Prevention is the Key to Cleaner Great Lakes

by Kieran Mulvaney

Originally published in The Detroit News, 6/11/97.

---

This month, the Great Lakes region is witnessing the first phase of an important experiment. If successful, it could greatly reduce the risk of further introductions of exotic animal and plant species through ships' ballast water-a problem that scientists have called an "ecological disaster."

Around the world, invading organisms are decreasing native species, transforming ecosystems and causing serious economic damage. In the Great Lakes, the focus is on the zebra mussel-largely because of the losses it has caused by blocking intake pipes. In addition, concern is being expressed about the possible consequences for native fish, and hence local fisheries, of the growing numbers of introduced goby and' ruffe. But what is happening in the Great Lakes is occurring with other species in aquatic environments everywhere.

Just a few examples among many:

• The comb jelly, a native of the U.S. Atlantic coast, appeared in the Black and Azov seas in the early 80s and underwent a massive explosion in numbers in the late 80s. It became the dominant species in the ecosystem there, driving down populations of native species and causing the collapse of regional fisheries.
• The introduction of more than zoo exotic species has transformed the ecosystem of San Francisco Bay. The Asian clam, for example, is now found on the bay floor in densities exceeding 10,000 per square meter.
• The invasion by the purple loosestrife plant of wetlands in 41 states has in some areas displaced half the original plant coverage and contributed to the decline of bird and turtle species by destroying their habitats.

At least 4,500 exotic species have established free-living populations in this country alone. It is estimated that, at any given time, a further 3,000 species-mostly in the form of microscopic spores and larvae-are in motion in the ballast water of ocean-going ships around the world; a staggering 11,507 million estimated gallons of that ballast are discharged into U.S. waters every year.

The Fish and Wildlife Service considers exotic species, including those introduced via ballast water, to have been a contributing factor in the listing of 16o species as threatened or endangered, and the major cause of listing for 41 species. The Office of Technological Assessment estimated that losses to industries such as agriculture, forestry and fisheries as a result of introduced species could be as much as several billion dollars each year.

Unfortunately, there are too many exotic species already established to combat all of them. Nor is it possible to focus on controlling the species that seem most likely to become problematic. Some species may appear to fit into their new surroundings, considered innocuous or even beneficial additions to the environment until building up in sufficient numbers to become pests.

The key, therefore, is prevention. Hence the importance of the research in the Great Lakes. Lasting all through the shipping season, the cargo vessel Algonorth will carry an experimental filtration system, designed to block the passage of tiny organisms that would otherwise be emptied into the environment every time the ship discharged its ballast water. The experiment-coordinated jointly by the Northeast-Midwest Institute and the Lake Carriers' Association, with funding by the Great Lakes Protection Fund-will be keenly watched by experts around the world, according to Jim Carlton, a Pew fellow and one of the world's authorities on introduced species in aquatic environments.

There is no guarantee of its success, although those involved with the program are optimistic.