a photo of eurasian watermilfoil in Lake Leelanau

Lake Leelanau Eurasian Watermilfoil Update

The Lake Leelanau Lake Association’s (LLLA) Eurasian Watermilfoil (EWM) team has been busy this summer tackling the threat of this dangerous aquatic invasive plant—particularly EWM—in Lake Leelanau. This summer is one of the most crucial seasons in our fight against EWM. The team has amplified our efforts, techniques, partnerships, and documentation to make a serious impact on EWM in Lake Leelanau. We are excited to share the progress our Crew is making this summer and how and why our efforts are successful.

Pre-season Preparations

The EWM team has expanded this year. Members include: 

  • Brian Price, Lake Biologist 
  • Ron Reimink, EWM Project Manager
  • Annalise Povolo, Director of Administration and Programs and SCUBA Team Leader 
  • Dan Mays, Inland Policy Biologist, and his colleagues from the Grand Traverse Band of Ottawa and Chippewa Indians

New to the EWM crew this year are partners from Grand Valley State University (GVSU). Professor Dr. Mark Luttenton and a Master’s degree candidate, Anna Briem, have joined us. The partnership with GVSU allows the Crew access to Annis Water Resources Institute’s resources. These resources help us to improve our scientific research and documentation of the impacts and effectiveness of our biodegradable burlap barriers used to kill EWM.

In addition, we have increased our collaboration with Dennis Wiand of Zero Gravity Aerials to utilize his advanced drone technology to improve our methods and documentation of EWM. And the cherry on top is two new contracted SCUBA divers, Catherine Dunn and Austin O’Connor, joined by three newly SCUBA certified divers from GTB to help with our underwater work.

With the newly assembled team, the crew began the season by amping up our efforts to document the large infestations of EWM in Lake Leelanau. We started by using drone technology to map out the infestations in the lake and accurately determine the size of the infestations. Then, we will use the findings to cover the areas with biodegradable burlap barriers.

We then set out to document:

  • The plant community in the infestation to ensure we were not covering a large number of native plants,
  • Macroinvertebrates (aquatic bugs, shells, crayfish, etc.), 
  • Physical and chemical conditions (nutrient concentrations within and outside treatment areas), and
  • The presence and response of fish on the barriers.

Once complete, we were ready to start covering these areas with our biodegradable burlap barriers to reduce the light penetration to EWM. Reducing the light penetration will ultimately kill the plant and protect our lake.

female GVSU graduate student labeling bags to collect plant and invertebrate samples in Lake Leelanau
GVSU graduate student Anna Briem labeling bags to collect plant and invertebrate samples.

Biodegradable Burlap Barrier Deployment

Once documentation was complete, we began setting some of the largest barriers the crew—or possibly anyone—has ever set before. We added extensions to our work pontoon boat to assist with setting barriers. We are setting barriers up to 40 feet wide off the side of the boat, with the largest reaching 500 feet in length. Some of these have even been overlapped to create barriers of 900 feet in length.

To prepare and set these giant barriers, the crew must lay the entire length of burlap on the road before loading on the boat. While laid out,  the members of the EWM team connect lengths of iron rebar along the barrier ends and in middle sections to keep the burlap stretched out and weighed down to the bottom of the lake. Then comes the grueling task of manually pulling the heavy and long burlap onto the boat to be ready to cover the EWM.

the eurasian watermilfoil crew lays out a biodegradable burlap barrier
The EWM crew lays out a 40-foot wide by 500-foot long burlap barrier (left) and then piled onto the work boat for deployment (right).

With the lessons learned over three summers of setting large burlap barriers in Lake Leelanau, the EWM team is deploying barriers in more advanced ways. The new techniques include overlapping sections of the barrier to custom-fit EWM infestations (since they are not all shaped like rectangles), and patching up edges that stick out with smaller “micro-barriers.”

A male eurasian watermilfoil crew member adjusts section of burlap barrier placed in Lake Leelanau
EWM Project Manager, Ron Reimink, adjusting a section of burlap before overlapping it with another.

Continued Maintenance and Documentation

As the EWM crew completes setting the barriers on the large, dense infestations of EWM, the dive crew is now busy with continued maintenance of all barrier location sites. Maintenance is crucial as any small fragments of EWM could settle on top of the barriers and regrow in those treated areas. 

One of the most positive findings of this season has been the discovery of native plants growing through the burlap. This shows that the native seed bank covered by the burlap can still produce plants that will grow through the burlap as it degrades — this is a great sign of our efforts, as EWM has not yet been able to flower in Lake Leelanau and produce a bank of seeds below the sediment.

As long as our crew can keep up with picking any fragmented EWM off of these sites, our native plant community can have the chance to take back its home. Our team, in collaboration with GVSU, is also investigating ways in which we can help those native plants speed up that process. In addition, the dive team is also working on documenting the same parameters on these barrier sites; this will help us compare the impacts before and after barriers have been put on an infestation of EWM.

Moving Forward

The EWM crew is very encouraged by the momentum we are gaining in our fight against EWM. But, as you can see, we have our work cut out for us. We are incredibly grateful for our partnership with the GTB and collaboration with GVSU. We also want to thank Zero Gravity Aerials for their contributions to morphing the Aquatic Invasive Species Program into the well-oiled machine it is now. Without all of the EWM Crew’s hard work, Lake Leelanau could quite possibly have already lost the battle against Eurasian watermilfoil.

If you, or anyone you know, would like to lend our EWM crew a hand by driving our dive boat and keeping our divers safe in the water, please contact Annalise at [email protected]. To learn more about EWM and our past work, please visit our Invasive Species page.

a male volunteer drives two SCUBA divers on a boat to infested area in lake leelanau
Volunteer Dan Harkness driving our divers, Austin O'Connor and Catherine Dunn, to their work site for the day.
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