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managing ballast water increase. The trade-off between levels of treatment and monitoring must be taken into account in assessing the cost effectiveness of strategies for managing ballast water.
The committee identified three levels of monitoring that might be needed for vessels that have either changed ballast at sea or have taken no action to control potential nuisance organisms in ballast. Vessels that have undertaken shipboard treatment of ballast water represent a somewhat different situation because monitoring requirements will generally be determined by the treatment method. The three proposed levels are as follows:
Level I. Log of change events and basic water quality parameter description
Level II. Basic bioactivity and indicator species description
Level III. Advanced biological analysis
Level I monitoring is the simplest and least expensive; level III is the most complex and expensive and is not likely to be practicable with existing technology. The committee anticipates that monitoring will be conducted at the lowest level necessary for determining with confidence that the discharge of ballast water does not pose an unacceptable risk of introducing nonindigenous aquatic species.
The committee believes that level I monitoring could be readily implemented and that it would be effective for ships that change ballast at sea. The basic parameters indicative of water quality—turbidity, salinity, temperature, dissolved oxygen content, and pH—can be readily measured using commercial instruments and test kits suitable for marine applications. In addition, records of ballast water operations are already kept by the vast majority of vessels. Examination of these records, in conjunction with testing of basic water quality parameters to confirm ballast movements, would generally provide adequate assurance that the ballast tanks contain oceanic rather than estuarine water. Thus, mandatory maintenance of ships' logs and records with data on all ballast-water movements for verification by shore officials would assist in implementing control measures and would reduce the need for detailed monitoring in many instances.
Vessels that have not treated or changed ballast water at sea are unlikely to be able to rely on level I monitoring approaches and will require level II or level III analyses.3 The presence of life in ballast water (level II monitoring) can easily be determined in a laboratory environment by assessing levels of bioactivity based on measurements of photosynthetic pigment, adenosine triphosphate, nucleic acids, and nutrients. Advanced biological analysis (level III monitoring) requires the taxonomic identification of organisms, possibly to species level; is time consuming and expensive; and cannot currently be performed on board ship. It may be possible to develop inexpensive biomonitoring techniques for ballast water that are amenable to shipboard use.
Exceptions may occur when vessels are transiting climatic extremes; for example, when they ballast in polar waters and deballast in tropical waters.