Plan

In 2007, in partnership with Gleason Lake Improvement Association (GLIA), the Minnehaha Creek Watershed District (MCWD) began a lake vegetation study to assess the extent and removal of curly-leaf pondweed over a five-year period (2007-2011). During the first three years of study (2007-2009), the whole lake was treated with Endothall (an aquatic herbicide). The last two years of the study (2010-2011), Endothall spot treatments were applied to infested areas of the lake. This project will allow the MCWD to demonstrate whether the herbicide application is a viable long-term solution to control claspingleaf pondweed.

 

Hints to identify: Has small "teeth" visible along edge of leaf; begins growing in early spring before most other pondweeds; dies back during midsummer; the flower stalks, when present, stick up above the water surface in June; appears reddish-brown in the water, but is actually green when pulled out of the water and examined closely. Easily confused with claspingleaf pondweed, which has leaves with no "teeth" around their edges.

Management strategy: See DNR regulations. Like Eurasian watermilfoil, curlyleaf pondweed is not native to the United States and often causes problems due to excessive growth. When control is necessary, herbicides and harvesting can be effective. Grants are available for control efforts on a lake-wide basis.

 Importance of plant: Provides some cover for fish; several waterfowl species feed on the seeds; diving ducks often eat the winter buds.

 

">curly-leaf pondweed and improve the water quality of the lake. The project data will also be used to study the impacts of herbicide application on other native vegetation and fish in the lake.

Management strategy: See DNR regulations. Curly-leaf pondweed is a nonnative plant that often causes problems due to excessive growth contributing high inputs of phosphorus to a waterbody and impediment of recreational activities. When control is necessary, herbicides and harvesting can be effective. Grants are available for control efforts on a lake-wide basis.

Budget

The five-year Gleason Lake vegetation study is estimated to cost $161,600.

Design

Treatment of the entire lake was proposed for 2007, 2008, and 2009 followed by spot treatment during 2010 and 2011. Pre and post-herbicide treatment vegetation surveys conducted to collect stem density and biomass data are used to demonstrate the effectiveness of the herbicide treatment. In 2007 and 2012 pre and post treatment data on the invertebrate (aquatic insect) and fish community will be collected and an Index of Biotic Integrity (IBI) will be conducted in Gleason Lake. Water quality monitoring data are collected by the MCWD to demonstrate the changes in water quality after the long-term treatment of curly-leaf pondweed.

Narrative

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 months, as well as ice fishing and ice skating during winter.

The watershed area of Gleason Lake is almost entirely (95%) in the city of Plymouth. The rest 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. GLIA has been treating the lake on a regular basis to control and manage the Eurasian water milfoil. Gleason Lake has good water clarity; however, high concentrations of phosphorus in late summer result in blue-green algae blooms. Curly-leaf pondweed dominates in early summer followed by coontail in the later part of the summer.

The water quality in Gleason Lake has been consistently scored in the C-D grade range. 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. The long-term goal for Gleason Lake is to achieve the District's interim goal or the state's standard for water quality. Phosphorus reductions are necessary to achieve these goals.

Curly-leaf pondweed is an exotic species that competes with other native plants and is suspected by most limnologists 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 MCWD has taken several steps and funded projects in the Gleason Lake watershed to reduce the amount of nutrients that flow into the lake. GLIA has completed several other projects on its own, as well as in partnership with the city of Plymouth and the MCWD, to reduce external nutrient loads and improve the water quality in Gleason Lake. This study also aims to improve water quality in Gleason Lake by reducing the population of curly-leaf pondweed. 

Summary

The first four years of treatment has been successful in controlling and reducing the curly-leaf pondweed stem density in the Gleason Lake.  Prior to 2007 treatment, the average curly-leaf pondweed density was 817 stems/m².  The 2007 post treatment stem density was 0 stems/m².  Prior to 2008 treatment, the average curly-leaf pondweed stem density was 411 stems/m² and the 2008 post treatment stem density was 0 stems/m².  Prior to 2009 treatment, the average curly-leaf pondweed stem density was 329 stems/m² and the 2009 post treatment stem density was 0 stem/m².  

Spot treatments were done on Gleason Lake in 2010 and 2011.  Prior to 2010 treatment the average curly-leaf pondweed stem density was 73 stems/m².  The area of acreage treated in 2010 was 27.9 acres. The 2010 post treatment stem density was 0 stems/m². Prior to 2011 treatment, the average curly-leaf pondweed stem density was 21 stems/m² and the area of acreage treated was 16.3 acres. The 2011 post treatment stem density was 0 stems/m². A post treatment survey of invertebrate and fish community sampling will take place in spring of 2012.   

The water quality lake grade has shown a slight improvement over course of the project. The water quality lake grade for Gleason Lake in 2007 was D+ and improved to a C in 2010. An analysis of the water quality data of Gleason Lake from 2007 to 2011 will determine if there has been an overall improvement of the water quality during the five year project and will be included in the final report late 2012.