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A research team including Old Dominion University oceanographer Fred Dobbs has proposed relatively inexpensive ways to combat nonnative species that hitchhike in ships' ballast tanks into the Great Lakes.

Researchers found that flushing ballast tanks with full-strength seawater will kill some of the fresh water species that could pose an invasion threat if introduced into the fresh water of the Great Lakes.

Dobbs said the saltwater rinse would not kill the great majority of nonnative saltwater species that pose a threat to the Chesapeake Bay. However, this practice and others proposed by the research team could be helpful if applied to ships entering the bay, he said.

"The best management practices-BMPs-we suggest in our Great Lakes research study may be taken as being broadly applicable to Chesapeake Bay ports as well," he said. "In the Chesapeake Bay, our potential invaders are saltwater organisms that are unlikely to be killed outright by exposure to seawater. But the concentrations of these organisms in tanks will be decreased by at-sea exchanges."

Another practice recommended in the researchers' final report calls for muddy water taken in as ballast to be dumped as soon as possible to avoid sediment accumulation in tanks. "This and other BMPs make sense both in the Great Lakes and the Chesapeake Bay," Dobbs said.

Some of the research team's experiments exposing invertebrates to saltwater were carried out in the Chesapeake Bay, and they showed, as Dobbs pointed out, that organisms originating in low-salinity ports don't live long when they come in contact with full-strength seawater.

Dobbs, a microbiologist and professor in the Department of Ocean, Earth and Atmospheric Sciences at ODU, is an expert in the ecology of microorganisms in ships' ballast water. Former ODU oceanography faculty members Martina Doblin and Lisa Drake also have worked with the research group. Doblin now is affiliated with the University of Technology in Sydney, Australia, and Drake with the U.S. Coast Guard Academy in New London, Conn.

Other researchers were from the Great Lakes Environmental Research Laboratory, University of Michigan, the University of Windsor in Ontario and the Smithsonian Environmental Research Center.

The three-year Great Lakes NOBOB (no ballast on board) assessment project focused on vessels that arrive at Great Lakes ports with a lot of cargo and very little ballast. The quantity of ballast is so small, in fact, that the vessels qualify as NOBOB and are exempt from some controls aimed at limiting the introduction of nonnative species via ballast water.

But quantities of ballast water too small to pump, as well as sediment, usually are in the tanks of NOBOB vessels, and these can harbor exotic organisms. If a ship offloads cargo at one Great Lakes port, it must take on ballast to maintain stability and nonnative species in the dregs will mix in with this new water. If this ship then takes on cargo at another Great Lakes port and has to dump ballast, the nonnative species can find their way into the Great Lakes.

The researchers recommend in a final report that ships destined for the Great Lakes regularly perform saltwater flushes of all technically empty ballast tanks when transiting oceans.

In 2005, a U.S. Coast Guard statement encouraged mid-ocean flushing, but the procedure has yet to be added to the Code of Best Practices for Ballast Water Management that applies to NOBOB vessels using domestic Great Lakes harbors. Canada, on the other hand, adopted management regulations in 2005 that require the flushing or some other salt treatment of ballast water, including residual water in NOBOB vessels, before ships can take on cargo at Canadian Great Lakes ports.

David Reid, a researcher with the Great Lakes Environmental Research Laboratory of the U.S. National Oceanic and Atmospheric Administration (NOAA) and a co-leader of the NOBOB study group, told news media, "This report is actually providing, finally, the basis of support for why the Canadians did what they did."

The latest report, which is titled, "Identifying, Verifying and Establishing Options for Best Management Practices for NOBOB Vessels," was funded by the Great Lakes Protection Fund, with support also from the Coast Guard and NOAA.

The saltwater treatments and other routine ballast tank maintenance procedures are consider low-cost alternatives to regulations that would require the use of sanitizing technologies employing chemicals, heat, ozone or ultraviolet radiation. These have been shown to be effective, but they are very expensive.

This article was posted on: July 30, 2007

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