Few species have had such a disastrous effect on Minnesota waters as the zebra mussel. As much as we might wish they weren’t, zebra mussels are a species that is well adapted to travelling among water systems and to reproducing explosively. Female zebra mussels can release 500,000 eggs per year, all of which can reach reproductive size within 12 to 18 months. Both the adults and veligers – larvae which drift in plankton and grow for three weeks before maturing to adulthood – are easily transported by watercrafts.
Veligers are most often transported by boats moving between water bodies when they are trapped in ballast tanks, live wells, etc. Adult zebra mussels attach themselves to objects with small, dark fibers called byssal threads. They clog intake pipes for water treatment and power plants, cover lake bottoms and pose dangers to swimmers’ feet, and cause damage to the boats they adhere to. It is estimated that zebra mussels alone cause over one billion dollars in economic harm per year to North America.
The ecologic damage zebra mussels cause is just as devastating. Zebra mussels smother out native bivalve mollusks, which have evolved over thousands of years to work within the ecosystem, keeping other species in check without running rampant. The invasive mussels further alter the energy flow by filtering massive quantities of microscopic algae from the water. Other species which rely on the algae for food are usually unable to compete with the zebra mussels’ prodigious growth, and the entire food web suffers for it.
The Minnesota Aquatic Invasive Species Research Center, a University of Minnesota entity, was started in 2012 to research the spread and effects of aquatic invasive species within state waters. The center’s zebra mussel work includes sequencing the genome to identify control options, studying the spread using population genetics, developing tests for early larvae detection, and studying the effectiveness of pesticides.
Adam Doll, a grad student at MAISRC, evaluated eight different boat compartments that hold water – like engines, ballast tanks, bilges, splash wells, live wells, etc. – to see how they might be aiding zebra mussel movement. He found that ballast tanks usually hold the most veligers. Some ballast tanks held up to 4,000 individual veligers that could be released into the next lake or river the boat visited.
Doll then studied how heating could affect veliger survival. Water held at 90˚F for 24 hours was able to kill all the veligers within a tank. The same success was achieved in three hours for water held at 100˚F. While the data is valuable, it is unlikely that everyone will boil the water in their boats for three hours every time they go out. Doll suggests simply drying boats completely before relaunching in a different water body, as this will have the same effect.
Luckily, boaters don’t have to fight invasives alone. Doll is trying to recruit another team to the fight: boat manufacturers. Certain design changes could keep aquatic invasive species out better, allow more efficient draining, and make it easier for inspectors to spot invasives. Doll has spoken with the American Boat and Yacht Council about implementing these changes, which include creating a closed engine cooling system, raising the hull to help with draining, placing the jet intake on the exterior to aid in flushing, and welding lifting strakes on pontoons closed.
While the council does not have the power to enforce these suggestions, it does represent a group of stakeholders that understand the incentive in slowing the movement of invasive species like zebra mussels. Boaters, and especially angling boaters, may drive the industry towards incorporating these modifications because of their interest in keeping river and lake ecosystems functioning. Regardless, it is comforting to know that private companies and individuals don’t have to wait on the government to save native waters.
Originally published in Outdoor News Minnesota.
Pictures from the Minnesota Aquatic Invasive Species Research Center