olympic swimming pools’ worth per ship—and all the life lurking in it gets set loose in the lakes. As one exasperated Great Lakes biologist once told me: “These ships are like syringes.”
