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2002 October Report of the Commissioner of the Environment and Sustainable Development
Case Study 4.4—Ballast water is a major pathway for aquatic invaders
Ships take on ballast water for stability and safety. When they do, their ballast tanks also take on a wide variety of aquatic species, including micro-organisms, algae, plants, small fish, and invertebrates. Over time, a layer of sediment accumulates in the tanks and it can also contain alien species. A recent study estimated that 3,000 species of aquatic organisms are transported around the world every day in the ballast tanks of ships.
Ballast water can transport a range of micro-algae, including toxic species that may form harmful algae blooms or "red tides." The public health impacts of such outbreaks are well documented and include paralytic shellfish poisoning, which can cause severe illness and death in humans.
Scientific research has established that human pathogens are also transported in ship ballast water. A 1998 study that sampled the ballast water of 28 transoceanic vessels en route to the Great Lakes found a number of known human pathogens (including salmonella, Vibrio cholerae, Giardia, and fecal coliforms such as E. coli) in one or more of the samples.
Ships pump out their ballast tanks in ports when they pick up cargo. In 1999, there were 201 Canadian ports reported to have handled cargo, 57 percent of it at 10 of the ports.
The introduction of invasive species through ballast water is an unintended consequence of a measure that serves a vital purpose to shipping and ship safety. However, while the Canada Shipping Act allows the federal government to regulate ballast water to prevent introductions of aquatic invasive species, it has not done so; nor has it assessed the potential risks that ballast water may pose to public health.
Ballast tank sediment contains alien species that may be released into Canadian ports as foreign vessels pick up and off-load cargo.
Photo: Phil Jenkins
Ballast water is a common source of unintentional introductions of aquatic invasive species.
Typical location of ballast tanks on a commercial ship.
Source: Phil Jenkins