But in 2017, UW-Superior researchers tested the ballast water tanks of eight U.S. and Canadian lakers traveling from the four lower Great Lakes to western Lake Superior. Their 2018 report documented several species of tiny zooplankton no one had previously recorded in Lake Superior — one of which had never been found in any Great Lake. The report followed Canadian research that found nonnative species in 90 percent of laker ballast water samples.

The Wisconsin researchers offered several recommendations, including developing workable treatment systems.

The Lake Carriers’ Association cooperated with the researchers by allowing them to board the ships and collect samples as part of a project required by the Minnesota Pollution Control Agency. But the group interpreted the results differently.

It criticized the study’s sampling as limited, and said it didn’t prove that laker-transported species could survive in new lakes.

“Let’s do some more work and get some more data to determine whether this study is telling us something new, or if these are limited data points that don’t reflect bigger issues and trends in the Great Lakes,” Jim Weakley, the group’s president, said following the report’s release.

Prihoda, the UW-Superior researcher, agreed having data covering a whole shipping season would give researchers a clearer glimpse at lakers’ role in invasions. She also acknowledged research is scarce about whether species were becoming established in new lakes after riding in laker ballast tanks. But waiting to take action is risky, Prihoda said.

“The thing is, once an organism becomes established, it could become invasive and spread. (It’s) too late at that point to do anything about it,” Prihoda said.

The Lake Carriers’ Association declined to allow Wisconsin Watch/Wisconsin Public Radio and Bridge Magazine to board a ship to report this story. Rayburn said the policy recommendations stemming from the UW-Superior study made captains more hesitant to welcome outside observers.

“We just want this to be more educational than judgmental,” he said.

New rules looming

Environmentalists hope research advances will give the EPA grounds to plug the regulation exemptions for lakers.

The agency is drawing up new standards by 2020 for dumping ballast water and the Coast Guard will craft rules for enforcing them by 2022. But a Coast Guard spokesman Richard Everett said whether those standards would apply to lakers is still to be decided.

The legislation signed by President Donald Trump in December was a compromise between environmentalists and the shipping industry after an earlier attempt in Congress to loosen ballast water protections for salties. It preserved the EPA’s Clean Water Act Authority to set ballast water standards, but it also made it difficult for states to set their own, stricter rules.

The wide-ranging law includes $50 million for invasive species prevention efforts. Molly Flanagan, vice president for policy at the Alliance for the Great Lakes, a Chicago-based environmental group, said the money could be used for laker ballast water research.

“We’re rapidly going to be running up against a situation where lakers are out of excuses and are going to have to treat their ballast water,” she said.

Cangelosi of Penn State said U.S. regulators should look for creative solutions. For example, regulators could require lakers to target specific known organisms in ballast water.

“I feel for the lakers because they are not bringing these things in (from overseas),” Cangelosi said. “A lot of the things that we worry about come in with the salties and then the lakers are caught holding the bag — moving it all around the lake.”

Danielle Kaeding of Wisconsin Public Radio contributed reporting.