Ballast Water Invaders
Wednesday 08 November, 2000
Ballast Water Invaders
Commercial ships are transferring diseases like cholera around the world, according to new scientific research. Biologists in the US have discovered that the ships' ballast water, which is used to stabilise the vessels at sea, contains a variety of potentially dangerous micro-organisms. The scientists say these can harm both humans and ocean wildlife. Helen Sewell of BBC Science reports.
Cholera in the water
Ships are designed to carry heavy cargoes and can be unstable when empty so they take in water as ballast. They discharge this at ports of call and en route, dumping more than 79 million tonnes every year into the seas near the US alone.
A group of marine biologists has examined ballast water from 15 ships coming into Chesapeake Bay on the East Coast of America. The vessels all came from Northern Europe and the Mediterranean.
Writing in the journal Nature the researchers, led by Gregory Ruiz of the Smithsonian Environmental Research Center, revealed that every ship they checked was carrying bacteria which cause cholera - a fast-spreading disease which can kill half the people it infects. The report states:
‘Ballast tanks carry a diverse community of organisms, resulting in many biological invasions. Pathogens [harmful microbes], including those affecting humans, are common in coastal waters and can be transferred in ballast water.’
Sea hitch hikers
The biologists say it is not just humans who are at risk. They believe that bacteria and viruses from ballast water frequently invade coastal ecosystems. But no one knows the full extent or effects of this discharged cocktail of potential pathogens.
Ballast water is untreated seawater and, if the conditions are right, it is possible that whatever is alive in the water when it is collected, will grow and could even breed. It has already been shown that other organisms, such as carnivorous comb jellies, have traveled the world in ship ballast water, with sometimes devastating impacts on the local environment.
Previous studies in Australia have also revealed all sorts of sea hitchhikers – some more welcome than others. In the 1970s two fish species, previously only found in Japan and North East Asia, were found in Sydney Harbour. The Yellowfin Goby and the Striped Goby were thought to have been introduced through the ballast waters and although an exotic addition to the water, it was feared that the Yellowfin would compete with existing species, consequently having a major influence on the natural order of predators.
Reducing the organisms
In an attempt to reduce the number of organisms present in ballast water, in 1990, the Australian Quarantine and Inspection Service (AQIS) introduced voluntary guidelines. Whilst the guidelines are not enforced by law, they could go some way to protecting marine species and ultimately human life.
The AQIS suggestions include filtering the ballast water as it is collected, eliminating organisms in the water during the voyage and treating the water as it is discharged in the port. Avoiding the organisms by collecting the ballast from deep water is a further consideration.
Whilst filtering could be effective for eliminating larger organisms, advanced filtering systems would be necessary to collect water-borne micro- organisms. If this system were to be implemented when the water was onboard ship, vessels would need to be significantly modified.
Re-ballasting the ship whilst at sea is another option. Exchanging the original water mid-ocean could reduce the survival rate of the organisms. However, as ships are designed to take ballast water on in still waters, there is a danger that exchanging water mid voyage could upset the balance of the vessel.
Sterilising the water with chemicals also seems a logical solution. Just as sewage is treated with chlorine or hydrogen peroxide, it is possible that ballast water could be treated either on collection or when discharged at the port. However there are two problems with this method – firstly it is costly and secondly the large doses of chemicals could have a detrimental impact on the environment.
Technological developments
All of these treatments have their benefits and drawbacks, however as the researchers at Chesapeake Bay warn, despite growing concern about the global spread of diseases, the potential for ships to carry micro-organisms around the world has been ‘virtually unexplored’. Recognising the benefits of technological advances Ann Pesiri Swanson, Executive Director of the Chesapeake Bay Commission added:
‘International efforts represent good interim steps in reducing the risks of ballast water organisms, but it is increasingly recognised that a technological solution or improved ballast management practices may provide eventual answers to prevent these invasions.’
The biologists have therefore called for immediate research into the international transfer of ballast water and it’s inadvertent cargoes.
| BBC World Service | http://www.bbc.co.uk/worldservice/sci_tech/highlights/001108_ballast.shtml |
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Ballast Water Invaders
Commercial ships are transferring diseases like cholera around the world, according to new scientific research. Biologists in the US have discovered that the ships' ballast water, which is used to stabilise the vessels at sea, contains a variety of potentially dangerous micro-organisms. The scientists say these can harm both humans and ocean wildlife. Helen Sewell of BBC Science reports.
Cholera in the water
Ships are designed to carry heavy cargoes and can be unstable when empty so they take in water as ballast. They discharge this at ports of call and en route, dumping more than 79 million tonnes every year into the seas near the US alone.
A group of marine biologists has examined ballast water from 15 ships coming into Chesapeake Bay on the East Coast of America. The vessels all came from Northern Europe and the Mediterranean.
Writing in the journal Nature the researchers, led by Gregory Ruiz of the Smithsonian Environmental Research Center, revealed that every ship they checked was carrying bacteria which cause cholera - a fast-spreading disease which can kill half the people it infects. The report states:
‘Ballast tanks carry a diverse community of organisms, resulting in many biological invasions. Pathogens [harmful microbes], including those affecting humans, are common in coastal waters and can be transferred in ballast water.’
| |
|  Listen to Gregory Ruiz explain the problem of the Zebra mussels found in the Great Lakes in the 1980s |
| |
Sea hitch hikers
The biologists say it is not just humans who are at risk. They believe that bacteria and viruses from ballast water frequently invade coastal ecosystems. But no one knows the full extent or effects of this discharged cocktail of potential pathogens.
Ballast water is untreated seawater and, if the conditions are right, it is possible that whatever is alive in the water when it is collected, will grow and could even breed. It has already been shown that other organisms, such as carnivorous comb jellies, have traveled the world in ship ballast water, with sometimes devastating impacts on the local environment.
Previous studies in Australia have also revealed all sorts of sea hitchhikers – some more welcome than others. In the 1970s two fish species, previously only found in Japan and North East Asia, were found in Sydney Harbour. The Yellowfin Goby and the Striped Goby were thought to have been introduced through the ballast waters and although an exotic addition to the water, it was feared that the Yellowfin would compete with existing species, consequently having a major influence on the natural order of predators.
|
Reducing the organisms
In an attempt to reduce the number of organisms present in ballast water, in 1990, the Australian Quarantine and Inspection Service (AQIS) introduced voluntary guidelines. Whilst the guidelines are not enforced by law, they could go some way to protecting marine species and ultimately human life.
The AQIS suggestions include filtering the ballast water as it is collected, eliminating organisms in the water during the voyage and treating the water as it is discharged in the port. Avoiding the organisms by collecting the ballast from deep water is a further consideration.
Whilst filtering could be effective for eliminating larger organisms, advanced filtering systems would be necessary to collect water-borne micro- organisms. If this system were to be implemented when the water was onboard ship, vessels would need to be significantly modified.
Re-ballasting the ship whilst at sea is another option. Exchanging the original water mid-ocean could reduce the survival rate of the organisms. However, as ships are designed to take ballast water on in still waters, there is a danger that exchanging water mid voyage could upset the balance of the vessel.
Sterilising the water with chemicals also seems a logical solution. Just as sewage is treated with chlorine or hydrogen peroxide, it is possible that ballast water could be treated either on collection or when discharged at the port. However there are two problems with this method – firstly it is costly and secondly the large doses of chemicals could have a detrimental impact on the environment.
Technological developments
All of these treatments have their benefits and drawbacks, however as the researchers at Chesapeake Bay warn, despite growing concern about the global spread of diseases, the potential for ships to carry micro-organisms around the world has been ‘virtually unexplored’. Recognising the benefits of technological advances Ann Pesiri Swanson, Executive Director of the Chesapeake Bay Commission added:
‘International efforts represent good interim steps in reducing the risks of ballast water organisms, but it is increasingly recognised that a technological solution or improved ballast management practices may provide eventual answers to prevent these invasions.’
The biologists have therefore called for immediate research into the international transfer of ballast water and it’s inadvertent cargoes.
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