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Ballast Water

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Ballast Water as a Pathway

When ocean cargo freighters cross the ocean, they use something called a ballast to balance the ship as it crosses the rough waters. In the 1800’s and early 1900’s solid soil ballasts were used, which provided a pathway to transfer seeds of exotic plants. Today, modern ocean freighters use water for their ballast. The ballast water is drawn in at the ship’s origin, and must be pumped out at its destination prior to unloading the ship’s cargo. Many organisms may survive within the water as the ship crosses the ocean and introduced to a new area. The Great Lakes provide a perfect connection for ocean freighters to ship cargo to and from Canada to overseas which has resulted in over 180 non-indigenous aquatic species to become established within the Great Lakes Basin.

Did You Know?

  • Since 1927, over 50% of the non-indigenous aquatic species found within the Great Lakes basin have come from ballast water releases?
  • In 2006, the federal governments of Canada and the United States created joint legislation requiring ocean freighters to treat their ballast water prior to entering the Great Lakes. Since this effort, zero species have been introduced through this pathway.

OFAH/OMNRF Invading Species Awareness Program. (2021). Pathways – Ballast Water. Retrieved from:
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