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species. The potential presence of additional, similar species can then be inferred without actually undertaking a more extensive biological analysis. This indicator species approach is used in waste-water treatment, where certain organisms (e.g., enteric bacteria) are used as surrogates to predict the presence of pathogens in waste water, including bacteria, viruses, protozoans, nematodes, and flatworms.
Although the indicator species approach may not be useful for monitoring ballast water in all cases, it may be useful in specific instances. For instance, if ballast water had been taken up in an area known to harbor an unwanted species, that particular species might be searched for specifically. Particularly resistant forms known to present high risks (such as dinoflagellate cysts) might be selected for monitoring. At the same time, it could be assumed that, if a particular species were killed or removed, most other species would also be eliminated.
Level III Monitoring
Advanced biological analysis comprises collecting plankton samples from the water column and benthic samples from bottom sediment (if present), followed by taxonomic identification to the species level, if possible. Identification may be manual or flow cytometry, molecular probes, or immunofluorescence may be used (see Appendix H).
Level III monitoring with existing technology is probably not feasible except when the risk of introduction is very high. In particular, the time needed for advanced biological analyses is not compatible with shipping schedules. However, the development of automated techniques, such as immunofluorescence, may eventually allow onboard identification of specific taxonomic groups. A number of biochemical methods for monitoring water are currently under development and might be applicable to level II and level III monitoring in the longer term (see Appendix H).
MONITORING AFTER TREATMENT OF BALLAST WATER
In contrast to the generic approaches to ballast water monitoring described above, monitoring methods after ballast water has been treated on board may be closely tied to the method used to treat the ballast water. For example, it may be possible to monitor the effectiveness of biocide treatments by monitoring the presence and concentrations of residuals in ballast water.
Australian researchers have identified three steps needed when monitoring the treatment of ballast water on board ships (AQIS, 1993):
Record equipment operation to confirm that all ballast water has been appropriately treated.
Sample treated ballast water and sediment to check performance of the equipment.