The ballast water problem

Ships carry ballast water to stabilise them when they are not carrying cargo at sea. The world’s shipping fleet carries 10 billion tonnes of ballast water each year. Every day, around 10,000 marine organisms are transported around the world’s oceans in ballast water. When discharged in a new environment, these organisms can thrive and become pests to local marine communities.

The Australian Government operates stringent protocols for ballast water management. Vessels carrying ballast water from ‘high risk’ areas are prohibited from dumping ballast water in Australian ports. However, there is no guarantee that ballast water from areas deemed ‘low risk’ does not contain organisms that could become pests once introduced into other environments. The scale of international shipping is such that areas thought to be ‘low risk’ for pest species can easily become ‘high risk’ before imported pests have been discovered.

A single ship can hold 70,000 tonnes of ballast water - enough to fill 32 Olympic swimming pools. This water can carry millions of small pests, including juvenile molluscs and seastars. The sheer volume of ballast water makes sterilisation extremely difficult. There is no effective method to treat ships’ ballast water economically, despite an abundance of research into the problem.

Ballast water exchange at sea is the method approved by the International Maritime Organisation to reduce the risk of introducing marine species. Deep water ballast exchange or treatment is mandatory for ships from ‘high risk’ areas coming into Australia. However, these methods are not fully effective and exchange at sea can be dangerous for ships. Deep water ballast exchange costs the shipping industry over $23 million a year.

The impact of introduced species

Most ballast water coming into Australia originates in south-east Asia. Transit time for vessels between Australian and Asian ports is usually less than 20 days. This is shorter than the larval life of a wide range of species found in ballast water. For example, toxic dinoflagellate algae which can accumulate in mussels, oysters and scallops and cause paralytic shellfish poisoning in humans, can survive in ballast water for weeks.

Introduced marine pest species are a major threat to coastal environments around the world. They disrupt ecosystems by introducing diseases and competing with native species for food and habitat. If established, marine pests could drastically affect the recreational, commercial and natural value of the Australian coast.

Darwin, Cairns and Hobart ports have all suffered significant financial impacts due to introduced marine pest quarantine measures that have restricted port operations.

The Australian Ballast Water Treatment Consortium (ABWTC) are developing a pilot treatment plant to sterilise ships' ballast water. For more information on this project, click here. For the final report to the Dept of Environment and Heritage about the Australian pilot project for the treatment of ballast water, click here.

For more information on introduced marine species click here.