1. University of Minnesota Extension
Managing Aquatic Invasives: Curly-leaf Pondweed and Eurasian Water Milfoil
Barbara Liukkonen
University of Minnesota Extension
Waconia, April 1, 2008

2. How much do you know about Curly Leaf Pondweed?
Photo: B. Liukkonen
How much do you know about Curly Leaf Pondweed?
A lot
Some
Not Much
Nothing

3. How much do you know about Eurasian Water Milfoil?
Photo: Plant Conservation Alliance
How much do you know about Eurasian Water Milfoil?
A lot
Some
Not Much
Nothing

4. Key messages Ecology of aquatic vegetation
Opportunities for AIS invasion
Unique life history of CLPW
CLPW & EWM identification and look-alikes
Photo, Steve McComas, Blue Water Science

5. The Ecology of Aquatic Plants
Photo by Mark Hagley
The Ecology of Aquatic Plants

6. Why care about aquatic plants?
Food and habitat for:
Waterfowl
Mammals
Fish
Invertebrates
Algae
Fungi
Bacteria
People
Plants provide food and habitat for many different types of “critters” in the environment, and many of those “critters” are important to people, both for food and for viewing pleasure.
University of Wisconsin – Extension

7. Sediment and erosion control
Shield shoreline from erosive wave action
Stabilize bottom sediments
Help keep water clear

8. Spawning, nesting, feeding, and refuge sites
Mary Gartshore
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9. Less obvious reasons to care about aquatic plants
Photo, Mark Hagley
Less obvious reasons to care about aquatic plants
They play a critical role in the ecological functioning and nutrient cycling of most aquatic systems

10. Productivity
Diagrams by Cindy Hagley
Oligotrophic – low nutrients, low “productivity,” usually high clarity
Mesotrophic – moderate nutrients, moderate “productivity,” moderate clarity
Lake productivity, and the values and beauty we ascribe to the lake, are largely determined by the supply of nutrients the lake receives.
The lakes and bays where aquatic plants or algae can become dense and troublesome are usually nutrient-rich. They are also often relatively shallow.
Thus, if you live on a lake that receives a lot of nutrients from its watershed, either because of how the land surrounding the lake is managed or because of natural sources, and your lake or bay is relatively shallow; it is at risk of becoming dominated by either algal blooms or aquatic plants.
Eutrophic – high nutrients, high “productivity,” low clarity

11. Eutrophication Impacts Noxious, occasionally toxic algae
Too many or too few aquatic plants
Loss of clarity
Low dissolved oxygen
Loss of habitat
When we talk about eutrophication, we are talking about what can be a natural condition, but usually it is accelerated by human land use practices.
Surprisingly, eutrophication can be accompanied by an increase in aquatic plants or LOSS of an aquatic plant community.
Other unpleasant impacts accompany these changes.

12. Influence of excess nutrients
Algae-dominated systems
Blue-green algae blooms increasing – potentially toxic
Schwanz Lake, MN
Here is a good example of what nutrients can do to a lake. This is a scientific experiment where a lake was divided by a barrier and phosphorus was added to just one side. The top portion is clear, low productivity water, the natural state of the lake. The lower portion is clearly not a desirable condition.

13. Which would you prefer?
Photo, Rich Axler
Most of us, given a choice, prefer an aquatic plant dominated system.
Shallow, productive lakes or bays are often delicately balanced ecosystems.
Research has shown that the balance between aquatic plant dominance and algae dominance can shift very quickly, and once a lake shifts to an algae dominated state it is very difficult to return it to aquatic plants.
If given a choice, most people would prefer their cabin to be located on a lake with healthy aquatic plant populations rather than a lake where dense blooms of algae have turned the lake pea soup green and shaded out the plants.

14. How can disrupting the plant community lead to increased algae?
Nutrients no longer used by macrophytes are available for algae growth
Algae blooms reduce light for rooted vegetation
Cindy Hagley
Cindy Hagley
LIGHT:
Although aquatic plants can grow in much lower light conditions than plants on land (up to 95% less light), lack of light still limits their maximum depth.
Therefore:
A dense algal bloom can shade out aquatic plants.
In a lake or bay that is shallow enough for aquatic plants to occur throughout, dense aquatic plant growth can actually shade and limit algal growth.
NUTRIENTS:
Nutrients released from the die off of algae can fuel aquatic plant growth.
Die off of aquatic plants can cause algal blooms.
It can be a delicate balancing act.

15. A fine ecological balance
Disturbances disrupt the balance
Excessive nutrients
Mechanical harvester or boat damage
Herbicides
Grazing by invasive fish
Major storms eroding shorelines
Choices you make can drive your lake to “algal soup”
E. Burkett, UMES
What can make a lake shift from dominance by plants to dominance by algae?
Research has shown a clear relationship between increased nutrients and increased algae in the water, and, at first, increased plant growth.
But soon the plants disappear, leaving the system dominated by algae.
Research shows other factors can cause lakes to shift from aquatic plant to algal dominance, such as:
mechanical harvester or boat damage to plants,
herbicides,
pesticides,
or grazing on plants by exotic fish such as carp*.
In other words, choices you might make to control plants might drive the lake to a much less desirable state – algal soup!

16. Disturbance impacts just like on land
Photo, Steve McComas, Blue Water Science
Orchard Lake
How can disrupting the native plant community contribute to nuisance aquatic plant invasions?
When you clear a patch of woods or dig up ground for a garden, but don’t get it planted right away, what happens?
When we disturb the natural community on land OR in water, we create a perfect opportunity:
The plants that are best able to colonize disturbed sites are –
Fast-growing and able to colonize new areas rapidly
Can adapt to a wide range of conditions
Reproduce rapidly
And, most importantly, can out-compete the native plants that normally occur
That is why we end up with plants like dandelions (highly invasive) over-running our gardens and old fields.
In particular, “invasive” plants that have migrated here from far away have no or few natural enemies in the form of insects, diseases, etc. to hold their populations in check.

17. Plant communities
Now we’ll shift gears just a bit to familiarize you with typical aquatic plant communities in lakes.

18. Aquatic plant growth forms
Floating-leaf
Submergent
Emergent
The littoral zone is usually defined by the growth of rooted and floating aquatic plants, or macrophytes. The macrophyte community can also include large branched algae, such as Chara and Nitella. This community also includes many groups of attached algae (periphyton) that grow in close association with the higher plants, using them as a substrate for attachment (slimy rocks or plants are covered with periphyton).

19. Floating leaved plants
Near-shore unless sheltered
Can grow to 3-6 ft deep
Can grow in turbid water because leaves float
Rooted or floating roots
Water lilies
Watermeal (Wolffia)
Duckweed
The littoral zone is usually defined by the growth of rooted and floating aquatic plants, or macrophytes. The macrophyte community can also include large branched algae, such as Chara and Nitella. This community also includes many groups of attached algae (periphyton) that grow in close association with the higher plants, using them as a substrate for attachment (slimy rocks or plants are covered with periphyton).

20. Submerged Aquatics Weak-stemmed Survive below ice & waves
In clear water can grow 6-12 ft below surface
May have floating leaves
Rooted or floating roots.
The littoral zone is usually defined by the growth of rooted and floating aquatic plants, or macrophytes. The macrophyte community can also include large branched algae, such as Chara and Nitella. This community also includes many groups of attached algae (periphyton) that grow in close association with the higher plants, using them as a substrate for attachment (slimy rocks or plants are covered with periphyton).
Isoetes (quillwort)
Milfoil
CLPW

21. Emergent Roots below water surface Vegetative parts above water
cattails
Roots below water surface
Vegetative parts above water
Special respiratory systems to pass oxygen to roots
Tolerate fluctuating water levels
Dense stands can dampen wave action
reeds
The littoral zone is usually defined by the growth of rooted and floating aquatic plants, or macrophytes. The macrophyte community can also include large branched algae, such as Chara and Nitella. This community also includes many groups of attached algae (periphyton) that grow in close association with the higher plants, using them as a substrate for attachment (slimy rocks or plants are covered with periphyton).
bulrushes

22. Summary – Why is aquatic vegetation important ?
Photo: Mark Hagley
Summary – Why is aquatic vegetation important ?
Habitat for food organisms (insects, invertebrates)
Spawning, nesting, resting habitat for fish & wildlife
Prevent shoreline erosion
Filter nutrients
Stabilize bottom substrates
Add dissolved oxygen to water

23. How does curly leaf fit in?
Photo, Shannon Lotthammer, 2005, PLSLWD
Submerged plant
VERY well-adapted to disturbance
Messes up the natural ecological cycle

24. Curly Leaf Pondweed Non-native, “Exotic”
Photo, Brian Vlach, 2005, Three Rivers Park District
Curly Leaf Pondweed
Non-native, “Exotic”
Aquatic Invasive Species or AIS
Submergent aquatic plant
Potamogeton crispus
Similar to other pondweeds
Can be very invasive

25. Curly-leaf pondweed in 800+ sites
There are over 500 sites with curly-leaf pondweed in the state. In some lakes it causes significant problems. In other lakes it does not become abundant
According to the MN Lakes Assoc, 3000 DNR Surveys of Minnesota Lakes indicate 540 lakes with CLPW, and located in 80% of Counties

26. Distribution of CLPW in Minnesota
as of 2005

27. Habitat Deep water plant Colonizes water 1–2 feet deep
Photo, John Barten, 2005, Three Rivers Park District
Habitat
Deep water plant
Colonizes water 1–2 feet deep
Spreads to depths of 10 or more feet
Tolerates low light

28. Growth habitat Grows well in disturbed sites
Photo, Steve McComas, Blue Water Science
Grows well in disturbed sites
Can grow under algae or snow-covered ice
Strong roots allow growth in lakes or moderate streams

29. Photo: Brian Vlach, 2005, Three Rivers Park District
Curly-leaf Life Cycle
Its unique life cycle gives curly leaf a competitive advantage over many other aquatic plants

30. Life cycle Autumn/winter Spring Sprouts buds from turions
Remains alive during winter
Can grow under ice
Spring
Rapid growth while other plants continue dormancy
summer
spring
fall
Curly-leaf pondweed’s unique life cycle gives it competitive advantages over many native aquatic plants. As this diagram taken from Wehrmeiser and Stuckey’s 1992 article in the Michigan botanist shows, unlike most native plants, curly-leaf pondweed plants remain alive in the winter slowly growing even under thick ice and snow cover. Therefore, it is often the first plant to appear after ice-out.
winter
J.R. Wehrmeister and R.L. Stuckey Life History of Potamogeton crispus. Mich. Botanist. 31(1):3-16

31. Life cycle Spring/summer May form dense mats Flower spikes/seeds
Turions form in leaf axils
summer
spring
fall
In mid-summer, when most aquatic plants are growing, curly-leaf plants are dying back. Before they die, they form vegetative propagules called turions (hardened stem tips).
winter
J.R. Wehrmeister and R.L. Stuckey Life History of Potamogeton crispus. Mich. Botanist. 31(1):3-16

32. Life cycle Summer/fall Turions drop Disperse by water movement
Sink to bottom of lake
Lie dormant
Cycle begins again
summer
spring
fall
Turions lay dormant during the summer when native plants are growing, and most germinate in the fall when most native vegetation has died back.
Long-term management of curly-leaf will require the reduction or elimination of turions to interrupt the life cycle of curly-leaf pondweed. The MnDNR has been actively supporting research to improve current management approaches. We are particularly interested in management strategies which could interrupt turion production.
winter
J.R. Wehrmeister and R.L. Stuckey Life History of Potamogeton crispus. Mich. Botanist. 31(1):3-16

33. CLPW reproduces … Through turions Through rhizomes
Photo: Barb Liukkonen
Photo: Barb Liukkonen

34. Potamogeton species Species are difficult to identify
Several have oval floating leaves
Others have entire structure below water
In flower, plants have compact spikes with greenish to brownish flowers above water surface
Pondweeds grow densely to limit of light

35. Three kinds of pondweed Note the differences in appearance
Source: W. Hoagman, Great Lakes Wetlands. University of Michigan press

36. Curly Leaf Identification
Key point # 1
Leaves grow in an alternate pattern along the stem
Typical in many pondweeds

37. Curly Leaf Identification
Key point #2
Branching vein pattern
The only pondweed with branching vein pattern

38. Curly Leaf Identification
Key point #3
Serrated leaf margin
Only 1 other pondweed species has serrated margin

39. Curly Leaf Identification
Leaves are wavy and may be reddish in color, but this is not unique to curly leaf pondweed
Photo, Barb Liukkonen,

40. Look-alike plants Serrated leaf margin Branching vein pattern
Curly leaf pondweed
Potamogeton crispis
Richardson’s pondweed
Potamogeton richardsonii
Serrated leaf margin
Branching vein pattern
Leaves not clasping stem
Smooth leaf margin
Vein pattern parallel
Leaf clasps stem

41. CLPW Management Physical – drawdown
Biological – no known bio controls yet
Mechanical – harvesting
Chemical – timing and application critical

42. CLPW Control Opportunities
Control the turions, control the plant
No growback after 16 nodes
Treat before plant reaches 22 nodes

43. Factors that influence CLPW growth
sediment pH
organic matter
sediment density
sediment iron concentration
Research is looking at ways to manipulate growth factors

44. Eurasian Water Milfoil
Photo by RL Johnson, Cornell University
Eurasian Water Milfoil
Submersed aquatic native to Europe, Asia, N. Africa
First in US between 1880 & 1940s
In MN in 1987 – Minnetonka
Burandt Lake in 2003
Spreads through human activities and connected waters

45. EWM description Slender stems whorled by threadlike leaves
4-petaled/no petal flowers in the axils of the floral bracts
Fruits are four-jointed nut-like bodies
Reproduces through fragments & runners

46. USDA-NRCS PLANTS Database/ Britton, N. L. , and A. Brown. 1913
USDA-NRCS PLANTS Database/ Britton, N.L., and A. Brown An illustrated flora of the northern United States, Canada and the British Possessions. Vol. 2: 614.
USDA-NRCS PLANTS Database / USDA NRCS. Wetland flora: Field office illustrated guide to plant species. USDA Natural Resources Conservation Service.

47. EWM in MN 200 lakes, as of summer 2007 Thick mats at surface
Interferes with recreation
Takes advantage of disturbance

48. Look-alikes
Without flowers or fruits, difficult to tell EWN from Northern water milfoil
EWM pairs of leaflets per leaf
Northern milfoil pairs of leaflets
Coontail is often mistaken for milfoil, but does not have individual leaflets.

49. EWM Management Mechanical - harvesting Biological – weevil
Chemical – timing and application critical

50. Biological control Euhrychiopsis lecontei Native species Stem “miners”
21-30 day life cycle
Prefer EWM
Cycle with plant populations, fish predation

51. Managing CLPW & EWM Eradication unlikely
Photo, J. Barton, Three Rivers
Managing CLPW & EWM
Eradication unlikely
Management and control are key
Takes coordinated action, working together
Partnership – property owners, local resources, DNR
Photo, B. Rice, TNC

52. Bald Eagle Lake
Photo, Steve McComas, Blue Water Science
Recommended Reading:
A field Guide to identification of Minnesota Aquatic Plants, by M. Blickenderfer (2007)
Through the Looking Glass: A Field Guide to Aquatic Plants by Borman, S., Korth, R. & Tempte, J. (1997). Available from Wisconsin Lakes Partnership at (715)
Special thanks to:
Mary Blickenderfer, UM Extension Service
Eleanor Burkett, UM Extension Service
Wendy Crowell, MN Department of Natural Resources
Cynthia Hagley, MN Sea Grant Program

53. Photo, Brian Vlach, 2005, Three Rivers Park District
The information and drawings in this slide show are copyright by the Board of Regents of the University of Minnesota, 2008, or by the sources listed. If you want to reproduce or reuse them, please contact Barb Liukkonen, from the University of Minnesota Extension Service.

54. Key messages Think before disturbing a healthy aquatic plant community
Learn about your lake’s aquatic plant community and nutrient dynamics
Develop a management plan
Your day-to-day choices and practices can cause problems AND be solutions