Eyes on the Lake

Eyes on the Lake

This feature will help us all with learning what plants are native and healthy for our lakes vs. the invasive plants. We hope you find this information helpful. Thanks for helping to keep our waters clean.

Zebra Mussels

Keys to identify:

  • Stripes are generally in zigzag patterns
  • Pattern is variable; some may lack striping altogether and can be solid tan or brown
  • Have a flat edge and won’t topple over when set on its edge
  • Shells form straight light when closed
  • Range from 1/8 of an inch to 2 inches; adults are typically fingernail sized.

Looks similar to:

  • Other invasive invertebrates: Quagga mussels, Asian clams & Chinese mystery snails.
  • Native invertebrates: native snails and native mussels.


Where to look:

  • Often found attached to submerged objects (such as boats and docks, as well as plants and rocks)
  • Newly settled mussels are usually in shallow areas; adults are common in depths of 10-20 feet.

Zebra Mussel Impact:

  • Encrusts equipment, such as boat motors and hulls, which reduces performance and efficiency, and is costly to clean and repair
  • Swimmers and pets can cut their feet on zebra mussels attached to rocks, docks, swim rafts and ladders
  • Creates a costly problem for power plants, cities and residents when they clog water intakes.
  • Filters tiny food particles out of the water, which can reduce available food for larval fish and other animals, and can increase aquatic plant growth as a result of increased water clarity.
  • Attaches to and kill native mussels.

What we should know:

  • A single zebra mussel can filter one quart of water per day while feeding primarily on algae.
  • A female can produce 100,000 to 500,000 eggs per year. Fertilized eggs develop into microscopic, free-living larvae, called "veligers," that form shells. After two to three weeks, the veligers settle and attach to a firm surface using tiny fibers called byssal threads. Beds of zebra mussels can reach tens-of-thousands within a single square yard.
  • Microscopic larvae (veligers) can survive in water contained in bait buckets, live wells, bilge areas, ballast tanks, motors and other water containing devices.
  • Zebra mussels are unintentionally spread through the movement of water-related equipment, attaching to boats, docks, swim rafts and boat lifts, as well as aquatic plants.
  • Adult mussels can survive out of water – less than 5 days in dry conditions, but up to 21 days in very wet conditions (such as, inside dock/lift pipes).
  • It is a prohibited invasive species and it is unlawful (a misdemeanor) to possess, import, purchase, transport, or introduce this species except under a permit for disposal, control, research, or education.


How to prevent zebra mussels:

Clean watercraft of all aquatic plants and prohibited invasive species.

Drain all water, including live wells and bait water. Remove boat drain plugs; keep them out during transport.

Dispose of unwanted bait in the trash.

Dry docks, lifts, swim rafts and other equipment for at least 21 days before placing equipment into another water body.

Credits:

AIS Identification Guide: A Minnesota Handbook, www.maisrcumn.edu

MN DNR website: https://www.dnr.state.mn.us/invasives/aquaticanimals/zebramussel/index.html

Eurasian Milfoil

Is It Eurasian Milfoil or Northern Milfoil?

Eurasian watermilfoil looks similar to many native, beneficial watermilfoils found in Minnesota lakes and rivers. Its common native look-alike is northern watermilfoil. It’s spread primarily through the movement of water-related equipment. Plant fragments can get tangled on boats, trailers, motors, anchors and other water-related equipment. All it takes is a single plant fragment to start a new population. It is a prohibited invasive species in Minnesota, which means it is unlawful (a misdemeanor) to possess, import, purchase, transport or introduce these species except under a permit for disposal, control, research or education.

Eurasian watermilfoil impacts:

  • Dense mats at the water’s surface inhibit water recreationists.
  • Overtakes habitat and outcompetes native aquatic plants, potentially lowering diversity.
  • Provides unsuitable shelter, food, and nesting habitat for native animals.

Keys to Identifying the 2 Types of Milfoil

EURASIAN NORTHERN

  • Featherly looking with 4 leaves per whorl
  • Leaves have central axis with 12-20 leaflet pairs
  • Can grow up to 10 feet long
  • Produces pink & white flowers on spike above surface
  • Flowers 2x/year; usually mid-June & late-July
  • Leaves become limp when taken out of water
  • Grows best in 3-15 feet
  • 4 leaves per whorl
  • Leaves have central axis
  • Each leaf has 4-11 leaflet pairs
  • Forms winter bud in late fall and winter
  • Leaves are rigid when taken out of water
  • Grows underwater in depths of up to 20 feet

Credits:

AIS Identification Guide: A Minnesota Handbook, www.maisrcumn.edu

MN DNR website: https://www.dnr.state.mn.us/invasives/aquaticplants/milfoil/index.html

Starry Stonewort

Keys to Identify:

  • Bushy, bright green macro-algae. It produces a characteristic star-shaped bulbil.
  • Small, white star-shaped bulbils form on clear threads at base of plant (asexual reproductive structure). May be found above or below the sediment surface – bulbils are the size of a grain of rice.
  • Small, orange spheres may be visible near the tips of the structure (male reproductive structures called antheridia).
  • Long, smooth branchlets are attached in whorls of 5-8 and branch asymmetrically at tips.
  • Stems are smooth.
  • Branchlets typically form several inches long – longer than Chara or Nitella (native aquatic grasses).
  • Can fill water column and form surface mats.

Looks similar to the follow native species:

  • Other native stoneworts and muskgrasses that are beneficial grass-like algae, and are found in Minnesota lakes and rivers.
  • Look-alike natives: Chara; Nitella; Sago pondweed; Water stargrass.

Where to look:

  • In shallow, still water and near accesses.



Starry Stonewort Impacts:

  • Dense mats at the water’s surface inhibit waterways and clog boat propellers, as well as water recreation.
  • Overtakes habitat and out-competes native aquatic plants, potentially lowering diversity.
  • Provides unsuitable shelter, food, and nesting habitat for native fish and wildlife.
  • No known herbicides will kill it. Mechanical harvesting is used to remove it and stop it from spreading.

What we should know:

  • Believed to be spread from one body of water to another by the unintentional transfer of bulbils, the star-like structures produced by the plant. These fragments are most likely attached to trailered boats, personal watercraft, docks, boat lifts, anchors or any other water-related equipment that was not properly cleaned.
  • First discovered in Minnesota in August 2015 on Lake Koronis near Paynesville in Stearns County.
  • 13 Minnesota counties have infested lakes, including Cass and Itasca (Lake WInnibigoshish, 2016) and Beltrami County (Lake Beltrami, 2019; Wolf, 2018; Upper Red Lake, 2016; Cass, 2016)

How to prevent starry stonewort:

  • Clean watercraft of all aquatic plants and prohibited invasive species.
  • Drain all water, including livewells and bait water. Remove boat drain plugs; keep them out during transport.
  • Dispose of unwanted bait in the trash.
  • Dry docks, lifts, swim rafts and other equipment for at least 21 days before placing equipment into another water body.

Credits:

AIS Identification Guide: A Minnesota Handbook, www.maisrcumn.edu.

MN DNR website: https://www.dnr.state.mn.us/invasives/aquaticanimals/zebramussel/index.html.

MN DNR infested waters: https://www.dnr.state.mn.us/invasives/ais/infested.html.