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Outdoors
Outdoors
By Vicki Browne
Iron County Lakes and Streams Partnership
CRYSTAL FALLS — Jen Ricker-Feak, District Manager for the Iron-Baraga Conservation District, loves the lakes of Iron County.
“The lakes are beautiful,” she said. “They’re in wonderful shape with lots of native biodiversity, and the majority are still very natural.”
One of Ricker-Feak’s areas of expertise is invasive species. These are the species that arrive uninvited and take over, crowding out native species and destroying natural habitats.
According to Ricker-Feak, the flow of water moves aquatic invasive species very easily.
“Invasives drift from lake to lake and into connected streams or wetlands, or are carried there on watercraft and equipment,” she explained.
Some of the invasive species she talked about are already here in some Iron County lakes. Those include purple loosestrife, curly leaf pondweed and Eurasian watermilfoil.
Purple Loosestrife
Although purple loosestrife looks pretty, it poses a serious threat. It is commonly held that purple loosestrife came to the U.S. in the mid-1800s in the ballast containers of ships and by people seeking a cure for dysentery. Sadly, purple loosestrife seeds are still sold online, and people purchase them unknowing the damage the plants can cause.
Purple loosestrife has a square, woody stem. It grows from 4–10 feet tall and has magenta flowers with 5–7 petals for most of the summer. It grows in wetlands, along the shoreline, and can occasionally be found on partially submerged logs, or vegetative mats floating in the lake.
According to the Michigan Invasive Species website, “Given the right conditions, purple loosestrife can rapidly establish and replace native vegetation. This can lead to a reduction in plant diversity, which reduces habitat value to wildlife.”
Purple loosestrife outcompetes native plants because of its fast reproduction rates. Birds, fish and other small mammals cannot penetrate the dense canopies it creates in wetlands.
Curly Leaf Pondweed
Curly leaf pondweed, or sometimes just curly pondweed, came to the Great Lakes in the 1880s, most likely when common carp were introduced as a game fish. It is a rooted, submersed plant.
According to the Minnesota Department of Natural Resources, “Wavy, lasagna-like leaves grow approximately a half-inch wide and 2-3 inches long. Leaves have an obvious mid-vein, “toothed” or serrated edges and blunt tips.” This is important to note since there are many types of native pondweeds that look similar.
Curly leaf pondweed grows from the shoreline to about 15-foot water depths and can grow to be 15 feet long. This invasive species creates dense mats at the water’s surface. Like all invasives, it outcompetes native plants and lowers biodiversity.
Curly leaf pondweed gets an early start since it grows through the spring and dies off mid-summer. The dead plant matter is a source of excess nutrients, which can boost algae growth. As it decomposes it causes a decrease in dissolved oxygen which is harmful to fish.
Eurasian Watermilfoil
Eurasian watermilfoil (EWM) is the aquatic invasive species with which most people are familiar. According to Ricker-Feak, it is present in approximately 15% of Iron County lakes that are over five acres in size. The costs to contain and control EWM once it is established in a lake make it a top priority for early detection and eradication.
EWM is very resilient. It can overwinter in frozen lakes and survive in overheated summer bays. Like curly pondweed, EWM gets the early jump in spring, as soon as ice is off the lakes. It also grows prolifically and can reproduce from any part of the plant. When it dies, it leaves behind a lot of biomass, which adds to the nutrient load in a lake.
The Minnesota DNR explains that EWM can be distinguished from native milfoil by the “leaves which are feather-like, with four leaves arranged in a whorl (radiating out from a single point) around the stem. Space between whorls along the stem can be a half-inch or greater. Each leaf has a central axis with 12–21 leaflet pairs. Leaflets are limp when the plant is removed from the water.”
According to the Michigan Invasive Species website, “Eurasian watermilfoil forms large mats of floating vegetation that will shade out native aquatic plants and impede recreational activities. This species is not a valuable food source of waterfowl and may interfere with fish predation. Thick vegetation like this can also clog residential or industrial water intakes.”
Recently, hybridized milfoil has been found in area waters. The hybridized milfoil combines the most successful traits of Eurasian watermilfoil with that of the native milfoil, leading to a more robust plant that is harder to identify and also more resistant to herbicides that are often used to control the plant. Hybridized milfoil establishment often leads to increased herbicide usage.
In general, aquatic invasive species are the bullies of the plant world. They use resources needed by native species and upset the balance created by a biologically diverse habitat. Some are attractive, like purple loosestrife. Some are dense and ugly, like Eurasian watermilfoil.
Ricker-Feak notes that “shallower lakes are at greater risk because an invasive species can take over easier since the littoral zone” — or the marshy perimeter along the banks of waterways — “is larger.”
The littoral zone of a lake is the area from the shoreline to the farthest point where sunlight can reach the sediment at the bottom. This is the place where an invasive species can do the most damage and readily multiply.
“Learn about invasive species and the best practices to disinfect your equipment,” Ricker-Feak advised. “Know what a plant is before you move it.”
To learn more about the Lakes and Streams Partnership, visit iclakesandstreamspartnership.com or find the group on its Facebook Page. More information on the Iron-Baraga Conservation District is available at ironbaragacd.org.