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Mining boom 'increased marine pest risk'

Ballast boom Australia's recent mining boom increased the risk of new marine pests arriving in the nation's waters, a new study suggests.

Research published today in the Royal Society journal Open Science has found the amount of ballast water dumped from ships arriving at Australian ports doubled between 1999 and 2012.

"The vast majority of ballast water discharge was related to the export of mining commodities," say the scientists, led by mathematical ecologist Dr Robert Cope, of the University of Adelaide.

Australia is the world's leading exporter of iron ore and coking coal, which are shipped off to countries such as China, Japan and Korea, often via Singapore, on ships called bulk carriers.

These enormous ships must take on huge quantities of ballast water to keep them stable when they are empty.

"When a ship, say, goes to China and unloads iron ore, it takes on ballast water for the journey back to Australia," says Cope.

"And when it gets here and loads the iron ore, it releases that water that was collected somewhere else, into ports here."

Cope and colleagues used rare data from the Australian department of agriculture that recorded how much ballast water was discharged into Australian ports between 1999 and 2001, and where it came from.

They combined this with records of all ships coming to and from Australia between 1999 and 2012 to model how much ballast water was emitted over these 13 years.

The researchers calculate that in 1999 the amount of ballast water dumped in Australian ports from other countries was around 150 million cubic metres. By 2012 this had doubled to just over 300 million cubic metres - which is the equivalent of 128,000 Olympic swimming pools.

Most of this ballast water was delivered in bulk carriers returning after delivering iron ore and coal to places like China, says Cope.

"Bulk carriers are most likely to come to Australia empty before loading up," he says.

He says they are significantly larger than other vessels, including container vessels, and there are more bulk carriers travelling to Australia than other vessel types. For example, in 2012 there were almost 8000 bulk carriers versus 2000 container vessels.

"It's the combination of larger vessels, larger ballast discharges (due to vessels arriving empty) and more vessels arriving that mean most of the ballast water discharge is associated with bulk carrier traffic," says Cope.

Marine pest risk

Exotic marine organisms released in ballast water can cause damage to both fisheries and marine ecology.

Up to 10,000 species are estimated to be carried around the globe by ballast water every 24 hours, say Cope and colleagues.

"With volumes of maritime trade increasing globally, the risk of transporting invasive species in ships ballast water is increasing," they say.

But, say Cope and colleagues, the trends observed in Australia are unique because of our export of commodities.

One exotic organism presenting a problem to Australia is the Northern Pacific seastar (Asterias amurensis), which the government is attempting to control via, among other things, managing the release of ballast water.

"A doubling of ballast water could amount to a doubling of risk of transporting exotic marine organisms to Australia," says Cope.

"However, not all exotic organisms that arrive will be sufficiently suited to conditions in our waters such that they become established."

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