THE UNITED STATES has declared war on alien invaders -- the potentially dangerous infiltrators of American waters that secretly travel in ballast water tanks of giant ocean-going ships.
That's especially good news for the Chesapeake Bay, where more than 3 billion gallons of foreign water are dumped by cargo vessels each year. Hidden in that ballast water (taken on by ships for stabilization) are thousands of exotic, alien organisms that pose dramatic threats to the ecology of the estuary.
The new National Invasive Species Act calls for ships to discharge their ballast tanks 200 miles from coastal waters, monitoring of the voluntary effort and funding of research to develop anti-invader techniques.
Thousands of foreign invader species -- from microorganisms to fish and crabs -- carried as stowaways in ballast water tanks are dumped in U.S. waters. Most non-native species in the Chesapeake are traced to ballast dumping.
Many transplanted species do not survive, some can be beneficial but some are decidedly dangerous, with potential to spread disease, wipe out native species and cause costly damage. This man-caused ecological exchange is "a game of biological roulette," with unforeseeable consequences, scientists warn.
The most notorious invader of U.S. waters is the European zebra mussel, which clogs water-intake pipes, threatens native freshwater mussels, alters food chains of fish and promotes explosions of harmful algae. The alien mollusk has spread rapidly since its transport in ballast water to the Great Lakes in the 1980s.
Exchanging ballast in the high-salt oceans can kill most alien species before they enter the U.S. waters; ocean species taken on in new ballast are unlikely to survive in low-salt mainland waters. That's not the ultimate solution: ship designs and sea conditions can prevent full compliance. But a two-year voluntary, educational program by the Coast Guard for ships visiting Chesapeake ports has achieved more than 80 percent compliance, a hopeful sign.
The Coast Guard can fine violators, if voluntary programs fail, under the new U.S. law. Research to develop heat or chemical treatment technology promises more effective longer-term prevention of this insidious, permanent biological pollution of our waters.
Pub Date: 11/16/96