What is Ballast Water and Why is it a Problem?
Ballast water is used to balance a ship when it loads and unloads cargo and to stabilize it during transit through rough water. Ships take in ballast water when cargo is unloaded and discharge it when cargo is loaded. The volume of ballast water carried on-board a ship varies depending on the type of load that it is transporting and the ship’s capacity for storing ballast water. Research has shown that ballast water of ships engaged in international trade have transferred AIS species from locations such as the Baltic, Black, and North Seas across the Atlantic Ocean to the freshwater ecosystem of the Great Lakes. The Transportation Research Board of the National Academies noted in it report, Great Lakes Shipping, Trade, and Aquatic Invasive Species, issued July 2008, that an estimated 55 to 70 percent of all AIS introductions in the Great Lakes Basin are attributed to ballast water discharges.
