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

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

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

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

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

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

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

Spawning, nesting, feeding, and refuge sites Mary Gartshore www.snowgoosegallery.com/. ../bushwacked2.gif

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

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

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.

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.

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.

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.

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!

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.

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

Aquatic plant growth forms http://aquat1.ifas.ufl.edu/\ 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).

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).

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

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

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

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

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

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

Distribution of CLPW in Minnesota as of 2005

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

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

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

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. 1992. Life History of Potamogeton crispus. Mich. Botanist. 31(1):3-16

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. 1992. Life History of Potamogeton crispus. Mich. Botanist. 31(1):3-16

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. 1992. Life History of Potamogeton crispus. Mich. Botanist. 31(1):3-16

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

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

Three kinds of pondweed Note the differences in appearance Source: W. Hoagman, 1998. Great Lakes Wetlands. University of Michigan press

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

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

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

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

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

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

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

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

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

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

USDA-NRCS PLANTS Database/ Britton, N. L. , and A. Brown. 1913 USDA-NRCS PLANTS Database/ Britton, N.L., and A. Brown. 1913. 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.

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

Look-alikes Without flowers or fruits, difficult to tell EWN from Northern water milfoil EWM - 9-21 pairs of leaflets per leaf Northern milfoil - 7-11 pairs of leaflets Coontail is often mistaken for milfoil, but does not have individual leaflets.

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

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

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

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) 346-2116 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

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, liukk001@umn.edu from the University of Minnesota Extension Service.

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