fact sheets - ballast water
HSI has nominated ballast water as a Key Threatening Process to threatened species under the Commonwealth Environment Protection and Biodiversity Conservation Act. We expect a decision on the listing from the Commonwealth Environment Minister in 2003.
Ballast water usually consists of coastal water that is taken on board a ship at port, for the stability of the unladen vessel during its voyage. This ballast is then discharged and exchanged for cargo at the port of destination. The sediment, which has settled at the bottom of the tanks, is physically shovelled over the side of the ship directly into the ocean.
Ballast water is different from bilge water which is a combination of rain water, sea water, waste matter and seeped oil from below deck, and is usually discharged at port in a controlled manner. The difference between bilge water and ballast water is that bilge water is considered to be abiotic whilst ballast water is biotic (contains living organisms).
Being a geographically isolated island continent and a large exporter of dry bulk such as minerals and agricultural products means that Australia relies heavily upon shipping for trade. Over 6,000 vessels from overseas and 4,000 commercial ships arrive in Australian ports each year.
In 1994, the Australian Quarantine and Inspection Services (AQIS) stated that over 155 million tonnes of ballast water is being discharged in Australian ports each year. Of which 121 million tonnes were being imported from overseas.
Ballast water can contain sediment if it is taken onboard in turbulent water. These sediments and the water can contain a wide range of live marine and estuarine flora and fauna. The larvae and spores of some marine animals can survive the tens of thousands of miles they are transported on board vessels.
Australia is particularly vulnerable as many cargo ships arrive without cargo and therefore with lots of ballast water in order to take away minerals such as coal, woodchips and wheat.
The other main source is the trade in live seafood (particularly oysters) and contaminated stock or feed for farms.
If organisms survive the transport and discharge process they may become established in the community and populations may flourish.
Technological advances such as faster, larger ships has led to the increased survival rate of non-native species and the higher rate of observed introductions over the last 2 decades in Australian waters.
There are roughly 100 exotic species known to be present in the marine Australian environment. Twenty species of exotic organism have been recorded in the Victorian waters, and the arrival of 14 of these is attributed to ballast water discharge. Species include fish, crustaceans, molluscs, polychaetes, seasquirts and algae.
Ships which are unloading cargo (and therefore ballast water) at more than one port can introduce organisms to multiple Australian ports. This is known as Top-up shipping.
Introduced organisms can affect local marine life in a number of ways, by competing with native species for food or space, preying on native species, crossbreeding with native species or by changing the habitat. There are a number of cases of species decline, but the full impact of these alien species on the communities has yet to be established.
In 1996, the Tasmanian Conservation Trust put out a media release about the possible extinction of a fish species due to an introduction via ballast water. The spotted handfish ( Brachionichthys hirsutus) was in danger of becoming the world' s first marine fish to become extinct. One reason for its decline was due to the Northern Pacific Seastar (Asterias amurensis) which was thought to have been introduced from ballast water during the 1980s.
The spotted handfish is still critically endangered because of the drastic decline in population recently. It is thought that the seastar consumes the egg masses of the handfish or depletes the handfishes' food supply. The Northern Pacific Seastar is still increasing in numbers and has spread to many areas since.
In 1998, work commenced on the Recovery Plan for spotted handfish utilising funds from the Commonwealth Endangered Species Program.
There are also problems associated with the temperature of ballast water. Ballast water collected in cold water ports is discharged into the warm water port of the Pilbara Region. The Pilbara is a key marine conservation area. There are a number of reef systems off the coast of the Pilbara. Reefs consist of delicate organisms, sensitive to temperature fluctuations.