Ballast Water
What is ballast water?
What are the potential problems associated with ballast water?
What is the Scottish Government doing to minimise introductions of non-native species?
What is ballast water?
Ships use ballast water to adjust their stability and trim when sailing without cargo, when partially loaded and during bad weather This is important both for safety reasons and for the economic operation of vessels in the modern shipping industry.
It is difficult to accurately estimate how many tonnes of ballast water are transported worldwide and estimates range from 2 - 10,000 million tonnes of ballast water transported annually. Ballast water discharges in the vicinity of Scottish Ports have been estimated as being between 17 and 26 million tonnes.
What are the potential problems associated with ballast water?
Ballast water can present serious consequences to the marine environment through the accidental introduction of non-native species when ballast water is discharged in harbours or coastal waters.. Of the thousands of species transported worldwide in ballast water some may be non-native in the waters into which they are discharged and while many may not become established in their new environment, or may cause no noticeable harm, others may have detrimental effects. For example, introduced species can transform ecosystems, alter natural habitats and threatened native and endangered species through competition for food, habitat and resources. They can also cause significant damage to economic interests such as fishing and may affect public health through the occurrence of harmful algal blooms.
While there is no firm evidence to date to suggest that ballast water discharges have resulted in species introductions within Scottish waters, there have been three recent concerns surrounding potential ballast water transfer:
- Possible transfer of the parasite Gyrodactylus salaris from Norway. This parasite affects salmon and trout populations, causing concern for Scottish fisheries and aquaculture.
- Possible transfer of phytoplankton that can form harmful algal blooms or 'red tides'. The public health implications are well documented and include Paralytic Shellfish Poisoning (PSP) which can cause severe illness in humans.
- Scientific research has shown that human pathogens may be transported in ballast water of ships including the cholera bacteria Vibrio cholerae.
What is the Scottish Government doing to minimise introductions of non-native species?
The International Maritime Organization (IMO) held a conference in 2004 at which an 'International Convention for the Control and Management of Ships Ballast Water and Sediments' was agreed. The Convention will enter into force 12 months after ratification by 30 States, representing 35 per cent of world merchant shipping tonnage and to date (March 2010) has been ratified by 21 states representing 22.63% of the world merchant shipping tonnage.
The Ballast Water Convention sets out a discharge standard that has to be met by vessels. This is based on discharging allowable concentrations of organisms in different size categories and, once the Convention is ratified, will be phased in depending on the size and the age of the vessel.
Vessels will have to install ballast water treatment systems in order to treat the ballast water to ensure it meets the standard and the Scottish Government is working alongside Marine Scotland - Science Marine Laboratory (MSS-ML) and the Maritime and Coastguard Agency (MCA) in the ongoing process to review ballast water treatment and management methods. Further work is also being carried out to produce standard methods for sampling ballast water to ensure compliance with the ballast water discharge standards contained within the convention.
A variety of treatment and management methods are currently available or under development and the IMO has a process to review the efficacy of these systems. A useful review of the available technologies is available online.
Further information on ballast water introductions can be found at Marine Scotland Science and International Maritime Organisation (IMO).