Curly-leaf Pondweed Management Study on Gleason Lake
The six-year study wrapped up in 2012. Read the results below. "The overall water quality improved: increase in water transparency, and reductions of total phosphorus and chlorophyll A. Gleason Lake met the state's water quality standards for clarity, phosphorus and cllorophyll A, the first time it has met all three metrics since the study began.
The six-year Gleason Lake aquatic vegetation management project wrapped up in 2012. The objectives of the project were to determine if (1) herbicide treatments with "Aquathol K" can control and manage curlyleaf pondweed, and (2) herbicide treatments are a viable long-term solution for Gleason Lake.
There was a considerable reduction in the amount of curlyleaf pondweed present from 2007 through 2012. The density of the invasive plant dropped from 817 stems/m² in 2007 to 21 stems/m² in 2011, with a slight increase in 2012. These results suggest that the annual herbicide treatments were efective in reducing the plant.
With the reduction of the curlyleaf, vegetation surveys showed the enhanced growth of native vegetation. The overall water quality improved: increase in water transparency, and reductions of total phosphorus and chlorophyll A. In 2012, the State’s water quality standards for Gleason Lake were met for all three, clarity, phosphorus, and chlorophyll A for the first time during the 6 year project. These results can lead us to believe that herbicide treatments are a viable long-term solution for Gleason Lake.
Though the outcomes of the study appear positive, there may be other factors that did contribute to the overall condition of Gleason Lake. For example, the Gleason Lake’s north stormwater pond was expanded in 2008, which was estimated to reduce phophorus by as much as 35 percent.
GLIA is working with the MNDNR to update their vegetation management plan for Gleason Lake for the continuation of control and management of curlyleaf pondweed and coontail. MCWD staff will continue monitoring the lake’s water quality annually.
Gleason Lake is a valuable recreational resource used by residents who live on the lake, as well as the general public. Although Gleason Lake has no public boat landing, the lake is accessible to the general public through Luce Line trail in Plymouth. There are wheelchair-accessible fishing docks near the newly renovated Luce Line trail bridge. The Gleason Lake area is used for hiking, bike riding, and horseback riding. The lake is also a valuable resource for fishing and water skiing during the summer, as well as ice fishing and ice skating during winter.
Curly-leaf pondweed is an exotic species that competes with other native plants and is suspected by most to be a significant contributor to high phosphorus levels in lakes. The die-off (senescence) of curly-leaf pondweed starts at the end of June or early July, after the completion of turion (winter bud) production. The senescence of curly-leaf pondweed releases phosphorus, which causes algae bloom and poor water quality.
The watershed area of Gleason Lake is almost entirely (95%) in the city of Plymouth. The remainder is located in the cities of Wayzata, Orono, and Minnetonka. The water of Gleason Lake is almost entirely littoral (close to the shore), is less than 15 feet deep, and has extensive aquatic vegetation including coontail, curly-leaf pondweed, and eurasian water milfoil. Curley-leaf pondweed was detected at one-third of the stations sampled during an aquatic vegetation survey in 2002. The GLIA has been working on controlling another invasive plant, Eurasian watermilfoil, and added control of Curlyleaf pondweed should further help to improve water clarity and reduce algae blooms.
Gleason Lake has consistently received C's and D's in the MCWD's annual water quality grades. The mean total phosphorus concentration for summer 2005 was approximately 108 micrograms per liter, which is well above the MCWD’s interim goal of 80 micrograms per liter and the state’s proposed standard of 60 micrograms per liter. Phosphorus reductions are necessary to achieve these goals.
The MCWD is proactively addressing AIS issues in the Gleason Lake watershed by reducing the amount of nutrients that flow into the lake. GLIA has completed several other projects to reduce external nutrient loads and improve the water quality in Gleason Lake.
The five years of treatment have been successful in controlling and reducing the curly-leaf pondweed stem density in the Gleason Lake.
|Treatment Year||Curly-leaf pondweed density before treatment (stems/m2)||Curly-leaf pondweed density after treatment (stems/m2)|