Column: The battle of the invasives

val0306hong eurasianmilfoil-06WebAsian carp and zebra mussels have been hogging headlines in recent years, but are aquatic invasive species really a new problem in Minnesota?
According to the Minnesota Department of Natural Resources curly-leaf pondweed was first reported in our state in 1910, more than 100 years ago. No one knows exactly how it got here, but ecologists think the plant probably arrived with a shipment of common carp, another non-native that Minnesotans had been shipping in intentionally since the 1880s as a game fish. Today, both curly-leaf and carp are found in abundance throughout the state, with curly-leaf growing in 750 Minnesota lakes and common carp known to live in hundreds of lakes in the southern two-thirds of Minnesota.
What has changed over the past 10-20 years is that Minnesotans have become increasingly mobile, heightening the risk that people might unknowingly transport aquatic species to new lakes and rivers that aren’t yet infested, and also that dozens more non-native plants, animals and diseases from around the world have added their names to the list of potential invaders.
Byron Karns, a ranger with the National Park Service, refers to invasive species as “biological pollutants,” saying, “They pollute our local lakes and rivers, but, instead of breaking down over time like other pollutants, they reproduce and spread to new lakes as well.”
Each invasive species carries with it a unique set of problems. Curly-leaf begins growing early in the spring under the ice, allowing it to out-compete native aquatic plants. It forms dense clumps during the early summer that snarl boat propellers and then dies back in mid-summer. Mats of dead plants wash up along the shoreline, and the dead curly-leaf releases phosphorus into the water, which contributes to excess algae growth at the end of the summer.
Carp root around on the bottoms of lakes, uprooting native vegetation and churning up muck at the bottom of shallow lakes, which also releases phosphorus and makes the water cloudy.
On Saturday, March 15, the Carnelian-Marine-St. Croix Watershed District, Comfort Lake-Forest Lake Watershed District and Chisago Lakes Improvement District will team up to offer a free workshop for local lake and river users interested in learning more about aquatic invasive species in the area. During the workshop, the districts will talk about which invasives have been found in which lakes in northern Washington and southern Chisago Counties, in addition to sharing the latest DNR survey data collected during boat launch inspections last year. Guest speaker Steve McComas, “the Lake Detective,” will talk about his research on the effectiveness of various strategies for managing curly-leaf and Eurasian water-milfoil in Forest Lake and other lakes, and I will share a story of success from Lake Minnetonka, where retrofits and educational signs at a popular boat launch have dramatically increased the percentage of people following clean and drain regulations.
In addition to the presentations, workshop participants will hone their identification skills as they practice differentiating between common native and invasive plant and animal species and will also have time at the end to network with other local residents and lakeshore property owners.
Last year’s aquatic invasive species workshop drew more than 70 attendees, and we expect this year’s workshop to be popular as well.
The Aquatic Invasive Species Workshop will take place 9-11 a.m. Saturday, March 15, at the Scandia Community Center, 14727 209th St. N. in Scandia. Register on-line at

Angie Hong is an educator for East Metro Water. Contact her at 651-275-1136 ext. 35 or