Quick Dips

Flushing Out Foreigners

With increasing concern in the shipping industry and among government agencies about the release of foreign marine organisms into New Zealand waters through ballast water discharge, Nelson's Cawthron Institute aims to develop an effective shipboard treatment that will kill potentially harmful ballast organisms.

The evidence linking dispersal of marine organisms to the movement of ballast is unequivocal. Foreign organisms pose a threat to the native communities of New Zealand's coastal waters, wild fisheries and to the aquaculture industry, and many are able to survive the period between ballasting and discharge. To date no feasible method has been found for killing organisms in ballast water.

The new project will initially test the effects of heat and biochemical methods for oxygen removal in the laboratory on marine organisms already in New Zealand which are similar to species potentially harmful to our marine environment. These are the eleven-armed starfish, a native species closely related to the potentially harmful predatory Northern Pacific seastar, and the introduced seaweed Undaria. The treatments are targeted towards the free swimming or larval forms of ballast organisms because they represent the most vulnerable stage of their life cycle, and since they are likely to disperse throughout ballast water, they are the form most likely to be released during ballast discharge.

A shipboard experiment will be carried out using the most suitable laboratory developed treatment, involving application of the treatment to small ballast tanks on the Union Rotoma.

The FRST-funded work will hopefully provide a feasible method for shipboard operation for the treatment of ballast thus minimising the risk of introducing harmful organisms into New Zealand waters.