Curlyleaf Pondweed and Eurasian ... - Comfort Lake

View of Eurasian Watermilfoil in Comfort Lake on June 17, 2020

Curlyleaf Pondweed and Eurasian WatermilfoilDelineation and Assessment Surveys for

Comfort Lake, Chisago County, 2020

Delineation Treatment Assessment

CLP April 29, 2020 No treatment June 17, 2020

EWM June 17, 2020 Treatments by Lake Association September 4, 2020

Prepared for:Comfort Lake/ForestLake Watershed DistrictForest Lake, Minnesota

Prepared by:Steve McComas

Blue Water ScienceSt. Paul, MN 55116

December 2020

Curlyleaf Pondweed and Eurasian WatermilfoilDelineation and Assessment Surveys

For Comfort Lake, Chisago County, 2020

Summary

Curlyleaf Pondweed Delineation and Assessment Surveys: Curlyleaf pondweed delineation fordistribution and abundance was conducted on April 29, 2020. A follow-up curlyleaf assessment wasconducted on June 17, 2020.

In the delineation survey, curlyleaf was found in Comfort Lake at a single site (Figure S1) and a fewnative plants were sampled as well. Curlyleaf pondweed was not treated in 2020.

About a month later, in the June curlyleaf assessment, curlyleaf was found at 2 sites and growth wasmostly light (Figure S1). Curlyleaf was scarce in Comfort Lake in 2020.

Figure S1. [left] DELINEATION: Map of curlyleaf pondweed distribution from the April 29, 2020 survey. Black dots =sample locations and green dot = light growth. Curlyleaf pondweed was observed at 1 site on April 29, 2020. TREATMENT: No curlyleaf pondweed treatment occurred in 2020. [right] ASSESSMENT: Map of curlyleaf pondweed assessment sites for June 17, 2020. Black dots = no curlyleaf,green circles = light growth, and yellow circles = moderate growth.

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Eurasian Watermilfoil Delineation, Treatment, and Assessment Surveys: Eurasian watermilfoil(EWM) was first observed in Comfort Lake in 2014. An EWM delineation for distribution andabundance was conducted on April 29, 2020 and a mix of dead EWM combined with light growth ofnew EWM was observed. Another survey was conducted about a month later on June 17, 2020 andEWM was found at 58 sites. No herbicide treatment was sponsored by the CLFLWD in 2020 althoughEWM treatments in the nearshore areas were conducted by the Comfort Lake Association.

An EWM assessment on July 15, 2020 found EWM growth had been reduced and was growing at lightto moderate densities with a few sites of heavy EWM growth (Figure S2).

Figure S2. [top-left] DELINEATION: Map of EWM distribution from the April 29, 2020 survey. [top-middle] TREATMENT: Map of treatment areas. [top-right] DELINEATION: Map of EWM distribution from the June17, 2020 survey. [top-right] TREATMENT: Map of treatment areas. [bottom-left] TREATMENT: Map of treatment areas.[bottom-right] ASSESSMENT: Map of EWM sites for September 4, 2020. Key: black dot = no EWM, green dot = lightgrowth, yellow dot = moderate growth, and red dot = heavy growth.

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Curlyleaf Pondweed and Eurasian Watermilfoil Treatments from 2014 Through 2020: A summaryof CLP and EWM treatments from 2014-2020 is shown in Figure S3. Curlyleaf was only treated at 1acre in 2015. Curlyleaf has been sparse in Comfort Lake. EWM was first observed in 2014 and it hasspread around the lake in the last few years. A total of 7.5 acres was treated in 2016 and 3.2 acreswere treated in 2017. Spot herbicide treatments were conducted in 2018, 2019, and 2020 in nearshoreareas by the Comfort Lake Association.

Figure S3. CLFLWD Sponsored Treatments with blue bars and Comfort Lake Association sponsored treatments withred bars: [top] Curlyleaf pondweed treated in 2014-2020. [bottom] Eurasian watermilfoil treated in 2014-2020 (2018 isestimated based on individual permits and 2019 and 2020 treatment were by the CLP).

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Milfoil Hotspots and Growth Potential in Comfort Lake: Areas of moderate and heavy growth ofEWM for 2015 through 2019 are shown on the hotspot map in Figure S4. In the last couple of yearsEWM has nearly ringed the lake with growth (Figure S4). However lake sediment nitrogenconcentrations collected in 2014 found mostly low nitrogen, except for 1 location near the ComfortLake inlet (Figure S4). High nitrogen is correlated with heavy milfoil growth. EWM is still in a heavygrowth mode that is typical of new invasive species. EWM growth will likely be reduced in the future butis difficult to pin down a year.

Figure S4. [left] EWM growth distribution and density for 2015-2019.[right] EWM potential growth based on lake sediment analyses forComfort Lake.Key: green = light growth, yellow = moderate growth, and red = heavygrowth.

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Curlyleaf Pondweed and Eurasian WatermilfoilDelineation and Assessment Surveys for

Comfort Lake, Chisago County, 2020

Introduction and Methods

Comfort Lake has an area of 218 acres with a littoral area of 90 acres (MnDNR). The maximumdepth of Comfort Lake is 37 feet. The objectives of the curlyleaf surveys were to delineate theacreage of curlyleaf pondweed to treat and then treat is necessary and then after treatment, assessthe effectiveness of the treatment. The objectives of the Eurasian watermilfoil (EWM) surveyswere to delineate the acreage of EWM to treat and then treat is necessary and then aftertreatment, assess the effectiveness of the treatment.

Curlyleaf Pondweed Delineation and Assessment Methods: An initial curlyleaf pondweeddelineation was conducted on April 29, 2020. The entire perimeter of the lake was checked forcurlyleaf pondweed. A total of 141 sites were sampled for aquatic plants. A follow-up curlyleafpondweed assessment was conducted on June 17, 2020 to characterize the status of curlyleafpondweed at it’s peak growing period. The same methodology that was used for the delineationwas used for the assessment. A total of 107 sites were sampled for aquatic plants.

Eurasian Watermilfoil Delineation and Assessment Methods: An initial EWM was conductedon April 29, 2020. The entire perimeter of the lake was checked for EWM. A total of 141 sites

were sampled for aquatic plants.Another delineation was conductedon June 17, 2020 and 107 sites weresampled. A follow-up EWMassessment was conducted onSeptember 4, 2020 to characterizethe status of EWM after a treatment.The same methodology that wasused for the delineation was usedfor the assessment. A total of 107sites were sampled for aquaticplants.

Figure 1. Contour map of ComfortLake (source: MnDNR).

Comfort Lake, 2020 1

Results of the April 29, 2020 Delineation

A curlyleaf delineation was conducted using rake sampling on April 29, 2020 and 141 sites wereexamined. At this time of the year curlyleaf was found at 1 site in Comfort Lake (Table 1 andFigure 2).

On the same date, an EWM was conducted using rake sampling on April 29, 2020 and 141 siteswere examined. EWM was found at 18 sites in Comfort Lake (Table 1 and Figure 2).

Curlyleaf Pondweed and EWM Conditions in Comfort Lake, April 29, 2020

Figure 2. Map of curlyleaf delineation (left) and EWM delineation (right) in Comfort Lake on April 29, 2020.


Table 1. Aquatic plant occurrences and densities based on rake sampling for A pril 29, 2020. Densities arebased on a scale of 1 to 3 with ‘1' being light and ‘3' representing heavy growth.

Site Depth(ft)

CLP-stems

Lilies Cab-bage

Coon-tail

EWM Natives Noplants

368 1

371 3

372 5

376 6

377 5

378 7 1

379 9 1

381 4 1 1 1

385 5 1

386 5 1

387 11 1

389 5 1

390 4 1

392 9 1

394 4 1

395 5 1

396 7 1

397 6 1

398 4

399 4 1

400 8 1

401 9 1

402 6 1

403 4

405 3 1

406 10 1

407 7 1

408 3 1 1

409 3 1

413 4 1

414 10 1

415 9 1

416 4 1

417 4 1

418 5 1

419 10 1

420 5 1

421 4 1

422 5 1

423 9 1

425 10 1

426 3 2

427 7

428 5 1

429 3 1

430 8 1

431 4 1

432 4 1

433 8 1

434 3 1

435 11 1

437 3

438 5 1 1

439 4 1

440 10 1

441 6 1

443 10 1

444 4 1

448 3 1 1

450 7 1

451 3 1

452 10 1

454 6 1

455 10 1

Site Depth(ft)

CLP-stems

Lilies Cab-bage

Coon-tail

EWM Natives Noplants

457 3 1 1

462 12

471 6 1

474 3 1 1

477 4 1 1

483 4 1

489 4 1 1

496 12 1

498 4 1

501 3 1

502 7 1

503 3 1

504 8 1

507 5 1

508 5 1

Average 1 1 1 1 1 1

Occur (141sites)

1 2 2 12 18 10 34


Curlyleaf Pondweed and Eurasian Watermilfoil Surveys onJune 17, 2020

A total of 107 sites were assessed with rake sampling on June 17, 2020. Curlyleaf was found at 2sample sites out of the 107 that were monitored (Table 2). Curlyleaf growth was found to be lightat all sites (Figure 3 and Table 2). EWM was found at 58 sample sites out of the 107 sites (Table2). EWM growth was light to heavy.

Figure 3. Map of curlyleaf distribution (left) and EWM distribution (right) in Comfort Lake on June 17,2020. Key: black dot = no growth, green circles = light growth, yellow = moderate growth, and red dots =heavy growth.


Table 2. Aquatic plant stem densities based on rake sampling for June 17, 2020. Densities are based on ascale from 1 to 3 with 3 being the densest.

Waypoint Depth (ft) Spatterdock White lilies Cabbage Coontail CLP EWM No plants

83 10 1

84 5 2

85 5 3

86 4 3

87 4 3

88 4 2

89 4 2

90 4 3

91 4 3

92 5 2

93 6 1

94 9 1

95 10 1

96 4 2

97 3 3

98 3 3

99 3 2 2

100 5 2

101 8 1

102 11 1

103 8 1

104 9 1

105 7 1

106 6 1

107 7 1

108 7 1

109 6 1

110 5 2 2

111 4 1 1

112 6 1

113 7 2

114 4 2 2

115 12 1

116 17 1

117 9 1

118 6 2

119 3 2 2

120 3 2 2

121 5 2 1

122 6 1

123 3 3 1

124 4 3

125 4 2

126 4 2

127 4 2 1

128 10 1

129 3 1 1 1

130 3 1 3

131 4 3

132 4 3 2

133 4 1 3

134 4 3

135 4 2 1

136 4 2

137 5 1

138 3 2

139 6 1

140 4 2 3


Table 2. Aquatic plant stem densities based on rake sampling for June 17, 2020. Densities are based on ascale from 1 to 3 with 3 being the densest.

Waypoint Depth (ft) Spatterdock White lilies Cabbage Coontail CLP EWM No plants

141 3 3

142 3 1

143 4 2

144

145 6 1

146 10 1

147 7 1

148 6 1

149 5 1

150 10 1

151 4 1

152 4 2

153 4 3

154 4 3

155 3 3

156 3 3

157 4 3 1

158 4 3

159 4 2

160 6 1

161 9 1

162 3 1

163 4 1

164 3 1

165 4 1 1

166 3 1

167 4 3

168 4 3

169 4 2

170 5 1

171 3 2 2

172 3 2 2

173 4 2 3

174 4 2 2

175 4 3

176 4 3

177 4 3

178 4 3

179 3 1

180 3 2 1

181 4 1

182 4 3

183 4 1

184 4 2

185 4 3

186 4 3

187 5 2

188 10 1

189 5 1

Average 2 2 1 2 2 2

Occur (107 sites) 27 7 2 8 2 58 25


EWM Assessment Survey on September 4, 2020

The summer was somewhat unusual. Warm temperatures arrived early and by June 17, 2020there was significant EWM growth although it was in water depths of 4 feet or less (Figure 4).By September 4, 2020 the EWM was still present but at mostly light growth. A map of a EWMmeander surveys for both dates are shown in Figure 4. Spot treatments conducted by the ComfortLake Association combined with some natural dieback may have influenced the EWMabundance.

Figure 4. [left] Map of EWM distribution in Comfort Lake on June 17, 2020. [right] Map of EWM assessment in Comfort Lake on September 4, 2020.Key: black dot = no growth, green circles = light growth, yellow = moderate growth, and red dots = heavygrowth.


APPENDIX - CLP and EWM Delineation or AssessmentsCurlyleaf Pondweed 2014-19 Eurasian Watermilfoil 2014-19

Curlyleaf pondweed and Eurasian watermilfoil maps for 2014 through 2019

Curlyleaf Pondweed 2014-19 Eurasian Watermilfoil 2014-19

Curlyleaf pondweed and Eurasian watermilfoil maps for 2014 through 2019.

Potential for Curlyleaf Pondweed and Eurasian WatermilfoilGrowth Based on Lake Sediment Characteristics

Lake sediment sampling has been used to predict lake bottom areas that have the potential to supportheavy curlyleaf pondweed plant growth. Based on the key sediment parameters of pH, sediment bulkdensity, organic matter, and the Fe:Mn ratio (McComas, unpublished), the predicted growthcharacteristics of curlyleaf pondweed in Comfort Lake are shown below.

Lake sediment sampling also has been used to predict lake areas that have the potential to supportvarious types of EWM growth. Based on the key sediment parameters of NH4 and organic matter(McComas, unpublished), a map was prepared that predict the type of growth that could be expected inthe future in Comfort Lake.

Predicted Curlyleaf Growth Actual CLP Growth - June 6, 2019

Predicted Eurasian watermilfoil Growth Actual EWM Growth - June 6, 2019

[top] Curlyleaf pondweed predicted (left) and actual (right) growth maps.[bottom] Eurasian watermilfoil predicted (left) and actual (right) growth maps.

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Curlyleaf Pondweed and Eurasian ... - Comfort Lake