COON LAKE AUGUST 2008
AQUATIC VEGETATION SURVEY
Field survey conducted by Kelly LaFortune
in accordance with policies and procedures of the MN DNR
Survey Summaries and Notes
Survey Dates: 8/10-12/2008
(On cover page, floating-leaved vegetation in Coon Lake)
Summaries
Coon Lake is located in Anoka County, Minnesota. Aquatic vegetation surveys were undertaken in June and August of
2008 at the request of the Coon Lake Improvement Association (CLIA). The purpose of these surveys was to assess the
health and diversity of the aquatic plant communities in the basins, with special emphasis regarding the population of nonnative Eurasian watermilfoil present.
The August 2008 survey took place over three days. The report that follows is a summary of these survey findings.
Coon Lake
A total of 23 species were found in Coon Lake during the August 2008
survey, compared with 13 species identified in June. Of these species,
3 were floating-leaved, 3 were emergent and the remaining 17 species
were considered submergent vegetation. Two species identified during
this survey were non-native, Eurasian watermilfoil (Myriophyllum
spicatum) and Curly-leaf pondweed (Potamogeton crispus).
Native submergent species were found in 85% of stations sampled. No
vegetation was found in Coon Lake in depths greater than 12.0 feet.
The average number of submerged native species at each sample point
was 3.5 +/- 1.
Natural shoreline on Coon Lake
Lake Information
DOW Lake ID: 02004200
Survey Dates: 8/10-12/08
General Lake Information
Basin Area (acres): 1,259 (1,098 littoral)
Public Accesses: 3
DOW Maximum Lake Depth: 27.00
DOW Secchi Depth: 7.75
Lake Survey Conditions
Survey Crew: Kelly LaFortune and Tom Straka
Dates: 8/10-12/2008
Air Temp-average (F): 78°
Water Temps (F): 75-77°
Sky Conditions: clear, variable light winds <10 mph (East)
Coon Lake, Anoka County
Lake Sample Station Summary
DOW Lake ID: 02004200
Survey Dates: 8/10-12/08
Sample Station Information
Number of Sample Stations: 578 of 604 sampled
Maximum Depth (of stations sampled): 24.4 feet
Mean Depth: 6.7 feet
Minimum Depth: 2.0 foot
Map of sample depths in Coon Lake during August 2008 survey
Values reflect depths (in feet). Points with no values were on shore or otherwise not surveyable
More detailed depth information may be made available to the Coon Lake Improvement Association along with
this report. Due to size constraints, point-by-point depths cannot be added here.
Lake Sample Station Summary
DOW Lake ID: 02004200
Vegetation Summary and Analysis
Maximum Depth of Submergent Vegetation Growth: 12.0 feet
Lakewide Species Richness: 23 (includes emergent vegetation)
Percent of Vegetated Plots: 85
Ceratophyllum demersum
# of Plots
Occurring
268
Species
Frequency**
53.2%
Potamogeton zosteriformis
256
50.8%
0.022
Elodea canadensis
241
47.8%
0.022
Potamogeton robbinsii
198
39.3%
0.022
Myriophyllum spicatum
165
32.7%
0.021
Potamogeton amplifolius
147
29.2%
0.020
Najas flexilis
133
26.4%
0.020
Potamogeton illinoensis
100
19.8%
0.018
Nymphaea odorata
59
11.7%
0.014
Chara sp.
57
11.3%
0.014
Utricularia vulgaris
39
7.7%
0.012
Vallisneria americana
33
6.5%
0.011
Potamogeton strictifolius
29
5.8%
0.010
Nuphar variegatum
19
3.8%
0.008
Stuckenia pectinata
12
2.4%
0.007
Potamogeton richardsonii
8
1.6%
0.006
Potamogeton crispus
3
0.6%
0.003
Ranunculus longirostris
1
0.2%
0.002
Potamogeton praelongus
1
0.2%
0.002
Species*
Standard Error
0.022
*Species in bold are non-native to Minnesota waters
**Species frequencies were calculated based on points sampled that were less than the
maximum depth where plants were found (per Crowell 2007)
The August 2008 survey found the submergent vegetation community of Coon Lake is dominated by a native species,
Ceratophyllum demersum. This species was also abundant in the June survey, found in 40.4% of vegetated points in that
survey. Emergent vegetation species identified in the August survey included hardstem bulrush (Scirpus acutus),
common cattail (Typha sp.) and three-square bulrush (Scirpuspungens). These species were scattered around the
shorelines of the basin. A free-floating species of duckweed (Lemna trisulca) was also identified.
Several submergent species not identified in the June survey were noted in August. A majority of these species were
identified as Potamogeton sp. in the June report. Potamogeton gramineus, a species identified by DNR staff in an earlier
survey, was not found during this survey. Images and descriptions of additional species are included in the next section
of this report. Additional information on these and many other native aquatic plants can be found on the Minnesota DNR
website at www.dnr.state.mn.us.
Lake Vegetation Illustrations
DOW Lake ID: 02004200
Survey Date: 8/10-12/08
Najas flexilis-Bushy pondweed
Bushy pondweed is a submergent plant commonly found in clear waters up to 20
feet deep. These plants are annuals, and therefore must start from seed every year.
The entire plant is eaten by waterfowl, and many fish species rely on bushy
pondweed for cover. This plant may be confused with Chara , however, Chara
has a strong, musky odor when crushed.
Stuckenia pectinata-Sago pondweed
Sago pondweed is widely regarded as one of the most important
submergent aquatic plants for waterfowl. Its seeds and tubers are
sought out by diving ducks such as canvasbacks. The plant is easy
to recognize by its stiff, needle-like leaves. Oftentimes, the seeds
can be seen growing above the water surface, and the leaves spread
out in a fanlike fashion below.
Potamogeton richardsonii-Clasping-leaf pondweed
Clasping-leaf pondweed is a member of the broad-leaf pondweed group. This
plant grows in depths up to twenty feet, often near drop-offs or other lake
structure. The leaves of clasping-leaf pondweed alternate along the stem, with
the broad leaf bases clasping around the stem-hence, its name. The seedheads
grow in a spike form, often reaching above the lake surface from June to
August. Clasping-leaf pondweed is a very important plant for fish habitatbluegills often nest near it and walleyes use this plant for cover from predation.
This plant may be confused with curly-leaf pondweed, however, there are no
small teeth along the margins of the leaves in clasping-leaf pondweed.
Lake Vegetation Illustrations – cont’d
DOW Lake ID: 02004200
Survey Date: 8/10-12/08
Potamogeton robbinsii-Robbins’ pondweed
Robbins’ pondweed is a member of the narrow-leaf pondweed group. As
with all narrow-leaf pondweeds, Robbins’ is an important plant for fish
and wildlife habitat. Many species depend on this native plant for cover
and food.
© USDA
Potamogeton strictifolius-Straight-leaved pondweed
This plant may also be called narrow-leaved or stiff pondweed due to its fairly rigid
leaves. This species resembles several other linear-leaved pondweeds, so
misidentification is common. The flowers and fruits seen in the late summer into
fall are often used for correct identification. As with Robbins’ pondweed, this
species is important for fish and wildlife habitat.
© USDA
Vallisneria americana-Wild celery
Wild celery provides shade and shelter for bluegills, young perch, and
largemouth bass. Parts of this plant are also choice food of waterfowl,
particularly diving ducks. Canvasbacks have been known to seek out
areas of wild celery during their migrations.
Because wild celery is an excellent wildlife food, it is usually best left
alone. Abundant growth during July and August in shallow water may
interfere with recreation. Herbicides don't work well to control this
plant. Hand-pulling or raking sometimes works, though floating,
uprooted plants often re-establish themselves in shallow water. In Coon
Lake, this plant did not seem to reach nuisance levels.
Non-Native Vegetation Summary
Potamogeton crispus in Coon Lake
DOW Lake ID: 02004200
Survey Dates: 8/10-12/08
Curly-leaf pondweed
The abundance of curly-leaf pondweed decreased
dramatically between the vegetation surveys of 2008.
In the June survey, the exotic was found in over 66%
of the stations sampled in Coon Lake. In contrast,
the species was identified in less than 1% of the
stations sampled in August.
It is natural for curly-leaf pondweed to be absent in
the late summer, due to its interesting life cycle.
Several turions (hardened stem tips) of the plants
were found on the vegetation hook during the August
survey. These tips can be thought of as the seeds of
the curly-leaf plant, and the reason that this plant is
so persistant. The turions fall to the sediment when
the plant dies in midsummer, and stay beneath the ice
over winter. These winter buds actually enable the
plant to begin growing under the ice in the early
spring, allowing it to get a head start on other, native
vegetation. This head start means that curly-leaf has
an advantage over other plants, and can limit their
growth by outcompeting for resources such as
nutrients and light.
Sample locations where Potamogeton crispus was found on Coon Lake
June 2008 (points in yellow)
Sample locations where Potamogeton crispus was found on Coon Lake
August 2008 (denoted by red stars)
Curly-leaf pondweed turion formation in Coon Lake
Non-Native Vegetation Summary
Myriophyllum spicatum in Coon Lake
DOW Lake ID: 02004200
Survey Dates: 8/10-12/08
Eurasian watermilfoil
Sample locations* where Myriophyllum spicatum was found in Coon Lake - June 2008
Sample locations* where Myriophyllum spicatum was found in Coon Lake - August 2008
*Locations where Eurasian watermilfoil was identified are shown in yellow.
Non-Native Vegetation Summary
Myriophyllum spicatum in Coon Lake-cont’d
DOW Lake ID: 02004200
Survey Dates: 8/10-12/08
Eurasian watermilfoil
Eurasian watermilfoil increased slightly in species frequency
between the two surveys, from 30.8% in June to 32.7% in the
August survey. However, it is important to realize that some
areas of the west bay were not able to be accurately surveyed in
June, which may account for some of the increase.
The figures below identify the areas of greatest density of
Eurasian watermilfoil identified during the 2008 aquatic
vegetation surveys. These densities represent abundances of 3
and 4 according to Minnesota DNR criteria for judging
abundances during a point-intercept survey (Crowell 2007).
Areas of high EWM density in June 2008
Eurasian watermilfoil in Coon Lake during the June survey
Areas of high EWM density in August 2008
The figures above show the relative density of Eurasian watermilfoil actually decreased during the
summer of 2008.
Coon Lake Ecology and Management
DOW Lake ID: 02004200
Survey Dates: 8/10-12/08
Nutrients
Nutrients have a very complex role in aquatic ecosystems and can be influenced by a number of factors. The
major sources of nutrients such as phosphorus to most urban lakes stem from the practices of homeowners in
the watershed. Runoff from lawn clippings and excess fertilizers is a common source of phosphorus pollution
and can promote algae blooms. Large die-offs of vegetation in a basin (such as after an aquatic herbicide
treatment or the natural mid-summer die-off of curly-leaf) can also cause an increase in nutrients.
Submergent vegetation, like this native
coontail, can help keep water clear by
removing excess nutrients from the water
column and by stabilizing sediments.
Shoreland Management
Although there is little landowners can do about natural plant
die-offs, you can improve water quality by minimizing runoff.
The Minnesota DNR has several references available to
landowners interested in learning how to minimize their negative
impacts on our lakes and streams. The publication listed below
is an excellent place to start, and can be purchased through the
DNR, or your local book retailer. Contact the MNDNR
Information Center for more information.
Lakescaping for Wildlife & Water Quality, by Carrol L.
Henderson, Carolyn J. Dindorf, and Fred J. Rozumalski. St.
Paul, MN: Minnesota Department of Natural Resources, Section of Wildlife, Nongame Wildlife Program
c1998.