What costs the U.S. economy $1 billion every year, clogs water intakes, decreases property values and ruins water-related equipment?
Zebra mussels, which have a huge negative impact on the environment and the economy. And they continue to spread.
About 8% of Minnesota’s more than 11,000 lakes are on the infested waters list which includes several aquatic invasive species (AIS). Less than 3% of these lakes are listed as infested with zebra mussels. As of October 2019, the DNR confirmed zebra mussels in 214 lakes and wetlands. It has listed 194 bodies of water as infested with zebra mussels because they are closely connected to a waterway where zebra mussels have been found. In Aitkin County, zebra mussels have been confirmed in Mille Lacs Lake, Big Pine Lake, Little Pine Lake, Round Lake, Farm Island Lake and in a portion of the Mississippi River.
Zebra mussels are a prohibited invasive species in Minnesota, and residents of the state are paying attention. Statewide compliance with AIS laws was 95% last year, and 99% in Aitkin County.
The low percentage of infestation in the state means, with the help of lake users, the DNR and partners like Minnesota counties, people have done a good job at limiting the spread of aquatic invasive species, said Tim Plude, invasive species specialist with the DNR.
WHAT ARE THEY?
They are small freshwater mussels. Adults range from 1/2 up to nearly 2 inches long with highly variable dark and light stripes; or are solid brown or yellow.
The mussel’s reproductive cycle is one key to its rapid spread and high abundance. Egg production starts when water temperature warms to about 54 degrees F. A fully mature female mussel may produce several hundred thousand eggs per season.
Eggs are fertilized outside the mussel’s body and within a few days develop into free-swimming larvae called veligers. Nearly invisible to unaided eye, veligers remain suspended in the water for three to four weeks, drifting with the currents. If they don’t settle onto firm objects, they die, and in fact, most do. Those that find a hard surface quickly attach themselves and transform into the typical, D-shape, double-shelled mussel.
Zebra mussels have been spreading to western and central European waterways for nearly 200 years. By the 1830s, these mussels covered much of Europe and Britain. Introduction of zebra mussels into the Great Lakes probably occurred in 1985 or 1986 and continued to spread to other bodies of water.
WHY ARE THEY HARMFUL?
Feeding by zebra mussels can remove so much microscopic plants and animals from the base of the food web that they can starve native fish and wildlife in lakes and rivers. As they spread, zebra mussels threaten the extinction of at least 30 freshwater mussels. Losses of crayfish and snails have been implicated by zebra mussel colonization.
Scientists have said that zebra mussels can cause an increase in toxic, blue-green algae, which produces a poison that causes liver damage when ingested by humans and wildlife. Since 1998, induced algae blooms have been known to trigger botulism type E outbreaks that have killed tens of thousands of loons and other waterfowl.
Recreational users of the waters have been impacted as well. There have been reports of boat engines overheating because cooling water inlets are clogged by zebra mussels.
Costs to manage, control and monitor for zebra mussels and their cousin, the quagga mussel, in the U.S. are more than $1 billion per year. They have especially affected water intake structures.
Controlling zebra mussel spread is not a lost cause, according to Plude.
“We can limit the spread with the help of everyone who uses lakes and rivers,” he explained. “Awareness of invasive species and everyone taking the proper prevention steps will limit the spread of zebra mussels.”
EVERYONE CAN HELP
He said public awareness is high and is reflected by the percentage of people obeying the laws.
“The public has many ways of learning about AIS laws,” said Plude, “through signs at boat landings, water inspections, boat registration, websites, news, talking to neighbors and participating in workshops and volunteer events. The DNR partners with UMN-Extension to put on AIS ID workshops, native and invasive plant ID workshops, as well as volunteer events like Starry Trek.”
Plude said there is always more that can be done to educate water users.
“One thing I have noticed over my career is that aquatic invasive species are being incorporated into school curriculum starting in grade school and this is great,” he said. “I have heard from parents that they learned some AIS facts from their children.
“Knowing the laws, understanding the impacts of AIS and knowing why these laws are in place are crucial pieces of information to help limit the spread of AIS,” Plude concluded.
“Water users should be aware that they can slow or stop all of the AIS threats by following the procedures we have consistently taught for five years or so,” noted Steve Hughes, district manager of the Aitkin County Soil and Water Conservation District. “The bait water, and dock/boatlift bounties are above and beyond the basic boat and trailer cleaning but will significantly reduce the risks.”
As always, stopping the spread of invasive species to other lakes and rivers, protects habitat for native species such as sunfish and crappies. Overall lake and river health is better without invasive species. Healthy lakes and rivers benefit fish, wildlife and people. Remember, “Clean, Drain, Dry and Dispose.”