The discovery of mature zebra mussels on the hydroelectric dam in Edmundston, New Brunswick, at Maine’s border where the Madawaska River flows into the St. John has put the state’s biologists on higher alert.
New Brunswick scientists found eight of the striped mussels on the dam last summer, and the organism’s DNA was detected in the St. John River beyond the dam using a technique that caught the genetic material in a filter.
It means that zebra mussels, which average an inch long, could already be establishing themselves in the St. John River, although none have been seen there yet, according to Dakota Stankowski, invasive species biologist at the Maine Department of Inland Fisheries and Wildlife.
Zebra mussels are filter feeders that very quickly drain nutrients from a body of water, which would endanger some of Maine’s prime fisheries if invaded, she said Tuesday.
The state is monitoring the Aroostook River, the Fish River chain of lakes, including Long Lake, the Deboullie Pond Reserve and some other bodies of water in northern Maine that are vulnerable to zebra mussels.
The mussels need lots of calcium and alkaline conditions, and all of the bodies of water being monitored have that. The Maine Department of Environmental Protection has identified 90 out of the state’s approximately 800 ponds and lakes that have from a moderate to a high probability zebra mussels could establish in them.
“Our lakes and ponds can naturally repel them, but it doesn’t mean that zebras can’t adapt,” Stankowski said.
Drifting juveniles likely died or the DNA flowed in from Canada are two possible reasons for why no mussels have been found in the St. John, she said.
The technique used to collect genetic material, called environmental DNA, allows scientists to identify at least the genus and sometimes the species of an organism by filtering water or air samples.
Waters infested with zebra mussels appear super clear and may be blue and pure looking, due to the lack of nutrients. The mussels’ presence alters the native populations of plants, fish and invertebrates by eating all of the phytoplankton and interrupting the food chain, she said.
Besides hurting the fishery, the mussels cause economic concerns as well. They attach to boats, docks, rocks on beaches, dams and other surfaces and clog drains and propellers. The shells are sharp so people cut their feet on them if they are on the beach.
Chemical treatment is about the only option to get rid of zebra mussels once they establish, but that would kill everything else in the body of water too. That’s why most of the state’s efforts center on preventing spread from one body of water to another, which Stankowski said is the first and last line of defense against the mollusk.
Part of that effort so far was to change a state education campaign encouraging people to clean their boats out between bodies of water into a law requiring them to do so. The “clean, drain, dry” legislation was signed into law in 2023 and requires boaters to drain out water and clean off plants and dirt gained in one lake or pond before entering another.
The mussels, which originated in eastern Europe, came to North America in ballast water in ships that entered the Great Lakes.
The next step is for the state to involve “community scientists” this summer. Community scientists are residents who report their sightings through standardized forms that are submitted to state biologists.
The state has used them in other projects, such as a 40-year atlas of amphibians and reptiles and the current owl pellet project.
“We need to keep an eye on this forever. They are not going away. With monitoring and outreach, we hope the proactive measures will prevent widespread infestation,” Stankowski said.