Reports of marine and freshwater invasions of nonindigenous species are increasing as human activities continue to disperse organisms at a significant rate. There are many vectors for transferring species to new environments, either intentionally or unintentionally. A significant known pathway for species introduction is through ships' ballast water, the use of which is necessary for safe ship operations. The committee reviewed the state of practice of the prevention and control of nonindigenous species introduction in ships' ballast operations, and assessed potential alternative control strategies and management options for biological efficacy and practicability and for their impacts on ship and crew safety and on the environment. The committee's conclusions and recommendations are provided below.
Conclusion 1. No system or practice in use today will totally prevent the introduction of unwanted nonindigenous aquatic species into port or estuarine waters. Also, there are no off-the-shelf technologies specifically designed for treating ballast water that are suitable for use on board ship without some redesign and modification.
Conclusion 2. The IMO has developed and circulated a set of voluntary guidelines that are in use today. These guidelines are aimed at minimizing the introduction of unwanted aquatic organisms into the marine environment through their transport in ships' ballast water. Currently, the best option for minimizing such introductions is deballasting and reballasting a ship in mid-ocean areas. The
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6 Conclusions and Recommendations Reports of marine and freshwater invasions of nonindigenous species are increasing as human activities continue to disperse organisms at a significant rate. There are many vectors for transferring species to new environments, either intentionally or unintentionally. A significant known pathway for species introduction is through ships' ballast water, the use of which is necessary for safe ship operations. The committee reviewed the state of practice of the prevention and control of nonindigenous species introduction in ships' ballast operations, and assessed potential alternative control strategies and management options for biological efficacy and practicability and for their impacts on ship and crew safety and on the environment. The committee's conclusions and recommendations are provided below. Conclusions Conclusion 1. No system or practice in use today will totally prevent the introduction of unwanted nonindigenous aquatic species into port or estuarine waters. Also, there are no off-the-shelf technologies specifically designed for treating ballast water that are suitable for use on board ship without some redesign and modification. Conclusion 2. The IMO has developed and circulated a set of voluntary guidelines that are in use today. These guidelines are aimed at minimizing the introduction of unwanted aquatic organisms into the marine environment through their transport in ships' ballast water. Currently, the best option for minimizing such introductions is deballasting and reballasting a ship in mid-ocean areas. The
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United States requires the use of this technique for ships destined for the Great Lakes and upper Hudson River. Continuous flushing of ballast tanks is thought to be an acceptable alternative technique for changing ballast water at sea. However, neither of the options for changing ballast water is suitable for all ships or all trade routes under all circumstances. Conclusion 3. A ballast water operations plan, developed in conjunction with the ship cargo plan for each voyage, would provide flexibility in managing ballast water. Such a plan would take account of available information on locations and times when ballast is likely to contain unwanted organisms. Conclusion 4. The member states of IMO are currently drafting a proposed new annex to MARPOL 73/78. Essentially, this annex would make mandatory the use of the existing voluntary guidelines. A new annex to MARPOL 73/78 probably would not be in force before the turn of the century. In the meantime, some countries already are establishing unilateral regulations for the control of ballast water introductions. Such unilateral controls could have significant negative consequences for ships in worldwide trade. Conclusion 5. Developing regulations to control ballast water operations will be most effective at the international level. Without a governing international framework, and considering the diversity of vessels, trade routes, and ecosystems, controls tailored to local circumstances could lead to a patchwork of national (and state) regulations and resulting difficulties in compliance. The scientific and technical basis for ballast water regulations needs to be updated continuously to take advantage of R&D in the United States and other countries that leads to a better understanding of the problem of aquatic nuisance species and improved technologies for controlling ballast water. Conclusion 6. Early involvement of all interested parties is important to the successful development and implementation of guidelines and regulations for the control of ballast water. The problem of nonindigenous species transfer has implications for society as a whole and is not simply an issue for the shipping industry. Conclusion 7. Onboard systems for treating ballast water would give ships the most flexibility for managing ballast water, although port-based systems may offer some advantages. Experience with land-based waste water treatment systems is a useful starting point for assessing candidate technologies for treating ballast water on board ships. However, the operational constraints associated with shipboard use, including the high flow rates associated with pumping ballast water and the presence of sediment, impose additional demands on candidate systems.
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Conclusion 8. The most promising technologies for successfully treating ballast water on board ships appear to be physical separation techniques. Filtration could remove all materials, down to a predetermined size, during uptake, thus removing many unwanted organisms from ballast water. Using filtration is applicable to most ships, regardless of the characteristics of the water being taken up for ballast. Continuous backwash filtration is the most favorable candidate technology for use on board ships based on environmental, health, safety, effectiveness, and cost considerations. The size of current media filtration systems precludes their use on board ship, but their performance and design could be optimized for compatibility with ships' operations, for example, by reducing their size and providing the capability to handle high flow rates. Conclusion 9. Chemical and thermal technologies are potenially acceptable alternatives to filtration for treating ballast water on board ships. Further investigation is needed to establish, with more confidence, the relationship between biocidal dose or temperature and the time needed to kill or inactivate unwanted organisms. Development work is also required to optimize system designs for shipboard implementation. Conclusion 10. Some emerging electro-treatment technologies have shown encouraging results in laboratory tests. However, all technologies investigated—aside from filtration, chemical and thermal treatments—appear to have major limitations and, therefore, require extensive development for possible onboard application. The transition from laboratory scale to shipboard systems carries high technical risk, and development may be extremely costly. Conclusion 11. Ultraviolet, acoustic, magnetic, and oxygen-deprivation technologies for treating water have been successful in selected land-based applications, but these technologies have not demonstrated their effectiveness in treating a wide range of aquatic species, especially on board ships. Therefore, they are not considered to be prime candidates for treating ballast on board ships when they are used alone. Conclusion 12. Certain treatment approaches would cause byproducts or residuals to be discharged overboard. As a general practice, discharges to the environment (e.g., chemicals filtrates, heated water) resulting from treating ballast water should be minimized. The trade-offs between the risk of introducing nonindigenous aquatic nuisance species and the risk of releasing small quantities of residuals produced from treating ballast water require further evaluation. Conclusion 13. Questions remain regarding appropriate levels of risk of introducing unwanted organisms: What level of reduction of biological activity is necessary? What standard can be used to declare that a particular treatment has
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been effective? How clean is clean? Better databases on the biology of aquatic organisms would help address these questions by providing more extensive data for risk assessments. Meanwhile, probabilistic risk analysis based on limited available data can be a useful indicator of cost-effective management strategies. Conclusion 14. The implementation of methods for managing ballast water will require the development of practical measures for verifying compliance and assessing accountability and responsibility; therefore, automated monitoring and the required record keeping are desirable so that crew members and regulating authorities can readily and effectively ensure that agreed-upon standards have been met. If individual species have been identified, thereby raising concerns about ballast water discharge, monitoring procedures for source water and ship-held water need to be established to determine whether or not treatment is necessary. It is essential that any treatment be monitored for effectiveness using automated procedures that require little crew intervention, other than noting whether or not standards have been met. Conclusion 15. Turbidity may currently be the most effective indirect indicator of the possible presence of living organisms in ballast water. Basic water-quality parameters can be monitored by automatic inline equipment that provides continuous readouts for subsequent computer storage or direct transmission to shore. Conclusion 16. One proposed approach to monitoring shipboard management practices involves a "sampling and dispatch" method. Chronic carriers of known unwanted aquatic species would be required to air freight samples of their ballast water to authorities at the destination port for testing. When the results are known, the ship would be instructed whether or not some form of treatment is required in transit. Such an approach would require careful sampling of ballast water and the establishment of appropriate test facilities. Conclusion 17. It would be helpful in identifying possible introductions if each port were to develop a monitoring program based on internationally agreed-to standards to establish an ongoing database of organisms present in its waters. RECOMMENDATIONS Recommendation for the U.S. Coast Guard. Managing the unintentional introduction of nonindigenous organisms into U.S. waters through ballast water should follow two parallel courses: Support current international activities conducted under the auspices of IMO. Introduce national voluntary guidelines aimed at minimizing the risk of
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introductions until such time as mandatory international standards can be developed. These guidelines should require a plan for ballast water loading and discharge, developed in conjunction with the cargo plan for each voyage. Recommendation for the Aquatic Nuisance Species Task Force. The following actions should be taken as part of the cooperative national program to prevent unintentional introductions of nonindigenous organisms through ballast water: The United States should support and encourage the early elaboration of a new annex to MARPOL 73/78 making mandatory the use of the existing voluntary guidelines; meanwhile, the IMO-sponsored voluntary guidelines should be continuously reviewed and updated. The cognizant U.S. authority,1 as a matter of priority, should be tasked with developing domestic guidelines to minimize the translocation of unwanted nonindigenous organisms among U.S. ports by vessels engaged in trade along U.S. coasts. All interested parties should be involved from an early stage in formulating such guidelines and in developing ways to implement them. The associated U.S. authorities should sponsor and encourage further research and development for killing or removing aquatic organisms in ballast water. In this regard, options for treating ballast water should not be limited to technologies for shipboard use. Shoreside treatment should be investigated as a possible alternative. Recommendation for the Aquatic Nuisance Species Task Force. National research and development, including one or more demonstration projects, should focus on the following: optimizing the filtration approach to treating ballast water identifying the level of biological activity that indicates that treatment has reduced the risk of species introduction to an acceptable level developing automated monitoring systems suitable for shipboard use To avoid duplication of effort, these activities should take into account related research and development in other countries. Recommendation to the Aquatic Nuisance Species Task Force. The results of this study should be disseminated to coastal states, including states bordering the Great Lakes. Recommendation for the U.S. maritime industry. At the same time research and development are undertaken to address long-term solutions for controlling 1 The cognizant U.S. authority may be the Coast Guard, the state, or the port authority, depending on circumstances.
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introductions of nonindigenous aquatic organisms, the U.S. maritime industry should pursue implementation of a combination of practices for managing ballast water and the control options described herein, within the framework of existing international guidelines. Recommendation for the member states of IMO. Future international considerations should include establishing guidelines for baseline sampling of ports for specific organisms. Samples should be tested to agreed-upon international standards to facilitate comparisons of the water of each ballast uptake port with the water of receiving ports. Recommendation for the member states of IMO. In future discussions and updates of the existing voluntary guidelines (IMO Assembly Resolution A.774(18), 1993), further consideration should be given to the maintenance of appropriate ships' logs and records of ballast water movements and any management practices used. These data could be valuable when used in conjunction with measurements of basic water-quality parameters to verify that ballast water has been effectively managed.
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