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Marine Log

September 24, 2007

NOAA reports on ballast water exchange

NOAA and the Smithsonian have released a technical report that describes the effectiveness of ballast water exchange procedures as a way to reduce aquatic invasive species discharged into U.S. waters, including the Great Lakes and Chesapeake Bay.

"Research and development to produce alternative ballast treatment methods and technology-based ballast treatment systems should continue to be pursued as a high priority toward the reduction of organism transfers," said Richard Spinrad, assistant administrator for NOAA Oceanic and Atmospheric Research. "This report assesses what is currently known about ballast water exchange, and provides analysis of its likely effects."

NOAA's National Center for Research on Aquatic Invasive Species and Smithsonian Environmental Research Center analyzed the delivery of ballast water to the Great Lakes and Chesapeake Bay.

These studies indicate reductions in the risk of invasive species introductions as a result of ballast water exchange. The analysis provides further confidence that overall, there has been a decline in the risk of invasion from ballast water in these regions. In addition, the report addresses a potential gap in the coastal ballast management protection framework where ships traveling less than 200 miles from the U.S. coast are not covered.

"Measurements made aboard ships during normal operations demonstrate that ballast water exchange, when properly conducted, can be highly effective, removing or killing approximately 90 percent or more of the coastal planktonic organisms from most ballast tanks," said David Reid, senior physical scientist, NOAA National Center for Research on Aquatic Invasive Species. "Some residual coastal organisms may remain in ballast water after exchange, and also in tanks with residual water and sediments, both which may pose some invasion risk during subsequent ballast discharge."

"It is clear that ballast water exchange has significantly reduced species transfers and invasion risk associated with ships' ballast operations," said SERC senior scientist Gregory Ruiz. "But the expected (albeit reduced) rate of invasions for the organisms that remain after exchange is not known. This represents a gap in scientific understanding that limits effective management decisions."

The report suggests that a standardized survey program, targeting key coastal ecosystems in the U.S., could provide the high-quality data necessary to (a) assess current invasion risk and (b) measure the performance of multiple management actions, including those of ships and other transfer mechanisms, in terms of invasion occurrence. No such program currently exists.

The report (TM-142) is available here.