Invasive Species in the St. Lawrence Seaway

The St. Lawrence Seaway, the major shipping canal connecting the Atlantic Ocean with the Great lakes, has become a major conduit for invasive species. About a third of invasives in the Great Lakes region have come by that route, and many of them end up elsewhere in the continent.

Zebra and quagga mussels from the Black Sea clog intake structures for municipal water systems and power plants. The mussels also gobble plankton so voraciously that little is left for other organisms. Round gobies and other invasive fish beat out native fish for food supplies, harming the lucrative commercial and sport fishing industries. Ballast is even blamed for the emergence of viral hemorrhagic septicemia, often called "fish ebola," resulting in large fish kills in the past several years.

And as infected pleasure boats are hauled to other lakes or species swim and float into tributaries, or even the Mississippi River, invasive species that came in with the ballast are spreading throughout the United States. Large quagga and zebra mussel colonies have been found in California and Nevada and are threatening to spread through California's many miles of municipal water pipes.

Many of the invasive species have come through ballast, which is not well regulated.

There are no federal standards for ballast treatment, although the Environmental Protection Agency and the Coast Guard are working on requirements that should reduce the amount of live organisms in ballast water.

Since 1993, ships have been required to exchange their ballast in the Atlantic before entering the Seaway, replacing water from whatever port they had last visited with high-seas water containing little life.

But until 2008, U.S.-bound ships loaded with cargo and hence containing no ballast were exempt from any regulations. These ships are called NOBOBs, for No Ballast on Board. But their "empty" ballast tanks contain many tons of muddy slop teeming with bacteria, small marine organisms, eggs and larva.

NOBOBs typically unload their cargo -- often steel -- in Great Lakes ports like Detroit and Cleveland, suck water into their ballast tanks, then head to other Great Lakes ports -- Duluth, Toledo or Milwaukee -- to load up on grain and dump their ballast, now mixed with the biologically rich mud.

Stricter regulations are supposed to be on the way, but have been slow in coming.