Report For: Dudley Pond Association Wayland, Massachusetts
Dudley Pond Targeted Aquatic Macrophyte Survey - 2021
Prepared by: Aquatic Restoration Consulting, LLC 18 Sunset Drive Ashburnham, MA 01430 November 2021
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Table of Contents Introduction ................................................................................................................................ 2 Methods ..................................................................................................................................... 2 Results ....................................................................................................................................... 4 Discussion ................................................................................................................................. 9
Tables Table 1. Dudley Pond Macrophyte Survey Data (October 2, 2021). ........................................... 5 Table 2. Cover and Biovolume Difference 2021 vs 2020. ........................................................... 6 Table 3. EWM and Tapegrass Density 2020 vs. 2021. ............................................................... 7
Figures Figure 1. Dudley Pond Aquatic Plant Observation Points ........................................................... 3 Figure 2. Dudley Pond Tapegrass & EWM Density (October. 2, 2021) ...................................... 8
Appendix - Photographs
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Introduction Aquatic Restoration Consulting, LLC (ARC) performed a limited in-lake aquatic macrophyte survey of Dudley Pond on October 2, 2021. The intent of the survey was to document the aquatic plant community and relative abundance of plants, specifically focusing on density of tapegrass (Vallisneria americana) and visual observations of harvesting efforts. The nuisance invasive species Eurasian watermilfoil (Myriophyllum spicatum) presence/absence was a secondary focus as reports from lake users indicated that this species was more prevalent than last year (2020). The Dudley Pond Association (Association) reports that tapegrass has become a nuisance and its abundance has greatly increased since first observed in 2010. The Association and the Town of Wayland have employed several management strategies to control rooted aquatic plant growth dating back to 1968. A combination of hand-pulling and herbicides are used to control Eurasian watermilfoil (EWM) with some success. SOLitude Lake Management treated the pond in August 2019 using ProcellaCOR, a selective systemic herbicide efficacious on Eurasian watermilfoil (EWM). The 2020 Aquatic Macrophyte Survey showed fewer areas containing EWM than in past years, but local pond users reported an increase in 2021. In 2021, the Association conducted mechanical harvesting in select areas of the lake and experimented with varying depths of cutting to assess efficacy of noxious tapegrass removal. Tapegrass can grow up to six feet under ample light and sediment conditions. The long ribbonlike leaves extending from a rosette and the female reproductive structure, a long flower stalk (peduncle), often binds up boat motors and entangle swimmers. The peduncle can reach the surface in water depths greater than six feet. The plant is prolific and can spread rapidly. It reproduces by seeds and runners (rhizomes) and can form winter buds (turions) allowing the plant to overwinter more successfully than other native plants. These multiple forms of reproduction and climate resiliency make controlling plant growth exceedingly difficult. This report provides a summary of findings of the limited macrophyte survey, compares 2021 survey data with 2020 and provides visual documentation of mechanical harvesting.
Methods ARC conducted a limited plant survey on October 2, 2021. ARC scientists observed and recorded submerged aquatic plants data using the same methodology in the 2020 Aquatic Macrophyte Survey. Underwater video documentation was conducted using Aqua-Vu® underwater camera and separate video recording equipment (AverMedia Live Gamer Portable 2). Only a portion of the 104 observation locations established in 2020 were reassessed. The 33 observation locations revisited in 2021 were selected in the field based on conversations at the boat launch with Association members. Areas of mechanical harvesting were described to ARC scientists prior to the survey and received the greatest level of effort during the survey. Figure 1 provides both the 104 observation points used in 2020 and the 33 points revisited in 2021.
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2020 Survey Observation Locations
2021 Survey Observation Locations
Figure 1. Dudley Pond Aquatic Plant Observation Points
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At each point, ARC scientists: • estimated percent cover of all plants as measured by the areal extent of plants within an approximate two square meter visual area. • estimated percent biovolume as measured by the height of the water column occupied by plants within the two square meter area. Cover and biovolume are estimated using a semiquantitative (0-4) ranking system as follows: Rank 0 1 2 3 4 • • •
Percent Cover or Biovolume 0% 1-25% 26-50% 51-75% 76-100%
identified plants to the species level or to genus level for those that were not readily identifiable in the field. estimated the density of all species present using categories of: Trace, Sparse, Moderate and Dense. used a rake toss to verify the visual identification of plants and density observed with the Aqua-Vu®.
ARC utilized QGIS software to produce maps depicting tapegrass and EWM densities. Note: there are inherent error/precision limitations associated with biological surveys and data are an estimation of conditions at the time of the survey.
Results Table 1 provides a listing of data collected at each observation point. Plant cover was greater than 50% (cover ranks 3 & 4) at the 33 observation points. Biovolume, a representation of the portion of the water column occupied by plants, was high with 39% of the observation locations exhibiting more than half of the water depth occupied by plants. Most of the observation points had plants occupying 26-50% of the water column (rank 2). Six percent of the observation locations had plants topping out at the surface. In comparison to the 2020 survey, plant biovolume was less; 39% (13 of 33 locations) of the 2021 observation locations showed a bio-volume decrease over 2020 (Table 2). This is likely the result of harvesting activities lessening the extent of plant growth reaching the surface. Plant species richness (number of species encountered) contained three different species. Filamentous green algae, slender naiad (Najas flexilis), and tapegrass were the most commonly encounters species. Filamentous green algae and EWM were more frequently encountered this year than during the September 2020 survey. When present, tapegrass was typically dense (79% of locations Figure 2). Slender naiad and tapegrass were commonly encountered together. Filamentous green algae were also widely distributed and present at 82% of the observation locations. EWM was encountered at seven locations (Figure 2). Specific changes in EWM and tapegrass density is shown in Table 3.
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Table 1. Dudley Pond Macrophyte Survey Data (October 2, 2021). BioBenthic Mat Cha Eleo FG Cover volume S 1 4 1 4 4 2 39 4 2 M 40 4 2 D 45 4 2 M 46 4 3 D D 54 4 3 D 57 4 3 61 4 3 65 4 1 D 66 3 1 D 67 3 2 S 69 4 3 D 73 4 2 M 74 4 4 75 4 3 D 77 4 3 D 78 4 2 D 82 4 3 M 83 4 3 M 85 4 4 S 86 4 3 88 4 3 S 89 4 1 D S 90 4 2 D 95 4 2 T 96 4 2 M 97 4 2 S D 98 4 2 S D 99 4 2 T M 100 4 2 M 101 4 2 S 104 4 2 D D Frequency of Occurrence 0 6 1 27 Frequency of Occurrence (%)1 0% 18% 3% 82% Density When Present (%) Dense 0% 33% 0% 48% Moderate 0% 0% 0% 30% Sparse 0% 33% 0% 22% Trace 0% 33% 0% 0%
Point
Lm
Mh
Ms
T T
T T
Nf D D D D S S D S S D S S D D M D D S M S S D D D
T T
No
Nv
Pc
0% 0% 0% 0%
0 0%
Usp T
M
S
D D M
T M
T M
M
T T
S T 7 27 9 1 21% 82% 27% 3%
0% 0% 52% 22% 0% 0% 7% 44% 0% 14% 41% 0% 0% 86% 0% 33%
S
T S M D D T
D S S 0 0%
Pp
0 0%
0% 0% 0% 0%
T
Va S D D D D D D D D D D M
D D D D M D D
S D S D S D S D T D D M 4 11 28 12% 33% 85%
Species Richness 3 3 4 4 4 3 3 2 4 2 3 4 5 4 2 4 4 3 3 4 6 4 4 2 4 3 3 6 6 4 3 3 5
0% 0% 18% 79% 0% 25% 9% 11% 0% 50% 36% 7% 0% 25% 36% 4%
1 – Percent Frequency of Occurrence is the number of times the species was present when plants were observed (# time species observed/33 total observations with plants).
Plant species identification key Cha - Chara (stonewort; macroalga)
Nf - Najas flexilis (slender naiad; nodding waternymph)
Eleo - Eleocharis sp . (spikerush)
No - Nymphaea odorata (yellow pond-lily)
FG - Filamentous green algae
Nv - Nuphar variegata (white pond-lily)
Lm - Lemna minor (common duckweed)
Pc - Potamogeton crispus (curly leaf pondweed)
Ms - Myriophyllum spicatum (Eurasian watermilfoil)
Pp - Potamogeton perfoliatus (clasping leaf pondweed)
Mh - Myriophyllum humile (low watermilfoil)
Usp - Utricularia species (bladderwort) Va - Vallisneria americana (tapegrass)
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Table 2. Cover and Biovolume Difference 2021 vs 2020.
Point 1 4 39 40 45 46 54 57 61 65 66 67 69 73 74 75 77 78 82 83 85 86 88 89 90 95 96 97 98 99 100 101 104
2020 2021-2020 2021 BioBioCover Bio-volume Cover volume Cover volume Difference Difference 4 1 4 4 0 -3 4 2 3 2 1 0 4 2 4 2 0 0 4 2 4 2 0 0 4 2 4 2 0 0 4 3 4 3 0 0 4 3 4 3 0 0 4 3 4 4 0 -1 4 3 3 2 1 1 4 1 4 2 0 -1 3 1 4 3 -1 -2 3 2 4 4 -1 -2 4 3 4 2 0 1 4 2 4 3 0 -1 4 4 3 2 1 2 4 3 4 3 0 0 4 3 4 3 0 0 4 2 4 2 0 0 4 3 4 4 0 -1 4 3 4 4 0 -1 4 4 4 4 0 0 4 3 4 4 0 -1 4 3 1 1 3 2 4 1 3 1 1 0 4 2 3 2 1 0 4 2 4 2 0 0 4 2 4 4 0 -2 4 2 4 4 0 -2 4 2 4 4 0 -2 4 2 4 2 0 0 4 2 4 4 0 -2 4 2 4 2 0 0 4 2 4 2 0 0 Increase 6 4 2 13 Decrease
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Table 3. EWM and Tapegrass Density 2020 vs. 2021.
Point 1 4 39 40 45 46 54 57 61 65 66 67 69 73 74 75 77 78 82 83 85 86 88 89 90 95 96 97 98 99 100 101 104
2020 Eurasian Milfoil 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 T 0 0 0 0 S T 0 0 0 0
2021 Eurasian Milfoil 0 0 T T 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 T 0 T 0 0 0 0 T T 0 0 0 S Increase Decrease
2020
2021
Difference Tapegrass Tapegrass Difference D no change S Decrease no change D D no change Increase D D no change Increase D D no change no change D D no change no change D 0 Decrease no change D D no change no change D D no change no change D D no change no change 0 0 no change no change D D no change no change D D no change no change M D Increase no change S M Increase no change 0 0 no change no change 0 0 no change no change D D no change no change M D Increase no change D D no change no change D D no change Increase D M Decrease no change D D no change no change T D Increase no change 0 0 no change no change M S Decrease no change M D Increase no change D D no change Increase D D no change no change D D no change no change 0 T Increase no change D D no change no change D D no change Increase 0 M Increase 5 7 0 4
Not present (0), Trace (T), Sparse (S), Moderate (M) and Dense (D).
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Figure 2. Dudley Pond Tapegrass & EWM Density (October. 2, 2021)
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Discussion As mentioned in the prior report, Dudley Pond has ample light and desirable sediment to support rooted plant growth and therefore something will grow. The pond will not sustain a plant-free littoral zone without dredging (and even that is limited) or excessive chemical application. The best achievable goal is to strike a balance of valuable aquatic habitat and human use by selecting a desirable native plant that will cover the pond bottom but that does not have a growth morphometry that allows the plant to reach the water surface impairing boating and swimming uses. Herbicides have become more selective over the years for control of non-native species, but none are known to effectively control tapegrass. Tapegrass is a resilient plant that has multiple mechanisms for reproduction and expansion. Generally, tapegrass is considered a desirable species and is not often a target plant for management. For these reasons there is not a lot of information on plant control remedies and very few tested solutions other than winter water level drawdown (not applicable for Dudley Pond), mechanical removal and herbicides, which have shown only fair results. The mechanical harvesting pilot program implemented in 2021 was successful in reducing tapegrass density based on the observation data and photographic documentation (Appendix – Photographs). Tapegrass can be difficult to harvest because of its ribbon like morphometry with leaf blades moving easily along with water movement. Blades can be swept away from the harvester teeth leaving spots of tall growth within a recently harvested area (see photo in Appendix). It also grows rapidly in ideal warm sunny conditions. Multiple passes with the harvester and multiple harvesting events per growing season are required to limit plant growth topping out at the surface. While mechanical harvesting will not reduce the overall plant coverage in the pond, continual harvesting will reduce the plant biomass lessening entanglement with swimmers and boating. EWM is found within the beds of tapegrass (see photo in Appendix). Unlike tapegrass, EWM can spread from fragments. Small fragments of EWM can sprout and root in the sediment upon settling. As mentioned in the 2020 evaluation, mechanical harvesting can exacerbate EWM density and a carefully planned plant management program is needed in order to avoid trading the tapegrass nuisance for a more severe EWM condition. The herbicide applicator will need to assess conditions (distribution and density of EWN in relation to tapegrass) early in the growing season and devise a treatment plan appropriate to decrease EWM density significantly prior to mechanical harvesting to avoid spreading EWM fragments. The herbicide applicator will need to carefully select an herbicide that will provide sufficient contact time with EWM as tapegrass blades may prevent the herbicide from making good contact with EWM. As with any aquatic plant management program, it is important to ensure that all appropriate permits are in place, nontarget impacts are minimized, and the contractor adheres to label restrictions and any permit special conditions.
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Appendix – Photographs
Dudley Pond Aquatic Macrophyte Survey 2021
Appendix - Photographs
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Photo 1. Tapegrass with cut tips.
Photo 2. Tapegrass with cut and uncut tips.
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Uncut or older cut in tapegrass
Deep cut in tapegrass
Photo 2. Deep cut of tapegrass.
Seed pod
Photo 3. Tapegrass peduncle (reproductive structure) with seed pod.
Dudley Pond Aquatic Macrophyte Survey 2021
Appendix - Photographs
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EWM in close association with tapegrass; high potential to be cut and spread during mechanical harvesting
Photo 4. Tapegrass with EWM.
Photo 5. Harvesting boundary
Dudley Pond Aquatic Macrophyte Survey 2021
Appendix - Photographs
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Photo 6. Bed of Chara
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Appendix - Photographs
