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ballast water

Definition

The water mass taken up by ships to balance their position while being loaded in harbours or while at sea. The water is taken on board in specially designed tanks distributed along the bottom, or located at the stern and aft of a ship. Several ship types have also top-wing tanks. It is estimated that about 12 billion tonnes of ballast water are annually transported intercontinentally. About 3000 fish and shellfish pathogens, parasites, toxic algae and human pathogens, many of which affect aquaculture in coastal and estuarine waters are known to be translocated in ballast water.

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