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Most of the world’s shipping nations are not complying with procedures designed to stop the spread of exotic organisms carried around the globe in the ballast of ships. The organisms can cause havoc to marine life in the ports where ballast water is off-loaded, because their natural predators are not there to keep them in check. Human health may also be at risk. Australia is inspecting all ships from South America and parts of Asia to prevent the introduction of cholera in ballast water. (see Graphic)

In London next week, the Marine Environment Protection Committee (MEPC) of the International Maritime Organization will consider the findings of a survey that shows many countries are ignoring IMO guidelines designed to reduce the risk of importing alien organisms. The problem is highlighted by the case of a destructive starfish which is spreading northwards along the Tasmanian coast and could reach as far as Sydney, 800 kilometres to the north. The starfish is normally restricted to the waters of the northern Pacific and was probably introduced to Tasmania in ballast water from Japan.

In a report on the starfish released last week, scientists from the CSIRO, Australia’s national research organisation, compare the starfish outbreak to Australia’s perennial plagues of rabbits. Both animals are ‘highly fecund and voracious eaters, with the capacity to inhabit large areas, causing damage to endemic and commercially valuable species’. The starfish, Asterias amurensis, is a ‘considerable threat’ to Australia’s shellfish industry, say the scientists. ‘Each time a vessel takes on seawater from an environment contaminated with starfish eggs and larvae, it has the potential to disperse the starfish to wherever the seawater is unloaded,’ says the report.

Ships take on ballast water in their home ports, discharging it when they take on cargo for the return journey. In 1991, the IMO adopted guidelines which recommend that ships should avoid taking on ballast in shallow areas and during toxic blooms of marine algae; keep accurate records of where and when ballast is loaded; exchange ballast water at sea, where toxic organisms are rare; and discharge sediments into approved areas at the port of destination (‘End of the line for deadly stowaways’, New Å®ÉúСÊÓƵ, 24 October 1992).

The guidelines are voluntary at this stage because it is not known which is the most effective way of treating ballast water. ‘We have to have a better means of managing ballast before the guidelines can be made mandatory,’ says Denis Paterson from the Australian Quarantine and Ins-pection Service. After a meeting of the MEPC last October, Australia was asked to conduct a survey of IMO members. ‘There has not been a significant uptake of the guidelines,’ says Paterson. ‘That is unsatisfactory.’

The survey revealed that some ‘major trading nations’ are very worried by the danger of ballast water and have adopted their own procedures to prevent the escape of exotic organisms.

In the next few weeks, the research arm of Australia’s largest company, BHP, will carry out tests on heat treatments to sterilise ballast water, using the water that cools the ship’s engines. Until recently it was thought that water would have to be heated to as much as 45 °C, but according to Paterson, it may only have to be between 2 °C and 5 °C above the temperature of the water in the ballast tanks to kill off potential invaders.

Å®ÉúСÊÓƵs are also investigating why outbreaks of exotic organisms have been reported only in the past 20 years, when water has been used as ballast for more than a century. Jim Carlton from Williams College in Connecticut has suggested that industrial pollution and the accumulation of nutrients such as nitrates and phosphates have destabilised natural ecosystems around ports, allowing exotic organisms to take over. ‘The theory is a very challenging one that is causing a lot of interest,’ says Gustaaf Hallegraeff from the University of Tasmania.