The quest to stop invasive species from reaching the Great Lakes in the ballast water of ocean-going ships is moving forward in Congress and at the state level.
But there remains a lot of disagreement over how strict new ballast requirements should be.
The U.S. House passed a measure earlier this month, and both the Coast Guard and Environmental Protection Agency are set to release their own new rules by the end of November. Meanwhile, New York has required water to be up to a thousand times cleaner than current international standards by 2013, a move that has sparked controversy.
Jim Sharrow, facilities manager for the Duluth Seaway Port Authority, said aggressive state rules like that could bring shipping in the Great Lakes to a standstill.
"If they want to impose rules on these ships that are different than what they see elsewhere in the world, it becomes very, very difficult to find ships that are interested in ever even coming back here," he said.
The Great Lakes are now home to nearly 200 non-native species. Over half of them came here hidden in ballast tanks deep in the bowels of cargo ships. When the ships flushed their tanks, into the Great Lakes the invaders went, including a finger-length fish called the round goby.
First discovered in Lake Superior in 1995, the voracious eater from the Black and Caspian seas is blamed for declining populations of native sculpin fish in the Great Lakes.
Three years later, fishermen reeled in gobies, recalls Doug Jensen, aquatic invasive species program coordinator for Minnesota Sea Grant.
"I asked them, 'how many did you catch?' They said 125," Jensen recalled. "I said, from how much shoreline?' They said, 'from one little spot about 30 feet in diameter.' And I knew we had a major infestation."
Efforts to prevent such infestations date back to at least 1993, when ships entering the St. Lawrence Seaway had to exchange their ballast water in the middle of the ocean. The saltwater kills a lot of the freshwater organisms left in the tanks. Then, in 2006, even empty ballast tanks had to be flushed with seawater.
Those uncelebrated moves have had a profound effect. Not a single new invasive species has been discovered in over five years, said Dale Bergeron, a maritime extension educator for Minnesota Sea Grant.
"Given the past dialogue of a new species every seven or eight months, this is unbelievably dramatic," Bergeron said.
Despite such success, there is wide consensus that a new national standard for ballast water is needed because there still are potentially harmful organisms that can survive in ballast tanks, even after saltwater flushing. The next step is for ships to install miniature treatment plants that kill the vast majority of organisms before the ballast water is discharged.
The controversy is over just how effective that equipment needs to be. Debate has focused on New York's tough measures to protect waters along the St. Lawrence Seaway to the Atlantic Ocean.
Sharrow and others say there's no proven technology to comply with New York's standard. But Marc Smith, a senior policy manager for the National Wildlife Federation, said the same thing was once true of gas mileage standards for cars.
"Let the standard drive the technology," Smith said. "We're firm believers that the higher standard you have, the technology will catch up to meet it."
But there's another problem with New York's tough new standard. It's impossible to tell if a ship has met it.
Experimental treatment systems are often put to the test at the Great Ships Initiative, a lakeside laboratory in Superior, Wis. After water has been treated, biologists painstakingly count the surviving organisms. But there's broad agreement that the technology doesn't exist yet to test at the level of precision required for New York's standard.
What's more, Bergeron said, there's no guarantee New York's tough standard will be effective.
"What does it mean in terms of protection? No one knows," he said. "For one species it might be 100 percent effective. For another species, it might have no impact whatsoever."
As federal officials mull their own standards, others, like Canadian government scientist Sarah Bailey, worry that the focus on removing invasive species from ballast water may be misplaced.
"The problem is that ballast water has been such a focus for the last 20 years that a lot of the other pathways have been ignored."
Bailey says other sources of invasive species, such as businesses that supply science classrooms, are still unregulated, and could deliver the next harmful foreign species that arrives in the Great Lakes.