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.
The five-year Gleason Lake
vegetation study is estimated to cost $161,600.
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
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
(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
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.
Curly-leaf pondweed density before treatment (stems/m2)
Curly-leaf pondweed density after treatment (stems/m2)
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 acresand 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).