A new study may settle a debate over whether ships that travel between the Great Lakes, but don't go into the ocean, can transport invasive species.
These ships, known as lakers, are exempt from regulations that require ocean-going vessels to maintain ballast water treatment systems.
Samples from ten U.S. and Canadian flagged lakers taken during the summer of 2017 in western Lake Superior turned up six species of non-native zooplankton that had not been found in the area previously.
The study was designed to fulfill the Minnesota Pollution Control Agency's ballast water permitting requirements, and was carried out by the Great Waters Research Collaborative (GWRC), a project of the University of Wisconsin-Superior's Lake Superior Research Institute. It was funded by the U.S. Environmental Protection Agency.
Five species of non-native zooplankton were found in discharged laker ballast water. An additional non-native zooplankton was identified in uptake water.
Joel Brammeier is president and CEO of Alliance for the Great Lakes. He says the study supports tighter regulations on laker ballast water.
"We've got evidence showing that these live critters are moving around the Great Lakes in the ballast tanks of these freshwater ships, and the current practices are not sufficient to actually prevent that from happening," says Brammeier.
The study did not determine whether the non-native zooplankton could survive or become established in western Lake Superior.