A study has confirmed that lakers — the freighters that move iron ore, coal and other bulk material between the Great Lakes in the US — carry invasive species that originated in countries thousands of miles away.
The study from the Great Waters Research Collaborative found six species of foreign zooplankton when researchers checked the ballast of 10 different lakers from both US and Canadian companies.
The report said that the invaders first came to North American ports in saltwater ships, but were being moved between the lakes by the lakers. Five of the foreign species, including one called the bloody red shrimp, have not yet established in western Lake Superior. The sixth species, Paraleptastacus wilsoni, had never been found in any of the Great Lakes before.
Some of the species live in harbour sediment and might have escaped standard methods of finding new species, the study found.
Sampling took place in 2017, primarily in the late summer through to early winter, and focused on ballast water discharges in Duluth and Superior of water loaded from ports in the lower four Great Lakes.
Forthcoming federal ballast water regulations that will require onboard water treatment in saltwater ships will not apply to ships that never leave the Great Lakes, although Minnesota has rules on the books that will require lakers to treat ballast the same way as for saltwater vessels.
Minnesota now has rules on the books to apply the International Maritime Organization standards to lakers after each boat’s first dry-dock starting in 2019, with all completed by about 2023, unless boat owners can convince regulators that it’s not possible. Wisconsin had a similar rule but recently dropped it.