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), Gleason Lake was treated with Endothall (an aquatic herbicide that is safe to humans). The last two years of the study (2010-2011), Endothall spot treatments were applied only 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 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.

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, 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. 

Summary

The five years of treatment have been successful in controlling and reducing the curly-leaf pondweed stem density in the Gleason Lake.  

Full lake treatments were done in 2007, 2008 and 2009 with spot treatments on Gleason Lake in 2010 and 2011.  The area of acreage treated in 2010 was 27.9 acres and the area of acreage treated in 2011 was 16.3 acres.  Additional surveys for vegetation took place in April and July of 2012, and an invertebrate community survey took place in July 2012. 

The water quality lake grade has shown a slight improvement over course of the project. The water quality lake grade for Gleason Lake has improved from a D+ in 2007 and 2008, increasing to a C- in 2009, and holding steady with a C in 2010 and 2011.  These grades reflect an improvement in water clarity, and a reduction in phosphorus and chlorophyll-(a).