Invasive species in most Great Lakes ships

updated 9:13 a.m. ET April 20, 2005

MUSKEGON, Mich. - Oceangoing freighters that claim to be empty of ballast water before entering the Great Lakes routinely carry organisms that endanger the water bodies, a new report shows.

The ships often have saltwater algae, invertebrates, deadly bacteria and other organisms in muddy water at the bottoms of their ballast tanks, according to the study conducted by the University of Michigan and the National Oceanic and Atmospheric Administration shows.

Ballast water is stored below deck to keep ships stable. It is added or dumped based on cargo load and organisms can escape from the ballast tanks when ships in harbor take in or unload water.

“Many invasive species act like a computer virus. Once they get into the Great Lakes ecosystem they can clean it out,” said Cameron Davis, executive director of the Chicago-based Alliance for the Great Lakes. “In the Great Lakes, we are operating without a virus protection program.”

Authors of the study, reported in Tuesday’s editions of The Muskegon Chronicle, called for immediate action to stem the flow of exotic organisms and pathogens into the lakes.

INTERACTIVE Alien invaders Interlopers threaten native species

Researchers found that two-thirds of 42 ships sampled for the five-year study carried potentially deadly organisms in ballast tanks that were supposedly empty and clean, including cholera and cryptosporidium, the newspaper reported. In 1993, cryptosporidium from an unknown source contaminated Milwaukee’s drinking water system, killing more than 100 people and making 400,000 others ill.

Zebra mussels and 181 other species imported to the lakes threaten to drive out some native species at the base of the Great Lakes food web, endangering a multibillion dollar fishery.

Despite the potential threat and their calls for action, however, researchers cautioned that contaminated ballast water may not represent an immediate danger.

“We know there are pathogens in these ships, but we don’t know of any outbreaks of disease associated with ships’ ballasting practices,” said co-author Fred Dobbs, an oceanography professor at Old Dominion University.

The authors said one possible remedy would be to require all transcontinental freighters to completely empty and refill ballast tanks with salt water before entering the Great Lakes.

Michigan lawmakers are considering legislation to require shipping companies to obtain a ballast water discharge permit before operating in Great Lakes ports.

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