During 1800s and before, rock ballasting was used to maintain the balance of wooden ships. During those old days, there were ballasting and de-ballasting stations in which rocks were loaded or downloaded respectively (a ballast hill is shown in the image).
After the introduction of steel hulled vessels, water has been used instead of rocks as ballast to stabilize vessels at sea. This major shift in ship ballasting has been found easier and more efficient. However, the practice showed ballast water acted as a biological belt moving variety of living organisms from the filling station and discharge it into the host environment.
Some case studies caused serious ecological and economic damage to aquatic ecosystems especially when natural enemies to the invaded organisms do not exist. Examples of the ecological damage caused by nuisance ballast organisms include the introduction of Asian algae, Odontella (Biddulphia sinensis) in the North Sea in 1903 and the zebra mussel in Lake St. Clair in 1988 before spreading into the Great Lakes. The introduction of cholera, Vibrio cholerae, into Peru via ballast water in 1991 and associated human risks is another example.
The global recognition of the threats associated with the ship’s ballast water has necessitated the developing of guidelines and management strategies for ships’ ballast at national or global levels.