Invasive Species in Ship Ballast

S T.  C L A I R,   M i c h.,   Aug. 14 -- Capt. Pat Nelson gazes about the cavernous, mud-slicked interior of the ballast tank deep in thebowels of the 1,000-foot cargo ship, Oglebay Norton.

“This thing holds more than a million gallons, and that’s justone tank,” Nelson says. “How are you supposed to sterilize thismuch water?”

The question is at the center of a debate that has turned thelowly ballast tank into one of the Great Lakes region’s hottestpolitical battlegrounds. The issue: how to stem an invasion byballast stowaways, such as the hated zebra mussel without sinkingthe shipping industry.

A Soupy Mixture

Ballast is a soupy mixture of water, sediment and seaweed whoseweight keeps ships stable during voyages. But it’s also home to avast array of aquatic organisms that end up being hauled thousandsof miles and then released into new territories as ships dumpballast while taking on cargo in port.

Once in their new homes, the uninvited immigrants can multiplyquickly and wage war on native species, gobbling up their food andstealing their habitat.

Among the most notorious are the parasitic sea lamprey, whichdecimated the native trout population by the mid-1900s, and thezebra mussel, which arrived in the late 1980s and did hundreds ofmillions in damage by clogging water pipes.

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Governments around the world are trying to close their bordersto unwanted biological travelers. But the sense of urgency isparticularly strong in the Great Lakes, where nuisance aliens havedrastically altered the world’s largest surface fresh water system.

“It’s an ecological disaster,” says Mark Coscarelli, anenvironmental specialist with Michigan’s Office of the Great Lakes.

“Exotic species are the No. 1 issue facing the lakes, thesingle largest threat,” says Ken Sikkema, chairman of the MichiganSenate’s environmental affairs committee.

An estimated 145 aquatic foreigners have taken up residence inthe Great Lakes ecosystem since the early 1800s — many, though notall, brought by ballast. More are on the way, scientists warn.