CLRR Projects

1. Half Moon Lake rehabilitation


 Half Moon Lake, a shallow oxbow of the Chippewa River located in Eau Claire, Wisconsin, is an important recreational resource for swimming, fishing, and boating and provides critical aquatic habitat for waterfowl, song birds, fish, and native submersed and emergent vegetation. In recent decades, the lake has exhibited dense invasive curly-leaf pondweed growth that covers nearly the entire lake, recent invasion by Eurasian watermilfoil, and severe cyanobacterial blooms. The lake was classified as hypereutrophic (trophic state index > 70). Mean summer total phosphorus concentration can exceed 100 μg/L, resulting in poor water transparency and low light penetration which limits native submersed macrophyte growth. Anoxia develops in the bottom water of the lake throughout much of the summer, which exacerbates phosphorus flux from sediments and greatly increases the potential for algal uptake and growth.


1. Half Moon Lake rehabilitation  (continued)

The overall management goal for Half Moon Lake is to improve water clarity and light penetration to promote the re-establishment of healthy native aquatic plant communities. Strategies to accomplish this goal are twofold: 1) reduce infestations of canopy-forming curly-leaf pondweed and Eurasian watermilfoil and 2) control internal phosphorus loading from sediment to limit algal productivity and improve light condition for native plant growth. First, motor boat activity has been restricted on the lake to reduce phosphorus resuspension and internal loading. Second, annual early spring herbicide treatments have been conducted during the years 2009-2013 to selectively target curly-leaf pondweed with minimal impact to native plants. Similar selective control of Eurasian watermilfoil was also accomplished in 2009. Finally, phosphorus release from sediments was managed in June, 2011, via application of buffered alum-aluminate to drive algal productivity toward phosphorus-limited growth and increase light penetration for native macrophyte communities.

To assess and evaluate native macrophyte community response to these management measures, extensive limnological monitoring has been conducted by faculty and students at the Center for Limnological Research and Rehabilitation. Macrophyte biomass is monitored in June and August using point-intercept sampling techniques to evaluate the effectiveness of the herbicide treatments in controlling curly-leaf pondweed and Eurasian watermilfoil and to quantify native macrophyte community response to changes in water quality and management of the targeted invasive species. These surveys were also part of an early detection monitoring program that found a pioneer population of Eurasian watermilfoil in the southwestern embayment of the lake. Germinated turion frequency of occurrence is quantified in early April of each year to determine areas in the lake that need further herbicide treatment and to evaluate the viable turion seedbank in the sediment. In addition, in situ (i.e., temperature, dissolved oxygen, pH, conductivity) measurements, light penetration, phosphorus, chlorophyll, and algal abundance are monitored at six stations in the lake to assess improvement in underwater light habitat for comparison with the native macrophyte community response. 

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 2. Phosphorus budget and management strategies for Cedar Lake, Wisconsin

Comprehensive limnological investigations are being conducted on Cedar Lake and its watershed in order to identify important phosphorus sources to the lake for management. This relatively large lake (453 ha) exhibits massive blooms of potentially toxin-forming cyanobacteria as a result of phosphorus recycling from sediment stored in the lake and mixing into the water column during fall turnover. Since cyanobacterial growth is generally limited by phosphorus availability in Cedar Lake, this phosphorus recycling pathway needs to be managed in order to reduce bloom frequency. We found that sediment phosphorus flux can account for up to 90% of the phosphorus sources to the lake during the growing season and are currently developing management scenarios to inactivate sediment phosphorus via aluminum sulfate (alum) application. Alum has been successfully used for decades as a management tool to bind mobile phosphorus in lake sediment. It is applied as a liquid slurry from a boat and quickly reacts to form aluminum hydroxide polymers that settle as a milky white floc to the sediment surface. These polymers attract and chemically bind phosphate in the sediment and remove it from further recycling. Control of this internal source of phosphorus recycling is expected to reduce phosphorus concentrations by up to 50% and the frequency of nuisance cyanobacterial blooms by up to 70%. 



3. Tributary loading and phosphorus budget analysis for Lake Desair, Wisconsin


4. Sediment characteristics and diffusive phosphorus fluxes in Lac Courte Oreilles, Wisconsin

Lac Courte Oreilles is a relatively large oligotrophic lake located in Sawyer County, Wisconsin, that is experiencing growing watershed development and agricultural pressure. A two-story fishery (i.e., both cold and warm water fisheries), it is considered one of Wisconsin’s designated Outstanding Resource Waters. Concerns over the potential for future degradation of this pristine lake has led to the development of a TMDL (Total Maximum Daily Load) for the lake. Our studies have focused on sediment chemistry and potential internal phosphorus loading from sediments in the various shallow embayments and three of the deep basins in the lake. Intact cores were collected during the summer of 2012 and incubated under control temperature and oxidation-reduction conditions for determination of phosphorus release rates from the sediment. Results will be used to better understand the role of sediments in the phosphorus budget of the lake.