More than 185 species of foreign fish, algae, plants, insects, and viruses have been brought into the Great Lakes. Many of them are invasive species that are damaging the lakes, such as zebra mussels, quagga mussels, round gobies, and Phragmites.
About a third of those invasive species were brought here in the ballast water of ocean-going ships. As they picked up their ballast water in foreign ports, they sucked up aquatic life along with it.
For decades, that ballast water and the things that lived in it were simply pumped out into the Great Lakes ports as the ships adjusted to loading and unloading cargo.
In 2005, Michigan passed a law requiring those ocean-going ships to obtain a state permit before docking in Michigan’s ports. The permit certified the ships would either not discharge ballast water, or that they’d treat ballast water to kill off foreign critters. Michigan passed that law because it felt the federal government wasn’t doing enough to stop invasive species from getting to the Great Lakes.