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Report Urges Saltwater Flushing to Kill Invasive Species Entering Great Lakes

Posted on: Wednesday, 11 July 2007, 00:18 CDT

By JOHN FLESHER

TRAVERSE CITY, Mich. (AP) - A new report proposes a simple way to prevent invasive species from sneaking into the Great Lakes aboard oceangoing cargo ships: just add salt water.

In a study released Tuesday, scientists said vessels should be required to flush their ballast tanks with full-strength seawater before entering the St. Lawrence Seaway, the passage to the lakes.

Doing so would kill many organisms that were scooped up in foreign ports where salinity levels are low, the study said. Even those that survive might be swept into the ocean, instead of winding up in the Great Lakes, said Thomas Johengen, a University of Michigan nutrient chemist and one of the study's leaders.

"This isn't a foolproof method," Johengen said in a phone interview.

"We look at it as an easy, interim approach until we have more of a technology-based treatment solution."

Ballast water is widely considered a leading source of aquatic invaders, which compete with native species for food and habitat. At least 185 have been identified in the Great Lakes, including zebra and quagga mussels, which clog water pipes and do more than US$150 million worth of damage a year.

U.S. coast guard regulations already instruct freighters bound for U.S. ports to exchange ballast water while at sea. But ships hauling cargo can avoid the requirement by declaring they aren't carrying ballast.

Critics say those ships - known as NOBOBs (No Ballast On Board) - might have residue in their tanks harbouring living organisms. More than 90 per cent of the freighters entering the St. Lawrence Seaway are NOBOBs, the report said.

Last year, Canada required saltwater treatment of ballast water for all ships, including NOBOBs.

The U.S. coast guard recommended mid-ocean ballast tank flushing for NOBOBs in 2005. The agency didn't make it mandatory because the rulemaking process would have taken years and the effectiveness of saltwater flushing was still being studied, said Bivan Patnaik, environmental regulation co-ordinator.

In their three-year study, scientists at the University of Michigan and other institutions ran more than 70 laboratory experiments to determine how saltwater flushing affects various invertebrates. Among them: zebra and quagga mussels.

The tests were conducted in Lake Erie, Lake Michigan, Chesapeake Bay, San Francisco Bay and several European ports.

They confirmed "saltwater can be quite effective at reducing the risk of invasions from ballast water," said David Reid of the Great Lakes Environmental Research Laboratory in Ann Arbor, Mich., another project leader.

John Jamian, president of the Seaway Great Lakes Trade Association, said the shipping industry supports midocean ballast water exchange, although each vessel has its own policies.

Pumping water into ballast tanks when a ship already is loaded with cargo can be dangerous, he said.

"You've got to look at the safety of the crew and the structural integrity of the ship," Jamian said.

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On the Net:

-Great Lakes Environmental Research Laboratory: http://www.glerl.noaa.gov

Source: Canadian Press

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