International ships are no longer unknowingly releasing invasive species into the Great Lakes and St. Lawrence Seaway, a new report has found. Many big ships carry water in ballast tanks. This ballast water makes the ships heavier and easier to control. However, officials found that invasive species, such as zebra muscles, were sometimes taken into the ballast tanks in faraway locations. If the water in those tanks was released in the Great Lakes, the invasive species could get out and cause great damage to the local environment. New regulations set by the Canadian and U.S. governments in 2006 forbid international ships from flushing out their ballast tanks within the Great Lakes system. The regulations seem to be working. There have been no reported new invasions from ballast water since the regulations went into place.
Photo of ship near the Duluth Harbor on Lake Superior by Pete Markham/Flickr, via Creative Commons.