Monitoring ships' ballast is complicated by the need to analyze not only the water column but also the sediment that accumulates at the bottom of tanks and holds. Periodic monitoring of sediment is necessary because sediment may be a source of transported organisms.
Under certain circumstances onboard monitoring systems are not practical or are too expensive to install. A system of ballast water sampling and dispatch has been suggested as an alternative to shipboard monitoring. Developing this approach for a range of organisms represents a major challenge in terms of both sampling and testing. It is also not clear if potentially harmful species can be identified as such prior to their introduction. However, baseline sampling of ports for the presence of specific organisms to standardized, internationally accepted criteria would be helpful in determining the risk associated with voyages between specified ports. Port baseline surveys represent a significant scientific undertaking and would require periodic updating.
The U.S. Coast Guard regulations for controlling nonindigenous species in ballast water in the Great Lakes, which were promulgated in response to P.L. 101-646, are the only mandatory regulations for managing ballast water in effect in the United States. The regulations apply to vessels that have operated outside the exclusive economic zone of either the United States or Canada. Overseas, Chile and the port of Haifa in Israel have introduced requirements making it mandatory that ballast water be changed prior to being discharged.
In addition to these mandatory requirements, there are a number of international, national, regional, state, and local initiatives to control introductions of nonindigenous aquatic nuisance species. In particular, the IMO has developed guidelines for preventing the introduction of unwanted aquatic organisms from discharged ballast water and sediment, and IMO member states have been requested to apply these guidelines on a voluntary basis. The Marine Environment Protection Committee of IMO is currently drafting a set of regulations for a possible new annex to MARPOL 73/784 that would make use of the guidelines mandatory. If acceptable to IMO's contracting nations, the new annex could be ratified around the turn of the century. The guidelines can be continuously updated, incorporating the results of research and development and improved technologies, without changing the regulations of the annex.
In an international context, the committee concluded that regulations to control introductions would be most effective in the form of an amendment to an existing international convention or treaty. The introduction of unilateral legislation and regulations by individual nations would result in a complicated ''patchwork" of